DLL3 antigen binding constructs

Abstract

Provided herein are antigen binding constructs, including antibodies and fragments thereof, such as minibodies and cys-diabodies, that bind to a target molecule, for example, DLL3. In some embodiments, the antigen binding constructs include novel complementarity-determining region (CDR) sequences and / or sequences associated with and / or part of the CDR sequence.

Description

TLTX.009WO PATENTDLL3 ANTIGEN BINDING CONSTRUCTSREFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Application No. 63 / 693396, filed September 11, 2024, which is hereby incorporated by reference in its entirety.REFERENCE TO SEQUENCE LISTING

[0002] The present application is being filed along with a Sequence Listing in electronic format. The Sequence Listing is provided as a file entitled TLlX009WO_SEQLlST.xml, which was created and last modified on September 8, 2025, which is 195,846 bytes in size. The information in the electronic Sequence Listing is hereby incorporated by reference in its entirety.FIELD

[0003] Embodiments herein relate to antigen binding constructs and minibodies. Specifically, DLL3 specific antigen binding constructs and minibodies.BACKGROUND

[0004] Delta-like protein 3 (DLL3) is an inhibitory protein of the Notch signaling pathway. DLL3 is expressed on the cell surface of small cell lung cancer (SCLC) and other highgrade endocrine tumors.SUMMARY

[0005] Provided herein is an antigen binding construct comprising: a variable light (VL) domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; a LCDR3 that is any one of SEQ ID NO: 8, 31 , 2, 52, 65, 75, or 85; and a variable heavy (VH) domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82.

[0006] Also provided is an antigen binding construct comprising: a variable light (VL) domain comprising: a LCDR1 that is an LCDR1 in any one of SEQ ID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69 or 79; a LCDR2 that is an LCDR2 in any one of SEQ ID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69 or 79; a LCDR3 that is an LCDR3 in any one of SEQ ID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69 or 79; and a variable heavy (VH) domain comprising: a HCDR1 that is an HCDR1 in any oneof SEQ ID NO: 1 , 10, 11 , 12, 13, 24, 45, 57, 68 or 78; a HCDR2 that is an HCDR2 in any one of SEQ ID NO: 1, 10, 11, 12, 13, 24, 45, 57, 68 or 78; and a HCDR3 that is an HCDR3 in any one of SEQ ID NO: 1, 10, 11, 12, 13, 24, 45, 57, 68 or 78.

[0007] Provided herein is a minibody that binds to DLL3, the minibody comprising: a single-chain variable fragment (scFv) that binds to DLL3, the scFv comprising a variable light (VL) domain linked to a variable heavy (VH) domain, the VL domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85; and the VH domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82; a hinge-extension domain comprising a hinge region; and a CH3 domain.

[0008] Also provided is an antigen binding construct comprising: a VL domain comprising: a LCDR1 that is of SEQ ID NO: 6; a LCDR2 that is of SEQ ID NO: 7; a LCDR3 that is of SEQ ID NO: 8; and a VH domain comprising: a HCDR1 that is any one of SEQ ID NO: 3 or 18; a HCDR2 that is of SEQ ID NO: 4; and a HCDR3 that is any one of SEQ ID NO: 5 or 19; a hinge-extension domain comprising a hinge region; and a CH3 domain.

[0009] Also provided is an antigen binding construct comprising: a VL domain comprising: a LCDR1 that is of SEQ ID NO: 29; a LCDR2 that is of SEQ ID NO: 30; a LCDR3 that is any one of SEQ ID NO: 31 or 32; and a VH domain comprising: a HCDR1 that is of SEQ ID NO: 26; a HCDR2 that is of SEQ ID NO: 27; and a HCDR3 that is of SEQ ID NO: 28, a hingeextension domain comprising a hinge region; and a CH3 domain.

[0010] Provided herein is an antigen binding construct comprising: a VL domain comprising: a LCDR1 that is of SEQ ID NO: 50; a LCDR2 that is of SEQ ID NO: 51; a LCDR3 that is of SEQ ID NO: 52; and a VH domain comprising: a HCDR1 that is of SEQ ID NO: 47; a HCDR2 that is of SEQ ID NO: 48; and a HCDR3 that is of SEQ ID NO: 49; a hinge-extension domain comprising a hinge region; and a CH3 domain.

[0011] Further provided is an antigen binding construct comprising: a VL domain comprising: a LCDR1 that is of SEQ ID NO: 63; a LCDR2 that is of SEQ ID NO: 64; a LCDR3 that is of SEQ ID NO: 65; and a VH domain comprising: a HCDR1 that is of SEQ ID NO: 59; aHCDR2 that is of SEQ ID NO: 60; and a HCDR3 that is any one of SEQ ID NO: 61 or 62; a hingeextension domain comprising a hinge region; and a CH3 domain.

[0012] Provided herein is an antigen binding construct comprising: a VL domain comprising: a LCDR1 that is of SEQ ID NO: 73; a LCDR2 that is of SEQ ID NO: 74; a LCDR3 that is of SEQ ID NO: 75; and a VH domain comprising: a HCDR1 that is of SEQ ID NO: 70; a HCDR2 that is of SEQ ID NO: 71; and a HCDR3 that is of SEQ ID NO: 72; a hinge-extension domain comprising a hinge region; and a CH3 domain.

[0013] Also provided is an antigen binding construct comprising: a single-chain variable fragment (scFv) that binds to DLL3, the scFv comprising a variable light (VL) domain linked to a variable heavy (VH) domain, the VL domain comprising: a LCDR1 that is of SEQ ID NO: 83; a LCDR2 that is of SEQ ID NO: 84; a LCDR3 that is of SEQ ID NO: 85; and a VH domain comprising: a HCDR1 that is of SEQ ID NO: 80; a HCDR2 that is of SEQ ID NO: 81; and a HCDR3 that is of SEQ ID NO: 82; a hinge-extension domain comprising a hinge region; and a CH3 domain.

[0014] Also provided is a minibody comprising an amino acid sequence of any one of SEQ ID NO: 110-135 (with or without the signal sequence), or a sequence at least 90% identical thereto.

[0015] Also provided is a nucleic acid encoding an antigen binding construct or minibody of any one of the embodiments described herein. Further provided is a cell line producing an antigen binding construct or minibody of any one of the embodiments described herein. Provided herein is a cell line producing an antigen binding construct or minibody, of any one of the embodiments described herein. Further provided is a kit comprising: an antigen binding construct or minibody, of any one of the embodiments described herein; and a detectable marker. Provided herein is a kit comprising: an antigen binding construct or minibody, of any one of the embodiments described herein; and a chelator, wherein the chelator allows incorporation of a detectable marker. Also provided is a kit comprising: an antigen binding construct or minibody, of any one of the embodiments described herein; and a chelator, wherein the chelator allows incorporation of a therapeutic isotope. Provided herein is a kit comprising: an antigen binding construct or minibody, of any one of the embodiments described herein; and a linker, wherein the linker allows incorporation of a detectable marker. Also provided is a kit comprising: an antigen binding construct or minibody, of any one of the embodiments described herein; and a linker,wherein the linker allows incorporation of a therapeutic isotope. Further provide is a kit comprising: an antigen binding construct or minibody, of any one of the embodiments described herein; and a detectable marker.

[0016] Also provided is a method of detecting a presence or absence of a DLL3, the method comprising: applying the antigen binding construct or minibody, of any of the embodiments described herein to a sample; and detecting a presence or an absence of the antigen binding construct or mininbody, thereby detecting a presence or absence of a DLL3.

[0017] Provided herein is a method of targeting a therapeutic agent to DLL3, the method comprising administering to a subject an antigen binding construct or minibody, of any one of the embodiments described herein, wherein the antigen binding construct is conjugated to a therapeutic agent.

[0018] Provided herein is therapeutic composition targeting DLL3, wherein the therapeutic composition comprises: an antigen binding construct that comprises: a variable light (VL) domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85; a variable heavy (VH) domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82; and a therapeutic agent, toxic payload, and / or a detectable marker.

[0019] Further provided is a therapeutic composition targeting DLL3, wherein the therapeutic composition comprises: a minibody that binds to DLL3, the minibody comprising: a single-chain variable fragment (scFv) that binds to DLL3, the scFv comprising a variable light (VL) domain linked to a variable heavy (VH) domain, the VL domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85; the VH domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82; a hinge-extension domain comprising a IgGl hinge region; a IgG CH3 sequence; and a therapeutic agent, toxic payload, and / or a detectable marker.

[0020] Further provided is a therapeutic composition targeting DLL3, wherein the therapeutic composition comprises a minibody that binds to DLL3, the minibody comprising anyone of SEQ ID NO: 110- 135 (with or without the signal sequence), or a sequence at least 85% identical thereto.

[0021] Also provided is a therapeutic composition targeting DLL3, wherein the therapeutic composition comprises: a cys-diabody that binds to DLL3, the cys-diabody comprising a polypeptide that comprises: a single-chain variable fragment (scFv) comprising a variable light (VL) domain linked to a variable heavy (VH) domain; the VL domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85; the VH domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82; and a therapeutic agent, toxic payload, and / or a detectable marker.

[0022] Provided herein is an antigen binding construct that binds DLL3, wherein the antigen binding construct is a nanobody®-Fc that binds DLL3 and comprises a variable heavy (VH) domain linked to a Fc region via a hinge domain.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 shows some non-limiting embodiments of polypeptide sequences of antigen binding constructs. (SEQ ID NO: 1-23).

[0024] FIG. 2 shows some non-limiting embodiments of a polypeptide sequence of antigen binding constructs. (SEQ ID NO: 24-44).

[0025] FIG. 3 shows some non-limiting embodiments of a polypeptide sequence of antigen binding constructs. (SEQ ID NO: 45-56).

[0026] FIG. 4 shows some non-limiting embodiments of a polypeptide sequence of antigen binding constructs. (SEQ ID NO: 57-67).

[0027] FIG. 5 shows some non-limiting embodiments of a polypeptide sequence of antigen binding constructs. (SEQ ID NO: 68-77).

[0028] FIG. 6 shows some non-limiting embodiments of a polypeptide sequence of antigen binding constructs. (SEQ ID NO: 78-87).

[0029] FIG. 7 is a graph showing some non-limiting embodiments of EC50 determinations of antigen binding constructs (e.g., minibodies) by ELISA.

[0030] FIG. 8 is a graph showing some non-limiting embodiments of EC50 determinations of antigen binding constructs (c.g., minibodics) by ELISA.

[0031] FIG. 9 is a collection of graphs showing some non-limiting embodiments of EC50 determinations of antigen binding constructs (e.g., minibodies) by ELISA.

[0032] FIG. 10 is a collection of graphs showing some non-limiting embodiments of EC50 determinations of antigen binding constructs (e.g., minibodies) by flow cytometry.

[0033] FIG. 11 is a graph showing some non-limiting embodiments of EC50 determinations of antigen binding constructs (e.g., minibodies) by ELISA.

[0034] FIG. 12 is a graph showing some non-limiting embodiments of EC50 determinations of antigen binding constructs (e.g., minibodies) by ELISA.

[0035] FIG. 13 is a graph showing some non-limiting embodiments of EC50 determinations of antigen binding constructs (e.g., minibodies) by ELISA.

[0036] FIG. 14 is a graph showing some non-limiting embodiments of EC50 determinations of antigen binding constructs (e.g., minibodies) by flow cytometry.

[0037] FIG. 15 is a graph showing some non-limiting embodiments of EC50 determinations of antigen binding constructs (e.g., minibodies) by ELISA.

[0038] FIG. 16 shows some non-limiting embodiments of a CH3 polypeptide sequence. (SEQ ID NO: 89-109).

[0039] FIG. 17 shows (including signal peptide) non-limiting embodiments of a polypeptide sequence of human-DLL3. (SEQ ID NO: 88).

[0040] FIG. 18 shows some non-limiting embodiments of a polypeptide sequence of minibodies (SEQ ID NO: 110-135).DETAILED DESCRIPTION

[0041] Described herein are antigen binding constructs, including antibodies and fragments thereof, such as minibodies or cys-diabodies. In some embodiments, these bind to a target molecule, for example, DLL3. In some embodiments, the antigen binding constructs include novel complementarity-determining region (CDR) sequences and / or sequences associated with and / or part of the CDR sequence. In some embodiments, the antigen binding constructs include novel framework region (FR) sequences and / or sequences associated with and / or part of the FR sequence. These CDR and FR sequences can provide various benefits and improvements over theart. Also provided herein are the antigen binding constructs (such as, minibodies or cys-diabodies) that include one or more of the CDR or FR sequences or subsequences provided herein.

[0042] In some embodiments, the antigen binding constructs can be useful for targeting therapeutic agents to cells that express the target molecule. In some embodiments, methods are provided for detecting the presence or absence of a target molecule (or “target”) using antigen binding constructs (including antibodies, cys-diabodies, and minibodies). In some embodiments, methods are provided for using the antigen binding constructs for therapeutic purposes.

[0043] In some embodiments, antigen binding constructs such as minibodies can have superior pharmacokinetic properties, for example for faster diagnostic imaging, while maintaining the binding specificity and affinity of the parental antibody. Current technology utilizes imaging with full-length antibodies which often require significantly longer times (~7-8 days postinjection) to produce high contrast images due to the slow serum clearance of the intact antibody. Some embodiments of the antigen binding constructs and minibodies provided herein provide the opportunity for same-day or next-day imaging.

[0044] In some embodiments, the antigen binding constructs are for diagnostics. When labeled with an appropriate radionuclide (e.g., the positron emitter Iodine-124, Copper-64, Fluorine- 18, Gallium-68 and / or Zirconium-89 for PET imaging) or fluorophore (for fluorescent imaging), or infrared dyes for optical imaging, the antibody fragments can be used for preclinical imaging as shown herein and for clinical imaging in patients. These antigen binding constructs can also be used as potential SPECT imaging agents by simply changing the radiolabel to single photon emitting radionuclides such as Indium-I l l, Iodine-123, Technetium-99M, and Lutitium-177.

[0045] In some embodiments, the antigen binding constructs can be clinical imaging agents (PET / SPECT) in humans. Accordingly, in some embodiments, antigen binding constructs can be used for targeted diagnostic detection for these disorders. In some embodiments, the antigen binding construct can be used as a therapeutic.Definitions

[0046] All terms have their ordinary and customary meaning as understood by one of ordinary skill in the art, in view of the present disclosure.

[0047] The term “antigen binding construct” includes all varieties of antibodies, including binding fragments thereof. Further included are constructs that include 1, 2, 3, 4, 5, and / or 6 CDRs. In some embodiments, tandem scFvs can be provided, which can provide twoarms with bivalent binding. In some embodiments, these CDRs can be distributed between their appropriate framework regions in a traditional antibody. In some embodiments, the CDRs can be contained within a heavy and / or light chain variable region. In some embodiments, the CDRs can be within a heavy chain and / or a light chain. In some embodiments, the CDRs can be within a single peptide chain. Unless otherwise denoted herein, the antigen binding constructs described herein bind to the noted target molecule. The term “target” or “target molecule” denotes the protein to which the antigen binding construct binds. Examples of target proteins are known in the art, and include, for example DLL3. In some embodiments, DLL3 has an amino acid sequence set forth in SEQ ID NO: 88.

[0048] The term “antibody” includes, but is not limited to, genetically engineered or otherwise modified forms of immunoglobulins, such as intrabodies, chimeric antibodies, fully human antibodies, humanized antibodies, antibody fragments, single-chain variable fragment (scFv), and heteroconjugate antibodies (for example, bispecific antibodies, diabodies, triabodies, tetrabodies, and nanobodies, etc.). The term “antibody” includes minibodies, diabodies and scFv- Fc. The term “antibody” includes a polypeptide of the immunoglobulin family or a polypeptide comprising fragments of an immunoglobulin that is capable of noncovalently, reversibly, and in a specific manner bind a corresponding antigen. An exemplary antibody structural unit comprises a tetramer. In some embodiments, a full-length antibody can be composed of two identical pairs of polypeptide chains, each pair having one “light” and one “heavy” chain (connected through a disulfide bond). The recognized immunoglobulin genes include the kappa, lambda, alpha, gamma, delta, epsilon, hinge, and mu constant region genes, as well as the myriad immunoglobulin variable region genes. For full length chains, the light chains are classified as either kappa or lambda. For full length chains, the heavy chains are classified as gamma, mu, alpha, delta, or epsilon, which in turn define the immunoglobulin classes, IgG, IgM, IgA, IgD, and IgE, respectively. The N- terminus of each chain defines a variable region of up to about 149 or more amino acids primarily responsible for antigen recognition. The terms variable light chain (VE) and variable heavy chain (VH) refer to these regions of light and heavy chains respectively. As used in this application, an “antibody” encompasses all variations of antibody and fragments thereof. Also, the term “antibody” includes camelid derived immunoglobulins like single heavy-chain antibodies and nanobodies®. Thus, within the scope of this concept are full length antibodies, chimeric antibodies, humanized antibodies, single chain antibodies (scFv), Fab, Fab', and multimericversions of these fragments (for example, F(ab')2) with the same binding specificity, scFv-Fc, single domain fragments (c.g., nanobodics®), pcptibodics, nanobodics®, nanobody®-Fc, minibodies, and diabodies. In some embodiments, the antibody binds specifically to a desired target.

[0049] The term "complementarity-determining domains" or " complementarity - determining regions ("CDRs") interchangeably refer to the hypervariable regions of VL and VH. The CDRs are the target molecule-binding site of the antibody chains that harbor specificity for such target molecule. In some embodiments, there are three CDRs (CDR1-3, numbered sequentially from the N-terminus) in each VL and / or VH, constituting about 15-20% of the variable domains. The CDRs are structurally complementary to the epitope of the target molecule and are thus directly responsible for the binding specificity. The remaining stretches of the VL or VH, the so-called FRs, exhibit less variation in amino acid sequence (Kuby, Immunology, 4th ed., Chapter 4. W.H. Freeman & Co., New York, 2000).

[0050] The positions of the CDRs and framework regions can be determined using various well known definitions in the art, for example, Kabat (Wu, T. T. et al., “An analysis of the sequences of the variable regions of Bence Jones proteins and myeloma light chains and their implications for antibody complementarity,” J. Exp. Med., Vol. 132, No. 2, pp. 211-250, 1970; Kabat, E. A. et al., “Sequences of Proteins of Immunological Interest,” 5th Ed., NIH Publication No. 91-3242, Bethesda, MD, 1991); Chotia (Chothia C. et al., “Canonical structures for the hypervariable regions of immunoglobulins,” J. Mol. Biol., Vol. 196, No. 4, pp. 901-917, 1987; Chothia C. et al., “Conformations of immunoglobulin hypervariable regions,” Nature, Vol. 342, No. 6252, pp. 877-883, 1989; Chothia C. et al., "Structural repertoire of the human VH segments," J. Mol. Biol., Vol. 227, No. 3, pp. 799-817, 1992; Al-Lazikani B. et al., “Standard conformations for the canonical structures of immunoglobulins,” J. Mol. Biol., Vol. 273, No. 4, pp. 927-748, 1997), ImMunoGeneTics database (IMGT) (on the worldwide web at imgt.org / ) (Giudicelli, V. et al., “IMGT / LIGM-DB, the IMGT® comprehensive database of immunoglobulin and T cell receptor nucleotide sequences,” Nucleic Acids Res., Vol. 34 (Database Issue), pp. D781-D784, 2006; Lefranc, M. P. et al., “IMGT unique numbering for immunoglobulin and T cell receptor variable domains and Ig superfamily V-like domains,” Dev. Comp. Immunol., Vol. 27, No. 1, pp. 55-77, 2003; Brochet, X. et al., “IMGT / V-QUEST: the highly customized and integrated system for IG and TR standardized V-J and V-D-J sequence analysis,” Nucleic Acids Res., Vol. 36 (WebServer Issue), pp. W5O3-5O8, 2008); AbM (Martin, A. C. et al., “Modeling antibody hypervariable loops: a combined algorithm, ’’Proc. Natl. Acad. Sci. U.S.A., Vol. 86, No. 23, pp. 9268-9272, 1989); AHo (Honegger A, Pliickthun A. Yet another numbering scheme for immunoglobulin variable domains: an automatic modeling and analysis tool. J Mol Biol. (2001) 309:657-70); Gelfand (Gelfand IM, Kister a E. Analysis of the relation between the sequence and secondary and three-dimensional structures of immunoglobulin molecules. Proc Natl Acad Sci USA. (1995) 92:10884-8); North (North B, Lehmann A, Dunbrack RLJ. A new clustering of antibody CDR loop conformations. J Mol Biol. (2011) 406:228-56); the contact definition (MacCallum, R. M. et al., “Antibody-antigen interactions: contact analysis and binding site topography,” J. Mol. Biol., Vol. 262, No. 5, pp. 732-745, 1996), and / or the automatic modeling and analysis tool (Honegger, A. et al., Accessible on the world wide web at bioc.uzh.ch / plueckthun / antibody / Numbering / ). In some embodiments, the polypeptide is numbered from the beginning of the polypeptide signal sequence. In some embodiments, the polypeptide is numbered according from the beginning of the polypeptide and not including the signal sequence.

[0051] An "antibody variable light chain" or an "antibody variable heavy chain" as used herein refers to a polypeptide comprising the VL or VH, respectively. The endogenous VL is encoded by the gene segments V (variable) and J (junctional), and the endogenous VH by V, D (diversity), and J. Each VL or VH includes the CDRs as well as the framework regions. In this application, antibody variable light chains and / or antibody variable heavy chains may, from time to time, be collectively referred to as "antibody chains." These terms encompass antibody chains containing mutations that do not disrupt the basic structure of VL or VH, as one skilled in the art will readily recognize. In some embodiments, full length heavy and / or light chains are contemplated. In some embodiments, only the variable region of the heavy and / or light chains are contemplated as being present.

[0052] The term “hinge” denotes at least a part of a hinge region for an antigen binding construct, such as an antibody, a minibody, a scEv-Ec, or a nanobody®-Fc. A hinge region can include a combination of the upper hinge, core (or middle) hinge and lower hinge regions. In some embodiments, the hinge is defined according to any of the antibody hinge definitions. Native IgGl, IgG2, and IgG4 antibodies have hinge regions of 12-15 amino acids. IgG3 has an extended hinge region, having 62 amino acids, including 21 prolines and 11 cysteines. The functional hinge region of naturally occurring antibodies, deduced from crystallographic studies, extends from amino acidresidues 216-237 of the IgGl H chain (EU numbering; ref. 12) and includes a small segment of the N terminus of the CH2 domain in the lower hinge, with the lower hinge being the N terminus of CH2 domain. The hinge can be divided into three regions: the "upper hinge," the "core," and the "lower hinge".

