Anti-cd28 antibodies and methods related thereto

Abstract

The present disclosure provides CD28-binding domains, antibodies, antigen-binding antibody fragments, and multispecific antibodies, which bind to CD28. The disclosed antibodies include those with, inter alia, desirable T-cell activation and (re)directed target cell killing potency, and / or developability profiles. The present disclosure further provides nucleic acids and vectors encoding such antibodies or antibody fragments and cells comprising such nucleic acids. Further provided are pharmaceutical compositions, in vivo methods, and manufacturing methods relating to such antibodies or antigen-binding antibody fragments.

Description

ANTI-CD28 ANTIBODIES AND METHODS RELATED THERETOCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to: U.S. Provisional Application No.: 63 / 467,202, filed on May 17, 2023, entitled “ANTI-CD28 ANTIBODIES AND METHODS RELATED THERETO”; and U.S. Provisional Application No.: 63 / 607,811, filed on December 8, 2023, entitled “ ANTI-CD28 ANTIBODIES AND METHODS RELATED THERETO”. The contents of said applications are incorporated by reference in their entirety herein.REFERENCE TO AN ELECTRONIC SEQUENCE LISTING

[0002] The contents of the electronic sequence listing (1160430_004413_SL.xml; Size: 13,964.535 bytes; and Date of Creation: April 23, 2024) is herein incorporated by reference in its entirety.BACKGROUND

[0003] The activation of T cells is important for the stimulation of immune responses. T cells exhibit immunological specificity and direct most of the cellular immune responses. Although T cells do not secrete antibodies, they are required for the secretion of antibodies by B lymphocytes. T cell activation requires the participation of a number of cell surface molecules, such as the T cell receptor (TCR) complex (which is a disulfide-linked heterodimer, membrane glycoprotein with chains, alpha and beta (α and β) . or gamma and delta (γ and δ), non-covalently linked with a complex of invariant proteins, designated CD3), CD4 or CD8 molecules, and receptors of costimulatoiy molecules (e.g., CD28 as a receptor of CD80 and CD86).

[0004] Due to the role of CD28 in T cell activation, CD28 is an important therapeutic target. Based thereon, agonistic anti-CD28 antibodies have been studied and clinically tested as therapeutics for the treatment of diseases in which immune activation is desired such as cancer (e.g., theralizumab, super agonistic anti-CD28 monoclonal antibody (also known as TGN1412)). Agonistic anti-CD28 antibodies are also believed to potentially help treat autoimmune diseases and inflammatory diseases, perhaps via activation of regulatory T cells (e.g., Beyersdorf et al., Ann Rheum Dis. 2005 Nov;64 Suppl 4 (Suppl 4):iv91-5.).Antagonistic anti-CD28 antibodies have also been developed for potential use in treating autoimmune diseases and inflammatory diseases and conditions such as those associated with transplantation (e.g., Vanhove et al.. Antibodies (Basel). 2017 Dec; 6(4): 19.; Suchard et al., JImmunol. 2013 Nov 1;191(9):4599-610.). However, development of anti-CD28 antibodies have so far faced difficulties such as induction of cytokine release syndrome (CRS), and regulatory approval is yet to be achieved.

[0005] The recent development and use of multispecific antibodies, such as bispecific antibodies (bsAbs), to redirect effector T cells for the targeted killing of tumor cells has shown considerable promise both pre-clinically and clinically (see, e.g., Topp et al, 2012, Blood 120:5185-87; Bargou et al, 2008, Science 321:974-77). Many of the bispecific antibodies developed to date contain a first binding site specific to CD3 for T-cell recruitment and activation, and a second binding site for a targeted disease-associated antigen, such as CD19 (Bassan, 2012, Blood 120:5094-95). The bispecific antibody is thought to bring CD3+ T cells into direct contact with targeted disease cells and induce cell-mediated cytotoxicity (Bassan, 2012).

[0006] Numerous methods for making bispecific antibodies are known. For example, bispecific antibodies can be produced by the quadroma method, which involves the fusion of two different hybridomas, each producing a monoclonal antibody recognizing a different antigenic site (Milstein and Cuello, Nature 1983; 305:537-540). Another method for producing bispecific antibodies uses heterobifunctional cross-linkers to chemically tether two different monoclonal antibodies, so that the resulting hybrid conjugate will bind to two different targets (Staerz, et al. Nature 1985; 314:628-631; Perez, et al. Nature 1985; 316:354- 356). Bispecific antibodies can also be produced by reduction of each of two parental monoclonal antibodies to the respective half molecules, which are then mixed and allowed to reoxidize to obtain the hybrid structure (Staerz and Bevan. Proc Natl Acad Sci USA 1986; 83: 1453-1457). An alternative approach involves chemically cross-linking two or three separately purified Fab' fragments using appropriate linkers. Several bispecific antibodies targeting CD3 and CD19 are in vanous stages of development and / or have been approved as therapeutics.

[0007] scFv-based bispecific antibody constructs, known as BITE® (Bispecific T-cell Engager), which employ a single polypeptide containing 2 antigen-binding specificities, each contributed by a cognate VH and VL, linked in tandem via a flexible linker are also known (see, e.g., Nagorsen et al, 2009, Leukemia & Lymphoma 50:886-91: Amann et al, 2009, J Immunother 32:453-64; Baeuerle and Reinhardt, 2009, Cancer Res 69:4941-44). Another type of bispecific antibody called DART® (Dual- Affinity Re-Targeting) which utilizes a disulfide-stabilized diabody design is also known (see, e.g.. Moore et al.. 2011. Blood 117:4542-51: Veri et al, 2010, Arthritis Rheum 62: 1933-43). Both BITE® and DART®exhibit fast blood clearance due to their small size (~55 kDa). which requires frequent administration to maintain therapeutic levels of the bispecific antibodies.

[0008] Also, SCORPION Therapeutics (Emergent Biosolutions, Inc., Seattle, Wash.) reportedly developed a platform technology combining two antigen-binding domains in a single chain protein wherein one binding domain is on the C-terminus and a second binding domain on the N-terminus of an effector domain base on immunoglobulin Fc regions.

[0009] Tetravalent and bispecific antibody-like proteins referred to as DVD-Igs are also known which are engineered from two monoclonal antibodies (Wu, C. et al., Nature Biotechnology, 25, p 1290-1297, 2007). To construct the DVD-Ig molecule, the V domains of the two mAbs are fused in tandem by a short peptide linker (TVAAP) (SEQ ID NO: 56) with the variable domain of the first antibody light (VL) chain at the N terminus, followed by the other antibodies VL and Ck to form the DVD-Ig protein light chain and wherein the variable regions of the heavy (VH) chain of the tw o mAbs are fused in tandem by a short peptide linker (ASTKGP) (SEQ ID NO: 57) with the first antibody at the N terminus, follow ed by the other antibody and the heavy chain constant domains to form the DVD-Ig protein heavy chain (VHWL1). All light chain and heavy chain constant domains are preserved in the DVD-Ig design, and cotransfection of mammalian cells with expression vectors encoding the DVD-Ig light chain and heavy chain reportedly leads to the secretion of a single species of an IgG-like molecule with molecular weight of approximately 200 kDa comprising four binding sites. 2 from each mAb.

[0010] While many candidate clinical and therapeutic bispecific antibodies have been disclosed which are reported to display exquisite selectivity and high potency towards targets of interest, a large proportion of these antibodies have been found during downstream development and clinical efficacy studies to suffer from undesirable characteristics such as: promiscuity of binding, poly specific binding (also termed herein and throughout, “polyspecificity”), off-target binding; nonspecific binding; poor expression levels or profiles in eukaryotic host cells, such as mammalian host cells and yeast cells; poor chemical and physical properties, such as poor stability during storage (e.g., poor / low “shelf-life” stability), poor (low) solubility, poor (high) viscosity, propensity to aggregate, and the like; and poor clinical and biophysical profiles, such as poor pharmacokinetic profiles, poor pharmacodynamic profiles, fast or poor in vivo clearance rates, short circulation half-life, and the like; thereby requiring the termination of further therapeutic development of such candidate antibodies. Additionally, it has been observed that antibodies derived from display technologies represent a historical minority of all clinical and marketed antibodies, a trendwhich is believed by many to be due, at least in part, to promiscuity of binding, poor PK profiles, and poor CMC characteristics - liabilities which are further postulated to be largely due to a lack of suitable means and methods by which undevelopable antibodies may be detected and / or counter-selected against when screening for antibodies using display technologies (see, e.g., Meninger 2012; available at hyper-text transfer protocol: proteins- congress.com / wordpress / wp-content / uploads / 2012 / 01 / Trends-in-Therapeutic-Monoclonal- Antibody-Discovery-Technology.pdf).

[0011] To address such issues certain techniques and assays have been developed to assess many of the aforementioned developability characteristics for discovered antibodies in the context of downstream development activities (“post-discovery antibodies”), such as CIC, SIC, BVP-ELISA, TMA, and other assays; however, such assays are typically not amenable to their incorporation into high-throughput early polypeptide and antibody discovery platforms, such as antibody display platforms. Furthermore, assessment of these attributes ty pically requires milligram to gram quantities of protein, which limits the number of leads that can be pragmatically considered for development, and consequently reducing the likelihood of program success. Consequently, significant resources are often expended attempting to fix poorly behaving lead candidates with few backups available in later stages of development.

[0012] In recognition of this bottleneck, considerable efforts have been made to develop assays with lower material requirements and to bring developability assessments further upstream in the development process (Esfandiary et al., 2013, Protein Eng Des Sei 26 (10): 663-670, 2013; Sathish et al., 2013, Nat Rev Drug Discov. 12(4):306-24). A number of such assays are directed at predicting antibody solubility and aggregation behavior of identified, lead candidates. Self-interaction chromatography (SIC) and cross-interaction chromatography (CIC) are column based, low-to-medium throughput assays that correlate with and thus predict antibody solubility at relatively low concentration (Ahamed et al., 2005, J Biol Chem 280(37):32090-100; Jacobs et al., Pharm Res 27:65-71, 2010; Spencer et al., mAbs 4(3)319- 325, 2012). Also, Sule and co-workers reported a medium throughput gold nanoparticle assay to predict solubility at very low concentration and further broadened the assay scope to be compatible with complex cell culture media (Sule et al., Biophys J 101 (7): 1749-1757, 2011;Mol Pharmaceutics 10(4): 1322-1331, 2013).

[0013] Also, because of the problems associated with polyspecificity and its association with poor antibody pharmacokinetics (see, Wu et al., J Mol Biol 368:652-665, 2007; Hotzel et al., 2012, mAbs 4(6):753-760), polyspecificity assays have been developed. For example,Wardemann and colleagues have reported an enzyme-linked immunosorbent assay (ELISA) method using LPS. Insulin, dsDNA, and ssDNA to study polyreactivity in natural antibody repertoires over the course of B-cell maturation (Wardemann et al., 2003, Science 301(5638): 1374-7). Protein biochips in which a diverse set of proteins are spotted onto an array for high-throughput ELISAs are another ty pe of screening tool. A chip with -400 different human proteins from Protagen (Dortmund, Germany) has been reported to compare favorably with IHC staining analysis (Lueking et al., 2008, Bio Techniques 45(4):Pi-Pv), as well as a measure of off-target binding of clinically approved TNF-alpha inhibitors (Feyen et al., Anal Bioanal Chem 391:1713-1720, 2008). Further, Frese et al. reported a 384-well assay that measures polyreactivity to 32 test proteins, termed Protein Panel Profiling or 3P (Frese et al., 2013. mAbs 5:2, 279-287). Using this assay, the authors showed that FDA-approved therapeutic antibodies show a highly specific profile to the 32 test proteins and that it may be used to screen candidates from a phage selection process. Also, Hotzel et al. 2012 mAbs 4(6):753-760), developed a baculovirus particle (BVP) ELISA which reportedly predicts faster antibody non-target mediated clearance in vivo. Also, reagents, methods, and means to assess, predict, select and enrich for developable therapeutic antibodies, and ultimately to generate and obtain developable antibodies, for example from antibody libraries, have been reported (see, e.g., WO2014 / 179363).

[0014] Cell proliferative disorders, such as cancer, are characterized by the uncontrolled growth of cell subpopulations. They are the leading cause of death in the developed world and the second leading cause of death in developing countries, with over 12 million new cancer cases diagnosed and 7 million cancer deaths occurring each year. The National Cancer Institute estimates that greater than half a million Americans will die of cancer in 2013, accounting for nearly one out of every four deaths in the country. As the elderly population has grown, the incidence of cancer has concurrently risen, as the probability of developing cancer is more than two-fold higher after the age of seventy. Cancer care thus represents a significant and ever-increasing societal burden. There is, therefore a need for the provision for CD28 binding domains, and antibodies comprising them (including multispecific antibodies), which display desirable developability and / or CRS risk profiles and are safe and efficacious in, for example, binding specifically to CD28 expressed on T-cells, activating T- cells, (re)-directing the activated T-cells to kill target cells. The present disclosure addresses these needs.SUMMARY

[0015] The present disclosure relates to: anti-CD28 antibodies and antigen-binding antibody fragments, nucleic acids and vectors encoding such antibodies or antibody fragments and cells comprising such nucleic acids: and pharmaceutical compositions, in treatment methods, and manufacturing methods related thereto.

[0016] In one aspect, the present disclosure provides anti-CD28 antibodies and antigenbinding antibody fragments. An anti-CD28 antibody or antigen-binding antibody fragment according to the present disclosure may comprise: a first heavy chain variable domain (VH-1) comprising a first heavy chain complementarity determining region (CDR) 1 (CDRH1-1), a first heavy chain CDR2 (CDRH2-1), and a first heavy chain CDR3 (CDRH3-1); and / or a first light chain variable domain (VL-1) comprising a first light chain CDR1 (CDRL1-1), a first light chain CDR2 (CDRL2-1). and a first light chain CDR3 (CDRL3-1).

[0017] In some embodiments, an anti-CD28 antibody or antigen-binding antibody fragment may comprise a CDR amino acid sequence according to any one of those listed in Table 1B and / or 12B or a variant thereof having at least about 50%, 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%. 95%. 96%. 97%. 98%. or 99% sequence identity.

[0018] In some embodiments, (a) the amino acid sequence of the CDRHl-1 may comprise or consist of a heavy chain complementarity determining region 1 (CDRH1) amino acid sequence contained in any one of the heavy chain variable domain (VH) amino acid sequences listed in Table 1A and / or 12A; and / or any one of the CDRH1 amino acid sequences listed in Table 1B and / or 12B; (b) the amino acid sequence of the CDRH2-1 mat comprise or consist of: a heavy chain complementarity determining region 2 (CDRH2) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 1A and / or 12A; and / or any one of the CDRH2 amino acid sequences listed in Table 1B and / or 12B; and / or (c) the amino acid sequence of the CDRH3-1 may comprise or consist of: a heavy chain complementarity determining region 3 (CDRH3) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 1A and / or 12A; and / or any one of the CDRH3 amino acid sequences listed in Table 1B and / or 12B.

[0019] In some embodiments, (d) the amino acid sequence of the CDRLl-1 may comprise or consist of: a light chain complementarity determining region 1 (CDRL1) amino acid sequence contained in any one of the light chain variable domain (VL) amino acid sequences listed in Table 1A and / or 12A; and / or any one of the CDRL1 amino acid sequences listed in Table 1B and / or 12B; (e) the amino acid sequence of the CDRL2-1 may comprise or consist of: a light chain complementarity determining region 2 (CDRL2) contained in any one of the VL amino acid sequences listed in Table 1A and / or 12A; and / or any one of the CDRL2amino acid sequences listed in Table 1B and / or 12B; and / or (f) the amino acid sequence of the CDRL3-1 may comprise or consist of: alight chain complementarity determining region 3 (CDRL3) contained in any one of the VL amino acid sequences listed in Table 1A and / or 12A; and / or any one of the CDRL3 amino acid sequences listed in Table 1B and / or 12B.

[0020] In some embodiments, an anti-CD28 antibody or antigen-binding antibody fragment according to the present disclosure may comprise: (a) a set of heavy chain CDR amino acid sequences of a first anti-CD28 antibody selected from the antibodies having the amino acid sequences listed in Tables 1A-1D and / or 12A-12D; (b) a set of light chain CDR amino acid sequences of a first anti-CD28 antibody selected from the antibodies having the amino acid sequences listed in Tables 1A-1D and / or 12A-12D; (c) a set of heavy and light chain CDR amino acid sequences of a first anti-CD28 antibody selected from the antibodies having the amino acid sequences listed in Tables 1A-1D and / or 12A-12D; (d) a set of heavy chain CDR amino acid sequences of a first anti-CD28 antibody selected from the antibodies listed having the amino acid sequences in Tables 1A-1D and / or 12A-12D; and a set of light chain CDR amino acid sequences of a second anti-CD28 antibody selected from the antibodies having the amino acid sequences listed in Tables 1A-1D and / or 12A-12D. The first anti-CD28 antibody and the second anti-CD28 antibody may or may not be the same antibody.

[0021] In certain embodiments, the anti-CD28 antibody or antigen-binding antibody fragment may comprise (A) said VH-1 and said VL-1, wherein: (1) the amino acid sequences of the CDRH1 -1, the CDRH2-1, and the CDRH3-1 comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, and a CDRH3, respectively, contained in the VH of a first anti-CD28 antibody; and (2) the amino acid sequences of the CDRLl-1, the CDRL2-1, and the CDRL3-1 comprise or consist of the amino acid sequences of a CDRL1, a CDRL2, and a CDRL3, respectively, contained in the VL of said first anti-CD28 antibody, wherein said first anti-CD28 antibody is any one of the following anti-CD28 antibodies listed in Tables 1A-1D and / or 12A-12D: (i) Ab No. 1; (ii) Ab No. 2; (iii) Ab No. 3; (iv) Ab No. 4; (v) Ab No. 5; (vi) Ab No. 6; (vii) Ab No. 7; (viii) Ab No. 8; (ix) Ab No. 9; (x) Ab No. 10; (xi) Ab No. 11; (xii) Ab No. 12; (xiii) Ab No. 13; (xiv) Ab No. 14; (xv) Ab No. 15; (xvi) Ab No. 16; (xvii) Ab No. 17; (xviii) Ab No. 18; (xix) Ab No. 19; (xx) Ab No. 20; (xxi) Ab No. 21; (xxi-a) Ab No. 21a; (xxi-b) Ab No. 21b; (xxi-c) Ab No. 21c; (xxi-d) Ab No. 21d; (xxi-e) Ab No. 21e; (xxi-1) Ab No. 21f; (xxii) Ab No. 22; (xxiii) Ab No. 23; (xxiv) Ab No. 24; (xv) Ab No. 25; (xvi) Ab No. 26; (xvii) Ab No. 27; (xviii) Ab No. 28; (xviii-a) Ab No. 28a; (xviii-b) Ab No. 28b; (xviii-c) Ab No. 28c; (xviii-d) Ab No. 28d; (xviii-e) Ab No. 28e; (xviii-f) Ab No. 28f; (xix) Ab No.29; (xxx) Ab No. 30; (xxxi) Ab No. 31; (xxxii) Ab No. 32; (xxxiii) Ab No. 33; (xxxiv) Ab No. 34; (xxxv) Ab No. 35; (xxxvi) Ab No. 36; (xxxvii) Ab No. 37; (xxxviii) Ab No. 38; (xxxix) Ab No. 39; (xl) Ab No. 40; (xli) Ab No. 41; (xlii) Ab No. 42; (xliii) Ab No. 43; (xliv) Ab No. 44; (xlv) Ab No. 45; (xlvi) Ab No. 46; (xlvi-a) Ab No. 46a; (xlvi-b) Ab No. 46b; (xlvi-c) Ab No. 46c; (xlvi-d) Ab No. 46d; (xlvi-e) Ab No. 46e; (xlvii) Ab No. 47; (xlviii) Ab No. 48; (xlix) Ab No. 49; (1) Ab No. 50; (li) Ab No. 51; (lii) Ab No. 52; (liii) Ab No. 53; (liv) Ab No. 54; (Iv) Ab No. 55; (Ivi) Ab No. 56; (Ivii) Ab No. 57; (Ivii-a) Ab No. 57a; (Ivii-b) Ab No. 57b; (Ivii-c) Ab No. 57c; (Ivii-d) Ab No. 57d; (Ivii-e) Ab No. 57 e; (Ivii-f) Ab No. 57f; (Iviii) Ab No. 58; (lix) Ab No. 59; (lx) Ab No. 60; (Ixi) Ab No. 61; (Ixi-a) Ab No. 61a; (Ixi-b) Ab No. 61b; (Ixi-c) Ab No. 61c; (Ixi-d) Ab No. 61d; (Ixi-e) Ab No. 61e; (Ixii) Ab No. 62; (Ixiii) Ab No. 63; (Ixiv) Ab No. 64; (Ixv) Ab No. 65; (Ixvi) Ab No. 66; (Ixvii) Ab No. 67; (Ixviii) Ab No. 68; (Ixviii-a) Ab No. 68a; (Ixviii-b) Ab No. 68b; (Ixviii-c) Ab No. 68c; (Ixviii- d) Ab No. 68d; (Ixviii-e) Ab No. 68e; (Ixviii-f) Ab No. 68f; or (Ixix) Ab No. 69.

[0022] In particular embodiments of (A) above, said first anti-CD28 antibody may be anyone of; (1) Ab No. 1. (2) Ab No. 21. (3) Ab No. 28, (4) Ab No. 46, (5) Ab No. 57, (6) Ab No. 61. or (7) Ab No. 68. according to Tables 1A-1D. In particular cases, said first anti-CD28 antibody may be Ab No. 1 according to Tables 1A-1D.

[0023] In certain embodiments, the VH-1 may be sufficient for binding to CD28 or the VH-1 paired with another VL or VL-1 such as but not limited to one disclosed herein may provide binding to CD28. Therefore, in certain embodiments, the anti-CD28 antibody or antigen-binding antibody fragment may comprise (B) the VH-1 and optionally a / the VL-1 , wherein the amino acid sequences of the CDRH1-1, the CDRH2-1, and the CDRH3-1 comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, and a CDRH3, respectively, contained in the VH of any one of the following anti-CD28 antibodies listed in Tables 1A-1D and / or 12A-12D: (i) Ab No. 1; (n) Ab No. 2; (in) Ab No. 3; (iv) Ab No. 4; (v) Ab No. 5; (vi) Ab No. 6; (vii) Ab No. 7; (viii) Ab No. 8; (ix) Ab No. 9; (x) Ab No. 10; (xi) Ab No. 11; (xii) Ab No. 12; (xiii) Ab No. 13; (xiv) Ab No. 14; (xv) Ab No. 15; (xvi) Ab No. 16; (xvii) Ab No. 17; (xviii) Ab No. 18; (xix) Ab No. 19; (xx) Ab No. 20; (xxi) Ab No. 21; (xxi-a) Ab No. 21a; (xxi-b) Ab No. 21b; (xxi-c) Ab No. 21c; (xxi-d) Ab No. 21d; (xxi-e) Ab No. 21e; (xxi-f) Ab No. 21 f; (xxii) Ab No. 22; (xxiii) Ab No. 23; (xxiv) Ab No. 24; (xv) Ab No. 25; (xvi) Ab No. 26; (xvii) Ab No. 27; (xviii) Ab No. 28; (xviii-a) Ab No. 28a; (xviii- b) Ab No. 28b; (xviii-c) Ab No. 28c; (xviii-d) Ab No. 28d; (xviii-e) Ab No. 28e; (xviii-f) Ab No. 28f; (xix) Ab No. 29; (xxx) Ab No. 30; (xxxi) Ab No. 31; (xxxii) Ab No. 32; (xxxiii) Ab No. 33; (xxxiv) Ab No. 34; (xxxv) Ab No. 35; (xxxvi) Ab No. 36; (xxxvii) Ab No. 37;(xxxviii) Ab No. 38; (xxxix) Ab No. 39; (xl) Ab No. 40; (xli) Ab No. 41; (xlii) Ab No. 42; (xliii) Ab No. 43; (xliv) Ab No. 44; (xlv) Ab No. 45; (xlvi) Ab No. 46; (xlvi-a) Ab No. 46a; (xlvi-b) Ab No. 46b; (xlvi-c) Ab No. 46c; (xlvi-d) Ab No. 46d; (xlvi-e) Ab No. 46e; (xlvii) Ab No. 47; (xlviii) Ab No. 48; (xlix) Ab No. 49; (1) Ab No. 50; (li) Ab No. 51; (lii) Ab No. 52; (liii) Ab No. 53; (liv) Ab No. 54; (Iv) Ab No. 55; (Ivi) Ab No. 56; (Ivii) Ab No. 57; (Ivii- a) Ab No. 57a; (Ivii-b) Ab No. 57b; (Ivii-c) Ab No. 57c; (Ivii-d) Ab No. 57d; (Ivii-e) Ab No. 57 e; (Ivii-f) Ab No. 57f; (Iviii) Ab No. 58; (lix) Ab No. 59; (lx) Ab No. 60; (Ixi) Ab No. 61; (Ixi-a) Ab No. 61a; (Ixi-b) Ab No. 61b; (Ixi-c) Ab No. 61c; (Ixi-d) Ab No. 61d; (Ixi-e) Ab No. 61e; (Ixii) Ab No. 62; (Ixiii) Ab No. 63; (Ixiv) Ab No. 64; (Ixv) Ab No. 65; (Ixvi) Ab No. 66; (Ixvii) Ab No. 67; (Ixviii) Ab No. 68; (Ixviii-a) Ab No. 68a; (Ixviii-b) Ab No. 68b; (Ixviii-c) Ab No. 68c; (Ixviii-d) Ab No. 68d; (Ixviii-e) Ab No. 68e; (Ixviii-f) Ab No. 68f; (Ixix) Ab No. 69; (Ixx) Ab No. 70; (Ixx-a) Ab No. 70a; (Ixx-b) Ab No. 70b; (Ixx-c) Ab No. 70c; (Ixx-d) Ab No. 70d; (Ixx-e) Ab No. 70e; (lxx-1) Ab No. 70f; (Ixxi) Ab No. 71; (Ixxii) Ab No. 72; (Ixxiii) Ab No. 73; (Ixxiv) Ab No. 74; (Ixxv) Ab No. 75; (Ixxvi) Ab No. 76; (Ixxvii) Ab No. 77; (Ixxviii) Ab No. 78; (Ixxix) Ab No. 79; (Ixxx) Ab No. 80; (Ixxxi) Ab No. 81; (Ixxxii) Ab No. 82; (Ixxxiii) Ab No. 83; (Ixxxiii-a) Ab No. 83a; (Ixxxiii-b) Ab No. 83b: (Ixxxiii-c) Ab No. 83c; (Ixxxiii-d) Ab No. 83d; (Ixxxiii-e) Ab No. 83e; (Ixxxiii-f) Ab No. 83f; or (Ixxxiv) Ab No. 84.

[0024] In particular embodiments of (B) above, the anti-CD28 antibody or antigenbinding antibody fragment according to the present disclosure may comprise the VH-1 and optionally a / the VL-1, wherein the amino acid sequences of the CDRH1-1, the CDRH2-1, and the CDRH3-1 comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, and a CDRH3, respectively, contained in the VH of: (1) Ab No. 70; or (2) Ab No. 83.

[0025] In certain embodiments, the anti-CD28 antibody or antigen-binding antibody fragment may comprise: (A) the VH-1 and the VL-1, wherein the amino acid sequences of the CDRH1-1, the CDRH2-1, the CDRH3-1, the CDRL1-1, the CDRL2-1, and the CDRL3-1 in said VH-1 and VL-1 comprise or consist of: (i) SEQ ID NOS: 112, 114, 116, 122, 124, and 126, respectively; (ii) SEQ ID NOS: 212, 214, 216, 222, 224, and 226, respectively; (iii) SEQ ID NOS: 312, 314. 316, 322, 324, and 326, respectively; (iv) SEQ ID NOS: 412. 414, 416. 422, 424, and 426, respectively; (v) SEQ ID NOS: 512, 514, 516, 522, 524, and 526, respectively; (vi) SEQ ID NOS: 612, 614, 616, 622, 624, and 626, respectively; (vii) SEQ ID NOS: 712, 714, 716, 722, 724. and 726, respectively; (viii) SEQ ID NOS: 812, 814, 816. 822, 824, and 826, respectively; (ix) SEQ ID NOS: 912, 914, 916, 922, 924. and 926, respectively; (x) SEQ ID NOS: 1012, 1014, 1016, 1022, 1024, and 1026, respectively; (xi) SEQ ID NOS:1112, 1114, 1116, 1122, 1124, and 1126, respectively; (xii) SEQ ID NOS: 1212, 1214, 1216, 1222, 1224, and 1226, respectively; (xiii) SEQ ID NOS: 1312, 1314, 1316. 1322, 1324, and 1326, respectively; (xiv) SEQ ID NOS: 1412, 1414, 1416, 1422, 1424, and 1426, respectively; (xv) SEQ ID NOS: 1512, 1514, 1516, 1522, 1524, and 1526, respectively; (xvi) SEQ ID NOS: 1612, 1614, 1616, 1622, 1624, and 1626, respectively; (xvii) SEQ ID NOS: 1712, 1714, 1716, 1722, 1724. and 1726, respectively; (xviii) SEQ ID NOS: 1812, 1814.1816, 1822, 1824, and 1826. respectively; (xix) SEQ ID NOS: 1912, 1914. 1916, 1922, 1924, and 1926, respectively; (xx) SEQ ID NOS: 2012, 2014, 2016, 2022, 2024, and 2026, respectively; (xxi) SEQ ID NOS: 2112, 2114, 2116, 2122, 2124, and 2126, respectively; (xxi- a) SEQ ID NOS: 2132, 2134, 2136, 2122, 2124. and 2126, respectively; (xxi-b) SEQ ID NOS: 2142, 2144, 2146, 2122. 2124, and 2126, respectively; (xxi-c) SEQ ID NOS: 2152, 2154, 2156, 2122, 2124, and 2126, respectively; (xxi-d) SEQ ID NOS: 2162, 2164, 2166, 2122, 2124, and 2126, respectively; (xxi-e) SEQ ID NOS: 2172, 2174, 2176, 2122, 2124, and 2126, respectively; (xxi-f) SEQ ID NOS: 2182, 2184, 2186, 2122, 2124, and 2126, respectively; (xxii) SEQ ID NOS: 2212, 2214, 2216, 2222, 2224, and 2226, respectively; (xxm) SEQ ID NOS: 2312, 2314, 2316. 2322. 2324, and 2326. respectively; (xxiv) SEQ ID NOS: 2412, 2414, 2416, 2422, 2424, and 2426, respectively; (xxv) SEQ ID NOS: 2512, 2514, 2516, 2522, 2524, and 2526, respectively; (xxvi) SEQ ID NOS: 2612, 2614, 2616, 2622, 2624, and 2626, respectively; (xxvii) SEQ ID NOS: 2712, 2714, 2716, 2722, 2724, and 2726, respectively; (xxviii) SEQ ID NOS: 2812, 2814, 2816, 2822. 2824. and 2826, respectively; (xxviii-a) SEQ ID NOS: 2832, 2834, 2836, 2822, 2824, and 2826, respectively; (xxviii-b) SEQ ID NOS: 2842, 2844, 2846, 2822, 2824, and 2826, respectively; (xxviii-c) SEQ ID NOS: 2852, 2854, 2856, 2822, 2824, and 2826, respectively; (xxviii-d) SEQ ID NOS: 2862, 2864, 2866, 2822. 2824, and 2826, respectively; (xxviii-e) SEQ ID NOS: 2872, 2874, 2876, 2822, 2824, and 2826, respectively; (xxviii-f) SEQ ID NOS: 2882, 2884, 2886, 2822, 2824, and 2826, respectively; (xxix) SEQ ID NOS: 2912, 2914, 2916, 2922, 2924, and 2926, respectively; (xxx) SEQ ID NOS: 3012, 3014, 3016, 3022, 3024, and 3026, respectively; (xxxi) SEQ ID NOS: 3112, 3114, 3116, 3122, 3124, and 3126, respectively;(xxxn) SEQ ID NOS: 3212, 3214. 3216, 3222, 3224, and 3226. respectively; (xxxin) SEQ ID NOS: 3312, 3314, 3316, 3322, 3324, and 3326, respectively; (xxxiv) SEQ ID NOS: 3412, 3414. 3416, 3422, 3424, and 3426, respectively; (xxxv) SEQ ID NOS: 3512, 3514, 3516, 3522, 3524, and 3526, respectively; (xxxvi) SEQ ID NOS: 3612, 3614, 3616, 3622, 3624, and 3626, respectively; (xxxvii) SEQ ID NOS: 3712, 3714. 3716, 3722, 3724, and 3726. respectively; (xxxviii) SEQ ID NOS: 3812, 3814, 3816, 3822, 3824, and 3826, respectively;(xxxix) SEQ ID NOS: 3912, 3914, 3916, 3922, 3924, and 3926, respectively; (xl) SEQ ID NOS: 4012, 4014, 4016, 4022. 4024, and 4026, respectively; (xli) SEQ ID NOS: 4112. 4114, 4116, 4122, 4124, and 4126, respectively; (xlii) SEQ ID NOS: 4212, 4214, 4216, 4222, 4224, and 4226, respectively; (xliii) SEQ ID NOS: 4312, 4314, 4316, 4322, 4324, and 4326, respectively; (xliv) SEQ ID NOS: 4412, 4414, 4416, 4422, 4424, and 4426, respectively; (xlv) SEQ ID NOS: 4512, 4514, 4516, 4522, 4524, and 4526. respectively; (xlvi) SEQ ID NOS: 4612, 4614, 4616. 4622. 4624, and 4626, respectively; (xlvi-a) SEQ ID NOS: 4632. 4634, 4636, 4622, 4624, and 4626, respectively; (xlvi-b) SEQ ID NOS: 4642, 4644, 4646, 4622, 4624, and 4626, respectively; (xlvi-c) SEQ ID NOS: 4652, 4654, 4656, 4622, 4624, and 4626, respectively; (xlvi-d) SEQ ID NOS: 4662, 4664, 4666, 4622. 4624, and 4626, respectively; (xlvi-e) SEQ ID NOS: 4672. 4674, 4676, 4622, 4624. and 4626, respectively; (xlvii) SEQ ID NOS: 4712, 4714, 4716, 4722, 4724, and 4726, respectively; (xlviii) SEQ ID NOS: 4812, 4814, 4816, 4822, 4824, and 4826, respectively; (xlix) SEQ ID NOS: 4912, 4914, 4916, 4922, 4924, and 4926, respectively; (1) SEQ ID NOS: 5012, 5014, 5016, 5022, 5024, and 5026, respectively; (li) SEQ ID NOS: 5112, 5114, 5116, 5122. 5124, and 5126, respectively; (In) SEQ ID NOS: 5212. 5214, 5216, 5222, 5224. and 5226, respectively; (liii) SEQ ID NOS: 5312, 5314, 5316, 5322, 5324, and 5326, respectively; (liv) SEQ ID NOS: 5412, 5414, 5416, 5422, 5424, and 5426, respectively; (Iv) SEQ ID NOS: 5512, 5514, 5516, 5522, 5524, and 5526, respectively; (Ivi) SEQ ID NOS: 5612, 5614, 5616, 5622, 5624. and 5626, respectively; (Ivii) SEQ ID NOS: 5712. 5714, 5716, 5722, 5724, and 5726, respectively; (Ivii-a) SEQ ID NOS: 5732, 5734, 5736, 5722, 5724, and 5726, respectively; (Ivii-b) SEQ ID NOS: 5742, 5744, 5746, 5722, 5724, and 5726, respectively; (Ivii-c) SEQ ID NOS: 5752, 5754, 5756, 5722. 5724, and 5726, respectively; (Ivii-d) SEQ ID NOS: 5762, 5764, 5766, 5722, 5724, and 5726, respectively; (Ivii-e) SEQ ID NOS: 5772. 5774, 5776, 5722, 5724, and 5726, respectively; (Ivii-f) SEQ ID NOS: 5782, 5784, 5786, 5722, 5724, and 5726, respectively; (Iviii) SEQ ID NOS: 5812, 5814, 5816, 5822, 5824, and 5826, respectively; (lix) SEQ ID NOS: 5912, 5914, 5916, 5922, 5924, and 5926, respectively; (lx) SEQ ID NOS: 6012, 6014. 6016, 6022, 6024, and 6026, respectively; (Ixi) SEQ ID NOS: 6112, 6114, 6116, 6122. 6124. and 6126, respectively; (Ixi-a) SEQ ID NOS: 6132. 6134. 6136, 6122, 6124, and 6126, respectively; (Ixi-b) SEQ ID NOS: 6142, 6144, 6146, 6122, 6124, and 6126, respectively; (Ixi-c) SEQ ID NOS: 6152, 6154, 6156, 6122, 6124, and 6126, respectively; (Ixi-d) SEQ ID NOS: 6162, 6164, 6166, 6122. 6124, and 6126, respectively; (Ixi-e) SEQ ID NOS: 6172, 6174, 6176. 6122. 6124, and 6126, respectively; (Ixii) SEQ ID NOS: 6212, 6214, 6216, 6222, 6224, and 6226, respectively; (Ixiii) SEQ ID NOS: 6312,6314, 6316, 6322, 6324, and 6326, respectively; (Ixiv) SEQ ID NOS: 6412, 6414, 6416, 6422, 6424, and 6426, respectively; (Ixv) SEQ ID NOS: 6512, 6514, 6516. 6522, 6524, and 6526, respectively; (Ixvi) SEQ ID NOS: 6612, 6614, 6616, 6622, 6624, and 6626, respectively; (Ixvii) SEQ ID NOS: 6712, 6714, 6716, 6722, 6724, and 6726, respectively; (Ixviii) SEQ ID NOS: 6812, 6814, 6816, 6822, 6824, and 6826, respectively; (Ixviii-a) SEQ ID NOS: 6832. 6834, 6836, 6822, 6824. and 6826, respectively; (Ixviii-b) SEQ ID NOS: 6842, 6844, 6846, 6822. 6824. and 6826, respectively; (Ixvm-c) SEQ ID NOS: 6852, 6854, 6856, 6822, 6824, and 6826, respectively; (Ixvin-d) SEQ ID NOS: 6862, 6864, 6866, 6822, 6824, and 6826, respectively; (Ixviii-e) SEQ ID NOS: 6872, 6874, 6876, 6822, 6824, and 6826, respectively; (Ixviii-f) SEQ ID NOS: 6882, 6884, 6886, 6822, 6824, and 6826. respectively; or (Ixix) SEQ ID NOS: 6912, 6914, 6916, 6922. 6924, and 6926, respectively.

[0026] In particular embodiments of (A) above, the anti-CD28 antibody or antigenbinding antibody fragment may comprise the VH-1 and the VL-1, wherein the amino acid sequences of the CDRH1-1, the CDRH2-1, the CDRH3-1, the CDRL1-1, the CDRL2-1, and the CDRL3-l in said VH-1 and VL-1 comprise or consist of: (1) SEQ ID NOS: 112, 114, 116, 122. 124, and 126, respectively.

[0027] In particular embodiments of (A) above, the anti-CD28 antibody or antigenbinding antibody fragment may comprise the VH-1 and the VL-1, wherein the VL-1 is a kappa VL. In particular cases, the amino acid sequences of the CDRHl-1, the CDRH2-1, the CDRH3-1. the CDRL1-1, the CDRL2-1, and the CDRL3-1 in said VH-1 and VL-1 may compn se or const st of: (2) SEQ ID NOS : 2112, 2114, 2116, 2122, 2124, and 2126, respectively, or (3) SEQ ID NOS: 2812, 2814, 2816, 2822, 2824, and 2826, respectively.

[0028] In particular embodiments of (A) above, the anti-CD28 antibody or antigenbinding antibody fragment may comprise the VH-1 and the VL-1, wherein the VL-1 is a lambda VL. In particular cases, the amino acid sequences of the CDRHl-1, the CDRH2-1, the CDRH3-1, the CDRL1-1, the CDRL2-1, and the CDRL3-1 in said VH-1 and VL-1 may comprise or consist of: (4) SEQ ID NOS: 4612, 4614, 4616, 4622, 4624, and 4626, respectively; or (5) SEQ ID NOS: 5712. 5714, 5716, 5722, 5724, and 5726, respectively.

[0029] In particular embodiments of (A) above, the anti-CD28 antibody or antigenbinding antibody fragment may comprise the VH-1 and the VL-1, wherein the VL-1 may also be capable of pairing with a VH having specificity for CD3. In particular cases, the amino acid sequences of the CDRHl-1, the CDRH2-1, the CDRH3-1, the CDRL1-1, the CDRL2-1, and the CDRL3-1 in said VH-1 and VL-1 may comprise or consist of: (6) SEQ ID NOS:6112, 6114, 6116, 6122, 6124, and 6126, respectively; or (7) SEQ ID NOS: 6812, 6814, 6816, 6822, 6824, and 6826. respectively.

[0030] In certain embodiments, the VH-1 may be sufficient for binding to CD28 or the VH-1 paired with another VL or VL-1 such as but not limited to one disclosed herein may provide binding to CD28. Therefore, in certain embodiments, the anti-CD28 antibody or antigen-binding antibody fragment may comprise: (B) said VH-1 and optionally said VL- Iwherein the amino acid sequences of the CDRHl-1, the CDRH2-1, and the CDRH3-1 in said VH-1 comprise or consist of: (i) SEQ ID NOS: 112, 114, and 116, respectively; (ii) SEQ ID NOS: 212, 214, and 216, respectively; (iii) SEQ ID NOS: 312, 314, and 316, respectively; (iv) SEQ ID NOS: 412, 414, and 416, respectively; (v) SEQ ID NOS: 512, 514, and 516, respectively; (vi) SEQ ID NOS: 612, 614, and 616, respectively; (vii) SEQ ID NOS: 712, 714, and 716, respectively; (viii) SEQ ID NOS: 812, 814, and 816, respectively; (ix) SEQ ID NOS: 912, 914, and 916, respectively; (x) SEQ ID NOS: 1012, 1014, and 1016, respectively; (xi) SEQ ID NOS: 1112, 1114, and 1116, respectively; (xii) SEQ ID NOS: 1212, 1214, and 1216, respectively; (xiii) SEQ ID NOS: 1312, 1314, and 1316, respectively; (xiv) SEQ ID NOS: 1412, 1414, and 1416. respectively; (xv) SEQ ID NOS: 1512, 1514, and 1516. respectively; (xvi) SEQ ID NOS: 1612, 1614, and 1616, respectively; (xvii) SEQ ID NOS: 1712, 1714, and 1716, respectively; (xviii) SEQ ID NOS: 1812, 1814, and 1816, respectively; (xix) SEQ ID NOS: 1912, 1914, and 1916, respectively; (xx) SEQ ID NOS: 2012, 2014, and 2016, respectively; (xxi) SEQ ID NOS: 2112. 2114. and 2116, respectively; (xxi-a) SEQ ID NOS: 2132, 2134, and 2136, respectively; (xxi-b) SEQ ID NOS: 2142, 2144, and 2146, respectively; (xxi-c) SEQ ID NOS: 2152, 2154, and 2156, respectively; (xxi-d) SEQ ID NOS: 2162, 2164, and 2166, respectively; (xxi-e) SEQ ID NOS: 2172, 2174, and 2176. respectively; (xxi-f) SEQ ID NOS: 2182, 2184, and 2186. respectively; (xxii) SEQ ID NOS: 2212, 2214, and 2216, respectively; (xxiii) SEQ ID NOS: 2312, 2314, and 2316, respectively; (xxiv) SEQ ID NOS: 2412, 2414, and 2416, respectively; (xxv) SEQ ID NOS: 2512, 2514, and 2516, respectively; (xxvi) SEQ ID NOS: 2612, 2614, and 2616, respectively; (xxvii) SEQ ID NOS: 2712, 2714. and 2716, respectively; (xxviii) SEQ ID NOS: 2812, 2814, and 2816, respectively; (xxviii-a) SEQ ID NOS: 2832, 2834, and 2836. respectively; (xxviii-b) SEQ ID NOS: 2842, 2844, and 2846, respectively; (xxviii-c) SEQ ID NOS: 2852, 2854, and 2856, respectively; (xxviii-d) SEQ ID NOS: 2862, 2864, and 2866, respectively; (xxviii-e) SEQ ID NOS: 2872, 2874. and 2876, respectively; (xxviii-f) SEQ ID NOS: 2882, 2884, and 2886, respectively; (xxix) SEQ ID NOS: 2912, 2914, and 2916. respectively; (xxx) SEQ ID NOS: 3012, 3014, and 3016, respectively; (xxxi) SEQ ID NOS: 3112, 3114, and 3116,respectively; (xxxii) SEQ ID NOS: 3212, 3214, and 3216, respectively; (xxxiii) SEQ ID NOS: 3312, 3314, and 3316. respectively; (xxxiv) SEQ ID NOS: 3412. 3414, and 3416, respectively; (xxxv) SEQ ID NOS: 3512, 3514, and 3516, respectively; (xxxvi) SEQ ID NOS: 3612, 3614, and 3616, respectively; (xxxvii) SEQ ID NOS: 3712, 3714, and 3716, respectively; (xxxviii) SEQ ID NOS: 3812, 3814, and 3816, respectively; (xxxix) SEQ ID NOS: 3912, 3914, and 3916. respectively; (xl) SEQ ID NOS: 4012. 4014, and 4016, respectively; (xli) SEQ ID NOS: 4112, 4114, and 4116. respectively; (xlii) SEQ ID NOS: 4212, 4214, and 4216, respectively; (xliii) SEQ ID NOS: 4312, 4314, and 4316, respectively; (xliv) SEQ ID NOS: 4412, 4414, and 4416, respectively; (xlv) SEQ ID NOS: 4512, 4514, and 4516, respectively; (xlvi) SEQ ID NOS: 4612, 4614, and 4616, respectively; (xlvi-a) SEQ ID NOS: 4632, 4634, and 4636. respectively; (xlvi-b) SEQ ID NOS: 4642, 4644, and 4646, respectively; (xlvi-c) SEQ ID NOS: 4652, 4654, and 4656, respectively; (xlvi-d) SEQ ID NOS: 4662, 4664, and 4666, respectively; (xlvi-e) SEQ ID NOS: 4672, 4674, and 4676, respectively; (xlvii) SEQ ID NOS: 4712, 4714, and 4716, respectively; (xlviii) SEQ ID NOS: 4812, 4814, and 4816, respectively; (xlix) SEQ ID NOS: 4912, 4914. and 4916, respectively; (1) SEQ ID NOS: 5012, 5014, and 5016. respectively; (li) SEQ ID NOS: 5112. 5114. and 5116, respectively; (lii) SEQ ID NOS: 5212, 5214, and 5216, respectively; (liii) SEQ ID NOS: 5312, 5314, and 5316, respectively; (liv) SEQ ID NOS: 5412, 5414, and 5416, respectively; (Iv) SEQ ID NOS: 5512, 5514, and 5516, respectively; (Ivi) SEQ ID NOS: 5612, 5614, and 5616, respectively; (Ivii) SEQ ID NOS: 5712, 5714, and 5716, respectively: (Ivii-a) SEQ ID NOS: 5732, 5734, and 5736, respectively; (Ivii-b) SEQ ID NOS: 5742, 5744, and 5746, respectively; (Ivii-c) SEQ ID NOS: 5752, 5754, and 5756, respectively; (Ivii-d) SEQ ID NOS: 5762, 5764. and 5766, respectively; (Ivii-e) SEQ ID NOS: 5772, 5774, and 5776, respectively; (Ivii-f) SEQ ID NOS: 5782, 5784. and 5786, respectively; (Iviii) SEQ ID NOS: 5812, 5814, and 5816, respectively; (lix) SEQ ID NOS: 5912, 5914, and 5916, respectively; (lx) SEQ ID NOS: 6012, 6014, and 6016, respectively; (Ixi) SEQ ID NOS: 6112, 6114, and 6116, respectively; (Ixi-a) SEQ ID NOS: 6132, 6134, and 6136, respectively; (Ixi-b) SEQ ID NOS: 6142, 6144, and 6146, respectively: (Ixi-c) SEQ ID NOS: 6152, 6154, and 6156, respectively; (Ixi-d) SEQ ID NOS: 6162. 6164. and 6166, respectively; (Ixi-e) SEQ ID NOS: 6172, 6174, and 6176, respectively; (Ixii) SEQ ID NOS: 6212, 6214, and 6216, respectively; (Ixiii) SEQ ID NOS: 6312, 6314, and 6316, respectively; (Ixiv) SEQ ID NOS: 6412, 6414, and 6416, respectively; (Ixv) SEQ ID NOS: 6512, 6514, and 6516, respectively; (Ixvi) SEQ ID NOS: 6612. 6614, and 6616, respectively; (Ixvii) SEQ ID NOS: 6712. 6714, and 6716, respectively; (Ixviii) SEQ ID NOS: 6812, 6814, and 6816, respectively; (Ixviii-a)SEQ ID NOS: 6832, 6834. and 6836, respectively; (Ixviii-b) SEQ ID NOS: 6842, 6844, and 6846, respectively; (Ixviii-c) SEQ ID NOS: 6852, 6854, and 6856, respectively; (Ixviii-d) SEQ ID NOS: 6862, 6864, and 6866, respectively; (Ixvm-e) SEQ ID NOS: 6872, 6874, and 6876, respectively; (Ixviii-f) SEQ ID NOS: 6882, 6884, and 6886, respectively; (Ixix) SEQ ID NOS: 6912, 6914, and 6916, respectively; (Ixx) SEQ ID NOS: 7012, 7014, and 7016, respectively; (Ixx-a) SEQ ID NOS: 7032, 7034, and 7036, respectively; (Ixx-b) SEQ ID NOS: 7042, 7044, and 7046, respectively; (Ixx-c) SEQ ID NOS: 7052, 7054, and 7056. respectively; (Ixx-d) SEQ ID NOS: 7062, 7064, and 7066, respectively; (Ixx-e) SEQ ID NOS: 7072, 7074, and 7076, respectively; (Ixx-f) SEQ ID NOS: 7082, 7084, and 7086, respectively; (Ixxi) SEQ ID NOS: 7112, 7114, and 7116, respectively; (Ixxii) SEQ ID NOS: 7212, 7214, and 7216, respectively; (Ixxiii) SEQ ID NOS: 7312, 7314, and 7316, respectively; (Ixxiv) SEQ ID NOS: 7412, 7414, and 7416, respectively; (Ixxv) SEQ ID NOS: 7512, 7514, and 7516, respectively; (Ixxvi) SEQ ID NOS: 7612, 7614, and 7616, respectively; (Ixxvii) SEQ ID NOS: 7712, 7714, and 7716, respectively; (Ixxviii) SEQ ID NOS: 7812, 7814, and 7816. respectively; (Ixxix) SEQ ID NOS: 7912, 7914. and 7916, respectively; (Ixxx) SEQ ID NOS: 8012, 8014, and 8016. respectively; (Ixxxi) SEQ ID NOS: 8112, 8114, and 8116, respectively; (Ixxxii) SEQ ID NOS: 8212, 8214, and 8216, respectively; (Ixxxiii) SEQ ID NOS: 8312, 8314, and 8316, respectively; (Ixxxiii-a) SEQ ID NOS: 8332, 8334, and 8336. respectively; (Ixxxiii-b) SEQ ID NOS: 8342, 8344, and 8346, respectively; (Ixxxiii-c) SEQ ID NOS: 8352, 8354, and 8356. respectively; (Ixxxiii-d) SEQ ID NOS: 8362, 8364, and 8366, respectively; (Ixxxiii-e) SEQ ID NOS: 8372, 8374, and 8376, respectively; (Ixxxiii-f) SEQ ID NOS: 8382, 8384, and 8386, respectively; or (Ixxxiv) SEQ ID NOS: 8412, 8414, and 8416, respectively.

[0031] In particular embodiments of (B) above, for example when the VH-1 may be sufficient for binding to CD28 or the VH-1 paired with another VL or VL-1 such as but not limited to one disclosed herein may provide binding to CD28, the anti-CD28 antibody or antigen-binding antibody fragment may comprise: the VH-1 and optionally the VL-1 wherein the amino acid sequences of the CDRH1-1, the CDRH2-1, and the CDRH3-1 in said VH-1 comprise or consist of: (1) SEQ ID NOS: 7012. 7014. and 7016, respectively; or (2) SEQ ID NOS: 8312, 8314, and 8316, respectively.

[0032] In certain embodiments, the amino acid sequence of the VH-1 may comprise or consist of one of the VH amino acid sequences listed in Table 1A and / or 12A or a variant thereof having at least about 80%, 85%. 90%. 91%. 92%. 93%. 94%. 95%. 96%. 97%. 98%. or 99% sequence identity thereto.

[0033] In certain embodiments, the amino acid sequence of the VL-1 may comprise or consist of one of the VL amino acid sequences listed in Table 1A and / or 12A or a variant thereof having at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto.

[0034] In certain embodiments, the amino acid sequence of the VH-1 may be encoded by a nucleic acid sequence comprising or consisting of one of the VH-encoding nucleic acid sequences listed in Table 2A and / or 13A or a variant thereof having at least about 80%. 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto.

[0035] In certain embodiments, the amino acid sequence of the VL-1 may be encoded by a nucleic acid sequence comprising or consisting of any one of the VL-encoding nucleic acid sequence listed in Table 2A and / or 13A or a variant thereof having at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto.