[0053] The term “artificial” or “non-natural” when modifying a hinge (or a subpart thereof) denotes that the sequence in question is not present, in the noted state, in nature. In the present context the hinges have been altered from their native state, so that their sequences are no longer those found in wild-type antibodies. As will be appreciated by those of skill in the ail, minibodies do not naturally occur in nature, and thus, any construct which is a minibody construct is also not found in nature. This also applies to at least some of the constructs found in and / or incorporating the sequences of any of the hinge sequence tables provided herein (for example, Table 4). In some embodiments, any of the hinge subparts or full hinge sequences can be artificial hinge sequences, as long as the sequence (or resulting combination for the hinge) does not occur in nature.

[0054] The term “full hinge region” or “entire hinge region” denotes the presence of the entire upper, core, and lower hinge regions as a single construct. The upper, core, and lower regions can be positioned immediately adjacent to one another, or additional residues can be added between, or N- or C-terminal to the regions. In some embodiments, the native lower hinge can be replaced with an extension sequence. In some embodiments, one can combine a native lower hinge with the extension sequence. In some embodiments, an extension or other set of sequences can be added after the upper and / or core sequences.

[0055] The phrase “effective hinge region” denotes that an adequate amount of pail of at least one of the upper, core and lower hinge regions is present to allow the hinge region to be effective for its intended purpose. Thus, the phrase encompasses variants of hinge regions and fragments of the various hinge regions. In some embodiments, the function of the hinge region is one or more of the following: to link the scFv with the CH3 domain, provide flexibility and spacing for the two scFvs to bind to the target properly, to link two half molecules together, to provide overall stability to the molecule, and / or to provide a site for site-specific conjugation due to its solvent exposure. In some embodiments, the hinge should be close to natural so as to reduce potential immunogenicity. In some embodiments, the upper hinge provides flexibility to scFv(starts at residue 216 in native IgGs), the middle hinge provides stability, and the lower hinge mediates flexibility to CH3 (starts at residue 231 in native IgGs).

[0056] The term “upper hinge” denotes the first part of the hinge that starts at the end of the scFv. The upper hinge includes the amino acids from the end of the scFv up to, but not including the first cysteine residue in the core hinge. As above, the term “effective upper hinge” denotes that enough of the sequence is present to allow the section to function as an upper hinge; the term encompasses functional variants and fragments of the designated hinge section.

[0057] The term “core hinge” denotes the second part of the hinge region that is C- terminal to the upper hinge. The core hinge contains the inter-chain disulfide bridges and a high content of prolines. As above, the term “effective core hinge” denotes that enough of the sequence is present to allow the section to function as a core hinge; the term encompasses functional variants and fragments of the designated hinge section.

[0058] The term “lower hinge” denotes the third part of the hinge region that is C terminal to the core hinge. In the context of a minibody or antibody fragment, the lower hinge connects to the CH3 domain. As above, the term “effective lower hinge” denotes that enough of the sequence is present to allow the section to function as a lower hinge; the term encompasses functional variants and fragments of the designated hinge section. The term “lower hinge” as used herein can encompass various amino acid sequences including naturally occurring IgG lower hinge sequences and artificial extension sequences in place of one another or a combination thereof provided herein. In some embodiments, the various extensions can be considered to be a lower hinge region in its entirety or a replacement.

[0059] Antibodies can exist as intact immunoglobulins or as a number of fragments produced by digestion with various peptidases. Thus, for example, pepsin digests an antibody below the disulfide linkages in the hinge region to produce F(ab)'2, a dimer of Fab' which itself is a light chain (VL-CL) joined to VH-CH1 by a disulfide bond. The F(ab)'2 may be reduced under mild conditions to break the disulfide linkage in the hinge region, thereby converting the F(ab)'2 dimer into a Fab' monomer. The Fab' monomer is a Fab with part of the hinge region. (Paul, W. E., “Fundamental Immunology,” 3d Ed., New York: Raven Press, 1993). While various antibody fragments are defined in terms of the digestion of an intact antibody, one of skill will appreciate that such fragments may be synthesized de novo either chemically or by using recombinant DNA methodology. Thus, the term "antibody," as used herein, also includes antibody fragments eitherproduced by the modification of whole antibodies, or those synthesized de novo using recombinant DNA methodologies (for example, single chain Fv) or those identified using phage display libraries (see, for example, McCafferty, J. et al., “Phage antibodies: filamentous phage displaying antibody variable domains,” Nature, Vol. 348, No. 66301, pp. 552-554, 1990). For preparation of monoclonal or polyclonal antibodies, any technique known in the art can be used (see, for example, Kohler, G. et al., “Continuous cultures of fused cells secreting antibody of predefined specificity,” Nature, Vol. 256, No. 5517, pp. 495-497, 1975; Kozbor, D. et al., “The production of monoclonal antibodies from human lymphocytes,” Immunology Today, Vol. 4, No. 3, pp. 72-79, 1983; Cole, et al., “Monoclonal Antibodies and Cancer Therapy,” Alan R. Liss, Inc., pp. 77-96, 1985; Wang, S., “Advances in the production of human monoclonal antibodies,” Antibody Technology Journal, Vol. 1, pp. 1-4, 2011; Sharon, J. et al., “Recombinant polyclonal antibodies for cancer therapy,” J. Cell Biochem., Vol. 96, No. 2, pp. 305-313, 2005;; Haurum, J. S., “Recombinant polyclonal antibodies: the next generation of antibody therapeutics?,” Drug Discov. Today, Vol. 11, No. 13- 14, pp. 655-660, 2006). Techniques for the production of single chain antibodies (U.S. Pat. No. 4,946,778) can be adapted to produce antibodies to polypeptides of the present disclosure. Also, transgenic mice, or other organisms such as other mammals, may be used to express fully human monoclonal antibodies. Furthermore, mammalian cells or E. Coli or yeast may be used to express and manufacture recombinant antibodies and antibody fragments (Simmons L. C., Reilly D., Klimowski L., Shantha Raju T., Meng G., Sims P., Hong K., Shields R. L., Damico L. A., Rancatore P., Yansura D. G.; Expression of full-length immunoglobulins in Escherichia coli: rapid and efficient production of aglycosylated antibodies, J Immunol Methods. 2002 May 1;263(1- 2): 133-47; Kulagina N, Besseau S, Godon C, Goldman G. H., Papon N., Courdavault V., Yeasts as biopharmaceutical production platforms; Front. Fungal Biol., 22 September 2021). Alternatively, phage display and yeast display technologies can be used to identify high affinity binders to selected antigens (see, for example, McCafferty et al., supra; Marks, J. D. et al., “Bypassing immunization: building high affinity human antibodies by chain shuffling,” Biotechnology (N. Y.), Vol. 10, No. 7, pp. 779-783, 1992; Feldhaus M. J., Siegel R. W., Yeast display of antibody fragments: a discovery and characterization platform, J Immunol Methods, 2004 Jul;290(l-2):69- 80). Alternatively, antibodies can be produced through B-cell screening technologies from human hosts (Pedrioli A., Oxenius A., Single B cell technologies for monoclonal antibody discovery, Trends in Immunology, (2021) volume 42, issue 12, pl 143-1158). Furthermore, antibodies can bederived from immunization of camelid animals or screening of camelid phage libraries (Harmsen M. M., De Haard H. J., Properties, production, and applications of camelid single-domain antibody fragments, Appl Microbiol Biotechnol. 2007; 77(1): 13-22). Alternatively, antibodies can be derived from in-silico screening simulations through deep learning and artificial intelligence algorithms (Graves J., Byerly J., Priego E., Makkapati N., Vince Parish S., Brenda Medellin and Monica Berrondo, A Review of Deep Learning Methods for Antibodies, Antibodies 2020, 9, 12).

[0060] Methods for humanizing or primatizing non-human antibodies are well known in the ail. Generally, a humanized antibody has one or more amino acid residues introduced into it from a source which is non-human. These non-human amino acid residues are often referred to as import residues, which are typically taken from an import variable domain. In some embodiments, the terms “donor” and “acceptor” sequences can be employed. Humanization can be essentially performed following the method of Winter and co-workers (see, for example, Jones, P. T. et al., “Replacing the complementarity-determining regions in a human antibody with those from a mouse,” Nature, Vol. 321, No. 6069, pp. 522-525, 1986; Riechmann, L. et al., “Reshaping human antibodies for therapy,” Nature, Vol. 332, No. 6162, pp. 323-327, 1988; Verhoeyen, M. et al., “Reshaping human antibodies: grafting an antilysozyme activity,” Science, Vol. 239, No. 4847, pp. 1534-1536, 1988; Presta, L. G., “Antibody engineering,”, Curr. Op. Struct. Biol., Vol. 2, No. 4, pp. 593-596, 1992), by substituting rodent CDRs or CDR sequences for the corresponding sequences of a human antibody. Accordingly, such humanized antibodies are chimeric antibodies (U.S. Pat. No. 4,816,567), wherein substantially less than an intact human variable domain has been substituted by the corresponding sequence from a non-human species. In practice, humanized antibodies are typically human antibodies in which some complementarity determining region ("CDR") residues and possibly some framework ("FR") residues are substituted by residues from analogous sites in rodent antibodies.

[0061] The term "Fc region" or “Fc domain” or “Fc” denotes a C-terminal region of an immunoglobulin heavy chain. The "Fc region" may be a native sequence Fc region or a variant Fc region (e.g., a variant having one or more mutations that reduces an effector function, e.g., FcyR binding, and / or binding to the Fc neonatal receptor (FcRn), etc.). The Fc region of an immunoglobulin (e.g., IgG) generally comprises two constant domains, CH2 and CH3. The Fc region can include a hinge region or sequence, as described herein. An Fc region can be presentin dimer or monomeric form. In some embodiments, the Fc region is a human Fc region, or a variant thereof.

[0062] A "chimeric antibody" is an antibody molecule in which (a) the constant region, or a portion thereof, is altered, replaced or exchanged so that the antigen binding site (variable region) is linked to a constant region of a different or altered class, effector function and / or species, or an entirely different molecule which confers new properties to the chimeric antibody, for example, an enzyme, toxin, hormone, growth factor, and drug; or (b) the variable region, or a portion thereof, is altered, replaced or exchanged with a variable region having a different or altered antigen specificity.

[0063] The term "‘antibody fragment” includes, but is not limited to one or more antigen binding fragments of antibodies alone or in combination with other molecules, including, but not limited to Fab, Fab', F(ab')2, Fv, rlgG (reduced IgG), scFv fragments, scFv-Fc, single domain fragments (e.g., nanobodies® or single domain fragments), peptibodies, nanobodies®, nanobody®-Fc, minibodies, and diabodies. The term “scFv” refers to a single chain Fv (“fragment variable”) antibody in which the variable domains of the heavy chain and of the light chain of a traditional two chain antibody have been joined to form one chain.

[0064] The term “artificial” or “non-natural” when modifying a CDR or FR (or a subpart thereof) denotes that the sequence in question is not present, in the noted state, in nature. In the present context the CDRs or FRs have been altered from their native state, so that their sequences are no longer those found in wild-type antibodies. As will be appreciated by those of skill in the art, minibodies and cys-diabodies do not naturally occur in nature, and thus, any construct which is a minibody or a cys-diabody construct is also not found in nature. This also applies to at least some of the constructs found in and / or incorporating the sequences of any of the CDR or FR sequence tables provided herein. In some embodiments, any of the CDR or FR sequences in the figures or tables, for example in Fig. 1, Table 1, or Table 2, can be artificial CDR or FR sequences, as long as the sequence (or resulting combination for the CDR or FR) does not occur in nature.

[0065] A “minibody” is an antibody format that has a smaller molecular weight than the full-length antibody while maintaining the bivalent binding property against an antigen. Because of its smaller size, absence of CH2 domain that binds Fc-gamma and FcRn receptors, absence of glycosylation, the minibody has a faster clearance from the system and potentiallyenhanced penetration when targeting tumor tissue. With the ability for strong targeting combined with rapid clearance, the minibody is advantageous for diagnostic imaging and delivery of radioactive payloads for which prolonged circulation times may result in adverse patient dosing or dosimetry. In some embodiments, it can also be advantageous for delivery of a cytotoxic payload due to the above-mentioned features such as tumor penetration and faster clearance. A “minibody” as described herein, encompasses a homodimer, wherein each monomer is a single-chain variable fragment (scFv) linked to a human IgG CH3 domain by a hinge sequence. In some embodiments, a minibody is a bivalent or bispecific, covalently bound homodimer of -80 kDa. In some embodiments, each monomer (half-molecule) is comprised of a variable heavy (VH) domain linked to the corresponding variable light (VL) domain by an approximate 15-18 amino acid Gly- Ser-rich linker sequence.

[0066] A "diabody" comprises a first polypeptide chain which comprises a heavy chain variable domain (VH) connected to a light chain variable domain (VL) on the first polypeptide chain (VH-VL or VL-VH) connected by a peptide linker that does not allow pairing between the two domains on the first polypeptide chain (e.g., the peptide linker is too short to allow the pairing), and a second polypeptide chain comprising a heavy chain variable domain (VH) linked to a light chain variable domain (VL) on the second polypeptide chain (VH-VL or VL-VH) connected by a peptide linker that does not allow pairing between the two domains on the second polypeptide chain (e.g., the peptide linker is too short to allow the pairing). Without being limited by theory, the short linkages can force chain pairing between the complementary domains of the first and the second polypeptide chains and promote the assembly of a dimeric molecule with two functional antigen binding sites. Therefore, a peptide linker may be any suitable length that promotes such assembly, for example, between 5 and 20 amino acids in length. A “cys-diabody” denotes a diabody whose monomer chains are covalently linked by a disulfide bond. In some embodiments, a “cys-diabody” is a diabody with one or more than one C-terminal cysteines.

[0067] The term “extension sequence” (e.g., in a diabody context) denotes a region that connects a first VH domain to a second VH domain, or a first VL to a second VL domain, in for example, a diabody. Extension sequences can connect the domains through the C-terminus of each domain. In some embodiments, extension sequences connect the domains through covalent bonds. In some embodiments, the extension sequence will include one or more cysteine, allowing for one or more disulfide bonds to be formed between two such extension sequences. A non-limitingexample of an extension sequence includes -(Gly)2-(Cys). In some embodiments, the extension sequence includes 1, 2, 3, or more cysteines per monomer chain. While the extension sequence will be towards the C-terminus of the constructs, it need not be the absolute last amino acid in the variable domain. That is, the extension sequence can be positioned slightly N-terminal to the C- terminus. For example, the extension sequence can be placed within the 10 amino acids of the C- terminus of the monomer. Similarly, additional sequence can be placed between the native C- terminus and where the extension sequence starts. The extension sequence can connect VH to VH or VL to VL through a disulfide bond. In some embodiments, the extension sequence includes GGCPPCPPC (SEQ ID NO: 203).

[0068] As used herein, “pharmaceutically acceptable” has its plain and ordinary meaning as understood in light of the specification and refers to carriers, excipients, and / or stabilizers that are nontoxic to the cell or mammal being exposed thereto at the dosages and concentrations employed or that have an acceptable level of toxicity. A “pharmaceutically acceptable” “diluent,” “excipient,” and / or “carrier” as used herein have their plain and ordinary meaning as understood in light of the specification and are intended to include any and all solvents, dispersion media, coatings, antibacterial or antifungal agents, isotonic or absorption delaying agents, compatible with administration to humans, primates, cats, dogs, or other vertebrate hosts. Typically, a pharmaceutically acceptable diluent, excipient, and / or carrier is a diluent, excipient, and / or carrier approved by a regulatory agency of a Federal, a state government, or other regulatory agency, or listed in the U.S. Pharmacopeia or other generally recognized pharmacopeia for use in animals, including humans as well as non-human mammals, such as cats and dogs. The term diluent, excipient, and / or “carrier” can refer to a diluent, adjuvant, excipient, or vehicle with which the pharmaceutical composition is administered. Such pharmaceutical diluent, excipient, and / or carriers, which can be incorporated in any one or more of the compositions described herein, include sterile liquids, such as water and oils, including those of petroleum, animal, vegetable or synthetic origin. Water, saline solutions or aqueous dextrose and glycerol solutions can be employed as liquid diluents, excipients, and / or carriers. Suitable pharmaceutical diluents and / or excipients, which can be incorporated in any one or more of the compositions described herein, also include starch, glucose, lactose, sucrose, gelatin, malt, rice, flour, chalk, silica gel, sodium stearate, glycerol monostearate, talc, sodium chloride, dried skim milk, glycerol, propylene, glycol, water, or ethanol. The physiologically acceptable carrier may also comprise one or more of thefollowing: antioxidants, such as ascorbic acid, low molecular weight (less than about 10 residues) polypeptides, proteins, such as scrum albumin, gelatin, immunoglobulins, hydrophilic polymers such as polyvinylpyrrolidone, amino acids, carbohydrates such as glucose, mannose, or dextrins, chelating agents such as EDTA, sugar alcohols such as mannitol or sorbitol, salt-forming counterions such as sodium, and nonionic surfactants such as TWEEN®, polyethylene glycol (PEG), PLURONICS® or preservatives such as an essential oil, methyl paraben, propyl paraben, or sodium salt of parabens. In some embodiments, the preservative is bronidiol. The composition, if desired, can also contain minor amounts of wetting, bulking, emulsifying agents, or pH buffering agents. These compositions can take the form of solutions, suspensions, emulsion, sustained release formulations and the like. The formulation should suit the mode of administration.

[0069] Additional excipients with desirable properties include but are not limited to preservatives, adjuvants, stabilizers, solvents, buffers, diluents, solubilizing agents, detergents, surfactants, chelating agents, antioxidants, alcohols, ketones, aldehydes, ethylenediaminetetraacetic acid (EDTA), citric acid, salts, sodium chloride, sodium bicarbonate, sodium phosphate, sodium borate, sodium citrate, potassium chloride, potassium phosphate, magnesium sulfate sugars, dextrose, fructose, mannose, lactose, galactose, sucrose, sorbitol, cellulose, serum, amino acids, polysorbate 20, polysorbate 80, sodium deoxycholate, sodium taurodeoxycholate, magnesium stearate, octylphenol ethoxylate, benzethonium chloride, thimerosal, gelatin, esters, ethers, 2-phenoxyethanol, urea, or vitamins, or any combination thereof. In some embodiments, the formulation includes an at least one agent that acts to reduce radiolysis (also known as “radioprotectors”) or is a kidney protecting agent. Non-limiting examples of radiolysis reducing agents include Gentisic acid, Acetylcholine, AET, ACE inhibitors, acteoside, alpha-tocopherol acetate, amifostine, ascorbic acid, aspirin, atorvastatin, beta-carotene, Bowman- Birk proteinase inhibitor, Caffeic acid, Captopril, carbaminoylcholine, Carvacrol, Celecoxib, coenzyme Q10, COX2 inhibitors / NSAIDs, curcumin, cysteine, cysteamine, cystamine, dendrodine analog, Dithiolthione, Dopamine, enalapril, epigallocatechin-3-gallate, Epinephrine, 17- -estradiol, GANRA-5, Genistein, green tea abstract, growth factors, guanine nucleotides, Halofuginone, Hmg-CoA reductase inhibitors (statins), heroin, histamine, ibuprofen, inapoyl-E- glucoside, Isoflavone, isofraxidin, kukoamine A, lactoferrin amifostine, lipoic acid, lovastatin, luteolin-7-O-(2-apiosyl)-glucoside, 2-mercaptoethylguanidine, melatonin, methacholine, morphine, N-acetyl cysteine, Oltipraz, palifermin, phenethyl ester, polyphenols, pravastatin,protease inhibitors, quercetin-3-O-rhamnoside-7-O-glucoside, quercetin-3-O-rhamnoside, ramipril, Resveratrol, rutin, serotonin, Simvastatin, Sodium ascorbate, superoxide dismutase, TGF- signaling inhibitors, tocopherols, vitamin C, vitamin E, watermelon juice, black grape juice, and thiols such as glutathione. Kidney protecting agents include free lysine, arginine, probenecid, gelofusin, and other compositions. Some excipients may be in residual amounts or contaminants from the process of manufacturing, including but not limited to serum, albumin, ovalbumin, antibiotics, inactivating agents, formaldehyde, glutaraldehyde, P-propiolactone, gelatin, cell debris, nucleic acids, peptides, amino acids, or growth medium components or any combination thereof. The amount of the excipient may be found in the composition at a percentage that is, is about, is at least, is at least about, is not more than, or is not more than about, 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 100% w / w or any percentage by weight in a range defined by any two of the aforementioned numbers.

[0070] As used herein, a “carrier” has its plain and ordinary meaning as understood in light of the specification and refers to a compound, particle, solid, semi- solid, liquid, or diluent that facilitates the passage, delivery and / or incorporation of a compound to cells, tissues and / or bodily organs.

[0071] As used herein, a “diluent” has its plain and ordinary meaning as understood in light of the specification and refers to an ingredient in a pharmaceutical composition that lacks pharmacological activity but may be pharmaceutically necessary or desirable. For example, a diluent may be used to increase the bulk of a potent drug whose mass is too small for manufacture and / or administration. It may also be a liquid for the dissolution of a drug to be administered by injection, ingestion or inhalation. A common form of diluent in the art is a buffered aqueous solution such as, without limitation, phosphate buffered saline that mimics the composition of human blood.

[0072] The term “target molecule dependent disorder” “or “target molecule associated disorder” includes any disorder in which the target molecule plays a role in the disorder itself. In some embodiments, this denotes over-expression of the target molecule. In some embodiments, the disorders can include any of the disorders discussed herein. In some embodiments, the disorder can be any for which there is a target molecule that can be targeted by binding, whose binding will result in the detection and / or treatment of the disorder.

[0073] The term “treating”, or “treatment” of a condition can refer to preventing the condition, slowing the onset and / or rate of development of the condition, reducing the risk of developing the condition, preventing and / or delaying the development of symptoms associated with the condition, reducing or ending symptoms associated with the condition, generating a complete or partial regression of the condition, or some combination thereof. The term “prevent” does not require the absolute prohibition of the disorder or disease. Examples of disorders or diseases include fibrosis, cancer, tumor and neoplasms, autoimmune disease, cardiovascular, neurodegenerative, metabolic and endocrine disorders, inflammatory, immunity, genetic disorders, infectious disorders, hematological, congenital disorders, musculoskeletal, oral and gastrointestinal, renal and urogenital disorders, reproductive disorders, respiratory disorders, skin and / or epithelial, as well as disorders with disputed or unknown etiology.

[0074] “Tumor,” as used herein, refers to all neoplastic cell growth and proliferation, whether malignant or benign, and all pre-cancerous and cancerous cells and tissues. The terms “cancer,” “cancerous,” “cell proliferative disorder,” “proliferative disorder” and “tumor” are not mutually exclusive as referred to herein. The term “neoplasia” encompasses the term tumor.

[0075] The terms “cancer” and “cancerous” refer to or describe the physiological condition in mammals that is typically characterized by unregulated cell growth. Examples of cancer include, but are not limited to, carcinoma, lymphoma, blastoma, sarcoma, and leukemia or lymphoid malignancies. More particular examples of such cancers include lung cancer including small-cell lung cancer, non-small cell lung cancer and lung adenocarcinomas with neuroendocrine features; neuroendocrine prostate cancer, melanoma, gliomas, low-grade gliomas and glioblastoma, medullary thyroid cancer, carcinoid tumors, neuroendocrine tumors in the pancreas, bladder cancer, testicular cancer squamous cell cancer (e.g. epithelial squamous cell cancer), neuroendocrine neoplasms, such as neuroendocrine tumors of unknown primary, neuroendocrine neoplasms of the small bowel, carotid body, adrenal gland, colorectal gynecological organ, abdomen, esophagus, GI tract, bile duct, nervous system, appendix, liver, anal, thymus, ileocecal junction, head and neck, breast, peritoneum and retroperitoneum, kidney, thyroid, stomach, bone,; adenocarcinomas, such as adenocarcinoma of the lung and squamous carcinoma of the lung, cancer of the peritoneum, hepatocellular cancer, gastric or stomach cancer including gastrointestinal cancer, pancreatic cancer, glioblastoma, cervical cancer, ovarian cancer, liver cancer, bladder cancer, cancer of the urinary tract, hepatoma, breast cancer, colon cancer, rectal cancer, colorectalcancer, endometrial or uterine carcinoma, salivary gland carcinoma, kidney or renal cancer, prostate cancer, vulval cancer, thyroid cancer, bone cancer, hepatic carcinoma, anal carcinoma, penile carcinoma, melanoma, multiple myeloma and B-cell lymphoma, brain, as well as head and neck cancer, and associated metastases. The term cancer includes adult and pediatric solid cancers. In some embodiments, the cancer can be a solid tumor. In some embodiments, the cancer is a highly fibrotic tumor or cancer. In some embodiments, the cancer is a desmoplasia.

[0076] A “therapeutically effective amount” or a “therapeutically effective dose” is an amount that produces a desired therapeutic effect in a subject, such as preventing, treating a target condition, delaying the onset of the disorder and / or symptoms, and / or alleviating symptoms associated with the condition. This amount will vary depending upon a variety of factors, including but not limited to the characteristics of the therapeutic compound (including activity, pharmacokinetics, pharmacodynamics, biodistribution and bioavailability), the physiological condition of the subject (including age, sex, disease type and stage, general physical condition, responsiveness to a given dosage, and type of medication), the nature of the pharmaceutically acceptable carrier or carriers in the formulation, and / or the route of administration. One skilled in the clinical and pharmacological arts will be able to determine a therapeutically effective amount through routine experimentation, for example by monitoring a subject's response to administration of a compound and adjusting the dosage accordingly, given the present disclosure. For additional guidance, see Remington: The Science and Practice of Pharmacy 21st Edition, Univ, of Sciences in Philadelphia (USIP), Lippincott Williams & Wilkins, Philadelphia, PA, 2005. In the context of radiopharmaceutical therapy, the terms “therapeutically effective amount” or a “therapeutically effective dose” or a “therapeutically effective activity” can be used interchangeably.

[0077] “Label”, “detectable label” or “detectable marker” are used interchangeably herein and refer to a detectable compound or composition which is conjugated directly or indirectly associated with the antibody so as to generate a “labeled” antibody. The label may be detectable by itself (e.g., radioisotope labels or fluorescent labels) or, in the case of an enzymatic label, may catalyze chemical alteration of a substrate compound or composition which is detectable.

[0078] The term “payload” denotes an atom or molecule or other entity that is associated (covalently or otherwise) to an antigen binding construct. It includes labels or markers for aspects for diagnostics for example, as well as toxins, cytotoxic agents, chemotherapeutic agents for various therapies. In some embodiments, the payload involves a chelator so as to attachthe antigen binding construct to the molecule or atom to be delivered via or colocalized via the antigen binding construct.

[0079] The term “cytotoxic agent” as used herein refers to a substance that inhibits or prevents a cellular function and / or causes cell death or destruction. The term is intended to include non-radioactive isotopes (ADC), radioactive isotopes (e.g.,177Lu,225Ac,67Cu,227Th,211At,131I,125I,90Y,186Re,188Re,153Sm,212Bi,213Bi,32P,149Tb,161Tb,212Pb), chemotherapeutic agents (as defined elsewhere herein). It can also mean an agent that increases the cell-killing effect of another agent, such as DNA repair pathway inhibitors including PARP1 / PARP2 inhibitors and DNA-PK inhibitors, as described in Li L-y, Guan Y-d, Chen X-s, Yang J-m and Cheng Y (2021) DNA Repair Pathways in Cancer Therapy and Resistance. Front. Pharmacol. 11:629266. doi: 10.3389 / fphar.2020.629266. Other cytotoxic agents are described below. A tumoricidal agent causes destruction of tumor cells.

[0080] A “toxin” is any substance capable of having a detrimental effect on the growth or proliferation of a cell. Non-radioactive payloads include those commonly used for antibody drug conjugates (ADC) and fragment drug conjugates (FDC), such as toxins belonging to the families of auristatins, maytansines, maytansinoids, calicheamicins, duocarymycins, pyrrolobenzodiazepines dimers and amatoxins.

[0081] A “therapeutic ion” refers to an electrically charged particle that is useful in the treatment of a disorder related to a target molecule. Examples of therapeutic ions include18F,18F- FAC,32P,33P,45Ti,47Sc,52Fe,59Fe,62Cu, ^Cu,67Cu,67Ga,68Ga,75Sc,77As,86Y,90Y,89Sr,89Zr,94TC,94TC,99mTc, "Mo,105Pd,105Rh,n iAg,U1ln,123I,124I,125I,131I,142Pr,143Pr,149Pm,149Tb,153Sm,154-158Gd,161Tb,166Dy,166Ho,169Er,175Lu,177Lu,186Re,188Re,189Re,194Ir,198Au,199Au,211At,211Pb,212Bi,212Pb,213Bi,223Ra,227Th, and225Ac. These are also options of therapeutic agents.

[0082] A “chemotherapeutic agent” is a chemical compound useful in the treatment of cancer. Examples of chemotherapeutic agents include alkylating agents such as thiotepa and CYTOXAN™ cyclosphosphamide; alkyl sulfonates such as busulfan, improsulfan and piposulf n; aziridines such as benzodopa, carboquone, meturedopa, and uredopa; ethylenimines and methylamelamines including altretamine, triethylenemelamine, triethylenephosphoramide, triethylenethiophosphoramide and trimethylolomelamine; acetogenins (especially bullatacin and bullatacinone); delta-9-tetrahydrocannabinol (dronabinol, MARINOL™); beta-lapachone; lapachol; colchicines; betulinic acid; a camptothecin (including the synthetic analogue topotecan(HYC AMTIN™), CPT-1 1 (irinotecan, CAMPTOSAR™), acetylcamptothecin, scopolectin, and 9-aminocamptothccin); bryostatin; callystatin; CC-1065 (including its adozclcsin, carzclcsin and bizelesin synthetic analogues); podophyllo toxin; podophyllinic acid; teniposide; cryptophycins (particularly cryptophycin 1 and cryptophycin 8); dolastatin; duocarmycin (including the synthetic analogues, KW-2189 and CB1-TM1); eleutherobin; pancratistatin; a sarcodictyin; spongistatin; nitrogen mustards such as chlorambucil, chlomaphazine, cholophosphamide, estramustine, ifosfamide, mechlorethamine, mechlorethamine oxide hydrochloride, melphalan, novembichin, phenesterine, prednimustine, trofosfamide, uracil mustard; nitrosoureas such as carmustine, chlorozotocin, fotemustine, lomustine, nimustine, and ranimnustine; antibiotics such as the enediyne antibiotics (e. g., calicheamicin, especially calicheamicin gammall and calicheamicin omegall (see, e.g., Agnew, Chem Inti. Ed. Engl., 33: 183-186 (1994)); dynemicin, including dynemicin A; an esperamicin; as well as neocarzinostatin chromophore and related chromoprotein enediyne antibiotic chromophores), aclacinomysins, actinomycin, authramycin, azaserine, bleomycins, cactinomycin, carabicin, carminomycin, carzinophilin, chromomycins, dactinomycin, daunorubicin, detorubicin, 6-diazo-5-oxo-L-norleucine, ADRIAMYCIN™ doxorubicin (including morpholino-doxorubicin, cyanomorpholino-doxorubicin, 2-pyrrolino-doxorubicin and deoxy doxorubicin), epirubicin, esorubicin, idarubicin. marcellomycin, mitomycins such as mitomycin C, mycophenolic acid, nogalamycin, olivomycins, peplomycin, porfiromycin, puromycin, quelamycin, rodorubicin, streptonigrin, streptozocin, tubercidin, ubenimex, zinostatin, zorubicin; metabolic inhibitor such as methotrexate and 5 -fluorouracil (5-FU); folic acid analogues such as denopterin, methotrexate, pteropterin, trimetrexate; purine analogs such as fludarabine, 6- mercaptopurine, thiamiprine, thioguanine; pyrimidine analogs such as ancitabine, azacitidine, 6- azauridine, carmofur, cytarabine, dideoxyuridine, doxifluridine, enocitabine, floxuridine; androgens such as calusterone, dromostanolone propionate, epitiostanol, mepitiostane, testolactone; anti-adrenals such as aminoglutethimide, mitotane, trilostane; folic acid replenisher such as frolinic acid; aceglatone; aldophosphamide glycoside; aminolevulinic acid; eniluracil; amsacrine; bestrabucil; bisantrene; edatraxate; defofamine; demecolcine; diaziquone; elfornithine; elliptinium acetate; an epothilone; etoglucid; gallium nitrate; hydroxyurea; lentinan; lonidainine; maytansinoids such as maytansine and ansamitocins; mitoguazone; mitoxantrone; mopidanmol; nitraerine; pentostatin; phenamet; pirarubicin; losoxantrone; 2-ethylhydrazide; procarbazine; PSK® polysaccharide complex (JHS Natural Products, Eugene, Oreg.); razoxane; rhizoxin;sizofiran; spirogermanium; tenuazonic acid; triaziquone; 2, 2’, 2” -trichlorotriethylamine; trichothcccncs (especially T-2 toxin, vcrracurin A, roridin A and anguidinc); urcthan; vindcsinc (ELDISINE™, FILDESIN™); dacarbazine; mannomustine; mitobronitol; mitolactol; pipobroman; gacytosine; arabinoside (“Ara-C”); thiotepa; taxoids, e.g., TAXOL® paclitaxel (Bristol-Myers Squibb Oncology, Princeton, N.J.), ABRAXANE™ Cremophor-free, albumin- engineered nanoparticle formulation of paclitaxel (American Pharmaceutical Partners, Schaumberg, Ill.), and TAXOTERE™ docetaxel (Rhone-Poulenc Rorer, Antony, France); chloranbucil; gemcitabine (GEMZAR™); 6-thioguanine; mercaptopurine; methotrexate; platinum analogs such as cisplatin and carboplatin; vinblastine (VELBAN™); platinum; etoposide (VP-16); ifosfamide; mitoxantrone; vincristine (ONCOVIN™); oxaliplatin; leucovovin; vinorelbine (NAVELBINE™); novantrone; edatrexate; daunomycin; aminopterin; ibandronate; topoisomerase inhibitor RFS 2000; difluoromethylomithine (DMFO); retinoids such as retinoic acid; capecitabine (XELODA™); pharmaceutically acceptable salts, acids or derivatives of any of the above; as well as combinations of two or more of the above such as CHOP, an abbreviation for a combined therapy of cyclophosphamide, doxorubicin, vincristine, and prednisolone, and FOLFOX, an abbreviation for a treatment regimen with oxaliplatin (ELOXATIN™) combined with 5-FU and leucovovin. These are also options of therapeutic agents.

[0083] “Radiotherapy” has its customary and ordinary meaning as understood by one of ordinary skill in the ail in view of the present disclosure, and denotes treatment using radiation or a radioisotope with a therapeutic purpose. It includes radiation therapy intended to have abscopal effect as described in Yang Liu, Yinping Dong, Li Kong, Fang Shi, Hui Zhu & Jinming Yu; “Abscopal effect of radiotherapy combined with immune checkpoint inhibitors”; Journal of Hematology & Oncology volume 11, Article number: 104 (2018); and in Melek Tugce Yilmaz, Aysenur Elmali, and Gozde Yazici; “Abscopal Effect, From Myth to Reality: From Radiation Oncologists' Perspective”; Cureus. 2019 Jan; 11(1). As used herein, radiotherapy also includes the fields sometimes known in the literature as radiopharmaceutical therapy, radiopharmacotherapy (RPT). Radiotherapy can include radioimmunotherapy.

[0084] The terms "subject," "patient," and "individual" interchangeably refer to an entity that is being examined and / or treated. The term “mammal” is used in its usual biological sense. Thus, it specifically includes, but is not limited to, primates, including simians(chimpanzees, apes, monkeys), humans, cattle, horses, sheep, goats, swine, rabbits, dogs, cats, rodents, rats, mice, or guinea pigs.

[0085] The term "co-administer" refers to the administration of two active agents in the blood of an individual or in a sample to be tested. Active agents that are co-administered in combination or sequentially delivered. “In combination” means that two (or more) different compositions are delivered to the subject during the course of the subject's affliction with the disorder, e.g., the two or more compositions are delivered after the subject has been diagnosed or selected as one having the disorder and before the disorder has been cured or eliminated. In some embodiments the subject is selected to receive any one or more of the compositions described herein by diagnostic analysis or clinical evaluation or both. In some embodiments, the delivery of one therapy is still occurring when the delivery of the second begins, so that there is overlap. This is sometimes referred to herein as "simultaneous" or "concomitant" or "concurrent delivery". In other embodiments, the delivery of one therapy ends before the delivery of the other therapy begins. This is sometimes referred to herein as "successive" or "sequential delivery." In embodiments of either case, the therapy is more effective because of combined administration. For example, the second therapy is a more effective, e.g., an equivalent effect is seen with less of the second therapy, or the second therapy reduces symptoms to a greater extent, than would be seen if the second therapy were administered in the absence of the first therapy, or the analogous situation is seen with the first therapy. In some embodiments, delivery is such that the reduction in a symptom, or other parameter related to the disorder is greater than what would be observed with one therapy delivered in the absence of the other. The effect of the two therapies can be partially additive, wholly additive, or greater than additive (e.g., synergistic). The delivery can be such that an effect of the first therapy delivered is still detectable when the second is delivered.

[0086] The phrase "specifically (or selectively) bind," when used in the context of describing the interaction between an antigen, for example, a protein, to an antibody or antibody- derived binding agent, refers to a binding reaction that is determinative of the presence of the antigen in a heterogeneous population of proteins and other biologies, for example, in a biological sample, for example, a blood, serum, plasma or tissue sample. Thus, under designated immunoassay conditions, in some embodiments, the antibodies or binding agents with a particular binding specificity bind to a particular antigen at least two times the background and do not substantially bind in a significant amount to other antigens present in the sample. Specific bindingto an antibody or binding agent under such conditions may require the antibody or agent to have been selected for its specificity for a particular protein. A variety of immunoassay formats may be used to select antibodies specifically immunoreactive with a particular protein. For example, solidphase ELISA immunoassays are routinely used to select antibodies specifically immunoreactive with a protein (see, for example, Harlow, E. & Lane D., “Using Antibodies, A Laboratory Manual,” Cold Spring Harbor Laboratory Press, 1998, for a description of immunoassay formats and conditions that can be used to determine specific immunoreactivity). Typically, a specific or selective binding reaction will produce a signal at least twice over the background signal and more typically at least 10 to 100 times over the background.

[0087] The term "equilibrium dissociation constant (KD, M)" refers to the dissociation rate constant (kd, time-1) divided by the association rate constant (ka, time-1M’1). Equilibrium dissociation constants can be measured using any known method in the art. The antibodies of the present disclosure generally will have an equilibrium dissociation constant of less (that is superior binding) than about 10'7or 10'8M, for example, less than about 10'9M or 10'10M, in some embodiments, less than about 10’11M, 10‘12M, or 10'13M.

[0088] The terms "polypeptide," "peptide," and "protein" are used interchangeably herein to refer to a polymer of amino acid residues. The terms apply to amino acid polymers in which one or more amino acid residue is an artificial chemical mimetic of a corresponding naturally occurring amino acid, as well as to naturally occurring amino acid polymers and non- naturally occurring amino acid polymer.

[0089] The term "nucleic acid" or "polynucleotide" refers to deoxyribonucleic acids (DNA) or ribonucleic acids (RNA) and polymers thereof in either single- or double-stranded form. Unless specifically limited, the term encompasses nucleic acids containing known analogues of natural nucleotides that have similar binding properties as the reference nucleic acid and are metabolized in a manner similar to naturally occurring nucleotides. Unless otherwise indicated, a particular nucleic acid sequence also implicitly encompasses conservatively modified variants thereof (for example, degenerate codon substitutions), alleles, orthologs, SNPs, and complementary sequences as well as the sequence explicitly indicated. Specifically, degenerate codon substitutions may be achieved by generating sequences in which the third position of one or more selected (or all) codons is substituted with mixed-base and / or deoxyinosine residues (Batzer, M. A. et al., “Enhanced evolutionary PCR using oligonucleotides with inosine at the 3'-terminus,” Nucleic Acid Res., Vol. 19, No. 18, pp. 5081 , 1991 ; Ohtsuka, E. et al., “An alternative approach to dcoxyoligonuclcotidcs as hybridization probes by insertion of dcoxyinosinc at ambiguous codon positions,” J. Biol. Chem., Vol. 260, No. 5, pp. 2605-2608, 1985; Rossolini, G. M. et al., “Use of deoxyinosine-containing primers vs degenerate primers for polymerase chain reaction based on ambiguous sequence information,” Mol. Cell. Probes, Vol. 8, No. 2, pp. 91-98, 1994).

[0090] The term "amino acid" refers to naturally occurring and synthetic amino acids, as well as amino acid analogs and amino acid mimetics that function in a manner similar' to the naturally occurring amino acids. Naturally occurring amino acids are those encoded by the genetic code, as well as those amino acids that are later modified, for example, hydroxyproline, gammacarboxyglutamate, and O-phosphoserine. Amino acid analogs refer to compounds that have the same basic chemical structure as a naturally occurring amino acid, for example, an alpha-carbon that is bound to a hydrogen, a carboxyl group, an amino group, and an R group, for example, homoserine, norleucine, methionine sulfoxide, methionine methyl sulfonium. Such analogs have modified R groups (for example, norleucine) or modified peptide backbones, but retain the same basic chemical structure as a naturally occurring amino acid. Amino acid mimetics refers to chemical compounds that have a structure that is different from the general chemical structure of an amino acid, but that functions in a manner similar to a naturally occurring amino acid.

[0091] The term "conservatively modified variants" applies to both amino acid and nucleic acid sequences. With respect to particular nucleic acid sequences, conservatively modified variants refers to those nucleic acids which encode identical or essentially identical amino acid sequences, or where the nucleic acid does not encode an amino acid sequence, to essentially identical sequences. Because of the degeneracy of the genetic code, a large number of functionally identical nucleic acids encode any given protein. For instance, the codons GCA, GCC, GCG and GCU all encode the amino acid alanine. Thus, at every position where an alanine is specified by a codon, the codon can be altered to any of the corresponding codons described without altering the encoded polypeptide. Such nucleic acid variations are "silent variations," which are one species of conservatively modified variations. Every nucleic acid sequence herein which encodes a polypeptide also describes every possible silent variation of the nucleic acid. One of skill will recognize that each codon in a nucleic acid (except AUG, which is ordinarily the only codon for methionine, and TGG, which is ordinarily the only codon for tryptophan) can be modified to yielda functionally identical molecule. Accordingly, each silent variation of a nucleic acid that encodes a polypeptide is implicit in each described sequence.

[0092] As to amino acid sequences, one of skill will recognize that individual substitutions, deletions or additions to a nucleic acid, peptide, polypeptide, or protein sequence which alters, adds or deletes a single amino acid or a small percentage of amino acids in the encoded sequence is a "conservatively modified variant" where the alteration results in the substitution of an amino acid with a chemically similar amino acid. Conservative substitution tables providing functionally similar amino acids are well known in the art. Such conservatively modified variants are in addition to and do not exclude polymorphic variants, interspecies homologs, and alleles of the present disclosure.

[0093] The following eight groups each contain amino acids that are conservative substitutions for one another: 1) Alanine (A), Glycine (G); 2) Aspartic acid (D), Glutamic acid (E); 3) Asparagine (N), Glutamine (Q); 4) Arginine (R), Lysine (K); 5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V); 6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W); 7) Serine (S), Threonine (T); and 8) Cysteine (C), Methionine (M) (see, for example, Creighton, T. E., “Proteins - Structures and Molecular Properties,” W. H. Freeman & Co. Ltd., 1984).

[0094] The term "percentage of sequence identity" can be determined by comparing two optimally aligned sequences over a comparison window, wherein the portion of the polynucleotide sequence in the comparison window may comprise additions or deletions (i.e., gaps) as compared to the reference sequence (for example, a polypeptide of the present disclosure), which does not comprise additions or deletions, for optimal alignment of the two sequences. The percentage is calculated by determining the number of positions at which the identical nucleic acid base or amino acid residue occurs in both sequences to yield the number of matched positions, dividing the number of matched positions by the total number of positions in the window of comparison and multiplying the result by 100 to yield the percentage of sequence identity.

[0095] The terms "identical" or percent "identity," in the context of two or more nucleic acids or polypeptide sequences, refer to two or more sequences or subsequences that are the same sequences. Two sequences are "substantially identical" if two sequences have a specified percentage of amino acid residues or nucleotides that are the same (for example, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% sequence identity over a specified region, or, when not specified, over the entire sequence of a reference sequence), when compared and aligned formaximum correspondence over a comparison window, or designated region as measured using one of the following sequence comparison algorithms or by manual alignment and visual inspection. Some embodiments provided herein provide polypeptides or polynucleotides that are substantially identical to the polypeptides or polynucleotides, respectively, exemplified herein. Optionally, the identity exists over a region that is at least about 15, 25 or 50 nucleotides in length, or more preferably over a region that is 100 to 500 or 1000 or more nucleotides in length, or over the full length of the reference sequence. With respect to amino acid sequences, identity or substantial identity can exist over a region that is at least 5, 10, 15 or 20 amino acids in length, optionally at least about 25, 30, 35, 40, 50, 75 or 100 amino acids in length, optionally at least about 150, 200 or 250 amino acids in length, or over the full length of the reference sequence. With respect to shorter amino acid sequences, for example, amino acid sequences of 20 or fewer amino acids, in some embodiments, substantial identity exists when one or two amino acid residues are conservatively substituted, according to the conservative substitutions defined herein.