[0036] In certain embodiments, in (A) above, the amino acid sequences of the VH-1 and the VL-1 may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%. at least about 93%, at least about 94%, at least about 95%, at least about 96%. at least about 97%, at least about 98%, at least or at least about 99% sequence identity to: in (i), SEQ ID NOS: 110 and 120, respectively; in (ii), SEQ ID NOS: 210 and 220, respectively; in (iii), SEQ ID NOS: 310 and 320, respectively; in (iv), SEQ ID NOS: 410 and 420, respectively; in (v). SEQ ID NOS: 510 and 520, respectively; in (vi), SEQ ID NOS: 610 and 620. respectively; in (vii). SEQ ID NOS: 710 and 720, respectively; in (viii), SEQ ID NOS: 810 and 820, respectively; in (ix), SEQ ID NOS: 910 and 920, respectively; in (x), SEQ ID NOS: 1010 and 1020, respectively; in (xi), SEQ ID NOS: 1110 and 1120, respectively; in (xii), SEQ ID NOS: 1210 and 1220, respectively; in (xiii), SEQ ID NOS: 1310 and 1320, respectively; in (xiv), SEQ ID NOS: 1410 and 1420, respectively; in (xv), SEQ ID NOS: 1510 and 1520, respectively; in (xvi), SEQ ID NOS: 1610 and 1620, respectively; in (xvii), SEQ ID NOS: 1710 and 1720, respectively; in (xviii), SEQ ID NOS: 1810 and 1820, respectively; in (xix), SEQ ID NOS: 1910 and 1920, respectively; in (xx), SEQ ID NOS: 2010 and 2020, respectively; in (xxi), SEQ ID NOS: 2110 and 2120, respectively; in (xxi-a), SEQ ID NOS: 2130 and 2120, respectively; in (xxi-b). SEQ ID NOS: 2140 and 2120, respectively; in (xxi-c), SEQ ID NOS: 2150 and 2120, respectively; in (xxi- d), SEQ ID NOS: 2160 and 2120, respectively; in (xxi-e), SEQ ID NOS: 2170 and 2120, respectively; in (xxi-1), SEQ ID NOS: 2180 and 2120, respectively: in (xxii), SEQ ID NOS: 2210 and 2220, respectively; in (xxiii), SEQ ID NOS: 2310 and 2320, respectively; in (xxiv), SEQ ID NOS: 2410 and 2420, respectively; in (xxv), SEQ ID NOS: 2510 and 2520,respectively; in (xxvi), SEQ ID NOS: 2610 and 2620, respectively; in (xxvii), SEQ ID NOS: 2710 and 2720, respectively; in (xxviii). SEQ ID NOS: 2810 and 2820. respectively; in (xxviii-a), SEQ ID NOS: 2830 and 2820, respectively; in (xxviii-b), SEQ ID NOS: 2840 and 2820, respectively; in (xxviii-c), SEQ ID NOS: 2850 and 2820, respectively; in (xxviii-d), SEQ ID NOS: 2860 and 2820, respectively; in (xxviii-e), SEQ ID NOS: 2870 and 2820, respectively; in (xxviii-f), SEQ ID NOS: 2880 and 2820, respectively; in (xxix), SEQ ID NOS: 2910 and 2920, respectively; in (xxx), SEQ ID NOS: 3010 and 3020, respectively: in (xxxi), SEQ ID NOS: 3110 and 3120, respectively; in (xxxii), SEQ ID NOS: 3210 and 3220, respectively; in (xxxiii), SEQ ID NOS: 3310 and 3320, respectively; in (xxxiv), SEQ ID NOS: 3410 and 3420, respectively; in (xxxv), SEQ ID NOS: 3510 and 3520, respectively; in (xxxvi), SEQ ID NOS: 3610 and 3620, respectively; in (xxxvii), SEQ ID NOS: 3710 and 3720, respectively; in (xxxviii), SEQ ID NOS: 3810 and 3820, respectively; in (xxxix), SEQ ID NOS: 3910 and 3920, respectively; in (xl), SEQ ID NOS: 4010 and 4020, respectively; in (xli), SEQ ID NOS: 4110 and 4120, respectively; in (xlii), SEQ ID NOS: 4210 and 4220, respectively; in (xliii), SEQ ID NOS: 4310 and 4320, respectively; in (xliv), SEQ ID NOS: 4410 and 4420, respectively; in (xlv), SEQ ID NOS: 4510 and 4520, respectively; in (xlvi), SEQ ID NOS: 4610 and 4620, respectively; in (xlvi-a), SEQ ID NOS: 4630 and 4620, respectively; in (xlvi-b), SEQ ID NOS: 4640 and 4620, respectively; in (xlvi-c), SEQ ID NOS: 4650 and 4620, respectively; in (xlvi-d), SEQ ID NOS: 4660 and 4620, respectively; in (xlvi-e), SEQ ID NOS: 4670 and 4620, respectively; in (xlvii), SEQ ID NOS: 4710 and 4720, respectively; in (xlviii), SEQ ID NOS: 4810 and 4820, respectively; in (xlix), SEQ ID NOS: 4910 and 4920, respectively; in (1), SEQ ID NOS: 5010 and 5020, respectively; in (li), SEQ ID NOS: 5110 and 5120, respectively; in (lii), SEQ ID NOS: 5210 and 5220, respectively; in (liii), SEQ ID NOS: 5310 and 5320, respectively; in (liv). SEQ ID NOS: 5410 and 5420. respectively; in (Iv), SEQ ID NOS: 5510 and 5520, respectively; in (Ivi), SEQ ID NOS: 5610 and 5620, respectively; in (Ivii), SEQ ID NOS: 5710 and 5720, respectively; in (Ivii-a), SEQ ID NOS: 5730 and 5720, respectively; in (Ivii-b), SEQ ID NOS: 5740 and 5720, respectively; in (Ivii-c), SEQ ID NOS: 5750 and 5720, respectively; in (Ivii-d). SEQ ID NOS: 5760 and 5720, respectively; in (Ivii-e), SEQ ID NOS: 5770 and 5720, respectively; in (Ivii-f). SEQ ID NOS: 5780 and 5720, respectively; in (Iviii), SEQ ID NOS: 5810 and 5820, respectively; in (lix), SEQ ID NOS: 5910 and 5920, respectively; in (lx), SEQ ID NOS: 6010 and 6020, respectively; in (Ixi), SEQ ID NOS: 6110 and 6120, respectively; in (Ixi-a), SEQ ID NOS: 6130 and 6120, respectively; in (Ixi-b), SEQ ID NOS: 6140 and 6120, respectively; in (Ixi-c), SEQ ID NOS: 6150 and 6120, respectively; in (Ixi-d), SEQ ID NOS: 6160 and 6120,respectively; in (Ixi-e), SEQ ID NOS: 6170 and 6120, respectively; in (Ixii), SEQ ID NOS: 6210 and 6220, respectively; in (Ixiii). SEQ ID NOS: 6310 and 6320. respectively; in (Ixiv), SEQ ID NOS: 6410 and 6420, respectively; in (Ixv), SEQ ID NOS: 6510 and 6520, respectively; in (Ixvi), SEQ ID NOS: 6610 and 6620, respectively; in (Ixvii), SEQ ID NOS: 6710 and 6720, respectively; in (Ixviii-a), SEQ ID NOS: 6830 and 6820, respectively; in (Ixviii-b), SEQ ID NOS: 6840 and 6820, respectively; in (Ixviii-c), SEQ ID NOS: 6850 and 6820, respectively; in (Ixviii-d), SEQ ID NOS: 6860 and 6820, respectively; in (Ixviii-e), SEQ ID NOS: 6870 and 6820, respectively; in (Ixviii-f), SEQ ID NOS: 6880 and 6820, respectively; in (Ixviii), SEQ ID NOS: 6810 and 6820, respectively; or in (Ixix), SEQ ID NOS: 6910 and 6920, respectively.

[0037] In particular embodiments, in (A) above, the amino acid sequences of the VH-1 and the VL-1 may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least or at least about 99% sequence identity to: in (1), SEQ ID NOS: 110 and 120. respectively (i.e., while comprising the heavy and light chain CDRs of Ab No. 1); in (2), SEQ ID NOS: 2110 and 2120, respectively (i.e., while comprising the heavy and light chain CDRs of Ab No. 21); in (3), SEQ ID NOS: 2810 and 2820, respectively (i.e., while comprising the heavy and light chain CDRs of Ab No. 28); in (4), SEQ ID NOS: 4610 and 4620, respectively (i.e.. while comprising the heavy and light chain CDRs of Ab No. 46); in (5), SEQ ID NOS: 5710 and 5720, respectively (i.e., while comprising the heavy and light chain CDRs of Ab No. 57); in (6), SEQ ID NOS: 6110 and 6120, respectively (i.e., while comprising the heavy and light chain CDRs of Ab No. 61); or in (7), SEQ ID NOS: 6810 and 6820, respectively (i.e., while comprising the heavy and light chain CDRs of Ab No. 68).

[0038] In certain embodiments, in (B) above, the amino acid sequence of the VH- 1 may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least or at least about 99% sequence identity to: in (i), SEQ ID NO: 110; in (h). SEQ ID NO: 210; in (hi), SEQ ID NO: 310; in (iv). SEQ ID NO: 410; in (v), SEQ ID NO: 510; in (vi), SEQ ID NO: 610; in (vii), SEQ ID NO: 710; in (viii), SEQ ID NO: 810; in (ix), SEQ ID NO: 910; in (x), SEQ ID NO: 1010; in (xi), SEQ ID NO: 1110; in (xii), SEQ ID NO: 1210; in (xiii), SEQ ID NO: 1310; in (xiv), SEQ ID NO: 1410; in (xv), SEQ ID NO: 1510; in (xvi), SEQ ID NO: 1610; in (xvii), SEQ ID NO: 1710; in (xviii). SEQ ID NO: 1810; in (xix), SEQ ID NO: 1910; in (xx), SEQ ID NO: 2010; in (xxi), SEQ IDNO: 2110; in (xxi-a), SEQ ID NO: 2130; in (xx-b), SEQ ID NO: 2140; in (xxi-c), SEQ ID NO: 2150; in (xxi-d), SEQ ID NO: 2160; in (xxi-e). SEQ ID NO: 2170; in (xxi-f), SEQ ID NO: 2180; in (xxii), SEQ ID NO: 2210; in (xxiii), SEQ ID NO: 2310; in (xxiv), SEQ ID NO: 2410; in (xxv), SEQ ID NO: 2510; in (xxvi), SEQ ID NO: 2610; in (xxvii), SEQ ID NO: 2710; in (xxviii), SEQ ID NO: 2810; in (xxv iii-a), SEQ ID NO: 2830; in (xxviii-b), SEQ ID NO: 2840; in (xxviii-c), SEQ ID NO: 2850; in (xxviii-d), SEQ ID NO: 2860; in (xxviii-e), SEQ ID NO: 2870; in (xxvin-f). SEQ ID NO: 2880; in (xxix), SEQ ID NO: 2910; in (xxx), SEQ ID NO: 3010; in (xxxi), SEQ ID NO: 3110; in (xxxii), SEQ ID NO: 3210; in (xxxiii), SEQ ID NO: 3310; in (xxxiv), SEQ ID NO: 3410; in (xxxv), SEQ ID NO: 3510; in (xxxvi), SEQ ID NO: 3610; in (xxxvii), SEQ ID NO: 3710; in (xxxviii), SEQ ID NO: 3810; in (xxxix), SEQ ID NO: 3910; in (xl), SEQ ID NO: 4010; in (xli). SEQ ID NO: 4110; in (xlii), SEQ ID NO: 4210; in (xliii), SEQ ID NO: 4310; in (xliv), SEQ ID NO: 4410; in (xlv), SEQ ID NO: 4510; in (xlv i), SEQ ID NO: 4610; in (xlvi-a), SEQ ID NO: 4630; in (xlvi-b), SEQ ID NO: 4640; in (xlvi-c), SEQ ID NO: 4650; in (xlvi-d), SEQ ID NO: 4660; in (xlvi-e), SEQ ID NO: 4670; in (xlvii), SEQ ID NO: 4710; in (xlviii), SEQ ID NO: 4810; in (xlix), SEQ ID NO: 4910; in (1). SEQ ID NO: 5010; in (li). SEQ ID NO: 5110; in (hi). SEQ ID NO: 5210; in (liii), SEQ ID NO: 5310; in (liv), SEQ ID NO: 5410; in (Iv), SEQ ID NO: 5510; in (Ivi), SEQ ID NO: 5610; in (Ivii), SEQ ID NO: 5710; in (Ivii-a), SEQ ID NO: 5730; in (Ivii-b), SEQ ID NO: 5740; in (Ivii-c), SEQ ID NO: 5750; in (Ivii-d), SEQ ID NO: 5760; in (Ivii-e), SEQ ID NO: 5770; in (Ivii-f), SEQ ID NO: 5780; in (Iviii), SEQ ID NO: 5810; in (lix), SEQ ID NO: 5910; in (lx), SEQ ID NO: 6010; in (Ixi), SEQ ID NO: 6110; in (Ixi-a), SEQ ID NO: 6130; in (Ixi-b), SEQ ID NO: 6140; in (Ixi-c), SEQ ID NO: 6150; in (Ixi-d), SEQ ID NO: 6160; in (Ixi-e), SEQ ID NO: 6170; in (Ixii), SEQ ID NO: 6210; in (Ixiii), SEQ ID NO: 6310; in (Ixiv), SEQ ID NO: 6410; in (Ixv), SEQ ID NO: 6510; in (Ixvi), SEQ ID NO: 6610; in (Ixvii), SEQ ID NO: 6710; in (Ixvih), SEQ ID NO: 6810; in (Ixviii-a), SEQ ID NO: 6830; in (Ixvhi- b), SEQ ID NO: 6840; in (Ixviii-c), SEQ ID NO: 6850; in (Ixviii-d), SEQ ID NO: 6860; in (Ixviii-e), SEQ ID NO: 6870; in (Ixviii-f), SEQ ID NO: 6880; in (Ixix), SEQ ID NO: 6910; in (Ixx). SEQ ID NO: 7010; in (Ixx-a), SEQ ID NO: 7030; in (Ixx-b), SEQ ID NO: 7040; in (Ixx-c). SEQ ID NO: 7050; in (Ixx-d). SEQ ID NO: 7060; in (Ixx-e), SEQ ID NO: 7070; in (Ixx-f), SEQ ID NO: 7080; in (Ixxi), SEQ ID NO: 7110; in (Ixxii), SEQ ID NO: 7210; in (Ixxiii), SEQ ID NO: 7310; in (Ixxiv), SEQ ID NO: 7410; in (Ixxv), SEQ ID NO: 7510; in (Ixxvi). SEQ ID NO: 7610; in (Ixxvii), SEQ ID NO: 7710; in (Ixxviii), SEQ ID NO: 7810; or in (Ixxix), SEQ ID NO: 7910; in (Ixxx), SEQ ID NO: 8010; in (Ixxxi), SEQ ID NO: 8110; in (Ixxxii), SEQ ID NO: 8210; in (Ixxxiii), SEQ ID NO: 8310; in (Ixxxiii-a), SEQ ID NO: 8330;in (Ixxxiii-b), SEQ ID NO: 8340; in (Ixxxiii-c), SEQ ID NO: 8350; in (Ixxxiii-d), SEQ ID NO: 8360; in (Ixxxiii-e). SEQ ID NO: 8370; in (Ixxxiii-f), SEQ ID NO: 8380; or in (Ixxxiv). SEQ ID NO: 8410.

[0039] In particular embodiments, in (B) above, the amino acid sequence of the VH-1 may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%. at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%. at least about 98%. at least or at least about 99% sequence identity to: in (1), SEQ ID NO: 7010 (i.e., while comprising the heavy and light chain CDRs of Ab No. 70); or in (2) SEQ ID NO: 8310 (i.e., while comprising the heavy and light chain CDRs of Ab No. 831).

[0040] In particular embodiments, in (A) above, the amino acid sequences of the VH-1 and the VL-1 may comprise or consist of: in (i), SEQ ID NOS: 110 and 120, respectively; in (ii), SEQ ID NOS: 210 and 220, respectively; in (lii), SEQ ID NOS: 310 and 320, respectively; in (iv), SEQ ID NOS: 410 and 420, respectively; in (v), SEQ ID NOS: 510 and 520, respectively; in (vi), SEQ ID NOS: 610 and 620. respectively; in (vii). SEQ ID NOS: 710 and 720. respectively; in (viii), SEQ ID NOS: 810 and 820. respectively; in (ix). SEQ ID NOS: 910 and 920, respectively; in (x), SEQ ID NOS: 1010 and 1020, respectively; in (xi), SEQ ID NOS: 1110 and 1120, respectively; in (xii), SEQ ID NOS: 1210 and 1220, respectively; in (xiii), SEQ ID NOS: 1310 and 1320, respectively; in (xiv), SEQ ID NOS: 1410 and 1420, respectively; in (xv), SEQ ID NOS: 1510 and 1520, respectively; in (xvi), SEQ ID NOS: 1610 and 1620, respectively; in (xvii), SEQ ID NOS: 1710 and 1720, respectively; in (xviii), SEQ ID NOS: 1810 and 1820, respectively; in (xix), SEQ ID NOS: 1910 and 1920, respectively; in (xx), SEQ ID NOS: 2010 and 2020, respectively; in (xxi), SEQ ID NOS: 2110 and 2120. respectively; in (xxi-a), SEQ ID NOS: 2130 and 2120, respectively; in (xxi-b), SEQ ID NOS: 2140 and 2120, respectively; in (xxi-c), SEQ ID NOS: 2150 and 2120, respectively; in (xxi-d), SEQ ID NOS: 2160 and 2120, respectively; in (xxi- e), SEQ ID NOS: 2170 and 2120, respectively; in (xxi-f), SEQ ID NOS: 2180 and 2120, respectively; in (xxii), SEQ ID NOS: 2210 and 2220, respectively; in (xxiii), SEQ ID NOS: 2310 and 2320, respectively; in (xxiv), SEQ ID NOS: 2410 and 2420, respectively; in (xxv). SEQ ID NOS: 2510 and 2520, respectively; in (xxvi), SEQ ID NOS: 2610 and 2620, respectively; in (xxvii), SEQ ID NOS: 2710 and 2720, respectively; in (xxviii), SEQ ID NOS: 2810 and 2820, respectively; in (xxviii-a), SEQ ID NOS: 2830 and 2820, respectively; in (xxviii-b), SEQ ID NOS: 2840 and 2820, respectively; in (xxviii-c), SEQ ID NOS: 2850 and 2820, respectively; in (xxviii-d), SEQ ID NOS: 2860 and 2820, respectively; in (xxviii-e), SEQ ID NOS: 2870 and 2820, respectively; in (xxviii-f), SEQ ID NOS: 2880 and 2820, respectively; in (xxix). SEQ ID NOS: 2910 and 2920. respectively; in (xxx), SEQ ID NOS: 3010 and 3020, respectively; in (xxxi), SEQ ID NOS: 3110 and 3120, respectively; in (xxxii), SEQ ID NOS: 3210 and 3220, respectively; in (xxxiii), SEQ ID NOS: 3310 and 3320, respectively; in (xxxiv), SEQ ID NOS: 3410 and 3420, respectively ; in (xxxv), SEQ ID NOS: 3510 and 3520, respectively; in (xxxvi), SEQ ID NOS: 3610 and 3620, respectively; in (xxxvii), SEQ ID NOS: 3710 and 3720, respectively; in (xxxviii), SEQ ID NOS: 3810 and 3820, respectively; in (xxxix), SEQ ID NOS: 3910 and 3920, respectively; in (xl), SEQ ID NOS: 4010 and 4020, respectively; in (xli), SEQ ID NOS: 4110 and 4120, respectively; in (xlii), SEQ ID NOS: 4210 and 4220, respectively; in (xliii), SEQ ID NOS: 4310 and 4320, respectively; in (xliv), SEQ ID NOS: 4410 and 4420, respectively; in (xlv). SEQ ID NOS: 4510 and 4520, respectively; in (xlvi), SEQ ID NOS: 4610 and 4620, respectively; in (xlvi-a), SEQ ID NOS: 4630 and 4620, respectively; in (xlvi-b), SEQ ID NOS: 4640 and 4620, respectively; in (xlvi-c), SEQ ID NOS: 4650 and 4620, respectively; in (xlvi-d), SEQ ID NOS: 4660 and 4620, respectively; in (xlvi-e), SEQ ID NOS: 4670 and 4620, respectively; in (xlvn). SEQ ID NOS: 4710 and 4720. respectively; in (xlvm), SEQ ID NOS: 4810 and 4820, respectively; in (xlix), SEQ ID NOS: 4910 and 4920, respectively; in (1), SEQ ID NOS: 5010 and 5020, respectively; in (li), SEQ ID NOS: 5110 and 5120, respectively; in (lii), SEQ ID NOS: 5210 and 5220, respectively; in (liii), SEQ ID NOS: 5310 and 5320, respectively; in (liv), SEQ ID NOS: 5410 and 5420, respectively; in (Iv), SEQ ID NOS: 5510 and 5520, respectively; in (Ivi), SEQ ID NOS: 5610 and 5620, respectively; in (Ivii), SEQ ID NOS: 5710 and 5720, respectively; in (Ivii-a), SEQ ID NOS: 5730 and 5720, respectively; in (Ivii- b), SEQ ID NOS: 5740 and 5720, respectively; in (Ivii-c). SEQ ID NOS: 5750 and 5720. respectively; in (Ivii-d), SEQ ID NOS: 5760 and 5720, respectively; in (Ivii-e). SEQ ID NOS: 5770 and 5720, respectively; in (Ivii-f), SEQ ID NOS: 5780 and 5720, respectively; in (Iviii), SEQ ID NOS: 5810 and 5820, respectively; in (lix), SEQ ID NOS: 5910 and 5920, respectively; in (lx), SEQ ID NOS: 6010 and 6020, respectively; in (Ixi), SEQ ID NOS: 6110 and 6120, respectively; in (Ixi-a), SEQ ID NOS: 6130 and 6120, respectively; in (Ixi-b), SEQ ID NOS: 6140 and 6120, respectively; in (Ixi-c), SEQ ID NOS: 6150 and 6120, respectively; in (Ixi-d), SEQ ID NOS: 6160 and 6120, respectively; in (Ixi-e), SEQ ID NOS: 6170 and 6120, respectively; in (Ixii), SEQ ID NOS: 6210 and 6220, respectively; in (Ixiii), SEQ ID NOS: 6310 and 6320, respectively; in (Ixiv), SEQ ID NOS: 6410 and 6420, respectively; in (Ixv). SEQ ID NOS: 6510 and 6520. respectively; in (Ixvi), SEQ ID NOS: 6610 and 6620, respectively; in (Ixvii), SEQ ID NOS: 6710 and 6720, respectively; in (Ixviii), SEQ ID NOS:6810 and 6820, respectively; in (Ixviii-a), SEQ ID NOS: 6830 and 6820, respectively; in (Ixviii-b), SEQ ID NOS: 6840 and 6820, respectively; in (Ixviii-c), SEQ ID NOS: 6850 and 6820, respectively; in (Ixviii-d), SEQ ID NOS: 6860 and 6820, respectively; in (Ixviii-e), SEQ ID NOS: 6870 and 6820, respectively; in (Ixviii-f), SEQ ID NOS: 6880 and 6820, respectively; or in (Ixix), or SEQ ID NOS: 6910 and 6920, respectively.

[0041] In particular embodiments of (A) above, in some cases, the amino acid sequences of the VH-1 and the VL-1 may comprise or consist of: in (1). SEQ ID NOS: 110 and 120.

[0042] In particular embodiments of (A) above, in some cases, the VL-1 may be a kappa VL. In particular cases, the amino acid sequences of the VH-1 and the VL-1 may comprise or consist of: in (2), SEQ ID NOS: 2110 and 2120. respectively; or in (3), SEQ ID NOS: 2810 and 2820, respectively.

[0043] In particular embodiments of (A) above, in some cases, the VL-1 may be a lambda VL. In particular cases, the amino acid sequences of the VH-1 and the VL-1 may comprise or consist of: in (4), SEQ ID NOS: 4610 and 4620, respectively; or in (5), SEQ ID NOS: 5710 and 5720, respectively.

[0044] In particular embodiments of (A) above, in some cases, the VL-1 may also be capable of pairing with a VH having specificity for CD3 (i.e., a common VL which may be shared by a CD28-binding region and a CD3-binding region). In particular cases, the amino acid sequences of the VH-1 and the VL-1 may comprise or consist of: in (6), SEQ ID NOS: 6110 and 6120, respectively; or in (7). SEQ ID NOS: 6810 and 6820. respectively.

[0045] In particular embodiments, in (B) above, the amino acid sequence of the VH-1 may comprise or consist of: in (i), SEQ ID NO: 110; in (ii), SEQ ID NO: 210; in (iii), SEQ ID NO: 310; in (iv), SEQ ID NO: 410; in (v), SEQ ID NO: 510; in (vi), SEQ ID NO: 610; in (vii), SEQ ID NO: 710; in (viii), SEQ ID NO: 810; in (ix), SEQ ID NO: 910; in (x), SEQ ID NO: 1010; in (xi), SEQ ID NO: 1110; in (xh), SEQ ID NO: 1210; in (xih), SEQ ID NO: 1310; in (xiv), SEQ ID NO: 1410; in (xv), SEQ ID NO: 1510; in (xvi), SEQ ID NO: 1610; in (xvii), SEQ ID NO: 1710; in (xviii), SEQ ID NO: 1810; in (xix), SEQ ID NO: 1910; in (xx), SEQ ID NO: 2010; in (xxi), SEQ ID NO: 2110; in (xxi-a), SEQ ID NO: 2130; in (xx-b), SEQ ID NO: 2140; in (xxi-c). SEQ ID NO: 2150; in (xxi-d), SEQ ID NO: 2160; in (xxi-e), SEQ ID NO: 2170; in (xxi-f), SEQ ID NO: 2180; in (xxii), SEQ ID NO: 2210; in (xxiii), SEQ ID NO: 2310; in (xxiv), SEQ ID NO: 2410; in (xxv), SEQ ID NO: 2510; in (xxvi), SEQ ID NO: 2610; in (xxvii), SEQ ID NO: 2710; in (xxviii), SEQ ID NO: 2810; in (xxviii-a), SEQ ID NO: 2830; in (xxviii-b), SEQ ID NO: 2840; in (xxviii-c), SEQ ID NO: 2850; in (xxviii-d). SEQ ID NO: 2860; in (xxvm-e), SEQ ID NO: 2870; in (xxviii-f), SEQ ID NO: 2880; in(xxix), SEQ ID NO: 2910; in (xxx), SEQ ID NO: 3010; in (xxxi). SEQ ID NO: 3110; in (xxxii). SEQ ID NO: 3210; in (xxxiii), SEQ ID NO: 3310; in (xxxiv), SEQ ID NO: 3410; in (xxxv), SEQ ID NO: 3510; in (xxxvi), SEQ ID NO: 3610; in (xxxvii), SEQ ID NO: 3710; in (xxxviii), SEQ ID NO: 3810; in (xxxix), SEQ ID NO: 3910; in (xl), SEQ ID NO: 4010; in (xli), SEQ ID NO: 4110; in (xlii), SEQ ID NO: 4210; in (xliii), SEQ ID NO: 4310; in (xliv), SEQ ID NO: 4410; in (xlv), SEQ ID NO: 4510; in (xlvi), SEQ ID NO: 4610; in (xlvi-a), SEQ ID NO: 4630; in (xlvi-b), SEQ ID NO: 4640; in (xlvi-c), SEQ ID NO: 4650; in (xlvi-d), SEQ ID NO: 4660; in (xlvi-e), SEQ ID NO: 4670; in (xlvii), SEQ ID NO: 4710; in (xlviii), SEQ ID NO: 4810; in (xlix), SEQ ID NO: 4910; in (1), SEQ ID NO: 5010; in (li), SEQ ID NO: 5110; in (lii). SEQ ID NO: 5210; in (liii), SEQ ID NO: 5310; in (liv), SEQ ID NO: 5410; in (Iv), SEQ ID NO: 5510; in (Ivi). SEQ ID NO: 5610; in (Ivii), SEQ ID NO: 5710; in (Ivii-a), SEQ ID NO: 5730; in (Ivii-b), SEQ ID NO: 5740; in (Ivii-c), SEQ ID NO: 5750; in (Ivii-d), SEQ ID NO: 5760; in (Ivii-e), SEQ ID NO: 5770; in (Ivii-f), SEQ ID NO: 5780; in (Iviii), SEQ ID NO: 5810; in (lix), SEQ ID NO: 5910; in (lx), SEQ ID NO: 6010; in (Ixi), SEQ ID NO: 6110; in (Ixi-a), SEQ ID NO: 6130; in (Ixi-b), SEQ ID NO: 6140; in (Ixi-c), SEQ ID NO: 6150; in (Ixi-d). SEQ ID NO: 6160; in (Ixi-e), SEQ ID NO: 6170; in (Ixn), SEQ ID NO: 6210; in (Ixiii), SEQ ID NO: 6310; in (Ixiv), SEQ ID NO: 6410; in (Ixv), SEQ ID NO: 6510; in (Ixvi), SEQ ID NO: 6610; in (Ixvii), SEQ ID NO: 6710; in (Ixviii), SEQ ID NO: 6810; in (Ixviii-a), SEQ ID NO: 6830; in (Ixviii-b). SEQ ID NO: 6840; in (Ixviii-c), SEQ ID NO: 6850; in (Ixviii-d), SEQ ID NO: 6860; in (Ixviii-e), SEQ ID NO: 6870; in (Ixviii-f), SEQ ID NO: 6880; in (Ixix), SEQ ID NO: 6910; in (Ixx), SEQ ID NO: 7010; in (Ixx-a), SEQ ID NO: 7030; in (Ixx-b), SEQ ID NO: 7040; in (Ixx-c), SEQ ID NO: 7050; in (Ixx-d), SEQ ID NO: 7060; in (Ixx-e), SEQ ID NO: 7070; in (Ixx-f), SEQ ID NO: 7080; in (Ixxi), SEQ ID NO: 7110; in (Ixxii), SEQ ID NO: 7210; in (Ixxiii), SEQ ID NO: 7310; in (Ixxiv), SEQ ID NO: 7410; in (Ixxv), SEQ ID NO: 7510; in (Ixxvi), SEQ ID NO: 7610; in (Ixxvii), SEQ ID NO: 7710; in (Ixxviii), SEQ ID NO: 7810; or in (Ixxix), SEQ ID NO: 7910; in (Ixxx), SEQ ID NO: 8010; in (Ixxxi), SEQ ID NO: 8110; in (Ixxxii), SEQ ID NO: 8210; in (Ixxxiii), SEQ ID NO: 8310; in (Ixxxiii-a), SEQ ID NO: 8330; in (Ixxxiii-b), SEQ ID NO: 8340; in (Ixxxiii-c), SEQ ID NO: 8350; in (Ixxxiii-d), SEQ ID NO: 8360; in (Ixxxm-e). SEQ ID NO: 8370; in (Ixxxiii-f), SEQ ID NO: 8380; or in (Ixxxiv), SEQ ID NO: 8410.

[0046] In particular embodiments of (B) above, in some cases, amino acid sequence of theVH-1 may comprise or consist of: in (1), SEQ ID NO: 7010; or in (2), SEQ ID NO: 8310.

[0047] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may comprise: (a) an immunoglobulin (Ig)format or a half-antibody variant thereof, optionally an IgG, IgA, IgE, IgD, or IgM format, further optionally an IgG1, IgG2, IgG3, or IgG4 format; (b) an antibody fragment antigenbinding region (Fab) format, a Fab’ format, a F(ab’)2 format, a F(ab’)s format, and / or a variable fragment (Fv) format; (c) a single chain fragment variable region (scFv) format, a tandem scFv format, a diabody format, a triabody format, a tetrabody format, a scFv-Fc format, a scFv-CH format, a minibody format, a scFv-zipper format, a diabody-Fc format, a diabody-CH format, a half-antibody variant of any of the foregoing, and / or a single chain Fab (scFab) format; (d) a heavy chain-only antibody (HCAb) format, ananobody-Fc format, a nanobody-CH format, a single chain nanobody-CH format, a camel Ig format, and / or an IgNAR format, or a single-chain variant of any of the foregoing; and / or (e) a single domain antibody (sdAb) format, a nanobody format, a tandem nanobody format.

[0048] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may comprise the VH-1 and the VL-1, wherein the anti-human CD28 antibody or antigen-binding antibody fragment may comprise or consist of: (a) a heavy chain comprising the VH-1 and a light chain comprising the VL-1, optionally wherein the antibody or antigen-binding antibody fragment: (a- 1 ) consists of said heavy and light chains; (a-2) comprises or consists of an Ig molecule comprising two said heavy chains and two said light chains, or a multimer of said Ig molecule; and / or (a-3) comprises or consists of an IgG, IgA, IgE. IgD, or IgM, optionally an IgG1, IgG2, IgG3, or IgG4; and / or (b) a Fab comprising the VH-1 and the VL-1, a Fab’ comprising the VH-1 and the VL-1 , a F(ab’)2 comprising the VH-1 and the VL-1, a F(ab’)3 comprising the VH-1 and the VL-1, and / or a Fv comprising the VH-1 and the VL-1; (c) a scFv comprising the VH-1 and the VL-1, a tandem scFv comprising the VH-1 and the VL-1, a diabody comprising the VH-1 and the VL-1, a triabody comprising the VH-1 and the VL-1. a tetrabody comprising the VH-1 and the VL-1, a scFv-Fc comprising the VH-1 and the VL-1, a scFv-CH comprising the VH-1 and the VL-1, a minibody comprising the VH-1 and the VL-1, a scFv- zipper comprising the VH-1 and the VL-1, a diabody-Fc comprising the VH-1 and the VL-1, a diabody-CH comprising the VH-1 and the VL-1, and / or a scFab comprising the VH-1 and the VL-1.

[0049] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may comprise the VH-1, wherein the antihuman CD28 antibody or antigen-binding antibody fragment may comprise or consist of: (d) a HCAb comprising the VH-1. a nanobody-Fc comprising the VH-1, a nanobody-CH comprising the VH-1, a camel Ig comprising the VH-1, an IgNAR comprising the VH-1,and / or a single-chain variant of any of the foregoing; and / or (e) a sdAb comprising the VH-1; a nanobody comprising the VH-1 ; and / or a tandem nanobody comprising the VH-1.

[0050] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may: (a) bind to mouse CD28 and / or cynomolgus CD28.

[0051] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may: (b) bind to human CD28 with a KD of < about 1 μM, < about 500 nM, < about 200 nM, < about 100 nM, < about 50 nM, < about 20 nM, < about 10 nM, < about 5 nM, < about 2 nM, < about 1 nM, < about 500 pM, about 1 μM, about 500 nM, about 200 nM, about 100 nM. about 50 nM, about 20 nM, about 10 nM, about 5 nM, about 2 nM. about 1 nM, about 500 pM, about 200 pM, between about 100 nM and 1 nM, between about 50 nM and 1 nM, between about 20 nM and 1 nM, between about 10 nM and 1 nM, between about 5 nM and 1 nM, between about 2 nM and 1 nM, between about 10 nM and 500 pM, between about 5 nM and 500 pM, between about 2 nM and 500 pM, between about InM and 500 pM, between about 1 nM and 200 pM, or between about 500 pM and about 200 pM, at a physiological pH or at pH 7.4, optionally as measured by bio- layer interferometry (BLI), further optionally as performed in Example 3and / or 12.

[0052] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may: (c) bind to human CD28 with a KD of < about 1 μM, < about 500 nM, < about 200 nM, < about 100 nM, < about 50 nM, < about 20 nM, < about 10 nM, < about 5 nM, < about 2 nM, < about 1 nM, about 1 μM, about 500 nM, about 200 nM, about 100 nM, about 50 nM, about 20 nM, about 10 nM, about 5 nM, about 2 nM, or about 1 nM, at an acidic pH or at pH 6.0, optionally as measured by BLI, further optionally as performed in Example 3.

[0053] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may: (d) bind to human CD28 with a lower KD at an acidic pH or at pH 6.0 compared to at a physiological pH or at pH 7.4, optionally by or at least by about 1.5-fold, about 2-fold, about 3-fold, about 4-fold, about 5-fold, about 6-fold, about 7-fold, about 8-fold, about 9-fold, about 10-fold, about 12-fold, about 15-fold, about 20-fold, about 25-fold, about 30-fold, about 35-fold, about 40-fold, about 45-fold, about 50- fold, about 60-fold, about 70-fold, about 80-fold, about 90-fold, about 100-fold, about 200- fold, about 300-fold, about 400-fold, about 500-fold, about 600-fold, about 700-fold, about 800-fold, about 900-fold, or about 1000-fold, optionally as measured by BLI, further optionally as performed in Example 3.

[0054] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may: (e) bind to human CD28 at an acidic pH or at pH 6.0 but does not bind to human CD28 at a physiological pH or at pH 7.4, optionally as measured by BLI, further optionally as performed in Example 3.

[0055] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may: (f) not bind to mouse or murine CD28 or binds to mouse or murine CD28 with a KD of > about 10 nM. > about 20 nM, > about 50 nM, > about 100 nM, > about 200 nM, > about 500 nM, > about 1 μM. about 10 nM, about 20 nM, about 50 nM, about 100 nM, about 200 nM, about 500 nM, or about 1 μM, optionally as measured by BLI, further optionally as performed in Example 3 and / or 12.

[0056] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may: (g) not bind to human CD28 monomer or bind to human CD28 monomer with a KD of > about 1 nM, > about 10 nM, > about 20 nM, > about 50 nM, > about 100 nM, > about 200 nM, > about 500 nM, > about 1 μM, about 1 nM, about 10 nM, about 20 nM, about 50 nM, about 100 nM, about 200 nM, about 500 nM, or about 1 μM, optionally as measured by BLI, further optionally as performed in Example 3 and / or 12.

[0057] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may: (h) bind to human CD28 expression cells, optionally Jurkat cells and / or human CD28-CHO cells, more efficiently compared to one or more of, optionally as measured by flow cytometry, further optionally based on median fluorescence intensity and / or normalized cell binding values, yet further optionally as performed in Example 5 and / or 13.

[0058] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may: (i) display a polyspecificity reagent (PSR) score of: score < 0.1 (clean); 0.10 < score < 0.33 (low), or 0.33 < score < 0.66 (medium), or 0.00 as measured by an PSR assay, optionally as performed in Example 6 and / or 14.

[0059] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may: (j) display a hydrophobic interaction chromatography (HIC) retention time (RT) of: RT < 9.5 minutes, RT < 10.0 minutes, or RT < 10.5 minutes (clean or low), or 10.5 minutes < RT < 11.5 minutes (medium), as measured by HIC, optionally as performed in Example 6 and / or 14.

[0060] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may: (k) display a melting temperature (Tm) of< about 45 °C, < about 50 °C, < about 55 °C, < about 60 °C, < about 65 °C, < about 70 °C, < about 75 °C, < about 80 °C, < about 85 °C, > about 45 °C, > about 50 °C. > about 55 °C, > about 60 °C, > about 65 °C, > about 70 °C, > about 75 °C, > about 80 °C, > about 85 °C, about 45 °C, about 50 °C, about 55 °C, about 60 °C, about 65 °C, about 70 °C, about 75 °C, about 80 °C, or about 85 °C, optionally as measured by differential scanning fluorimetry (DSF), further optionally as performed in Example 6 and / or 14.

[0061] In some embodiments, the anti-human CD28 antibody or antigen-binding antibody fragment according to the present disclosure may: (1) be capable of stimulating a T cell.

[0062] In certain embodiments, such T cell stimulation may be determined by: (1-1) increased expression of CD69. optionally as measured by flow cytometry, further optionally based on an increased mean fluorescence intensity (MFI), yet further optionally by about 5%, by about 10%, about 15%, by about 20%, about 25%, by about 30%, about 35%, by about 40%, about 45%, by about 50%, about 55%, by about 60%, about 65%, by about 70%, about 75%, by about 80%, about 85%, by about 90%, about 95%, by about 100%, by about 150%, by about 200%, by about 250%, by about 300%, by about 350%, by about 400%, by about 450%, or by 500%.

[0063] In certain embodiments, such T cell stimulation may be determined by: (1-2) increased release of IL-2, optionally by or at least by about 1.5-fold, about 2-fold, about 3- fold, about 4-fold, about 5-fold, about 6-fold, about 7-fold, about 8-fold, about 9-fold, about 10-fold, about 12-fold, about 15-fold, about 20-fold, about 25-fold, about 30-fold, about 35- fold, about 40-fold, about 45-fold, or about 50-fold, optionally as measured by an immuno- assay, optionally Enzyme-linked immunosorbent assay (ELISA), optionally by about 5%, by about 10%. about 15%, by about 20%, about 25%, by about 30%, about 35%, by about 40%, about 45%. by about 50%. about 55%, by about 60%. about 65%, by about 70%. about 75%, by about 80%, about 85%, by about 90%, about 95%, by about 100%, by about 150%, by about 200%, by about 250%, by about 300%, by about 350%, by about 400%, by about 450%, or by 500%.

[0064] In certain embodiments, such T cell stimulation may be determined by: (1-3) increased transcriptional activation, optionally as measured using a CD28 Bioassay (Promega, TM633), upon incubation of a T cell with the anti-human CD28 antibody or antigen-binding antibody fragment and optionally with an anti-CD3 antibody, optionally compared to incubation of the T cell without the anti-human CD28 antibody or antigen- binding antibody fragment with or without an anti-CD3 antibody, further optionally as performed in Example 7.

[0065] In one aspect, the disclosure provides multi-specific antibodies. A multi-specific antibody may comprise: (1) a first antigen-binding region (ABR-1) that binds human CD28, wherein the ABR-1 comprises any of the anti-human CD28 antibodies or antigen-binding antibody fragments described above; and (2) a second antigen-binding region (ABR-2) that binds a second antigen.

[0066] In some embodiments, the ABR-2 may comprise: a second heavy chain variable domain (VH-2) comprising a second heavy chain complementarity determining region (CDR) 1 (CDRH1-2), a second heavy chain CDR2 (CDRH2-2), and a second heavy chain CDR3 (CDRH3-2); and / or a second light chain variable domain (VL-2) comprising a second light chain CDR1 (CDRL1-2), a second light chain CDR2 (CDRL2-2), and a second light chain CDR3 (CDRL3-2).

[0067] In some embodiments, the second antigen may optionally be the same as or different from CD28 (or human CD28). If different, the first specificity and the second specificity7of the multi-specific antibody may be an epitope in CD28 and another epitope in CD28, respectively.

[0068] In some embodiments, the multi-specific antibody may be bispecific, trispecific, tetraspecific, or pentaspecific, or may have more than five specificities.

[0069] In some embodiments, the multi-specific antibody may be bivalent, trivalent, tetravalent, pentavalent, or may have a higher valency. In some embodiments, the multi- specific antibody may bind to CD28 monovalently, bivalently, trivalently, tetravalently, or pentavalently, or a with a higher valency. In some embodiments, the multi-specific antibody may bind to the second antigen monovalently, bivalently, trivalently, tetravalently, or pentavalently , or a with a higher valency.

[0070] In some embodiments, the second antigen may be or may comprise: (a) human cluster of differentiation 3 (CD3); (b) a cancer antigen, optionally a tumor-specific antigen (TSA) or a tumor-associated antigen (TAA); (c) human CD28; (d) any one of the antigens selected from those listed in Table 3; and / or (c) any one of the cancer antigens, optionally any one of the TSAs or any one of the TAAs, selected from those listed in Table 3.

[0071] In certain embodiments, the second antigen may be or may comprise CD3.

[0072] In certain embodiments, the ABR-2 may comprise the VH-2 and / or VL-2 and may comprise a CDR amino acid sequence according to any one of those listed in Table 4B.

[0073] In certain embodiments, in said VH-2 in the ABR-2: (a) the amino acid sequence of the CDRH1-2 may comprise or consist of: a heavy chain complementarity determining region 1 (CDRH1) amino acid sequence contained in any one of the heavy chain variabledomain (VH) amino acid sequences listed in Table 4A; and / or any one of the CDRH1 amino acid sequences listed in Table 4B; (b) the amino acid sequence of the CDRH2-2 may comprise or consist of: a heavy chain complementarity determining region 2 (CDRH2) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 4A; and / or any one of the CDRH2 amino acid sequences listed in Table 4B; and / or (c) the amino acid sequence of the CDRH3-2 may comprise or consist of: a heavy chain complementarity determining region 3 (CDRH3) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 4A: and / or any one of the CDRH3 amino acid sequences listed in Table 4B, and / or

[0074] In certain embodiments, in said VL-2 in the ABR-2 : (d) the amino acid sequence of the CDRL1-2 may comprise or consist of: a light chain complementarity determining region 1 (CDRL1) amino acid sequence contained in any one of the light chain variable domain (VL) amino acid sequences listed in Table 4A; and / or any one of the CDRL1 amino acid sequences listed in Table 4B; (c) the amino acid sequence of the CDRL2-2 may comprise or consist of: a light chain complementarity determining region 2 (CDRL2) contained in any one of the VL amino acid sequences listed in Table 4A; and / or any one of the CDRL2 amino acid sequences listed in Table 4B; and / or (f) the amino acid sequence of the CDRL3-2 may comprise or consist of: a light chain complementarity determining region 3 (CDRL3) that contained in any one of the VL amino acid sequences listed in Table 4A; and / or any one of the CDRL3 amino acid sequences listed in Table 4B.

[0075] In some embodiments, in a multi-specific antibody according to the present disclosure, the ABR-2 may comprise: (a) a set of heavy chain CDR amino acid sequences of a first anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E; (b) a set of light chain CDR amino acid sequences of a first anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E; (c) a set of heavy and light chain CDR amino acid sequences of a first anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E; and / or (d) a set of heavy chain CDR amino acid sequences of a first anti-CD3 antibody- selected from the antibodies listed in Tables 4A-4E; and a set of light chain CDR amino acid sequences of a second anti-CD3 antibody selected from the antibodies listed in Tables 4A- 4E. The first anti-CD3 antibody and the second anti-CD3 antibody may or may not be the same antibody. In certain embodiments, the ABR-2 may comprise: (a) a set of heavy chain CDR amino acid sequences of ADI-26906 or ADI-26921. In certain embodiments, the ABR- 2 may comprise: (b) a set of light chain CDR amino acid sequences of ADI-26906 or ADI- 26921. In certain embodiments, the ABR-2 may comprise: (c) a set of heavy and light chainCDR amino acid sequences of ADI-26906 or ADI-26921. In certain embodiments, the ABR- 1 and the ABR-2 may have the same VL sequences (i.e., common VL). In particular embodiments, the ABR-1 may comprise a set of heavy and light chain CDR amino acid sequences of (as contained in the VH and VL of ) any one of Ab Nos. 59-69 and the ABR-2 may comprise a set of heavy and light chain CDR amino acid sequences of (as contained in the VH and VL of ) ADI-26921. In particular embodiments, the ABR-1 may comprise a set of heavy and light chain CDR amino acid sequences of (as contained in the VH and VL of ) Ab No. 61 or 68 and the ABR-2 may comprise a set of heavy and light chain CDR amino acid sequences of (as contained in the VH and VL of ) ADI-26921.

[0076] In some embodiments, in a multi-specific antibody according to the present disclosure which comprises the ABR-2 comprising the VH-2 and the VL-2: (1) the amino acid sequences of the CDRH1-2, the CDRH2-2, and the CDRH3-2 in the VH-2 of the ABR-2 comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, and a CDRH3, respectively, contained in the VH of a first anti-CD3 antibody; and (2) the amino acid sequences of the CDRL1-2, the CDRL2-2, and the CDRL3-2 in the VL-2 of the ABR-2 comprise or consist of the amino acid sequences of a CDRL1, a CDRL2. and a CDRL3, respectively, contained in the VL of said first anti-CD3 antibody, wherein said first anti-CD3 antibody is one selected from the antibodies listed in Tables 4A-4E. In certain embodiments, the first anti-CD3 antibody may be ADI-26906 or ADI-26921. In certain embodiments, the ABR-1 and the ABR-2 may have the same VL sequences (i.e., common VL). In particular embodiments, the VL-1 and the VL-2 may comprise a set of light chain CDR amino acid sequences of (as contained in the VL of) ADI-26921. In some cases, the ABR-1 may comprise a set of heavy and light chain CDR amino acid sequences of (as contained in the VH and VL of ) any one of Ab Nos. 59-69 and the ABR-2 may comprise a set of heavy and light chain CDR amino acid sequences of (as contained in the VH and VL of ) ADI-26921. In particular cases, the ABR-1 may comprise a set of heavy and light chain CDR amino acid sequences of (as contained in the VH and VL of ) Ab No. 61 or 68 and the ABR-2 may comprise a set of heavy and light chain CDR amino acid sequences of (as contained in the VH and VL of) ADI-26921.

[0077] In some embodiments, the ABR-2 may comprise the VH-2 the VL-2, and wherein the amino acid sequences of the CDRH1-2, the CDRH2-2, the CDRH3-2, the CDRL1-2, the CDRL2-2, and the CDRL3-2 comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, a CDRH3, CDRL1, a CDRL2. and a CDRL3 of a first anti-CD3 antibody, wherein said first anti-CD3 antibody is one selected from the antibodies listed in Tables 4A-4E.

[0078] In certain embodiments, the first anti-CD3 antibody may be ADI-26906 or ADI- 26921.

[0079] In certain embodiments, the multi-specific antibody may comprise the VH-2 and / or the VL-2, wherein: the amino acid sequence of the VH-2 comprises or consists of an amino acid sequence selected from any one of the VH amino acid sequences listed in Table 4 A or a variant thereof having at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%. 98%. or 99% sequence identity; and / or the amino acid sequence of the VL-2 comprises or consists of an amino acid sequence selected from any one of the VL amino acid sequences listed in Table 4A or a variant thereof having at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity'.

[0080] In certain embodiments, the amino acid sequences of the VH-2 and the VL-2 may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity' to the amino acid sequences of the VH and the VL, respectively, of said first anti-CD3 antibody. In particular embodiments, the first anti-CD3 antibody may be ADI-26906 or ADI-26921.

[0081] In particular embodiments, the ABR-2 may comprise a variable domain pair according to any of those listed in Table 4A. In some cases, the ABR-2 may comprise the VH and the VL of ADI-26906 or ADI-26921. In certain cases, the ABR-1 may comprise a VH and VL pair of any one of Ab Nos. 59-69 and the ABR-2 may comprise a VH and VL pair of ADI-26921. In particular cases, the ABR-1 may comprise a VH and VL pair of Ab No. 61 or 68 and the ABR-2 may comprise a VH and VL pair of ADI-26921.

[0082]

[0083] In particular embodiments, in the ABR-2, the amino acid sequences of the VH-2 and the VL-2 may comprise or consist of the amino acid sequences of the VH and the VL, respectively, of said first anti-CD3 antibody.

[0084] In certain embodiments, in the any of the multi-specific antibodies described above: (1) the ABR-1 may comprise: (a) a heavy chain comprising the VH-1 and a light chain comprising the VL-1, optionally wherein the ABR-1: (a-1) consists of said heavy and light chains; (a-2) comprises or consists of an Ig molecule comprising two said heavy chains and two said light chains, or a multimer of said Ig molecule; and / or (a-3) comprises or consists of an IgG. IgA, IgE, IgD, or IgM, optionally an IgG1, IgG2, IgG3, or IgG4; (b) a Fab comprising the VH-1 and the VL-1, a Fab’ comprising the VH-1 and the VL-1, a F(abT)2 comprising the VH-1 and the VL-1, a F(ab’)? comprising the VH-1 and the VL-1, and / or a Fvcomprising the VH-1 and the VL-1; (c) a scFv comprising the VH-1 and the VL-1, a tandem scFv comprising the VH-1 and the VL-1, a diabody comprising the VH-1 and the VL-1, a triabody comprising the VH-1 and the VL-1, a tetrabody comprising the VH-1 and the VL-1, a scFv-Fc comprising the VH-1 and the VL-1, a scFv-CH comprising the VH-1 and the VL-1, a minibody comprising the VH-1 and the VL-1, a scFv-zipper comprising the VH-1 and the VL-1, a diabody-Fc comprising the VH-1 and the VL-1, a diabody-CH comprising the VH-1 and the VL-1; and / or a scFab comprising the VH-1 and the VL-1; (d) a HCAb comprising the VH-1, a nanobody-Fc comprising the VH-1, a nanobody-CH comprising the VH-1, a camel Ig comprising the VH-1, an IgNAR comprising the VH-1, and / or a singlechain variant of any of the foregoing; and / or (e) a sdAb comprising the VH-1, a nanobody comprising the VH-1, and / or a tandem nanobody comprising the VH-1.

[0085] In certain embodiments, in the any of the multi-specific antibodies described above: (2) the ABR-2 comprises: (a) a heavy chain comprising the VH-2 and a light chain comprising the VL-2, optionally wherein the ABR-2: (a-1) consists of said heavy and light chains; (a-2) comprises or consists of an Ig molecule comprising two said heavy chains and two said light chains, or a multimer of said Ig molecule; and / or (a-3) comprises or consists of an IgG, IgA, IgE, IgD, or IgM, optionally an IgG1, IgG2, IgG3, or IgG4; (b) a Fab comprising the VH-2 and the VL-2, a Fab’ comprising the VH-2 and the VL-2, a F(ab')2 comprising the VH-2 and the VL-2, a F(ab’)3 comprising the VH-2 and the VL-2, and / or a Fv comprising the VH-2 and the VL-2; (c) a scFv comprising the VH-2 and the VL-2. a tandem scFv comprising t the VH-2 and the VL-2, a diabody comprising the VH-2 and the VL-2, a triabody comprising the VH-2 and the VL-2, a tetrabody comprising the VH-2 and the VL-2, a scFv-Fc comprising the VH-2 and the VL-2. a scFv-CH comprising the VH-2 and the VL-2, a minibody comprising the VH-2 and the VL-2, a scFv-zipper comprising the VH-2 and the VL-2, a diabody-Fc comprising the VH-2 and the VL-2, a diabody-CH comprising the VH-2 and the VL-2, and / or a scFab comprising the VH-2 and the VL-2; (d) a HCAb comprising the VH-2, a nanobody-Fc comprising the VH-2, a nanobody-CH comprising the VH-2, a camel Ig comprising the VH-2, an IgNAR comprising the VH-2. and / or a single- chain variant of any of the foregoing; and / or (e) a sdAb comprising the VH-2, a nanobody comprising the VH-2, and / or a tandem nanobody comprising the VH-2.

[0086] In some cases, the ABR-1 and the ABR-2 may be associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker. In some cases, the ABR-1 and the ABR-2 may be associated with or linked to each other via oneor more disulfide bonds. In some cases, the ABR-1 and the ABR-2 may be directly associated with or linked to each other.

[0087] In particular embodiments, the multi-specific antibody may comprise a structure depicted in any one of FIGS. 1-6, optionally any one of FIGS. 2-6, further optionally any one of FIGS. 2A-2M, 4A-4C, 5A-5N, and 6. In particular cases, the multi-specific antibodymay comprise the boxed structure of FIG. 2G.

[0088] In some cases, in any of the multi-specific antibodies described above: (1) the ABR-1 may comprise: at least one Ig constant domain, optionally one or more of a heavy chain constant domain 1 (CH1), a heavy chain constant domain 2 (CH2), a heavy chain constant domain 3 (CH3), and / or a light chain constant domain (CL); and / or a fragment crystallizable (Fc) region, optionally wherein: (a) the CH1, CH2, and / or the CH3 may be individually of an IgG, IgA, IgE, IgD, or IgM class, optionally of an IgG1, IgG2, IgG3, and / or IgG4 subclass; (b) the CL may be of a kappa isotype (CLK) or a lambda isotype (CLk): and / or (c) the Fc region may be of an IgG, IgA, IgE, IgD, or IgM class, optionally of an IgG1, IgG2. IgG3, and / or IgG4 subclass.

[0089] In some cases, in any of the multi-specific antibodies described above: (2) the ABR-2 may comprise: at least one Ig constant domain, optionally one or more of a CH1, a CH2, a CH3, and / or a CL; and / or a Fc region, optionally wherein: (a) the CH1, CH2, and / or the CH3 may be individually of an IgG, IgA, IgE, IgD, or IgM class, optionally of an IgG1, IgG2, IgG3, and / or IgG4 subclass; (b) the CL is a CLK or a CLk; and / or (c) the Fc region may be of an IgG, IgA, IgE, IgD, or IgM class, optionally of an IgG1, IgG2, IgG3, and / or IgG4 subclass.

[0090] In some cases, the multi-specific antibody may comprise common light chains, and / or the VL-1 and the VL-2 may have the same or essentially the same amino acid sequences. In certain cases, the second antigen is human CD3 and the amino acid sequences of the VL-1 and the VL-2 individually have at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity- to the amino acid sequences of the VL of ADI-26921 (SEQ ID NO: 13270). In particular cases, the amino acid sequences of the VL- I and the VL-2 individually comprise or consist of SEQ ID NO: 1327.