[0096] In some embodiments, the percent identity is over the CDR and / or FR regions noted herein. In such situations, the percent identity of the CDR or FR can be identified separately from the rest of the protein or nucleic acid sequence. Thus, two CDRs or FRs can have a specified percentage of amino acid residues or nucleotides that are the same (for example, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% sequence identity over a specified region, or, when not specified, over the entire sequence of a reference sequence), while allowing for the remainder of the protein to either stay 100% identical to the comparison protein, our while also allowing the remainder of the protein to also have variation by a specified percent identity.

[0097] For sequence comparison, typically one sequence acts as a reference sequence, to which test sequences are compared. When using a sequence comparison algorithm, test and reference sequences are entered into a computer, subsequence coordinates are designated, if necessary, and sequence algorithm program parameters are designated. Default program parameters can be used, or alternative parameters can be designated. The sequence comparison algorithm then calculates the percent sequence identities for the test sequences relative to the reference sequence, based on the program parameters.

[0098] A "comparison window", as used herein, includes reference to a segment of any one of the numbers of contiguous positions selected from the group consisting of from 20 to 600, usually about 50 to about 200, more usually about 100 to about 150 in which a sequence may becompared to a reference sequence of the same number of contiguous positions after the two sequences arc optimally aligned. Methods of alignment of sequences for comparison arc well known in the ail. Optimal alignment of sequences for comparison can be conducted, for example, by the local homology algorithm of Smith and Waterman (1970) Adv. Appl. Math. 2:482c, by the homology alignment algorithm of Needleman, S. B. et al., “A general method applicable to the search for similarities in the amino acid sequence of two proteins,” J. Mol. Biol., Vol. 48, No. 3, pp. 443-453, 1970, by the search for similarity method of Pearson, W. R. et al., “Improved tools for biological sequence comparison,” Proc. Natl. Acad. Sci. U.S.A., Vol. 85, No. 8, pp. 2444-2448, 1988, by computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Dr., Madison, Wis.), or by manual alignment and visual inspection (see, for example, Ausubel, F. M. et al., Current Protocols in Molecular Biology, Supplement, 1995).

[0099] Two examples of algorithms that are suitable for determining percent sequence identity and sequence similarity are the BLAST and BLAST 2.0 algorithms, which are described in Altschul, S. F. et al., “Gapped BLAST and PSLBLAST: a new generation of protein database search programs,” Nucleic Acids Res., Vol. 25, No. 17, pp. 3389-3402, 1977, and Altschul, S. F. et al., “Basic local alignment search tool,” J. Mol. Biol., Vol. 215, No. 3, pp. 403-410, 1990, respectively. Software for performing BLAST analyses is publicly available through the National Center for Biotechnology Information. This algorithm involves first identifying high scoring sequence pairs (HSPs) by identifying short words of length W in the query sequence, which either match or satisfy some positive-valued threshold score T when aligned with a word of the same length in a database sequence. T is referred to as the neighborhood word score threshold (Altschul, S. F. et al., supra). These initial neighborhood word hits act as seeds for initiating searches to find longer HSPs containing them. The word hits are extended in both directions along each sequence for as far as the cumulative alignment score can be increased. Cumulative scores are calculated using, for nucleotide sequences, the parameters M (reward score for a pair of matching residues; always >0) and N (penalty score for mismatching residues; always <0). For amino acid sequences, a scoring matrix is used to calculate the cumulative score. Extension of the word hits in each direction are halted when: the cumulative alignment score falls off by the quantity X from its maximum achieved value; the cumulative score goes to zero or below, due to the accumulation of one or more negative-scoring residue alignments; or the end of either sequence is reached. TheBLAST algorithm parameters W, T, and X determine the sensitivity and speed of the alignment. The BLASTN program (for nucleotide sequences) uses as defaults a word length (W) of 11, an expectation (E) or 10, M=5, N=-4 and a comparison of both strands. For amino acid sequences, the BLASTP program uses as defaults a word length of 3, and expectation (E) of 10, and the BLOSUM62 scoring matrix (see, Henikoff, S. et al., “Amino acid substitution matrices from protein blocks,” Proc. Natl. Acad. Sci. U.S.A., Vol. 89, No. 22, pp. 10915-10919, 1992) alignments (B) of 50, expectation (E) of 10, M=5, N=-4, and a comparison of both strands.

[0100] The BLAST algorithm also performs a statistical analysis of the similarity between two sequences (see, for example, Karlin, S. et al., “Applications and statistics for multiple high-scoring segments in molecular sequences,” Proc. Natl. Acad. Sci. U.S.A., Vol. 90, No. 12, pp. 5873-5787, 1993). One measure of similarity provided by the BLAST algorithm is the smallest sum probability (P(N)), which provides an indication of the probability by which a match between two nucleotide or amino acid sequences would occur by chance. For example, a nucleic acid is considered similar to a reference sequence if the smallest sum probability in a comparison of the test nucleic acid to the reference nucleic acid is less than about 0.2, more preferably less than about 0.01, and most preferably less than about 0.001.

[0101] An indication that two nucleic acid sequences or polypeptides are substantially identical is that the polypeptide encoded by the first nucleic acid is immunologically cross reactive with the antibodies raised against the polypeptide encoded by the second nucleic acid, as described below. Thus, in some embodiments, a polypeptide is typically substantially identical to a second polypeptide, for example, where the two peptides differ only by conservative substitutions. Another indication that two nucleic acid sequences are substantially identical is that the two molecules or their complements hybridize to each other under stringent conditions, as described below. Yet another indication that two nucleic acid sequences are substantially identical is that the same primers can be used to amplify the sequence.Antigen Binding Constructs

[0102] It is herein appreciated that the sequences within the CDR and / or FR can be of special relevance for various antigen binding constructs, such as in a minibody or diabody, e.g., cys-diabody, arrangement.

[0103] Some aspects of the present disclosure relate to an antigen binding construct. In some embodiments, the antigen binding construct (c.g., that binds to DLL3) comprises: a variable light (VL) domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85; and / or a variable heavy (VH) domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82. In some embodiments, the antigen binding construct having the LCDR and HCDR sequences discussed above bind to DLL3.

[0104] In some embodiments, the antigen binding construct comprises a minibody. In some embodiments, a minibody that binds to DLL3 is provided, wherein the minibody comprises: a single-chain variable fragment (scFv) that binds to DLL3. In some embodiments, the scFv comprises a variable light (VL) domain linked to a variable heavy (VH) domain. The VL domain comprises: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; and a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85. In some embodiments, the VH domain comprises: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82. The antigen binding construct and / or minibody further comprises a hinge-extension domain comprising a IgG hinge region, and a IgG CH3 sequence.

[0105] FIG. 1 shows some non-limiting embodiments of polypeptide sequences of antigen binding constructs (e.g. minibodies). (SEQ ID NO: 1-23). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence set forth in any of SEQ ID NO: 20-23 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ ID NO: 20 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ ID NO: 21 (with or without the signal sequence). In some embodiments,the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ ID NO: 22. In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ ID NO: 23 (with or without the signal sequence). In some embodiments, any of the antigen binding construct does not include a signal sequence (e.g., does not include a sequence of SEQ ID NO: 158).

[0106] In some embodiments, the antigen binding construct, cys-diabody, or minibody comprises a CDR that is a CDR in Table 1. In some embodiments, the antigen binding construct (e.g., minibody) includes a CDR that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CDR that is any one of SEQ ID NO: 3-8, 18, and 19. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR1 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR1 in SEQ ID NO: 3 or 18. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR2 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR2 in SEQ ID NO: 4. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR3 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR3 in SEQ ID NO: 5 or 19. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR1 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR1 in SEQ ID NO: 6. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR2 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR2 in SEQ ID NO: 7. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR3 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR3 in SEQ ID NO: 8. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR1 of SEQ ID NO:3 or 18, a HCDR2 of SEQ ID NO:4, and / or a HCDR3 of SEQ ID NO:5, and a VH that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a VH in any one of SEQ ID NOs: 9-13 or 20-23. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR1 of SEQ ID NO:6, a LCDR2 ofSEQ ID N0:7, and / or a LCDR3 of SEQ ID NO:8, and a VL that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a VL in any one of SEQ ID NOs: 14-17 or 20-23. In some embodiments, the antigen binding construct (e.g., minibody) includes any 1, 2, 3, 4, 5, or 6 of the CDR (HCDR and / or LCDR) sequences herein, e.g., as provided in Table 1, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in any one of SEQ ID NOs:20-23 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 1, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in any one of SEQ ID NOs: 20-23 (with or without the signal sequence).TABLE 1

[0107] FIG. 2 shows some non-limiting embodiments of polypeptide sequences of antigen binding constructs (c.g., minibodics). (SEQ ID NO: 24-44). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in any of SEQ ID NO: 33-44 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ ID NO: 33 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ ID NO: 34 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ ID NO:35 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ ID NO: 36 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has at least about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ ID NO: 37 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ ID NO: 38. In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ ID NO: 39 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ ID NO: 40 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ IDNO: 41 (with or without the signal sequence). In some embodiments, the antigen binding construct (c.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ ID NO: 42 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a that is SEQ ID NO: 43 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or 100% sequence identity to a scFv sequence set forth in SEQ ID NO: 44 (with or without the signal sequence).

[0108] In some embodiments, the antigen binding construct, cys-diabody, or minibody comprises a CDR that is a CDR in Table 2. In some embodiments, the antigen binding construct (e.g., minibody) includes a CDR that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CDR that is any one of SEQ ID NO: 26-32. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR1 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR1 in SEQ ID NO: 26. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR2 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR2 in SEQ ID NO: 27. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR3 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR3 in SEQ ID NO: 28. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR1 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR1 in SEQ ID NO: 29. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR2 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR2 in SEQ ID NO: 30. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR3 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR3 in SEQ ID NO: 31 or 32. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR1 of SEQ ID NO:26, a HCDR2 of SEQ ID NO:27, a HCDR3 of SEQ ID NO:28, and a VHthat has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a VH in any one of SEQ ID NOs: 33-44. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR1 of SEQ ID NO:29, a LCDR2 of SEQ ID NO:30, a LCDR3 of SEQ ID NO:31 or 32, and a VL that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a VL in any one of SEQ ID NOs: 33-44. In some embodiments, the antigen binding construct (e.g., minibody) includes any 1, 2, 3, 4, 5, or 6 of the CDR (HCDR and / or LCDR) sequences herein, e.g., as provided in Table 2, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in any one of SEQ ID NOs: 33-44 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 2, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in any one of SEQ ID NOs: 33-44 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 2, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in SEQ ID NO: 33 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 2, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in SEQ ID NO: 34 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 2, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in SEQ ID NO: 35 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 2, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in SEQ ID NO:36 (with or without the signal sequence). In some embodiments, the antigen binding construct (c.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 2, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in SEQ ID NO: 37 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 2, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in SEQ ID NO: 38 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 2, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in SEQ ID NO: 39 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 2, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in SEQ ID NO: 40 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 2, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in SEQ ID NO: 41 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 2, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in SEQ ID NO: 42 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 2, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in SEQ ID NO: 43 (with or without the signal sequence). In someembodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 2, and a seFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in SEQ ID NO: 44 (with or without the signal sequence). In some embodiments, the antigen binding construct does not include a signal sequence (e.g., does not include a sequence of SEQ ID NO: 158).TABLE 2

[0109] FIG. 3 shows some non-limiting embodiments of polypeptide sequences of antigen binding constructs (e.g. minibodies). (SEQ ID NO: 45-56). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a scFv sequence set forth in any of SEQ ID NO: 53-56 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a scFv sequence set forth in SEQ ID NO: 53 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a that is SEQ ID NO: 54 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a that is SEQ ID NO: 55 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a that is SEQ ID NO: 56 (with or without the signal sequence).

[0110] In some embodiments, the antigen binding construct, cys-diabody, or minibody comprises a CDR that is a CDR in Table 3. In some embodiments, the antigen binding construct (e.g., minibody) includes a CDR that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CDR that is any one of SEQ ID NO: 47-52. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR1 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR1 in SEQ ID NO: 47. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR2 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR2 in SEQ ID NO: 48. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR3 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR3 in SEQ ID NO: 49. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR1 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR1 in SEQ ID NO: 50. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR2 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR2 in SEQ ID NO: 51. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR3 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR3 in SEQ ID NO: 52. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR1 of SEQ ID NO:47, a HCDR2 of SEQ ID NO:48, and / or a HCDR3 of SEQ ID NO:49, and a VH that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a VH in any one of SEQ ID NOs: 53-56. In some embodiments, theantigen binding construct (e.g., minibody) includes a LCDR1 of SEQ ID NO:50, a LCDR2 of SEQ ID NO:51, and / or a LCDR3 of SEQ ID NO:52, and a VL that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a VL in any one of SEQ ID NOs: 34-44. In some embodiments, the antigen binding construct (e.g., minibody) includes any 1, 2, 3, 4, 5, or all 6 of the CDR (HCDR and / or LCDR) sequences herein, e.g., as provided in Table 3, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in any one of SEQ ID NOs: 53-56 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes the 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 3, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in any one of SEQ ID NOs: 53-56 (with or without the signal sequence).TABLE 3

[0111] FIG. 4 shows some non-limiting embodiments of polypeptide sequences of antigen binding constructs (e.g. minibodies). (SEQ ID NO: 57-67). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a scFv sequence set forth in any of SEQ ID NO: 66-67 (with or without the signal sequence). In some embodiments,the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a that is SEQ ID NO: 66 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a that is SEQ ID NO: 67 (with or without the signal sequence). In some embodiments, the antigen binding construct does not include a signal sequence (e.g., does not include a sequence of SEQ ID NO: 158).

[0112] In some embodiments, the antigen binding construct, cys-diabody, or minibody comprises a CDR that is a CDR in Table 4. In some embodiments, the antigen binding construct (e.g., minibody) includes a CDR that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CDR that is any one of SEQ ID NO: 59-65. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR1 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR1 in SEQ ID NO: 59. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR2 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR2 in SEQ ID NO: 60. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR3 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR3 in SEQ ID NO: 61 or 62. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR1 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR1 in SEQ ID NO: 63. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR2 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR2 in SEQ ID NO: 64. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR3 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR3 in SEQ ID NO: 65. In some embodiments, the antigen binding construct (e.g., minibody) includes HCDR1 of SEQ ID NO:59, a HCDR2 of SEQ ID NO:60, and / or a HCDR3 of SEQ ID NO:61 or 62, and a VH that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a VH in any one of SEQ ID NOs: 66 or 67. In some embodiments, the antigen binding construct (e.g., minibody) includes LCDR1 of SEQ ID NO:63, a LCDR2 ofSEQ ID NO:64, and / or a LCDR3 of SEQ ID NO:65, and a VL that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a VL in any one of SEQ ID NOs: 66 or 67. In some embodiments, the antigen binding construct (e.g., minibody) includes any 1, 2, 3, 4, 5, or 6 of the CDR (HCDR and / or LCDR) sequences herein, e.g., as provided in Table 4, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in any one of SEQ ID NO: 66 or 67 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 4, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in any one of SEQ ID NO: 66 or 67 (with or without the signal sequence). In some embodiments, the antigen binding construct does not include a signal sequence (e.g., does not include a sequence of SEQ ID NO: 158).TABLE 4

[0113] FIG. 5 shows some non-limiting embodiments of polypeptide sequences of antigen binding constructs (e.g. minibodies). (SEQ ID NO: 68-77). In some embodiments, theantigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a scFv sequence set forth in any of SEQ ID NO: 76-77 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to scFv sequence set forth in SEQ ID NO: 76 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a scFv sequence set forth in SEQ ID NO: 77 (with or without the signal sequence). In some embodiments, the antigen binding construct does not include a signal sequence (e.g., does not include a sequence of SEQ ID NO: 158).

[0114] In some embodiments, the antigen binding construct, cys-diabody, or minibody comprises a CDR that is a CDR in Table 5. In some embodiments, the antigen binding construct (e.g., minibody) includes a CDR that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CDR that is any one of SEQ ID NO: 70-75. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR1 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR1 in SEQ ID NO: 70. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR2 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR2 in SEQ ID NO: 01. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR3 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR3 in SEQ ID NO: 72. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR1 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR1 in SEQ ID NO: 73. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR2 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR2 in SEQ ID NO: 74. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR3 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR3 in SEQ ID NO: 75. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR1of SEQ ID NO:70, a HCDR2 of SEQ ID NO:71 , and / or a HCDR3 of SEQ ID NO:72, and a VH that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a VH in any one of SEQ ID NOs: 76 or 77. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR1 of SEQ ID NO:73, a LCDR2 of SEQ ID NO:74, and / or a LCDR3 of SEQ ID NO:75, and a VL that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a VL in any one of SEQ ID NOs: 76 or 77. In some embodiments, the antigen binding construct (e.g., minibody) includes any 1, 2, 3, 4, 5, or all 6 of the CDR (HCDR and / or LCDR) sequences herein, e.g., as provided in Table 5, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in any one of SEQ ID NO: 76 or 77 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes the 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 5, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in any one of SEQ ID NO: 76 or 77 (with or without the signal sequence). In some embodiments, the antigen binding construct does not include a signal sequence (e.g., does not include a sequence of SEQ ID NO: 158).TABLE 5

[0115] FIG. 6 shows some non-limiting embodiments of polypeptide sequences of antigen binding constructs (c.g. minibodics). (SEQ ID NOs: 78-87). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a scFv sequence set forth in any of SEQ ID NO: 86-87 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a scFv sequence set forth in SEQ ID NO: 86 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a scFv sequence set forth in SEQ ID NO: 87 (with or without the signal sequence). In some embodiments, the antigen binding construct does not include a signal sequence (e.g., does not include a sequence of SEQ ID NO: 158).

[0116] In some embodiments, the antigen binding construct, cys-diabody, or minibody comprises a CDR that is a CDR in Table 6. In some embodiments, the antigen binding construct (e.g., minibody) includes a CDR that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CDR that is any one of SEQ ID NO: 80-85. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR1 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR1 in SEQ ID NO: 80. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR2 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR2 in SEQ ID NO: 81. In some embodiments, the antigen binding construct (e.g., minibody) includes a HCDR3 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a HCDR3 in SEQ ID NO: 82. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR1 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR1 in SEQ ID NO: 83. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR2 that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR2 in SEQ ID NO: 84. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR3 that has, has at least, or has about 70%, 75%,80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a LCDR3 in SEQ ID NO: 85. In some embodiments, the antigen binding construct (c.g., minibody) includes a HCDR1 of SEQ ID NO:80, a HCDR2 of SEQ ID NO:81, and / or a HCDR3 of SEQ ID NO:82, and a VH that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a VH in any one of SEQ ID NOs: 86 or 87. In some embodiments, the antigen binding construct (e.g., minibody) includes a LCDR1 of SEQ ID NO:83, a LCDR2 of SEQ ID NO:84, and / or a LCDR3 of SEQ ID NO:85, and a VL that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a VL in any one of SEQ ID NO: 86 or 87. In some embodiments, the antigen binding construct (e.g., minibody) includes any 1, 2, 3, 4, 5, or all 6 of the CDR (HCDR and / or LCDR) sequences herein, e.g., as provided in Table 6, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in any one of SEQ ID NOs: 86 or 87 (with or without the signal sequence). In some embodiments, the antigen binding construct (e.g., minibody) includes any combination of 6 CDR (HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3) sequences provided in Table 6, and a scFv sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a scFv sequence in any one of SEQ ID NO: 86 or 87 (with or without the signal sequence). In some embodiments, the antigen binding construct does not include a signal sequence (e.g., does not include a sequence of SEQ ID NO: 158).TABLE 6

[0117] FIG. 17 shows embodiments of a polypeptide sequence of human-DLL3. (SEQ ID NO: 88). The signal sequence is underlined, and a transmembrane domain is shown in bolded italics, in Fig. 17. In some embodiments, the antigen binding construct or minibody, binds to a protein having an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a DLL3 that is SEQ ID NO: 88 (with or without the signal sequence). In some embodiments, the antigen binding construct, minibody, and / or cys-diabody, binds to a protein having an amino acid sequence of SEQ ID NO: 88, without the signal sequence.

[0118] In some embodiments, the antigen binding construct (e.g., minibody) includes a scFv that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of the scFv sequences set forth in Table 11 (without or without the signal sequence). FIG. 18 shows some non-limiting embodiments of polypeptide sequences of minibodies (SEQ ID NO: 1 10-135). In some embodiments, the minibody has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to any of SEQ ID NO: 110-135 (with or without the signal sequence). Provided herein is a minibody that includes any one of the sequences provided in Table 12 (with or without the signal sequence, which are underlined in each sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 110 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 110 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 110, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 110 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 111 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a SEQ IDNO: 11 1 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 111, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 111 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 112 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 112 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 112, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 112 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 113 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 113 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 113, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 113 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 114 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 114 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 114, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 114 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 115 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 115 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 115, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 115 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 116 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 116 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 116, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 116 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 117 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 117 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 117, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 117 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 118 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 118 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 118, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 118 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 119 (with or without the signal sequence). In someembodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 119 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 119, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 119 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 120 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 120 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 120, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 120 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 121 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 121 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 121, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 121 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 122 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 122 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 122, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 122 (with or without the signal sequence). Also provided is a minibody that includesan amino acid sequence of SEQ ID NO: 123 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 123 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 123, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 123 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 124 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 124 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 124, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 124 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 125 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 125 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 125, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 125 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 126 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 126 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 126, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity toSEQ ID NO: 126 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 127 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 127 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 127, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 127 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 128 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 128 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 128, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 128 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 129 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 129 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 129, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 129 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 130 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 130 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 130, and an amino acid sequence that has, has at least, or hasabout 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 130 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 131 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 131 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 131, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 131 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 132 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 132 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 132, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 132 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 133 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 133 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 133, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 133 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 134 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 134 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1,HCDR2, HCDR3 in SEQ TD NO: 134, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 134 (with or without the signal sequence). Also provided is a minibody that includes an amino acid sequence of SEQ ID NO: 135 (with or without the signal sequence). In some embodiments, the minibody includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 135 (with or without the signal sequence). In some embodiments, the minibody includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 135, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 135 (with or without the signal sequence). In some embodiments, the minibody does not include a signal sequence (e.g., does not include a sequence of SEQ ID NO: 158).

[0119] In some embodiments, a minibody that binds to DLL3 is provided, wherein the minibody comprises amino acid sequence of any one of SEQ ID NO: 110-135 (with or without the signal sequence). In some embodiments, a minibody that binds to DLL3 is provided, wherein the minibody comprises amino acid sequence of any one of SEQ ID NO: 114-125 (with or without the signal sequence). In some embodiments, a minibody that binds to DLL3 is provided, wherein the minibody has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to any of SEQ ID NO: 110-135 (with or without the signal sequence). In some embodiments, a minibody that binds to DLL3 is provided, wherein the minibody has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to any of SEQ ID NO: 114-125 (with or without the signal sequence). In some embodiments, a minibody that binds to DLL3 is provided, wherein the minibody has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to any one of the sequences provided in Table 12 (with or without the signal sequence, which are underlined in each sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 110 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 110 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3of the LCDR 1 , LCDR2, LCDR3, HCDR1 , HCDR2, HCDR3 in SEQ TD NO: 110, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 110 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 111 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a SEQ ID NO: 111 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 111, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 111 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 112 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 112 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 112, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 112 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 113 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 113 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 113, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 113 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 114 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 114 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 114, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 114 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 115 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 115 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 115, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 115 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 116 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 116 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 116, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 116 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 117 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 117 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 117, and an amino acid sequence that has, has at least, or has about 70%,75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 117 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 118 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 118 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 118, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 118 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 119 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 119 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 119, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 119 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 120 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 120 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 120, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 120 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 121 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or moresequence identity to SEQ ID NO: 121 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 121, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 121 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 122 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 122 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 122, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 122 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 123 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 123 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 123, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 123 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 124 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 124 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 124, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 124 (with or without the signalsequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 125 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 125 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 125, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 125 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 126 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 126 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 126, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 126 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 127 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 127 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 127, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 127 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 128 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 128 (with or without the signal sequence). In some embodiments, the minibody thatbinds to DLL3 includes an LCDR1 , LCDR2, LCDR3, HCDR1 , HCDR2, HCDR3 of the LCDR1 , LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 128, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 128 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 129 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 129 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 129, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 129 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 130 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 130 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 130, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 130 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 131 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 131 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 131, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 131 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 132 (withor without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 132 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 132, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 132 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 133 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 133 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 133, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 133 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 134 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 134 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 in SEQ ID NO: 134, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 134 (with or without the signal sequence). Also provided is a minibody that binds to DLL3 and that includes an amino acid sequence of SEQ ID NO: 135 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to SEQ ID NO: 135 (with or without the signal sequence). In some embodiments, the minibody that binds to DLL3 includes an LCDR1, LCDR2, LCDR3, HCDR1, HCDR2, HCDR3 of the LCDR1, LCDR2, LCDR3, HCDR1, HCDR2,HCDR3 in SEQ ID NO: 135, and an amino acid sequence that has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%, or more, sequence identity to SEQ ID NO: 135 (with or without the signal sequence). In some embodiments, the minibody does not include a signal sequence (e.g., does not include a sequence of SEQ ID NO: 158).

[0120] In some embodiments, the antigen binding construct, minibody, and / or cys- diabody, includes a VH domain that comprises an amino acid sequence having at least 90% identity to a VH domain in any one of SEQ ID NO: 1, 9, 10, 11, 12 or 13, and wherein the antigen binding construct or minibody, comprises a T25S, Y27G, R28T and / or C95S mutation as numbered according to the numbering in SEQ ID NO: 1 (Kabat). In some embodiments, the VH domain comprises an amino acid sequence having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identity to a VH domain in any one of SEQ ID NO: 1, 9, 10, 11, 12 or 13, and wherein the antigen binding construct or minibody, comprises a T25S, Y27G, R28T and / or C95S mutation as numbered according to the numbering in SEQ ID NO: 1 (Kabat).

[0121] In some embodiments, the antigen binding construct, minibody, and / or cys- diabody, includes a VL domain that comprises an amino acid sequence having at least 90% identity to a VL domain of SEQ ID NO: 25, and wherein the antigen binding construct or minibody, comprises a D93N mutation (Kabat). In some embodiments, the VL domain comprises an amino acid sequence having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identity to a VL domain of SEQ ID NO: 25, and wherein the antigen binding construct or minibody, comprises a D93N mutation (Kabat).

[0122] In some embodiments, the antigen binding construct, minibody, and / or cys- diabody, includes a VH domain that comprises an amino acid sequence having at least 90% identity to a VH domain of SEQ ID NO: 57, and wherein the antigen binding construct or minibody, comprises a K94R mutation (Kabat). In some embodiments, the VH domain comprises an amino acid sequence having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identity to a VH domain of SEQ ID NO: 57, and wherein the antigen binding construct or minibody, comprises a K94R mutation (Kabat).

[0123] In some embodiments, the antigen binding construct, minibody, or cys-diabody, comprises a FR that is a FR in Table 7. In some embodiments, the FR has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a FR that is any of SEQ ID NO: 136-138. In some embodiments, the FR has, has at least, or has about 70%,75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a FR that is SEQ ID NO: 136. In some embodiments, the FR has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a FR that is SEQ ID NO: 137. In some embodiments, the FR has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a FR that is SEQ ID NO: 138. In some embodiments, the FR has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a FR that is SEQ ID NO: 139. In some embodiments, the FR has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a FR that is SEQ ID NO: 140. In some embodiments, the FR has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a FR that is SEQ ID NO: 141.TABLE 7

[0124] In some embodiments, the antigen binding construct or minibody has a disrupted cluster of surface-exposed, positively charged amino acids, and has enhanced biodistribution and / or pharmacokinetics compared to an original construct having an original cluster of surface-exposed, positively charged amino acids and from which the construct having the disrupted cluster is derived (e.g., solely by disrupting the original cluster in the original antibody, while other sequence-based features can otherwise remain the same). In some embodiments, the antigen binding construct or minibody has reduced kidney uptake when administered to a subject, compared to the original construct having the intact cluster of positively charged amino acids. In some embodiments, the antigen binding construct has a molecular weightof 15-160 kDa. In some embodiments, the antigen binding construct has a molecular weight of about 50-80 kDa. In some embodiments, the change in biodistribution due to disruption of the cluster is readily observed for an antigen binding construct having a molecular weight (as a dimer) of -50-80 kDa, such as a minibody or a cys-diabody. In general, modification of the original antigen binding construct by disrupting the cluster of positively charged amino acids at least maintains the same binding specificity and binding affinity of the original antigen binding construct, while enhancing the biodistribution and / or pharmacokinetics.

[0125] In some embodiments, the antigen binding construct or minibody is a variant that includes at least one disrupted cluster of surface-exposed positively charged amino acids, the original cluster having at least two (e.g., 2, 3, 4, 5, 6 or more) surface-exposed, positively charged amino acids within about 30 angstroms of each other, where the variant varies from an original antigen binding construct that includes the original cluster by having a substitution of at least one of the surface-exposed, positively charged amino acids of the original cluster with one or more negatively charged or non-charged amino acid, whereby the original positive cluster is disrupted (compared to the original). In some embodiments, the original cluster has at least two (e.g., 2, 3, 4, 5, 6 or more) surface-exposed, positively charged amino acids within, or within about 30, 25, 20, 15, 10, 8, or 5 angstroms, or a distance in a range defined by any two of the preceding values (e.g., 5-30 angstroms, 5-25 angstroms, 5-15 angstroms, 10-20 angstroms, etc.) of each other. In some embodiments, the variant antigen binding construct exhibits reduced kidney uptake (e.g., when the variant antigen binding construct is radiolabeled and administered to a subject) when compared to the original antigen binding construct.

[0126] In some embodiments, the antigen binding construct, minibody, or cys-diabody includes at least one disrupted cluster of surface-exposed positively charged amino acids, the original cluster having at least two (e.g., 2, 3, 4, 5, 6 or more) surface-exposed, positively charged amino acids within about 30 angstroms of each other, where the variant varies from the original binding construct that includes the original cluster by having a substitution of at least one of the surface-exposed, positively charged amino acids of the original cluster with one or more negatively charged or non-charged amino acid, whereby the positive cluster is disrupted (compared to the binding construct). In some embodiments, the antigen binding construct, minibody, or cys- diabody includes a VL having a variant framework region 2 (FR2) that has been modified from an original construct that includes the original sequence X1X2X3X4X5X6X7 (SEQ ID NO: 142), whereXi is a positively charged amino acid (e.g., a lysine or arginine), where X2, X3, X5, and Xe are each independently any negatively charged or a non-chargcd amino acid, and where X4 and X7 arc each independently any amino acid with the proviso that at least one is a positively charged amino acid, where the sequence is outside of any CDR of the antigen binding construct, and where the at least one of X4 and X7 that is a positively charged amino acid is surface exposed and is part of the original cluster. In some embodiments, Xi is part of the original cluster. In some embodiments, Xi and the at least one of X4 and X7 that is a positively charged amino acid are part of the original cluster. In some embodiments, all of the positively charged amino acids of the original sequence are part of the original cluster. In some embodiments, X2, X3, X5, and Xe are each independently any non-charged amino acid. The antigen binding construct, e.g., variant antigen binding construct, can include the original sequence of X1X2X3X4X5X6X7 (SEQ ID NO: 142) with the substitution of the at least one of the surface-exposed positively charged amino acids of the cluster with a negatively charged or non-charged amino acid that disrupts the original cluster. In some embodiments, the negatively charged or non-charged amino acid with which the at least one of the surface-exposed, positively charged amino acids of the original cluster is substituted is a glutamine (e.g., a K to Q, or R to Q substitution). In some embodiments, the framework region 2 (FR2) of the original antigen binding construct includes at least one of the following original sequences: KX2X3KX5 XeK (SEQ ID NO: 143), where X2, X3, X5, and X6 are each independently any negatively charged or a non-charged amino acid; KX2X3X4X5 X<>R (SEQ ID NO: 144), where X2, X3, X4, X5, and Xe are each independently any negatively charged or a non-charged amino acid; or KX2X3X4X5 X(>K (SEQ ID NO: 145), where X2, X3, X4, X5, and X& are each independently any negatively charged or a non-charged amino acid. In some embodiments, the framework region 2 (FR2) of the original antigen binding construct includes at least one of the following sequences: KPGKAPK (SEQ ID NO: 146), KPGQAPR (SEQ ID NO: 147), KPEKAPK (SEQ ID NO: 148), KPGKVPK (SEQ ID NO: 149), KPGQPPR (SEQ ID NO: 150), KPGQSPR (SEQ ID NO: 151), KPGLAPR (SEQ ID NO: 152), or KPGQPPK (SEQ ID NO: 153), corresponding to X1X2X3X4X5X6X7 (SEQ ID NO: 142). In some embodiments, the original sequence is KPGKAPK (SEQ ID NO: 146) or KPGQAPR (SEQ ID NO: 147), corresponding to X1X2X3X4X5X6X7 (SEQ ID NO: 142). In some embodiments, the antigen binding construct, minibody, or cys-diabody includes at least one of KPGQAPR (SEQ ID NO: 147), KPGQAPK (SEQ ID NO: 154, KPGQAPQ(SEQ ID NO: 155), KPGQSPQ (SEQ ID NO: 156), and QQKPGQSPQ (SEQ ID NO: 157), e.g., in the VLFR2.

[0127] In some embodiments, the antigen binding construct or minibody, further comprises a signal peptide that is a signal peptide in SEQ ID NO: 158. As used herein, “signal peptide” and “signal sequence” are used interchangeably, unless indicated otherwise.

[0128] In some embodiments, the antigen binding construct or minibody comprises a linker (e.g., a peptide linker that links a VL domain and a Vn domain of the antigen binding construct) that is any of SEQ ID NO: 159-164. In some embodiments, the antigen binding construct, minibody, or cys-diabody, comprise a linker that is a linker in Table 8.TABLE 8

[0129] Table 9 shows some non-limiting embodiments of a hinge sequence of the antigen binding construct (e.g., minibody, scFv-Fc, nanobody®-Fc) of the present disclosure. In some embodiments, the antigen binding construct (e.g., minibody, scFv-Fc, nanobody®-Fc) includes a hinge region having any one of the sequences as set forth in Table 9. In some embodiments, the antigen binding construct (e.g., minibody, scFv-Fc, nanobody®-Fc) includes a hinge region having an upper hinge, core hinge, and a lower hinge including the sequence of any one of the upper hinge, core hinge, and a lower hinge, respectively, as set forth in Table 9. In some embodiments, the antigen binding construct (e.g., minibody, scFv-Fc, nanobody®-Fc) includes a hinge region having a sequence of any one of the full hinge sequences set forth in Table 9. In some embodiments, the antigen binding construct includes an upper hinge having the sequence EPKSSDKTHT (SEQ ID NO: 165). In some embodiments, the antigen binding construct includes an upper hinge having the sequence EPGSSDGTHT (SEQ ID NO: 166). In some embodiments,the antigen binding construct includes a core hinge having the sequence CPPCPPC (SEQ ID NO: 167). In some embodiments, the antigen binding construct includes a core hinge having the sequence CPPCP (SEQ ID NO: 168). In some embodiments, the antigen binding construct includes a lower hinge having at least one of the following sequences: APELLGGP (SEQ ID NO: 169), GGGSSGGGSG (SEQ ID NO: 170), and APPVAGP (SEQ ID NO: 171).Table 9

[0130] Some non-limiting embodiments of a CH3 polypeptide sequence arc shown in SEQ ID NO: 202-222.

[0131] In some embodiments, the antigen binding construct or minibody comprises a CH3 domain that is a CH3 domain in Table 9. In some embodiments, the CH3 domain is an IgG CH3 domain. In some embodiments, the IgG CH3 domain is an IgGl, IgG2, IgG3, and / or IgG 4 CH3 domain. In some embodiments, the CH3 domain comprises a germline CH3 domain. In some embodiments, the CH3 domain comprises one or more allotypes. In some embodiments, the IgGl CH3 domain is any of SEQ ID Nos. 202-205. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequenceidentity to a CH3 domain that is any of SEQ TD NO: 202-205. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 202. In some embodiments, the hinge region has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 203. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 204. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 205. In some embodiments, the CH3 domain is an IgG2 CH3 domain. In some embodiments, the IgG2 CH3 domain is any of SEQ ID Nos. 206-208. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is any of SEQ ID NO: 206-208. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 206. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 207. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 208. In some embodiments, the hinge region is an IgG3 CH3 domain. In some embodiments, the IgG3 CH3 domain is any of SEQ ID Nos. 209-219. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is any of SEQ ID NO: 209-219. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 209. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 210. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 211. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 212. In some embodiments, the CH3 domain has, has at least, orhas about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 213. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 214. In some embodiments, the CH3 domain has at least about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 215. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 216. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 217. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 218. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 219. In some embodiments, the CH3 domain is an IgG2 CH3 domain. In some embodiments, the IgG2 CH3 domain is any of SEQ ID Nos. 220-222. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is any of SEQ ID NO: 220-222. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 220. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 221. In some embodiments, the CH3 domain has, has at least, or has about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a CH3 domain that is SEQ ID NO: 222.TABLE 10

[0132] In some embodiments, the antigen binding construct includes a Fc region (e.g., a scFv-Fc, a nanobody®-Fc). In some embodiments, the antigen binding construct includes an amino acid sequence identical to the amino acid sequence of a native or naturally occurring Fc region (e.g., a human IgGl Fc region). In some embodiments, the Fc region includes an amino acid sequence of SEQ ID NO: 202, as set forth below.THTCPPCPAPELLGGP SVFLFPPKPKDTLMISRTPEVTCVWDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNS TYRVVSVLTVLHQDWLNGKE YKCKVSNKALPAP I EKTI SKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYP SD IAVEWE SNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHE4 40IALHNHYTQKSLSLSPGK ( SEQ I D NO : 2 02 )

[0133] In some embodiments, the Fc region includes an amino acid sequence at least 70, 80, 90, 95, 96, 97, 98, 99, or about 100% identical or identical by a percentage in a range defined by any two of the preceding values (e.g., 80-100%, 85-97%, 85-95%, 90-100%, etc.), to SEQ ID NO: 202. In some embodiments, the Fc region includes one or more (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more) mutations (e.g., substitutions) that changes (e.g., increase or reduce) an effector function (e.g., FcyR binding) and / or binding to the Fc neonatal receptor (FcRn). In some embodiments, the Fc region includes an amino acid sequence of SEQ ID NO: 202, with one or more (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more) mutations (e.g., substitutions) that changes (e.g.,increase or reduce) an effector function (e.g., FcyR binding) and / or binding to the Fc neonatal receptor (FcRn). In some embodiments, the Fc region includes one or more (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more) mutations (e.g., substitutions) that reduces an effector function (e.g., FcyR binding) and / or binding to the Fc neonatal receptor (FcRn). In some embodiments, the Fc region includes an amino acid sequence of SEQ ID NO: 202, with one or more (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more) mutations (e.g., substitutions) that reduces an effector function (e.g., FcyR binding) and / or binding to the Fc neonatal receptor (FcRn). In some embodiments, the one or more mutations that reduce FcRn binding is a mutation (e.g., substitution) of any one or more (e.g., one, two or all three) of 1253, H310, and H435 (EU numbering). In some embodiments, the one or more mutations that reduce binding to the FcRn is any one or more (e.g., one, two or all three) of I253A, H310A, and H435A (EU numbering). In some embodiments, the Fc region includes one or more (e.g., one, two or all three) of I253A, H310A, and H435A (EU numbering). In some embodiments, the one or more mutations that reduces binding to the FcyR is a mutation (e.g., substitution) of N297 (EU numbering). In some embodiments, the one or more mutations that reduce binding to the Fc neonatal receptor is N297Q, N297A or N297G (EU numbering). In some embodiments, the Fc region includes N297Q (EU numbering). In some embodiments, the one or more mutations that reduces Fc effector function is a mutation (e.g., substitution) of any one or more of: L234, L235, G236, G237, P238, H268, K322, L328, P329, A330, P331. In some embodiments, the one or more mutations that reduces Fc effector function is any one or more of: L234A, L235A, G236R, G237A, P238S, H268A, K322A, L328R, P329G, A330S, P331S. Further non-limiting examples of known mutations that change Fc effector function may be found in Wilkinson and Hale (2022) Systematic analysis of the varied designs of 819 therapeutic antibodies and Fc fusion proteins assigned international nonproprietary names. MAbs. 2022 Jan- Dec;14(l):2123299. doi: 10.1080 / 19420862.2022.2123299. In some embodiments, the Fc region does not include a C-terminal lysine.

[0134] In some embodiments, the antigen binding construct is an scFv-Fc. In some embodiments, the scFv-Fc includes any one of the scFv that binds to DLL3, e.g., having a variable light (VL) domain linked to the variable heavy (VH) domain as described herein, a hinge domain, and an Fc region. In some embodiments, the scFv-Fc includes any one of the scFv that binds to DLL3, e.g., having a variable light (VL) domain linked to the variable heavy (VH) domain as described herein, linked to an Fc region via a hinge domain, as described herein. In someembodiments, the hinge domain is any suitable hinge domain as described herein (e.g., Table 9). In some embodiments, the antigen binding construct is a nanobody ®-Fc (or a single domain fragment fused to an Fc region). In some embodiments, the nanobody®-Fc includes a variable domain (VHH) having any one or more of the HCDR1, HCDR2 and HCDR3 sequences, as described herein. In some embodiments, the nanobody®-Fc includes a variable domain (VHH) having a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82. In some embodiments, the nanobody®-Fc includes a VH domain having any one or more (e.g., any 1, 2 or all 3) of the HCDR1, HCDR2 and HCDR3 sequences as described herein linked to a Fc region via a hinge domain, as described herein. In some embodiments, the nanobody®-Fc includes a variable domain (VHH) having a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82, where the HCDR1, HCDR2, and HCDR3 sequences are combined according to the arrangement of the HCDRs in any one of FIGs. 1-6. In some embodiments, the nanobody®-Fc includes a VH domain having the HCDR1, HCDR2 and HCDR3 sequences in the arrangement as shown in any one of FIGs. 1-6, linked to a Fc region via a hinge domain.

[0135] In some embodiments, the antigen binding construct includes at least one modification. Exemplary modifications include, but are not limited to, antigen binding constructs that have been modified by glycosylation, acetylation, pegylation, phosphorylation, amidation, derivatization by known protecting / blocking groups, conjugation to metal chelator, fluorescence or infrared dye, or conjugation to a toxin, proteolytic cleavage, and linkage to a cellular ligand or other protein. Any of numerous chemical modifications may be carried out by known techniques, including, but not limited to, amine coupling to amine containing amino acids, cystine coupling, specific chemical cleavage, acetylation, and metabolic synthesis of tunicamycin. In some embodiments, the derivative can contain one or more non-natural amino acids.

[0136] In some embodiments, the antigen binding construct is conjugated to another substance to form an anti-target conjugate. The conjugates described herein can be prepared by known methods of linking antigen binding constructs with lipids, carbohydrates, protein or other atoms and molecules. In some embodiments, the conjugate is formed by site-specific conjugation using a suitable linkage or bond. Site-specific conjugation is more likely to preserve the bindingactivity of an antigen binding construct. The substance may be conjugated or attached at the hinge region of a reduced antigen binding construct via thiocthcr bond formation. In some embodiments, tyrosine conjugation can be employed. Other linkages or bonds used to form the conjugate can include, but are not limited to, a covalent bond, a non-covalent bond, a disulfide linkage, a hydrazone linkage, an ester linkage, an amido linkage, and amino linkage, an imino linkage, a thiosemicarbazone linkage, a semicarbazone linkage, an oxime linkage and a carbon-carbon linkage. In some embodiments, no cysteine or other linking aspect, need be included in the antigen binding construct.

[0137] In some embodiments, the antigen binding construct or minibody is conjugated to a chemotherapeutic agent. Chemotherapeutic agents are often cytotoxic or cytostatic in nature and may include alkylating agents, antimetabolites, anti-tumor antibiotics, topoisomerase inhibitors, mitotic inhibitors hormone therapy, targeted therapeutics and immunotherapeutic s. In some embodiments the chemotherapeutic agents that may be used as detectable markers in accordance with the embodiments of the disclosure are selected from among those chemotherapeutic agents defined elsewhere herein.

[0138] In some embodiments, the antigen binding construct or minibody is conjugated to a toxin. Toxins that may be used in accordance with the embodiments of the disclosure include, but are not limited to, Auristatin E, Auristatin F, Dolastatin 10, Dolastatin 15, combretastatin and their analogs, maytansinoid, calicheamicin, alpha-amanitin, pyrrolobenzodiazepine dimers, epothilones, duocarmycin and their analogs, tubulysin D, basillistatins, ricin, abrin, ribonuclease (RNase), DNase I, Staphylococcal enterotoxin-A, pokeweed antiviral protein, gelonin, diphtheria toxin, Pseudomonas exotoxin, and Pseudomonas endotoxin.

[0139] In some embodiments, the antigen binding construct or minibody is conjugated to a radioisotope. In some embodiments, the radioisotope comprises a beta-emitter or alphaemitter, such as, Iodine-131, Yttrium-90, Copper-67, Terbium-149, Terbium-161, Lutetium-177, Astatine-211 , Lead-212, Bismuth-212, Actinium-225, Bismuth-213, or 227-Thorium, a positron emitter such as Zirconium-89, Copper-64, Gallium-68, Fluorine- 18, Indium- 111, Iodine- 124. In some embodiments, the radiolabel comprises Terbium-149, Terbium-161, or Lead-212. In some embodiments, the antigen binding construct or minibody, are conjugated to a gamma emitter. In some embodiments the radioisotope comprises a auger radiation emitter.16

[0204] In some embodiments, the antigen binding construct or minibody is conjugated to a radioisotope, a fluorescent compound, a biolumincsccnt compound, chemiluminescent compound, a metal chelator or an enzyme. In some embodiments, the at least one payload is comprises18F,18F-FAC,32P,33P,45Ti,47Sc,52Fe,59Fe,62Cu,MCLI,67CU,67Ga,68Ga,75Sc,77As,86Y,90Y,89Sr,89Zr,94Tc,94Tc, "mTc, "Mo,105Pd,105Rh,l uAg,niIn,123I,124I,125I,131I,142Pr,143Pr,149Pm,149Tb,153Sm,154’158Gd,161Tb,166Dy,166Ho,169Er,175Lu,177Lu,186Re,188Re,189Re,194Ir,198AU,199AU,21'At,21'Pb,212Bi,212Pb,213Bi,223Ra,227Th and225Ac, or any combination thereof. In some embodiments, the at least one payload comprises149Tb,161Tb, or212Pb.