[0091] In some cases, the multi-specific antibody may comprise one or more of the following: (4-i) a heavy chain constant region (CH), optionally a CH1, which is engineered to promote pairing with a CLK over a CLk, optionally wherein the CH1 engineering is one of those described in WO2021067404; (4-ii) a CH, optionally a CH1, which is engineered to promote pairing with a CLk over a CLK, optionally wherein the CH1 engineering is one ofthose described in WO2021067404; and / or (4-iii) a CH. optionally a CH1, which is engineered to promote pairing with an engineered CL comprised in the multi-specific antibody over another CL, optionally wherein the combination of the CH engineering and the CL engineering is one of those described in WO2022150787; and / or (4-iv) at least two CHs having different amino acid sequences, optionally at least two CH3s having different amino acid sequences, which are engineered to promote heteromeric paring between the two CHs over homomeric pairing, optionally wherein the CH3 engineering is one of those described in WO2022150785.

[0092] In some embodiments, any of the multi-specific antibodies described above may comprise a third antigen-binding region (ABR-3) that binds to a third antigen. In some embodiments, any of the multi-specific antibodies described above may comprise a ABR-3 comprising: a third heavy chain variable domain (VH-3) comprising a third heavy chain complementarity determining region (CDR) 1 (CDRH1-3), a third heavy chain CDR2 (CDRH2-3), and a third heavy chain CDR3 (CDRH3-3); and / or a third light chain variable domain (VL-3) comprising a third light chain CDR1 (CDRL1-3), a third light chain CDR2 (CDRL2-3), and a third light chain CDR3 (CDRL3-3).

[0093] In some embodiments, the third antigen may optionally be the same as or different from CD28 (or human CD28) and / or the second antigen. If the third antigen is CD28, the ABR-1 and the ABR-3 may bind to the same epitope of CD28 or bind to different epitopes of CD28. If the third antigen is the same as the second antigen, the ABR-2 and the ABR-3 may bind to the same epitope of the second antigen or bind to different epitopes of the second antigen.

[0094] In some embodiments, the third antigen may be or may comprise: (a) human CD3; (b) a cancer antigen, optionally a TSA or a TAA; (c) human CD28; (d) any one of the antigens selected from those listed in Table 3; and / or (e) any one of the cancer antigens, optionally any one of the TSAs or any one of the TAAs, selected from those listed in Table 3.

[0095] In some embodiments, the third antigen may be or may comprise CD3.

[0096] In certain embodiments, the ABR-3 may comprise the VH-3 and / or VL-3 and may comprise a CDR amino acid sequence according to any one of those listed in Table 4B.

[0097] In certain embodiments, the ABR-3 may comprise said VH-3, wherein: (a) the amino acid sequence of the CDRH1-3 comprises or consists of: a heavy chain complementarity determining region 1 (CDRH1) amino acid sequence contained in any one of the heavy chain variable domain (VH) amino acid sequences listed in Table 4A; and / orany one of the CDRH1 amino acid sequences listed in Table 4B; (b) the amino acid sequence of the CDRH2-3 comprises or consists of a heavy chain complementarity determining region 2 (CDRH2) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 4A; and / or any one of the CDRH2 amino acid sequences listed in Table 4B; and / or (c) the amino acid sequence of the CDRH3-3 comprises or consists of: a heavy chain complementarity determining region 3 (CDRH3) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 4A; and / or any one of the CDRH3 amino acid sequences listed in Table 4B.

[0098] In certain embodiments, the ABR-3 may comprise said VL-3, wherein: (d) the amino acid sequence of the CDRL1-3 comprises or consists of: alight chain complementarity determining region 1 (CDRL1) amino acid sequence contained in any one of the light chain variable domain (VL) amino acid sequences listed in Table 4A; and / or any one of the CDRL1 amino acid sequences listed in Table 4B; (c) the amino acid sequence of the CDRL2-3 comprises or consists of: a light chain complementarity determining region 2 (CDRL2) contained in any one of the VL amino acid sequences listed in Table 4A; and / or any one of the CDRL2 amino acid sequences listed in Table 4B; and / or (f) the amino acid sequence of the CDRL3-3 comprises or consists of: a light chain complementarity determining region 3 (CDRL3) that contained in any one of the VL amino acid sequences listed in Table 4A; and / or any one of the CDRL3 amino acid sequences listed in Table 4B.

[0099] In some embodiments, the ABR-3 may comprise: (a) a set of heavy chain CDR amino acid sequences of a third anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E; (b) a set of light chain CDR amino acid sequences of a third anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E; (c) a set of heavy and light chain CDR amino acid sequences of a third anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E; and / or (d) a set of heavy chain CDR amino acid sequences of a third anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E; and a set of light chain CDR amino acid sequences of a fourth anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E. In certain embodiments, the third anti-CD3 antibody may be ADI- 26906 or ADI-26921. In (d). the third and / or fourth anti-CD3 antibody may be ADI-26906 or ADI-26921. In (d), in the third anti-CD3 antibody and the fourth anti-CD3 antibody may or may not be the same antibody.

[0100] In particular embodiments, the ABR-3 may comprise a set of heavy chain CDR amino acid sequences contained in the VH of ADI-26906 or ADI-26921. In some cases, the ABR-3 may comprise a set of light chain CDR amino acid sequences contained in the VL ofADI-26906 or ADI-26921. In particular embodiments, the ABR-3 may comprise a set of heavy and light chain CDR amino acid sequences contained in the VH and VL of ADI-26906 or in the VH and VL of ADI-26921. In some cases, the ABR-1 may comprise a set of heavy and light chain CDR amino acid sequences contained in the VH and VL of any one of Ab Nos. 59-69 and the ABR-3 may comprise a set of heavy and light chain CDR amino acid sequences contained in the VH and VL of ADI-26921. In particular cases, the ABR-1 may comprise a set of heavy and light chain CDR amino acid sequences contained in the VH and VL of Ab No. 61 or 68 and the ABR-3 may comprise a set of heavy and light chain CDR amino acid sequences contained in the VH and VL of ADI-26921.

[0101] In some embodiments, in the ABR-3 may comprise the VH-3 and the VL-3, wherein: (1) the amino acid sequences of the CDRH1-3, the CDRH2-3, and the CDRH3-3 of the VH-3 of the ABR-3 may comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, and a CDRH3, respectively, contained in the VH of a third anti-CD3 antibody; and (2) the amino acid sequences of the CDRL1-3, the CDRL2-3, and the CDRL3-3 of the VL-3 of ABR-3 may comprise or consist of the amino acid sequences of a CDRL1, a CDRL2, and a CDRL3, respectively, contained in the VL of said third anti-CD3 antibody, wherein said third anti-CD3 antibody is one selected from the antibodies listed in Tables 4A-4E. In particular embodiments, the third anti-CD3 antibody may be ADI-26906 or ADI-26921.

[0102] In some embodiments, in the ABR-3: the amino acid sequences of the CDRH1-3, the CDRH2-3, the CDRH3-3, the CDRL1-3, the CDRL2-3. and the CDRL3-3 of the VL-3 and the VH-3 of the ABR-3 may comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, a CDRH3, CDRL1, a CDRL2, and a CDRL3 of a third anti-CD3 antibody, wherein said third anti-CD3 antibody is one selected from the antibodies listed in Tables 4A-4E. In particular embodiments, the third anti-CD3 antibody may be ADI-26906 or ADI-26921.

[0103] In certain embodiments: the amino acid sequence of the VH-3 of the ABR-3 may comprise or consist of an amino acid sequence selected from any one of the VH amino acid sequences listed in Table 4A or a variant thereof having at least about 80%, 85%, 90%, 91%, 92%. 93%. 94%. 95%. 96%. 97%. 98%. or 99% sequence identity; and / or the amino acid sequence of the VL-3 of the ABR-3 may comprise or consist of an amino acid sequence selected from any one of the VL amino acid sequences listed in Table 4A or a variant thereof having at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity.

[0104] In certain embodiments: the amino acid sequences of the VH-3 and the VL-3 of the ABR-3 may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to the amino acid sequences of the VH and the VL, respectively, of said third anti-CD3 antibody.

[0105] In particular embodiments, the third anti-CD3 antibody may be ADI-26906 or ADI-26921

[0106] In particular embodiments: the ABR3 may comprise a variable domain pair according to any of those listed in Table 4A. In some cases, the ABR3 may comprise a variable domain pair of ADI-26906 or ADI-26921. In certain cases, the ABR-1 may comprise a VH and VL pair of any one of Ab Nos. 59-69 and the ABR-3 may comprise a VH and VL pair of ADI-26921. In particular cases, the ABR-1 may comprise a VH and VL pair of Ab No. 61 or 68 and the ABR-3 may comprise a VH and VL pair of ADI-26921.

[0107] In particular embodiments: the amino acid sequences of the VH-3 and the VL-3 may comprise or consist of the amino acid sequences of the VH and the VL, respectively, of said third anti-CD3 antibody.

[0108] In certain embodiments, in the any of the multi-specific antibodies described above: the ABR-3 may comprise: (a) a heavy chain comprising said VH-3 and a light chain comprising said VL-3. optionally wherein the ABR-3: (a- 1) consists of said heavy and light chains; (a-2) comprises or consists of an Ig molecule comprising two said heavy chains and two said light chains, or a multimer of said Ig molecule; and / or (a-3) comprises or consists of an IgG. IgA, IgE, IgD, or IgM, optionally an IgG1, IgG2, IgG3, or IgG4; (b) a Fab comprising the VH-3 and the VL-3, a Fab’ comprising the VH-3 and the VL-3, a F(ab’)2 comprising the VH-3 and the VL-3, a F(ab’)s comprising the VH-3 and the VL-3, and / or a Fv comprising the VH-3 and the VL-3; (c) a scFv comprising the VH-3 and the VL-3, a tandem scFv comprising the VH-3 and the VL-3, a diabody comprising the VH-3 and the VL-3, a triabody comprising the VH-3 and the VL-3, a tetrabody comprising the VH-3 and the VL-3, a scFv-Fc comprising the VH-3 and the VL-3. a scFv-CH comprising the VH-3 and the VL- 3, a minibody comprising the VH-3 and the VL-3, a scFv-zipper comprising the VH-3 and the VL-3, a diabody-Fc comprising the VH-3 and the VL-3, a diabody-CH comprising the VH-3 and the VL-3, and / or a scFab comprising the VH-3 and the VL-3; (d) a HCAb comprising the VH-3, ananobody-Fc comprising the VH-3, ananobody-CH comprising the VH-3, a camel Ig comprising the VH-3, an IgNAR comprising the VH-3, and / or a single-chain variant of any of the foregoing; and / or (e) a sdAb comprising the VH-3, a nanobody comprising the VH-3, and / or a tandem nanobody comprising the VH-3.

[0109] In some cases, (f) the ABR-1 and the ABR-2 may be associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds. In some cases, (g) the ABR-1 and the ABR-3 are associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds. In some cases, (h) the ABR-2 and the ABR-3 are associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds.

[0110] In particular embodiments, the multi-specific antibody may comprise a structure depicted in any one of FIGS. 1-6, optionally any one of FIGS. 2-6. further optionally any one of FIGS. 3A-3B, 4A-4C, 5A-5N, and 6. In particular cases, the multi-specific antibody may comprise the boxed structure of FIG. 2G.[OHl] In some cases, in any of the multi-specific antibodies described above: (1) the ABR-3 may comprise: at least one Ig constant domain, optionally one or more of a CH1. a CH2. a CH3. and / or a CL; and / or a Fc region, optionally wherein: (a) the CH1. CH2. and / or the CH3 is / are individually of an IgG, IgA, IgE, IgD, or IgM class, optionally of an IgG1, IgG2, IgG3, and / or IgG4 subclass; (b) the CL is a CLK or a CLX; and / or (c) the Fc region is of an IgG, IgA, IgE, IgD, or IgM class, optionally of an IgG1, IgG2, IgG3, and / or IgG4 subclass.

[0112] In some cases, in any of the multi-specific antibodies described above: (2) the multi-specific antibody may comprise common light chains and / or the VL-1 and the VL-2 have the same or essentially the same amino acid sequences and / or the VL-1 and the VL-3 have the same or essentially the same amino acid sequences and / or the VL-2 and the VL-3 have the same or essentially the same amino acid sequences.

[0113] In particular cases, (i) the second antigen may be human CD3 and the amino acid sequences of the VL-1 and the VL-2 may individually have at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%. 98%. or 99% sequence identity to the amino acid sequences of the VL of ADI-26921 (SEQ ID NO: 13270) or comprise or consist of SEQ ID NO: 13270. In particular cases, (ii) the third antigen may be human CD3 and the amino acid sequences of the VL-1 and the VL-3 may individually have at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity' to the amino acid sequences of the VL of ADI-26921 (SEQ ID NO: 13270) or comprise or consist of SEQ ID NO: 13270.

[0114] In some cases, in any of the multi-specific antibodies described above: (3) the multi-specific antibody may comprise one or more of the following: (3-i) a heavy chain constant region (CH), optionally a CH1, which is engineered to promote pairing with a CLK over a CLλ , optionally wherein the CH1 engineering is one of those described in WO2021067404; (3-ii) a CH, optionally a CH1, which is engineered to promote pairing with a CLλ over a CLκ, optionally wherein the CH1 engineering is one of those described in WO2021067404; and / or (3-iii) a CH, optionally a CH1. which is engineered to promote pairing with an engineered CL comprised in the multi-specific antibody over another CL, optionally wherein the combination of the CH engineering and the CL engineering is one of those described in WO2022150787; and / or (3-iv) two CHs having different amino acid sequences, optionally two CH3s having different amino acid sequences, which are engineered to promote heteromeric paring between the two CHs over homomeric pairing, optionally wherein the CH3 engineering is one of those described in WO2022150785.

[0115] In some embodiments, any of the multi-specific antibodies described above may comprise a fourth antigen-binding region (ABR-4) that binds to a fourth antigen. In some embodiments, any of the multi-specific antibodies described above may comprise a ABR-4 comprising: a fourth heavy chain variable domain (VH-4) comprising a fourth heavy chain complementarity determining region (CDR) 1 (CDRH1-4), a fourth heavy chain CDR2 (CDRH2-4), and a fourth heavy chain CDR3 (CDRH3-4); and / or a fourth light chain variable domain (VL-4) comprising a fourth light chain CDR1 (CDRL1-4), a fourth light chain CDR2 (CDRL2-4), and a fourth light chain CDR3 (CDRL3-4).

[0116] In some embodiments, the fourth antigen may optionally be the same as or different from CD28 (or human CD28), the second antigen, and / or the third antigen. If the fourth antigen is CD28, the ABR-1 and the ABR-4 may bind to the same epitope of CD28 or bind to different epitopes of CD28. If the fourth antigen is the same as the second antigen, the ABR-2 and the ABR-4 may bind to the same epitope of the second antigen or bind to different epitopes of the second antigen. If the fourth antigen is the same as the third antigen, the ABR-3 and the ABR-4 may bind to the same epitope of the third antigen or bind to different epitopes of the third antigen.

[0117] In some embodiments, the fourth antigen may comprise or may be: (a) human cluster of differentiation 3 (CD3); (b) a cancer antigen, optionally a TSA or a TAA; (c) human CD28; (d) any one of the antigens selected from those listed in Table 3; and / or (e) any one of the cancer antigens, optionally any one of the TSAs or any one of the TAAs, selected from those listed in Table 3.

[0118] In some embodiments, the fourth antigen may comprise or may be: CD3.

[0119] In certain embodiments, the ABR-4 may comprise the VH-4 and / or VL-4 and may comprise a CDR amino acid sequence according to any one of those listed in Table 4B.

[0120] In certain embodiments, the ABR-4 may comprise said VH-4, wherein: (a) the amino acid sequence of the CDRH1-4 comprises or consists of: a heavy chain complementarity determining region 1 (CDRH1) amino acid sequence contained in any one of the heavy chain variable domain (VH) ammo acid sequences listed in Table 4A; and / or any one of the CDRH1 amino acid sequences listed in Table 4B; (b) the amino acid sequence of the CDRH2-4 comprises or consists of: a heavy chain complementarity determining region 2 (CDRH2) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 4A; and / or any one of the CDRH2 amino acid sequences listed in Table 4B; and / or (c) the amino acid sequence of the CDRH3-4 comprises or consists of: a heavy chain complementarity determining region 3 (CDRH3) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 4A; and / or any one of the CDRH3 amino acid sequences listed in Table 4B. and / or

[0121] In certain embodiments, the ABR-4 may comprise said VL-4, wherein: (d) the amino acid sequence of the CDRL1-4 comprises or consists of: a light chain complementarity determining region 1 (CDRL1) amino acid sequence contained in any one of the light chain variable domain (VL) amino acid sequences listed in Table 4A; and / or any one of the CDRL1 amino acid sequences listed in Table 4B; (c) the amino acid sequence of the CDRL2-4 comprises or consists of: a light chain complementarity determining region 2 (CDRL2) contained in any one of the VL amino acid sequences listed in Table 4A; and / or any one of the CDRL2 amino acid sequences listed in Table 4B; and / or (f) the amino acid sequence of the CDRL3-4 comprises or consists of: a light chain complementarity determining region 3 (CDRL3) that contained in any one of the VL amino acid sequences listed in Table 4A; and / or any one of the CDRL3 amino acid sequences listed in Table 4B.

[0122] In certain embodiments, the ABR-4 may comprise: (a) a set of heavy chain CDR amino acid sequences of a fifth anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E; (b) a set of light chain CDR amino acid sequences of a fifth anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E; (c) a set of heavy and light chain CDR amino acid sequences of a fifth anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E; and / or (d) a set of heavy chain CDR amino acid sequences of a fifth anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E; and a set of light chain CDR amino acid sequences of a sixth anti-CD3 antibody selected from the antibodieslisted in Table 4A-4E. In certain embodiments, the fifth anti-CD3 antibody may be ADI- 26906 or ADI-26921. In (d). the fifth and / or sixth anti-CD3 antibody may be ADI-26906 or ADI-26921. In (d), the fifth anti-CD3 antibody and the sixth anti-CD3 antibody may or may not be the same antibody.

[0123] In particular embodiments, the ABR-4 may comprise a set of heavy chain CDR amino acid sequences contained in the VH of ADI-26906 or ADI-26921. In some cases, the ABR-4 may comprise a set of light chain CDR amino acid sequences contained in the VL of ADI-26906 or ADI-26921. In particular embodiments, the ABR-4 may comprise a set of heavy and light chain CDR amino acid sequences contained in the VH and VL of ADI-26906 or in the VH and VL of ADI-26921. In some cases, the ABR-1 may comprise a set of heavy and light chain CDR amino acid sequences contained in the VH and VL of any one of Ab Nos. 59-69 and the ABR-4 may comprise a set of heavy and light chain CDR amino acid sequences contained in the VH and VL of ADI-26921. In particular cases, the ABR-1 may comprise a set of heavy and light chain CDR amino acid sequences contained in the VH and VL of Ab No. 61 or 68 and the ABR-4 may comprise a set of heavy and light chain CDR amino acid sequences contained in the VH and VL of ADI-26921.

[0124] In some embodiments, the ABR-4 may comprise: (1) the amino acid sequences of the CDRH1-4, the CDRH2-4, and the CDRH3-4 of the VH-4 of the ABR-4 comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, and a CDRH3, respectively, contained in the VH of a fifth anti-CD3 antibody; and (2) the amino acid sequences of the CDRL1-4, the CDRL2-4, and the CDRL3-4 of the VL-4 of the ABR-4 comprise or consist of the amino acid sequences of a CDRL1, a CDRL2, and a CDRL3, respectively, contained in the VL of said fifth anti-CD3 antibody, wherein said fifth anti-CD3 antibody is one selected from the antibodies listed in Tables 4A-4E. In certain embodiments, the fifth anti-CD3 antibody may be ADI-26906 or ADI-26921.

[0125] In some embodiments, in the ABR-4: the amino acid sequences of the CDRH1-4, the CDRH2-4, the CDRH3-4, the CDRL1-4, the CDRL2-4, and the CDRL3-4 of the VH-4 and VL-4 of the ABR-4 may comprise or consist of the amino acid sequences of a CDRH1, a CDRH2. a CDRH3, CDRL1, a CDRL2. and a CDRL3 of a fifth anti-CD3 antibody, wherein said fifth anti-CD3 antibody is one selected from the antibodies listed in Tables 4A-4E.

[0126] In certain embodiments: the amino acid sequence of said VH-4 may comprise or consist of an amino acid sequence selected from any one of the VH amino acid sequences listed in Table 4A or a variant thereof having at least about 80%. 85%. 90%. 91%. 92%. 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity; and / or the amino acid sequenceof said VL-4 may comprise or consist of an amino acid sequence selected from any one of the VL amino acid sequences listed in Table 4A or a variant thereof having at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity.

[0127] In certain embodiments: the amino acid sequences of said VH-4 and the VL-4 may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%. at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%. at least about 98%. at least or at least about 99% sequence identity to the amino acid sequences of the VH and the VL, respectively, of said fifth anti-CD3 antibody.

[0128] In particular embodiments, the fifth anti-CD3 antibody may be ADI-26906 or ADI-26921.

[0129] In particular embodiments, the ABR-4 may comprise a variable domain pair according to any of those listed in Table 4A. In some cases, the ABR-4 may comprise the VH and the VL of ADI-26906 or ADI-26921. In some cases, the ABR-1 may comprise a VH and VL pair of any one of Ab Nos. 59-69 and the ABR-4 may comprise a VH and VL pair of ADI-26921. In particular cases, the ABR-1 may comprise a VH and VL pair of Ab No. 61 or 68 and the ABR-4 may comprise a VH and VL pair of ADI-26921.

[0130] In particular embodiments, the amino acid sequences of the VH-4 and the VL-4 may comprise or consist of the amino acid sequences of the VH and the VL, respectively, of said fifth anti-CD3 antibody.

[0131] In some embodiments, said ABR-4 comprises: (a) a heavy chain comprising the VH-4 and a light chain comprising the VL-4, optionally wherein the antibody or antigenbinding antibody fragment: (a-1) consists of said heavy and light chains; (a-2) comprises or consists of an Ig molecule comprising two said heavy chains and two said light chains, or a multimer of said Ig molecule; and / or (a-3) comprises or consists of an IgG. IgA, IgE, IgD, or IgM, optionally an IgG1, IgG2, IgG3, or IgG4; (b) a Fab comprising the VH-4 and the VL-4, a Fab’ comprising the VH-4 and the VL-4, a F(ab’)2 comprising the VH-4 and the VL-4, a F(ab’)s comprising the VH-4 and the VL-4, and / or a Fv comprising the VH-4 and the VL-4; (c) a scFv comprising the VH-4 and the VL-4, a tandem scFv comprising the VH-4 and the VL-4, a diabody comprising the VH-4 and the VL-4, a triabody comprising the VH-4 and the VL-4, a tetrabody comprising the VH-4 and the VL-4, a scFv-Fc comprising the VH-4 and the VL-4, a scFv-CH comprising the VH-4 and the VL-4, a minibody comprising the VH-4 and the VL-4, a scFv-zipper comprising the VH-4 and the VL-4, a diabody -Fc comprising the VH-4 and the VL-4, a diabody-CH comprising the VH-4 and the VL-4. and / or a scFab comprising the VH-4 and the VL-4; (d) a HCAb comprising the VH-4, a nanobody-Fccomprising the VH-4, a nanobody-CH comprising the VH-4, a camel Ig comprising the VH- 4, an IgNAR comprising the VH-4, and / or a single-chain variant of any of the foregoing: and / or (e) a sdAb comprising the VH-4, a nanobody comprising the VH-4, and / or a tandem nanobody comprising the VH-4,

[0132] In some cases, (f) the ABR-1 and the ABR-2 may be associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds. In some cases, (g) the ABR-1 and the ABR-3 may be associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds. In some cases, (h) the ABR-1 and the ABR-4 may be associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds. In some cases, (i) the ABR-2 and the ABR-3 may be associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds. In some cases, (j) the ABR-2 and the ABR-4 may be associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds. In some cases, (k) the ABR-3 and the ABR-4 may be associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds. In some cases, the ABR-4 may be directly associated with or linked to any one or more of ABR-1, ABR-2. and / or ABR-4.

[0133] In particular embodiments, the multi-specific antibody may comprise a structure depicted in any one of FIGS. 1-6, optionally any one of FIGS. 4-6, further optionally any one of FIGS. 4A-4C, 5A-5N, and 6. In particular cases, the multi-specific antibody may comprise a structure depicted in the boxed structure of FIG. 2G.

[0134] In some cases, in any of the multi-specific antibodies described above: (1) the ABR-4 comprises: at least one Ig constant domain, optionally one or more of a CH1, a CH2, a CH3, and / or a CL; and / or a Fc region, further optionally wherein: (a) the CH1, CH2, and / or the CH3 is / are individually of an IgG, IgA, IgE. IgD, or IgM class, optionally of an IgG1, IgG2, IgG3, and / or IgG4 subclass; (b) the CL is a CLK or a CL / .: and / or (c) the Fc region is of an IgG, IgA, IgE, IgD, or IgM class, optionally of an IgG1, IgG2, IgG3, and / or IgG4 subclass.

[0135] In some cases, in any of the multi-specific antibodies described above: (2) the multi-specific antibody may comprise common light chains, and / or the VL-1 and the VL-2 have the same or essentially the same amino acid sequences, and / or the VL-1 and the VL-3have the same or essentially the same amino acid sequences and / or the VL-1 and the VL-4 have the same or essentially the same amino acid sequences, and / or the VL-2 and the VL-3 have the same or essentially the same amino acid sequences and / or the VL-2 and the VL-4 have the same or essentially the same amino acid sequences, and / or the VL-3 and the VL-4 have the same or essentially the same amino acid sequences. In certain cases, (i) the second antigen may be human CD3 and the amino acid sequences of the VL-1 and the VL-2 may individually have at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity to the amino acid sequences of the VL of ADI-26921 (SEQ ID NO: 13270) or comprise or consist of SEQ ID NO: 13270; (ii) the third antigen may be human CD3 and the amino acid sequences of the VL-1 and the VL-3 may individually have at least about 80%. 85%. 90%. 91%. 92%. 93%. 94%. 95%, 96%, 97%, 98%, or 99% sequence identity to the amino acid sequences of the VL of ADI-26921 (SEQ ID NO: 13270) or comprise or consist of SEQ ID NO: 13270; and / or (iii) the fourth antigen may be human CD3 and the amino acid sequences of the VL-1 and the VL-4 may individually have at least about 80%. 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity to the amino acid sequences of the VL of ADI-26921 (SEQ ID NO: 13270) or comprise or consist of SEQ ID NO: 1327.

[0136] For example, in any of the embodiments described herein, when the sequences of the VL-1 and the VL-2 (or the VL-1 and the VL-3, and / or the VL-1 and the VL-4) are the same, such VL domains having the same sequences may be referred to as “common VL” or “ cVL” domains. Similarly, light chains having the same sequences may be referred to as “common light chains” or “cLCs”.

[0137] In some cases, in any of the multi-specific antibodies described above: (3) the multi-specific antibody may comprise one or more of the following: (3-i) a heavy chain constant region (CH), optionally a CH1, which is engineered to promote pairing with a CLK over a CLk, optionally wherein the CH1 engineering is one of those described in WO2021067404; (3-ii) a CH, optionally a CH1, which is engineered to promote pairing with a CLk over a CLK, optionally wherein the CH1 engineering is one of those described in WO2021067404; and / or (3-iii) a CH, optionally a CH1. which is engineered to promote pairing with an engineered CL comprised in the multi-specific antibody over another CL, optionally wherein the combination of the CH engineering and the CL engineering is one of those described in WO2022150787; and / or (3-iv) two CHs having different amino acid sequences, optionally two CH3s having different amino acid sequences, which are engineeredto promote heteromeric paring between the two CHs over homomeric pairing, optionally wherein the CH3 engineering is one of those described in WO2022150785.

[0138] In one aspect, the disclosure provides multi-specific antibodies, which optionally may be any of the multispecific antibodies described above.

[0139] In some embodiments, the multispecific antibody may comprise: (A) at least one antigen-binding region which binds to antigen A (ABR-A), comprising: (A-i) at least one heavy chain A which comprises a heavy chain variable domain A (VH-A) and a heavy chain constant region A (CH- A), optionally from the N-terminus to the C-terminus, optionally wherein the CH-A comprises: (a) a heavy chain constant domain 1 A (CH1-A), a hinge (hinge-A), a heavy chain constant domain 2 A (CH2-A), and / or a heavy chain constant domain 3 A (CH3-A); and / or (b) a CH1 -A, a hinge-A, a CH2-A, and a CH3-A. optionally from the N-terminus to the C-terminus; and optionally (A-ii) at least one light chain A which comprises a light chain variable domain A (VL-A) and a light chain constant domain A (CL- A), wherein the heavy chain A and the light chain A (if present) are paired with each other, optionally via at least one disulfide bond; and (B) at least one antigen-binding region B (ABR-B) which comprises a Fab which binds to antigen B (Fab-B), comprising: (B-i) a heavy chain B which comprises a heavy chain variable domain B (VH-B) and a heavy chain constant region B (CH-B) comprising at least a heavy chain constant domain 1 B (CH1-B); and (B-ii) a light chain B which comprises a light chain variable domain B (VL-B) and a light chain constant domain B (CL-B), wherein the heavy chain B and the light chain B are paired with each other, optionally via at least one disulfide bond, to form an antigen-binding region which binds to the antigen B.

[0140] In some cases, (a) the heavy chain B, optionally the C-terminus of or the N- terminus of the heavy chain B. is associated with or linked to: (a-1) the heavy chain A. optionally the N-terminus of or the C-terminus of the heavy chain A; or (a-2) the light chain A (if present), optionally the N-terminus of or the C-terminus of the light chain A (if present), optionally via a linker, further optionally a peptide linker, yet further optionally a flexible peptide linker.

[0141] In some cases, (b) the light chain B, optionally the C-terminus of or the N-terminus of the light chain B, is associated with or linked to: (b-1) the light chain A (if present), optionally the N-terminus of or the C-terminus of the light chain A (if present); and / or (b-2) the heavy chain A, optionally the N-terminus of or the C-terminus of the heavy chain A, optionally via a linker, further optionally a peptide linker, yet further optionally a flexible peptide linker.

[0142] In certain embodiments, the multi-specific antibody may comprise a structure depicted in any one of FIGS. 1-6, optionally according to any one of FIGS. 2A-2I, 3A-3B, 4A-4C, and 5A-5I, and further optionally wherein the antigen B is the same as or different from antigen A. In particular embodiments, the multi-specific antibody may comprise a structure depicted in the boxed structure of FIG. 2G.

[0143] In some embodiments, the multispecific antibody may comprise: (A) at least one antigen-binding region which binds to antigen A (ABR-A). comprising: (A-i) at least one heavy chain A which comprises a heavy chain variable domain A (VH-A) and a heavy chain constant region A (CH- A), optionally from the N-terminus to the C-terminus, optionally wherein the CH-A comprises: (a) a heavy chain constant domain 1 A (CH1-A), a hinge (hinge-A), a heavy chain constant domain 2 A (CH2-A), and / or a heavy chain constant domain 3 A (CH3-A); and / or (b) a CH1 -A, a hinge-A, a CH2-A, and a CH3-A, optionally from the N-terminus to the C-terminus; and optionally ( A-ii) at least one light chain A which comprises a light chain variable domain A (VL-A) and a light chain constant domain A (CL-A), wherein the heavy chain A and the light chain A (if present) are paired with each other, optionally via at least one disulfide bond, to form an antigen-binding region which binds to antigen A; and (B) at least one antigen-binding region B (ABR-B) which comprises a scFv which binds to antigen B (scFv-B), comprising: (B-i) a heavy chain variable domain B (VH-B); and (B-ii) a light chain variable domain B (VL-B).

[0144] In some cases, (a) the C-terminus of the VH-B is linked to the N-terminus of the VL-B, optionally wherein the scFv-B comprises the VH-B, a linker, and the VL-B from the N-terminus to the C-terminus; or (b) the C-terminus of the VL-B is linked to the N-terminus of the VH-B, optionally wherein the scFv-B comprises the VL-B. a linker, and the VH-B from the N-terminus to the C-terminus.

[0145] In some cases, the scFv-B, optionally the C-terminus of or the N-terminus of the scFv-B, may be associated with or linked to: (1) the heavy chain A, optionally the N-terminus of or the C-terminus of the heavy chain A; and / or (2) the light chain A (if present), optionally the N-terminus of or the C-terminus of the light chain A (if present), optionally via a linker, further optionally a peptide linker, yet further optionally a flexible peptide linker.

[0146] In certain embodiments, the multi-specific antibody may comprise a structure depicted in any one of FIGS. 1-6, optionally according to any one of FIGS. 2A, 2F, 2 J, 3A- 3B, 4A-4C, 5C-5G, and 5J-5N, and optionally wherein the antigen B is the same as or different from antigen A.

[0147] In some embodiments, the multispecific antibody may comprise: (A) at least one antigen-binding region which binds to antigen A (ABR-A), comprising: (A-i) at least one heavy chain A which comprises a heavy chain variable domain A (VH-A) and a heavy chain constant region A (CH- A), optionally from the N-terminus to the C-terminus, optionally wherein the CH-A comprises: (a) a heavy chain constant domain 1 A (CH1-A), a hinge (hinge-A), a heavy chain constant domain 2 A (CH2-A), and / or a heavy chain constant domain 3 A (CH3-A); and / or (b) a CH1 -A, a hinge-A, a CH2-A, and a CH3-A. optionally from the N-terminus to the C-terminus; and optionally ( A-ii) at least one light chain A which comprises a light chain variable domain A (VL-A) and a light chain constant domain A (CL- A), wherein the heavy chain A and the light chain A (if present) are paired with each other, optionally via at least one disulfide bond, to form an antigen-binding region which binds to antigen A; and (B) at least one antigen-binding region B (ABR-B) which comprises a scFab which binds to antigen B (scFab-B), comprising: (B-i) a heavy chain B which comprises a heavy chain variable domain B (VH-B) and a heavy chain constant region B (CH-B) comprising at least a heavy chain constant domain 1 B (CH1-B); and (B-ii) alight chain B which comprises a light chain variable domain B (VL-B) and a light chain constant domain B (CL-B), wherein: (a) the C-terminus of the heavy chain B is linked to the N-terminus of the light chain B, optionally wherein the scFab-B comprises the heavy chain B, a linker, and the light chain B from the N-terminus to the C-terminus; or (b) the C-terminus of the light chain B is linked to the N-terminus of the heavy chain B, optionally wherein the scFab-B comprises the light chain B, a linker, and the heavy chain B from the N-terminus to the C-terminus,

[0148] In some cases, the scFab-B, optionally the C-terminus of or the N-terminus of the scFab-B, is associated with or linked to: (1) the heavy chain A, optionally the N-terminus of or the C-terminus of the heavy chain A; and / or (2) the light chain A (if present), optionally the N-terminus of or the C-terminus of the light chain A (if present), optionally via a linker, further optionally a peptide linker, yet further optionally a flexible peptide linker.

[0149] In certain embodiments, the multi-specific antibody may comprise a structure depicted in any one of FIGS. 1-6, optionally according to any one of FIGS. 2A, 2F, 2K, 3A- 3B, and 4A-4C, and optionally wherein the antigen B is the same as or different from antigen A.

[0150] In some embodiments, the multispecific antibody may comprise: (A) at least one antigen-binding region which binds to antigen A (ABR-A), comprising: (A-i) at least one heavy chain A which comprises a heavy chain variable domain A (VH-A) and a heavy chain constant region A (CH-A), optionally from the N-terminus to the C-terminus, optionallywherein the CH-A comprises: (a) a heavy chain constant domain 1 A (CH1-A), a hinge (hinge-A), a heavy chain constant domain 2 A (CH2-A), and / or a heavy chain constant domain 3 A (CH3-A); and / or (b) a CH1 -A, a hinge-A, a CH2-A, and a CH3-A, optionally from the N-terminus to the C-terminus; and optionally ( A-ii) at least one light chain A which comprises a light chain variable domain A (VL-A) and a light chain constant domain A (CL- A), wherein the heavy chain A and the light chain A are paired with each other, optionally via at least one disulfide bond, to form an antigen-binding region which binds to antigen A; and (B) at least one antigen-binding region B (ABR-B) which comprises a sdAb which binds to antigen B (sdAb-B), comprising a heavy chain variable domain B (VH-B).

[0151] In some cases, the sdAb, optionally the C-terminus of or the N-terminus of the sdAb-B, is associated with or linked to: (1) the heavy chain A, optionally the N-terminus of or the C-terminus of the heavy chain A; and / or (2) the light chain A (if present), optionally the N-terminus of or the C-terminus of the light chain A (if present), optionally via a linker, further optionally a peptide linker, yet further optionally a flexible peptide linker.

[0152] In certain embodiments, the multi-specific antibody may comprise a structure depicted in any one of FIGS. 1-6. optionally according to any one of FIGS. 2-6 which is further modified to omit at least one VL, and further optionally wherein the antigen B is the same as or different from antigen A.

[0153] In some embodiments, the multispecific antibody may comprise: (A) at least one antigen-binding region which binds to antigen A (ABR-A). comprising: (A-i) at least one heavy chain A which comprises a heavy chain variable domain A (VH-A) and a heavy chain constant region A (CH-A), optionally from the N-terminus to the C-terminus, optionally wherein the CH-A comprises: (a) a heavy chain constant domain 1 A (CH1 -A), a hinge A (hinge-A), a heavy chain constant domain 2 A (CH2-A), and / or a heavy chain constant domain 3 A (CH3-A); and / or (b) a CH1 -A, a hinge-A, a CH2-A, and a CH3-A, optionally from the N-terminus to the C-terminus; and optionally (A-ii) at least one light chain A which comprises a light chain variable domain A (VL-A) and a light chain constant domain A (CL- A), wherein the heavy chain A and the light chain A (if present) are paired with each other, optionally via at least one disulfide bond, to form an antigen-binding region which binds to antigen A; and (B) at least one antigen-binding region which binds to antigen B (ABR-B), comprising: (B-i) at least one heavy chain B which comprises a heavy chain variable domain B (VH-B) and a heavy chain constant region B (CH-B), optionally from the N-terminus to the C-terminus, optionally wherein the CH-B comprises: (a) a heavy chain constant domain 1 B (CH1-B), a hinge B (hinge-B), a heavy chain constant domain 2 B (CH2-B), and / or a heavychain constant domain 3 B (CH3-A); and / or (b) a CH1-B, a hinge-B, a CH2-B, and a CH3-B, optionally from the N-terminus to the C -terminus; and optionally (B-ii) at least one light chain B which comprises a light chain variable domain B (VL-B) and a light chain constant domain B (CL-B), wherein the heavy chain B and the light chain B (if present) are paired with each other, optionally via at least one disulfide bond, to form an antigen-binding region which binds to antigen B, optionally wherein the heavy chain A and the heavy chain B are paired with each other, optionally via at least one disulfide bond.

[0154] In certain embodiments, (a) (a-1) the light chain A (if present) and the light chain B (if present) may have the same or essentially the same amino acid sequences or are common light chains.

[0155] In certain embodiments, (a-2) (a-2i) the CH-A and / or the CL-A (if present), optionally the CH1 -A and / or the CL-A (if present), may be engineered to promote pairing between the CH-A and the CL-A over between the CH-A and the CL-B and / or over between the CH-B and the CL-A, optionally wherein: (1) the CL-A is a CLK and the CH-A, optionally the CH1 -A, is engineered to promote pairing with a CLK over a CLk. optionally wherein the CH1-A engineering is one of those described in WO2021067404; (2) the CL-A is a CLk and the CH-A, optionally the CH1 -A, is engineered to promote pairing with a CLk over a CLK, optionally wherein the CH1-A engineering is one of those described in WO2021067404; or (3) both the CH-A. optionally the CH1 -A, and the CL-A are engineered to promote pairing between the CH-A and the CL-A over between the CH-A and the CL-B and / or between the CH-B and the CL-A, optionally wherein the combination of the CH-A engineering and the CL-A engineering is one of those described in WO2022150787.

[0156] In certain embodiments, (a-2) (a-2ii) the CH-B and / or the CL-B (if present), optionally the CH1-B and / or the CL-B (if present), may be engineered to promote pairing between the CH-B and the CL-B over between the CH-B and the CL-A and / or over between the CH-A and the CL-B, optionally wherein: (1) the CL-B is a CLk and the CH-B, optionally the CH1-B, is engineered to promote pairing with a CLk over a CLK, optionally wherein the CH1-B engineering is one of those described in WO2021067404; (2) the CL-B is a CLK and the CH-B, optionally the CH1-B, is engineered to promote pairing with a CLK over a CLk. optionally wherein the CH1-B engineering is one of those described in WO2021067404; or (3) both the CH-B, optionally the CH1-B, and the CL-B are engineered to promote pairing between the CH-B and the CL-B over between the CH-B and the CL-A and / or between the CH-A and the CL-B. optionally wherein the combination of the CH-B engineering and the CL-B engineering is one of those described in WO2022150787.

[0157] In certain embodiments, (b) the CH- A and / or the CH-B, optionally the CH3-A and / or the CH3-B and / or optionally the CH3-A and / or the CH3-B, may be engineered to promote heteromeric paring between the CH-A and the CH-B over homomeric CH-A pairing and / or homomeric CH-B pairing, optionally wherein the CH3-A and / or CH3-B engineering is one of those described in WO2022150785.

[0158] In certain embodiments, the multi-specific antibody may comprise a structure depicted in any one of FIGS. 1-6, optionally according to any one of FIGS. 2G-2K, 3A-3B, 4A-4C, and 5A-5N, and optionally wherein said antigen B is the same as or different from antigen A. In certain embodiments, the multi-specific antibody may comprise a structure depicted in the boxed structure of FIG. 2G.

[0159] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1 and an ABR-2, wherein: (I) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1; and (B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2; or (II) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2; and (B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1.

[0160] In some embodiments, any of the multispecific antibodies described above comprising an ABR-A and an ABR-B may further comprise: (C) at least one antigen-binding region which binds to antigen C (ABR-C).

[0161] In certain embodiments, the ABR-C may comprise: (C-l) a Fab which binds to antigen C (Fab-C). comprising: (C-l-i) a heavy chain C which comprises a heavy chain variable domain C (VH-C) and a heavy chain constant region C (CH-C) comprising at least a heavy chain constant domain 1 C (CH1-C); and (C-ii) a light chain C which comprises a light chain variable domain C (VL-C) and a light chain constant domain C (CL-C), wherein the heavy chain C and the light chain C are paired with each other, optionally via at least one disulfide bond.

[0162] In certain embodiments, the ABR-C may comprise: (C-2) a scFv which binds to antigen C (scFv-C), comprising: (C-i) a heavy chain variable domain C (VH-C); and (C-ii) a light chain variable domain C (VL-C). wherein: (a) the C-terminus of the VH-C is linked to the N-terminus of the VL-C. optionally wherein the scFv-C comprises the VH-C, a linker, and the VL-C from the N-terminus to the C-terminus; or (b) the C-terminus of the VL-C islinked to the N-terminus of the VH-C, optionally wherein the scFv-C comprises the VL-C, a linker, and the VH-C from the N-terminus to the C -terminus.

[0163] In certain embodiments, the ABR-C may comprise: (C-3) (a) which binds to antigen C (scFab-C), comprising: (C-i) a heavy chain C which comprises a heavy chain variable domain C (VH-C) and a heavy chain constant region C (CH-C) comprising at least a heavy chain constant domain 1 C (CH1-C); and (C-ii) a light chain C which comprises a light chain variable domain C (VL-C) and a light chain constant domain C (CL-C), wherein: (a) the C-terminus of the heavy chain C is linked to the N-terminus of the light chain C, optionally wherein the scFab-C comprises the heavy chain C, a linker, and the light chain B from the N-terminus to the C-terminus; or (b) the C-terminus of the light chain C is linked to the N-terminus of the heavy chain C, optionally wherein the scFab-C comprises the light chain C, a linker, and the heavy chain C from the N-terminus to the C-terminus.

[0164] In certain embodiments, the ABR-C may comprise: (C-4) at least one sdAb which binds to antigen C (sdFab-C), comprising a heavy chain variable domain C (VH-C).

[0165] In particular embodiments, the multi -specific antibody comprises a structure depicted in any one of FIGS. 1-6. optionally according to any one of FIGS. 2-6. optionally wherein the antigen C is the same as or different from antigen A and / or antigen B.

[0166] In some cases, in (C-l), the Fab-C is associated with or linked to the ABR-A and / or the ABR-B, optionally wherein: (a) the heavy chain C. optionally the C-terminus of or the N-terminus of the heavy chain C, may be associated with or linked to the ABR-A and / or the ABR-B, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A and / or the C- terminus of and / or the N-terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, optionally via a linker; and / or (b) the light chain C, optionally the C-terminus of or the N-terminus of the light chain C, may be associated with or linked to the ABR-A and / or the ABR-B, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A and / or the C- terminus of and / or the N-terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, optionally via a linker, optionally a peptide linker, yet further optionally a flexible peptide linker.

[0167] In some cases, in (C-2). the scFv-C, optionally the C-terminus of or the N-terminus of the scFv-C, may be associated with or linked to the ABR-A and / or the ABR-B, optionallyassociated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A and / or the C-terminus of and / or the N- terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, optionally via a linker, optionally a peptide linker, yet further optionally a flexible peptide linker.

[0168] In some cases, in (C-3), the scFab-C, optionally the C-terminus of or the N- terminus of the scFab-C. may be associated with or linked to the ABR-A and / or the ABR-B. optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A and / or the C-terminus of and / or the N-terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, optionally via a linker, optionally a peptide linker, yet further optionally a flexible peptide linker.

[0169] In some cases, in (C-4), the sdFab-C, optionally the C-terminus of or the N- terminus of the sdAb-C, may be associated with or linked to the ABR-A and / or the ABR-B, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A and / or the C-terminus of and / or the N-terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, optionally via a linker, optionally a peptide linker, yet further optionally a flexible peptide linker.

[0170] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, and an ABR-3, wherein: (I) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1; (B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2; and (C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3.

[0171] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, and an ABR-3, wherein: (II) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1; (B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises theVL-3; and (C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH- 2 and / or the VL-C (if present) is or comprises the VL-2.

[0172] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, and an ABR-3, wherein: (III) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2; (B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1; and (C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3.

[0173] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, and an ABR-3, wherein: (IV) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2; (B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3; and (C) the antigen C is human CD28. wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1.

[0174] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, and an ABR-3, wherein: (V) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3; (B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1; and (C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2; or

[0175] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, and an ABR-3, wherein: (VI) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3; (B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2; and (C) the antigen C is human CD28. wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1.

[0176] In some embodiments, any of the multispecific antibodies described above comprising an ABR-A and an ABR-B may further comprise: (D) at least one antigen-binding region which binds to antigen D (ABR-D).

[0177] In certain embodiments, the ABR-D may comprise: (D-l) a Fab which binds to antigen D (Fab-D). comprising: (D-l-i) a heavy chain D which comprises a heavy chain variable domain D (VH-D) and a heavy chain constant region D (CH-D) comprising at least a heavy chain constant domain 1 D (CH1-D); and (D-ii) a light chain D which comprises a light chain variable domain D (VL-D) and a light chain constant domain D (CL-D), wherein the heavy chain D and the light chain D are paired with each other, optionally via at least one disulfide bond.

[0178] In certain embodiments, the ABR-D may comprise: (D-2) a scFv which binds to antigen D (scFv-D), comprising: (D-i) a heavy chain variable domain D (VH-D); and (D-ii) a light chain variable domain D (VL-D), wherein: (a) the C-terminus of the VH-D is linked to the N-terminus of the VL-D. optionally wherein the scFv-D comprises the VH-D, a linker, and the VL-D from the N-terminus to the C-terminus; or (b) the C-terminus of the VL-D is linked to the N-terminus of the VH-D, optionally wherein the scFv-D comprises the VL-D, a linker, and the VH-D from the N-terminus to the C-terminus;

[0179] In certain embodiments, the ABR-D may comprise: (D-3) a scFab which binds to antigen D (scFab-D), comprising: (D-i) a heavy chain D which comprises a heavy chain variable domain D (VH-D) and a heavy chain constant region D (CH-D) comprising at least a heavy chain constant domain 1 D (CH1-D); and (D-ii) a light chain D which comprises a light chain variable domain D (VL-D) and a light chain constant domain D (CL-D), wherein: (a) the C-terminus of the heavy chain D is linked to the N-terminus of the light chain D, optionally wherein the scFab-D comprises the heavy chain D, a linker, and the light chain D from the N-terminus to the C-terminus; or (b) the C-terminus of the light chain D is linked to the N-terminus of the heavy chain D, optionally wherein the scFab-D comprises the light chain D, a linker, and the heavy chain D from the N-terminus to the C-terminus.

[0180] In certain embodiments, the ABR-D may comprise: (D-4) a sdAb which binds to antigen D (sdFab-D), comprising a heavy chain variable domain D (VH-D).

[0181] In particular embodiments, the multi-specific antibody may comprise a structure depicted in any one of FIGS. 1-6, optionally according to any one of FIGS. 2-6, optionally wherein the antigen D is the same as or different from antigen A. antigen B, and / or antigen C.

[0182] In some cases, in (D-l), the Fab-D is associated with or linked to the ABR-A, the ABR-B, and / or the ABR-C, optionally wherein: (a) the heavy chain D, optionally the C- terminus of or the N-terminus of the heavy' chain D, is associated with or linked to the ABR- A, the ABR-B. and / or the ABR-C. optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A, the C-terminus of and / or the N-terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, and / or the C-terminus of and / or the N-terminus of the heavy chain C (if present) and / or the light chain C (if present), the scFv-C (if present), the scFab-C (if present), or the sdAb-C (if present) of the ABR-C, optionally via a linker; and / or (a) the light chain D, optionally the C-terminus of or the N-terminus of the light chain C, is associated wi th or linked to the ABR-A, the ABR-B. and / or the ABR-C. optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A, the C-terminus of and / or the N-terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, and / or the C-terminus of and / or the N- terminus of the heavy chain C (if present) and / or the light chain C (if present), the scFv-C (if present), the scFab-C (if present), or the sdAb-C (if present) of the ABR-C, optionally via a linker, optionally a peptide linker, yet further optionally a flexible peptide linker.

[0183] In some cases, in (D-2). the scFv-D, optionally the C-terminus of or the N- terminus of the scFv-D, is associated with or linked to the ABR-A. the ABR-B, and / or the ABR-C, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A, the C-terminus of and / or the N-terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, and / or the C-terminus of and / or the N-terminus of the heavy chain C (if present) and / or the light chain C (if present), the scFv-C (if present), the scFab-C (if present), or the sdAb-C (if present) of the ABR-C, optionally via a linker, optionally a peptide linker, yet further optionally a flexible peptide linker.

[0184] In some cases, in (D-3), the scFab-D, optionally the C-terminus of or the N- terminus of the scFab-D, is associated with or linked to the ABR-A, the ABR-B, and / or the ABR-C, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A, the C-terminus of and / or the N-terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, and / or the C-terminus of and / or the N-terminus of the heavy chain C (if present) and / or the light chain C (if present), the scFv-C (if present), the scFab-C (if present), or the sdAb-C (if present) of the ABR-C, optionally via a linker, optionally a peptide linker, yet further optionally a flexible peptide linker.

[0185] In some cases, in (D-4), the sdFab-D, optionally the C-terminus of or the N- terminus of the sdAb-D, is associated with or linked to the ABR-A. the ABR-B, and / or the ABR-C, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A, the C-terminus of and / or the N-terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, and / or the C-terminus of and / or the N-terminus of the heavy chain C (if present) and / or the light chain C (if present), the scFv-C (if present), the scFab-C (if present), or the sdAb-C (if present) of the ABR-C, optionally via a linker, optionally a peptide linker, yet further optionally a flexible peptide linker.

[0186] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (I) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1; (B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2; (C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3; and (D) the antigen D is the fourth antigen, wherein the VH-D is or comprises the VH-4 and / or the VL-D (if present) is or comprises the VL-4.

[0187] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (II) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1; (B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2; (C) the antigen C is the fourth antigen, wherein the VH-C is or comprises the VH-4 and / or the VL-C (if present) is or comprises the VL-4; and (D) the antigen D is the third antigen, wherein the VH-D is or comprises the VH-3 and / or the VL-D (if present) is or comprises the VL-3.

[0188] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (III) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1; (B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3; (C) the antigen C is the second antigen, wherein the VH-C is orcomprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2; and (D) the antigen D is the fourth antigen, wherein the VH-D is or comprises the VH-4 and / or the VL-D (if present) is or comprises the VL-4.

[0189] In particular embodiments, the multi-specific antibody may any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (IV) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1; (B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3; (C) the antigen C is the fourth antigen, wherein the VH-C is or comprises the VH-4 and / or the VL-C (if present) is or comprises the VL-4; and (D) the antigen D is the second antigen, wherein the VH-D is or comprises the VH-2 and / or the VL- D (if present) is or comprises the VL-2.

[0190] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (V) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1; (B) the antigen B is the fourth antigen, wherein the VH-B is or comprises the VH-4 and / or the VL-B (if present) is or comprises the VL-4; (C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2; and (D) the antigen D is the third antigen, wherein the VH-D is or comprises the VH-3 and / or the VL-D (if present) is or comprises the VL-3.

[0191] In particular embodiments, the multi -specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (VI) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1; (B) the antigen B is the fourth antigen, wherein the VH-B is or comprises the VH-4 and / or the VL-B (if present) is or comprises the VL-4; (C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3; and (D) the antigen D is the second antigen, wherein the VH-D is or comprises the VH-2 and / or the VL-D (if present) is or comprises the VL-2.

[0192] In particular embodiments, the multi -specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (VII) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2; (B) the antigen Bis human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1; (C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3; and (D) the antigen D is the fourth antigen, wherein the VH-D is or comprises the VH-4 and / or the VL-D (if present) is or comprises the VL-4.

[0193] In particular embodiments, the multi -specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (VIII) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2; (B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1; (C) the antigen C is the fourth antigen, wherein the VH-C is or comprises the VH-4 and / or the VL-C (if present) is or comprises the VL-4; and (D) the antigen D is the third antigen, wherein the VH-D is or comprises the VH-3 and / or the VL-D (if present) is or comprises the VL-3.

[0194] In particular embodiments, the multi -specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (IX) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2; (B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3; (C) the antigen C is human CD28, wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1 ; and (D) the antigen D is the fourth antigen, wherein the VH-D is or comprises the VH-4 and / or the VL-D (if present) is or comprises the VL-4.

[0195] In particular embodiments, the multi -specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (X) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2; (B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3; (C) the antigen C is the fourth antigen, wherein the VH-C is or comprises the VH-4 and / or the VL-C (if present) is or comprises the VL-4; and (D) the antigen D is human CD28, wherein the VH-D is or comprises the VH-1 and / or the VL-D (if present) is or comprises the VL-1.

[0196] In particular embodiments, the multi -specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, andABR-4, wherein: (XI) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2: (B) the antigen B is the fourth antigen, wherein the VH-B is or comprises the VH-4 and / or the VL-B (if present) is or comprises the VL-4; (C) the antigen C is human CD28, wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1; and (D) the antigen D is the third antigen, wherein the VH-D is or comprises the VH-3 and / or the VL-D (if present) is or comprises the VL-3.

[0197] In particular embodiments, the multi -specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (XII) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2: (B) the antigen B is the fourth antigen, wherein the VH-B is or comprises the VH-4 and / or the VL-B (if present) is or comprises the VL-4; (C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3; and (D) the antigen D is human CD28. wherein the VH-D is or comprises the VH-1 and / or the VL-D (if present) is or comprises the VL-1.