[0140] In some embodiments, the antigen binding construct is an antibody (-140-170 kDa), a multi- specific antibody (-100 kDa and greater), a single-arm or one-arm antibody (-110 kDa and less), a modified antibody, or the like. In some embodiments, the antigen binding construct or minibody, binds specifically to DLL3. In some embodiments, the antigen binding construct or minibody, is bispecific. In some embodiments, the antigen binding construct or minibody, is bivalent. In some embodiments, the antigen binding construct or minibody comprises a monovalent scFv. In some embodiments, the antigen binding construct is a scFv-Fc (e.g., a scFv fused to a Fc). In some embodiments, the antigen binding construct is a nanobody®-Fc (e.g., a nanobody® (or single domain fragment) fused to a Fc).

[0141] In some embodiments, the order of the variable domains, from N terminus to C terminus of the antigen binding construct or minibody, from N terminus to C terminus of the polypeptide is VL, VH. In some embodiments, the order of the variable domains, from N terminus to C terminus of the polypeptide is VH, VL.

[0142] In some embodiments, the antigen binding construct or minibody is a humanized antigen binding construct or minibody. In some embodiments, the antigen binding constructs or minibodies of any of FIG. 1-6 can be reformatted from an antigen binding construct or minibody, to a different format. For example, the minibodies presented in any one of FIG. 1-6 may be reformatted to antigen binding constructs. For example, the minibodies presented in FIG. 1-6 can be reformatted to scFv-Fc.

[0143] In some embodiments, a minibody that binds to DLL3 includes: a single-chain variable fragment (scFv) that binds to DLL3, the scFv comprising a variable light (VL) domain linked to a variable heavy (VH) domain, the VL domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74,or 84; and a LCDR3 that is any one of SEQ ID NO: 8, 31 , 32, 52, 65, 75, or 85 and variable heavy (VH) domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82; a hinge region; a IgG CH3 sequence; and a therapeutic agent, toxic payload, and / or a detectable marker.

[0144] In some embodiments, a scFv-Fc that binds to DLL3 includes: a single-chain variable fragment (scFv) that binds to DLL3, the scFv comprising a variable light (VL) domain linked to a variable heavy (VH) domain, the VL domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; and a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85 and variable heavy (VH) domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82; a hinge region; a IgG CH3 sequence; and a therapeutic agent, toxic payload, and / or a detectable marker.

[0145] In some embodiments, a humanized antigen binding construct or minibody comprises: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; and a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85 and variable heavy (VH) domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82.

[0146] In some embodiments, the VL domain comprises, or further comprises a LFR2 of a LFR2 of SEQ ID NO: 137 or 138.Properties

[0147] In some embodiments, expression yield of the antigen binding construct, or minibody is determined using ultraviolet-visible spectroscopy (UV-Vis or UV / Vis). In some embodiments, expression yield of the antigen binding construct, or minibody is determined using chromatographic techniques. In some embodiments, expression of the antigen binding construct, or minibody is determined using biolayer interferometry. In some embodiments, the expression yield of the antigen binding construct, or minibody is, is about, or is at least 1, 5, 10, 15, 20, 25, 30, 40, 50, 60, 70, 75, 80, 90, 100, 110, 120, 125, 150, 175, 200, 250, 300, 350, 400, 450, or 500mg / L, or a yield in a range that is defined by any two of the preceding values. For example, in some embodiments, the expression yield of the antigen binding construct, or minibody, is between about 1 and 500 mg / L, 1 and 350 mg / L, 1 and 200 mg / L, 1 and 100 mg / L, 1 and 50 mg / L, 1 and 25 mg / L, 5 and 500 mg / L, 5 and 350 mg / L, 5 and 200 mg / L, 5 and 100 mg / L, 5 and 50 mg / L, 5 and 25 mg / L, 25 and 500 mg / L, 25 and 350 mg / L, 25 and 20 mg / L, 25 and 100 mg / L, or 25 and 50 mg / L. In some embodiments, the expression yield of the antigen binding construct, or minibody is determined with respect to the expression yield of the parental antigen binding construct, or minibody. For example, in some embodiments, the expression yield of the antigen binding construct, or minibody is about 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10-fold higher than the expression yield of the parental antigen binding construct, or minibody, or is increased by a range that is defined by any two of the preceding values. For example, in some embodiments, the expression yield of the antigen binding construct, or minibody, is between 1 and 10-fold, 1 and 8-fold, 1 and 5-fold, 1 and 3-fold, 3 and 10-fold, 3 and 8-fold, 3 and 5-fold, 5 and 10-fold, or 5 and 8-fold higher than the expression yield of the parental antigen binding construct, or minibody.

[0148] In some embodiments, the antigen binding construct, or minibody, accumulates to a detectable level in a subject’s blood, liver, kidney, spleen, lungs, muscle, bone, heart, stomach, small intestine, large intestine, pancreas, tumor, or any combination therein. In some embodiments, the antigen binding construct is biased for distribution to a subject’s blood, liver, kidney, spleen, lungs, muscle, bone, heart, stomach, small intestine, large intestine, pancreas, tumor, or any combination therein.

[0149] In some embodiments, the antigen binding construct, or minibody is detectable at, at about, up to, or up to about 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, or 35% ID / g (% injected dose per gram), or a percentage in a range that is defined by any two of the preceding values. For example, in some embodiments, the antigen binding construct, or minibody, is detectable at between about 0.1% and 35%, 0.1% and 30%, 1% and 35%, 1% and 30%, 5% and 35%, or 5% and 30% ID / g.

[0150] In some embodiments, the antigen binding construct, or minibody are distributed to the blood, liver, kidney, spleen, lungs, muscles, bones, heart, stomach, small intestine, large intestine, pancreas, tumor, or any combination therein. In some embodiments, the antigen binding construct, or minibody are distributed to the blood, liver, kidney, spleen, lungs, muscles, bones, heart, stomach, small intestine, large intestine, pancreas, tumor, or anycombination therein, at, at least or at about 1 %, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 90%, 95%, or 100%, ID / g, or a percentage in a range that is defined by any two of the preceding values. For example, in some embodiments, the antigen binding construct, or minibody are distributed to the blood, liver, kidney, spleen, lungs, muscles, bones, heart, stomach, small intestine, large intestine, pancreas, tumor, or any combination therein at an ID / g of between about 1% and 100%, 1% and 75%, 1% and 50%, 1% and 30%, 1% and 25%, 5% and 100%, 5% and 75%, 5% and 50%, 5% and 30%, 5% and 25%, 10% and 100%, 10% and 75%, 10% and 50%, 10% and 30%, or 10% and 25%.

[0151] In some embodiments, the antigen binding construct, or minibody are distributed to the blood, liver, kidney, spleen, lungs, muscles, bones, heart, stomach, small intestine, large intestine, pancreas, tumor, or any combination therein. In some embodiments, the antigen binding construct, or minibody are distributed to the blood, liver, kidney, spleen, lungs, muscles, bones, heart, stomach, small intestine, large intestine, pancreas, tumor, or any combination therein, at, at least or at about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 90%, 95%, or 100%, ID / g, or a percentage in a range that is defined by any two of the preceding values. For example, in some embodiments, the antigen binding construct, or minibody are distributed to the blood, liver, kidney, spleen, lungs, muscles, bones, heart, stomach, small intestine, large intestine, pancreas, tumor, or any combination therein at an ID / g of between about 1% and 100%, 1% and 75%, 1% and 50%, 1% and 30%, 1% and 25%, 5% and 100%, 5% and 75%, 5% and 50%, 5% and 30%, 5% and 25%, 10% and 100%, 10% and 75%, 10% and 50%, 10% and 30%, or 10% and 25%.

[0152] In some embodiments, the antigen binding construct, or minibody, comprises a LFR2 that is SEQ ID NO: 137 or 138; and the antigen binding construct, or minibody has improved biodistribution as compared to an antigen binding construct, or minibody comprising an LFR2 that is SEQ ID NO: 136.

[0153] In some embodiments, the antigen binding construct, or minibody, has a KD (e.g., KD of binding to a DLL3 protein) of less than about 10’5M, 10’6M, 10'7M, 10'8M, 10’9M, 10 ° M, 1041M, 1042M, 1043M, 1044M, or 1045M, or a KD in a range defined by any two of the preceding values. For example, in some embodiments, the antigen binding construct, minibody, or cys-diabody, has a KD (e.g., KD of binding to an antigen) of between about 10'5M and 1045M, I04M and IO’12M, 10'5M and IO’10M, IO’7M and 105M, 1 O’7M and 1042M, 10'7M and 104°M, 10‘10M and 10'15M, or 10‘10M and 10'12M. In some embodiments, the KD is determined for an antibody dissolved in buffer. In some embodiments, the buffer is a phosphate buffer. If desired, the KD can be determined using any suitable option, e.g., biolayer interferometry or surface plasmon resonance.

[0154] In some embodiments, the antigen binding construct or minibody has an EC50 (e.g., EC50 of binding to a DLL3 protein, or a cell expressing a DLL3 protein) of, of about, of at most, or less than 0.001, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 2, 2.1, 2.2, 2.3, 2.4 , 2.5 or 3 nM or an EC50 in a range that is defined by any two of the preceding values. For example, in some embodiments, the antigen binding construct or minibody has an EC50 (e.g., EC50 of binding to an antigen, or a cell expressing an antigen) of between about 0.001 and 3 nM, 0.001 and 0.17 nM, 0.001 and 0.12 nM, 0.01 and 0.20 nM, 0.01 and 0.17 nM, 0.01 and 0.12 nM, 0.05 and 0.20 nM, 0.05 and 0.17 nM. 0.05 and 0.15 nM, 0.05 and 0.12 nM, 0.08 and 0.20 nM, 0.08 and 0.17 nM, 0.08 and 0.12 nM, 0.12 and 0.22nM, 0.14 and 0.18nM, 0.3 and 0.4nM, 0.5 and InM, 1 and 1.4nM, 1.1 and 2.1 nM, or 1.5 and 2.5 nM. In some embodiments, the antigen binding construct or minibody, has an EC50 (e.g., EC50 of binding to a DLL3 protein, or a cell expressing a DLL3 protein) of up to about 10 nM. If desired, the EC50 can be determined using any suitable option, e.g., using ELISA or flow cytometry.Therapeutic agents and Compositions

[0155] Provided herein is a composition, e.g., a therapeutic composition, that includes any one of the antigen binding constructs provided herein. In some embodiments, the pharmaceutical composition can also include a pharmaceutically acceptable carrier. A pharmaceutically acceptable carrier can be a pharmaceutically acceptable material, composition, or vehicle that is involved in carrying or transporting a compound of interest from one tissue, organ, or portion of the body to another tissue, organ, or portion of the body. For example, the carrier can be a liquid or solid filler, diluent, excipient, solvent, or encapsulating material, or some combination thereof. Each component of the carrier is "pharmaceutically acceptable" in that it is compatible with the other ingredients of the formulation. It is also suitable for contact with any tissue, organ, or portion of the body that it can encounter, meaning that, ideally it will not carry asignificant risk of toxicity, irritation, allergic response, immunogenicity, or any other complication that excessively outweighs its therapeutic benefits.

[0156] In some embodiments, the therapeutic composition comprises: an antigen binding construct that comprises: a VL domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; and a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85 and a VH domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82; and a therapeutic agent, toxic payload, and / or a detectable marker. In some embodiments, the HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3 sequences are selected according to the arrangement of the HCDRs and LCDRs in any one of FIGs. 1-6. In some embodiments, an antigen binding construct is a minibody that further includes a hinge region (e.g., any one of the hinge regions described herein) and an IgG CH3 sequence (e.g., any one of the CH3 sequences described herein). In some embodiments, an antigen binding construct is a cys-diabody that further includes an extension sequence (e.g., GGC or GGCPPCPPC (SEQ ID NO:203)) at the C-terminus of a monomer.

[0157] In some embodiments, the therapeutic composition comprises: a minibody that binds to DLL3, the minibody comprising: a single-chain variable fragment (scFv) that binds to DLL3, the scFv comprising a variable light (VL) domain linked to a variable heavy (VH) domain, the VL domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; and a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85 and the VH domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82; a hingeextension domain comprising a IgGl hinge region; an IgG CH3 sequence; and a therapeutic agent, toxic payload, and / or a detectable marker. In some embodiments, the HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3 sequences are combined according to the arrangement of the HCDRs and LCDRs in any one of FIGs. 1-6.

[0158] In some embodiments, the therapeutic composition comprises: a cys-diabody that binds to DLL3, the cys-diabody comprising: a polypeptide chain comprising a variable light (VL) domain linked to a variable heavy (VH) domain, the VL domain comprising: a LCDR1 that isany one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; and a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85; and the VH domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82; and an extension sequence (e.g., GGC or GGCPPCPPC (SEQ ID NO:203)) at the C-terminus of a monomer; and a therapeutic agent, toxic payload, and / or a detectable marker. In some embodiments, the HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3 sequences are combined according to the arrangement of the HCDRs and LCDRs in any one of FIGs. 1-6.

[0159] In some embodiments, the therapeutic composition comprises one or more of the minibody arrangements provided in any one of the figures and / or in the Tables disclosed herein.

[0160] In some embodiments, the therapeutic composition comprises an antigen binding construct or minibody, VL, VH, CDR, FR, linker, signal peptide, or any combination therein, having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to an antigen binding construct or minibody, VL, VH, CDR, FR, linker, signal peptide, of any of one or more of SEQ ID NOs: 1-223. In some embodiments, the therapeutic composition comprises a minibody that is any of SEQ ID NOs: 110- 135 (with or without the signal sequence). In some embodiments, the therapeutic composition comprises a minibody having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a minibody that is any of SEQ ID NOs: 110- 135 (with or without the signal sequence). In some embodiments, the therapeutic composition comprises a minibody that is any of SEQ ID NOs: 114-125 (with or without the signal sequence). In some embodiments, the therapeutic composition comprises a minibody having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a minibody that is any of SEQ ID NOs: 114-125 (with or without the signal sequence).

[0161] In some embodiments, the therapeutic composition includes an antigen binding construct (e.g., minibody, cys-diabody, etc.) that comprises a LCDR that is any of SEQ ID NOs: 6, 29, 50, 63, 73, 83, 7, 30, 51, 64, 74, 84, 8, 31, 32, 52, 65, 75, or 85. In some embodiments, the therapeutic composition includes an antigen binding construct (e.g., minibody, cys-diabody, etc.) that comprises a LCDR having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a LCDR that is any of SEQ ID NO: 6, 29,50, 63, 73, 83, 7, 30, 51 , 64, 74, 84, 8, 31 , 32, 52, 65, 75, or 85. In some embodiments, the therapeutic composition includes an antigen binding construct (c.g., minibody, cys-diabody, etc.) that comprises a HCDR that is any of SEQ ID NOs: 3, 18, 26, 47, 59, 70, 80, 4, 27, 48, 60, 71, 81, 5, 19, 28, 49, 61, 62, 72, or 82. In some embodiments, the therapeutic composition includes an antigen binding construct (e.g., minibody, cys-diabody, etc.) that comprises a HCDR having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a HCDR that is any of SEQ ID NOs: 3, 18, 26, 47, 59, 70, 80, 4, 27, 48, 60, 71, 81, 5, 19, 28, 49, 61, 62, 72, or 82. In some embodiments, the therapeutic composition includes an antigen binding construct (e.g., minibody, cys-diabody, etc.) that comprises a FR that is any of SEQ ID NOs: 136-141. In some embodiments, the therapeutic composition includes an antigen binding construct (e.g., minibody, cys-diabody, etc.) that comprises a FR having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a FR that is any of SEQ ID NOs: 136-141. In some embodiments, the therapeutic composition includes an antigen binding construct (e.g., minibody, cys-diabody, etc.) that comprises a linker that is any of SEQ ID NO: 159-164. In some embodiments, the therapeutic composition includes an antigen binding construct (e.g., minibody, cys-diabody, etc.) that comprises a linker having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a linker that is any of SEQ ID NO: 159-164. In some embodiments, the therapeutic composition includes an antigen binding construct (e.g., minibody, cys-diabody, etc.) that comprises a signal peptide that is of SEQ ID NO: 158. In some embodiments, the therapeutic composition includes an antigen binding construct (e.g., minibody, cys-diabody, etc.) that comprises a signal peptide having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a signal peptide that is of SEQ ID NO: 158. In some embodiments, the therapeutic composition includes an antigen binding construct (e.g., minibody, cys-diabody, etc.) that comprises a VH that is any one of SEQ ID NO: 1, 9, 10, 11, 12, 13, 24, 45, 57, 68 or 78. In some embodiments, the therapeutic composition includes an antigen binding construct (e.g., minibody, cys-diabody, etc.) that comprises a minibody having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a VH that is any one of SEQ ID NO: 1, 9, 10, 11, 12, 13, 24, 45, 57, 68 or 78. In some embodiments, the therapeutic composition includes an antigen binding construct (e.g., minibody, cys-diabody, etc.) that comprises a VL that is any one of SEQID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69, or 79. In some embodiments, the therapeutic composition includes an antigen binding construct (c.g., minibody, cys-diabody, etc.) that comprises a VL having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a VL that is any of SEQ ID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69, or 79.

[0162] The pharmaceutical, or therapeutic, compositions described herein can be administered by any suitable route of administration. A route of administration can refer to any administration pathway known in the art, including but not limited to aerosol, enteral, nasal, ophthalmic, oral, parenteral, rectal, transdermal (e.g., topical cream or ointment, patch), or vaginal. "Transdermal" administration can be accomplished using a topical cream or ointment or by means of a transdermal patch. "Parenteral" refers to a route of administration that is generally associated with injection, including infraorbital, infusion, intraarterial, intracapsular, intracardiac, intradermal, intramuscular, intraperitoneal, intrapulmonary, intraspinal, intrastemal, intrathecal, intracranial, intraventricular, intrauterine, intravenous, subarachnoid, subcapsular, subcutaneous, sublingual, transmucosal, or transtracheal. In some embodiments, the antigen binding construct can be delivered intraoperatively as a local administration during an intervention or resection.

[0163] In some embodiments, an antigen binding construct or minibody is conjugated to a therapeutic agent. A "therapeutic agent" as used herein is an atom, molecule, or compound that is useful in the treatment of a disorder related to a target molecule. Examples of therapeutic agents include, but are not limited to, drugs, chemotherapeutic agents, therapeutic antibodies and antibody fragments, toxins, radioisotopes, enzymes (for example, enzymes to cleave prodrugs to a cytotoxic agent at the site of the antigen binding construct binding), nucleases, hormones, immunomodulators, antisense oligonucleotides, chelators, boron compounds, photoactive agents and dyes, elastin-like polypeptides such as PLGA, and nanoparticles. Examples of disorders include those related to one or more target molecules.

[0164] Chemotherapeutic agents are often cytotoxic or cytostatic in nature and may include alkylating agents, antimetabolites, anti-tumor antibiotics, topoisomerase inhibitors, mitotic inhibitors hormone therapy, targeted therapeutics and immunotherapeutics. In some embodiments the chemotherapeutic agents that may be used as detectable markers in accordance with the embodiments of the disclosure include, but are not limited to, 13-cis-Retinoic Acid, 2- Chlorodeoxyadenosine, 5 -Azacitidine, 5 -Fluorouracil, 6-Mercaptopurine, 6-Thioguanine,actinomycin-D, adriamycin, aldesleukin, alemtuzumab, alitretinoin, all-transretinoic acid, alpha interferon, altrctaminc, amcthoptcrin, amifostinc, anagrclidc, anastrozolc, arabinosylcytosinc, arsenic trioxide, amsacrine, aminocamptothecin, aminoglutethimide, asparaginase, azacytidine, bacillus calmette-guerin (BCG), bendamustine, bevacizumab, bexarotene, bicalutamide, bortezomib, bleomycin, busulfan, calcium leucovorin, citrovorum factor, capecitabine, canertinib, carboplatin, carmustine, cetuximab, chlorambucil, cisplatin, cladribine, cortisone, cyclophosphamide, cytarabine, darbepoetin alfa, dasatinib, daunomycin, decitabine, denileukin diftitox, dexamethasone, dexasone, dexrazoxane, dactinomycin, daunorubicin, decarbazine, docetaxel, doxorubicin, doxifluridine, eniluracil, epirubicin, epoetin alfa, erlotinib, everolimus, exemestane, estramustine, etoposide, filgrastim, fluoxymesterone, fulvestrant, flavopiridol, floxuridine, fludarabine, fluorouracil, flutamide, gefitinib, gemcitabine, gemtuzumab ozogamicin, goserelin, granulocyte - colony stimulating factor, granulocyte macrophage-colony stimulating factor, hexamethylmelamine, hydrocortisone hydroxyurea, ibritumomab, interferon alpha, interleukin - 2, interleukin-11, isotretinoin, ixabepilone, idarubicin, imatinib mesylate, ifosfamide, irinotecan, lapatinib, lenalidomide, letrozole, leucovorin, leuprolide, liposomal Ara-C, lomustine, mechlorethamine, megestrol, melphalan, mercaptopurine, mesna, methotrexate, methylprednisolone, mitomycin C, mitotane, mitoxantrone, nelarabine, nilutamide, octreotide, oprelvekin, oxaliplatin, paclitaxel, pamidronate, pemetrexed, panitumumab, PEG Interferon, pegaspargase, pegfilgrastim, PEG-L-asparaginase, pentostatin, plicamycin, prednisolone, prednisone, procarbazine, raloxifene, rituximab, romiplostim, ralitrexed, sapacitabine, sargramostim, satraplatin, sorafenib, sunitinib, semustine, streptozocin, tamoxifen, tegafur, tegafur-uracil, temsirolimus, temozolamide, teniposide, thalidomide, thioguanine, thiotepa, topotecan, toremifene, tositumomab, trastuzumab, tretinoin, trimitrexate, alrubicin, vincristine, vinblastine, vindestine, vinorelbine, vorinostat, or zoledronic acid.