[0198] In particular embodiments, the multi -specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (XIII) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3: (B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1; (C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2; and (D) the antigen D is the fourth antigen, wherein the VH-D is or comprises the VH-4 and / or the VL-D (if present) is or comprises the VL-4.

[0199] In particular embodiments, the multi -specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (XIV) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3: (B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1; (C) the antigen C is the fourth antigen, wherein the VH-C is or comprises the VH-4 and / or the VL-C (if present) is or comprises the VL-4; and (D) the antigen D is the second antigen, wherein the VH-D is or comprises the VH-2 and / or the VL- D (if present) is or comprises the VL-2.

[0200] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (XV) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3; (B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2; (C) the antigen C is human CD28, wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1; and (D) the antigen D is the fourth antigen, wherein the VH-D is or comprises the VH-4 and / or the VL-D (if present) is or comprises the VL-4.

[0201] In particular embodiments, the multi -specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (XVI) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3; (B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2; (C) the antigen C is the fourth antigen, wherein the VH-C is or comprises the VH-4 and / or the VL-C (if present) is or comprises the VL-4; and (D) the antigen D is human CD28, wherein the VH-D is or comprises the VH-1 and / or the VL-D (if present) is or comprises the VL-1.

[0202] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (XVII) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3; (B) the antigen B is the fourth antigen, wherein the VH-B is or comprises the VH-4 and / or the VL-B (if present) is or comprises the VL-4; (C) the antigen C is human CD28, wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1; and (D) the antigen D is the second antigen, wherein the VH-D is or comprises the VH-2 and / or the VL- D (if present) is or comprises the VL-2.

[0203] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (XVIII) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3; (B) the antigen B is the fourth antigen, wherein the VH-B is or comprises the VH-4 and / or the VL-B (if present) is or comprises the VL-4; (C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2; and (D) theantigen D is human CD28, wherein the VH-D is or comprises the VH-1 and / or the VL-D (if present) is or comprises the VL-1.

[0204] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (IXX) (A) the antigen A is the fourth antigen, wherein the VH-A is or comprises the VH-4 and / or the VL-A (if present) is or comprises the VL-4; (B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1; (C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2; and (D) the antigen D is the third antigen, wherein the VH-D is or comprises the VH-3 and / or the VL-D (if present) is or comprises the VL-3.

[0205] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (XX) (A) the antigen A is the fourth antigen, wherein the VH-A is or comprises the VH-4 and / or the VL-A (if present) is or comprises the VL-4; (B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1; (C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3; and (D) the antigen D is the second antigen, wherein the VH-D is or comprises the VH-2 and / or the VL- D (if present) is or comprises the VL-2.

[0206] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (XXI) (A) the antigen A is the fourth antigen, wherein the VH-A is or comprises the VH-4 and / or the VL-A (if present) is or comprises the VL-4; (B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2; (C) the antigen C is human CD28, wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1; and (D) the antigen D is the third antigen, wherein the VH-D is or comprises the VH-3 and / or the VL-D (if present) is or comprises the VL-3.

[0207] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (XXII) (A) the antigen A is the fourth antigen, wherein the VH-A is or comprises the VH-4 and / or the VL-A (if present) is or comprises the VL-4; (B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (ifpresent) is or comprises the VL-2; (C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3; and (D) the antigen D is human CD28, wherein the VH-D is or comprises the VH-1 and / or the VL-D (if present) is or comprises the VL-1.

[0208] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (XXIII) (A) the antigen A is the fourth antigen, wherein the VH-A is or comprises the VH-4 and / or the VL-A (if present) is or comprises the VL-4; (B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3; (C) the antigen C is human CD28, wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1; and (D) the antigen D is the second antigen, wherein the VH-D is or comprises the VH-2 and / or the VL- D (if present) is or comprises the VL-2.

[0209] In particular embodiments, the multi-specific antibody may be any of the multispecific antibodies described above comprising an ABR-1, an ABR-2, an ABR-3, and ABR-4, wherein: (XXIV) (A) the antigen A is the fourth antigen, wherein the VH-A is or comprises the VH-4 and / or the VL-A (if present) is or comprises the VL-4; (B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3; (C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2; and (D) the antigen D is human CD28, wherein the VH-D is or comprises the VH-1 and / or the VL-D (if present) is or comprises the VL-1.

[0210] In particular embodiments, a multi-specific antibody according to any of the multispecific antibodies described above may comprise a structure depicted in: any one of FIGS. 2C (left top), 2F, 2G (boxed), 2J (boxed), 2K (boxed), 2 J, and / or 2M, optionally wherein the antigen A and the antigen B are CD28 and CD3, respectively, or CD3 and CD28, respectively.

[0211] In particular embodiments, a multi-specific antibody according to a multi-specific antibody according to any of the multi-specific antibodies described above may comprise a structure depicted in: any one of FIGS. 3A-3B, optionally wherein: (a) the antigen A and the antigen B are CD28 and CD3, respectively, or CD3 and CD28, respectively; (b) the antigen A and the antigen C are CD28 and CD3. respectively, or CD3 and CD28. respectively; or (c) the antigen B and the antigen C are CD28 and CD3. respectively, or CD3 and CD28. respectively.

[0212] In particular embodiments, a multi-specific antibody according to any of the multispecific antibodies described above may comprise a structure depicted in: any one of FIGS.4A-4C, 5A (boxed), 5C-5F, 5H (top left), 51 (top left), and / or 5J-5M, optionally wherein: (a) the antigen A and the antigen B are CD28 and CD3, respectively, or CD3 and CD28, respectively; (b) the antigen A and the antigen C are CD28 and CD3, respectively, or CD3 and CD28, respectively; (c) the antigen A and the antigen D are CD28 and CD3, respectively, or CD3 and CD28. respectively; (d) the antigen B and the antigen C are CD28 and CD3. respectively, or CD3 and CD28, respectively; (e) the antigen B and the antigen D are CD28 and CD3, respectively, or CD3 and CD28, respectively; or (f) the antigen C and the antigen D are CD28 and CD3, respectively, or CD3 and CD28, respectively.

[0213] In certain embodiments, a multi-specific antibody according to any of the multispecific antibodies described above may bind monovalently, bivalently, trivalently, or tetravalently to: (a) human cluster of differentiation 3 (CD3); (b) a cancer antigen, optionally a TSA or a TAA; (c) human CD28; (d) any one of the antigens selected from those listed in Table 3; and / or (e) any one of the cancer antigens, optionally any one of the TSAs or any one of the TAAs. selected from those listed in Table 3.

[0214] In certain embodiments, a multi-specific antibody according to any of the multispecific antibodies described above may bind bivalently to CD3.

[0215] In one aspect, the disclosure provides nucleic acids encoding (e.g.. a nucleic acid encoding or a set of nucleic acids in combination encoding) any of the anti-human CD28 antibodies or antigen-binding antibody fragments described herein or any of the multispecific antibodies described herein or a portion thereof.

[0216] In some embodiments, a nucleic acid(s) may comprise: a VH-1 -encoding nucleic acid having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identity to any one of the VH-encoding sequences of Table 2A and / or 13A; and / or a VL-1 -encoding nucleic acid having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%. at least about 93%. at least about 94%. at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identity to any one of the VL-encoding sequences of Table 2A and / or 13A.

[0217] In certain embodiments, a nucleic acid(s) may comprise: a VH-1 -encoding nucleic acid having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about96%, at least about 97%, at least about 98%, at least about 99%, or 100% identity to the VH- encoding sequences of SEQ ID NO: 119, 2119, 2819.4619, 5719, 6119, 6819, 7019. or 8319; and / or a VL-1 -encoding nucleic acid having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identity to the VL-encoding sequences of SEQ ID NO: 129, 2129. 2829, 4629, 5729, 6129, or 6829.

[0218] In certain embodiments, a nucleic acid(s) may comprise: a VH-l-encoding nucleic acid and a VL-l-encoding nucleic acid having at least about 80%, at least about 85%, at least about 90%. at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%. at least about 97%. at least about 98%, at least about 99%, or 100% identity to SEQ ID NOS: 119 and 129, respectively, 2119 and 2129, respectively, 2819 and 2829, respectively, 4619 and 4629, respectively, 5719 and 5729, respectively, 6119 and 6129, respectively, or 6819 and 6829, respectively.

[0219] In particular embodiments, a nucleic acid(s) may comprise: a VH-1 -encoding nucleic acid and a VL-l-encoding nucleic acid having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%. or 100% identity to SEQ ID NOS: 119 and 129, respectively.

[0220] In certain embodiments, the encoded anti-CD28 antibody or antigen-binding antibody fragment comprising a VH-1 and a VL-1 may comprise a kappa VL. In particular embodiments, a nucleic acid(s) may comprise: a VH-l-encoding nucleic acid and a VL-l- encoding nucleic acid having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%. at least about 93%. at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identity to SEQ ID NOS: 2119 and 2129, respectively, or 2819 and 2829, respectively.

[0221] In certain embodiments, the encoded anti-CD28 antibody or antigen-binding antibody fragment comprising a VH-1 and a VL-1 may comprise a lambda VL. In particular embodiments, a nucleic acid(s) may comprise: a VH-1 -encoding nucleic acid and a VL-l- encoding nucleic acid having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%. at least about 97%, at least about 98%, at least about 99%, or 100% identity to SEQ ID NOS: 4619 and 4629, respectively, 5719 and 5729. respectively.

[0222] In certain embodiments, the encoded anti-CD28 antibody or antigen-binding antibody fragment comprising a VH-1 and a VL-1 may comprise a common VL (e.g., a VL which binds to CD28 when paired with a VH with specificity for CD28 and which binds to CD3 when paired with a VH with specificity for CD3). In particular embodiments, a nucleic acid(s) may comprise a VH-1 -encoding nucleic acid and a VL-1 -encoding nucleic acid having at least about 80%, at least about 85%. at least about 90%, at least about 91%, at least about 92%. at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identity to SEQ ID NOS: 6119 and 6129, respectively, or 6819 and 6829, respectively.

[0223] In certain embodiments, the encoded anti-CD28 antibody or antigen-binding antibody fragment comprising a VH-1 may be capable of binding to CD28 without a need of a VL (e.g., a VHH, a nanobody, single domain antibody (sdAb), heavy chain antibody (HCAb), etc). In particular embodiments, a nucleic acid(s) may comprise a VH-1 -encoding nucleic acid having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%. at least about 93%, at least about 94%, at least about 95%, at least about 96%. at least about 97%, at least about 98%, at least about 99%, or 100% identity to SEQ ID NO: 7019 or 8319.

[0224] In one aspect, the disclosure provides vectors encoding (e.g., a vector encoding or a set of vectors in combination encoding) any of the anti-human CD28 antibodies or antigenbinding antibody fragments described herein or any of the multi-specific antibodies described herein or a portion thereof. Such a vector or vectors may comprise the nucleic acid(s) described above.

[0225] In some embodiments, the vector may be an expression vector.

[0226] In some embodiments, the vector may comprise a plasmid, a viral vector(optionally adenoviral, lentiviral, or retroviral), a lipid-based vector, a self-replicating RNA vector, a virus-like particle, a polymer-based vector, and / or a nanoparticle, optionally a lipid- based nanoparticle.

[0227] In one aspect, the disclosure provides isolated, recombinant, and / or host cells comprising the nucleic acid(s) described above or the vector(s) described above.

[0228] In some embodiments, the cell may be or may comprise (i) a non-mammalian, optionally bacterial, yeast, fungal, protozoa, plant, or insect, bacterial cell(s).

[0229] In some embodiments, the cell may be or may comprise (ii) a mammalian, optionally human, non-human primate, monkey, rabbit, rodent, hamster, rat, or mouse cell(s).

[0230] In one aspect, the disclosure provides compositions comprising at least one excipient and at least one of: any of the anti-human CD28 antibodies or antigen-binding antibody fragments and / or any of the multi-specific antibodies described herein; any of the nucleic acids described herein; any of the vectors described above; and any of the isolated, recombinant, and / or host cells described herein.

[0231] In a further aspect, the disclosure provides methods of treating a disease, disorder, or condition in a subject. The method may comprise administering to the subject an effective amount of at least one of: any of the anti-human CD28 antibodies or antigen-binding antibody fragments and / or any of the multi-specific antibodies described herein; any of the nucleic acids described herein: any of the vectors described herein; and any of the isolated, recombinant, and / or host cells described herein; and / or any of the compositions described herein.

[0232] In some embodiments, the subject is (i) a mammal, optionally a human, a nonhuman primate, a monkey, a horse, a cow, sheep, a goat, a pig, a dog, a cat, a rabbit, a rodent, a hamster, a rat, or a mouse; or (ii) a non-mammalian vertebrate, optionally a bird, fish, an amphibian, or a reptile.

[0233] In some embodiments, the method may further comprise administering to the subject an additional agent, optionally an adjuvant or a therapeutic agent.

[0234] In some embodiments, the disease, disorder, or a condition may comprise cancer or a neoplastic condition, an autoimmune disease, a neurodegenerative disease, an infectious disease, an inflammatory disease, or another disease.

[0235] In certain embodiments, the cancer may be a solid cancer, optionally chosen from: one or more of mesothelioma, malignant pleural mesothelioma, non-small cell lung cancer, small cell lung cancer, squamous cell lung cancer, large cell lung cancer, pancreatic cancer, pancreatic ductal adenocarcinoma, esophageal adenocarcinoma, breast cancer, glioblastoma, ovarian cancer, colorectal cancer, prostate cancer, cervical cancer, skin cancer, melanoma, renal cancer, liver cancer, brain cancer, thymoma, sarcoma, carcinoma, uterine cancer, kidney cancer, gastrointestinal cancer, urothelial cancer, pharynx cancer, head and neck cancer, rectal cancer, esophagus cancer, or bladder cancer, or a metastasis thereof.

[0236] In certain embodiments, the cancer may be a liquid cancer, optionally chosen from: chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL), multiple myeloma, acute lymphoid leukemia (ALL), Hodgkin lymphoma, B-cell acute lymphoid leukemia (BALL), T-cell acute lymphoid leukemia (TALL), small lymphocytic leukemia (SLL). B cell prolymphocytic leukemia, blastic plasmacytoid dendritic cell neoplasm, Burkitt's lymphoma.diffuse large B cell lymphoma (DLBCL), DLBCL associated with chronic inflammation, chronic myeloid leukemia, myeloproliferative neoplasms, follicular lymphoma, pediatric follicular lymphoma, hairy cell leukemia, small cell- or a large cell-follicular lymphoma, malignant lymphoproliferative conditions, MALT lymphoma (extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue), Marginal zone lymphoma, myelodysplasia, myelodysplastic syndrome. non-Hodgkin lymphoma, plasmablastic lymphoma, plasmacytoid dendritic cell neoplasm. Waldenstrom macroglobulinemia. splenic marginal zone lymphoma, splenic lymphoma / leukemia, splenic diffuse red pulp small B-cell lymphoma, hairy cell leukemia-variant, lymphoplasmacytic lymphoma, a heavy chain disease, plasma cell myeloma, solitary plasmacytoma of bone, extraosseous plasmacytoma, nodal marginal zone lymphoma, pediatric nodal marginal zone lymphoma, primary cutaneous follicle center lymphoma, lymphomatoid granulomatosis, primary mediastinal (thymic) large B-cell lymphoma, intravascular large B-cell lymphoma, ALK+large B-cell lymphoma, large B-cell lymphoma arising in HHV8-associated multicentric Castleman disease, primary effusion lymphoma, B-cell lymphoma, acute myeloid leukemia (AML), or unclassifiable lymphoma.

[0237] In certain embodiments, the autoimmune or inflammatory disease is psoriasis, rheumatoid arthritis, autoimmune arthritis, type I diabetes, systemic lupus ery thematosus, myasthenia gravis, multiple sclerosis, scleroderma, inflammatory bowel disease, Crohn’s disease, ulcerative colitis, Guillain-Barre syndrome, chronic inflammatory demyelinating polyneuropathy, pemphigus vulgaris, Sjogren’s syndrome, Addison’s disease, Behcet’s disease, Schmidt syndrome, celiac disease, dermatomyositis, autoimmune vitiligo, Graves' disease, Hashimoto thyroiditis, Kawasaki disease, pernicious anemia, autoimmune vasculitis, or fibrosis;

[0238] In certain embodiments, the neurodegenerative disease is Alzheimer’s disease, Huntington’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, Friedreich ataxia, Lewy body disease, spinal muscular atrophy , motor neuron disease, multiple sclerosis, Batten disease, Creutzfeldt-Jakob disease.

[0239] In certain embodiments, the infectious disease may be a viral, bacterial, fungal, yeast, protozoan, prion or parasitic disease, optionally wherein: (1) the viral disease is human immunodeficiency virus (HIV), hepatitis vims (optionally hepatitis A, B, or C virus), human papillomavirus (HPV), herpes simplex virus (HSV) (optionally HSV-1 or HSV-2), enterovirus, human cytomegalovirus, adenovirus, rhinovirus, Pox virus, Influenza virus, coronavirus (optionally MERS-CoV, SARS-CoV, or SARS-CoV-2, or common humancoronavirus), norovirus, West Nile Virus, Zika virus, poliovirus, Ebola virus, or dengue virus (DENV) infection; (2) the bacterial disease is Salmonella, Escherichia coll, Mycobacterium tuberculosis, methicillin-resistant staphylococcus aureus (MRSA), Clostridium difficile. Streptococcus pneumoniae, Klebsiella pneumoniae, Pseudomonas aeruginosa, Helicobacter pylori, Neisseria gonorrhoeae. Vibrio vulnificus; and / or (3) the fungal disease is Aspergillosis, Candida, Candida auris, Cryptococcus neoformans, Pneumocystis jirovecii. Mucoromycetes , Taloromyces. ringworm. Blastomyces. Coccidioides, Cryptococcus gattii. Histoplasma, Paracoccidioides, or Sporothrix infection.

[0240] In a further aspect, the disclosure provides methods of manufacturing any of the anti-human CD28 antibodies or antigen-binding antibody fragments described herein or the multi-specific antibodies described herein.

[0241] In some embodiments, the method may comprise: (a) culturing cells comprising any of the nucleic acids described herein in a condition that allows for expression of said antibody or antigen-binding antibody fragment or said multispecific antibody, and (b) harvesting and purifying the antibody or antigen-binding antibody fragment or the multispecific antibody from the cell culture from (a).

[0242] In a further aspect, the disclosure provides methods of manufacturing any of the isolated, recombinant, and / or host cells described herein or a population of such cells.

[0243] In some embodiments, the method may comprise introducing any of the nucleic acids described herein and / or any of the vectors described herein into one or more cells, optionally wherein the introducing occurs in vitro, ex vivo, or in vivo.

[0244] Any of the anti-human CD28 antibodies or antigen-binding antibody fragments according to the present disclosure or any of the multi-specific antibodies according to the present disclosure, any of the nucleic acids according to the present disclosure, any of the vectors according to the present disclosure, any of the isolated, recombinant, and / or host cells according to the present disclosure or a population of such cells, any of the compositions according to the present disclosure, may be for use in use in medicine or for use in the preparation of a medicament for use in medicine.

[0245] Any of the anti-human CD28 antibodies or antigen-binding antibody fragments according to the present disclosure or any of the multi-specific antibodies according to the present disclosure, any of the nucleic acids according to the present disclosure, any of the vectors according to the present disclosure, any of the isolated, recombinant, and / or host cells according to the present disclosure or a population of such cells, any of the compositions according to the present disclosure, may be for use in treating a disease, disorder, orcondition, optionally wherein the disease, disorder, or condition comprises any one or more of those described herein.

[0246] Any of the anti-human CD28 antibodies or antigen-binding antibody fragments according to the present disclosure or any of the multi-specific antibodies according to the present disclosure, any of the nucleic acids according to the present disclosure, any of the vectors according to the present disclosure, any of the isolated, recombinant, and / or host cells according to the present disclosure or a population of such cells, any of the compositions according to the present disclosure, may be for use in the manufacture of a medicament for treatment of a disease, disorder, or condition, optionally wherein the disease, disorder, or condition comprises any one or more of those described herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0247] FIG. 1-6 provide exemplary and non-limiting embodiments of various antibody, antigen-binding antibody fragment, and multi-specific antibody structures which may comprise any of the anti-CD28 antibody sequences disclosed herein. In FIGS. 1-6, the following rules applies unless otherwise indicated: (1) Each domain is presented as a rectangle with a text therein showing the domain name (e.g., CH3, VH. etc); (2) a set of multiple domains connected with each other represents a polypeptide (e.g., a heavy chain polypeptide, a light chain polypeptide, etc); (3) the direction of domains within a polypeptide is according to the direction of the text showing domain names, from the N-terminus to the C-terminus; (4) a linker or a hinge may be used between domains as necessary and a disulfide bond(s) may exist between polypeptides (and / or within a domain or within a polypeptide), perhaps to allow correct formation of the antigen-binding site(s), even when the FIGS do not explicitly show a linker, a hinge, or a disulfide bond; (5) any of the constant domain (e.g., CH1, CH2. and / or CH3 domain(s)) shown in FIGS may be omitted or replaced with another constant domain when possible and / or desired and, when appropriate, may be replaced with a hinge or a linker; (6) rectangles with no pattern (i.e., open) are domains which individually may comprise a corresponding wild-ty pe sequence or may comprise one or more amino acid substitutions relative to a wild- type sequence; (7) hinge and CH1, CH2, and CH3 domains may individually be of any (heavy chain) isolype; (8) when more than one hinges are present in a structure, the hinges may or may not be of the same isotype, when more than one CH1 domains are present in a structure, the CH1 domains may or may not be of the same isotype, when more than one CH2 domains are present in a structure, the CH2 domains may or maynot be of the same isotype, and when more than one CH3 domains are present in a structure, the CH3 domains may or may not be of the same isotype; (9) light chain constant (CL) domain may be is a kappa CL domain or a lambda CL domain; (10) when more than one CL domains are present in a structure, all CL domains may be kappa CLs or all CL domains may be lambda CLs, or alternatively at least one CL may be a kappa CL and at least one CL may be a lambda CL domain; (11) when both kappa and lambda CL domains are present, the CH1 domains paired to the CL domains may. in some instances, be variant CH1 domains, one of which may be a variant CH1 that preferentially binds to a kappa CL and another CH1 domain may be a variant CH1 that preferentially binds to a lambda CL (e.g., having kappa and lambda CLs and kappa-preferring CH1 and lambda-preferring CH1 in a molecule potentially allows for efficient manufacturing); (12) VH and VL domains paired with each other in FIGS form an antigen-binding site for an epitope; (13) in a given VH-VL pair, the VL may be omitted even if VL is shown in FIGS, if the VH alone gives sufficient specificity to a cognate antigen (e.g., nanobody); and (14) when there are more than one antigen-binding sites, the antigen-binding sites may all bind to the same epitope or at least one or more antigen-binding sites may bind to a different epitope.

[0248] FIGS. 1A-1J provide some exemplary and non-limiting embodiments of structures which may be comprised by or contained in (i) various anti-CD28 antibodies and antigen- binding antibody fragments and / or (ii) various antigen-binding regions (ABRs) which may be contained in multi-specific antibodies according to the present disclosure.

[0249] FIG. 1A provides some basic, exemplary antibody structures. The antibody on the left (boxed) is an exemplary, standard full-size antibody, in which hinges or disulfide bods are not explicitly shown. The boxed antibody may , for example, comprise a hinge between CH1 and CH2 and one or more disulfide bond(s) (dotted line(s)) may be present between the hinges and / or between CH1 and CL (center). Alternatively, the boxed antibody may, for example, comprise a hinge between CH1 and CH2 and one or more disulfide bond (dotted line(s)) may be present between hinges and / or between CL and hinge (right). Hinges and disulfide bonds, such as but not limited to those shown in middle and right antibody structures may be present, even if not explicitly shown, in any of the structures shown in FIGS and described herein.

[0250] FIG. 1B provides some variations of the boxed antibody structure provided in FIG. 1A and the description thereof. In some variants of the boxed antibody of FIG. 1A, VH and VL positions are swapped and / or CH1 and CL positions are swapped, relative to the boxedstructure of FIG. 1A. Variations equivalent to those shown in FIG. 1B (swapping VH-VL and / or swapping CH1 -CL positions) may be further applied to any of the structures shown in FIGS. 1-6 and the description thereof or variations thereof as appropriate, even if not explicitly shown.

[0251] FIG. 1C provides some variations of the boxed antibody structure provided in FIG. 1A and the description thereof. In some variants of the boxed antibody of FIG. 1A, any of the constant domains, even if shown in FIGS, may be omitted when possible and / or desired. For example, a CH3 domain(s) may be omitted (top row), a CH2 domain(s) may be omitted (middle row), and / or a CH1 and a CL domain(s) may be omitted (bottom row). Even when such constant domains may be omitted, ahinge(s) and / or a disulfide bond(s) may be present (e.g., center and right structures in each row) or a linker may be present to connect domains (e.g., an exemplary and optional linker shown with a square dotted line in left structure in the third and bottom rows). Variations equivalent to those shown in FIG. 1C (omitting one or more CH3, CH2, CH1, and / or CL domains) may be further applied to any of the structures shown in FIGS. 1-6 and the description thereof or variations thereof as appropriate, even if not explicitly shown.

[0252] FIG. 1D provides some variations of the boxed antibody structure provided in FIG. 1A and the description thereof. In some variants of the boxed antibody of FIG. 1A, any two or more of the constant domains, even if shown in FIGS, may be omitted when possible and / or desired. For example, CH1, CL, and CH2 domains may be omitted (top row), CD1, CL, and CH3 domains may be omitted (second row), CH2 and CH3 domains may be omitted (third row), and / or CH1, CH2, and CH3 domains may be omitted (bottom row). Even when such constant domains may be omitted, ahinge(s) and / or a disulfide bond(s) may be present (e.g., center and right structures in each row). The center and right structures of in the third row may be referred to as a F(ab’)2. Variations equivalent to those shown in FIG. 1D (omitting two or more of CH3, CH2, CH1, and / or CL domains) may be further applied to any of the structures shown in FIGS. 1-6 and the description thereof or variations thereof as appropriate, even if not explicitly shown.

[0253] FIG. 1E provides additional variations of the antibody structures. The present disclosure further encompasses the “half-antibody” variants of any of the antibody structures provided in FIGS. 1A-1D and the description thereof. The top left structure (boxed) is a “half-antibody” variant of the boxed antibody structure provided in FIG. 1A. In some variants of the boxed “half-antibody”, VH and VL positions are swapped and / or CH1 and CLpositions are swapped, relative to the boxed structure of FIG. 1A. In some variants of the boxed "half-antibody", a CH3 domain may be omitted (middle left), a CH2 domain may be omitted (middle row, second from the left), CH1 and CL domains may be omitted (middle row center), CH1, CH2, and CL domains may be omitted (middle row second from the right), or CH1, CH3, and CL domains may be omitted (middle row, right). In some variants of the boxed "half-antibody". CH2 and CH3 domains may be omitted (bottom left (boxed), which may be referred to as a fragment antigen-binding region (Fab)), or CH2 and CH3 domains may be omitted and a hinge or a portion thereof sufficiently long enough to provide a cysteine for a disulfide bond is present (bottom, second from the left, which may be referred to as a Fab’). A variant of a Fab structure may include one in which the CH1 and CL positions are swapped (bottom, second from the right). In some variants of the boxed "half- antibody". CH1, CH2, CH3, and CL domains may be omitted (bottom right), which may be referred to as a variable fragment (Fv). Variations equivalent to those shown in FIG. 1E (“half-antibody” variants, i.e., structures containing a monomer portion of a dimer (or a dimer portion of a tetramer, or the like) contained in a parent structure) may be further applied to any of the structures shown in FIGS. 1-6 and the description thereof or variations thereof as appropriate, even if not explicitly shown.

[0254] FIG. 1F provides further variations of the boxed antibody structure provided in FIG. 1A and the description thereof. In some variants of the boxed antibody of FIG. 1A, a VH and a VL may be placed in tandem wi thin a polypeptide, with or without a linker between the VH and the VL, in a direction from the N-terminus to the C-terminus or from the C-terminus to the N-terminus (top row. left and right, respectively). Such structures may be referred to as a single chain fragment variable region (scFv). In further variants, two or more of such scFvs may be placed in tandem within a polypeptide (middle row). Such structures may be referred to as a tandem scFv. Variants containing multiple scFvs may include a diabody, a triabody, and a tetrabody (bottom left, center, and right, respectively; each shown using the boxed scFv structure, but for example the VH-VL positions may be swapped).

[0255] FIG. 1G provides further variations of the boxed antibody structure provided in FIG. 1A or of the boxed scFv of FIG. 1F and the description thereof. Some structures may comprise a scFv in place of a VH-VL set of the boxed antibody structure provided in FIG. 1A. or a scFv may be placed at the N-terminus of a CH1 (e.g., top left), at the N-terminus of a CL (e.g., bottom left), at the C terminus of a CL (e.g.. bottom center), or at the C-terminus of a CH3 (e.g., bottom right), or a combination thereof. Although structures comprising twoscFvs are shown, some structures may comprise one scFv, two scFvs (e.g., top left (boxed) and bottom), three scFvs, four scFvs, or more scFvs (e.g.. five, six, seven, or eight scFvs). As noted above, one or more of the constant domains may be omitted. For example, CH1 and CL domains may be omitted (which structure may be referred to as a scFv-Fc), or either CH2 or CH3 domains may be further omitted (which structure may be referred to as a scFv-CH). Any of such structures in which an scFv is linked directly or indirectly (e.g.. via a hinge) to a CH domain paired with another CH domain may be referred to as a scFv-CH. Furthermore, also as noted above, “half-antibody” variants of any of the structures of FIG. 1G and the description thereof are further encompassed by the disclosure. Some structures may comprise two scFvs each attached to the N-terminus of or each attached to the C-terminus of dimeric polypeptides forming a leucine zipper (top row, center and right, respectively). Such structures may be referred to as scFv-zipper. In FIG. 1G, although structures using the boxed scFv of FIG. 1F are shown, structures using any scFvs or scFv variants such as but not limited to those in FIG. 1F (e.g., diabody-Fc and diabody-CH, in which the scFvs in scFv-Fc and scFv-CH, respectively, are replaced with diabodies) are also encompassed by the disclosure.

[0256] FIG. 1H provides further variations of the boxed antibody structure provided in FIG. 1A or of the boxed scFv of FIG. 1F and the description thereof. In some variants of the boxed antibody of FIG. 1A, a VH followed by a constant domain (e.g., CH1) and a VL followed by a constant domain (e.g., CL) may be placed in tandem within a polypeptide, with or without a linker between the VH followed by a constant domain and the VL followed by a constant domain, in a direction from the N-terminus to the C-terminus (top row; left (boxed) and second from the left) or from the C-terminus to the N-terminus (top row; third and fourth from the left). Such structures may be referred to as a single chain Fab (scFab). In further variants, tw o or more of any of such scFabs may be placed in tandem w ithin a polypeptide with or without a linker (e.g., top right). Such structures may be referred to as a tandem scFab. Variants containing multiple scFabs may include the structures in the bottom row, each of w hich is shown using the boxed scFab structure, but for example the VH-VL positions and / or the CH1 -CL positions may be swapped.

[0257] FIG. 1I provides further variations of the boxed antibody structure provided in FIG. 1A or of the boxed scFab of FIG. 1H and the description thereof. Some structures may comprise a scFab in place of a VH-VL set of the boxed antibody structure provided in FIG. 1A, or a scFab may be placed at the N-terminus of a CH1 (e.g., top left (boxed)), at the N-terminus of a CL (e.g., botom left), at the C terminus of a CL (e.g.. botom center), or at the C-terminus of a CH3 (e.g.. botom right), or a combination thereof. Although structures comprising two scFabs are shown, some structures may comprise one scFab, two scFabs (e.g., top left (boxed) and botom), three scFabs, four scFabs, or more scFabs (e.g., five, six, seven, or eight scFabs). As noted above, one or more of the constant domains may be omited. For example, CH1 and CL domains (that were present in the parent structure, i.e., boxed structure of FIG. 1A) may be omited (which structure may be referred to as a scFab- Fc), or either CH2 or CH3 domains may be further omited (which structure may be referred to as a scFab-CH). Also as noted above, “half-antibody” variants of any of the structures of FIG. 1I and the description thereof are further encompassed. Some structures may comprise two scFabs each atached to the N-terminus of or each atached to the C-terminus of dimeric polypeptides forming a leucine zipper (top row, center and right, respectively). Such structures may be referred to as scFab-zipper. In FIG. 1I, although structures using the boxed scFab of FIG. 1H are show n, structures using other scFabs and variants thereof such as but not limited to those in FIG. 1H are also encompassed.

[0258] FIG. 1J provides further variations of the boxed antibody structure provided in FIG. 1A or of structures provided in any of FIGS. 1A-1I and the description thereof. As noted above, a VL may be omited as long a VH alone gives sufficient specificity to a cognate antigen. Therefore, the present disclosure encompasses structures which are the same as any of the structures contained in FIGS. 1A-1I or the description thereof except that at least one VL (and optionally one or more CL domains) is omited. For example, some structures may comprise just a VH which is not paired with a VL (e.g.. top left, which may be referred to as a single domain antibody (sdAb) or a nanobody). In some structures, two or more of any of such sdAbs may be placed in tandem within a polypeptide with or without a linker (e.g., top right), which may be referred to as a tandem sdAb or a tandem nanobody. Some structures may comprise a sdAb in place of a VH-VL set of the boxed antibody structure provided in FIG. 1A. In some structures, a sdAb may be placed at the N-terminus of a CH1 (e.g., middle left). In some cases one or more of the CL domains may further be omited (e.g., middle row; second from the left), and in some cases the CH1 domain may further be omited, which structure may be referred to as a camel or camelid antibody (hinges are ty pically present). In some cases, a sdAb may be placed at the N-terminus of a CL (e.g., botom left), at the C terminus of a CL (e.g., botom center), or at the C-terminus of a CH3 (e.g., top row, second from the right; or one or more of the CL domains may further be omited (e.g., top right)), ora combination thereof. Although structures comprising two scFvs are shown, some structures may comprise one sdAb. two sdAbs, three sdAbs. four sdAbs, or more sdAbs (e.g., five, six. seven, or eight sdAbs). As noted above, one or more of the constant domains may be omitted. For example, CH1 and CL domains may be omitted (which structure may be referred to as a sdAb-Fc), or either CH2 or CH3 domains may be further omitted (which structure may be referred to as a sdAb-CH). Any of such structures may further comprise one or more additional constant domains. The bottom right structure may be referred to as an Immunoglobulin new antigen receptor (IgNAR), and its variants not comprising CH4 or CH5 domains are also encompassed by the disclosure. Also as noted above, “half-antibody” variants of any of the structures of FIG. 1 J and the description thereof are further encompassed. Any of the structures not containing a VL or a CL may be referred to as a heavy chain-only antibody (HCAb).

[0259] FIGS. 2-6 provide schematics and some exemplary and non-limiting embodiments of structures which may be comprised by or contained in antibodies comprising more than one antigen-binding regions (ABRs) such as multi-specific antibodies according to the present disclosure. In addition to the above-noted rules (1)-(14), the following rules applies unless otherwise indicated: (15) VH-A and VL-A form an antigen-binding site specific for antigen A or epitope A, VH-B and VL-B form an antigen-binding site for antigen B or epitope B, VH-C and VL-C form an antigen-binding site for antigen C or epitope C, VH-D and VL-D form an antigen-binding site for antigen D or epitope D, VH-E and VL-E form an antigenbinding site for antigen E or epitope E, VH-F and VL-F form an antigen-binding site for antigen F or epitope F. VH-G and VL-G form an antigen-binding site for antigen G or epitope G, VH-H and VL-H form an antigen-binding site for antigen H or epitope H, VH-I and VL-I form an antigen-binding site for antigen I or epitope I, and VH-J and VL-J form an antigen-binding site for antigen J or epitope J; (16) all of antigens A-J or epitopes A-J may be different from each other, or not all of antigens A-J or epitopes A-J may be different from each other; (17) stipe and dotted constant domains paired with each other (e.g., a set of CH1 and CL domains or a set of two CH3 domains) in FIGS may or may not be a set of constant domains one or both of which domains is / are engineered to promote preferential pairing between the constant domains of the set (e.g., over pairing with another constant domain); (18) two or more VL domains in dotted grid in a structure may or may not be common VLs (i.e., VLs having the same amino acid sequences); and two or more VL domains in solid grid in a structure may or may not be common VLs; and (19) when VL domains in dotted grid andVL domains in solid grid are both present, the VL domain(s) in dotted grid and the VL domain(s) in solid grid may or may not have the same amino acid sequences.

[0260] FIG. 2A provides a schematic of antigen-binding structures which bind to antigens A and B and / or epitopes A and B ("AB-A / B") which may be contained in antibodies, antigen- binding antibody fragments, and multispecific antibodies (e.g., bispecific antibodies). Such an AB-A / B comprises (1) an antigen-binding structure (AB-A) which comprises at least one antigen-binding region which binds to antigen A or epitope A (ABR-A) and (2) at least one antigen-binding region which binds to antigen B or epitope B (ABR-B). Antigens A and B may be same or different from each other, and epitopes A and B may be same or different from each other. Although eight ABR-Bs are shown, the structure may comprise one, any number of, such as one, two, three, four, or more (e.g., five, six, seven, or eight) ABR-Bs. In some cases, the AB-A and / or the ABR-A may comprise any one or more of the structures in FIGS. 1A-1J or the description thereof. In some cases, the ABR-B may comprise any one or more of the structures in FIGS. 1A-1J or the description thereof. The AB-A and the ABR-B may be associated with each other, optionally via one or more disulfide bonds, or linked to each other in any appropriate manner, optionally via a hinge or a linker. For example, the N- terminus or the C-terminus of a polypeptide contained in the ABR-B may be linked to the N- terminus or the C-terminus of a polypeptide contained in the AB-A.

[0261] FIGS. 2B-2E provide exemplary AB-A / B structures (encompassed by the structure of FIG. 2A and the description thereof) comprising: (1) an ABR-A having the structure of a full-size antibody which binds to antigen A or epitope A, comprising two sets of (a) a polypeptide (which may be called a heavy chain A) comprising a heavy chain variable domain A (VH-A) and a heavy chain constant region A (CH- A) (CH-A may comprise a heavy chain constant domain 1 A (CH1 -A), a hinge (hinge- A), a heavy chain constant domain 2 A (CH2-A), and / or a heavy chain constant domain 3 A (CH3-A)), from the N- terminus to the C-terminus and (b) a polypeptide (which may be called a light chain A) comprising a light chain variable domain A (VL-A) and a light chain constant domain A (CL- A) from the N-terminus to the C-terminus, wherein the heavy chain A and the light chain A are paired with each other, optionally via at least one disulfide bond (e.g., boxed structure of FIG. 1A); and (2) at least one ABR-B having the structure of a Fab w hich binds to antigen B or epitope B (Fab-B), comprising (a) a polypeptide (which may be called a heavy chain B) comprising a heavy chain variable domain B (VH-B) and a heavy chain constant region B (CH-B) (CH-B may comprise at least a heavy chain constant domain 1 B (CH1-B)), from theN-terminus to the C-terminus and (b) a polypeptide (which may be called a light chain B) comprising a light chain variable domain B (VL-B) and a light chain constant domain B (CL- B) from the N-terminus to the C-terminus (e.g., boxed Fab structure of FIG. 1E) wherein the heavy chain B and the light chain B are paired with each other, optionally via at least one disulfide bond. In FIGS. 2B-2E, both the heavy chain B and the light chain B of at least one Fab-B are linked to a heavy chain A and a light chain A, respectively, or a light chain A and a heavy chain A. respectively of AB-A.

[0262] FIG. 2B shows exemplary structures comprising one Fab-B. The C-terminus of the heavy chain B is attached to the N-terminus of a heavy A and the C-terminus of the light chain B is attached to the N-terminus of a light chain A paired with the heavy chain A (top left); the C-terminus of the light chain B is attached to the N-terminus of a heavy A and the C-terminus of the heavy chain B is attached to the N-terminus of a light chain A paired with the heavy chain A (top right); or the N-terminus of the heavy chain B is attached to the C- terminus of one heavy chain A and the N-terminus of light chain B is attached to the C- terminus of another heavy chain A (bottom).

[0263] FIG. 2C shows additional, exemplary structures comprising two Fab-Bs. In some structures, one Fab-B is attached to the N-terminus of one heavy and light chain A pair and the other Fab-B is attached to the N-terminus of the other heavy and light chain A pair (left three structures). In some structures, two Fab-Bs are attached in tandem to the C-terminus of two heavy chains A (center and right structures).

[0264] FIG. 2D shows additional, exemplary structures comprising two Fab-Bs. In some structures, two Fab-Bs are attached in tandem to the C-terminus of one heavy and light chain A pair.

[0265] FIG. 2E shows additional, exemplary structures comprising two Fab-Bs. In some structures, one Fab-B is attached to the N-terminus of one heavy and light chain A pair and the other Fab-B is attached to the C-terminus of two heavy chains A.

[0266] In FIGS. 2B-2E, although structures comprise one full-size antibody and one or two Fabs are shown, structures comprising any numbers of Fabs (e.g.. three, four, five, six. seven, eight, or more) are also encompassed by the disclosure. Furthermore, in FIGS. 2B-2E, although structures using the boxed full-size antibody structure of FIG. 1A and the Fab in the boxed Fab structure of FIG. 1E are shown, structures using other full-size antibody structures and variants thereof such as but not limited to those in FIGS. 1A-1E and the descriptionthereof (e.g., those with one or more domains omitted, those with domain positions swapped, and / or half-antibody variants) and / or using other Fab structures and variants thereof such as but not limited to those in FIG. 1E and the description thereof (e.g. those with one or more domains omitted (e.g., Fv, when both CH-B and CL-B are omitted), those with domain positions swapped, and / or those with a hinge (Fab’)) are also encompassed by the disclosure.

[0267] FIG. 2F provides a schematic of antibodies, antigen-binding antibody fragments, and multispecific antibodies (encompassed by the structure of FIG. 2A and the description thereof), which comprises (1) an AB- A which comprises at least one ABR-A having the structure of a full-size antibody which binds to antigen A or epitope A, comprising two sets of (a) a polypeptide (which may be called a heavy chain A) comprising a VH-A and a CH-A (CH-A may comprise a CH1-A, a hinge-A, a CH2-A, and / or a CH3-A), from the N-terminus to the C-terminus and (b) a polypeptide (which may be called a light chain A) comprising a VL-A and a CL- A from the N-terminus to the C-terminus, wherein the heavy chain A and the light chain A are paired with each other, optionally via at least one disulfide bond (e.g., boxed structure of FIG. 1A) and (2) one or more ABR-Bs.

[0268] Each of the one or more ABR-Bs may have the structure of: (i) a Fab-B as described above in relation to FIGS. 2B-2E; (ii) a Fv which binds to antigen B or epitope B (Fv-B), comprising (a) a polypeptide (which may be called a heavy chain B) comprising a VH-B and (b) a polypeptide (which may be called a light chain B) comprising a VL-B (e.g.. bottom right structure of FIG. 1E) wherein the heavy chain B and the light chain B are paired with each other, optionally via at least one disulfide bond; (iii) a scFv which binds to antigen B or epitope B (scFv-B), comprising (a) a VH-B, (b) an optional linker, and (c) a VL-B. from the N-terminus to the C-terminus (e.g., boxed structure of FIG. 1F); (iv) a scFab which binds to antigen B or epitope B (scFab-B), comprising (a) a VH-B, (b) a CH-B (CH-B may comprise at least a CH1-B), (c) an optional linker, (d) a VL-B, and (e) a CL-B, from the N-terminus to the C-terminus (e.g., boxed structure of FIG. 1H); or (v) a sdAb which binds to antigen B or epitope B (sdAb-B) comprising a VH-B. In case of (a) and (b) (i.e.. Fab-B and Fv-B), either the heavy chain B or the light chain B is linked to a heavy chain A or a light chain A of AB- A. In case of (c)-(e) (i.e., scFv-B, scFab-B, and sdAb-B) the N-terminus or the C-terminus of the ABR-B is linked to a heavy chain A or a light chain A of AB-A.

[0269] Additionally, structures using (1) a ABR-A having another full-size antibody structure or a variant thereof such as but not limited to those in FIGS. 1A-1E and the description thereof (e.g., those with one or more domains omitted, those with domain positions swapped,and / or half-antibody variants) and / or using (2) a ABR-B having (a) another Fab structure or a variant thereof such as but not limited to those in FIG. 1E and the description thereof (e.g. those with one or more domains omitted, those with domain positions swapped, and / or those with a hinge (Fab’)); (b) another Fv structure or variant thereof; (c) another scFv-containing structure or a variant thereof such as but not limited to those in FIGS. IF and 1G and the description thereof (e.g. those with one or more domains added, one or more domains omitted, and / or domain positions swapped); (d) another scFab structure or a variant thereof such as but not limited to those in FIGS. 1H and II and the description thereof (e.g. those with one or more domains added, one or more domains omitted, and / or domain positions swapped); or (e) a sdAb structure or a variant thereof such as but not limited to those in FIG. 1J and the description thereof (e.g. those with one or more domains added, one or more domains omitted, and / or domain positions swapped) are further encompassed by the disclosure.

[0270] Furthermore, although eight ABR-Bs are shown, the structure may comprise one, any number of, such as one, two, three, four, or more (e.g., five, six, seven, or eight) ABR-Bs. When two or more ABR-Bs are present, the structure of the ABR-Bs may be all the same (e.g., all scFvs) or one or more of the ABR-Bs have different structures (e.g.. scFv and Fab).

[0271] FIGS. 2G-2I provide exemplary structures (encompassed by the structure of FIG. 2A and the description thereof) comprising: (1) an ABR-A having the structure of a halfantibody variant of a full-size antibody (e.g., any of the full-size antibodies in FIGS. 1A-1B) which binds to antigen A or epitope A, the half-antibody variant comprising (a) a polypeptide (which may optionally be called a heavy chain A) comprising a VH-A and (b) a polypeptide (which may optionally be called a light chain A) comprising a VL-A. wherein the heavy chain A and the light chain A are paired with each other, optionally via at least one disulfide bond; and (2) an ABR-B having the structure of a half-antibody variant of a full-size antibody (e.g., any of the full-size antibodies in FIGS. 1A-1B) which binds to antigen B or epitope B, the half-antibody variant comprising (a) a polypeptide (which may optionally be called a heavy chain B) comprising a VH-B and (b) a polypeptide (which may optionally be called a light chain B) comprising a VL-B, wherein the ABR-A and the ABR-B are paired with each other, optionally via at least one disulfide bond.

[0272] In FIG. 2G, the top (boxed) structure comprises (1) an ABR-A having the structure of a half-antibody as shown in the top left (boxed) structure of FIG. 1E, which binds to antigen A or epitope A (half-antibody A), the half-antibody A comprising (a) a polypeptide (whichmay be called a heavy chain A) comprising a VH-A and a CH-A (CH-A may comprise a CH1-A, a hinge-A. a CH2-A, and / or a CH3-A), from the N-terminus to the C-terminus and (b) a polypeptide (which may be called a light chain A) comprising a VL-A and a CL-A, wherein the heavy chain A and the light chain A are paired with each other, optionally via at least one disulfide bond; and (2) an ABR-B having the structure of a half-antibody as show n in the top left (boxed) structure of FIG. 1E, which binds to antigen B or epitope B (halfantibody B), the half-antibody B comprising (a) a polypeptide (which may be called a heavy chain B) comprising a VH-B and a CH-B (CH-B may comprise a CH1-B, a hinge-B, a CH2- B, and / or a CH3-B), from the N-terminus to the C-terminus and (b) a polypeptide (which may be called a light chain B) comprising a VL-B and a CL-B, wherein the heavy' chain B and the light chain B are paired with each other, optionally via at least one disulfide bond, wherein the ABR-A and the ABR-B are paired with each other, optionally via at least one disulfide bond. In the bottom three structures, one or more of the paired VH-VL positions are swapped relative to the boxed structure.

[0273] In FIG. 2H, in the top three structures, one or more of the paired CH1 -CL positions are swapped relative to the boxed structure of FIG. 2G. In the bottom three structures, one or more of the paired CH1 -CL positions are swapped relative to the bottom left structure of FIG. 2G

[0274] In FIG. 21. in the top three structures, one or more of the paired CH1-CL positions are swapped relative to the bottom center structure of FIG. 2G. In the bottom three structures, one or more of the paired CH1-CL positions are sw apped relative to the bottom right structure of FIG. 2G.

[0275] Additionally, in relation to FIGS. 2G-2I, structures using (1) a ABR-A having another half-antibody structure or a variant thereof such as but not limited to those in FIG. 1E and the description thereof (e.g.. those with one or more domains omitted, those with domain positions swapped, and / or one or more domains added) and / or using (2) a ABR-B having another half-antibody structure or a variant thereof such as but not limited to those in FIG. 1E and the description thereof (e.g., those with one or more domains omitted, those with domain positions swapped, and / or one or more domains added) are further encompassed by the disclosure.

[0276] FIGS. 2J-2K provide exemplary structures (encompassed by the structure of FIG. 2A and the description thereof) comprising: (1) an ABR-A having the structure of a half-antibody variant of any of the structures in FIGS. 1G and II and the description thereof, which binds to antigen A or epitope A; and (2) an ABR-B having the structure of a halfantibody variant of any of the structures in FIGS. 1G and II and the description thereof, which binds to antigen B or epitope B, wherein the ABR-A and the ABR-B are paired with each other, optionally via at least one disulfide bond.

[0277] In FIG.2J, the top (boxed) structure comprises: (1) an ABR-A having the structure of a half-antibody variant of the top left structure of FIGS. 1G, which binds to antigen A or epitope A, the half-antibody variant comprising (a) a polypeptide (which may optionally be called a heavy chain A) comprising a scFv-A and a CH-A (CH-A may comprise a CH1-A, a hinge- A, a CH2-A, and / or a CH3-A) and optionally (b) a polypeptide (which may optionally be called a light chain A) comprising a CL- A, wherein the heavy chain A and the light chain A if present are paired with each other, optionally via at least one disulfide bond; and (2) an ABR-B having the structure of a half-antibody variant of the top left structure of FIGS. 1G, which binds to antigen B or epitope B, the half-antibody variant comprising (a) a polypeptide (which may optionally be called a heavy chain B) comprising a scFv-B and a CH-B (CH-B may comprise a CH1-B, a hinge-B, a CH2-B, and / or a CH3-B) and optionally (b) a polypeptide (which may optionally be called a light chain B) comprising a CL-B, wherein the heavy chain B and the light chain B if present are paired with each other, optionally via at least one disulfide bond. Some variants of the boxed structure, in which one or more of the paired VH-VL positions are swapped relative to the boxed structure are also shown (top, other than the boxed). Alternatively, the ABR-A and / or the ABR-B may individually comprise a half-antibody variant of any of the structures of FIGS. 1G, instead of a halfantibody variant of the top left structure of FIGS. 1G. Some of such variants include but are not limited to the bottom four structures.

[0278] In FIG.2K, the top (boxed) structure comprises: (1) an ABR-A having the structure of a half-antibody variant of the top left structure of FIGS. II, which binds to antigen A or epitope A, the half-antibody variant comprising (a) a polypeptide (which may optionally be called a heavy chain A) comprising a scFab-A and a CH-A (CH-A may comprise a CH1 -A, a hinge- A, a CH2-A, and / or a CH3-A) and optionally (b) a polypeptide (which may optionally be called a light chain A) comprising a CL- A, wherein the heavy chain A and the light chain A if present are paired with each other, optionally via at least one disulfide bond; and (2) an ABR-B having the structure of a half-antibody variant of the top left structure of FIGS. II, which binds to antigen B or epitope B, the half-antibody variant comprising (a) a polypeptide(which may optionally be called a heavy chain B) comprising a scFab-B and a CH-B (CH-B may comprise a CH1-B, a hinge-B, a CH2-B, and / or a CH3-B) and optionally (b) a polypeptide (which may optionally be called a light chain B) comprising a CL-B, wherein the heavy chain B and the light chain B if present are paired with each other, optionally via at least one disulfide bond. Some variants of the boxed structure, in which one or more of the paired VH-VL positions are swapped relative to the boxed structure are also shown (top, other than the boxed). Alternatively, the ABR-A and / or the ABR-B may individually comprise a half-antibody variant of any of the structures of FIGS. II, instead of a halfantibody variant of the top left structure of FIGS. II. Some of such variants include but are not limited to the bottom three structures.

[0279] Additionally, in relation to FIGS. 2J-2K, structures using (1) a ABR-A having another half-antibody structure or a variant thereof such as but not limited to those in FIGS. 1G and II and the description thereof (e.g.. those with one or more domains omitted, those with domain positions swapped, and / or one or more domains added) and / or using (2) a ABR- B having another half-antibody structure or a variant thereof such as but not limited to those in FIGS. 1G and II and the description thereof (e.g., those with one or more domains omitted, those with domain positions swapped, and / or one or more domains added) are further encompassed by the disclosure.

[0280] FIGS. 2L-2M provide additional exemplary structures (encompassed by the structure of FIG. 2A and the description thereof) which comprise a structurally asymmetric format.

[0281] In FIG. 2L, the top left structure comprises: (1) an ABR-A having the structure of a half-antibody variant of the top left structure of FIG. 1G, which binds to antigen A or epitope A; and (2) an ABR-B having the structure of a half-antibody variant of the top structure of FIG. 2G, which binds to antigen B or epitope B, wherein the ABR-A and the ABR-B are paired with each other, optionally via at least one disulfide bond. In some cases, the CL-A and / or CH1 -A may be omitted. In the top right structure, the pair of CH1 -A and CL-A is omitted. The bottom left structure comprises: (1) an ABR-A which binds to antigen A or epitope A having the same structure as a half-antibody variant of the top (boxed) structure of FIG. 2G, except that the VL-A is omitted (VH-A) is sufficient for binding to antigen A or epitope A; and (2) an ABR-B which binds to antigen B or epitope B having the structure of a half-antibody variant of the top (boxed) structure of FIG. 2G, wherein the ABR-A and the ABR-B are paired with each other, optionally via at least one disulfide bond. In some cases,the CL- A and / or CH1 -A may be omitted. In the top right structure, the pair of CH1 -A and CL-A is omitted.

[0282] In FIG. 2M, the top left structure comprises: (1) an ABR-A having the structure of a half-antibody variant of the top left structure of FIG. 1G. which binds to antigen A or epitope A; and (2) an ABR-B which binds to antigen B or epitope B having the same structure as a half-antibody variant of the top (boxed) structure of FIG. 2G, except that the VL-B is omitted (VH-B) is sufficient for binding to antigen B or epitope B, wherein the ABR-A and the ABR-B are paired with each other, optionally via at least one disulfide bond. In some cases, one or more of the CL-A, CH1-A, CL-B, and / or CH1-B may be omitted (e.g., the first and second structures from the left of the middle and bottom rows). The top right structure comprises: (1) an ABR-A which binds to antigen A or epitope A having the same structure as a half-antibody variant of the top (boxed) structure of FIG.2G. except that the VL-A is omitted (VH-A) is sufficient for binding to antigen A or epitope A; and (2) an ABR-B which binds to antigen B or epitope B having the same structure as a half-antibody variant of the top (boxed) structure of FIG. 2G, except that the VL-B is omitted (VH-B) is sufficient for binding to the antigen B or epitope B, wherein the ABR-A and the ABR-B are paired with each other, optionally via at least one disulfide bond. In some cases, one or more of the CL-A, CH1-A, CL-B, and / or CH1-B may be omitted (e.g., the first and second structures from the right of the middle and bottom rows).

[0283] Structures of antibodies (e.g., multispecific antibodies) having a structurally asymmetric format are not limited to those shown in FIGS. 2L-2M and the descriptions thereof but many other structures are possible, for example those comprising (1) an ABR-A which binds to antigen A or epitope A having the structure of a half-antibody variant of any of the structures shown in FIGS. 1 and 2A-2K and the descriptions thereof; and (2) an ABR- B which binds to antigen B or epitope B having the structure of a half-antibody variant of another structure of the structures shown in FIGS. 1 and 2A-2K and the descriptions thereof, wherein the ABR-A and the ABR-B are paired with each other, optionally via at least one disulfide bond. Antibodies, antigen-binding antibody fragments, and multispecific antibodies having any of such structures are also encompassed by the disclosure herein.

[0284] FIG. 3A provides a schematic of antigen-binding structures which bind to antigens A,B, and C and / or epitopes A, B, and C (“AB-A / B / C”) which may be contained in antibodies, antigen-binding antibody fragments, and multispecific antibodies (e.g., bispecific or trispecific antibodies). Such an AB-A / B / C comprises (1) an antigen-binding structure (AB-A / B) which comprises at least one ABR-A and at least one ABR-B; and (2) at least one antigen-binding region which binds to antigen C or epitope C (ABR-C), comprising a heavy chain variable domain C (VH-C) and optionally a light chain variable domain (VL-C). One or more of antigens A, B, and C may be same or different from each other, and one or more of epitopes A, B, and C may be same or different from each other. Although eight ABR-Cs are shown, the structure may comprise one, any number of, such as one, two, three, four, or more (e.g.. five, six, seven, or eight) ABR-Cs. In some cases, the AB-A and / or the ABR-A may comprise any one or more of the structures in FIGS. 1A-1J or the description thereof. In some cases, the ABR-B may comprise any one or more of the structures in FIGS. 1A-1J or the description thereof. In some cases, the AB-A / B may comprise any one or more of the structures in FIGS. 2A-2K or the description thereof. In some cases, the ABR-C may comprise any one or more of the structures in FIGS. 1A-1J or the description thereof. The AB-A / B and the ABR-C may be associated with each other, optionally via one or more disulfide bonds, or linked to each other in any appropriate manner, optionally via a hinge or a linker. For example, the N-terminus or the C-terminus of a polypeptide contained in the ABR-C may be linked to the N-terminus or the C-terminus of a polypeptide contained in the AB-A / B.

[0285] FIG. 3B provides a schematic of exemplary antibodies, antigen-binding antibody fragments, and multispecific antibodies (encompassed by the structure of FIG. 3A and the description thereof), which comprises (1) an AB-A / B which comprises the boxed structure of FIG. 2G and (2) one or more ABR-Cs (in tandem or linked at separate sites of the AB-A / B).

[0286] Each of the one or more ABR-Cs may have the structure of: (i) a Fab which binds to antigen C (Fab-C). comprising (a) a polypeptide (which may be called a heavy chain C) comprising a heavy chain variable domain C (VH-C) and a heavy chain constant region C (CH-C) (CH-C may comprise at least a heavy chain constant domain 1 C (CH1-C)), from the N-terminus to the C-terminus and (b) a polypeptide (which may be called a light chain C) comprising a light chain variable domain C (VL-C) and a light chain constant domain C (CL- C) from the N-terminus to the C-terminus (e.g., boxed Fab structure of FIG. 1E) wherein the heavy chain C and the light chain C are paired with each other, optionally via at least one disulfide bond; (ii) a Fv which binds to antigen C or epitope C (Fv-C), comprising (a) a polypeptide (which may be called a heavy chain C) comprising a VH-C and (b) a polypeptide (which may be called a light chain C) comprising a VL-C (e.g.. bottom right structure of FIG. 1E) wherein the heavy chain C and the light chain C are paired with each other.optionally via at least one disulfide bond; (iii) a scFv which binds to antigen C or epitope C (scFv-C), comprising (a) a VH-C, (b) an optional linker, and (c) a VL-C, from the N-terminus to the C-terminus (e.g., boxed structure of FIG. 1F); (iv) a scFab which binds to antigen C or epitope C (scFab-C), comprising (a) a VH-C, (b) a CH-C (CH-C may comprise at least a CH1-C), (c) an optional linker, (d) a VL-C, and (e) a CL-C, from the N-terminus to the C- terminus (e.g., boxed structure of FIG. 1H); or (v) a sdAb which binds to antigen C or epitope C (sdAb-C) comprising a VH-C. In case of (i) and (ii) (i.e.. Fab-C and Fv-C), either the heavy chain C or the light chain C is linked to a heavy chain A or a light chain A and / or a heavy chain B or a light chain B of AB-A / B; or the heavy chain C and the light chain C are linked to a heavy chain A and a light chain A, respectively or a light chain A and a heavy chain A, respectively, and / or a heavy chain B and a light chain B. respectively, or a light chain B and a heavy chain B, respectively. In case of (iii)-(v) (i.e., scFv-C, scFab-C, and sdAb-C) the N-terminus or the C-terminus of the ABR-C is linked to a heavy chain A, a light chain A, a heavy chain B, and / or a light chain B of AB-A / B.

[0287] Additionally, structures using (1) a ABR-A / B having another full-size antibody structure or a variant thereof such as but not limited to those in FIGS. 2A-2M and the description thereof (e.g.. those with one or more domains omitted, those with domain positions swapped, and / or half-antibody variants) and / or using (2) a ABR-C having (a) another Fab structure or a variant thereof such as but not limited to those in FIG. 1E and the description thereof (e.g. those with one or more domains omitted, those with domain positions swapped, and / or those with a hinge (Fab’)); (b) another Fv structure or variant thereof; (c) another scFv-containing structure or a variant thereof such as but not limited to those in FIGS. 1F and 1G and the description thereof (e.g. those with one or more domains added, one or more domains omitted, and / or domain positions swapped); (d) another scFab structure or a variant thereof such as but not limited to those in FIGS. 1H and 1I and the description thereof (e.g. those with one or more domains added, one or more domains omitted, and / or domain positions sw apped); or (e) a sdAb structure or a variant thereof such as but not limited to those in FIG. 1J and the description thereof (e.g. those with one or more domains added, one or more domains omitted, and / or domain positions swapped) are further encompassed by the disclosure.

[0288] Furthermore, although eight ABR-Cs are shown, the structure may comprise one, any number of. such as one, two. three, four, or more (e.g., five, six, seven, or eight) ABR-Cs.When two or more ABR-Cs are present, the structure of the ABR-Cs may be all the same (e.g., all scFvs) or one or more of the ABR-Cs have different structures (e.g.. scFv and Fab).

[0289] FIG. 4A provides a schematic of antigen-binding structures which bind to antigens A, B, C. and D and / or epitopes A, B, C, and D (“AB-A / B / C / D ’) which may be contained in antibodies, antigen-binding antibody fragments, and multispecific antibodies (e.g., bispecific, trispecific, or tetraspecific antibodies). Such an AB-A / B / C / D comprises (1) an antigenbinding structure (AB-A / B / C) which comprises at least one ABR-A, at least one ABR-B, and at least one ABR-C; and (2) at least one antigen-binding region which binds to antigen D or epitope D (ABR-D) comprising a heavy chain variable domain D (VH-D) and optionally a light chain variable domain (VL-D). One or more of antigens A, B, C, and D may be same or different from each other, and one or more of epitopes A, B, C, and D may be same or different from each other. Although eight ABR-Ds are shown, the structure may comprise one, any number of, such as one, two. three, four, or more (e.g.. five. six. seven, or eight) ABR-Ds. In some cases, the AB-A and / or the ABR-A may comprise any one or more of the structures in FIGS. 1A-1J or the description thereof. In some cases, the ABR-B may comprise any one or more of the structures in FIGS. 1A-1J or the description thereof. In some cases, the ABR-C may comprise any one or more of the structures in FIGS. 1A-1J or the description thereof. In some cases, the AB-A / B / C may comprise any one or more of the structures according to FIGS. 3A-3B or the description thereof. In some cases, the ABR-D may comprise any one or more of the structures in FIGS. 1A-1J or the description thereof. The AB-A / B / C and the ABR-D may be associated with each other, optionally via one or more disulfide bonds, or linked to each other in any appropriate manner, optionally via a hinge or a linker. For example, the N-terminus or the C-terminus of a polypeptide contained in the ABR-D may be linked to the N-terminus or the C-terminus of a polypeptide contained in the AB-A / B / C.

[0290] FIG. 4B provides a schematic of exemplary antibodies, antigen-binding antibody fragments, and multispecific antibodies (encompassed by the structure of FIG. 4A and the description thereof), which comprises (1) an AB-A / B which comprises the boxed structure of FIG. 2G, (2) one or more ABR-Cs (in tandem or linked at separate sites of the AB-A / B), and (3) one or more ABR-Ds (in tandem or linked at separate sites of the AB-A / B).

[0291] Each of the one or more ABR-Cs may have the structure as described in FIG. 3B. Each of the one or more ABR-Ds may have the structure of: (i) a Fab w hich binds to antigen D (Fab-D). comprising (a) a polypeptide (which may be called a heavy chain D) comprising aheavy chain variable domain D (VH-D) and a heavy chain constant region D (CH-D) (CH-D may comprise at least a heavy chain constant domain 1 D (CH1-D)), from the N-terminus to the C-terminus and (b) a polypeptide (which may be called a light chain D) comprising a light chain variable domain D (VL-D) and a light chain constant domain D (CL-D) from the N-terminus to the C-terminus (e.g., boxed Fab structure of FIG. 1E) wherein the heavy chain D and the light chain D are paired with each other, optionally via at least one disulfide bond; (ii) a Fv which binds to antigen D or epitope D (Fv-D), comprising (a) a polypeptide (which may be called a heavy chain D) comprising a VH-D and (b) a polypeptide (which may be called a light chain D) comprising a VL-D (e.g., bottom right structure of FIG. 1E) wherein the heavy chain D and the light chain D are paired with each other, optionally via at least one disulfide bond; (iii) a scFv which binds to antigen D or epitope D (scFv-D), comprising (a) a VH-D, (b) an optional linker, and (c) a VL-D, from the N-terminus to the C-terminus (e.g., boxed structure of FIG. 1F); (iv) a scFab which binds to antigen D or epitope D (scFab-D), comprising (a) a VH-D, (b) a CH-D (CH-D may comprise at least a CH1-D), (c) an optional linker, (d) a VL-D. and (e) a CL-D, from the N-terminus to the C-terminus (e.g., boxed structure of FIG. 1H); or (v) a sdAb which binds to antigen D or epitope D (sdAb-D) comprising a VH-D. For Fab-C and Fv-C, either the heavy chain C or the light chain C is linked to a heavy chain A or a light chain A; or the heavy chain C and the light chain C are linked to a heavy chain A and a light chain A, respectively or a light chain A and a heavychain A, respectively. For Fab-D and Fv-D, either the heavy chain D or the light chain D is linked to a heavy chain B or a light chain B; or the heavy chain D and the light chain D are linked to a heavy chain B and a light chain B, respectively or a light chain B and a heavychain B, respectively. For scFv-C, scFab-C, and sdAb-C, the N-terminus or the C-terminus of the ABR-C is linked to a heavy chain A and / or a light chain A. For scFv-D, scFab-D, and sdAb-D, the N-terminus or the C-terminus of the ABR-D is linked to a heavy chain B and / or a light chain B.

[0292] Additionally, structures using (1) a ABR-A / B having another full-size antibody structure or a variant thereof such as but not limited to those in FIGS. 2A-2M and the description thereof (e.g., those with one or more domains omitted, those with domain positions swapped, and / or half-antibody variants) and / or using (2) a ABR-C and / or (3) a ABR-D, having (a) another Fab structure or a variant thereof such as but not limited to those in FIG. 1E and the description thereof (e.g. those with one or more domains omitted, those with domain positions swapped, and / or those with a hinge (Fab’)); (b) another Fv structure orvariant thereof; (c) another scFv-containing structure or a variant thereof such as but not limited to those in FIGS. IF and 1G and the description thereof (e.g. those with one or more domains added, one or more domains omitted, and / or domain positions swapped); (d) another scFab structure or a variant thereof such as but not limited to those in FIGS. 1H and II and the description thereof (e.g. those with one or more domains added, one or more domains omitted, and / or domain positions swapped); or (e) a sdAb structure or a variant thereof such as but not limited to those in FIG. 1J and the description thereof (e.g. those with one or more domains added, one or more domains omitted, and / or domain positions swapped) are further encompassed by the disclosure.

[0293] Furthermore, although four ABR-Cs and four ABR-Ds are shown, the structure may comprise one, any number of, such as one, two, three, four, or more (e.g., five, six, seven, or eight) ABR-Cs and / or one, any number of, such as one, two, three, four, or more (e.g., five, six. seven, or eight) ABR-Ds. When two or more ABR-Cs are present, the structure of the ABR-Cs may be all the same (e.g., all scFvs) or one or more of the ABR-Cs have different structures (e.g., scFv and Fab). When two or more ABR-Ds are present, the structure of the ABR-Ds may be all the same (e.g., all scFvs) or one or more of the ABR-Ds have different structures (e.g., scFv and Fab). Furthermore, the structure of the ABR-C(s) and the ABR-D(s) may or may not be the same.

[0294] FIG. 4C provides a schematic of further exemplary antibodies, antigen-binding antibody fragments, and multispecific antibodies (encompassed by the structure of FIG.4A and the description thereof), which comprises (1) an Fc region of an Ig molecule, comprising two heavy chains each comprising at least CH2 and CH3 domains, (2) one or more ABR-As (if two or more, in tandem or linked to separate sites of the Fc). (3) one or more ABR-Bs (if two or more, in tandem or linked at separate sites of the Fc), (4) one or more ABR-Cs (if two or more, in tandem or linked to separate sites of the Fc), and (5) one or more ABR-Ds (if two or more, in tandem or linked at separate sites of the Fc).

[0295] Each of the one or more ABR-As may have the structure of: (i) a Fab-A, as described above; (ii) a Fv-A, as described above; (iii) a scFv-A, as described above; (iv) a scFab- A, as described above; or (v) a sdAb-A, as described above. Each of the one or more ABR-Bs may have the structure of: (i) a Fab-B, as described above; (ii) a Fv-B, as described above; (iii) a scFv-B, as described above; (iv) a scFab-B, as described above; or (v) a sdAb-B, as described above. Each of the one or more ABR-Cs may have the structure of: (i) a Fab-C, as described above; (ii) a Fv-C, as described above; (iii) a scFv-C, as described above; (iv) a scFab-C, asdescribed above; or (v) a sdAb-C, as described above. Each of the one or more ABR-Ds may have the structure of: (i) a Fab-D, as described above; (ii) a Fv-D, as described above; (iii) a scFv-D, as described above; (iv) a scFab-D, as described above; or (v) a sdAb-D, as described above. For any of ABR-As, ABR-Bs, ABR-Cs, ABR-Ds, in case of (i) and (ii) (i.e., Fab and Fv), either the heavy chain or the light chain of the Fab or Fv is linked to a heavy chain (optionally the N-terminus or the C-terminus of the heavy’ chain) of the Fc; or the heavy chain and the light chain of the Fab or Fv are linked to one heavy chain and the other heavy chain, respectively, of the Fc. For any of ABR-As, ABR-Bs, ABR-Cs, ABR-Ds, in case of scFv, scFab, and sdAb, the N-terminus or the C-terminus of the scFv, scFab, or sdAb, is linked to a heavy chain (optionally the N-terminus or the C-terminus of the heavy chain) of the Fc.

[0296] For a Fab, any Fab structure or a variant thereof such as but not limited to those in FIG. 1E and the description thereof (e.g. those with one or more domains omitted, those with domain positions swapped, and / or those with a hinge (Fab’)) may be used. For a Fv, any Fv structure or variant thereof may be used. For a scFv, any scFv-containing structure or a variant thereof such as but not limited to those in FIGS. IF and 1G and the description thereof (e.g. those with one or more domains added, one or more domains omitted, and / or domain positions swapped) may be used. For a scFab, any scFab structure or a variant thereof such as but not limited to those in FIGS. 1H and II and the description thereof (e.g. those with one or more domains added, one or more domains omitted, and / or domain positions swapped) may be used. For a sdAb, any sdAb structure or a variant thereof such as but not limited to those in FIG. 1J and the description thereof (e.g. those with one or more domains added, one or more domains omitted, and / or domain positions swapped) may be used.

[0297] Furthermore, although one ABR-A, one ABR-B, one ABR-C, and one ABR-D are shown, the structure may comprise one, any number of, such as one, two, three, four, or more (e.g., five, six, seven, or eight) of ABR-A, ABR-B, ABR-C, and ABR-D. When two or more of a given ABR (ABR-A, ABR-B. ABR-C, or ABR-D) are present, the structure of the two or more of the ABRs may be all the same (e.g., all scFvs) or one or more of the ABRs have different structures (e.g., scFv and Fab). When tw o or more of a given ABR (ABR-A, ABR- B, ABR-C, or ABR-D) are present, the ABRs may be placed in tandem, one of which is linked to at least one heavy chain of the Fc, or at least two of the ABRs may be linked to separate sites of the Fc.

[0298] FIGS. 5A-5N provide various exemplary structures (encompassed by the structures of FIGS. 2, 3, and 4 and the description thereof), especially those comprising the core structure of any of the structures in FIG. 2G-2K and the description thereof.

[0299] In FIG. 5A, the structures comprise: (1) the core structure (AR-A / B) according to the boxed structure of FIG. 2G; (2) an ABR-C having the structure of a Fv which binds to antigen C or epitope C (Fv-C), comprising (a) a polypeptide (which may be called a heavy chain C) comprising a VH-C and (b) a polypeptide (which may be called a light chain C) comprising a VL-C (e.g., bottom right structure of FIG. 1E) wherein the heavy chain C and the light chain C are paired with each other, optionally via at least one disulfide bond: and (3) an ABR-D having the structure of a Fv which binds to antigen D or epitope D (Fv-D), comprising (a) a polypeptide (which may be called a heavy chain D) comprising a VH-D and (b) a polypeptide (which may be called a light chain D) comprising a VL-D (e.g., bottom right structure of FIG. 1E) wherein the heavy chain D and the light chain D are paired with each other, optionally via at least one disulfide bond. Although the Fv-C and Fv-D are placed at the N-terminus of the heavy and light chains A and the heavy and light chains B, respectively of the core structure (AR-A / B) in FIG. 5A, structures in which the Fv-C and Fv- D are placed at the C-terminus of heavy chains A and B of the core structure (AR-A / B) are also encompassed by the disclosure. Although not explicitly depicted, variants in which the core structure (AR-A / B) comprises any of the structures in FIG. 2G-2K are encompassed. Furthermore, variants in which one or more of ABR-A, ABR-B, ABR-C, and / or ABR-D are omitted are also encompassed.

[0300] In FIG. 5B, the structures comprise: (1) the core structure (AB-A / B / C / D) according to the top left structure of FIG. 5A; (2) an ABR-E having the structure of a Fv which binds to antigen E or epitope C (Fv-E), comprising (a) a polypeptide (which may be called a heavy chain E) comprising a VH-E and (b) a polypeptide (which may be called a light chain E) comprising a VL-E (e.g.. bottom right structure of FIG. 1E) wherein the heavy chain E and the light chain E are paired with each other, optionally via at least one disulfide bond. The heavy chain E and the light chain E are placed at the C-terminus of the heavy chain A and the heavy chain B, respectively (left structure), or at the C-terminus of the heavy' chain B and the heavy chain A, respectively (right structure), of the core structure. Although not explicitly depicted, variants in which the core structure (AR-A / B / C / D) comprises any of the structures in FIG. 5A are further encompassed. Furthermore, variants in which one or more of ABR-A, ABR-B, ABR-C, ABR-D, and / or ABR-E are omitted are also encompassed.

[0301] In FIG. 5C, the structures comprise: (1) the core structure (AR-A / B) according to the boxed structure of FIG. 2G; (2) an ABR-C having the structure of a scFv which binds to antigen C or epitope C (scFv-C), comprising (a) a VH-C, (b) an optional linker, and (c) a VL- C, from the N-terminus to the C-terminus or from the C-terminus to the N-terminus (e.g., top scFv structures of FIG. 1F); and (3) an ABR-D having the structure of a scFv which binds to antigen D or epitope D (scFv-D), comprising (a) a VH-D. (b) an optional linker, and (c) a VL-D, from the N-terminus to the C-terminus or from the C-terminus to the N-terminus (e.g., top Fab structures of FIG. 1F). The scFv-C and scFv-D are placed at the C-terminus of the heavy chain A and the heavy chain B, respectively of the core structure. Although not explicitly depicted, variants in which the core structure (AR-A / B) comprises any of the structures in FIG. 2G-2K are further encompassed. Furthermore, variants in which one or more of scFv-A, scFv-B, scFv-C, and / or scFv-D are replaced with the corresponding scFab structures (e.g., according to any of the scFab structures of FIG.1H) and / or one or more of ABR-A, ABR-B, ABR-C, and / or ABR-D are omitted are also encompassed.

[0302] In FIG. 5D, the structures comprise: (1) the core structure (AR-A / B) according to the boxed structure of FIG. 2G; (2) an ABR-C comprising a scFv-C (as described in FIG. 5B); and (3) an ABR-D comprising a scFv-D (as described in FIG. 5B). The scFv-C and scFv-D are placed at the C-terminus of the light chain A and the light chain B, respectively of the core structure. Although not explicitly depicted, variants in which the core structure (AR- A / B) comprises any of the structures in FIG. 2G-2K are further encompassed. Furthermore, variants in which one or more of scFv-A, scFv-B, scFv-C, and / or scFv-D are replaced with the corresponding scFab structures (e.g.. according to any of the scFab structures of FIG.1H) and / or one or more of ABR-A, ABR-B, ABR-C, and / or ABR-D are omitted are also encompassed.

[0303] In FIG. 5E, the structures comprise: (1) the core structure (AR-A / B) according to the boxed structure of FIG. 2G; (2) an ABR-C comprising a scFv-C (as described in FIG. 5B); and (3) an ABR-D comprising a scFv-D (as described in FIG. 5B). The scFv-C and scFv-D are placed at the N-terminus of the heavy chain A and the heavy chain B, respectively of the core structure. Although not explicitly depicted, variants in which the core structure (AR- A / B) comprises any of the structures in FIG. 2G-2K are further encompassed. Furthermore, variants in which one or more of scFv-A, scFv-B, scFv-C, and / or scFv-D are replaced with the corresponding scFab structures (e.g., according to any of the scFab structures of FIG.1H)and / or one or more of ABR-A, ABR-B, ABR-C, and / or ABR-D are omited are also encompassed.

[0304] In FIG. 5F, the structures comprise: (1) the core structure (AR-A / B) according to the boxed structure of FIG. 2G; (2) an ABR-C comprising a scFv-C (as described in FIG. 5B); and (3) an ABR-D comprising a scFv-D (as described in FIG. 5B). The scFv-C and scFv-D are placed at the N-terminus of the light chain A and the light chain B, respectively of the core structure. Although not explicitly depicted, variants in which the core structure (AR- A / B) comprises any of the structures in FIG. 2G-2K are further encompassed. Furthermore, variants in which one or more of scFv-A, scFv-B, scFv-C, and / or scFv-D are replaced with the corresponding scFab structures (e.g., according to any of the scFab structures of FIG.1H) and / or one or more of ABR-A, ABR-B, ABR-C, and / or ABR-D are omited are also encompassed.

[0305] In FIG. 5G, the structures comprise: (1) the core structure (AR-A / B) according to the boxed structure of FIG. 2G; (2) an ABR-C comprising a scFv-C (as described in FIG. 5B); (3) an ABR-D comprising a scFv-D (as described in FIG. 5B); (4) an ABR-E having the structure of a scFv which binds to antigen E or epitope E (scFv-E), comprising (a) a VH-E, (b) an optional linker, and (c) a VL-E, from the N-terminus to the C-terminus or from the C- terminus to the N-terminus (e.g.. top scFv structures of FIG. 1F); (5) an ABR-F having the structure of a scFv which binds to antigen F or epitope F (scFv-F), comprising (a) a VH-F. (b) an optional linker, and (c) a VL-F, from the N-terminus to the C-terminus or from the C- terminus to the N-terminus (e.g., top scFv structures of FIG. 1F); (6) an ABR-G having the structure of a scFv which binds to antigen G or epitope G (scFv-G), comprising (a) a VH-G, (b) an optional linker, and (c) a VL-G. from the N-terminus to the C-terminus or from the C- terminus to the N-terminus (e.g., top scFv structures of FIG. 1F); (7) an ABR-C having the structure of a scFv which binds to antigen H or epitope H (scFv-H), comprising (a) a VH-H, (b) an optional linker, and (c) a VL-H, from the N-terminus to the C-terminus or from the C- terminus to the N-terminus (e.g.. top scFv structures of FIG. 1F); (8) an ABR-I having the structure of a scFv which binds to antigen I or epitope I (scFv-I), comprising (a) a VH-L (b) an optional linker, and (c) a VL-I, from the N-terminus to the C-terminus or from the C- terminus to the N-terminus (e.g., top scFv structures of FIG. 1F); and (9) an ABR-J having the structure of a scFv which binds to antigen J or epitope J (scFv-J), comprising (a) a VH-J. (b) an optional linker, and (c) a VL-J, from the N-terminus to the C-terminus or from the C- terminus to the N-terminus (e.g., top scFv structures of FIG. 1F). The scFv-C and scFv-D areplaced at the N-terminus of the heavy chain A and the heavy chain B, respectively of the core structure. The scFv-E and scFv-F are placed at the N-terminus of the light chain A and the light chain B, respectively of the core structure. The scFv-G and scFv-H are placed at the C- terminus of the light chain A and the light chain B, respectively of the core structure. The scFv-I and scFv-J are placed at the C-terminus of the heavy chain A and the heavy chain B, respectively of the core structure. One or more of antigens A-J may be same or different from each other, and one or more of epitopes A-J may be same or different from each other. Although not explicitly depicted, variants in which the core structure (AR-A / B) comprises any of the structures in FIG. 2G-2K are further encompassed. Furthermore, variants in which one or more ofscFv-A, scFv-B, scFv-C. scFv-D, scFv-E, scFv-F, scFv-G, scFv-H, scFv-I, and / or scFv-J are replaced with the corresponding scFab structures (e.g., according to any of the scFab structures of FIG.1H) and / or one or more of ABR-A, ABR-B, ABR-C, ABR-D, ABR-E, ABR-F, ABR-G, ABR-H, ABR-I, and / or ABR-J are omitted are also encompassed.

[0306] In FIG. 5H, the structures comprise: (1) the core structure (AR-A / B) according to the boxed structure of FIG. 2G; (2) an ABR-C having the structure of a Fab which binds to antigen C or epitope C (Fab-C), comprising (a) a polypeptide (which may be called a heavychain C) comprising a VH-C and a CH-C (CH-C may comprise a CH1-C, a hinge-C. a CH2- C, and / or a CH3-C), from the N-terminus to the C-terminus and (b) a polypeptide (which may be called a light chain C) comprising a VL-C and a CL-C, wherein the heavy chain C and the light chain C are paired with each other, optionally via at least one disulfide bond and (e.g., bottom left (boxed) structure of FIG. 1E); and (3) an ABR-D having the structure of a Fab which binds to antigen D or epitope D (Fab-D). comprising (a) a polypeptide (which may be called a heavy- chain D) comprising a VH-D and a CH-D (CH-D may comprise a CH1-D, ahinge-D, a CH2-D, and / or a CH3-D), from the N-terminus to the C-terminus and (b) a polypeptide (which may be called a light chain D) comprising a VL-D and a CL-D, wherein the heavy chain D and the light chain D are paired with each other, optionally via at least one disulfide bond and (e.g., bottom left (boxed) structure of FIG. 1E). The heavy chain C and the light chain C may be placed at the N-terminus of the heavy chain A and the N-terminus of the light chain A, respectively, or placed at the N-terminus of the light chain A and the N- terminus of the heavy chain A, respectively. The heavy chain D and the light chain D may be placed at the N-terminus of the heavy chain B and the N-terminus of the light chain B, respectively, or placed at the N-terminus of the light chain B and the N-terminus of the heavy chain B, respectively . Although not explicitly depicted, variants in which the core structure(AR-A / B) comprises any of the structures in FIG. 2G-2K are encompassed. Furthermore, variants in which any of the paired VH-VL positions and / or any of the paired CH1 -CL positions are swapped and / or one or more of ABR-A, ABR-B, ABR-C, and / or ABR-D are omitted are also encompassed.

[0307] In FIG. 51, the structures comprise: (1) the core structure (AR-A / B) according to the boxed structure of FIG. 2G; (2) an ABR-C having the structure of a Fab-C, comprising (a) a polypeptide (which may be called a heavy chain C) comprising a VH-C and a CH-C (CH-C may comprise a CH1-C, a hinge-C, a CH2-C, and / or a CH3-C). from the N-terminus to the C-terminus and (b) a polypeptide (which may be called a light chain C) comprising a VL-C and a CL-C, wherein the heavy chain C and the light chain C are paired with each other, optionally via at least one disulfide bond and (e.g., bottom left (boxed) structure of FIG. 1E); and (3) an ABR-D having the structure of a Fab-D, comprising (a) a polypeptide (which may be called a heavy chain D) comprising a VH-D and a CH-D (CH-D may comprise a CH1-D. a hinge-D, a CH2-D, and / or a CH3-D), from the N-terminus to the C-terminus and (b) a polypeptide (which may be called a light chain D) comprising a VL-D and a CL-D, wherein the heavy chain D and the light chain D are paired with each other, optionally via at least one disulfide bond and (e.g., bottom left (boxed) structure of FIG. 1E). The heavy chain C and the light chain C may be placed at the C-terminus of the heavy chain A and the C-terminus of the light chain A, respectively, or placed at the C-terminus of the light chain A and the C- terminus of the heavy chain A, respectively. The heavy chain D and the light chain D may be placed at the C-terminus of the heavy chain B and the C-terminus of the light chain B, respectively, or placed at the C-terminus of the light chain B and the C-terminus of the heavy chain B, respectively. Although not explicitly depicted, variants in which the core structure (AR-A / B) comprises any of the structures in FIG. 2G-2K are encompassed. Furthermore, variants in which any of the paired VH-VL positions and / or any of the paired CH1-CL positions are swapped and / or one or more of ABR-A. ABR-B, ABR-C. and / or ABR-D are omitted are also encompassed.

[0308] In FIG. 5J, the structures comprise: (1) the core structure (AR-A / B) according to the top left (boxed) structure of FIG. 2J; (2) an ABR-C having the structure of a scFv which binds to antigen C or epitope C (scFv-C), comprising (a) a VH-C, (b) an optional linker, and (c) a VL-C, from the N-terminus to the C-terminus or from the C-terminus to the N-terminus (e.g.. top left or top right scFv structures of FIG. 1F); and (3) an ABR-D having the structure of a scFv which binds to antigen D or epitope D (scFv-D), comprising (a) a VH-D, (b) anoptional linker, and (c) a VL-D, from the N-terminus to the C-terminus or from the C- terminus to the N-terminus (e.g.. top left or top right scFv structure of FIG. 1F). The scFv-C and scFv-D are placed at the N-terminus of the scFv-A and the N-terminus of the scFv-B, respectively of the core structure. Although not explicitly depicted, variants in which the core structure (AR-A / B) comprises any of the structures in FIG. 2J-2K are further encompassed. Furthermore, variants in which one or more of ABR-A, ABR-B, ABR-C. and / or ABR-D are omitted and / or one or more are CLs are omitted are also encompassed.

[0309] In FIG. 5K, the structures comprise: (1) the core structure (AR-A / B) according to the top left (boxed) structure of FIG. 2 J; (2) an ABR-C having the structure of a scFv-C, as described above for FIG. 5 J; and (3) an ABR-D having the structure of a scFv-D, as described above for FIG. 5J. The scFv-C and scFv-D are placed at the N-terminus of the light chain A and the N-terminus of the light chain B, respectively of the core structure. Although not explicitly depicted, variants in which the core structure (AR-A / B) comprises any of the structures in FIG. 2J-2K are further encompassed. Furthermore, variants in which one or more of ABR-A, ABR-B, ABR-C, and / or ABR-D are omitted and / or one or more are CLs are omitted are also encompassed.

[0310] In FIG. 5L, the structures comprise: (1) the core structure (AR-A / B) according to the top left (boxed) structure of FIG. 2J; (2) an ABR-C having the structure of a scFv-C, as described above for FIG. 5J; and (3) an ABR-D having the structure of a scFv-D, as described above for FIG. 5J. The scFv-C and scFv-D are placed at the C-terminus of the light chain A and the C-terminus of the light chain B, respectively of the core structure. Although not explicitly depicted, variants in which the core structure (AR-A / B) comprises any of the structures in FIG. 2J-2K are further encompassed. Furthermore, variants in which one or more of ABR-A, ABR-B, ABR-C, and / or ABR-D are omitted and / or one or more are CLs are omitted are also encompassed.

[0311] In FIG. 5M, the structures comprise: (1) the core structure (AR-A / B) according to the top left (boxed) structure of FIG. 2J; (2) an ABR-C having the structure of a scFv-C, as described above for FIG. 5J; and (3) an ABR-D having the structure of a scFv-D, as described above for FIG. 5J. The scFv-C and scFv-D are placed at the C-terminus of the heavy chain A and the C-terminus of the heavy chain B, respectively of the core structure. Although not explicitly depicted, variants in which the core structure (AR-A / B) comprises any of the structures in FIG. 2J-2K are further encompassed. Furthermore, variants in whichone or more of ABR-A, ABR-B. ABR-C, and / or ABR-D are omited and / or one or more are CLs are omited are also encompassed.

[0312] In FIG. 5N, the structures comprise: (1) the core structure (AR-A / B / C / D) according to the top left structure of FIG. 5J; (2) an ABR-E having the structure of a scFv which binds to antigen E or epitope E (scFv-E), comprising (a) a VH-E, (b) an optional linker, and (c) a VL-E, from the N-terminus to the C-terminus or from the C-terminus to the N-terminus (e.g., top left or top right scFv structures of FIG. 1F); (3) an ABR-F having the structure of a scFv which binds to antigen F or epitope F (scFv-F), comprising (a) a VH-F. (b) an optional linker, and (c) a VL-F, from the N-terminus to the C-terminus or from the C-terminus to the N- terminus (e.g., top left or top right scFv structure of FIG. 1F); (4) an ABR-G having the structure of a scFv which binds to antigen G or epitope G (scFv-G), comprising (a) a VH-G, (b) an optional linker, and (c) a VL-G. from the N-terminus to the C-terminus or from the C- terminus to the N-terminus (e.g.. top left or top right scFv structure of FIG. 1F); (5) an ABR- H having the structure of a scFv which binds to antigen H or epitope H (scFv-H), comprising (a) a VH-H, (b) an optional linker, and (c) a VL-F, from the N-terminus to the C-terminus or from the C-terminus to the N-terminus (e.g., top left or top right scFv structure of FIG. 1F);6) an ABR-I having the structure of a scFv which binds to antigen I or epitope I (scFv-I), comprising (a) a VH-I, (b) an optional linker, and (c) a VL-I, from the N-terminus to the C- terminus or from the C-terminus to the N-terminus (e.g., top left or top right scFv structure of FIG. 1F); and (J) an ABR-J having the structure of a scFv which binds to antigen J or epitope J (scFv-J), comprising (a) a VH-J, (b) an optional linker, and (c) a VL-J, from the N-terminus to the C-terminus or from the C-terminus to the N-terminus (e.g.. top left or top right scFv structure of FIG. 1F). The scFv-E and scFv-F are placed at the N-terminus of the light A and the N-terminus of the light chain B, respectively of the core structure. The scFv-G and scFv- H are placed at the C-terminus of the light A and the C-terminus of the light chain B. respectively of the core structure. The scFv-I and scFv-J are placed at the C-terminus of the heavy A and the C-terminus of the heavy chain B, respectively of the core structure. Although not explicitly depicted, variants in which the core structure (AR-A / B / C / D) comprises any of the structures in FIG. 5 J are further encompassed. Furthermore, variants in which one or more of ABR-A. ABR-B, ABR-C, ABR-D, ABR-E, ABR-F, ABR-G, ABR-H, ABR-I, and / or ABR-J are omitted and / or one or more of the paired VH-VL positions are swapped are also encompassed.

[0313] FIG. 6 provides an additional antibody, antigen-binding antibody fragment, and multispecific antibody structure, which is a variation of the boxed antibody structure of FIG. 5A, but the variable domains are placed in different orientations. Although not explicitly depicted, variants in which and / or one or more of the paired VH-VL positions are swapped, one or more of the paired CH1 -CL positions are swapped, one or more of the constant domains are omitted are further encompassed.DETAILED DESCRIPTIONDefinitions

[0314] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0315] It must also be noted that, unless the context clearly dictates otherwise, the singular forms "a." “an.” and “the” as used herein and in the appended claims include plural refence. Thus, the reference to “a cell” refers to one or more cells and equivalents thereof known to those skilled in the art, and so forth. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by a person of skilled in the art.

[0316] It should be understood that, unless clearly indicated otherwise, in any methods disclosed or claimed herein that comprise more than one step, the order of the steps to be performed is not restricted by the order of the steps cited.

[0317] As used herein, the term “about” or “approximately” when used in reference to a particular recited numerical value, means that the value may vary from the recited value by no more than 10%. For example, as used herein, the expression “about 100” includes 90 and 110 and all values in between (e.g., 91, 92, 93, 99, 99.1. 99.2. 99.3, 99.4, 100, 100.8. 100.9, 101, 106, 107, 108, 109, etc.).

[0318] It is understood that aspects and embodiments of the disclosure described herein include “comprising,” “consisting,” and “consisting essentially of’ aspects and embodiments. Transitional phrases such as “comprising,” “including,” “having,” “containing,” “involving,” “composed of,” and the like are to be understood to be open-ended, namely , to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively.

[0319] By “comprising,” it is meant that the recited elements are required in, for example, the composition, method, kit, etc., but other elements may be included to form the. for example, composition, method, kit etc. within the scope of the claim. For example, an expression cassette “comprising” a gene encoding a therapeutic polypeptide operably linked to a promoter is an expression cassette that may include other elements in addition to the gene and promoter, e.g., poly-adenylation sequence, enhancer elements, other genes, linker domains, etc. The terms “including”, “includes”, “having”, “has”, “with”, or variants thereof used herein are intended to be inclusive in a manner similar to the term “comprising”.

[0320] By “consisting essentially of,” it is meant a limitation of the scope of the, for example, composition, method, kit, etc., described to the specified materials or steps that do not materially affect the basic and novel characteristic(s) of the, for example, composition, method, kit, etc. For example, an expression cassette “consisting essentially of’ a gene encoding a therapeutic polypeptide operably linked to a promoter and a polyadenylation sequence may include additional sequences, e.g., linker sequences, so long as they do not materially affect the transcription or translation of the gene. As another example, a variant, or mutant, polypeptide fragment “consisting essentially of’ a recited sequence has the amino acid sequence of the recited sequence plus or minus about 10 amino acid residues at the boundaries of the sequence based upon the full length naive polypeptide from which it was derived, e.g., 10, 9, 8, 7, 6, 5, 4, 3, 2 or 1 residue less than the recited bounding amino acid residue, or 1. 2, 3, 4. 5, 6, 7, 8. 9, or 10 residues more than the recited bounding amino acid residue.

[0321] By “consisting of,” it is meant the exclusion from the composition, method, or kit of any element, step, or ingredient not specified in the claim. For example, a polypeptide or polypeptide domain “consisting of’ a recited sequence contains only the recited sequence.

[0322] “Cluster of Differentiation 28” or “CD28”, also known as “Tp44”, is a protein having an important role in T-cell development, activation, proliferation, and survival, and generally refers to any native CD28 from any vertebrate source, including mammals such as primates (e.g., humans or non-human primates such as cynomolgus) and rodents (e.g., mice and rats), unless otherwise indicated. The term encompasses “full-length,” unprocessed CD28 and any form of CD28 that results from processing in the cell, and naturally occurring variants of CD28, including, for example, splice variants or allelic variants. In humans, CD28 is encoded by the CD28 gene on chromosome 2, with gene location 2q33.2 (NCBI). Human CD28 may have an aminoacid sequence provided as GenBank: GenBank: AAH93698.1, which is 220 amino acids in length. In one aspect, human CD28 has the amino acid sequence provided as SEQ ID NO: 100 or may contain one or more equivalent / corresponding residue(s) from anon-human species, e.g., mouse, rodent, monkey, ape and the like.

[0323] The term “antibody” is used herein in the broadest sense and encompasses various antibody structures, including but not limited to monoclonal antibodies, polyclonal antibodies, multispecific antibodies (e.g., bispecific, trispecific, and tetraspecific antibodies), and / or antibody fragments (preferably those fragments that exhibit the desired antigen- binding activity, which are referred to as "antigen-binding antibody fragments”). A “full antibody”, “full Ab”, “full size antibody”, “full size Ab”, “full-length antibody”, “intact antibodies”, or “whole antibody”, or the like, encompasses molecules having a structure substantially similar to a native antibody and, in case of IgG, IgD, or IgE, comprises two immunoglobulin heavy chains and two immunoglobulin light chains. An “antigen-binding fragment” or “antigen-binding antibody fragment” refers to a portion of an intact antibody or to a combination of portions derived from an intact antibody or from intact antibodies and binds the antigen(s) to which the intact antibody or antibodies bind.

[0324] The terms “intact antibody,” “full length antibody,” and “whole antibody” or the like are used herein interchangeably and refer to an antibody having a structure substantially similar to a native antibody. In some instances, an antibody comprises heavy (H) and light (L) chains interconnected by disulfide bonds. There are five major classes of antibodies: IgA, IgD, IgE, IgG, and IgM, and several of these may be further divided into subclasses (isotypes), e.g., IgG1, IgG2, IgG3. IgG4, IgA1, and IgA2. The heavy chain constant domains that correspond to the different classes of immunoglobulins are called a, 5, e. y, and p, respectively. For example, an intact IgG (or IgD or IgE) antibody comprises two immunoglobulin heavy chains and two immunoglobulin light chains. Therefore, in some instances, an antibody according to the present disclosure may comprise two pairs of heavy and light chains interconnected by disulfide bonds, or an antigen-binding fragment(s) thereof. Some intact antibody comprises multiple units, each comprising two pairs of heavy and light chains interconnected by disulfide bonds. For example, an intact IgA comprises tw o units and an intact IgM comprises five units. Therefore, in other instances, an antibody according to the present disclosure may instead comprise multiple (e.g., two, three, four, five, and so on) units each comprising two pairs of heavy and light chains interconnected by disulfide bonds, or an antigen-binding fragment(s) thereof.

[0325] In an intact antibody, each heavy chain comprises a variable domain, such as a heavy chain variable domain (“VH”) (also referred to as heavy chain variable region), and a heavy chain constant region (“CH”). In case of an intact antibody, a CH comprises a heavy chain constant domain 1 (CH1), a hinge, a heavy chain constant domain 2 (CH2), and a heavy chain constant domain 3 (CH3), with some exceptions, e.g., a camel IgG2 or camel IgG3, in which a CH comprises a hinge, a CH2, and a CH3, or a shark antibody (e.g., IgNAR), in which a CH comprises a hinge, a CH1, a CH2, a CH3, a CH4, and a CH5. In an intact antibody, each light chain is comprised of: a light chain variable domain (VL); and a light chain constant domain (CL). Typically (with some exceptions such as nanobodies, camelid heavy chain antibodies, IgNARs, and the like), one VH and one VL may form an antigen- binding structure. Therefore, ‘"a set of variable domains" or “a variable domain pair” (or the like) of an antibody means the set or combination of the VH and VL of the antibody.

[0326] The VH and VL can be further subdivided into regions of hypervariability, termed complementarity determining regions (CDRs), interspersed with regions that are more conserved, termed framework regions (FRs). Each VH and VL polypeptide is composed of three CDRs and four FRs, arranged from amino-terminus to carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3. FR4. The CDRs in a heavy chain are designated “CDRHL” “CDRH2,” and “CDRH3,” respectively, and the CDRs in a light chain are designated “CDRL1,” “CDRL2,” and CDRL3 " Therefore, “a set of heavy chain CDRs” (or the like) of an antibody means the set or combination of the CDRH1, CDRH2, and CDRH3 of the antibody, “a set of light chain CDRs” (or the like) of an antibody means the set or combination of the CDRLL CDRL2, and CDRL3 of the antibody, and “a set of heavy and light chain CDRs” (or the like) of an antibody means the set or combination of the CDRH1, CDRH2, CDRH3, CDRL1, CDRL2, and CDRL3 of the antibody. The FRs in a heavy chain are designated “FRH1,” “FRH2,” “FR3,” and “FRH4,” respectively, and the FRs in a light chain are designated “FRL1.” “FRL2,” “FRL3,” and “FRL4.” In certain embodiments of the disclosure, the FRs of the antibody (or antigen-binding fragment thereof) may be identical to the human germline-encoded sequences (e.g., heavy chain FR sequences encoded by the VH1-03, VH1-69, VH2-05, VH3-09, VH3-23, VH4-31, VH4-39, VH4-4A, VH4-59, VH1-02, VH4-0B, VH4-59, VH1-18, or VH3-48 germline; and / or light chain FR sequences encoded by the VK4-01, VK1-12, VK3-1L VK1-39, VK1-33, VK-2-28, VK3-15, VK1-05, VK3-20, VL2-11, VL1-51, VL1-40, VL2-11, VL6-57, VL2-14, or VL1-44germline) or may be naturally or artificially modified. An amino acid consensus sequence may be defined based on a side-by-side analysis of two or more CDRs.

[0327] The phrase “heavy chain” or “HC” is used in its broadest sense and encompasses a polypeptide comprising at least one immunoglobulin heavy chain domain or part (i.e., at least one of VH, CH1, hinge, CH2, and / or CH3). Similarly, the phrase “light chain” or “LC” is used in its broadest sense and encompasses a polypeptide comprising at least one immunoglobulin light chain domain (i.e., at least one of VL and / or CL).

[0328] In general, CDRs may be determined using any appropriate manner. For example, CDR sequences may be: determined based on an appropriate numbering system (e.g., Kabat numbering or IMGT numbering, or alternatively Chothia numbering. Martin numbering (also known as AbM numbering), Gelfand numbering, Honneger’s numbering (also known as AHo’s numbering), or Chemical Computing Group (CCG) numbering for variable regions; determined structurally (see e.g., IgBlast (https: / / www-.ncbi.nlm.nih.gov / igblast / );Dondelinger et al., Front Immunol. 2018 Oct 16;9:2278; http: / / www-.bioinf.org.uk / abs / info.html#cdrid; http: / / opig. stats, ox, ac.uk / webapps / newsabdab / sabpred / anarci / ). e.g., by using x-ray crystallography to visualize specific epitope contact residues; or a combination thereof.

[0329] The numbering of amino acid residues in antibody variable and constant domains may be performed by the EU-index or EU numbering system, as described in Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991). The EU numbering system is used in the present specification unless otherwise specified.

[0330] According to IMGT (the international ImMunoGeneTics information system for immunoglobulins or antibodies, T cell receptors, MH, immunoglobulin superfamily IgSF and MhSF), the CH1 domain is the amino acid positions (or simply referred to as “positions” herein) 118-215 (EU numbering) and the hinge region is the amino acid positions 216-230 (EU numbering). The term “CH1 domain” is used in a broad sense herein to encompass any naturally occurring, corresponding heavy chain constant domain and / or region allotypes and variants thereof, which may comprise fewer or more amino acids and / or amino acid modification(s) and to refer to a heavy chain region comprising at least 80% of the heavy chain positions 118-215 (EU numbering)) and in some instances also comprising a portion of the hinge region (a portion of heavy chain positions 216-230 (EU numbering)) is included(e.g., up to position 218 or 220). A human IgG1 CH1 domain reference sequence, corresponding to the amino acid positions 118-220 according to EU numbering, is provided herein as SEQ ID NO: 1, which corresponds to the CH1 domain sequence of human IgG1 Allotype “IGHGl*01 (J00228)”, “IGHG1*O4 (JN582178)”, or “IGHGl*07” and is an exemplary7amino acid sequence of a wild-ty pe (WT) CH1 domain.

[0331] Human IgG1 CH1 domain reference sequence:ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVL QSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSC (positions 118-220 according to EU numbering) (SEQ ID NO: 1).

[0332] Alternative CH1 domain reference sequences of human IgG1 include but are not limited to SEQ ID NO: 2, which corresponds to the CH1 domain sequence of human IgG1 Allotype “IGHGl*03 (Y14737)” or “IGHG1*O8”

[0333] Human IgG1 alternative CH1 domain reference sequence (214R relative to SEQ ID NO: 1):ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVL QSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKRVEPKSC (positions 118-220 according to EU numbering) (SEQ ID NO: 2).

[0334] These CH1 domain reference sequences are exemplary as “CH1 domain” sequences as used herein include any naturally occurring CH1 domain allotype or allelic variant.

[0335] According to IMGT, the hinge is the amino acid positions 216-230 (EU numbering). The term “hinge” is used in a broad sense herein to refer to a heavy chain region comprising at least at least 60% of the hinge positions 216-230 (EU numbering). Human IgG1. IgG2, IgG3, and IgG4 hinge reference sequences, corresponding to the amino acid positions 231- 340 according to EU numbering, are provided herein as SEQ ID NOS: 11, 12, 13, and 14, respectively, which are exemplary amino acid sequence of a wild-type (WT) hinge.

[0336] Human IgG1 hinge reference sequence:EPKSCDKTHTCPPCP (positions 216-230 according to EU numbering) (SEQ ID NO: 11).

[0337] Human IgG2 hinge reference sequence: ERKCCVECPPCP (SEQ ID NO: 12).

[0338] Human IgG3 hinge reference sequence:ELKTPEGDTTHTCPRCPEPKSCDTPPPCPRCPEPKSCDTPPPCPRCPEPKSCDTPPPCPRCP (SEQ ID NO: 13)

[0339] Human IgG4 hinge reference sequence:ESKYGPPCPSCP (SEQ ID NO: 14).

[0340] According to IMGT, the CH2 domain is the amino acid positions (or simply referred to as '‘positions” herein) 231 -340 (EU numbering). The term “CH2 domain” is used in a broad sense herein to refer to a heavy chain region comprising at least at least 80% of the heavy chain positions 231-340 (EU numbering)). A human IgG1 CH2 domain reference sequence, corresponding to the amino acid positions 231-340 according to EU numbering, is provided herein as SEQ ID NO: 21, which is an exemplary amino acid sequence of a wildtype (WT) CH2 domain.

[0341] Human IgG1 CH2 domain reference sequence: APELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNA KTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAK (SEQ ID NO: 21)

[0342] The recited CH2 domain reference sequence is exemplary as the “CH2 domain” sequences as used herein include any naturally occurring CH2 domain allotype or allelic variant.

[0343] According to IMGT, the CH3 domain is the amino acid positions (or simply referred to as “positions” herein) 341-446 (EU numbering). The term “CH3 domain” is used in a broad sense herein to refer to a heavy' chain region comprising at least seven consecutive amino acid positions of the heavy chain positions 341-446 (EU numbering)). A CH3 domain reference sequence, corresponding to the amino acid positions 341-446 according to EU numbering, is provided herein as SEQ ID NO: 31, which corresponds to the CH3 domain sequence of human IgG1 Allotype “IGHGl*01 (J00228)” or “IGHGl*08” and is an exemplary amino acid sequence of a wild-type (WT) CH3 domain.

[0344] Human IgG1 CH3 domain reference sequence:

[0345] GQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYK TTPPVLDSDGSFFLYSKETVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPG (SEQ ID NO: 31)

[0346] Alternative CH3 domain reference sequences of human IgG1 may include but are not limited to SEQ ID NO: 32, which corresponds to the CH3 domain sequence of human IgG1 Allotype ‘IGHGl*03 (Y 14737)”, SEQ ID NO: 33, which corresponds to the CH3 domain sequence of human IgG1 Allotype “IGHGI*04 (JN582178)”, and SEQ ID NO: 34, which corresponds to the CH3 domain sequence of human IgG1 Allotype “IGHG1*07”

[0347] Human IgG1 alternative CH3 domain reference sequence 1 (356E and 358M relative to SEQ ID NO: 31)

[0348] GQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYK TTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPG (SEQ ID NO: 32)

[0349] Human IgG1 alternative CH3 domain reference sequence 2 (4221 relative to SEQ ID NO: 31):

[0350] GQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYK TTPPVLDSDGSFFLYSKLTVDKSRWQQGNIFSCSVMHEALHNHYTQKSLSLSPG (SEQ ID NO: 33)

[0351] Human IgG1 alternative CH3 domain reference sequence 3 (431G relative to SEQ ID NO: 31):

[0352] GQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYK TTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEGLHNHYTQKSLSLSPG (SEQ ID NO: 34)

[0353] Furthermore, CH3 domain reference sequences of human IgG2, IgG3, and IgG4 include but are not limited to SEQ ID NOS: 35, 36, and 37, respectively.

[0354] CH3 domain reference sequence of human IgG2:

[0355] GQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDISVEWESNGQPENNYK TTPPMLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPG(SEQ ID NO: 35)

[0356] CH3 domain reference sequence of human IgG3:

[0357] GQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESSGQPENNYN TTPPMLDSDGSFFLYSKLTVDKSRWQQGNIFSCSVMHEALHNRFTQKSLSLSPG (SEQ ID NO: 36)

[0358] CH3 domain reference sequence of human IgG4:

[0359] GQPREPQVYTLPPSQEEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYK TTPPVLDSDGSFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSLSLG (SEQ ID NO: 37)

[0360] These CH3 domain reference sequences are exemplary as the “CH3 domain” sequences used herein include any naturally occurring CH3 domain allotype or allelic variant. Accordingly, an amino acid modification(s) in variant CH3 domain polypeptides according to the present disclosure may be relative to and / or incorporated to any parent CH3 domain polypeptides, for example but not limited to a wild-type sequence, such as SEQ ID NO: 1 or any allelic variants thereof, such as any of SEQ ID NOS: 31-37. In some embodiments, a CH3 domain may further comprise lysine at the C terminus (i.e., K447, according to EU numbering).

[0361] There are two major CL isotypes, kappa (“K”) and lambda (“X”), and such CL domains are referred to herein as kappa CL domain (“CLK” domain) and lambda CL domain (“CLk” domain).

[0362] According to IMGT, the CLK domain is the amino acid positions 108-214 (EU numbering). The term “CLK domain” is used in a broad sense herein to refer to a light chain region comprising at least seven consecutive amino acid positions of the kappa light chain positions 108-214 (EU numbering). A human Ig CLK domain reference sequence, corresponding to the amino acid positions 108-214 (EU numbering), is provided herein as SEQ ID NO: 41, which is an exemplary amino acid sequence of a wild-type (WT) CLK domain.

[0363] Human Ig CLK domain reference sequence:

[0364] RTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNS QESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (positions 108 to 214 according to EU numbering) (SEQ ID NO: 41).