[0165] Toxins that may be used in accordance with the embodiments of the disclosure include, but are not limited to, Auristatin E, Auristatin F, Dolastatin 10, Dolastatin 15, combretastatin and their analogs, maytansinoid, calicheamicin, alpha-amanitin, pyrrolobenzodiazepine dimers, epothilones, duocarmycin and their analogs, tubulysin D, basillistatins, ricin, abrin, ribonuclease (RNase), DNase I, Staphylococcal enterotoxin-A, pokeweed antiviral protein, gelonin, diphtheria toxin, Pseudomonas exotoxin, and Pseudomonas endotoxin.

[0166] In some embodiments nanoparticles are used in therapeutic applications as drug carriers that, when conjugated to an antigen binding construct, minibody, or cys-diabody, deliver chemotherapeutic agents, hormonal therapeutic agents, radiotherapeutic agents, toxins, or any other cytotoxic or anti-cancer agents known in the art to cancerous cells that overexpress the target on the cell surface.

[0167] In some embodiments, the antigen binding constructs or minibodies described herein may be further conjugated or co-administered with one or more immunotherapeutic agents. In some embodiments, the antigen binding constructs or minibodies described herein may be conjugated or co-administered with one or more immunotherapeutic agents. For example, in some embodiments, the antigen binding constructs or minibodies described herein may be further conjugated, or co-administered, with anti-PDl and anti-PD-Ll binding agents, anti-CTLA4 agents, and multi- specific agents including, but not limited to, anti-CTLA-4 / B7-l / B7-2. Additional immunotherapies include checkpoint inhibitors such as ipilimumab (Yervoy), pembrolizumab (KEYTRUDA), nivolumab (OPDIVO), atezolizumab (TECENTRIQ), avelumab (BAVENCIO), and durvalumab (IMFINZI). Immunotherapies also include tremelimumab and pidilizumab. Small molecule immunotherapies are also in development including BMS-1001, BMS-1116, CA-170, CA-327, Imiquimod, Resiquimod, 852A, VTX-2337, ADU-S100, MK- 1454, Ibrutinib, 3AC, Idelalisib, IPI-549, Epacadostat, AT-38, CPI-444, Vipadenant, Preladenant, PBF, AZD4635, Galuniseritib, OTX015 / MK-8628, CPI-0610 (c.f. Kerr and Chisolm (2019) The Journal of Immunology, 2019, 202: 11-19.)

[0168] In some embodiments, the antigen binding construct or minibodies described herein is conjugated with one or more DNA damage or DNA repair specific agents. In some embodiments, the agent comprises a DNA damage repair inhibitor, for example, a PARP inhibitor, DNA-dependent protein kinase (DNA-PK) inhibitor, ataxia-telangiectasia and Rad3 related (ATR) inhibitor, ataxia-telangiectasia mutated (ATM) inhibitor, CHK1 inhibitor, WEE1 inhibitor, and POLO inhibitor. In some embodiments, the PARP inhibitor comprises niraparob, Olaparib, talazoparib, and / or rucaparib, or any combination thereof.

[0169] In some embodiments, the antigen binding constructs or minibodies described herein may be further conjugated with one or more kidney- and / or radio-protecting agents. In some embodiments, the antigen binding constructs or minibodies described herein may be coadministered with one or more kidney- and / or radio-protecting agents. In some embodiments, theradioprotecting agent comprises free lysine, free arginine, probenecid, gelofusin, 2,4- dinitrophcnol, caffeine, Ibuprofen, ascorbic acid, caffeic acid, aspirin, carnosine, minocycline, catechin, 4'-O-methylcatechin, 4-phenylbutyric acid, 14937-32-7, lithium chloride, cyclosporine, epoprostenol, fullerene, fumarate, gallic acid, metformin, indirubin, kaempferol, sodium butyrate, spermidine, cholecalciferol, avobenzone, octinoxate, titanium dioxide, tempol, gusperimus, irsogladine, tetrachlorodecaoxide, calcium alginate, gusperimus hydrochloride, D-galacturonic acid sodium salt, cystamine hydrobromide, cystaphos, N-Acetyl-Ser-Asp-Lys-Pro, D08Eai, prolycopene, velaresol, U-74389G maleate, trans-2-hexenyl salicylate, 3-benzylidene camphor, irsogladine maleate, sodium alginate, Gsh-Mee, triethylenediamine diacetate, cystamine hydrochloride, amifostine, glutathione reduced ethyl ester, homocysteine thiolactone, 132316-35- 9, hydroquinone, 13258-59-8, adeturon, unii-S8Kc806H2T, nitrogen oxygen, 2-ethyl-3-hydroxy- 6-methylpyridine, S-ethylglutathione, (8S,10S,13S,14S,17S)-17-[2-[4-(2,6-dipyrrolidin-l- ylpyrimidin-4-Yl)piperazin-l-Yl]acetyl]-10,13-dimethyl-6,7,8,12,14,15,16,17- actahydrocyclopenta[A]phenanthren-3-One, trilazad mesylate, Wr 1065, posphonol, amifostine, l,4-diazabicyclo[2.2.2]octane, gusperimus trihydrochloride, tributyl phosphate, sulfolane, deuterium oxide, benzobarbital, 6-methyluracil, homosalate, cystamine dihydrochloride, 2-(2- aminoethyl)isothiourea dihydrobromide, tempol-H, fenofibrate, cystamine, beta-aminoethyl isothiourea, zingerone, aeol 10150, artemisinin, 16,16-dimethylprostaglandin E2, theaflavin, succinic acid, andrographis, balsalazide, N-adenylyl-L-phenylalanine, chlorophyllin, nacu, dieckol, eckol, diltiazem, edaravone, rhepo, ferulic acid, glutathione, glycyrrhizic acid, hesperidin, indomethacin, misoprostol, morin, myricetin, tiopronin, naringin, recilisib sodium, probucol, hydroxyethylrutoside, cystaphos, sulfasalazine, sucralfate, chugai, silymarin, floxacillin, cyproterone, cysteamine, thymol, mercaptoethanol, desogestrel, cellobiose, kanamycin, sodium alginate, acetylcysteine, zinc oxide, cystaphos, 10-hydroxy-2-decenoic acid, teduglutide, curcuma, troxerutin, trichostatin A, selegiline, lycopene, nitrendipine, glycerol, 21245-02-3, rosmarinic acid, simvastatin, fisetin, sirolimus, oxybenzone, ascophyllum, ecamsule, alginate, alginic acid, potassium salt, potassium alginate, U-74389G, calcium alginate, Hoechst 33342 (Trihydrochloride), polydatin, thioctic acid, enalapril, amifostine, ursolic acid, Unii-Sm5Yj88Ltu, carbonyl cyanide m-chlorophenyl hydrazone, genistein, resveratrol, (-)-epigallocatechin gallate, ellagic acid, baicalein, valproic acid, pentoxifylline, acacia, melatonin, trehalose, acteoside, kukoamine, atorvastatin, carvacrol, isofraxidin, palifermin, cysteine, vitamin E, heparin,chondroethin sulfate, AET, M40403, EUK- 189, EUK-207, vitamin C, vitamin A, lipoic acid, P- carotcnc, L- selenomethionine, and / or Q10.

[0170] Any of the antigen binding constructs or minibodies described herein may be further conjugated with one or more additional therapeutic agents, detectable markers, nanoparticles, carriers or a combination thereof. For example, an antigen binding construct may be radiolabeled with Iodine- 131 and conjugated to a lipid carrier, such that the anti-target molecule-lipid conjugate forms a micelle. The micelle can incorporate one or more therapeutic agents, isotopes, ions, and / or detectable markers.

[0171] In some embodiments, antigen binding constructs or minibodies are conjugated to a therapeutic agent. While some of the antigen binding constructs can have a shorter circulation half-life compared to a full-length antibody, in some embodiments, these formats can exhibit improved tumor penetration based on their smaller size and be therapeutically effective when appropriately armed with a cytotoxic drug or radioisotope. In some embodiments, an antigen binding construct or minibody, drug-conjugate approach can be employed. In some embodiments, a therapeutic approach includes radioimmunotherapy by attaching an appropriate radioisotopes such as, a beta-emitter or alpha-emitter, such as, Iodine-131, Yttrium-90, Lutetium-177, Copper- 67, Terbium-149, Terbium-161, Astatine-211, Lead-212, Bismuth-212, Actinium-225, Bismuth- 213, and 227-Thorium, which can deliver cell damage and death to a target tissue. In some embodiments, treatment with these fragments armed with a cytotoxic drug or radionuclide results in less nonspecific toxicity as they will be cleared from the body more rapidly. In some embodiments, the radiolabel includes Terbium-149, Terbium-161, or Lead-212.

[0172] In some embodiments, the label and / or therapeutic agent comprises18F,18F- FAC,32P,33P,45Ti,47Sc,52Fe,59Fe,62Cu, ^Cu,67Cu,67Ga,68Ga,75Sc,77As,86Y,90Y,89Sr,89Zr,94TC,94TC,99mTc, "Mo,105Pd,105Rh,i nAg,niIn,123I,124I,125I,131I,142Pr,143Pr,149Pm,149Tb,153Sm,154‘158Gd,161Tb,166Dy,166Ho,169Er,175Lu,177Lu,186Re,188Re,189Re,194Ir,198Au,199Au,211At,211Pb,212Bi,212Pb,213Bi,223Ra,227Th and225Ac, or any combination thereof.

[0173] In some embodiments, the antigen binding construct or minibody, can be connected to a therapeutic agent to a disorder associated with the expression of the target molecule.

[0174] In some embodiments, target molecule antigen binding constructs are used as a stand-alone medicament (e.g. antigen binding construct in the absence of therapeutic agent) in the treatment of a disorder associated with the expression of the target molecule.Methods of detecting the presence or absence of the target molecule

[0175] Antigen binding constructs or minibodies can be used to detect the presence or absence of the target molecule in vivo and / or in vitro. Accordingly, some embodiments include methods of detecting the presence or absence of the target. In some embodiments, the construct recognizes and binds the DLL3 protein. In some embodiments, the target is DLL3-expressing cells.

[0176] In some embodiments, the antigen binding construct or minibody is labeled with a detectable marker. The marker can be for instance, a radioisotope, a fluorescent compound, a bioluminescent compound, chemiluminescent compound, a metal chelator or an enzyme. In some embodiments, the detectable marker comprises a phototherapy dye. In some embodiments, the detectable marker comprises boron. In some embodiments, the detectable marker comprises a marker that is compatible with Boron Neutron Capture Therapy (BNCT). In some embodiments, the detectable marker is suitable for use with Auger electron spectroscopy. In some embodiments, the detectable marker comprises a payload. In some embodiments, the at least one payload is selected from a group consisting of18F,18F-FAC,32P,33P,45Ti,47Sc,52Fe,59Fe,62Cu,MCu.67Cu,67Ga,68Ga,75Sc,77As,86Y,90Y,89Sr,89Zr,94Tc,94Tc,99mTc, "Mo,105Pd,105Rh,inAg,1HIn,123I,124I,125I,131I,142Pr,143Pr,149Pm,149Tb,153Sm,154’158Gd,161Tb,166Dy,166Ho,169Er,175Lu,177Lu,186Re,188Re,189Re,194Ir,198Au,199Au,211At,211Pb,212Bi,212Pb,213Bi,223Ra,227Th and225Ac, or any combination thereof. In some embodiments, the marker is a radioisotope. Many radionucleotides may be used as imaging labels, including without limitation,211At,131I,125I,90Y,186Re,188Re,153Sm,212Bi,32P,212Pb,89Zr,frlCu,18F,68G,124I, and the like. One skilled in the art will know of other radionuclides particularly well suited for use in the present disclosure.

[0177] In some embodiments, the method kills the cancer cell. In additional embodiments, the method further comprises administering to a subject a chemotherapeutic drug, and / or radiation therapy. In some embodiments, the subject is also treated with hormone ablation therapy or hormone antagonist therapy.

[0178] The method can include applying an antigen binding construct or minibody to a subject. In some embodiments, the antigen binding construct or minibody, is applied to a sample. The method can include detecting a binding (or presence of binding) or an absence of binding of the antigen binding construct or minibody, to the target molecule. In some embodiments, any targetmolecule could be detected through the options provided herein. Tn some embodiments, the target molecule to be detected is DLL3. In some embodiments, the target molecule is detected using one or more of the minibody arrangements provided in the figures and / or in the Tables, such as Tables 11 and 12.TABLE 11TABLE 12

[0179] In some embodiments, any of the constructs provided herein can be employed without or can exclude the signal peptide or signal sequence (e.g., the initial sequence underlined in Tables 11 and 12). In some embodiments, the signal sequence (or signal peptide) is SEQ ID NO: 158. In some embodiments, the signal sequence is located immediately upstream of the antigen binding construct or minibody. In some embodiments, residue 20 of the signal peptide (Kabat) is immediately adjacent to residue number 1 of the antigen binding construct or minibody (Kabat). In any and every embodiment provided herein, the signal sequence is optional, and can be included or excluded from any of the herein disclosed antigen binding construct or minibody.

[0180] Methods of detecting the presence or absence of the target molecule are provided herein. It will be appreciated that the processes below can be performed in any sequence, and / or can be optionally repeated and / or eliminated, and that additional steps can optionally be added to the method. In some embodiments, an antigen binding construct or minibody, as described herein can be applied to a sample. In some embodiments, an optional wash can be performed. Optionally, a secondary antigen binding construct can be applied to the sample. An optional wash can be performed. In some embodiments, a binding or absence of binding of the antigen binding construct or minibody, to the target molecule can be detected.

[0181] In some embodiments, an antigen binding construct or minibody, as described herein is applied to a sample in vivo. The antigen binding construct can be administered to a subject. In some embodiments, the subject is a human. In some embodiments, the subject is a nonhuman mammal, for example a rat, mouse, guinea pig, hamster, rabbit, dog, cat, cow, horse, goat, sheep, donkey, pig, monkey, or ape. In some embodiments, the antigen binding construct is infused into the subject. In some embodiments, the infusion is intravenous. In some embodiments, the infusion is intraperitoneal. In some embodiments, the antigen binding construct or minibody, is applied topically or locally (as in the case of an interventional or intraoperative application) to the subject. In some embodiments, a capsule containing the antigen binding construct or minibody, is applied to the subject, for example orally or intraperitoneally. In some embodiments, the antigen binding construct or minibody, is selected to reduce the risk of an immunogenic response by subject. For example, for a human subject, the antigen binding construct or minibody, can be humanized as described herein. In some embodiments, following in vivo application of the antigen binding construct or minibody, the sample, or a portion of the sample is removed from the host. In some embodiments, the antigen binding construct or minibody, is applied in vivo, is incubated in vivo for a period of time as described herein, and a sample is removed for analysis in vitro, for example in vitro detection of antigen binding construct or minibody, bound to the target molecule or the absence thereof as described herein.

[0182] In some embodiments, the antigen binding construct or minibody, is applied to a sample in vitro. In some embodiments, the sample is freshly harvested from a subject, for example a biopsy. In some embodiments, the sample is incubated following harvesting from a subject. In some embodiments, the sample is fixed. In some embodiments the sample includes a whole organ and / or tissue. In some embodiments, the sample includes one or more whole cells. In some embodiments the sample is from cell extracts, for example lysates. In some embodiments, antigen binding construct in solution is added to a solution in the sample. In some embodiments, antigen binding construct or minibody, in solution is added to a sample that does not contain a solution, for example a lyophilized sample, thus reconstituting the sample. In some embodiments, lyophilized antigen binding construct, minibody, or cys-diabody, is added to a sample that contains solution, thus reconstituting the antigen binding construct or minibody.

[0183] In some embodiments, the antigen binding construct or minibody, is optionally incubated with the sample. The antigen binding construct or minibody, can be incubated for aperiod of no more than about 1 days, for example no more than about 1 days, 13, 12, 1 1 , 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 day, or no more than about 23 hours, for example no more than about 23 hours, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.75, 0.5, 0.25, or 0.1 hour, or is a range that is defined by any two of the preceding values. In some embodiments, the incubation is within a subject to which the antigen binding construct or minibody, was administered. In some embodiments, the incubation is within an incubator. In some embodiments, the incubator is maintained at a fixed temperature, for example about 21 °C, room temperature, 25°C, 29°C, 34°C, 37°C, or 40°C.

[0184] In some embodiments, the antigen binding construct or minibody, that is not bound to the target is optionally removed from the sample. In some embodiments, the sample is washed. Washing a sample can include removing the solution that contains unbound antigen binding construct or minibody, and adding solution that does not contain antigen binding construct or minibody, for example buffer solution. In some embodiments, an in vitro sample is washed, for example by aspirating, pipetting, pumping, or draining solution that contains unbound antigen binding construct or minibody, and adding solution that does not contain antigen binding construct or minibody. In some embodiments, an in vivo sample is washed, for example by administering to the subject solution that does not contain antigen binding construct or minibody, or by washing a site of topical antigen binding construct administration. In some embodiments, the wash is performed at least two times, for example at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, or 20 times. In some embodiments, following the wash or washes, at least about 50% of unbound antibody is removed from the sample, for example at least about 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 97%, 98%, 99% or greater.

[0185] In some embodiments, unbound antigen binding construct or minibody is eliminated from the sample. Following application of the antigen binding construct or minibody, to the sample, antigen binding construct bound to the target reaches an equilibrium with antigen binding construct unbound to the target, so that at some time after application of the antigen binding construct, the amount of antigen binding construct bound to the target does not substantially increase. After this time, at least part of the quantity of the antigen binding construct or minibody, that is unbound to the target can be eliminated. In some embodiments, unbound antigen binding construct or minibody, is eliminated by metabolic or other bodily processes of the subject to whom the antigen binding construct or minibody, was delivered. In some embodiments,unbound antigen binding construct or minibody, is eliminated by the addition of an agent that destroys or destabilized the unbound antigen binding construct or minibody, for example a protease or a neutralizing antibody. In some embodiments, 1 day after application of the antigen binding construct or minibody, at least about 30% of the antigen binding construct that was applied has been eliminated, for example at least about 30%, 40%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 97%, 98%, 99%, or 99.9%. In some embodiments, 2 days after application of the antigen binding construct or minibody, at least about 40% of the antigen binding construct or minibody, that was applied has been eliminated, for example at least about 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 97%, 98%, 99%, or 99.9%.

[0186] In some embodiments, the presence or absence of the target molecule is detected. The presence or absence of the target can be detected based on the presence or absence of the antigen binding construct in the sample. After removal and / or elimination of the antigen binding construct from the sample, for example by washing and / or metabolic elimination, remaining antigen binding construct in the sample can indicate the presence of the target, while an absence of the antigen binding construct in the sample can indicate the absence of the target.

[0187] In some embodiments, the antigen binding construct includes a detectable marker as described herein. Thus, the presence of the antigen binding construct can be inferred by detecting the detectable marker.

[0188] In some embodiments, a secondary antigen binding construct or minibody, is used to detect the antigen binding construct or minibody. The secondary antigen binding construct or minibody, can bind specifically to the antigen binding construct. For example, the secondary antigen binding construct or minibody, can include a polyclonal or monoclonal antibody, diabody, minibody, etc. against the host type of the antibody, or against the antigen binding construct or minibody, itself. The secondary antigen binding construct or minibody, can be conjugated to a detectable marker as described herein. The secondary antigen binding construct or minibody, can be applied to the sample. In some embodiments, the secondary antigen binding construct or minibody, is applied to the sample in substantially the same manner as the antigen binding construct or minibody. For example, if the antigen binding construct or minibody was infused into a subject, the secondary antigen binding construct or minibody, can also be infused into the subject.

[0189] In some embodiments, binding (or the presence of binding) or the absence of binding of the antigen binding construct or minibody, is detected via at least one of: positronemission tomography (PET), single-photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), Computed Tomography (CT), or detection of fluorescence emissions. PET can include, but is not limited to, small animal PET or PET / CT imaging. In some embodiments, binding (or the presence of binding) or the absence of binding of the antigen binding construct, minibody, or cys-diabody is detected via two or more forms of imaging. In some embodiments, detection can be via near-infrared (NIR) and / or Cerenkov.

[0190] In some embodiments, any combination of imaging modalities is possible, including, by way of example, PET + CR, SPECT + CT, PET + MRI, PET + NIR, PET + SPECT etc. “PET” is a diagnostic technique that can be used to observe functions and metabolism of human organs and tissues at the molecular level. For PET, a positron radioactive drug (e.g., 18F- FDG) can be injected into a human body. If FDG is used, because the metabolism of fludeoxyglucose (FDG) is similar to glucose, the FDG will gather in cells that digest the glucose. A positron emitted by the decay of 18F and an electron in tissues will undergo an annihilation reaction to generate two gamma-photons with the same energy in opposite directions. A detector array surrounding the human body can detect the two photons using a coincidence measurement technique and determine position information of the positron. A tomography image of positrons in the human body can then be constructed by processing the position information using an image reconstruction software. In some situations, Immuno-PET can be employed, where the label (e.g., 18F) is attached or associated with an antigen binding construct. In such embodiments, the distribution of the antigen binding construct can be monitored, which will depend upon the binding properties and distribution properties of the antigen binding construct. For example, if a CD8- directed minibody is used, then PET can be used to monitor the distribution of the CD8 molecules through the hosts’ system. PET systems are known in the art and include, for example U.S. Pat. Pub. No. 20170357015, 20170153337, 20150196266, 20150087974, 20120318988, and 20090159804, the entireties of each of which are incorporated by reference herein for their description regarding PET and the use thereof.

[0191] In some embodiments, imaging is conducted through PET scan, a PET / CT scan, or SPECT scan. In some embodiments, imaging is conducted through photoacoustic, optical probes, MR imaging, magnetic nanoparticles for imaging, spectroscopy, and / or any other standard method of imaging. In some embodiments, at least one optical probe is coupled together with at least one metal chelator. In some embodiments, optical imaging is used for assisted surgery. Insome embodiments, photodynamic therapy is used. In some embodiments, photodynamic therapy is used for assisted surgery. In some embodiments, infrared fluorescence is used for assisted surgery. In some embodiments, photodynamic therapy is used for theranostics.Nucleic Acid

[0192] In some embodiments, the polypeptides of the antigen binding constructs or minibodies, can be encoded by nucleic acids and expressed in vivo or in vitro, or these peptides can be synthesized chemically. In some embodiments, the nucleic acid encodes one part or monomer of an antigen binding construct or minibody. In some embodiments, the nucleic acid encodes two or more monomers, for example, at least 2 monomers. Nucleic acids encoding multiple monomers can include nucleic acid cleavage sites between at least two monomers, can encode transcription or translation start site between two or more monomers, and / or can encode proteolytic target sites between two or more monomers. In some embodiments, the nucleic acid encodes an antigen binding construct or minibody, VL, VH, CDR, FR, linker, signal peptide, or any combination therein. In some embodiments, the nucleic acid encodes an antigen binding constructs or minibodies, VL, VH, CDR, FR, linker, signal peptide, or any combination therein.