[0365] According to IMGT, the CLλ domain is the amino acid positions 107-215 (EU numbering). The term “CLλ domain” is used in a broad sense herein to refer to a light chain region comprising at least seven consecutive amino acid positions of the lambda light chain positions 107-215 (EU numbering). A CLλ domain reference sequence, corresponding to the amino acid positions 107-215 (EU numbering), is provided herein as SEQ ID NO: 42. which is an exemplary amino acid sequence of a wild-type (WT) CLλ domain.

[0366] Human Ig CLZ domain reference sequence:

[0367] GQPKAAPSVTLFPPSSEELQANKATLVCLISDFYPGAVTVAWKADSSPVKAG VETTTPSKQSNNKYAASSYLSLTPEQWKSHRSYSCQVTHEGSTVEKTVAPTECS (positions 107 to 215 according to EU numbering) (SEQ ID NO: 42).

[0368] Various standard sequences (corresponding to different allotypes) of the constant domains of human IgG1, IgG2, IgG3, and IgG4 are known in the field and may be found for example in Vidarsson et al., Front Immunol. 2014 Oct 20:5:520 and US Patent No. 9150663, the disclosures of which are hereby incorporated by reference herein in their entirety herein. Again these reference sequences are exemplary as human IgG1, IgG2, IgG3, and IgG4 sequences include any naturally occurring human IgG1. IgG2, IgG3, and IgG4 allotype.

[0369] A “Fc region” is a C-terminal region of an immunoglobulin heavy chain that contains at least a portion of the constant region, including native sequence Fc regions and variant Fc regions. A human IgG heavy chain Fc region can extend from Asp221, to the carboxyl-terminus of the heavy chain. However, the C-terminal lysine (Lys447) of the Fc region may or may not be present. Unless otherwise specified herein, numbering of amino acid residues in the Fc region or constant region is according to the EU numbering system, as described in Kabat et al., Sequences of Proteins of Immunological Interest^ 5th Ed. Public Health Sendee, National Institutes of Health, Bethesda, Md., 1991.

[0370] The phrase “effector function” of an antibody refers to biological activities attributable to the Fc region of an antibody, which varies by antibody class or isotype. Exemplary effector functions include: complement (e.g., Clq) binding and complement dependent cytotoxicity (CDC); Fc receptor binding; antibody-dependent cell-mediated cytotoxicity (ADCC); phagocytosis; down regulation of cell surface receptors (e.g., B cell receptor); and B cell activation.

[0371] An “antigen-binding fragment of an antibody” or “antigen-binding antibody fragment” includes any naturally occurring, enzymatically obtainable, synthetic (e.g., domain orders are rearranged relative to naturally occurring antibody), or genetically engineered polypeptide or protein or glycoprotein that comprises an antigen-binding antibody domain (e.g., a VH domain, or VH and VL domains) specifically binds an antigen to form a complex. Exemplary antigen-binding antibody fragments include, but are not limited to: Fv; fragment antigen-binding (“Fab”) fragment; single-chain Fab (scFab); Fab' fragment; Fab' containing a free sulfhydryl group ('Fab'-SH’); F(ab')2 fragment; F(ab')3 fragment; diabody; triabody;tetrabody; linear antibodies; single-chain antibody molecules (e.g. single-chain variable fragment C’scFvJ. tandem scFv; scFv-Fc; scFv-CH (e.g.. scFv-CH3. scFv-CH2, scFv-CH1, scFv-CH2 / CH3, scFv-CH1 / CH2, scFv-CH1 / CH3, scFv-CH 1 / CH2 / CH3, scFv- CH1 / hinge / CH2 / CH3, minibody, or the like); scFv-zipper; tandem scFv-Fc; tandem scFv-CH (e.g., tandem scFv-CH3, tandem scFv-CH2, tandem scFv-CH1, tandem scFv-CH2 / CH3, tandem scFv-CH1 / CH2, tandem scFv-CH1 / CH3, tandem scFv-CH1 / CH2 / CH3, tandem scFv- CH1 / hinge / CH2 / CH3. or the like); tandem scFv-zipper; diabody-Fc; diabody-CH (e.g., diabody-CH3, diabody-CH2, diabody-CH1, diabody-CH2 / CH3, diabody-CH1 / CH2, diabody- CH1 / CH3, diabody-CH1 / CH2 / CH3, diabody-CH1 / hinge / CH2 / CH3, or the like); diabody- zipper; single domain antibody (sdAb); nanobody or VHH (i.e.. VH domain only and no VL); tandem sdAb or tandem nanobody; sdAb-Fc or nanobody-Fc; sdAb-CH or nanobody-CH (e.g., sdAb-CH3, sdAb-CH2, sdAb-CH1, sdAb-CH2 / CH3, sdAb-CH1 / CH2, sdAb-CH1 / CH3, sdAb-CH1 / CH2 / CH3, sdAb-CH1 / hinge / CH2 / CH3, or the like); a heavy chain-only antibody (HCAb); camel Ig; immunoglobulin new antigen receptor (IgNAR); “half-antibody” variant of any of the foregoing (when the structure allows); and monospecific or multispecific antibodies formed from one or more of antibody fragments such as the foregoing. Further exemplary antigen-binding antibody fragments include, but are not limited to: minimal recognition units consisting of the amino acid residues that mimic the hypervariable region of an antibody (e.g., an isolated complementarity determining region (CDR) such as a CDR3 peptide), or a constrained FR3-CDR3-FR4 peptide; and small modular immunopharmaceuticals (SMIPs). Tn some embodiments, antibodies (e.g., multispecific antibodies) described herein comprise one or more Fabs, scFvs, scFabs, sdAbs, and / or IgGs.

[0372] For a review of certain antibody fragments, see, e.g., Hudson et al. Nat. Med. 9: 129- 134 (2003). For discussion of Fab and F(ab')2 fragments comprising salvage receptor binding epitope residues and having increased in vivo half-life, see U.S. Pat. No. 5,869.046.Diabodies are antibody fragments with two antigen-binding sites that may be bivalent or bispecific. See, for example, EP 404,097; WO 1993 / 01161; Hudson et al. Nat. Med. 9: 129- 134 (2003); and Hollinger et al. Proc. Natl. Acad. Sci. USA 90: 6444-6448 (1993). Triabodies and tetrabodies are also described in Hudson et al. Nat. Med. 9: 129-134 (2003). Single- domain antibodies are antibody fragments comprising all or a portion of the heavy chain variable domain or all or a portion of the light chain variable domain of an antibody. In certain embodiments, a single-domain antibody is a human single-domain antibody (Domantis, Inc., Waltham, Mass.; see, e.g., U.S. Pat. No. 6,248,516 Bl). Antibody fragmentscan be made by various techniques, including but not limited to proteolytic digestion of an intact antibody as well as production by recombinant host cells (e.g. E. coli or phage), as described herein.

[0373] An antigen-binding fragment of an antibody will typically comprise at least one variable domain. The variable domain may be of any size or amino acid composition and will generally comprise at least one CDR, which is adjacent to or in frame with one or more framework sequences. In antigen-binding fragments having a VH associated with a VL, the VH and VL may be situated relative to one another in any suitable arrangement. For example, the variable region may be dimeric and contain VH - VH, VH - VL or VL - VL dimers. Alternatively, the antigen-binding fragment of an antibody may contain a monomeric VH or VL domain.

[0374] In certain embodiments, an antigen-binding fragment of an antibody may contain at least one variable domain covalently linked to at least one constant domain. Non-limiting, exemplary configurations of variable and constant domains that may be found within an antigen- binding fragment of an antibody of the present disclosure include: (i) VH -CH1 ; (ii) VH -CH2; (iii) VH -CH3; (iv) VH -CH1 -CH2; (V) VH -CH1-CH2-CH3; (vi) VH -CH2- CH3; (vii) VH -CL; (viii) VL -CH1 ; (ix) VL - CH2; (x) VL -CH3; (xi) VL -CH1-CH2; (xii) VL -CH1-CH2-CH3; (xiii) VL -CH2-CH3; and (xiv) VL -CL. In any configuration of variable and constant domains, including any of the exemplary configurations listed above, the variable and constant domains may be either directly linked to one another or may be linked by a full or partial hinge or linker region. A hinge region may consist of at least two (e.g.. 5. 10. 15. 20. 40. 60 or more) amino acids, which result in a flexible or semi-flexible linkage between adjacent variable and / or constant domains in a single polypeptide molecule. Moreover, an antigen-binding fragment of an antibody of the present disclosure may co...

Claims

CLAIMSWhat is claimed is:

1. An anti -human cluster of differentiation 28 (CD28) antibody or antigen-binding antibody fragment, which comprises: a first heavy chain variable domain (VH-1) comprising a first heavy chain complementarity determining region (CDR) 1 (CDRH1-1), a first heavy chain CDR2 (CDRH2-1), and a first heavy chain CDR3 (CDRH3-1); and / or a first light chain variable domain (VL-1) comprising a first light chain CDR1 (CDRL1- 1), a first light chain CDR2 (CDRL2-1). and a first light chain CDR3 (CDRL3-1), wherein the antibody or antigen binding antibody fragment comprises a CDR amino acid sequence according to any one of those listed in Table 1B and / or 12B or a variant thereof having at least about 50%, 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity.

2. The anti-human CD28 antibody or antigen-binding antibody fragment of claim 1, wherein:(a) the amino acid sequence of the CDRH1-1 comprises or consists of: a heavy chain complementarity determining region 1 (CDRH1) amino acid sequence contained in any one of the heavy chain variable domain (VH) amino acid sequences listed in Table 1A and / or 12A; and / or any one of the CDRH1 amino acid sequences listed in Table 1B and / or 12B;(b) the amino acid sequence of the CDRH2-1 comprises or consists of: a heavy chain complementarity determining region 2 (CDRH2) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 1A and / or 12A; and / or any one of the CDRH2 amino acid sequences listed in Table 1B and / or 12B; and / or(c) the amino acid sequence of the CDRH3-1 comprises or consists of: a heavy chain complementarity determining region 3 (CDRH3) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 1A and / or 12A; and / or any one of the CDRH3 amino acid sequences listed in Table 1B and / or 12B, and / or wherein:(d) the amino acid sequence of the CDRL1-1 comprises or consists of: a light chain complementarity determining region 1 (CDRL1) amino acid sequence contained in any one of the light chain variable domain (VL) amino acid sequences listed in Table 1A and / or 12A; and / or any one of the CDRL1 amino acid sequences listed in Table IB and / or 12B;(e) the amino acid sequence of the CDRL2-1 comprises or consists of: a light chain complementarity determining region 2 (CDRL2) contained in any one of the VL amino acid sequences listed in Table 1A and / or 12A; and / or any one of the CDRL2 amino acid sequences listed in Table 1B and / or 12B; and / or(f) the amino acid sequence of the CDRL3-1 comprises or consists of: a light chain complementarity determining region 3 (CDRL3) contained in any one of the VL amino acid sequences listed in Table 1A and / or 12A; and / or any one of the CDRL3 amino acid sequences listed in Table 1B and / or 12B.

3. The anti -human CD28 antibody or antigen-binding antibody fragment of claim 1 or 2, comprising:(a) a set of heavy chain CDR amino acid sequences of a first anti-CD28 antibody selected from the antibodies having the amino acid sequences listed in Tables 1A-1D and / or 12A-12D;(b) a set of light chain CDR amino acid sequences of a first anti-CD28 antibody selected from the antibodies having the amino acid sequences listed in Tables 1A-1D and / or 12A-12D;(c) a set of heavy and light chain CDR amino acid sequences of a first anti-CD28 antibody selected from the antibodies having the amino acid sequences listed in Tables 1A-1D and / or 12A-12D; and / or(d) a set of heavy chain CDR amino acid sequences of a first anti-CD28 antibody selected from the antibodies listed having the amino acid sequences in Tables 1A-1D and / or 12A-12D; and a set of light chain CDR ammo acid sequences of a second anti-CD28 antibody selected from the antibodies having the amino acid sequences listed in Tables 1A-1D and / or 12A-12D4. The anti-human CD28 antibody or antigen-binding antibody fragment of any one of claims 1-3. comprising:(A) said VH-1 and said VL-1, wherein:(1) the amino acid sequences of the CDRH1-1, the CDRH2-1, and the CDRH3-1 comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, and a CDRH3, respectively, contained in the VH of a first anti-CD28 antibody; and(2) the amino acid sequences of the CDRL1-1, the CDRL2-1, and the CDRL3- 1 comprise or consist of the amino acid sequences of a CDRL1, a CDRL2, and a CDRL3, respectively, contained in the VL of said first anti-CD28 antibody. wherein said first anti-CD28 antibody is:(I) any one of the following anti-CD28 antibodies listed in Tables 1A-1D: (1) Ab No.

1. (2) Ab No. 21, (3) Ab No. 28, (4) Ab No. 46, (5) Ab No. 57, (6) Ab No. 61, or (7) Ab No. 68; and / or(II) any one of the following anti-CD28 antibodies listed in Tables 1A-1D and / or 12A-12D: (i) Ab No. 1; (ii) Ab No. 2; (iii) Ab No. 3; (iv) Ab No. 4; (v) Ab No. 5; (vi) Ab No. 6; (vii) Ab No. 7; (viii) Ab No. 8; (ix) Ab No. 9; (x) Ab No. 10; (xi) Ab No. 11; (xii) Ab No. 12; (xiii) Ab No. 13; (xiv) Ab No. 14; (xv) Ab No. 15; (xvi) Ab No. 16; (xvii) Ab No. 17; (xviii) Ab No. 18; (xix) Ab No. 19; (xx) Ab No. 20; (xxi) Ab No. 21; (xxi-a) Ab No. 21a; (xxi-b) Ab No. 21b; (xxi-c) Ab No. 21c; (xxi-d) Ab No. 21d; (xxi-e) Ab No. 21e; (xxi-f) Ab No. 21 f: (xxii) Ab No. 22; (xxiii) Ab No. 23;(xxiv) Ab No. 24; (xv) Ab No. 25; (xvi) Ab No. 26; (xvii) Ab No. 27; (xviii) Ab No. 28; (xviii-a) Ab No. 28a; (xviii-b) Ab No. 28b; (xviii-c) Ab No. 28c; (xviii-d) Ab No. 28d; (xviii-e) Ab No. 28e; (xviii-f) Ab No. 28f; (xix) Ab No. 29; (xxx) Ab No. 30; (xxxi) Ab No. 31; (xxxii) Ab No. 32; (xxxiii) Ab No. 33; (xxxiv) Ab No. 34; (xxxv) Ab No. 35; (xxxvi) Ab No. 36; (xxxvii) Ab No. 37; (xxxviii) Ab No. 38; (xxxix) Ab No. 39; (xl) Ab No. 40; (xli) Ab No. 41; (xlii) Ab No. 42; (xliii) Ab No. 43; (xliv) Ab No. 44; (xlv) Ab No. 45; (xlvi) Ab No. 46; (xlvi-a) Ab No. 46a; (xlvi-b) Ab No. 46b;(xlvi-c) Ab No. 46c; (xlvi-d) Ab No. 46d; (xlvi-e) Ab No. 46e; (xlvii) Ab No. 47; (xlviii) Ab No. 48; (xlix) Ab No. 49; (1) Ab No. 50; (li) Ab No. 51; (lii) Ab No. 52; (liii) Ab No. 53; (liv) Ab No. 54; (Iv) Ab No. 55; (Ivi) Ab No. 56; (Ivii) Ab No. 57;(Ivii-a) Ab No. 57a; (Ivii-b) Ab No. 57b; (Ivii-c) Ab No. 57c; (Ivii-d) Ab No. 57d; (Ivii-e) Ab No. 57e; (Ivii-f) Ab No. 57f; (Iviii) Ab No. 58; (lix) Ab No. 59; (lx) Ab No. 60; (Ixi) Ab No. 61; (Ixi-a) Ab No. 61a; (Ixi-b) Ab No. 61b; (Ixi-c) Ab No. 61c; (Ixi-d) Ab No. 61d; (Ixi-e) Ab No. 61e; (Ixii) Ab No. 62; (Ixiii) Ab No. 63; (Ixiv) Ab No. 64; (Ixv) Ab No. 65; (Ixvi) Ab No. 66; (Ixvii) Ab No. 67; (Ixviii) Ab No. 68; (Ixviii-a) Ab No. 68a; (Ixviii-b) Ab No. 68b; (Ixviii-c) Ab No. 68c; (Ixviii-d) Ab No. 68d; (Ixviii-e) Ab No. 68e; (Ixviii-f) Ab No. 68f; or (Ixix) Ab No. 69; or(B) the VH-1 and optionally the VL- 1, wherein the amino acid sequences of the CDRH1- 1, the CDRH2-1, and the CDRH3-1 comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, and a CDRH3, respectively, contained in the VH of:(I) any one of the following anti-CD28 antibodies listed in Tables 1A-1D: (1) Ab No. 70 or (2) Ab No. 83; and / or(II) any one of the following anti-CD28 antibodies listed in Tables 1A-1D and / or 12A-12D: (i) Ab No. 1; (ii) Ab No. 2; (iii) Ab No. 3; (iv) Ab No. 4; (v) Ab No. 5; (vi) Ab No. 6; (vii) Ab No. 7; (viii) Ab No. 8; (ix) Ab No. 9; (x) Ab No. 10; (xi) Ab No. 11; (xii) Ab No. 12; (xiii) Ab No. 13; (xiv) Ab No. 14; (xv) Ab No. 15; (xvi) Ab No. 16; (xvii) Ab No. 17; (xviii) Ab No. 18; (xix) Ab No. 19; (xx) Ab No. 20; (xxi) Ab No. 21; (xxi-a) Ab No. 21a; (xxi-b) Ab No. 21b; (xxi-c) Ab No. 21c; (xxi-d) Ab No. 21d; (xxi-e) Ab No. 21e; (xxi-f) Ab No. 21f; (xxii) Ab No. 22; (xxiii) Ab No. 23;(xxiv) Ab No. 24; (xv) Ab No. 25; (xvi) Ab No. 26; (xvii) Ab No. 27; (xviii) Ab No. 28; (xviii-a) Ab No. 28a; (xviii-b) Ab No. 28b; (xviii-c) Ab No. 28c; (xviii-d) Ab No. 28d; (xviii-e) Ab No. 28e; (xviii-f) Ab No. 28f; (xix) Ab No. 29; (xxx) Ab No. 30;(xxxi) Ab No. 31; (xxxii) Ab No. 32; (xxxiii) Ab No. 33; (xxxiv) Ab No. 34; (xxxv) Ab No. 35; (xxxvi) Ab No. 36; (xxxvii) Ab No. 37; (xxxviii) Ab No. 38; (xxxix) Ab No. 39; (xl) Ab No. 40; (xli) Ab No. 41; (xlii) Ab No. 42; (xliii) Ab No. 43; (xliv) Ab No. 44; (xlv) Ab No. 45; (xlvi) Ab No. 46; (xlvi-a) Ab No. 46a; (xlvi-b) Ab No. 46b; (xlvi-c) Ab No. 46c; (xlvi-d) Ab No. 46d; (xlvi-e) Ab No. 46e; (xlvii) Ab No. 47; (xlviii) Ab No. 48; (xlix) Ab No. 49; (1) Ab No. 50; (li) Ab No. 51; (lii) Ab No. 52; (liii) Ab No. 53; (liv) Ab No. 54; (Iv) Ab No. 55; (Ivi) Ab No. 56; (Ivii) Ab No. 57;(Ivii-a) Ab No. 57a; (Ivii-b) Ab No. 57b; (Ivii-c) Ab No. 57c; (Ivii-d) Ab No. 57d; (Ivii-e) Ab No. 57e; (Ivii-f) Ab No. 57f; (Iviii) Ab No. 58; (lix) Ab No. 59; (lx) Ab No. 60; (Ixi) Ab No. 61; (Ixi-a) Ab No. 61a; (Ixi-b) Ab No. 61b; (Ixi-c) Ab No. 61c;(Ixi-d) Ab No. 61d; (Ixi-e) Ab No. 61e; (Ixii) Ab No. 62; (Ixiii) Ab No. 63; (Ixiv) Ab No. 64; (Ixv) Ab No. 65; (Ixvi) Ab No. 66; (Ixvii) Ab No. 67; (Ixviii) Ab No. 68; (Ixviii-a) Ab No. 68a; (Ixviii-b) Ab No. 68b; (Ixviii-c) Ab No. 68c; (Ixviii-d) Ab No. 68d; (Ixviii-e) Ab No. 68e; (Ixviii-f) Ab No. 68f; (Ixix) Ab No. 69; (Ixx) Ab No. 70; (Ixx-a) Ab No. 70a; (Ixx-b) Ab No. 70b; (Ixx-c) Ab No. 70c; (Ixx-d) Ab No. 70d;(Ixx-e) Ab No. 70e; (Ixx-f) Ab No. 70f; (Ixxi) Ab No. 71; (Ixxii) Ab No. 72; (Ixxiii) Ab No. 73; (Ixxiv) Ab No. 74; (Ixxv) Ab No. 75; (Ixxvi) Ab No. 76; (Ixxvii) Ab No. 77; (Ixxviii) Ab No. 78; (Ixxix) Ab No. 79; (Ixxx) Ab No. 80; (Ixxxi) Ab No. 81; (Ixxxii) Ab No. 82; (Ixxxiii) Ab No. 83; (Ixxxiii-a) Ab No. 83a; (Ixxxiii-b) Ab No. 83b; (Ixxxiii-c) Ab No. 83c; (Ixxxiii-d) Ab No. 83d; (Ixxxiii-e) Ab No. 83e; (Ixxxiii-f) Ab No. 83f; or (Ixxxiv) Ab No. 84.

5. The anti-human CD28 antibody or antigen-binding antibody fragment of any one of claims 1-3, comprising:(A) said VH-1 and said VL-1, wherein the amino acid sequences of the CDRH1-1, the CDRH2-1, the CDRH3-1, the CDRL1-1, the CDRL2-1. and the CDRL3-1 in said VH-1 and VL-1 comprise or consist of:(I) (1) SEQ ID NOS: 112, 114, 116, 122, 124, and 126, respectively; (2) SEQ ID NOS: 2112, 2114, 2116, 2122, 2124, and 2126, respectively; (3) SEQ ID NOS: 2812, 2814. 2816, 2822, 2824, and 2826. respectively; (4) SEQ ID NOS: 4612, 4614. 4616, 4622, 4624, and 4626, respectively; (5) SEQ ID NOS: 5712, 5714, 5716, 5722, 5724, and 5726, respectively; (6) SEQ ID NOS: 6112, 6114, 6116, 6122, 6124, and 6126, respectively; or (7) SEQ ID NOS: 6812, 6814. 6816, 6822, 6824, and 6826, respectively; and / or(II) (i) SEQ ID NOS: 112, 114, 116, 122, 124, and 126, respectively; (ii) SEQ ID NOS: 212, 214, 216, 222, 224, and 226, respectively; (iii) SEQ ID NOS: 312, 314, 316, 322, 324, and 326, respectively; (iv) SEQ ID NOS: 412, 414, 416, 422, 424, and 426, respectively; (v) SEQ ID NOS: 512, 514. 516, 522, 524, and 526, respectively;(vi) SEQ ID NOS: 612, 614, 616, 622, 624, and 626, respectively; (vh) SEQ ID NOS: 712, 714, 716, 722, 724, and 726, respectively; (viii) SEQ ID NOS: 812, 814, 816, 822, 824, and 826, respectively; (ix) SEQ ID NOS: 912, 914, 916, 922, 924, and 926, respectively; (x) SEQ ID NOS: 1012, 1014, 1016, 1022, 1024, and 1026, respectively; (xi) SEQ ID NOS: 1112. 1114, 1116, 1122, 1124. and 1126, respectively; (xh) SEQID NOS: 1212, 1214, 1216, 1222, 1224, and 1226, respectively; (xiii) SEQ ID NOS: 1312. 1314, 1316, 1322, 1324. and 1326, respectively; (xiv) SEQ ID NOS: 1412. 1414, 1416, 1422, 1424, and 1426, respectively; (xv) SEQ ID NOS: 1512, 1514, 1516, 1522, 1524, and 1526, respectively; (xvi) SEQ ID NOS: 1612, 1614, 1616, 1622, 1624, and 1626, respectively; (xvii) SEQ ID NOS: 1712, 1714, 1716, 1722, 1724. and 1726, respectively; (xviii) SEQ ID NOS: 1812, 1814. 1816, 1822, 1824, and 1826, respectively; (xix) SEQ ID NOS: 1912. 1914. 1916, 1922, 1924. and 1926, respectively; (xx) SEQ ID NOS: 2012, 2014, 2016, 2022, 2024, and 2026, respectively; (xxi) SEQ ID NOS: 2112, 2114, 2116, 2122, 2124, and 2126, respectively; (xxi-a) SEQ ID NOS: 2132, 2134, 2136, 2122, 2124, and 2126, respectively; (xxi-b) SEQ ID NOS: 2142, 2144, 2146. 2122, 2124, and 2126. respectively; (xxi-c) SEQ ID NOS: 2152, 2154, 2156, 2122, 2124, and 2126, respectively; (xxi-d) SEQ ID NOS: 2162, 2164, 2166, 2122, 2124, and 2126, respectively; (xxi-e) SEQ ID NOS: 2172, 2174, 2176, 2122, 2124, and 2126, respectively; (xxi-f) SEQ ID NOS: 2182, 2184, 2186, 2122. 2124, and 2126, respectively; (xxn) SEQ ID NOS: 2212. 2214. 2216, 2222, 2224. and 2226, respectively; (xxiii) SEQ ID NOS: 2312, 2314, 2316, 2322, 2324, and 2326, respectively; (xxiv) SEQ ID NOS: 2412, 2414, 2416, 2422, 2424, and 2426, respectively; (xxv) SEQ ID NOS: 2512, 2514, 2516, 2522, 2524, and 2526. respectively; (xxvi) SEQ ID NOS: 2612, 2614, 2616, 2622, 2624. and 2626, respectively; (xxvii) SEQ ID NOS: 2712, 2714, 2716, 2722, 2724, and 2726, respectively; (xxviii) SEQ ID NOS: 2812, 2814, 2816, 2822, 2824, and 2826, respectively; (xxviii-a) SEQ ID NOS: 2832, 2834, 2836, 2822, 2824, and 2826, respectively; (xxviii-b) SEQ ID NOS: 2842, 2844, 2846, 2822, 2824, and 2826, respectively; (xxvin-c) SEQ ID NOS: 2852, 2854, 2856, 2822, 2824, and 2826, respectively; (xxviii-d) SEQ ID NOS: 2862, 2864, 2866, 2822, 2824, and 2826, respectively; (xxviii-e) SEQ ID NOS: 2872, 2874, 2876, 2822, 2824, and 2826, respectively; (xxviii-f) SEQ ID NOS: 2882, 2884, 2886, 2822, 2824, and 2826. respectively; (xxix) SEQ ID NOS: 2912. 2914, 2916, 2922. 2924. and 2926, respectively; (xxx) SEQ ID NOS: 3012, 3014, 3016, 3022, 3024, and 3026, respectively; (xxxi) SEQ ID NOS: 3112, 3114, 3116, 3122, 3124, and 3126, respectively; (xxxii) SEQ ID NOS: 3212, 3214, 3216, 3222, 3224, and 3226, respectively; (xxxiii) SEQ ID NOS: 3312, 3314. 3316, 3322, 3324, and 3326, respectively; (xxxiv) SEQ ID NOS: 3412, 3414, 3416, 3422, 3424, and 3426,respectively; (xxxv) SEQ ID NOS: 3512, 3514, 3516, 3522. 3524, and 3526, respectively; (xxxvi) SEQ ID NOS: 3612, 3614. 3616, 3622, 3624, and 3626. respectively; (xxxvii) SEQ ID NOS: 3712, 3714, 3716, 3722, 3724, and 3726, respectively; (xxxviii) SEQ ID NOS: 3812, 3814, 3816, 3822, 3824, and 3826, respectively; (xxxix) SEQ ID NOS: 3912, 3914, 3916, 3922, 3924, and 3926, respectively; (xl) SEQ ID NOS: 4012, 4014. 4016, 4022, 4024, and 4026, respectively; (xli) SEQ ID NOS: 4112, 4114, 4116, 4122. 4124. and 4126, respectively; (xlii) SEQ ID NOS: 4212, 4214, 4216, 4222, 4224, and 4226, respectively; (xliii) SEQ ID NOS: 4312, 4314, 4316, 4322, 4324, and 4326, respectively; (xliv) SEQ ID NOS: 4412, 4414. 4416, 4422, 4424, and 4426, respectively; (xlv) SEQ ID NOS: 4512, 4514, 4516. 4522, 4524, and 4526, respectively; (xlvi) SEQ ID NOS: 4612, 4614, 4616, 4622, 4624, and 4626, respectively; (xlvi-a) SEQ ID NOS: 4632, 4634, 4636, 4622, 4624, and 4626, respectively; (xlvi-b) SEQ ID NOS: 4642, 4644. 4646, 4622, 4624, and 4626, respectively; (xlvi-c) SEQ ID NOS: 4652, 4654. 4656, 4622, 4624, and 4626, respectively; (xlvi-d) SEQ ID NOS: 4662. 4664. 4666, 4622, 4624. and 4626, respectively; (xlvi-e) SEQ ID NOS: 4672, 4674, 4676, 4622, 4624, and 4626, respectively; (xlvii) SEQ ID NOS: 4712, 4714, 4716, 4722, 4724, and 4726, respectively; (xlviii) SEQ ID NOS: 4812, 4814, 4816, 4822, 4824, and 4826, respectively; (xlix) SEQ ID NOS: 4912. 4914. 4916, 4922, 4924, and 4926, respectively; (1) SEQ ID NOS: 5012, 5014, 5016, 5022, 5024, and 5026, respectively; (li) SEQ ID NOS: 5112, 5114, 5116, 5122, 5124, and 5126, respectively; (lii) SEQ ID NOS: 5212, 5214, 5216, 5222, 5224, and 5226, respectively; (liii) SEQ ID NOS: 5312. 5314, 5316, 5322, 5324, and 5326, respectively; (liv) SEQ ID NOS: 5412, 5414, 5416, 5422, 5424, and 5426, respectively; (Iv) SEQ ID NOS: 5512, 5514, 5516, 5522, 5524, and 5526, respectively; (Ivi) SEQ ID NOS: 5612, 5614, 5616, 5622, 5624, and 5626, respectively; (Ivii) SEQ ID NOS: 5712, 5714, 5716, 5722, 5724, and 5726. respectively; (Ivn-a) SEQ ID NOS: 5732, 5734, 5736, 5722, 5724, and 5726. respectively; (Ivn-b) SEQ ID NOS: 5742, 5744. 5746. 5722, 5724, and 5726. respectively; (Ivii-c) SEQ ID NOS: 5752, 5754, 5756, 5722, 5724, and 5726, respectively; (Ivii-d) SEQ ID NOS: 5762, 5764, 5766, 5722, 5724, and 5726, respectively; (Ivii-e) SEQ ID NOS: 5772, 5774, 5776, 5722, 5724, and 5726, respectively; (Ivii-f) SEQ ID NOS: 5782, 5784, 5786, 5722. 5724, and 5726, respectively; (Ivin) SEQ ID NOS: 5812, 5814, 5816, 5822, 5824, and 5826,respectively; (lix) SEQ ID NOS: 5912, 5914, 5916, 5922, 5924. and 5926, respectively; (lx) SEQ ID NOS: 6012, 6014. 6016, 6022, 6024, and 6026, respectively; (Ixi) SEQ ID NOS: 6112, 6114, 6116, 6122, 6124, and 6126, respectively; (Ixi-a) SEQ ID NOS: 6132, 6134, 6136, 6122, 6124, and 6126, respectively; (Ixi-b) SEQ ID NOS: 6142, 6144, 6146, 6122, 6124, and 6126, respectively; (Ixi-c) SEQ ID NOS: 6152, 6154, 6156, 6122, 6124. and 6126, respectively; (Ixi-d) SEQ ID NOS: 6162, 6164, 6166, 6122. 6124, and 6126, respectively; (Ixi-e) SEQ ID NOS: 6172, 6174, 6176, 6122, 6124, and 6126, respectively; (Ixii) SEQ ID NOS: 6212, 6214, 6216, 6222, 6224, and 6226, respectively; (Ixiii) SEQ ID NOS: 6312, 6314. 6316, 6322, 6324, and 6326, respectively; (Ixiv) SEQ ID NOS: 6412, 6414. 6416, 6422, 6424, and 6426, respectively; (Ixv) SEQ ID NOS: 6512, 6514, 6516, 6522, 6524, and 6526, respectively; (Ixvi) SEQ ID NOS: 6612, 6614, 6616, 6622, 6624, and 6626, respectively; (Ixvii) SEQ ID NOS: 6712, 6714, 6716, 6722, 6724. and 6726, respectively; (Ixviii) SEQ ID NOS: 6812, 6814, 6816. 6822, 6824, and 6826, respectively; (Ixvtii-a) SEQ ID NOS: 6832, 6834. 6836. 6822, 6824, and 6826. respectively; (Ixviii-b) SEQ ID NOS: 6842, 6844, 6846, 6822, 6824, and 6826, respectively; (Ixviii-c) SEQ ID NOS: 6852, 6854, 6856, 6822, 6824, and 6826, respectively; (Ixviii-d) SEQ ID NOS: 6862, 6864, 6866. 6822, 6824, and 6826, respectively; (Ixviii-e) SEQ ID NOS: 6872, 6874, 6876. 6822, 6824, and 6826. respectively; (Ixviii-f) SEQ ID NOS: 6882, 6884, 6886, 6822, 6824, and 6826, respectively; or (Ixix) SEQ ID NOS: 6912, 6914, 6916, 6922, 6924, and 6926, respectively; or(B) said VH-1 and optionally said VL-1, wherein the amino acid sequences of the CDRH1-1, the CDRH2-1, and the CDRH3-1 in said VH-1 comprise or consist of:(I) (1) SEQ ID NOS: 7012, 7014, and 7016, respectively; or (2) SEQ ID NOS: 8312, 8314, and 8316, respectively; and / or(II) (i) SEQ ID NOS: 112, 114, and 116. respectively; (h) SEQ ID NOS:

212. 214, and 216, respectively; (iii) SEQ ID NOS: 312, 314, and 316, respectively; (iv) SEQ ID NOS: 412, 414, and 416, respectively; (v) SEQ ID NOS: 512, 514, and 516, respectively; (vi) SEQ ID NOS: 612, 614, and 616, respectively; (vii) SEQ ID NOS: 712, 714. and 716, respectively; (viii) SEQ ID NOS: 812, 814, and 816, respectively;(ix) SEQ ID NOS: 912, 914, and 916, respectively; (x) SEQ ID NOS: 1012, 1014, and 1016. respectively; (xi) SEQ ID NOS: 1112. 1114, and 1116, respectively; (xii) SEQ ID NOS: 1212, 1214, and 1216, respectively; (xiii) SEQ ID NOS: 1312, 1314, and 1316, respectively; (xiv) SEQ ID NOS: 1412, 1414, and 1416, respectively; (xv) SEQ ID NOS: 1512, 1514, and 1516, respectively; (xvi) SEQ ID NOS: 1612, 1614, and 1616. respectively; (xvii) SEQ ID NOS: 1712. 1714, and 1716, respectively; (xviii) SEQ ID NOS: 1812, 1814. and 1816, respectively; (xix) SEQ ID NOS: 1912. 1914, and 1916, respectively; (xx) SEQ ID NOS: 2012, 2014, and 2016, respectively; (xxi) SEQ ID NOS: 2112, 2114, and 2116, respectively; (xxi-a) SEQ ID NOS: 2132, 2134, and 2136, respectively: (xxi-b) SEQ ID NOS: 2142, 2144, and 2146, respectively; (xxi-c) SEQ ID NOS: 2152, 2154, and 2156, respectively: (xxi-d) SEQ ID NOS: 2162, 2164, and 2166, respectively; (xxi-e) SEQ ID NOS: 2172, 2174, and 2176, respectively; (xxi-f) SEQ ID NOS: 2182, 2184, and 2186, respectively; (xxii) SEQ ID NOS: 2212, 2214, and 2216, respectively; (xxiii) SEQ ID NOS: 2312, 2314, and 2316. respectively; (xxiv) SEQ ID NOS: 2412, 2414, and 2416. respectively; (xxv) SEQ ID NOS: 2512. 2514. and 2516, respectively; (xxvi) SEQ ID NOS: 2612, 2614. and 2616, respectively; (xxvii) SEQ ID NOS: 2712, 2714, and 2716, respectively; (xxviii) SEQ ID NOS: 2812, 2814, and 2816, respectively; (xxviii-a) SEQ ID NOS: 2832, 2834, and 2836, respectively; (xxviii-b) SEQ ID NOS: 2842, 2844, and 2846, respectively; (xxviii-c) SEQ ID NOS: 2852. 2854. and 2856, respectively; (xxviii-d) SEQ ID NOS: 2862, 2864, and 2866, respectively; (xxviii-e) SEQ ID NOS: 2872, 2874, and 2876, respectively; (xxviii-f) SEQ ID NOS: 2882, 2884, and 2886, respectively; (xxix) SEQ ID NOS: 2912, 2914, and 2916, respectively; (xxx) SEQ ID NOS: 3012, 3014, and 3016, respectively; (xxxi) SEQ ID NOS: 3112, 3114, and 3116, respectively; (xxxii) SEQ ID NOS: 3212, 3214, and 3216, respectively; (xxxiii) SEQ ID NOS: 3312, 3314, and 3316, respectively; (xxxiv) SEQ ID NOS: 3412, 3414, and 3416, respectively; (xxxv) SEQ ID NOS: 3512, 3514, and 3516, respectively; (xxxvi) SEQ ID NOS: 3612, 3614. and 3616, respectively; (xxxvii) SEQ ID NOS: 3712. 3714, and 3716, respectively; (xxxvm) SEQ ID NOS: 3812, 3814, and 3816. respectively; (xxxix) SEQ ID NOS: 3912, 3914, and 3916, respectively; (xl) SEQ ID NOS: 4012, 4014, and 4016, respectively; (xli) SEQ ID NOS: 4112, 4114, and 4116, respectively; (xlii) SEQ ID NOS: 4212, 4214, and 4216, respectively: (xliii) SEQ ID NOS: 4312, 4314, and 4316. respectively; (xliv) SEQ ID NOS: 4412. 4414, and 4416, respectively; (xlv) SEQ ID NOS: 4512, 4514, and 4516, respectively; (xlvi) SEQ IDNOS: 4612, 4614, and 4616, respectively; (xlvi-a) SEQ ID NOS: 4632, 4634, and 4636. respectively; (xlvi-b) SEQ ID NOS: 4642, 4644, and 4646, respectively; (xlvi- c) SEQ ID NOS: 4652, 4654, and 4656, respectively; (xlvi-d) SEQ ID NOS: 4662, 4664, and 4666, respectively; (xlvi-e) SEQ ID NOS: 4672, 4674, and 4676, respectively; (xlvii) SEQ ID NOS: 4712, 4714, and 4716, respectively; (xlviii) SEQ ID NOS: 4812, 4814, and 4816, respectively; (xlix) SEQ ID NOS: 4912, 4914, and 4916. respectively; (1) SEQ ID NOS: 5012, 5014, and 5016. respectively; (li) SEQ ID NOS: 5112, 5114, and 5116, respectively; (lii) SEQ ID NOS: 5212, 5214, and 5216, respectively; (liii) SEQ ID NOS: 5312, 5314, and 5316, respectively; (liv) SEQ ID NOS: 5412, 5414, and 5416, respectively; (Iv) SEQ ID NOS: 5512, 5514, and 5516, respectively; (Ivi) SEQ ID NOS: 5612, 5614, and 5616, respectively; (Ivii) SEQ ID NOS: 5712, 5714, and 5716, respectively; (Ivii-a) SEQ ID NOS: 5732, 5734, and 5736, respectively; (Ivii-b) SEQ ID NOS: 5742, 5744, and 5746, respectively; (Ivii-c) SEQ ID NOS: 5752, 5754, and 5756, respectively; (Ivii-d) SEQ ID NOS: 5762, 5764, and 5766, respectively: (Ivii-e) SEQ ID NOS: 5772. 5774, and 5776, respectively; (Ivii-f) SEQ ID NOS: 5782, 5784. and 5786. respectively; (Ivin) SEQ ID NOS: 5812, 5814, and 5816, respectively; (lix) SEQ ID NOS: 5912, 5914, and 5916, respectively; (lx) SEQ ID NOS: 6012, 6014, and 6016, respectively; (Ixi) SEQ ID NOS: 6112, 6114, and 6116, respectively; (Ixi-a) SEQ ID NOS: 6132, 6134. and 6136, respectively; (Ixi-b) SEQ ID NOS: 6142, 6144, and 6146. respectively; (Ixi-c) SEQ ID NOS: 6152, 6154, and 6156, respectively; (Ixi-d) SEQ ID NOS: 6162, 6164, and 6166, respectively; (Ixi-e) SEQ ID NOS: 6172, 6174, and 6176, respectively; (Ixii) SEQ ID NOS: 6212, 6214, and 6216, respectively; (Ixiii) SEQ ID NOS: 6312, 6314, and 6316, respectively: (Ixiv) SEQ ID NOS: 6412, 6414, and 6416, respectively; (Ixv) SEQ ID NOS: 6512, 6514, and 6516, respectively; (Ixvi) SEQ ID NOS: 6612, 6614, and 6616, respectively; (Ixvii) SEQ ID NOS: 6712, 6714, and 6716, respectively; (Ixviii) SEQ ID NOS: 6812, 6814, and 6816, respectively; (Ixviii-a) SEQ ID NOS: 6832. 6834, and 6836, respectively; (Ixviii-b) SEQ ID NOS: 6842, 6844, and 6846, respectively; (Ixviii-c) SEQ ID NOS: 6852, 6854. and 6856, respectively: (Ixviii-d) SEQ ID NOS: 6862, 6864, and 6866, respectively; (Ixvni-e) SEQ ID NOS: 6872, 6874, and 6876, respectively; (Ixviii-f) SEQ ID NOS: 6882, 6884, and 6886, respectively; (Ixix) SEQ ID NOS: 6912, 6914, and 6916, respectively; (Ixx) SEQ ID NOS: 7012, 7014, and 7016. respectively; (Ixx-a) SEQ ID NOS: 7032, 7034, and 7036, respectively; (Ixx-b) SEQ ID NOS: 7042, 7044, and 7046, respectively; (Ixx-c)SEQ ID NOS: 7052, 7054, and 7056, respectively; (Ixx-d) SEQ ID NOS: 7062, 7064, and 7066, respectively: (Ixx-e) SEQ ID NOS: 7072, 7074. and 7076, respectively; (Ixx-f) SEQ ID NOS: 7082, 7084, and 7086, respectively; (Ixxi) SEQ ID NOS: 7112, 7114, and 7116, respectively; (Ixxii) SEQ ID NOS: 7212, 7214, and 7216, respectively; (Ixxiii) SEQ ID NOS: 7312, 7314, and 7316, respectively; (Ixxiv) SEQ ID NOS: 7412, 7414, and 7416, respectively; (Ixxv) SEQ ID NOS: 7512, 7514, and 7516. respectively; (Ixxvi) SEQ ID NOS: 7612, 7614. and 7616, respectively; (Ixxvii) SEQ ID NOS: 7712, 7714, and 7716, respectively; (Ixxvin) SEQ ID NOS: 7812, 7814, and 7816, respectively; (Ixxix) SEQ ID NOS: 7912, 7914, and 7916, respectively; (Ixxx) SEQ ID NOS: 8012, 8014, and 8016, respectively; (Ixxxi) SEQ ID NOS: 8112. 8114, and 8116, respectively; (Ixxxii) SEQ ID NOS: 8212, 8214. and 8216, respectively; (Ixxxiii) SEQ ID NOS: 8312, 8314, and 8316, respectively;(Ixxxiii-a) SEQ ID NOS: 8332, 8334, and 8336, respectively; (Ixxxiii-b) SEQ ID NOS: 8342, 8344, and 8346, respectively; (Ixxxiii-c) SEQ ID NOS: 8352, 8354, and 8356. respectively; (Ixxxiii-d) SEQ ID NOS: 8362, 8364, and 8366, respectively; (Ixxxiii-e) SEQ ID NOS: 8372, 8374, and 8376. respectively; (Ixxxiii-f) SEQ ID NOS: 8382, 8384, and 8386, respectively; or (Ixxxiv) SEQ ID NOS: 8412, 8414, and 8416, respectively.

6. The anti-human CD28 antibody or antigen-binding antibody fragment of any one of claims 1-5. wherein: the amino acid sequence of the VH-1 comprises or consists of one of the VH amino acid sequences listed in Table 1A and / or 12A or a variant thereof having at least about 80%, 85%, 90%. 91%. 92%. 93%. 94%. 95%. 96%. 97%. 98%. or 99% sequence identity thereto; the amino acid sequence of the VL-1 comprises or consists of one of the VL amino acid sequences listed in Table 1A and / or 12A or a variant thereof having at least about 80%, 85%, 90%, 91%, 92%. 93%. 94%. 95%. 96%. 97%. 98%. or 99% sequence identity thereto; the amino acid sequence of the VH-1 is encoded by a nucleic acid sequence comprising or consisting of one of the VH-encoding nucleic acid sequences listed in Table 2A and / or 13A or a variant thereof having at least about 80%, 85%, 90%,91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and / or the amino acid sequence of the VL-1 is encoded by a nucleic acid sequence comprising or consisting of any one of the VL-encoding nucleic acid sequence listed in Table 2A and / or 13A or a variant thereof having at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto.

7. The anti-human CD28 antibody or antigen-binding antibody fragment of claim 4 or 5, wherein: in (A), the amino acid sequences of the VH-1 and the VL-1 have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least or at least about 99% sequence identity to: in (I), in (1), SEQ ID NOS: 110 and 120, respectively; in (2), SEQ ID NOS: 2110 and 2120, respectively; in (3), SEQ ID NOS: 2810 and 2820, respectively; in (4), SEQ ID NOS: 4610 and 4620, respectively; in (5), SEQ ID NOS: 5710 and 5720, respectively; in (6), SEQ ID NOS: 6110 and 6120, respectively; or in (7), SEQ ID NOS: 6810 and 6820. respectively; and / or in (II), in (i), SEQ ID NOS: 110 and 120, respectively; in (ii), SEQ ID NOS: 210 and 220, respectively; in (iii), SEQ ID NOS: 310 and 320, respectively; in (iv), SEQ ID NOS: 410 and 420, respectively; in (v), SEQ ID NOS: 510 and 520, respectively; in (vi), SEQ ID NOS: 610 and 620. respectively; in (vii). SEQ ID NOS: 710 and 720, respectively; in (viii), SEQ ID NOS: 810 and 820. respectively; in (ix), SEQ ID NOS: 910 and 920, respectively; in (x), SEQ ID NOS: 1010 and 1020, respectively; in (xi), SEQ ID NOS: 1110 and 1120, respectively; in (xii), SEQ ID NOS: 1210 and 1220, respectively; in (xiii), SEQ ID NOS: 1310 and 1320, respectively; in (xiv), SEQ ID NOS: 1410 and 1420, respectively; in (xv), SEQ ID NOS: 1510 and 1520, respectively; in (xvi), SEQ ID NOS: 1610 and 1620, respectively; in (xvii), SEQ ID NOS: 1710 and 1720, respectively; in (xviii), SEQ ID NOS: 1810 and 1820, respectively; in (xix), SEQ ID NOS: 1910 and 1920, respectively; in (xx), SEQ ID NOS: 2010 and 2020, respectively; in (xxi), SEQ ID NOS: 2110 and 2120,respectively; in (xxi-a), SEQ ID NOS: 2130 and 2120, respectively; in (xxi-b), SEQ ID NOS: 2140 and 2120. respectively; in (xxi-c), SEQ ID NOS: 2150 and 2120, respectively; in (xxi-d), SEQ ID NOS: 2160 and 2120, respectively; in (xxi-e), SEQ ID NOS: 2170 and 2120, respectively; in (xxi-f), SEQ ID NOS: 2180 and 2120, respectively; in (xxii), SEQ ID NOS: 2210 and 2220, respectively; in (xxiii), SEQ ID NOS: 2310 and 2320, respectively; in (xxiv), SEQ ID NOS: 2410 and 2420, respectively; in (xxv), SEQ ID NOS: 2510 and 2520, respectively; in (xxvi), SEQ ID NOS: 2610 and 2620, respectively; in (xxvii), SEQ ID NOS: 2710 and 2720, respectively; in (xxviii), SEQ ID NOS: 2810 and 2820, respectively; in (xxviii-a), SEQ ID NOS: 2830 and 2820, respectively; in (xxviii-b), SEQ ID NOS: 2840 and 2820. respectively; in (xxviii-c), SEQ ID NOS: 2850 and 2820, respectively; in (xxviii-d), SEQ ID NOS: 2860 and 2820, respectively; in (xxviii-e), SEQ ID NOS: 2870 and 2820, respectively; in (xxviii-f), SEQ ID NOS: 2880 and 2820, respectively; in (xxix), SEQ ID NOS: 2910 and 2920, respectively; in (xxx), SEQ ID NOS: 3010 and 3020, respectively: in (xxxi), SEQ ID NOS: 3110 and 3120, respectively; in (xxxn). SEQ ID NOS: 3210 and 3220. respectively; in (xxxiti). SEQ ID NOS: 3310 and 3320, respectively; in (xxxiv), SEQ ID NOS: 3410 and 3420, respectively; in (xxxv), SEQ ID NOS: 3510 and 3520, respectively; in (xxxvi), SEQ ID NOS: 3610 and 3620, respectively: in (xxxvii), SEQ ID NOS: 3710 and 3720, respectively; in (xxxviii). SEQ ID NOS: 3810 and 3820. respectively; in (xxxix), SEQ ID NOS: 3910 and 3920, respectively; in (xl), SEQ ID NOS: 4010 and 4020, respectively; in (xli), SEQ ID NOS: 4110 and 4120, respectively; in (xlii), SEQ ID NOS: 4210 and 4220, respectively; in (xliii), SEQ ID NOS: 4310 and 4320, respectively; in (xliv), SEQ ID NOS: 4410 and 4420, respectively; in (xlv), SEQ ID NOS: 4510 and 4520, respectively; in (xlvi), SEQ ID NOS: 4610 and 4620, respectively; in (xlvi-a), SEQ ID NOS: 4630 and 4620, respectively; in (xlvi-b), SEQ ID NOS: 4640 and 4620, respectively; in (xlvi-c), SEQ ID NOS: 4650 and 4620, respectively; in (xlvi-d), SEQ ID NOS: 4660 and 4620. respectively; in (xlvi-e), SEQ ID NOS: 4670 and 4620, respectively; in (xlvii). SEQ ID NOS: 4710 and 4720. respectively; in (xlviii), SEQ ID NOS: 4810 and 4820, respectively; in (xlix), SEQ ID NOS: 4910 and 4920, respectively; in (1), SEQ ID NOS: 5010 and 5020, respectively; in (li), SEQ ID NOS: 5110 and 5120. respectively; in (lii), SEQ ID NOS: 5210 and 5220, respectively; in (liii), SEQ ID NOS: 5310 and 5320, respectively; in (liv), SEQ ID NOS: 5410 and 5420, respectively; in (Iv), SEQ ID NOS: 5510 and 5520, respectively; in (Ivi), SEQID NOS: 5610 and 5620, respectively; in (Ivii), SEQ ID NOS: 5710 and 5720, respectively; in (Ivii-a), SEQ ID NOS: 5730 and 5720, respectively; in (Ivii-b), SEQ ID NOS: 5740 and 5720, respectively; in (Ivii-c), SEQ ID NOS: 5750 and 5720, respectively; in (Ivii-d), SEQ ID NOS: 5760 and 5720, respectively; in (Ivii-e), SEQ ID NOS: 5770 and 5720, respectively; in (Ivii-f), SEQ ID NOS: 5780 and 5720, respectively; in (Iviii), SEQ ID NOS: 5810 and 5820, respectively; in (lix), SEQ ID NOS: 5910 and 5920, respectively; in (lx). SEQ ID NOS: 6010 and 6020, respectively; in (Ixi), SEQ ID NOS: 6110 and 6120, respectively; in (Ixi-a), SEQ ID NOS: 6130 and 6120, respectively; in (Ixi-b), SEQ ID NOS: 6140 and 6120, respectively; in (Ixi-c), SEQ ID NOS: 6150 and 6120, respectively; in (Ixi-d). SEQ ID NOS: 6160 and 6120, respectively; in (Ixi-e), SEQ ID NOS: 6170 and 6120, respectively; in (Ixii), SEQ ID NOS: 6210 and 6220, respectively; in (Ixiii), SEQ ID NOS: 6310 and 6320, respectively; in (Ixiv), SEQ ID NOS: 6410 and 6420, respectively; in (Ixv), SEQ ID NOS: 6510 and 6520, respectively; in (Ixvi), SEQ ID NOS: 6610 and 6620, respectively; in (Ixvii), SEQ ID NOS: 6710 and 6720, respectively; in (Ixviii), SEQ ID NOS: 6810 and 6820, respectively; in (Ixviii-a). SEQ ID NOS: 6830 and 6820, respectively; in (Ixviii-b), SEQ ID NOS: 6840 and 6820, respectively; in (Ixviii-c), SEQ ID NOS: 6850 and 6820, respectively; in (Ixviii-d), SEQ ID NOS: 6860 and 6820, respectively; in (Ixviii-e), SEQ ID NOS: 6870 and 6820. respectively; in (Ixviii-f), SEQ ID NOS: 6880 and 6820, respectively; or in (Ixix), SEQ ID NOS: 6910 and 6920, respectively; or in (B), the amino acid sequence of the VH-1 has at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%. at least about 93%, at least about 94%. at least about 95%. at least about 96%, at least about 97%, at least about 98%, at least or at least about 99% sequence identity to: in (I), in (1), SEQ ID NO: 7010; or in (2), SEQ ID NO: 8310; and / or in (II), in (i), SEQ ID NO: 110; in (ii), SEQ ID NO: 210; in (iii), SEQ ID NO: 310; in (iv), SEQ ID NO: 410; in (v), SEQ ID NO: 510; in (vi). SEQ ID NO: 610; in (vn), SEQ ID NO: 710; in (v iii ), SEQ ID NO: 810; in (ix), SEQ ID NO: 910; in (x), SEQ ID NO : 1010; in (xi), SEQ ID NO : 1110; in (xii), SEQ ID NO : 1210; in (xiii), SEQ ID NO: 1310; in (xiv), SEQ ID NO: 1410; in (xv), SEQ ID NO: 1510; in (xvi), SEQ ID NO: 1610; in (xvii). SEQ ID NO: 1710; in (xviii), SEQ ID NO: 1810; in (xix),SEQ ID NO: 1910; in (xx), SEQ ID NO: 2010; in (xxi), SEQ ID NO: 2110; in (xxi-a), SEQ ID NO: 2130; in (xx-b), SEQ ID NO: 2140; in (xxi-c). SEQ ID NO: 2150; in (xxi-d), SEQ ID NO: 2160; in (xxi-e), SEQ ID NO: 2170; in (xxi-f), SEQ ID NO: 2180; in (xxii), SEQ ID NO: 2210; in (xxiii), SEQ ID NO: 2310; in (xxiv), SEQ ID NO: 2410; in (xxv), SEQ ID NO: 2510; in (xxvi), SEQ ID NO: 2610; in (xxvii), SEQ ID NO: 2710; in (xxvin). SEQ ID NO: 2810; in (xxviii-a), SEQ ID NO: 2830; in (xxviii-b), SEQ ID NO: 2840; in (xxviii-c), SEQ ID NO: 2850; in (xxviii-d), SEQ ID NO: 2860; in (xxviii-e), SEQ ID NO: 2870; in (xxviii-f), SEQ ID NO: 2880; in (xxix), SEQ ID NO: 2910; in (xxx), SEQ ID NO: 3010; in (xxxi), SEQ ID NO: 3110; in (xxxii), SEQ ID NO: 3210; in (xxxiii), SEQ ID NO: 3310; in (xxxiv). SEQ ID NO: 3410; in (xxxv), SEQ ID NO: 3510; in (xxxvi), SEQ ID NO: 3610; in (xxxvii), SEQ ID NO: 3710; in (xxxviii), SEQ ID NO: 3810; in (xxxix), SEQ ID NO: 3910; in (xl), SEQ ID NO: 4010; in (xli), SEQ ID NO: 4110; in (xlii), SEQ ID NO: 4210; in (xliii), SEQ ID NO: 4310; in (xliv), SEQ ID NO: 4410; in (xlv), SEQ ID NO: 4510; in (xlvi), SEQ ID NO: 4610; in (xlvi-a), SEQ ID NO: 4630; in (xlvi-b). SEQ ID NO: 4640; in (xlvi-c), SEQ ID NO: 4650; in (xlvi-d), SEQ ID NO: 4660; in (xlvi-e), SEQ ID NO: 4670; in (xlvii), SEQ ID NO: 4710; in (xlviii), SEQ ID NO: 4810; in (xlix), SEQ ID NO: 4910; in (1), SEQ ID NO: 5010; in (li), SEQ ID NO: 5110; in (lii), SEQ ID NO: 5210; in (liii), SEQ ID NO: 5310; in (liv), SEQ ID NO: 5410; in (Iv), SEQ ID NO: 5510; in (Ivi), SEQ ID NO: 5610; in (Ivii). SEQ ID NO: 5710; in (Ivii-a). SEQ ID NO: 5730; in (Ivii-b), SEQ ID NO: 5740; in (Ivii-c), SEQ ID NO: 5750; in (Ivii-d), SEQ ID NO: 5760; in (Ivii-e), SEQ ID NO: 5770; in (Ivii-f), SEQ ID NO: 5780; in (Iviii), SEQ ID NO: 5810; in (lix), SEQ ID NO: 5910; in (lx), SEQ ID NO: 6010; in (Ixi), SEQ ID NO: 6110; in (Ixi-a). SEQ ID NO: 6130; in (Ixi-b), SEQ ID NO: 6140; in (Ixi-c), SEQ ID NO: 6150; in (Ixi-d), SEQ ID NO: 6160; in (Ixi-e), SEQ ID NO: 6170; in (Ixii), SEQ ID NO: 6210; in (Ixiii), SEQ ID NO: 6310; in (Ixiv), SEQ ID NO: 6410; in (Ixv), SEQ ID NO: 6510; in (Ixvi), SEQ ID NO: 6610; in (Ixvii), SEQ ID NO: 6710; in (Ixviii), SEQ ID NO: 6810; in (Ixviii-a), SEQ ID NO: 6830; in (Ixviii-b). SEQ ID NO: 6840; in (Ixviii-c). SEQ ID NO: 6850; in (Ixviii-d), SEQ ID NO: 6860; in (Ixviii-e), SEQ ID NO: 6870; in (Ixviii-f), SEQ ID NO: 6880; in (Ixix), SEQ ID NO: 6910; in (Ixx), SEQ ID NO: 7010; in (Ixx-a), SEQ ID NO: 7030; in (Ixx- b), SEQ ID NO: 7040; in (Ixx-c), SEQ ID NO: 7050; in (Ixx-d), SEQ ID NO: 7060; in (Ixx-e). SEQ ID NO: 7070; in (Ixx-f), SEQ ID NO: 7080; in (Ixxi), SEQ ID NO: 7110; in (Ixxii), SEQ ID NO: 7210; in (Ixxni), SEQ ID NO: 7310; in (Ixxiv), SEQ IDNO: 7410; in (Ixxv), SEQ ID NO: 7510; in (Ixxvi), SEQ ID NO: 7610; in (Ixxvii), SEQ ID NO: 7710; in (Ixxviii), SEQ ID NO: 7810; or in (Ixxix), SEQ ID NO: 7910; in (Ixxx), SEQ ID NO: 8010; in (Ixxxi), SEQ ID NO: 8110; in (Ixxxii), SEQ ID NO: 8210; in (Ixxxiii), SEQ ID NO: 8310; in (Ixxxiii-a), SEQ ID NO: 8330; in (Ixxxiii-b), SEQ ID NO: 8340; in (Ixxxiii-c), SEQ ID NO: 8350; in (Ixxxiii-d), SEQ ID NO: 8360; in (Ixxxiii-e), SEQ ID NO: 8370; in (Ixxxiii-f), SEQ ID NO: 8380; or in (Ixxxiv), SEQ ID NO: 8410.

8. The anti-human CD28 antibody or antigen-binding antibody fragment of any one of claims 4, 5, or 7, wherein: in (A), the amino acid sequences of the VH-1 and the VL-1 comprise or consist of: in (I), in (1), SEQ ID NOS: 110 and 120, respectively; in (2), SEQ ID NOS: 2110 and 2120, respectively; in (3), SEQ ID NOS: 2810 and 2820, respectively; in (4), SEQ ID NOS: 4610 and 4620, respectively; in (5), SEQ ID NOS: 5710 and 5720, respectively; in (6), SEQ ID NOS: 6110 and 6120, respectively; or in (7). SEQ ID NOS: 6810 and 6820, respectively; and / or in (II), in (i), SEQ ID NOS: 110 and 120, respectively; in (ii), SEQ ID NOS: 210 and 220, respectively; in (iii), SEQ ID NOS: 310 and 320, respectively; in (iv), SEQ ID NOS: 410 and 420. respectively; in (v), SEQ ID NOS: 510 and 520, respectively; in (vi), SEQ ID NOS: 610 and 620, respectively; in (vn), SEQ ID NOS: 710 and 720, respectively; in (viii), SEQ ID NOS: 810 and 820, respectively; in (ix), SEQ ID NOS: 910 and 920, respectively; in (x), SEQ ID NOS: 1010 and 1020, respectively; in (xi), SEQ ID NOS: 1110 and 1120, respectively; in (xii), SEQ ID NOS: 1210 and 1220, respectively; in (xiii), SEQ ID NOS: 1310 and 1320, respectively; in (xiv), SEQ ID NOS: 1410 and 1420, respectively; in (xv), SEQ ID NOS: 1510 and 1520, respectively; in (xvi), SEQ ID NOS: 1610 and 1620, respectively; in (xvii), SEQ ID NOS: 1710 and 1720, respectively; in (xviii), SEQ ID NOS: 1810 and 1820, respectively; in (xix), SEQ ID NOS: 1910 and 1920, respectively; in (xx), SEQ ID NOS: 2010 and 2020, respectively; in (xxi), SEQ ID NOS: 2110 and 2120, respectively; in (xxi-a), SEQ ID NOS: 2130 and 2120, respectively; in (xxi-b), SEQ ID NOS: 2140 and 2120, respectively; in (xxi-c), SEQ ID NOS: 2150 and 2120, respectively; in (xxi-d), SEQ ID NOS: 2160 and 2120, respectively; in (xxi-e), SEQ ID NOS: 2170 and 2120. respectively; in (xxi-f), SEQ ID NOS: 2180 and 2120,respectively; in (xxii), SEQ ID NOS: 2210 and 2220, respectively; in (xxiii), SEQ ID NOS: 2310 and 2320, respectively; in (xxiv), SEQ ID NOS: 2410 and 2420, respectively; in (xxv), SEQ ID NOS: 2510 and 2520, respectively; in (xxvi), SEQ ID NOS: 2610 and 2620, respectively; in (xxvii), SEQ ID NOS: 2710 and 2720, respectively; in (xxviii), SEQ ID NOS: 2810 and 2820, respectively; in (xxviii-a), SEQ ID NOS: 2830 and 2820, respectively; in (xxviii-b), SEQ ID NOS: 2840 and 2820. respectively; in (xxviii-c), SEQ ID NOS: 2850 and 2820. respectively; in (xxviii-d), SEQ ID NOS: 2860 and 2820, respectively; in (xxviii-e), SEQ ID NOS: 2870 and 2820, respectively; in (xxviii-f), SEQ ID NOS: 2880 and 2820, respectively; in (xxix), SEQ ID NOS: 2910 and 2920, respectively; in (xxx), SEQ ID NOS: 3010 and 3020, respectively: in (xxxi), SEQ ID NOS: 3110 and 3120, respectively; in (xxxii), SEQ ID NOS: 3210 and 3220, respectively; in (xxxiii), SEQ ID NOS: 3310 and 3320, respectively; in (xxxiv), SEQ ID NOS: 3410 and 3420, respectively; in (xxxv), SEQ ID NOS: 3510 and 3520, respectively; in (xxxvi), SEQ ID NOS: 3610 and 3620, respectively: in (xxxvii), SEQ ID NOS: 3710 and 3720, respectively; in (xxxviii). SEQ ID NOS: 3810 and 3820. respectively; in (xxxix), SEQ ID NOS: 3910 and 3920, respectively; in (xl), SEQ ID NOS: 4010 and 4020, respectively; in (xli), SEQ ID NOS: 4110 and 4120, respectively; in (xlii), SEQ ID NOS: 4210 and 4220, respectively; in (xliii), SEQ ID NOS: 4310 and 4320, respectively; in (xliv), SEQ ID NOS: 4410 and 4420, respectively; in (xlv), SEQ ID NOS: 4510 and 4520, respectively; in (xlvi), SEQ ID NOS: 4610 and 4620, respectively; in (xlvi-a), SEQ ID NOS: 4630 and 4620, respectively; in (xlvi-b), SEQ ID NOS: 4640 and 4620, respectively; in (xlvi-c), SEQ ID NOS: 4650 and 4620, respectively; in (xlvi-d), SEQ ID NOS: 4660 and 4620. respectively; in (xlvi-e), SEQ ID NOS: 4670 and 4620, respectively; in (xlvii), SEQ ID NOS: 4710 and 4720, respectively; in (xlviii), SEQ ID NOS: 4810 and 4820, respectively; in (xlix), SEQ ID NOS: 4910 and 4920, respectively; in (1), SEQ ID NOS: 5010 and 5020, respectively; in (li), SEQ ID NOS: 5110 and 5120. respectively: in (lii), SEQ ID NOS: 5210 and 5220, respectively; in (liii), SEQ ID NOS: 5310 and 5320, respectively; in (liv). SEQ ID NOS: 5410 and 5420, respectively; in (Iv), SEQ ID NOS: 5510 and 5520, respectively; in (Ivi), SEQ ID NOS: 5610 and 5620, respectively; in (Ivii), SEQ ID NOS: 5710 and 5720, respectively; in (Ivii-a), SEQ ID NOS: 5730 and 5720, respectively; in (Ivii-b), SEQ ID NOS: 5740 and 5720. respectively; in (Ivii-c), SEQ ID NOS: 5750 and 5720, respectively; in (Ivii-d), SEQ ID NOS: 5760 and 5720, respectively; in (Ivii-e), SEQID NOS: 5770 and 5720, respectively; in (Ivii-f), SEQ ID NOS: 5780 and 5720, respectively; in (Iviii), SEQ ID NOS: 5810 and 5820, respectively; in (lix), SEQ ID NOS: 5910 and 5920, respectively; in (lx), SEQ ID NOS: 6010 and 6020, respectively; in (Ixi), SEQ ID NOS: 6110 and 6120, respectively; in (Ixi-a), SEQ ID NOS: 6130 and 6120, respectively; in (Ixi-b), SEQ ID NOS: 6140 and 6120, respectively; in (Ixi-c), SEQ ID NOS: 6150 and 6120, respectively; in (Ixi-d). SEQ ID NOS: 6160 and 6120, respectively; in (Ixi-e), SEQ ID NOS: 6170 and 6120, respectively; in (Ixii), SEQ ID NOS: 6210 and 6220, respectively; in (Ixiii), SEQ ID NOS: 6310 and 6320, respectively; in (Ixiv), SEQ ID NOS: 6410 and 6420, respectively; in (Ixv), SEQ ID NOS: 6510 and 6520, respectively; in (Ixvi), SEQ ID NOS: 6610 and 6620, respectively; in (Ixvii), SEQ ID NOS: 6710 and 6720, respectively; in (Ixviii), SEQ ID NOS: 6810 and 6820, respectively; in (Ixviii-a), SEQ ID NOS: 6830 and 6820, respectively; in (Ixviii-b), SEQ ID NOS: 6840 and 6820, respectively; in (Ixviii-c), SEQ ID NOS: 6850 and 6820, respectively; in (Ixviii-d), SEQ ID NOS: 6860 and 6820, respectively; in (Ixviii-e), SEQ ID NOS: 6870 and 6820. respectively; in (Ixviii-f), SEQ ID NOS: 6880 and 6820, respectively; or in (Ixix), or SEQ ID NOS: 6910 and 6920, respectively; or in (B), the amino acid sequence of the VH-1 comprises or consists of: in (I), in (1) SEQ ID NO: 7010; or in (2), SEQ ID NO: 8310; and / or in (II), in (i), SEQ ID NO: 110; in (ii), SEQ ID NO: 210; in (hi), SEQ ID NO: 310; in (iv), SEQ ID NO: 410; in (v), SEQ ID NO: 510; in (vi), SEQ ID NO: 610; in (vii), SEQ ID NO: 710; in (viii), SEQ ID NO: 810; in (ix), SEQ ID NO: 910; in (x), SEQ ID NO: 1010; in (xi). SEQ ID NO: 1110; in (xii), SEQ ID NO: 1210; in (xiii), SEQ ID NO: 1310; in (xiv), SEQ ID NO: 1410; in (xv), SEQ ID NO: 1510; in (xvi), SEQ ID NO: 1610; in (xvii), SEQ ID NO: 1710; in (xviii), SEQ ID NO: 1810; in (xix), SEQ ID NO: 1910; in (xx), SEQ ID NO: 2010; in (xxi), SEQ ID NO: 2110; in (xxi-a), SEQ ID NO: 2130; in (xx-b), SEQ ID NO: 2140; in (xxi-c), SEQ ID NO: 2150; in (xxi-d). SEQ ID NO: 2160; in (xxi-e), SEQ ID NO: 2170; in (xxi-f), SEQ ID NO: 2180; in (xxii), SEQ ID NO: 2210; in (xxiii), SEQ ID NO: 2310; in (xxiv), SEQ ID NO: 2410; in (xxv), SEQ ID NO: 2510; in (xxvi), SEQ ID NO: 2610; in (xxvii), SEQ ID NO: 2710; in (xxviii). SEQ ID NO: 2810; in (xxviii-a), SEQ ID NO: 2830; in (xxviii-b), SEQ ID NO: 2840; in (xxviii-c), SEQ ID NO: 2850; in (xxviii-d), SEQ IDNO: 2860; in (xxviii-e), SEQ ID NO: 2870; in (xxviii-f), SEQ ID NO: 2880; in (xxix), SEQ ID NO: 2910; in (xxx), SEQ ID NO: 3010; in (xxxi), SEQ ID NO: 3110; in (xxxii), SEQ ID NO: 3210; in (xxxni), SEQ ID NO: 3310; in (xxxiv), SEQ ID NO: 3410; in (xxxv), SEQ ID NO: 3510; in (xxxvi), SEQ ID NO: 3610; in (xxxvii), SEQ ID NO: 3710; in (xxxviii), SEQ ID NO: 3810; in (xxxix), SEQ ID NO: 3910; in (xl), SEQ ID NO: 4010; in (xli), SEQ ID NO: 4110; in (xlii). SEQ ID NO: 4210; in (xliii), SEQ ID NO: 4310; in (xliv). SEQ ID NO: 4410; in (xlv), SEQ ID NO: 4510; in (xlvi). SEQ ID NO: 4610; in (xlvi-a), SEQ ID NO: 4630; in (xlvi-b), SEQ ID NO: 4640; in (xlvi-c), SEQ ID NO: 4650; in (xlvi-d), SEQ ID NO: 4660; in (xlvi-e), SEQ ID NO: 4670; in (xlvii), SEQ ID NO: 4710; in (xlviii). SEQ ID NO: 4810; in (xlix), SEQ ID NO: 4910; in (1), SEQ ID NO: 5010; in (li), SEQ ID NO: 5110; in (lii), SEQ ID NO: 5210; in (liii), SEQ ID NO: 5310; in (liv), SEQ ID NO: 5410; in (Iv), SEQ ID NO: 5510; in (Ivi), SEQ ID NO: 5610; in (Ivii), SEQ ID NO: 5710; in (Ivii-a), SEQ ID NO: 5730; in (Ivii-b), SEQ ID NO: 5740; in (Ivii-c), SEQ ID NO: 5750; in (Ivii-d), SEQ ID NO: 5760; in (Ivii-e), SEQ ID NO: 5770; in (Ivii-f), SEQ ID NO: 5780; in (Iviii), SEQ ID NO: 5810; in (lix). SEQ ID NO: 5910; in (lx). SEQ ID NO: 6010; in (Ixi), SEQ ID NO: 6110; in (Ixi-a), SEQ ID NO: 6130; in (Ixi-b), SEQ ID NO: 6140; in (Ixi-c), SEQ ID NO: 6150; in (Ixi-d), SEQ ID NO: 6160; in (Ixi-e), SEQ ID NO: 6170; in (Ixii), SEQ ID NO: 6210; in (Ixiii), SEQ ID NO: 6310; in (Ixiv), SEQ ID NO: 6410; in (Ixv). SEQ ID NO: 6510; in (Ixvi), SEQ ID NO: 6610; in (Ixvii), SEQ ID NO: 6710; in (Ixviii), SEQ ID NO: 6810; in (Ixviii-a), SEQ ID NO: 6830; in (Ixviii-b), SEQ ID NO: 6840; in (Ixviii-c), SEQ ID NO: 6850; in (Ixviii-d), SEQ ID NO: 6860; in (Ixviii-e), SEQ ID NO: 6870; in (Ixviii-f), SEQ ID NO: 6880; in (Ixix), SEQ ID NO: 6910; in (Ixx), SEQ ID NO: 7010; in (Ixx-a), SEQ ID NO: 7030; in (Ixx- b), SEQ ID NO: 7040; in (Ixx-c), SEQ ID NO: 7050; in (Ixx-d), SEQ ID NO: 7060; in (Ixx-e), SEQ ID NO: 7070; in (Ixx-f), SEQ ID NO: 7080; in (Ixxi), SEQ ID NO: 7110; in (Ixxii), SEQ ID NO: 7210; in (Ixxiii), SEQ ID NO: 7310; in (Ixxiv), SEQ ID NO: 7410; in (Ixxv), SEQ ID NO: 7510; in (Ixxvi), SEQ ID NO: 7610; in (Ixxvii), SEQ ID NO: 7710; in (Ixxvin), SEQ ID NO: 7810; or in (Ixxix), SEQ ID NO: 7910; in (Ixxx), SEQ ID NO: 8010; in (Ixxxi), SEQ ID NO: 8110; in (Ixxxii), SEQ ID NO: 8210; in (Ixxxiii), SEQ ID NO: 8310; in (Ixxxiii-a), SEQ ID NO: 8330; in (Ixxxiii-b), SEQ ID NO: 8340; in (Ixxxiii-c), SEQ ID NO: 8350; in (Ixxxiii-d), SEQ ID NO: 8360; in (Ixxxiii-e), SEQ ID NO: 8370; in (Ixxxiii-f), SEQ ID NO: 8380; or in (Ixxxiv), SEQ ID NO: 8410.

9. The anti-human CD28 antibody or antigen-binding antibody fragment of any one of claims 1-8. which comprises:(a) an immunoglobulin (Ig) format or a half-antibody variant thereof, optionally an IgG, IgA, IgE, IgD, or IgM format, further optionally an IgG1, IgG2, IgG3, or IgG4 format;(b) an antibody fragment antigen-binding region (Fab) format, a Fab’ format, a F(ab’)2 format, a F(ab’)v format, and / or a variable fragment (Fv) format,;(c) a single chain fragment variable region (scFv) format, a tandem scFv format, a diabody format, atriabody format, a tetrabody format, a scFv-Fc format, a scFv-CH format, a minibody format, a scFv-zipper format, a diabody-Fc format, a diabody- CH format, a half-antibody variant of any of the foregoing, and / or a single chain Fab (scFab) format;(d) a heavy chain-only antibody (HCAb) format, a nanobody -Fc format, a nanobody-CH format, a single chain nanobody-CH format, a camel Ig format, and / or an IgNAR format, or a single-chain variant of any of the foregoing; and / or(e) a single domain antibody (sdAb) format, a nanobody format, a tandem nanobody format.

10. The anti-human CD28 antibody or antigen-binding antibody fragment of any one of claims 1-9, which comprises: the VH-1 and the VL-1, wherein the anti-human CD28 antibody or antigen-binding antibody fragment comprises or consists of:(a) a heavy chain comprising the VH-1 and a light chain comprising the VL-1, optionally wherein the antibody or antigen-binding antibody fragment:(a-1) consists of said heavy and light chains;(a-2) comprises or consists of an Ig molecule comprising two said heavy chains and two said light chains, or a multimer of said Ig molecule; and / or(a-3) comprises or consists of an IgG, IgA, IgE, IgD, or IgM, optionally an IgG1, IgG2, IgG3, or IgG4; and / or(b) a Fab comprising the VH-1 and the VL-1, a Fab' comprising the VH-1 and the VL-1, a F(ab')2 comprising the VH-1 and the VL-1. aF(ab’)s comprising the VH-1 and the VL-1, and / or a Fv comprising the VH-1 and the VL-1; and / or(c) a scFv comprising the VH-1 and the VL-1, a tandem scFv comprising the VH-1 and the VL-1, a diabody comprising the VH-1 and the VL-1, a triabody comprising the VH-1 and the VL-1, a tetrabody comprising the VH-1 and the VL-1, a scFv-Fc comprising the VH-1 and the VL-1, a scFv-CH comprising the VH-1 and the VL-1, a minibody comprising the VH-1 and the VL-1, a scFv-zipper comprising the VH-1 and the VL-1, a diabody-Fc comprising the VH-1 and the VL-1, a diabody-CH comprising the VH-1 and the VL-1, and / or a scFab comprising the VH-1 and the VL-1; or the VH-1, wherein the anti-human CD28 antibody or antigen-binding antibody fragment comprises or consists of:(d) a HCAb comprising the VH-1, a nanobody-Fc comprising the VH-1, a nanobody - CH comprising the VH-1, a camel Ig comprising the VH-1, an IgNAR comprising the VH-1, and / or a single-chain variant of any of the foregoing; and / or(e) a sdAb comprising the VH-1; a nanobody comprising the VH-1; and / or a tandem nanobody comprising the VH-1.

11. The anti -human CD28 antibody or antigen-binding antibody fragment of any one of claims 1-10, which comprises one or more of the following features:(a) binds to mouse CD28 and / or cynomolgus CD28;(b) binds to human CD28 with a KD of < about 1 μM, < about 500 nM, < about 200 nM, < about 100 nM, < about 50 nM. < about 20 nM, < about 10 nM, < about 5 nM, < about 2 nM, < about 1 nM, < about 500 pM, about 1 μM, about 500 nM, about 200 nM, about 100 nM, about 50 nM, about 20 nM, about 10 nM, about 5 nM, about 2 nM, about 1 nM, about 500 pM, about 200 pM, between about 100 nM and 1 nM, between about 50 nM and 1 nM, between about 20 nM and 1 nM. between about 10 nM and 1 nM, between about 5 nM and 1 nM, between about 2 nM and 1 nM, between about 10 nM and 500 pM, between about 5 nM and 500 pM, between about 2 nM and 500 pM, between about InM and 500 pM, between about 1 nM and 200 pM, or between about 500 pM and about 200 pM, at a physiological pH or at pH 7.4,optionally as measured by bio-layer interferometry' (BLI), further optionally as performed in Example 3 and / or 12;(c) binds to human CD28 with a KD of < about 1 μM, < about 500 nM, < about 200 nM, < about 100 nM, < about 50 nM, < about 20 nM, < about 10 nM, < about 5 nM, < about 2 nM, < about 1 nM, about 1 μM, about 500 nM, about 200 nM, about 100 nM, about 50 nM, about 20 nM. about 10 nM, about 5 nM, about 2 nM, or about 1 nM, at an acidic pH or at pH 6.0, optionally as measured by BLI, further optionally as performed in Example 3;(d) binds to human CD28 with a lower KD at an acidic pH or at pH 6.0 compared to at a physiological pH or at pH 7.4, optionally by or at least by about 1.5-fold, about 2- fold, about 3-fold, about 4-fold, about 5-fold, about 6-fold, about 7-fold, about 8-fold, about 9-fold, about 10-fold, about 12-fold, about 15-fold, about 20-fold, about 25- fold, about 30-fold, about 35-fold, about 40-fold, about 45-fold, about 50-fold, about 60-fold, about 70-fold, about 80-fold, about 90-fold, about 100-fold, about 200-fold, about 300-fold, about 400-fold, about 500-fold, about 600-fold, about 700-fold, about 800-fold, about 900-fold, or about 1000-fold, optionally as measured by BLI, further optionally as performed in Example 3;(e) binds to human CD28 at an acidic pH or at pH 6.0 but does not bind to human CD28 at a physiological pH or at pH 7.

4. optionally as measured by BLI, further optionally as performed in Example 3;(1) does not bind to mouse or murine CD28 or binds to mouse or murine CD28 with a KD of > about 10 nM, > about 20 nM, > about 50 nM. > about 100 nM, > about 200 nM, > about 500 nM, > about 1 μM, about 10 nM, about 20 nM. about 50 nM, about 100 nM, about 200 nM, about 500 nM, or about 1 μM, optionally as measured by BLI, further optionally as performed in Example 3 and / or 12;(g) does not bind to human CD28 monomer or binds to human CD28 monomer with a KD of > about 1 nM, > about 10 nM, > about 20 nM, > about 50 nM, > about 100 nM, > about 200 nM, > about 500 nM, > about 1 μM, about 1 nM, about 10 nM, about 20 nM, about 50 nM, about 100 nM, about 200 nM, about 500 nM, or about 1 μM, optionally as measured by BLI, further optionally as performed in Example 3 and / or 12;(h) binds to human CD28 expression cells, optionally Jurkat cells and / or human CD28- CHO cells, more efficiently compared to one or more of CTL-77428 (TheraMab IgG Hu5.11 Defines Bin 1), CTL-77431 (OSE IgGHCD28.3 Defines Bin 2), CTL-77432 (Astellas IgG FK734), CTL-77435 (Sanofi IgG CD28sup), CTL-77436 (Roche IgG SA28_vl5), and / or CTL-77440 (Inhibrx HCAb INRX28), optionally as measured by flow cytometry, further optionally based on median fluorescence intensity and / or normalized cell binding values, yet further optionally as performed in Example 5 and / or 13;(i) displays a polyspecificity reagent (PSR) score of: score < 0.1 (clean); 0.10 < score < 0.33 (low), or 0.33 < score < 0.66 (medium), or 0.00 as measured by an PSR assay, optionally as performed in Example 6 and / or 14;(j) displays a hydrophobic interaction chromatography (HIC) retention time (RT) of: RT < 9.5 minutes, RT < 10.0 minutes, or RT < 10.5 minutes (clean or low), or 10.5 minutes < RT < 11.5 minutes (medium), as measured by HIC, optionally as performed in Example 6 and / or 14;(k) displays a melting temperature (Tm) of < about 45 °C, < about 50 °C, < about 55 °C, < about 60 °C, < about 65 °C, < about 70 °C, < about 75 °C, < about 80 °C, < about 85 °C, > about 45 °C, > about 50 °C, > about 55 °C, > about 60 °C. > about 65 °C, > about 70 °C, > about 75 °C, > about 80 °C, > about 85 °C. about 45 °C, about 50 °C, about 55 °C, about 60 °C, about 65 °C, about 70 °C, about 75 °C, about 80 °C, or about 85 °C, optionally as measured by differential scanning fluorimetry (DSF), further optionally as performed in Example 6 and / or 14; and / or(l) is capable of stimulating a T cell, as determined by at least one of:(1-1) increased expression of CD69, optionally as measured by flow cytometry, further optionally based on an increased mean fluorescence intensity (MFI), yet further optionally by about 5%, by about 10%, about 15%, by about 20%, about 25%, by about 30%, about 35%, by about 40%, about 45%, by about 50%, about 55%, by about 60%, about 65%, by about 70%, about 75%, by about 80%, about 85%, by about 90%, about 95%, by about 100%, by about 150%, by about 200%, by about 250%, by about 300%, by about 350%, by about 400%, by about 450%, or by 500%;(1-2) increased release of IL-2, optionally by or at least by about 1.5-fold, about 2- fold, about 3-fold, about 4-fold, about 5-fold, about 6-fold, about 7-fold, about 8-fold, about 9-fold, about 10-fold, about 12-fold, about 15-fold, about 20-fold, about 25- fold, about 30-fold, about 35-fold, about 40-fold, about 45-fold, or about 50-fold, optionally as measured by an immuno-assay, optionally Enzyme-linked immunosorbent assay (ELISA), optionally by about 5%, by about 10%. about 15%, by about 20%, about 25%. by about 30%, about 35%. by about 40%, about 45%. by about 50%, about 55%, by about 60%, about 65%, by about 70%, about 75%, by about 80%, about 85%, by about 90%, about 95%, by about 100%, by about 150%, by about 200%, by about 250%. by about 300%, by about 350%, by about 400%, by about 450%, or by 500%; or(1-3) increased transcriptional activation, optionally as measured using a CD28 Bioassay (Promega, TM633), upon incubation of a T cell with the anti-human CD28 antibody or antigen-binding antibody fragment and optionally with an anti-CD3 antibody. optionally compared to incubation of the T cell without the anti-human CD28 antibody or antigen-binding antibody fragment with or without an anti-CD3 antibody, further optionally as performed in Example 7.

12. A multi-specific antibody, comprising:(1) a first antigen-binding region (ABR-1) that binds human CD28, wherein the ABR-1 comprises the anti-human CD28 antibody or antigen-binding antibody fragment of any one of claims 1-11; and(2) a second antigen-binding region (ABR-2) that binds a second antigen, optionally wherein the ABR-2 comprises: a second heavy chain variable domain (VH-2) comprising a second heavy' chain complementarity determining region (CDR) 1 (CDRH1-2), a second heavy chain CDR2 (CDRH2-2), and a second heavy chain CDR3 (CDRH3-2); and / or a second light chain variable domain (VL-2) comprising a second light chain CDR1 (CDRL1-2), a second light chain CDR2 (CDRL2-2), and a second light chain CDR3 (CDRL3-2),wherein the second antigen is optionally the same as or different from human CD28, optionally wherein the multi-specific antibody is bispecific, trispecific, or tetraspecific.

13. The multi-specific antibody of claim 12, wherein the second antigen is or comprises:(a) human cluster of differentiation 3 (CD3);(b) a cancer antigen, optionally a tumor-specific antigen (TSA) or a tumor-associated antigen (TAA);(c) human CD28;(d) any one of the antigens selected from those listed in Table 3; and / or(c) any one of the cancer antigens, optionally any one of the TSAs or any one of the TAAs, selected from those listed in Table 3.

14. The multi-specific antibody of claim 12 or 13, wherein the second antigen is or comprises CD3.

15. The multi-specific antibody of claim 14, wherein the ABR-2 comprises the VH-2 and / or VL-2 and comprises a CDR amino acid sequence according to any one of those listed in Table 4B16. The multi-specific antibody of claim 14 or 15, wherein the ABR-2 comprises: said VH-2, wherein:(a) the amino acid sequence of the CDRH1-2 comprises or consists of: a heavy chain complementarity determining region 1 (CDRH1) amino acid sequence contained in any one of the heavy chain variable domain (VH) amino acid sequences listed in Table 4A; and / or any one of the CDRH1 amino acid sequences listed in Table 4B;(b) the amino acid sequence of the CDRH2-2 comprises or consists of: a heavy chain complementarity determining region 2 (CDRH2) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 4A; and / or any one of the CDRH2 amino acid sequences listed in Table 4B; and / or(c) the amino acid sequence of the CDRH3-2 comprises or consists of: a heavy chain complementarity determining region 3 (CDRH3) amino acid sequence contained inany one of the VH amino acid sequences listed in Table 4A; and / or any one of theCDRH3 amino acid sequences listed in Table 4B. and / or said VL-2, wherein:(d) the amino acid sequence of the CDRL1-2 comprises or consists of: a light chain complementarity determining region 1 (CDRL1) amino acid sequence contained in any one of the light chain variable domain (VL) amino acid sequences listed in Table 4A; and / or any one of the CDRL1 amino acid sequences listed in Table 4B;(c) the amino acid sequence of the CDRL2-2 comprises or consists of: a light chain complementarity determining region 2 (CDRL2) contained in any one of the VL amino acid sequences listed in Table 4A; and / or any one of the CDRL2 amino acid sequences listed in Table 4B; and / or(f) the amino acid sequence of the CDRL3-2 comprises or consists of: a light chain complementarity determining region 3 (CDRL3) that contained in any one of the VL amino acid sequences listed in Table 4A; and / or any one of the CDRL3 amino acid sequences listed in Table 4B.

17. The multi-specific antibody of any one of claims 14-16, wherein the ABR-2 comprises:(a) a set of heavy chain CDR amino acid sequences of a first anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E, optionally wherein the first anti-CD3 antibody is ADI-26906 or ADI-26921 ;(b) a set of light chain CDR amino acid sequences of a first anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E, optionally wherein the first anti-CD3 antibody is ADI-26906 or ADI-26921;(c) a set of heavy and light chain CDR amino acid sequences of a first anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E, optionally wherein the first anti-CD3 antibody is ADI-26906 or ADI-26921, further optionally wherein the ABR-1 comprises a set of heavy and light chain CDR amino acid sequences of any one of Ab Nos. 59-69 (yet further optionally Ab No. 61 or 68) and the ABR-2 comprises a set of heavy and light chain CDR amino acid sequences of ADI-26921; and / or(d) a set of heavy chain CDR amino acid sequences of a first anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E; and a set of light chain CDR amino acid sequences of a second anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E18. The multi-specific antibody of any one of claims 14-17, wherein the ABR-2 comprises the VH-2 and the VL-2, and wherein:(1) the amino acid sequences of the CDRH1-2, the CDRH2-2, and the CDRH3-2 in the VH-2 of the ABR-2 comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, and a CDRH3, respectively, contained in the VH of a first anti-CD3 antibody ; and(2) the amino acid sequences of the CDRL1-2, the CDRL2-2, and the CDRL3-2 in the VL-2 of the ABR-2 comprise or consist of the amino acid sequences of a CDRL1, a CDRL2, and a CDRL3, respectively , contained in the VL of said first anti-CD3 antibody , wherein said first anti-CD3 antibody is one selected from the antibodies listed in Tables 4A- 4E, optionally wherein the first anti-CD3 antibody is ADI-26906 or ADI-26921.

19. The multi-specific antibody of any one of claims 14-17, wherein the ABR-2 comprises the VH-2 and the VL-2, and wherein the amino acid sequences of the CDRH1-2, the CDRH2-2, the CDRH3-2, the CDRL1-2, the CDRL2-2, and the CDRL3-2 comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, a CDRH3, CDRLL a CDRL2, and a CDRL3 of a first anti-CD3 antibody, wherein said first anti-CD3 antibody is one selected from the antibodies listed in Tables 4A-4E, optionally wherein the first anti-CD3 antibody is ADI-26906 or ADI-26921.

20. The multi-specific antibody of any one of claims 14-18, wherein: the amino acid sequence of the VH-2 comprises or consists of an amino acid sequence selected from any one of the VH amino acid sequences listed in Table 4A or a variant thereof having at least about 80%, 85%, 90%, 91%. 92%. 93%. 94%. 95%, 96%, 97%, 98%, or 99% sequence identity; and / or the amino acid sequence of the VL-2 comprises or consists of an amino acid sequence selected from any one of the VL amino acid sequences listed in Table 4Aor a variant thereof having at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity.

21. The multi-specific antibody of claim 18 or 19, wherein the amino acid sequences of the VH-2 and the VL-2 have at least about 80%, at least about 85%, at least about 90%, at least about 91%. at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%. at least about 98%. or at least about 99% sequence identity to the amino acid sequences of the VH and the VL, respectively, of said first anti- CD3 antibody.

22. The multi-specific antibody of claim 14, wherein the ABR-2 comprises a variable domain pair according to any of those listed in Table 4A, optionally comprising the VH and the VL of ADI-26906 or ADI-26921, further optionally wherein the ABR-1 comprises a set of heavy and light chain CDR amino acid sequences of or a variable domain pair of any one of Ab Nos. 59-69 (yet further optionally Ab No. 61 or 68) and the ABR-2 comprises the variable domain pair of ADI-26921.

23. The multi-specific antibody of any one of claims 18, 19, or 21, wherein the amino acid sequences of the VH-2 and the VL-2 comprise or consist of the amino acid sequences of the VH and the VL, respectively, of said first anti-CD3 antibody.

24. The multi-specific antibody of any one of claims 12-23, wherein:(1) the ABR-1 comprises:(a) a heavy chain comprising the VH-1 and a light chain comprising the VL-1, optionally wherein the ABR-1 :(a- 1 ) consists of said heavy and light chains;(a-2) comprises or consists of an Ig molecule comprising two said heavy chains and two said light chains, or a multimer of said Ig molecule; and / or(a-3) comprises or consists of an IgG, IgA, IgE, IgD, or IgM, optionally an IgG1, IgG2. lgG3, or IgG4;(b) a Fab comprising the VH-1 and the VL-1, a Fab’ comprising the VH-1 and the VL-1, a F(ab’)2 comprising the VH-1 and the VL-1, a F(ab’)s comprising the VH-1 and the VL-1, and / or a Fv comprising the VH-1 and the VL-1;(c) a scFv comprising the VH-1 and the VL-1, a tandem scFv comprising the VH-1 and the VL-1, a diabody comprising the VH-1 and the VL-1, a triabody comprising the VH-1 and the VL-1, a tetrabody comprising the VH-1 and the VL-1, a scFv-Fc comprising the VH-1 and the VL-1, a scFv-CH comprising the VH-1 and the VL-1, a minibody comprising the VH-1 and the VL-1, a scFv-zipper comprising the VH-1 and the VL-1, a diabody-Fc comprising the VH-1 and the VL-1. a diabody-CH comprising the VH-1 and the VL-1; and / or a scFab comprising the VH-1 and the VL-1;(d) a HCAb comprising the VH-1, a nanobody-Fc comprising the VH-1, a nanobody- CH comprising the VH-1, a camel Ig comprising the VH-1, an IgNAR comprising the VH-1, and / or a single-chain variant of any of the foregoing; and / or(e) a sdAb comprising the VH-1, a nanobody comprising the VH-L and / or a tandem nanobody comprising the VH-1; and / or(2) the ABR-2 comprises:(a) a heavy chain comprising the VH-2 and a light chain comprising the VL-2, optionally wherein the ABR-2:(a-1) consists of said heavy and light chains;(a-2) comprises or consists of an Ig molecule comprising two said heavy chains and two said light chains, or a multimer of said Ig molecule; and / or(a-3) comprises or consists of an IgG, IgA, IgE, IgD, or IgM, optionally an IgG1, IgG2, IgG3, or IgG4;(b) a Fab comprising the VH-2 and the VL-2, a Fab' comprising the VH-2 and the VL-2, a F(ab')2 comprising the VH-2 and the VL-2. a F(ab’)s comprising the VH-2 and the VL-2, and / or a Fv comprising the VH-2 and the VL-2;(c) a scFv comprising the VH-2 and the VL-2, a tandem scFv comprising t the VH-2 and the VL-2, a diabody comprising the VH-2 and the VL-2, a triabody comprising the VH-2 and the VL-2, a tetrabody comprising the VH-2 and the VL-2, a scFv-Fc comprising the VH-2 and the VL-2, a scFv-CH comprising the VH-2 and the VL-2, a minibody comprising the VH-2 and the VL-2, a scFv-zipper comprising the VH-2 andthe VL-2. a diabody-Fc comprising the VH-2 and the VL-2, a diabody-CH comprising the VH-2 and the VL-2, and / or a scFab comprising the VH-2 and the VL-2;(d) a HCAb comprising the VH-2, a nanobody-Fc comprising the VH-2, a nanobody - CH comprising the VH-2, a camel Ig comprising the VH-2, an IgNAR comprising the VH-2, and / or a single-chain variant of any of the foregoing; and / or(e) a sdAb comprising the VH-2. a nanobody comprising the VH-2. and / or a tandem nanobody comprising the VH-2, optionally wherein the ABR-1 and the ABR-2 are associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds, and optionally wherein the multi-specific antibody comprises a structure depicted in any one of FIGS. 1-6, optionally any one of FIGS. 2-6, further optionally any one of FIGS. 2A-2M, 4A-4C, 5A-5N, and 6. yet further optionally the boxed structure of FIG.2G.

25. The multi-specific antibody of any one of claims 12-24, wherein:(1) the ABR-1 comprises: at least one Ig constant domain, optionally one or more of a heavy chain constant domain 1 (CH1), a heavy chain constant domain 2 (CH2), a heavy chain constant domain 3 (CH3), and / or a light chain constant domain (CL); and / or a fragment crystallizable (Fc) region, optionally wherein:(a) the CH1, CH2, and / or the CH3 is / are individually of an IgG, IgA, IgE, IgD, or IgM class, optionally of an IgG1, IgG2, IgG3, and / or IgG4 subclass;(b) the CL is of a kappa isotype (CLK) or a lambda isotype (CLk); and / or(c) the Fc region is of an IgG, IgA, IgE, IgD, or IgM class, optionally of an IgG1, IgG2, IgG3, and / or IgG4 subclass;(2) the ABR-2 comprises: at least one Ig constant domain, optionally one or more of a CH1, a CH2, a CH3, and / or a CL; and / or a Fc region, optionally wherein:(a) the CH1, CH2, and / or the CH3 is / are individually of an IgG, IgA, IgE, IgD, or IgM class, optionally of an IgG1, IgG2, IgG3, and / or IgG4 subclass;(b) the CL is a CLK or a CLk; and / or(c) the Fc region is of an IgG, IgA. IgE, IgD, or IgM class, optionally of an IgG1. IgG2. IgG3, and / or IgG4 subclass;(3) the multi-specific antibody comprises common light chains, and / or the VL-1 and the VL-2 have the same or essentially the same amino acid sequences, optionally wherein the second antigen is human CD3 and the amino acid sequences of the VL-1 and the VL-2 individually have at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity to the amino acid sequences of the VL of ADI-26921 (SEQ ID NO: 13270) or comprise or consist of SEQ ID NO: 13270; and / or(4) the multi-specific antibody comprises one or more of the following:(4-i) a heavy chain constant region (CH), optionally a CH1. which is engineered to promote pairing with a CLK over a CLZ. optionally wherein the CH1 engineering is one of those described in WO2021067404;(4-ii) a CH. optionally a CH1, which is engineered to promote pairing with a CLZ over a CLK, optionally wherein the CH1 engineering is one of those described in WO2021067404; and / or(4-iii) a CH, optionally a CH1, which is engineered to promote pairing with an engineered CL comprised in the multi-specific antibody over another CL. optionally wherein the combination of the CH engineering and the CL engineering is one of those described in WO2022150787; and / or(4-iv) at least two CHs having different amino acid sequences, optionally at least two CH3s having different amino acid sequences, which are engineered to promote heteromeric paring between the two CHs over homomeric pairing, optionally wherein the CH3 engineering is one of those described in WO2022150785.

26. The multi-specific antibody of any one of claims 12-25, comprising a third antigenbinding region (ABR-3) that binds to a third antigen, optionally wherein the ABR-3 comprises: a third heavy chain variable domain (VH-3) comprising a third heavy chain complementarity determining region (CDR) 1 (CDRH1-3), a third heavy chain CDR2 (CDRH2-3), and a third heavy chain CDR3 (CDRH3-3); and / ora third light chain variable domain (VL-3) comprising a third light chain CDR1 (CDRL1-3), a third light chain CDR2 (CDRL2-3), and a third light chain CDR3 (CDRL3-3), wherein the third antigen is optionally the same as or different from human CD28 and / or the second antigen.

27. The multi-specific antibody of claim 26, wherein the third antigen is or comprises:(a) human CD3;(b) a cancer antigen, optionally a TSA or a TAA;(c) human CD28;(d) any one of the antigens selected from those listed in Table 3; and / or(e) any one of the cancer antigens, optionally any one of the TSAs or any one of the TAAs, selected from those listed in Table 3.

28. The multi-specific antibody of claim 26 or 27, wherein the third antigen is or comprises CD329. The multi-specific antibody of claim 28, wherein the ABR-3 comprises the VH-3 and / or VL-3 and comprises a CDR amino acid sequence according to any one of those listed in Table 4B30. The multi-specific antibody of claim 28 or 29, wherein the ABR-3 comprises: said VH-3, wherein:(a) the amino acid sequence of the CDRH1-3 comprises or consists of: a heavy chain complementarity determining region 1 (CDRH1) amino acid sequence contained in any one of the heavy chain variable domain (VH) amino acid sequences listed in Table 4A; and / or any one of the CDRH1 amino acid sequences listed in Table 4B;(b) the amino acid sequence of the CDRH2-3 comprises or consists of: a heavy chain complementarity determining region 2 (CDRH2) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 4A; and / or any one of the CDRH2 amino acid sequences listed in Table 4B; and / or(c) the amino acid sequence of the CDRH3-3 comprises or consists of: a heavy chain complementarity determining region 3 (CDRH3) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 4A; and / or any one of the CDRH3 amino acid sequences listed in Table 4B, and / or said VL-3, wherein:(d) the amino acid sequence of the CDRL1-3 comprises or consists of: a light chain complementarity determining region 1 (CDRL1) amino acid sequence contained in any one of the light chain variable domain (VL) amino acid sequences listed in Table 4A; and / or any one of the CDRL1 amino acid sequences listed in Table 4B;(c) the amino acid sequence of the CDRL2-3 comprises or consists of: a light chain complementarity determining region 2 (CDRL2) contained in any one of the VL amino acid sequences listed in Table 4A; and / or any one of the CDRL2 amino acid sequences listed in Table 4B; and / or(f) the amino acid sequence of the CDRL3-3 comprises or consists of: a light chain complementarity determining region 3 (CDRL3) that contained in any one of the VL amino acid sequences listed in Table 4A; and / or any one of the CDRL3 amino acid sequences listed in Table 4B.

31. The multi-specific antibody of any one of claims 28-30, wherein the ABR-3 comprises:(a) a set of heavy chain CDR amino acid sequences of a third anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E, optionally wherein the third anti-CD3 antibody is ADI-26906 or ADI-26921;(b) a set of light chain CDR amino acid sequences of a third anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E, optionally wherein the third anti-CD3 antibody is ADI-26906 or ADI-26921;(c) a set of heavy and light chain CDR amino acid sequences of a third anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E, optionally wherein the third anti- CD3 antibody is ADI-26906 or ADI-26921, further optionally wherein the ABR-1 comprises a set of heavy and light chain CDR amino acid sequences of any one of Ab Nos. 59-69 (yet further optionally Ab No. 61 or 68) and the ABR-3 comprises a set of heavy and light chain CDR amino acid sequences of ADI-26921; and / or(d) a set of heavy chain CDR amino acid sequences of a third anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E; and a set of light chain CDR amino acid sequences of a fourth anti-CD3 antibody selected from the antibodies listed in Tables 4A- 4E.

32. The multi-specific antibody of any one of claims 28-31, wherein the ABR-3 comprises the VH-3 and the VL-3, and wherein:(1) the amino acid sequences of the CDRH1-3, the CDRH2-3, and the CDRH3-3 of the VH-3 of the ABR-3 comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, and a CDRH3, respectively, contained in the VH of a third anti-CD3 antibody; and(2) the amino acid sequences of the CDRL1-3, the CDRL2-3, and the CDRL3-3 of the VL-3 of the ABR-3 comprise or consist of the amino acid sequences of a CDRL1, a CDRL2, and a CDRL3, respectively , contained in the VL of said third anti-CD3 antibody, wherein said third anti-CD3 antibody is one selected from the antibodies listed in Tables 4A- 4E, optionally wherein the third anti-CD3 antibody is ADI-26906 or ADI-26921.

33. The multi-specific antibody of any one of claims 28-32, wherein the amino acid sequences of the CDRH1-3, the CDRH2-3, the CDRH3-3, the CDRL1-3, the CDRL2-3, and the CDRL3-3 of the VH-3 and the VL-3 of the ABR-3 comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, a CDRH3, CDRL1, a CDRL2, and a CDRL3 of a third anti-CD3 antibody, wherein said third anti-CD3 antibody is one selected from the antibodies listed in Tables 4A-4E, optionally wherein the third anti-CD3 antibody is ADI-26906 or ADI-26921.

34. The multi-specific antibody of any one of claims 29-33, wherein: the amino acid sequence of the VH-3 of the ABR-3 comprises or consists of an amino acid sequence selected from any one of the VH amino acid sequences listed in Table 4A or a variant thereof having at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity; and / or the amino acid sequence of the VL-3 of the ABR-3 comprises or consists of an amino acid sequence selected from any one of the VL amino acid sequences listedin Table 4A or a variant thereof having at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity.

35. The multi-specific antibody of claim 32 or 33, wherein the amino acid sequences of the VH-3 and the VL-3 of the ABR-3 have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%. at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to the ammo acid sequences of the VH and the VL, respectively, of said third anti-CD3 antibody.

36. The multi-specific antibody of any one of claims 28-35, wherein the ABR3 comprises a variable domain pair according to any of those listed in Table 4A, optionally comprising the VH and the VL of ADI-26906 or ADI-26921, further optionally wherein the ABR-1 comprises a set of heavy and light chain CDR amino acid sequences of any one of Ab Nos. 59-69 (yet further optionally Ab No. 61 or 68) and the ABR-3 comprises the variable domain pair of ADI-26921.

37. The multi-specific antibody of any one of claims 32, 33, or 35, wherein the amino acid sequences of the VH-3 and the VL-3 comprise or consist of the amino acid sequences of the VH and the VL, respectively, of said third anti-CD3 antibody.

38. The multi-specific antibody of any one of claims 26-37, wherein the ABR-3 comprises:(a) a heavy chain comprising said VH-3 and a light chain comprising said VL-3, optionally wherein the ABR-3 :(a-1) consists of said heavy and light chains;(a-2) comprises or consists of an Ig molecule comprising two said heavy chains and two said light chains, or a multimer of said Ig molecule; and / or(a-3) comprises or consists of an IgG, IgA, IgE, IgD, or IgM, optionally an IgG1 , IgG2, IgG3, or IgG4;(b) a Fab comprising the VH-3 and the VL-3, a Fab’ comprising the VH-3 and the VL-3, a F(ab’)2 comprising the VH-3 and the VL-3, a F(ab’)s comprising the VH-3 and the VL-3, and / or a Fv comprising the VH-3 and the VL-3;(c) a scFv comprising the VH-3 and the VL-3, a tandem scFv comprising the VH-3 and the VL-3, a diabody comprising the VH-3 and the VL-3, a triabody comprising the VH-3 and the VL-3, a tetrabody comprising the VH-3 and the VL-3, a scFv-Fc comprising the VH-3 and the VL-3, a scFv-CH comprising the VH-3 and the VL-3, a minibody comprising the VH-3 and the VL-3, a scFv-zipper comprising the VH-3 and the VL-3, a diabody-Fc comprising the VH-3 and the VL-3. a diabody-CH comprising the VH-3 and the VL-3, and / or a scFab comprising the VH-3 and the VL-3;(d) a HCAb comprising the VH-3, a nanobody-Fc comprising the VH-3, a nanobody - CH comprising the VH-3, a camel Ig comprising the VH-3, an IgNAR comprising the VH-3, and / or a single-chain variant of any of the foregoing; and / or(e) a sdAb comprising the VH-3, a nanobody comprising the VH-3, and / or a tandem nanobody comprising the VH-3, optionally wherein:(f) the ABR-1 and the ABR-2 are associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds;(g) the ABR-1 and the ABR-3 are associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds; and / or(h) the ABR-2 and the ABR-3 are associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds, and optionally wherein the multi-specific antibody comprises a structure depicted in any one of FIGS. 1-6, optionally any one of FIGS. 2-6, further optionally any one of FIGS. 3A-3B, 4A-4C, 5A-5N, and 6, yet further optionally the boxed structure of FIG.2G.

39. The multi-specific antibody of any one of claims 26-38, wherein:(1) the ABR-3 comprises: at least one Ig constant domain, optionally one or more of a CH1, a CH2, a CH3, and / or a CL; and / or a Fc region, optionally wherein:(a) the CH1, CH2, and / or the CH3 is / are individually of an IgG. IgA, IgE, IgD, or IgM class, optionally of an IgG1, IgG2, IgG3, and / or IgG4 subclass;(b) the CL is a CLK or a CLk; and / or(c) the Fc region is of an IgG, IgA, IgE, IgD, or IgM class, optionally of an IgG1, IgG2. IgG3, and / or IgG4 subclass;(2) the multi-specific antibody comprises common light chains and / or the VL-1 and the VL-2 have the same or essentially the same amino acid sequences and / or the VL-1 and the VL-3 have the same or essentially the same amino acid sequences and / or the VL-2 and the VL-3 have the same or essentially the same amino acid sequences, optionally wherein (i) the second antigen is human CD3 and the amino acid sequences of the VL-1 and the VL-2 individually have at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity to the amino acid sequences of the VL of ADI-26921 (SEQ ID NO: 13270) or compnse or consist of SEQ ID NO: 13270 and / or (ii) the third antigen is human CD3 and the amino acid sequences of the VL-1 and the VL-3 individually have at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity to the amino acid sequences of the VL of ADI- 26921 (SEQ ID NO: 13270) or compnse or consist of SEQ ID NO: 13270; and / or(3) the multi-specific antibody comprises one or more of the following:(3-i) a heavy chain constant region (CH), optionally a CH1, which is engineered to promote pairing with a CLK over a CLk, optionally wherein the CH1 engineering is one of those described in WO2021067404;(3-ii) a CH. optionally a CH1, which is engineered to promote pairing with a CLk over a CLK, optionally wherein the CH1 engineering is one of those described in WO2021067404; and / or(3-iii) a CH, optionally a CH1, which is engineered to promote pairing with an engineered CL comprised in the multi-specific antibody over another CL. optionally wherein the combination of the CH engineering and the CL engineering is one of those described in WO2022150787; and / or(3-iv) two CHs having different amino acid sequences, optionally two CH3s having different amino acid sequences, which are engineered to promote heteromeric paring between the twoCHs over homomeric pairing, optionally wherein the CH3 engineering is one of those described in WO2022150785.

40. The multi-specific antibody of any one of claims 12-39, comprising a fourth antigenbinding region (ABR-4) that binds to a fourth antigen, optionally wherein the ABR-4 comprises: a fourth heavy chain variable domain (VH-4) comprising a fourth heavy chain complementarity determining region (CDR) 1 (CDRH1-4), a fourth heavy chain CDR2 (CDRH2-4), and a fourth heavy chain CDR3 (CDRH3-4); and / or a fourth light chain variable domain (VL-4) comprising a fourth light chain CDR1 (CDRL1-4), a fourth light chain CDR2 (CDRL2-4). and a fourth light chain CDR3 (CDRL3-4), wherein the fourth antigen is optionally same as or different from human CD28, the second antigen, and / or the third antigen(s).

41. The multi-specific antibody of claim 40, wherein the fourth antigen comprises:(a) human cluster of differentiation 3 (CD3);(b) a cancer antigen, optionally a TSA or a TAA;(c) human CD28;(d) any one of the antigens selected from those listed in Table 3; and / or(e) any one of the cancer antigens, optionally any one of the TSAs or any one of the TAAs, selected from those listed in Table 3.

42. The multi-specific antibody of claim 40, wherein the fourth antigen is or comprises CD3.

43. The multi-specific antibody of claim 42, wherein the ABR-4 comprises the VH-4 and / or VL-4 and comprises a CDR amino acid sequence according to any one of those listed inTable 4B44. The multi-specific antibody of claim 42 or 43, wherein the ABR-4 comprises: said VH-4, wherein:(a) the amino acid sequence of the CDRH1-4 comprises or consists of: a heavy chain complementarity determining region 1 (CDRH1) amino acid sequence contained in any one of the heavy chain variable domain (VH) amino acid sequences listed in Table 4A; and / or any one of the CDRH1 amino acid sequences listed in Table 4B;(b) the amino acid sequence of the CDRH2-4 comprises or consists of: a heavy chain complementarity determining region 2 (CDRH2) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 4A; and / or any one of the CDRH2 amino acid sequences listed in Table 4B; and / or(c) the amino acid sequence of the CDRH3-4 comprises or consists of: a heavy chain complementarity determining region 3 (CDRH3) amino acid sequence contained in any one of the VH amino acid sequences listed in Table 4A; and / or any one of the CDRH3 amino acid sequences listed in Table 4B, and / or said VL-4, wherein:(d) the amino acid sequence of the CDRL1-4 comprises or consists of: a light chain complementarity determining region 1 (CDRL1) amino acid sequence contained in any one of the light chain variable domain (VL) amino acid sequences listed in Table 4A; and / or any one of the CDRL1 amino acid sequences listed in Table 4B;(c) the amino acid sequence of the CDRL2-4 comprises or consists of: a light chain complementarity determining region 2 (CDRL2) contained in any one of the VL amino acid sequences listed in Table 4A; and / or any one of the CDRL2 amino acid sequences listed in Table 4B; and / or(f) the amino acid sequence of the CDRL3-4 comprises or consists of: a light chain complementarity determining region 3 (CDRL3) that contained in any one of the VL amino acid sequences listed in Table 4A; and / or any one of the CDRL3 amino acid sequences listed in Table 4B.

45. The multi-specific antibody of any one of claims 42-44, wherein the ABR-4 comprises:(a) a set of heavy chain CDR amino acid sequences of a fifth anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E, optionally wherein the fifth anti-CD3 antibody is ADI-26906 or ADI-26921;(b) a set of light chain CDR amino acid sequences of a fifth anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E, optionally wherein the fifth anti-CD3 antibody is ADI-26906 or ADI-26921;(c) a set of heavy and light chain CDR amino acid sequences of a fifth anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E, optionally wherein the fifth anti- CD3 antibody is ADI-26906 or ADI-26921, further optionally wherein the ABR-1 comprises a set of heavy and light chain CDR amino acid sequences of any one of Ab Nos. 59-69 (yet further optionally Ab No. 61 or 68) and the ABR-4 comprises a set of heavy and light chain CDR amino acid sequences of ADI-26921; and / or(d) a set of heavy chain CDR amino acid sequences of a fifth anti-CD3 antibody selected from the antibodies listed in Tables 4A-4E; and a set of light chain CDR amino acid sequences of a sixth anti-CD3 antibody selected from the antibodies listed in Tables 4A- 4E.

46. The multi-specific antibody of claim 42-45. wherein the ABR-4 comprises the VH-4 and the VL-4, and wherein:(1) the amino acid sequences of the CDRH1-4, the CDRH2-4, and the CDRH3-4 of the VH-4 of the ABR-4 comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, and a CDRH3, respectively, contained in the VH of a fifth anti-CD3 antibody; and(2) the amino acid sequences of the CDRL1-4, the CDRL2-4, and the CDRL3-4 of the VL-4 of the ABR-4 comprise or consist of the amino acid sequences of a CDRL1, a CDRL2, and a CDRL3, respectively, contained in the VL of said fifth anti-CD3 antibody, wherein said fifth anti-CD3 antibody is one selected from the antibodies listed in Tables 4A- 4E, optionally wherein the fifth anti-CD3 antibody is ADI-26906 or ADI-26921.

47. The multi-specific antibody of claim 42-46, wherein the amino acid sequences of the CDRH1-4. the CDRH2-4, the CDRH3-4, the CDRL1-4, the CDRL2-4. and the CDRL3-4 of the VH-4 and VL-4 of the ABR-4 comprise or consist of the amino acid sequences of a CDRH1, a CDRH2, a CDRH3, CDRL1, a CDRL2, and a CDRL3 of a fifth anti-CD3 antibody, wherein said fifth anti-CD3 antibody is one selected from the antibodies listed in Tables 4A-4E48. The multi-specific antibody of any one of claims 43-47, wherein: the amino acid sequence of said VH-4 comprises or consists of an amino acid sequence selected from any one of the VH amino acid sequences listed in Table 4A or a variant thereof having at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity; and / or the amino acid sequence of said VL-4 comprises or consists of an amino acid sequence selected from any one of the VL amino acid sequences listed in Table 4A or a variant thereof having at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity.

49. The multi-specific antibody of claim 46 or 47, wherein the amino acid sequences of said VH-4 and the VL-4 have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least or at least about 99% sequence identity to the amino acid sequences of the VH and the VL. respectively, of said fifth anti-CD3 antibody.

50. The multi-specific antibody of claim 49, wherein the ABR-4 comprises a variable domain pair according to any of those listed in Table 4A, optionally comprising the VH and the VL of ADI-26906 or ADI-26921, further optionally wherein the ABR-1 comprises a set of heavy and light chain CDR amino acid sequences of any one of Ab Nos. 59-69 (yet further optionally Ab No. 61 or 68) and the ABR-4 comprises the variable domain pair of ADI- 26921.

51. The multi-specific antibody of any one of claims 46, 47, or 49. wherein the amino acid sequences of the VH-4 and the VL-4 comprise or consist of the amino acid sequences of the VH and the VL, respectively, of said fifth anti-CD3 antibody.

52. The multi-specific antibody of any one of claims 40-51, wherein said ABR-4 comprises:(a) a heavy chain comprising the VH-4 and a light chain comprising the VL-4, optionally wherein the ABR-4:(a-1) consists of said heavy and light chains;(a-2) comprises or consists of an Ig molecule comprising two said heavy chains and two said light chains, or a multimer of said Ig molecule: and / or(a-3) comprises or consists of an IgG, IgA, IgE, IgD, or IgM, optionally an IgG1, IgG2, IgG3, or IgG4;(b) a Fab comprising the VH-4 and the VL-4, a Fab' comprising the VH-4 and the VL-4, a F(ab')2 comprising the VH-4 and the VL-4. a F(ab’)s comprising the VH-4 and the VL-4, and / or a Fv comprising the VH-4 and the VL-4:(c) a scFv comprising the VH-4 and the VL-4, a tandem scFv comprising the VH-4 and the VL-4, a diabody comprising the VH-4 and the VL-4, a triabody comprising the VH-4 and the VL-4, a tetrabody comprising the VH-4 and the VL-4, a scFv-Fc comprising the VH-4 and the VL-4, a scFv-CH comprising the VH-4 and the VL-4, a minibody comprising the VH-4 and the VL-4, a scFv-zipper comprising the VH-4 and the VL-4, a diabody -Fc comprising the VH-4 and the VL-4, a diabody-CH comprising the VH-4 and the VL-4, and / or a scFab comprising the VH-4 and the VL-4;(d) a HCAb comprising the VH-4, a nanobody-Fc comprising the VH-4, a nanobody - CH comprising the VH-4, a camel Ig comprising the VH-4, an IgNAR comprising the VH-4, and / or a single-chain variant of any of the foregoing; and / or(e) a sdAb comprising the VH-4. a nanobody comprising the VH-4. and / or a tandem nanobody comprising the VH-4, optionally wherein:(f) the ABR-1 and the ABR-2 are associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds;(g) the ABR-1 and the ABR-3 are associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds;(h) the ABR-1 and the ABR-4 are associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds;(i) the ABR-2 and the ABR-3 are associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds:(j) the ABR-2 and the ABR-4 are associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds; and / or(k) the ABR-3 and the ABR-4 are associated with or linked to each other via a linker, optionally a peptide linker, further optionally a flexible peptide linker, or via one or more disulfide bonds, and further and optionally wherein the multi-specific antibody comprises a structure depicted in any one of FIGS. 1-6, optionally any one of FIGS. 4-6, further optionally any one of FIGS. 4A-4C, 5A-5N, and 6, yet further optionally the boxed structure of FIG. 2G.

53. The multi-specific antibody of any one of claims 40-52, wherein:(l) the ABR-4 comprises: at least one Ig constant domain, optionally one or more of a CH1, a CH2, a CH3, and / or a CL; and / or a Fc region, further optionally wherein:(a) the CH1, CH2, and / or the CH3 is / are individually of an IgG, IgA, IgE, IgD, or IgM class, optionally of an IgG1, IgG2, IgG3, and / or IgG4 subclass;(b) the CL is a CLK or a CL / .; and / or(c) the Fc region is of an IgG, IgA, IgE, IgD, or IgM class, optionally of an IgG1, IgG2, IgG3, and / or IgG4 subclass;(2) the multi-specific antibody comprises common light chains, and / or the VL-1 and the VL-2 have the same or essentially the same amino acid sequences, and / or the VL-1 and the VL-3 have the same or essentially the same amino acid sequences and / or the VL-1 and the VL-4 have the same or essentially the same amino acid sequences, and / or the VL- 2 and the VL-3 have the same or essentially the same amino acid sequences and / or the VL-2 and the VL-4 have the same or essentially the same amino acid sequences, and / or the VL-3 and the VL-4 have the same or essentially the same amino acid sequences, optionally wherein: (i) the second antigen is human CD3 and the amino acid sequences of the VL-1 and the VL-2 individually have at least about 80%, 85%, 90%, 91%, 92%, 93%,94%, 95%, 96%, 97%, 98%, or 99% sequence identity to the amino acid sequences of the VL of ADI-26921 (SEQ ID NO: 13270) or comprise or consist of SEQ ID NO: 13270;(ii) the third antigen is human CD3 and the amino acid sequences of the VL-1 and the VL-3 individually have at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity to the amino acid sequences of the VL of ADI- 26921 (SEQ ID NO: 13270) or comprise or consist of SEQ ID NO: 13270; and / or (iii) the fourth antigen is human CD3 and the amino acid sequences of the VL-1 and the VL-4 individually have at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity' to the amino acid sequences of the VL of ADI-26921 (SEQ ID NO: 13270) or comprise or consist of SEQ ID NO: 13270; and / or(3) the multi-specific antibody comprises one or more of the following:(3-i) a heavy chain constant region (CH), optionally a CH1, which is engineered to promote pairing with a CLK over a CLZ. optionally wherein the CH1 engineering is one of those described in WO2021067404;(3-ii) a CH, optionally a CH1, which is engineered to promote pairing with a CLZ over a CLK, optionally wherein the CH1 engineering is one of those described in WO2021067404; and / or(3 -iii) a CH, optionally a CH1. which is engineered to promote pairing with an engineered CL comprised in the multi-specific antibody over another CL, optionally wherein the combination of the CH engineering and the CL engineering is one of those described in WO2022150787; and / or(3-iv) two CHs having different amino acid sequences, optionally two CH3s having different amino acid sequences, which are engineered to promote heteromeric paring between the two CHs over homomeric pairing, optionally wherein the CH3 engineering is one of those described in WO2022150785.

54. A multi-specific antibody, optionally according to any one of claims 12-53, which comprises:(A) at least one antigen-binding region which binds to antigen A (ABR-A), comprising:(A-i) at least one heavy chain A which comprises a heavy chain variable domain A (VH-A) and a heavy chain constant region A (CH-A). optionally from the N-terminus to the C-terminus, optionally wherein the CH-A comprises:(a) a heavy chain constant domain 1 A (CH1 -A), a hinge (hinge-A), a heavy chain constant domain 2 A (CH2-A). and / or a heavy chain constant domain 3 A (CH3-A); and / or(b) a CH1 -A, a hinge-A, a CH2-A, and a CH3-A, optionally from the N- terminus to the C-terminus; and optionally(A-ii) at least one light chain A which comprises a light chain variable domain A (VL-A) and a light chain constant domain A (CL-A), wherein the heavy chain A and the light chain A (if present) are paired with each other, optionally via at least one disulfide bond; and(B) at least one antigen-binding region B (ABR-B) which comprises a Fab which binds to antigen B (Fab-B). comprising:(B-i) a heavy chain B which comprises a heavy chain variable domain B (VH-B) and a heavy chain constant region B (CH-B) comprising at least a heavy chain constant domain 1 B (CH1-B); and(B-ii) a light chain B which comprises a light chain variable domain B (VL-B) and a light chain constant domain B (CL-B), wherein the heavy chain B and the light chain B are paired with each other, optionally via at least one disulfide bond, to form an antigen-binding region which binds to the antigen B, optionally wherein:(a) the heavy chain B, optionally the C-terminus of or the N-terminus of the heavy chain B, is associated with or linked to:(a-1) the heavy chain A, optionally the N-terminus of or the C-terminus of the heavy chain A; or(a-2) the light chain A (if present), optionally the N-terminus of or the C-terminus of the light chain A (if present). optionally via a linker, further optionally a peptide linker, yet further optionally a flexible peptide linker; and / or(b) the light chain B, optionally the C-terminus of or the N-terminus of the light chain B, is associated with or linked to:(b-1) the light chain A (if present), optionally the N-terminus of or the C-terminus of the light chain A (if present); and / or(b-2) the heavy chain A, optionally the N-terminus of or the C-terminus of the heavy chain A, optionally via a linker, further optionally a peptide linker, yet further optionally a flexible peptide linker, further optionally wherein the multi-specific antibody comprises a structure depicted in any one of FIGS. 1-6, optionally according to any one of FIGS. 2A-21, 3A-3B, 4A-4C, and SA- 51, further optionally the boxed structure of FIG. 2G, and further optionally wherein the antigen B is the same as or different from antigen A.

55. A multi-specific antibody, optionally according to any one of claims 12-53. which comprises:(A) at least one antigen-binding region which binds to antigen A (ABR-A), comprising:(A-i) at least one heavy chain A which comprises a heavy chain variable domain A (VH-A) and a heavy chain constant region A (CH-A). optionally from the N-terminus to the C-terminus, optionally wherein the CH-A comprises:(a) a heavy chain constant domain 1 A (CH1 -A), a hinge (hinge-A), a heavy chain constant domain 2 A (CH2-A). and / or a heavy chain constant domain 3 A (CH3-A); and / or(b) a CH1 -A, a hinge-A, a CH2-A, and a CH3-A, optionally from the N- terminus to the C-terminus; and optionally(A-ii) at least one light chain A which comprises a light chain variable domain A (VL-A) and a light chain constant domain A (CL-A), wherein the heavy chain A and the light chain A (if present) are paired with each other, optionally via at least one disulfide bond, to form an antigen-binding region which binds to antigen A; and(B) at least one antigen-binding region B (ABR-B) which comprises a scFv which binds to antigen B (scFv-B), comprising:(B-i) a heavy chain variable domain B (VH-B); and(B-ii) a light chain variable domain B (VL-B), wherein:(a) the C-terminus of the VH-B is linked to the N-terminus of the VL-B, optionally wherein the scFv-B comprises the VH-B, a linker, and the VL-B from the N-terminus to the C-terminus; or(b) the C-terminus of the VL-B is linked to the N-terminus of the VH-B, optionally wherein the scFv-B comprises the VL-B, a linker, and the VH-B from the N-terminus to the C-terminus, optionally wherein the scFv-B, optionally the C-terminus of or the N-terminus of the scFv-B, is associated with or linked to:(1) the heavy chain A, optionally the N-terminus of or the C-terminus of the heavy chain A; and / or(2) the light chain A (if present), optionally the N-terminus of or the C-terminus of the light chain A (if present), optionally via a linker, further optionally a peptide linker, yet further optionally a flexible peptide linker; and / or further optionally wherein the multi-specific antibody comprises a structure depicted in any one of FIGS. 1-6, optionally according to any one of FIGS. 2A, 2F, 2J, 3A-3B, 4A-4C, 5C-5G, and 5J-5N,and optionally wherein the antigen B is the same as or different from antigen A.

56. A multi-specific antibody, optionally according to any one of claims 12-53. which comprises:(A) at least one antigen-binding region which binds to antigen A (ABR-A), comprising:(A-i) at least one heavy chain A which comprises a heavy chain variable domain A (VH-A) and a heavy chain constant region A (CH-A). optionally from the N-terminus to the C-terminus, optionally wherein the CH-A comprises:(a) a heavy chain constant domain 1 A (CH1 -A), a hinge (hinge-A), a heavy chain constant domain 2 A (CH2-A). and / or a heavy chain constant domain 3 A (CH3-A); and / or(b) a CH1 -A, a hinge-A, a CH2-A, and a CH3-A, optionally from the N- terminus to the C-terminus; and optionally(A-ii) at least one light chain A which comprises a light chain variable domain A (VL-A) and a light chain constant domain A (CL-A), wherein the heavy7chain A and the light chain A (if present) are paired with each other, optionally via at least one disulfide bond, to form an antigen-binding region which binds to antigen A; and(B) at least one antigen-binding region B (ABR-B) which comprises a scFab which binds to antigen B (scFab-B), comprising:(B-i) a heavy chain B which comprises a heavy7chain variable domain B (VH-B) and a heavy chain constant region B (CH-B) comprising at least a heavy chain constant domain 1 B (CH1-B); and(B-ii) a light chain B which comprises a light chain variable domain B (VL-B) and a light chain constant domain B (CL-B), wherein:(a) the C-terminus of the heavy chain B is linked to the N-terminus of the light chain B, optionally wherein the scFab-B comprises the heavy chain B, a linker, and the light chain B from the N-terminus to the C-terminus; or(b) the C-terminus of the light chain B is linked to the N-terminus of the heavy chain B, optionally wherein the scFab-B comprises the light chain B, a linker, and the heavy chain B from the N-terminus to the C-terminus, optionally wherein the scFab-B, optionally the C-terminus of or the N-terminus of the scFab- B, is associated with or linked to:(1) the heavy chain A, optionally the N-terminus of or the C-terminus of the heavy chain A; and / or(2) the light chain A (if present), optionally the N-terminus of or the C-terminus of the light chain A (if present), optionally via a linker, further optionally a peptide linker, yet further optionally a flexible peptide linker; and / or further optionally wherein the multi-specific antibody comprises a structure depicted in any one of FIGS. 1-6, optionally according to any one of FIGS. 2A, 2F, 2K, 3A-3B, and 4A-4C, and optionally wherein the antigen B is the same as or different from antigen A.

57. A multi-specific antibody, optionally according to any one of claims 12-53, which comprises:(A) at least one antigen-binding region which binds to antigen A (ABR-A). comprising:(A-i) at least one heavy chain A which comprises a heavy chain variable domain A (VH-A) and a heavy chain constant region A (CH-A), optionally from the N-terminus to the C-terminus, optionally wherein the CH-A comprises:(a) a heavy chain constant domain 1 A (CH1 -A), a hinge (hinge-A). a heavy chain constant domain 2 A (CH2-A), and / or a heavy chain constant domain 3 A (CH3-A); and / or(b) a CH1-A, a hinge-A, a CH2-A, and a CH3-A, optionally from the N- terminus to the C-terminus; and optionally(A-ii) at least one light chain A which comprises a light chain variable domain A (VL-A) and a light chain constant domain A (CL-A),wherein the heavy chain A and the light chain A are paired with each other, optionally via at least one disulfide bond, to form an antigen-binding region which binds to antigen A; and(B) at least one antigen-binding region B (ABR-B) which comprises a sdAb which binds to antigen B (sdAb-B), comprising a heavy chain variable domain B (VH-B), optionally wherein the sdAb, optionally the C-terminus of or the N-terminus of the sdAb-B, is associated with or linked to:(1) the heavy chain A, optionally the N-terminus of or the C-terminus of the heavy chain A; and / or(2) the light chain A (if present), optionally the N-terminus of or the C-terminus of the light chain A (if present), optionally via a linker, further optionally a peptide linker, yet further optionally a flexible peptide linker; and / or further optionally wherein the multi-specific antibody comprises a structure depicted in any one of FIGS. 1-6, optionally according to any one of FIGS. 2-6 which is further modified to omit at least one VL, and further optionally wherein the antigen B is the same as or different from antigen A.

58. A multi-specific antibody, optionally according to any one of claims 12-53, which comprises:(A) at least one antigen-binding region which binds to antigen A (ABR-A), comprising:(A-i) at least one heavy chain A which comprises a heavy chain variable domain A (VH-A) and a heavy chain constant region A (CH-A), optionally from the N-terminus to the C-terminus, optionally wherein the CH-A comprises:(a) a heavy chain constant domain 1 A (CH1 -A), a hinge A (hinge- A), a heavychain constant domain 2 A (CH2-A). and / or a heavy chain constant domain 3 A (CH3-A); and / or(b) a CH1 -A, a hinge- A, a CH2-A, and a CH3-A, optionally from the N- terminus to the C-terminus; and optionally(A-ii) at least one light chain A which comprises a light chain variable domain A (VL-A) and a light chain constant domain A (CL-A), wherein the heavy chain A and the light chain A (if present) are paired with each other, optionally via at least one disulfide bond, to form an antigen-binding region which binds to antigen A; and(B) at least one antigen-binding region which binds to antigen B (ABR-B), comprising:(B-i) at least one heavy chain B which comprises a heavy chain variable domain B (VH-B) and a heavy chain constant region B (CH-B), optionally from the N-terminus to the C-terminus, optionally wherein the CH-B comprises:(a) a heavy chain constant domain 1 B (CH1-B). a hinge B (hinge-B). a heavy’ chain constant domain 2 B (CH2-B), and / or a heavy chain constant domain 3 B (CH3-A); and / or(b) a CH1-B, a hinge-B, a CH2-B, and a CH3-B, optionally from the N- terminus to the C-terminus; and optionally(B-ii) at least one light chain B which comprises a light chain variable domain B (VL- B) and a light chain constant domain B (CL-B), wherein the heavy chain B and the light chain B (if present) are paired with each other, optionally via at least one disulfide bond, to form an antigen-binding region which binds to antigen B, optionally wherein the heavy chain A and the heavy chain B are paired with each other, optionally via at least one disulfide bond, further optionally wherein:(a) (a-1) the light chain A (if present) and the light chain B (if present) have the same or essentially the same amino acid sequences or are common light chains; or(a-2) (a-2i) the CH-A and / or the CL- A (if present), optionally the CH1 -A and / or the CL-A (if present), are engineered to promote pairing between the CH-A and the CL-A over between the CH-A and the CL-B and / or over between the CH-B and the CL-A, optionally wherein:(1) the CL- A is a CLK and the CH- A, optionally the CH1 -A, is engineered to promote pairing with a CLK over a C LX. optionally wherein the CH1-A engineering is one of those described in WO2021067404;(2) the CL-A is a CL / . and the CH- A, optionally the CH1 -A, is engineered to promote pairing with a CL / . over a CLK. optionally wherein the CH1-A engineering is one of those described in WO2021067404; or(3) both the CH- A, optionally the CH1 -A, and the CL-A are engineered to promote pairing between the CH-A and the CL-A over between the CH-A and the CL-B and / or between the CH-B and the CL-A, optionally wherein the combination of the CH-A engineering and the CL-A engineering is one of those described inWO2022150787; and / or(a-2ii) the CH-B and / or the CL-B (if present), optionally the CH1-B and / or the CL-B (if present), are engineered to promote pairing between the CH-B and the CL-B over between the CH-B and the CL-A and / or over between the CH-A and the CL-B, optionally wherein:(1) the CL-B is a CLA and the CH-B, optionally the CH1-B, is engineered to promote pairing with a CL / . over a CLK, optionally wherein the CH1-B engineering is one of those described in WO2021067404;(2) the CL-B is a CLK and the CH-B. optionally the CH1-B. is engineered to promote pairing with a CLK over a CL / .. optionally wherein the CH1-B engineering is one of those described in WO2021067404; or(3) both the CH-B, optionally the CH1-B, and the CL-B are engineered to promote pairing between the CH-B and the CL-B over between the CH-B and the CL-A and / or between the CH-A and the CL-B, optionally wherein the combination of the CH-B engineering and the CL-B engineering is one of those described in WO2022150787; and / or(b) the CH-A and / or the CH-B, optionally the CH3-A and / or the CH3-B and / or optionally the CH3-A and / or the CH3-B, are engineered to promote heteromeric paring between the CH-A and the CH-B over homomeric CH-A pairing and / or homomeric CH-B pairing, optionally wherein the CH3-A and / or CH3-B engineering is one of those described in WO2022150785, further optionally wherein the multi-specific antibody comprises a structure depicted in any one of FIGS. 1-6, optionally according to any one of FIGS. 2G-2K, 3A-3B, 4A-4C, and 5A- 5N, further optionally the boxed structure of FIG. 2G, and optionally wherein said antigen B is the same as or different from antigen A.

59. The multi-specific antibody of any one of claims 54-58, which is according to any one of claims 12-25, wherein:(I) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1; and(B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2; or(II) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2; and(B) the antigen B is human CD28. wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1.

60. The multi-specific antibody of any one of claims 54-58, which further comprises:(C) at least one antigen-binding region which binds to antigen C (ABR-C), comprising:(C-l) a Fab which binds to antigen C (Fab-C), comprising:(C-l-i) a heavy chain C which comprises a heavy chain variable domain C (VH- C) and a heavy chain constant region C (CH-C) comprising at least a heavy chain constant domain 1 C (CH1-C); and(C-ii) a light chain C which comprises a light chain variable domain C (VL-C) and a light chain constant domain C (CL-C),wherein the heavy chain C and the light chain C are paired with each other, optionally via at least one disulfide bond;(C-2) a scFv which binds to antigen C (scFv-C), comprising:(C-i) a heavy chain variable domain C (VH-C); and(C-ii) a light chain variable domain C (VL-C). wherein:(a) the C-terminus of the VH-C is linked to the N-terminus of the VL-C, optionally wherein the scFv-C comprises the VH-C, a linker, and the VL-C from the N-terminus to the C-terminus; or(b) the C-terminus of the VL-C is linked to the N-terminus of the VH-C, optionally wherein the scFv-C comprises the VL-C, a linker, and the VH-C from the N-terminus to the C-terminus;(C-3) a which binds to antigen C (scFab-C), comprising:(C-i) a heavy chain C which comprises a heavy chain variable domain C (VH-C) and a heavy chain constant region C (CH-C) comprising at least a heavy chain constant domain 1 C (CH1-C); and(C-ii) a light chain C which comprises a light chain variable domain C (VL-C) and a light chain constant domain C (CL-C), wherein:(a) the C-terminus of the heavy chain C is linked to the N-terminus of the light chain C, optionally wherein the scFab-C comprises the heavy chain C, a linker, and the light chain B from the N-terminus to the C-terminus; or(b) the C-terminus of the light chain C is linked to the N-terminus of the heavy chain C, optionally wherein the scFab-C comprises the light chain C, a linker, and the heavy chain C from the N-terminus to the C-terminus; or(C-4) at least one sdAb which binds to antigen C (sdFab-C), comprising a heavy chain variable domain C (VH-C),further optionally wherein the multi-specific antibody comprises a structure depicted in any one of FIGS. 1-6, optionally according to any one of FIGS. 2-6, optionally wherein the antigen C is the same as or different from antigen A and / or antigen B.

61. The multi-specific antibody of claim 60, wherein: in (C-l), the Fab-C is associated with or linked to the ABR-A and / or the ABR-B. optionally wherein:(a) the heavy chain C, optionally the C-terminus of or the N-terminus of the heavy chain C, is associated with or linked to the ABR-A and / or the ABR-B, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A and / or the C-terminus of and / or the N-terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, optionally via a linker; and / or(b) the light chain C. optionally the C-terminus of or the N-terminus of the light chain C, is associated with or linked to the ABR-A and / or the ABR-B, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A and / or the C-terminus of and / or the N- terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, optionally via a linker; in (C-2), the scFv-C, optionally the C-terminus of or the N-terminus of the scFv-C, is associated with or linked to the ABR-A and / or the ABR-B, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A and / or the C-terminus of and / or the N-terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, optionally via a linker; in (C-3), the scFab-C, optionally the C-terminus of or the N-terminus of the scFab-C, is associated with or linked to the ABR-A and / or the ABR-B, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A and / or the C-terminus of and / or the N-terminus of theheavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, optionally via a linker; or in (C-4), the sdFab-C, optionally the C-terminus of or the N-terminus of the sdAb-C, is associated with or linked to the ABR-A and / or the ABR-B, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A and / or the C-terminus of and / or the N-terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, optionally via a linker, optionally wherein the optional linker in (C-l), (C-2), (C-3), and / or (C-4) is a peptide linker, optionally a flexible peptide linker.

62. The multi-specific antibody of claim 60 or 61, which is one according to any one of claims 26-39, wherein:(I) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1;(B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2; and(C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3;(II) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1;(B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3; and(C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2;(III) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2;(B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1; and(C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3;(IV) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2;(B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3; and(C) the antigen C is human CD28, wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1;(V) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3;(B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1; and(C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2; or(VI) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3;(B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2; and(C) the antigen C is human CD28, wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1.

63. The multi-specific antibody of any one of claims 60-62, which further comprises:(D) at least one antigen-binding region which binds to antigen D (ABR-D), comprising:(D-l) a Fab which binds to antigen D (Fab-D), comprising:(D-l-i) a heavy chain D which comprises a heavy chain variable domain D (VH- D) and a heavy chain constant region D (CH-D) comprising at least a heavy chain constant domain 1 D (CH1-D); and(D-ii) a light chain D which comprises a light chain variable domain D (VL-D) and a light chain constant domain D (CL-D), wherein the heavy chain D and the light chain D are paired with each other, optionally via at least one disulfide bond;(D-2) a scFv which binds to antigen D (scFv-D), comprising:(D-i) a heavy chain variable domain D (VH-D); and(D-ii) a light chain variable domain D (VL-D), wherein:(a) the C-terminus of the VH-D is linked to the N-terminus of the VL-D. optionally wherein the scFv-D comprises the VH-D, a linker, and the VL-D from the N-terminus to the C-terminus; or(b) the C-terminus of the VL-D is linked to the N-terminus of the VH-D, optionally wherein the scFv-D comprises the VL-D. a linker, and the VH-D from the N-terminus to the C-terminus;(D-3) a scFab which binds to antigen D (scFab-D), comprising:(D-i) a heavy chain D which comprises a heavy chain variable domain D (VH-D) and a heavy chain constant region D (CH-D) comprising at least a heavy chain constant domain 1 D (CH1-D); and(D-ii) a light chain D which comprises a light chain variable domain D (VL-D) and a light chain constant domain D (CL-D), wherein:(a) the C-terminus of the heavy chain D is linked to the N-terminus of the light chain D, optionally wherein the scFab-D comprises the heavy chain D, a linker, and the light chain D from the N-terminus to the C-terminus; or(b) the C-terminus of the light chain D is linked to the N-terminus of the heavy chain D, optionally wherein the scFab-D comprises the light chain D, a linker, and the heavy chain D from the N-terminus to the C-terminus; or(D-4) a sdAb which binds to antigen D (sdFab-D), comprising a heavy chain variable domain D (VH-D). further optionally wherein the multi-specific antibody comprises a structure depicted in any one of FIGS. 1-6, optionally according to any one of FIGS. 2-6, optionally wherein the antigen D is the same as or different from antigen A, antigen B, and / or antigen C.

64. The multi-specific antibody of claim 63, wherein: in (D-l), the Fab-D is associated with or linked to the ABR-A, the ABR-B, and / or the ABR-C, optionally wherein:(a) the heavy chain D, optionally the C-terminus of or the N-terminus of the heavy chain D, is associated with or linked to the ABR-A, the ABR-B, and / or the ABR-C, optionally associated w ith or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A. the C-terminus of and / or the N-terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, and / or the C-terminus of and / or the N-terminus of the heavy chain C (if present) and / or the light chain C (if present), the scFv-C (if present), the scFab-C (if present), or the sdAb-C (if present) of the ABR-C, optionally via a linker; and / or(a) the light chain D, optionally the C-terminus of or the N-terminus of the light chain C, is associated with or linked to the ABR-A, the ABR-B, and / or the ABR-C, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A. the C-terminus of and / or the N-terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, and / or the C-terminus of and / or the N-terminus of the heavy chain C (if present) and / or the light chain C (if present), the scFv-C (if present), the scFab-C (if present), or the sdAb-C (if present) of the ABR-C, optionally via a linker; in (D-2), the scFv-D, optionally the C-terminus of or the N-terminus of the scFv-D, is associated with or linked to the ABR-A, the ABR-B, and / or the ABR-C, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain Aand / or the light chain A (if present) of the ABR-A, the C-terminus of and / or the N- terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, and / or the C-terminus of and / or the N-terminus of the heavy chain C (if present) and / or the light chain C (if present), the scFv-C (if present), the scFab-C (if present), or the sdAb-C (if present) of the ABR-C, optionally via a linker; in (D-3), the scFab-D, optionally the C-terminus of or the N-terminus of the scFab-D, is associated with or linked to the ABR-A, the ABR-B, and / or the ABR-C, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A, the C-terminus of and / or the N- terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, and / or the C-terminus of and / or the N-terminus of the heavy chain C (if present) and / or the light chain C (if present), the scFv-C (if present), the scFab-C (if present), or the sdAb-C (if present) of the ABR-C, optionally via a linker; or in (D-4), the sdFab-D, optionally the C-terminus of or the N-terminus of the sdAb-D, is associated with or linked to the ABR-A, the ABR-B, and / or the ABR-C, optionally associated with or linked to the C-terminus of and / or the N-terminus of the heavy chain A and / or the light chain A (if present) of the ABR-A, the C-terminus of and / or the N- terminus of the heavy chain B (if present) and / or the light chain B (if present), the scFv-B (if present), the scFab-B (if present), or the sdAb-B (if present) of the ABR-B, and / or the C-terminus of and / or the N-terminus of the heavy chain C (if present) and / or the light chain C (if present), the scFv-C (if present), the scFab-C (if present), or the sdAb-C (if present) of the ABR-C, optionally via a linker, optionally wherein the optional linker in (D-l), (D-2), (D-3), and / or (D-4) is a peptide linker, optionally a flexible peptide linker.

65. The multi-specific antibody of claim 63 or 64. which is one according to any one of claims 40-53, wherein:(I) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1;(B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2;(C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3; and(D) the antigen D is the fourth antigen, wherein the VH-D is or comprises the VH-4 and / or the VL-D (if present) is or comprises the VL-4;(II) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1;(B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2;(C) the antigen C is the fourth antigen, wherein the VH-C is or comprises the VH-4 and / or the VL-C (if present) is or comprises the VL-4; and(D) the antigen D is the third antigen, wherein the VH-D is or comprises the VH-3 and / or the VL-D (if present) is or comprises the VL-3;(III) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1;(B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3;(C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2; and(D) the antigen D is the fourth antigen, wherein the VH-D is or comprises the VH-4 and / or the VL-D (if present) is or comprises the VL-4;(IV) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1;(B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3;(C) the antigen C is the fourth antigen, wherein the VH-C is or comprises the VH-4 and / or the VL-C (if present) is or comprises the VL-4; and(D) the antigen D is the second antigen, wherein the VH-D is or comprises the VH-2 and / or the VL-D (if present) is or comprises the VL-2;(V) (A) the antigen A is human CD28. wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1;(B) the antigen B is the fourth antigen, wherein the VH-B is or comprises the VH-4 and / or the VL-B (if present) is or comprises the VL-4;(C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2; and(D) the antigen D is the third antigen, wherein the VH-D is or comprises the VH-3 and / or the VL-D (if present) is or comprises the VL-3;(VI) (A) the antigen A is human CD28, wherein the VH-A is or comprises the VH-1 and / or the VL-A (if present) is or comprises the VL-1;(B) the antigen B is the fourth antigen, wherein the VH-B is or comprises the VH-4 and / or the VL-B (if present) is or comprises the VL-4;(C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3; and(D) the antigen D is the second antigen, wherein the VH-D is or comprises the VH-2 and / or the VL-D (if present) is or comprises the VL-2;(VII) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH- 2 and / or the VL-A (if present) is or comprises the VL-2;(B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1;(C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3; and(D) the antigen D is the fourth antigen, wherein the VH-D is or comprises the VH-4 and / or the VL-D (if present) is or comprises the VL-4;(VIII) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH- 2 and / or the VL-A (if present) is or comprises the VL-2;(B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1;(C) the antigen C is the fourth antigen, wherein the VH-C is or comprises the VH-4 and / or the VL-C (if present) is or comprises the VL-4; and(D) the antigen D is the third antigen, wherein the VH-D is or comprises the VH-3 and / or the VL-D (if present) is or comprises the VL-3;(IX) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2;(B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3;(C) the antigen C is human CD28, wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1; and(D) the antigen D is the fourth antigen, wherein the VH-D is or comprises the VH-4 and / or the VL-D (if present) is or comprises the VL-4;(X) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2;(B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3;(C) the antigen C is the fourth antigen, wherein the VH-C is or comprises the VH-4 and / or the VL-C (if present) is or comprises the VL-4; and(D) the antigen D is human CD28. wherein the VH-D is or comprises the VH-1 and / or the VL-D (if present) is or comprises the VL-1;(XI) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH-2 and / or the VL-A (if present) is or comprises the VL-2;(B) the antigen B is the fourth antigen, wherein the VH-B is or comprises the VH-4 and / or the VL-B (if present) is or comprises the VL-4;(C) the antigen C is human CD28, wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1; and(D) the antigen D is the third antigen, wherein the VH-D is or comprises the VH-3 and / or the VL-D (if present) is or comprises the VL-3;(XII) (A) the antigen A is the second antigen, wherein the VH-A is or comprises the VH- 2 and / or the VL-A (if present) is or comprises the VL-2;(B) the antigen B is the fourth antigen, wherein the VH-B is or comprises the VH-4 and / or the VL-B (if present) is or comprises the VL-4;(C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3; and(D) the antigen D is human CD28, wherein the VH-D is or comprises the VH-1 and / or the VL-D (if present) is or comprises the VL-1;(XIII) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3;(B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1;(C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2; and(D) the antigen D is the fourth antigen, wherein the VH-D is or comprises the VH-4 and / or the VL-D (if present) is or comprises the VL-4;(XIV) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3;(B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1;(C) the antigen C is the fourth antigen, wherein the VH-C is or comprises the VH-4 and / or the VL-C (if present) is or comprises the VL-4; and(D) the antigen D is the second antigen, wherein the VH-D is or comprises the VH-2 and / or the VL-D (if present) is or comprises the VL-2;(XV) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3;(B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2;(C) the antigen C is human CD28, wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1; and(D) the antigen D is the fourth antigen, wherein the VH-D is or comprises the VH-4 and / or the VL-D (if present) is or comprises the VL-4;(XVI) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3;(B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2;(C) the antigen C is the fourth antigen, wherein the VH-C is or comprises the VH-4 and / or the VL-C (if present) is or comprises the VL-4; and(D) the antigen D is human CD28. wherein the VH-D is or comprises the VH-1 and / or the VL-D (if present) is or comprises the VL-1;(XVII) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH-3 and / or the VL-A (if present) is or comprises the VL-3;(B) the antigen B is the fourth antigen, wherein the VH-B is or comprises the VH-4 and / or the VL-B (if present) is or comprises the VL-4;(C) the antigen C is human CD28, wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1; and(D) the antigen D is the second antigen, wherein the VH-D is or comprises the VH-2 and / or the VL-D (if present) is or comprises the VL-2;(XVIII) (A) the antigen A is the third antigen, wherein the VH-A is or comprises the VH- 3 and / or the VL-A (if present) is or comprises the VL-3;(B) the antigen B is the fourth antigen, wherein the VH-B is or comprises the VH-4 and / or the VL-B (if present) is or comprises the VL-4;(C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2; and(D) the antigen D is human CD28, wherein the VH-D is or comprises the VH-1 and / or the VL-D (if present) is or comprises the VL-1;(IXX) (A) the antigen A is the fourth antigen, wherein the VH-A is or comprises the VH- 4 and / or the VL-A (if present) is or comprises the VL-4;(B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1;(C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2; and(D) the antigen D is the third antigen, wherein the VH-D is or comprises the VH-3 and / or the VL-D (if present) is or comprises the VL-3;(XX) (A) the antigen A is the fourth antigen, wherein the VH-A is or comprises the VH-4 and / or the VL-A (if present) is or comprises the VL-4;(B) the antigen B is human CD28, wherein the VH-B is or comprises the VH-1 and / or the VL-B (if present) is or comprises the VL-1;(C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3; and(D) the antigen D is the second antigen, wherein the VH-D is or comprises the VH-2 and / or the VL-D (if present) is or comprises the VL-2;(XXI) (A) the antigen A is the fourth antigen, wherein the VH-A is or comprises the VH- 4 and / or the VL-A (if present) is or comprises the VL-4;(B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2;(C) the antigen C is human CD28, wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1; and(D) the antigen D is the third antigen, wherein the VH-D is or comprises the VH-3 and / or the VL-D (if present) is or comprises the VL-3;(XXII) (A) the antigen A is the fourth antigen, wherein the VH-A is or comprises the VH- 4 and / or the VL-A (if present) is or comprises the VL-4;(B) the antigen B is the second antigen, wherein the VH-B is or comprises the VH-2 and / or the VL-B (if present) is or comprises the VL-2;(C) the antigen C is the third antigen, wherein the VH-C is or comprises the VH-3 and / or the VL-C (if present) is or comprises the VL-3; and(D) the antigen D is human CD28. wherein the VH-D is or comprises the VH-1 and / or the VL-D (if present) is or comprises the VL-1;(XXIII) (A) the antigen A is the fourth antigen, wherein the VH-A is or comprises the VH-4 and / or the VL-A (if present) is or comprises the VL-4;(B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3;(C) the antigen C is human CD28, wherein the VH-C is or comprises the VH-1 and / or the VL-C (if present) is or comprises the VL-1; and(D) the antigen D is the second antigen, wherein the VH-D is or comprises the VH-2 and / or the VL-D (if present) is or comprises the VL-2; or(XXIV) (A) the antigen A is the fourth antigen, wherein the VH-A is or comprises the VH-4 and / or the VL-A (if present) is or comprises the VL-4;(B) the antigen B is the third antigen, wherein the VH-B is or comprises the VH-3 and / or the VL-B (if present) is or comprises the VL-3;(C) the antigen C is the second antigen, wherein the VH-C is or comprises the VH-2 and / or the VL-C (if present) is or comprises the VL-2; and(D) the antigen D is human CD28, wherein the VH-D is or comprises the VH-1 and / or the VL-D (if present) is or comprises the VL-1.

66. The multi-specific antibody of any one of claims 12-65, which comprises a structure depicted in:(I) any one of FIGS. 2C (left top), 2F, 2G (boxed), 2J (boxed), 2K (boxed), 2J, and / or 2M, optionally wherein the antigen A and the antigen B are CD28 and CD3, respectively, or CD3 and CD28, respectively;(II) any one of FIGS. 3A-3B, optionally wherein:(a) the antigen A and the antigen B are CD28 and CD3, respectively, or CD3 and CD28, respectively;(b) the antigen A and the antigen C are CD28 and CD3, respectively, or CD3 and CD28, respectively; or(c) the antigen B and the antigen C are CD28 and CD3, respectively, or CD3 and CD28, respectively;(III) any one of FIGS.4A-4C. 5A (boxed), 5C-5F, 5H (top left), 51 (top left), and / or 5J- 5M, optionally wherein:(a) the antigen A and the antigen B are CD28 and CD3, respectively, or CD3 and CD28, respectively;(b) the antigen A and the antigen C are CD28 and CD3. respectively, or CD3 and CD28, respectively;(c) the antigen A and the antigen D are CD28 and CD3, respectively, or CD3 and CD28, respectively;(d) the antigen B and the antigen C are CD28 and CD3, respectively, or CD3 and CD28, respectively;(e) the antigen B and the antigen D are CD28 and CD3, respectively, or CD3 and CD28, respectively; or(f) the antigen C and the antigen D are CD28 and CD3, respectively, or CD3 and CD28, respectively.

67. The multi-specific antibody of any one of claims 12-66, which binds monovalently, bivalently, trivalently, or tetravalently to:(a) human cluster of differentiation 3 (CD3);(b) a cancer antigen, optionally a TSA or a TAA;(c) human CD28;(d) any one of the antigens selected from those listed in Table 3; and / or.(e) any one of the cancer antigens, optionally any one of the TSAs or any one of the TAAs, selected from those listed in Table 3.

68. The multi-specific antibody of claim 67, which binds bivalently to CD3.

69. A nucleic acid encoding the anti-human CD28 antibody or antigen-binding antibody fragment of any one of claims 1-11 or the multi-specific antibody of any one of claims 12- 68 or a portion thereof, optionally comprising: a VH-1 -encoding nucleic acid having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%. or 100% identity to any one of the VH-encoding sequences of Table 2A and / or 13A, optionally the VH-encoding sequences of SEQ ID NO:

119. 2119, 2819, 4619, 5719, 6119, 6819, 7019, or 8319; and / ora VL-1 -encoding nucleic acid having at least about 80%, at least about 85%, at least about 90%. at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identity to any one of the VL-encoding sequences of Table 2A and / or 13A, optionally the VL-encoding sequences of SEQ ID NO: 129, 2129, 2829, 4629. 5729, 6129, or 6829, further optionally comprising a VH- 1 -encoding nucleic acid and a VL-1 -encoding nucleic acid comprising SEQ ID NOS: 119 and 129, respectively, SEQ ID NOS: 2119 and 2129, respectively, SEQ ID NOS: 2819 and 2829, respectively, SEQ ID NOS: 4619 and 4629, respectively, SEQ ID NOS: 5719 and 5729, respectively, SEQ ID NOS: 6119 and 6129, respectively, or SEQ ID NOS: 6819 and 6829, respectively, or comprising a VH-l-encoding nucleic acid comprising SEQ ID NO: 7019 or 8319.

70. A vector comprising the nucleic acid of claim 69, optionally wherein:(i) the vector is an expression vector; and / or(ii) the vector comprises a plasmid, a viral vector (optionally adenoviral, lentiviral, or retroviral), a lipid-based vector, a self-replicating RNA vector, a virus-like particle, a polymer-based vector, and / or a nanoparticle, optionally a lipid-based nanoparticle.

71. An isolated, recombinant, and / or host cell comprising the nucleic acid of claim 69 or the vector of claim 70, optionally wherein the isolated, recombinant, and / or host cell is:(i) non-mammalian, optionally bacterial, yeast, fungal, protozoa, plant, or insect, bacterial; or(ii) mammalian, optionally human, non-human primate, monkey, rabbit, rodent, hamster, rat, or mouse.

72. A composition comprising at least one excipient and at least one of: the anti-human CD28 antibody or antigen-binding antibody fragment of any one of claims 1-11 or the multi-specific antibody of any one of claims 12-68; the nucleic acid of claim 69; the vector of claim 70; andthe isolated, recombinant, and / or host cell of claim 71.

73. A method of treating a disease, disorder, or condition in a subject, the method comprising administering to the subject an effective amount of at least one of: the anti-human CD28 antibody or antigen-binding antibody fragment of any one of claims 1-11 or the multi-specific antibody of any one of claims 12-68; the nucleic acid of claim 69; the vector of claim 70; the isolated, recombinant, and / or host cell of claim 71; and / or the composition of claim 72. optionally wherein:(a) the subject is(i) a mammal, optionally a human, a non-human primate, a monkey, a horse, a cow, sheep, a goat, a pig, a dog, a cat, a rabbit, a rodent, a hamster, a rat, or a mouse; or(ii) a non-mammalian vertebrate, optionally a bird, fish, an amphibian, or a reptile; and / or(b) the method further comprises administering to the subject an additional agent, optionally an adjuvant or a therapeutic agent.

74. The method of claim 73, wherein the disease, disorder, or a condition comprises cancer or a neoplastic condition, an autoimmune disease, a neurodegenerative disease, an infectious disease, an inflammatory disease, or another disease, optionally wherein:(i) the cancer is:(i-1) a solid cancer, optionally chosen from: one or more of mesothelioma, malignant pleural mesothelioma, non-small cell lung cancer, small cell lung cancer, squamous cell lung cancer, large cell lung cancer, pancreatic cancer, pancreatic ductal adenocarcinoma, esophageal adenocarcinoma, breast cancer, glioblastoma, ovarian cancer, colorectal cancer, prostate cancer, cervical cancer, skin cancer, melanoma, renal cancer, liver cancer, brain cancer, thymoma, sarcoma, carcinoma, uterine cancer, kidney cancer, gastrointestinal cancer, urothelial cancer, phary nx cancer,head and neck cancer, rectal cancer, esophagus cancer, or bladder cancer, or a metastasis thereof; and / or(i-2) a liquid cancer, optionally chosen from: chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL), multiple myeloma, acute lymphoid leukemia (ALL), Hodgkin lymphoma, B-cell acute lymphoid leukemia (BALL), T-cell acute lymphoid leukemia (TALL), small lymphocytic leukemia (SLL), B cell prolymphocytic leukemia, blastic plasmacytoid dendritic cell neoplasm, Burkitt's lymphoma, diffuse large B cell lymphoma (DLBCL), DLBCL associated with chronic inflammation, chronic myeloid leukemia, myeloproliferative neoplasms, follicular lymphoma, pediatric follicular lymphoma, hairy cell leukemia, small cell- or a large cell-follicular lymphoma, malignant lymphoproliferative conditions, MALT lymphoma (extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue), Marginal zone lymphoma, myelodysplasia, myelodysplastic syndrome, non-Hodgkin ly mphoma, plasmablastic lymphoma, plasmacytoid dendritic cell neoplasm, Waldenstrom macroglobulinemia, splenic marginal zone lymphoma, splenic lymphoma / leukemia, splenic diffuse red pulp small B-cell lymphoma, hairy cell leukemia-variant, lymphoplasmacytic lymphoma, a heavy chain disease, plasma cell myeloma, solitary' plasmacytoma of bone, extraosseous plasmacytoma, nodal marginal zone lymphoma, pediatric nodal marginal zone lymphoma, primary cutaneous follicle center lymphoma, lymphomatoid granulomatosis, primary mediastinal (thymic) large B-cell lymphoma, intravascular large B-cell lymphoma, ALK+large B-cell lymphoma, large B-cell lymphoma arising in HHV8-associated multicentric Castleman disease, primary' effusion lymphoma. B-cell lymphoma, acute myeloid leukemia (AML), or unclassifiable lymphoma;(ii) the autoimmune or inflammatory' disease is psoriasis, rheumatoid arthritis, autoimmune arthritis, ty pe I diabetes, systemic lupus ery thematosus, myasthenia gravis, multiple sclerosis, scleroderma, inflammatory bowel disease, Crohn’s disease, ulcerative colitis. Guillain-Barre syndrome, chronic inflammatory demyelinating polyneuropathy, pemphigus vulgaris, Sjogren’s syndrome, Addison’s disease, Behcet’s disease, Schmidt syndrome, celiac disease, dermatomyositis, autoimmune vitiligo, Graves’ disease, Hashimoto thyroiditis, Kawasaki disease, pernicious anemia, autoimmune vasculitis, or fibrosis;(iii) the neurodegenerative disease is Alzheimer’s disease, Huntington’s disease, Parkinson’s disease, amyotrophic lateral sclerosis. Friedreich ataxia, Lewy body disease, spinal muscular atrophy, motor neuron disease, multiple sclerosis. Batten disease, Creutzfeldt-Jakob disease;(iv) the infectious disease is a viral, bacterial, fungal, yeast, protozoan, prion or parasitic disease, optionally wherein (1) the viral disease is human immunodeficiency virus (HIV), hepatitis virus (optionally hepatitis A, B. or C virus), human papillomavirus (HPV), herpes simplex virus (HSV) (optionally HSV-1 orHSV-2), enterovirus, human cytomegalovirus, adenovirus, rhinovirus, Pox virus, Influenza virus, coronavirus (optionally MERS-CoV, SARS-CoV, or SARS-CoV-2, or common human coronavirus), norovirus, West Nile Virus, Zika virus, poliovirus, Ebola virus, or dengue virus (DENV) infection, (2) the bacterial disease is Salmonella, Escherichia coli. Mycobacterium tuberculosis, methicillin-resistant staphylococcus aureus (MRSA), Clostridium difficile, Streptococcus pneumoniae, Klebsiella pneumoniae, Pseudomonas aeruginosa, Helicobacter pylori, Neisseria gonorrhoeae. Vibrio vulnificus, and / or (3) the fungal disease is Aspergillosis, Candida. Candida auris. Cryptococcus neoformans, Pneumocystis jirovecii, Mucormycetes, Taloromyces, ringworm, Blastomyces, Coccidioides, Cryptococcus gattii, Histoplasma, Paracoccidioides, or Sporolhrix infection.

75. A method of manufacturing the anti-human CD28 antibody or antigen-binding antibody fragment of any one of claims 1-11 or the multi-specific antibody of any one of claims 12- 68. comprising:(a) culturing cells comprising the nucleic acid of claim 69 in a condition that allows for expression of said antibody or antigen-binding antibody fragment or said multispecific antibody, and(b) harvesting and purifying the antibody or antigen-binding antibody fragment or the multispecific antibody from the cell culture from (a).

76. A method of manufacturing the isolated, recombinant, and / or host cell of claim 71 or a population of such cells, comprising introducing the nucleic acid of claim 69 and / or the vector of claim 70 into one or more cells, optionally wherein the introducing occurs in vitro, ex vivo, or in vivo.

77. The anti-human CD28 antibody or antigen-binding antibody fragment of any one of claims 1-11 or the multi-specific antibody of any one of claims 12-68. the nucleic acid of claim 69, the vector of claim 70, the isolated, recombinant, and / or host cell of claim 71 or a population of such cells, the composition of claim 72, for use in medicine.

78. The anti-human CD28 antibody or antigen-binding antibody fragment of any one of claims 1-11 or the multi-specific antibody of any one of claims 12-68, the nucleic acid of claim 69, the vector of claim 70, the isolated, recombinant, and / or host cell of claim 71 or a population of such cells, the composition of claim 72. for use in treating a disease, disorder, or condition, optionally wherein the disease, disorder, or condition comprises any one or more of those according to claim 74.

79. Use of the anti-human CD28 antibody or antigen-binding antibody fragment of any one of claims 1-11 or the multi-specific antibody of any one of claims 12-68, the nucleic acid of claim 69, the vector of claim 70, the isolated, recombinant, and / or host cell of claim 71 or a population of such cells, the composition of claim 72. for the manufacture of a medicament for treatment of a disease, disorder, or condition, optionally wherein the disease, disorder, or condition comprises any one or more of those according to claim 74.

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