[0193] In some embodiments, an expression vector contains a nucleic acid encoding an antigen binding construct or minibody, as disclosed herein. In some embodiments, the expression vector includes pcDNA3.1™ / myc-His (-) Version A vector for mammalian expression (Invitrogen, Inc.) or a variant thereof. The pcDNA3.1 expression vector features a CMV promoter for mammalian expression and both mammalian (Neomycin) and bacterial (Ampicillin) selection markers. In some embodiments, the expression vector includes a plasmid. In some embodiments, the vector includes a viral vector, for example a retroviral or adenoviral vector. In embodiments, the vector includes a cosmid, YAC, or BAC. In some embodiments, the expression vector encodes an antigen binding construct or minibody, VL, VH, CDR, FR, linker, signal peptide, or any combination therein. In some embodiments, the expression vector encodes an antigen binding construct or minibody, VL, VH, CDR, FR, linker, signal peptide, or any combination therein, having at least about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to an antigen binding construct or minibody, VL, VH, CDR, FR, linker, signal peptide, of any one of SEQ ID NO: 1-223 In some embodiments, the expression vector encodes a minibody that comprises any one of SEQ ID NO: 110-135 (with or without the signal sequence). In someembodiments, the expression vector encodes a minibody having a sequence that is, is at least, or is about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identical to any one of SEQ ID NO: 110-135 (with or without the signal sequence). In some embodiments, the expression vector encodes an antigen binding construct (e.g., a minibody or cys-diabody) that includes a LCDR that is any one of SEQ ID NO: 6, 29, 50, 63, 73, 83, 7, 30, 51, 64, 74, 84, 8, 31, 32, 52, 65, 75, or 85. In some embodiments, the expression vector encodes an antigen binding construct (e.g., a minibody or cys-diabody) that includes a LCDR having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a LCDR that is any one of SEQ ID NO: 6, 29, 50, 63, 73, 83, 7, 30, 51, 64, 74, 84, 8, 31, 32, 52, 65, 75, or 85. In some embodiments, the expression vector encodes an antigen binding construct (e.g., a minibody or cys-diabody) that includes a HCDR that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, 80, 4, 27, 48, 60, 71, 81, 5, 19, 28, 49, 61, 62, 72, or 82. In some embodiments, the expression vector encodes an antigen binding construct (e.g., a minibody or cys-diabody) that includes a HCDR having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a HCDR that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, 80, 4, 27, 48, 60, 71, 81, 5, 19, 28, 49, 61, 62, 72, or 82. In some embodiments, the expression vector encodes an antigen binding construct (e.g., a minibody or cys-diabody) that includes a FR that is any one of SEQ ID NO: 136-141. In some embodiments, the expression vector encodes an antigen binding construct (e.g., a minibody or cys-diabody) that includes a FR having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a FR that is any one of SEQ ID NO: 136-141. In some embodiments, the expression vector encodes an antigen binding construct (e.g., a minibody or cys-diabody) that includes a linker that is any one of SEQ ID NO: 159-164. In some embodiments, the expression vector encodes an antigen binding construct (e.g., a minibody or cys-diabody) that includes a linker having at least about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a linker that is any one of SEQ ID NO: 159-164. In some embodiments, the expression vector encodes an antigen binding construct (e.g., a minibody or cys-diabody) that includes a signal peptide that is of SEQ ID NO: 158. In some embodiments, the expression vector encodes a signal peptide having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a signal peptide that is of SEQ ID NO: 158. In some embodiments, the expression vector encodes an antigen binding construct (e.g., a minibody or cys-diabody) that includes a VH that is any one of SEQ ID NO: 1, 9, 10, 11 , 12, 13, 24, 45, 57, 68 or78. In some embodiments, the nucleic acid encodes a an antigen binding construct (e.g., a minibody or cys-diabody) that includes a VH having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a VH that is any one of SEQ ID NO: 1, 9, 10, 11, 12, 13, 24, 45, 57, 68 or 78. In some embodiments, the expression vector encodes an antigen binding construct (e.g., a minibody or cys-diabody) that includes a VL that is any one of SEQ ID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69, or 79. In some embodiments, the expression vector encodes an antigen binding construct (e.g., a minibody or cys-diabody) that includes a VL having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a VL that is any one of SEQ ID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69, or79. In any of the embodiments provided herein, a sequence encoding the signal peptide can be excluded from the nucleic acid sequence, for some embodiments. In some embodiments the nucleic acid encodes a binding construct and / or minibody that is an antigen binding construct and / or minibody in Table 11 or 12. In some embodiments, the expression vector encodes an antigen binding construct and / or minibody, that is an antigen binding construct and / or minibody in Table 11 or 12.Cells

[0194] In some embodiments, a cell line is provided that expresses at least one of the antigen binding constructs or minibodies described herein. In some embodiments, a mammalian cell line (for example, CHO-K1, ExpiCHO, HEK-293, 293f, Expi293 cell lines) is an expression system to produce the antigen binding constructs or minibodies, or other antibodies as described herein. In some embodiments, the antigen binding constructs or minibodies, and other antibodies or antibody fragments described herein are non-glycosylated, and a mammalian expression system is not required, as such post-translational modifications are not needed. Thus, in some embodiments, one or more of a wide variety of mammalian or non-mammalian expression systems are used to produce antigen binding constructs or minibodies, described herein including, but not limited to mammalian expression systems (for example, CHO-K1 cells), bacterial expression systems (for example, E. coli, B. subtilis) yeast expression systems (for example, Pichia, S. cerevisiae) or any other known expression system. Other systems can include insect cells and / or plant cells.

[0195] In some embodiments, the cell expresses an antigen binding construct, or minibody, VL, VH, CDR, FR, linker, signal peptide, or any combination therein. In some embodiments, the cell expresses an antigen binding construct or minibody, VL, VH, CDR, FR, linker, signal peptide, or any combination therein, having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to an antigen binding construct, minibody, cys-diabody, VL, VH, CDR, FR, linker, signal peptide, of any of SEQ ID NO: 1-223. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys-diabody) that includes any one of SEQ ID NO: 1-87, 110-135. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys-diabody) that includes a sequence that is, is at least, or is about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identical to any one of SEQ ID NO: 1-87, 110-135. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys-diabody) that includes a LCDR that is any one of SEQ ID NO: 6, 29, 50, 63, 73, 83, 7, 30, 51, 64, 74, 84, 8, 31, 32, 52, 65, 75, or 85. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys- diabody) that includes a LCDR having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to any one of SEQ ID NO: 6, 29, 50, 63, 73, 83, 7, 30, 51, 64, 74, 84, 8, 31, 32, 52, 65, 75, or 85. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys-diabody) that includes a HCDR that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, 80, 4, 27, 48, 60, 71, 81, 5, 19, 28, 49, 61, 62, 72, or 82. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys-diabody) that includes a HCDR having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a HCDR that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, 80, 4, 27, 48, 60, 71, 81, 5, 19, 28, 49, 61, 62, 72, or 82. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys-diabody) that includes a FR that is any one of SEQ ID NO: 136-141. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys-diabody) that includes a FR having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a FR that is any one of SEQ ID NO: 136-141. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys-diabody) that includes a linker that is any one of SEQ ID NO: 159-164. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys-diabody) that includes a linker having, having at least, or having about 70%,75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a linker that is any one of SEQ ID NO: 159-164. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys-diabody) that includes a signal peptide that is of SEQ ID NO: 158. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys- diabody) that includes a signal peptide having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a signal peptide that is of SEQ ID NO: 158. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys-diabody) that includes a VH that is any one of SEQ ID NO: 1, 9, 10, 11, 12, 13, 24, 45, 57, 68 or 78. In some embodiments, the cell expresses a minibody having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a VH that is any one of SEQ ID NO: 1, 9, 10, 11, 12, 13, 24, 45, 57, 68 or 78. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys-diabody) that includes a VL that is any one of SEQ ID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69, or 79. In some embodiments, the cell expresses an antigen binding construct (e.g., minibody or cys-diabody) that includes a VL having, having at least, or having about 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% or more sequence identity to a VL that is any of SEQ ID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69, or 79.Kits

[0196] In some embodiments, kits are provided. In some embodiments, the kit includes an antigen binding construct, minibody, cys-diabody, or any combination thereof, as described herein. In some embodiments, the kit includes a nucleic acid that encodes an antigen binding construct as described herein. In some embodiments, the kit includes a cell line that produces an antigen binding construct as described herein. In some embodiments, the kit includes a detectable marker as described herein. In some embodiments, the kit includes a therapeutic agent as described herein. In some embodiments, the kit includes buffers. In some embodiments, the kit includes positive controls, for example target specific cells, or fragments thereof. In some embodiments, the kit includes negative controls, for example a surface or solution that is substantially free of the target. In some embodiments, the kit includes packaging. In some embodiments, the kit includes instructions. In some embodiments, the kit comprises: an antigen binding construct, minibody, or cys-diabody, of any of the preceding embodiments; and a chelator, wherein the chelator allowsincorporation of a detectable marker. In some embodiments, the kit comprises: an antigen binding construct, minibody, or cys-diabody, of any of the preceding embodiments; and a chelator, wherein the chelator allows incorporation of a therapeutic isotope. In some embodiments, the kit comprises: an antigen binding construct, minibody, or cys-diabody, of any of the preceding embodiments; and a linker, wherein the linker allows incorporation of a detectable marker. In some embodiments, the kit comprises: an antigen binding construct, minibody, or cys-diabody, of any of the preceding embodiments; and a linker, wherein the linker allows incorporation of a therapeutic isotope.

[0197] Additional embodiments of the present disclosure are provided in the following numbered arrangements.1. An antigen binding construct comprising: a variable light (VL) domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85; and a variable heavy (VH) domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82.2. An antigen binding construct comprising: a variable light (VL) domain comprising: a LCDR1 that is an LCDR1 in any one of SEQ ID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69 or 79; a LCDR2 that is an LCDR2 in any one of SEQ ID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69 or 79; a LCDR3 that is an LCDR3 in any one of SEQ ID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69 or 79; and a variable heavy (VH) domain comprising: a HCDRl that is an HCDR1 in any one of SEQ ID NO:1, 10, 11, 12, 13, 24, 45, 57, 68 or 78; a HCDR2 that is an HCDR2 in any one of SEQ ID NO: 1, 10, 11, 12, 13, 24, 45, 57, 68 or 78; andI l la HCDR3 that is an HCDR3 in any one of SEQ ID NO: 1 , 10, 1 1 , 12, 13, 24, 45, 57, 68 or 78.3. The antigen binding construct of arrangement 1 or 2, wherein the antigen binding construct is an antibody.4. A minibody that binds to DLL3, the minibody comprising: a single-chain variable fragment (scFv) that binds to DLL3, the scFv comprising a variable light (VL) domain linked to a variable heavy (VH) domain, the VL domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85; and the VH domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82; a hinge-extension domain comprising a hinge region; and a CH3 domain.5. An antigen binding construct comprising: a VL domain comprising: a LCDR1 that is of SEQ ID NO: 6; a LCDR2 that is of SEQ ID NO: 7; a LCDR3 that is of SEQ ID NO: 8; and a VH domain comprising: a HCDR1 that is any one of SEQ ID NO: 3 or 18; a HCDR2 that is of SEQ ID NO: 4; and a HCDR3 that is any one of SEQ ID NO: 5 or 19; a hinge-extension domain comprising a hinge region; and a CH3 domain.6. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the VH domain comprises an amino acid sequence having at least 90% identity to a VH domain in any one of SEQ ID NO: 1, 9, 10, 11, 12 or 13.7. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the antigen binding construct or minibody, comprises a T25S, Y27G, R28T and / or C95S mutation (Kabat).8. An antigen binding construct comprising: a VL domain comprising: a LCDR1 that is of SEQ ID NO: 29; a LCDR2 that is of SEQ ID NO: 30; a LCDR3 that is any one of SEQ ID NO: 31 or 32; and a VH domain comprising: a HCDR1 that is of SEQ ID NO: 26; a HCDR2 that is of SEQ ID NO: 27; and a HCDR3 that is of SEQ ID NO: 28, a hinge-extension domain comprising a hinge region; and a CH3 domain.9. The antigen binding construct or minibody of any one of arrangements 1 to 4 or 8, wherein the VL domain comprises an amino acid sequence having at least 90% identity to a VL domain of SEQ ID NO: 25.10. The antigen binding construct or minibody of any one of arrangements 1 to 4, 8, or 9, wherein the antigen binding construct or minibody, comprises a D93N mutation (Kabat).11. An antigen binding construct comprising: a VL domain comprising: a LCDR1 that is of SEQ ID NO: 50; a LCDR2 that is of SEQ ID NO: 51 ; a LCDR3 that is of SEQ ID NO: 52; and a VH domain comprising: a HCDR1 that is of SEQ ID NO: 47; a HCDR2 that is of SEQ ID NO: 48; and a HCDR3 that is of SEQ ID NO: 49; a hinge-extension domain comprising a hinge region; and a CH3 domain.12. An antigen binding construct comprising:a VL domain comprising: a LCDR1 that is of SEQ ID NO: 63; a LCDR2 that is of SEQ ID NO: 64; a LCDR3 that is of SEQ ID NO: 65; and a VH domain comprising: a HCDR1 that is of SEQ ID NO: 59; a HCDR2 that is of SEQ ID NO: 60; and a HCDR3 that is any one of SEQ ID NO: 61 or 62; a hinge-extension domain comprising a hinge region; and a CH3 domain.13. The antigen binding construct or minibody of any one of the arrangements 1 to 4 or 12, wherein the VH domain comprises an amino acid sequence having at least 90% identity to a VH domain of SEQ ID NO: 57.14. The antigen binding construct or minibody of any one of the arrangements 1 to 4, 12 or 13, wherein the antigen binding construct or minibody, comprises a K94R mutation (Kabat).15. An antigen binding construct comprising: a VL domain comprising: a LCDR1 that is of SEQ ID NO: 73; a LCDR2 that is of SEQ ID NO: 74; a LCDR3 that is of SEQ ID NO: 75; and a VH domain comprising: a HCDR1 that is of SEQ ID NO: 70; a HCDR2 that is of SEQ ID NO: 71; and a HCDR3 that is of SEQ ID NO: 72; a hinge-extension domain comprising a hinge region; and a CH3 domain.16. An antigen binding construct comprising: a single-chain variable fragment (scFv) that binds to DLL3, the scFv comprising a variable light (VL) domain linked to a variable heavy (VH) domain, the VL domain comprising: a LCDR1 that is of SEQ ID NO: 83;a LCDR2 that is of SEQ ID NO: 84; a LCDR3 that is of SEQ ID NO: 85; and a VH domain comprising: a HCDR1 that is of SEQ ID NO: 80; a HCDR2 that is of SEQ ID NO: 81; and a HCDR3 that is of SEQ ID NO: 82; a hinge-extension domain comprising a hinge region; and a CH3 domain.17. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the antigen binding construct or minibody, further comprises a signal peptide that is SEQ ID NO: 158.18. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the antigen binding construct or minibody, comprises a linker that is any one of SEQ ID NO: 159-164.19. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the CH3 domain is an IgG CH3 domain.20. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the IgG CH3 domain is an IgGl, IgG2, IgG3, or IgG4 CH3 domain.21. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the IgG CH3 domain comprises an IgGl CH3 domain that is any one of SEQ ID NO: 202-205.22. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the IgG CH3 domain comprises an IgGl CH3 domain that is any one of SEQ ID NO: 206-208.23. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the IgG CH3 domain comprises an IgGl CH3 domain that is any one of SEQ ID NO: 209-229.24. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the IgG CH3 domain comprises an IgGl CH3 domain that is any one of SEQ ID NO: 220-222.25. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the antigen binding construct or minibody, binds specifically to DLL3.26. The antigen binding construct or minibody of any one of the preceding arrangements, further comprising a detectable marker.27. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker is a fluorescently detectable marker.28. A minibody comprising an amino acid sequence of any one of SEQ ID NO: 110- 135 (with or without the signal sequence), or a sequence at least 90% identical thereto.29. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker comprises a phototherapy compatible dye.30. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker comprises boron.31. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker is compatible for use with Boron Neutron Capture therapy (BNCT).32. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker is a radiolabel.33. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker is an alpha-emitter radiolabel.34. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker is a beta-emitter radiolabel.35. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker is a positron-emitter radiolabel.36. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker comprises Lutetium-177.37. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker is a gamma-emitter radiolabel.38. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker is suitable for use with Auger electron spectroscopy.39. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker comprises an isotope.40. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker comprises a bioluminescent compound.41. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker comprises a chemiluminescent compound.42. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker comprises an enzyme.43. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the detectable marker comprises a metal chelator.44. The antigen binding construct or minibody of any one of the preceding arrangements, further comprising a therapeutic agent.45. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the therapeutic agent comprises a therapeutic isotope or ion.46. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the therapeutic agent is a radiolabel.47. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the therapeutic agent is an alpha-emitter radiolabel.48. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the therapeutic agent is a beta-emitter radiolabel.49. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the therapeutic agent is a positron-emitter radiolabel.50. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the therapeutic agent is a gamma-emitter radiolabel.51. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the therapeutic agent comprises Lutetium-177.52. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the therapeutic agent comprises a phototherapy compatible dye.53. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the therapeutic agent comprises boron.54. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the therapeutic agent is compatible for use with Boron Neutron Capture therapy (BNCT).55. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the therapeutic agent and / or detectable marker comprise a toxic pay load.56. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the antigen binding construct or minibody, is bispecific.57. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the antigen binding construct or minibody comprises a monovalent scFv.58. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the order of the variable domains, from N terminus to C terminus of the polypeptide is VL, VH.59. The antigen binding construct or minibody of any one of arrangements 1-58, wherein the order of the variable domains, from N terminus to C terminus of the polypeptide is VH, VL.60. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the minibody is a humanized antigen binding construct or minibody.61. The antigen binding construct or minibody of arrangement 60, wherein the subject is a mammal, optionally wherein the subject is a human.62. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the antigen binding construct or minibody, has an EC50 of about 0.001, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 2, 2.1, 2.2, 2.3, 2.4 , 2.5 or 3 nM.63. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the antigen binding construct or minibody, has an EC50 of between about 0.001 and 3 nM, 0.001 and 0.17 nM, 0.001 and 0.12 nM, 0.01 and 0.20 nM, 0.01 and 0.17 nM, 0.01 and 0.12 nM, 0.05 and 0.20 nM, 0.05 and 0.17 nM. 0.05 and 0.15 nM, 0.05 and 0.12 nM, 0.08 and 0.20 nM, 0.08 and 0.17 nM, 0.08 and 0.12 nM, 0.12 and O.22nM, 0.14 and 0.18nM, 0.3 and 0.4nM, 0.5 and InM, 1 and 1.4nM, 1.1 and 2.1nM, or 1.5 and 2.5nM.64. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the antigen binding construct or minibody, has an EC50 of up to about 10 nM.65. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the LCDR1 is or comprises SEQ ID NO:29, the LCDR2 is or comprises SEQ ID NO:30, and the LCDR3 is or comprises SEQ ID NO:31 or 32, optionally wherein the LCDR3 is or comprises SEQ ID NO:31.66. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the VL domain comprises: the LCDR1 that is the LCDR1 in SEQ ID NO:25, the LCDR2 that is the LCDR2 in SEQ ID NO:25; and the LCDR3 that is the LCDR3 in SEQ ID NO:25 or 40, optionally wherein the LCDR3 is the LCDR3 in SEQ ID NO:25.67. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the HCDR1 is or comprises SEQ ID NO:26, the HCDR2 is or comprises SEQ ID NO:27, the HCDR3 is or comprises SEQ ID NO:28.68. The antigen binding construct or minibody of any one of the preceding arrangements, wherein the VH domain comprises: the HCDR1 that is the HCDR1 in SEQ ID NO:24, the HCDR2 that is the HCDR2 in SEQ ID NO:24; and the HCDR3 that is the HCDR3 in SEQ ID NO:24.69. The antigen binding construct or minibody of any one of arrangements 65-68, wherein the VL domain comprises a sequence of the VL domain in any one of SEQ ID NOs: 25 and 33-44, or a sequence at least 90% identical thereto.70. The antigen binding construct or minibody of any one of arrangements 65-69, wherein the VL domain comprises a sequence of the VL domain in SEQ ID NO: 33, or a sequence at least 90% identical thereto.71. The antigen binding construct or minibody of any one of arrangements 65-70, wherein the VH domain comprises a sequence of the VH domain in any one of SEQ ID NOs:24 and 33-44, or a sequence at least 90% identical thereto.72. The antigen binding construct or minibody of any one of arrangements 65-71 , wherein the VH domain comprises a sequence of the VH domain in SEQ ID NO: 33, or a sequence at least 90% identical thereto.73. The antigen binding construct or minibody of any one of the preceding arrangements, comprising an scFv comprising the sequence of any one of SEQ ID NOs: 25 and 33-44 (with or without the signal sequence), or a sequence at least 90% identical thereto.74. The antigen binding construct or minibody of arrangement 73, wherein the scFv comprises the sequence of SEQ ID NO:33 (with or without the signal sequence), or a sequence at least 90% identical thereto.75. The antigen binding construct or minibody of any one of the preceding arrangements, comprising the sequence of any one of SEQ ID NOs: 114- 125 (with or without the signal sequence), or a sequence at least 90% identical thereto.76. The antigen binding construct or minibody of arrangement 75, comprising the sequence of SEQ ID NO: 114 (with or without the signal sequence), or a sequence at least 90% identical thereto.77. A nucleic acid encoding an antigen binding construct or minibody of any one of the preceding arrangements.78. A cell line producing an antigen binding construct or minibody of any one of the preceding arrangements.79. A cell line producing an antigen binding construct or minibody, of any one of the preceding arrangements.80. A kit comprising: an antigen binding construct or minibody, of any one of the preceding arrangements; and a detectable marker.81. A kit comprising: an antigen binding construct or minibody, of any one of the preceding arrangements; and a chelator, wherein the chelator allows incorporation of a detectable marker.82. A kit comprising: an antigen binding construct or minibody, of any one of the preceding arrangements; and a chelator, wherein the chelator allows incorporation of a therapeutic isotope.83. A kit comprising: an antigen binding construct or minibody, of any one of the preceding arrangements; and a linker, wherein the linker allows incorporation of a detectable marker.84. A kit comprising: an antigen binding construct or minibody, of any one of the preceding arrangements; and a linker, wherein the linker allows incorporation of a therapeutic isotope.85. A kit comprising: an antigen binding construct or minibody, of any one of the preceding arrangements; and a detectable marker.86. A method of detecting a presence or absence of a DLL3, the method comprising: applying the antigen binding construct or minibody, of any of the preceding arrangements to a sample; and detecting a presence or an absence of the antigen binding construct or minibody, thereby detecting a presence or absence of a DLL3.87. The method of arrangement 86, wherein the antigen binding construct or minibody, is conjugated to a detectable marker.88. The method of arrangement 86 or 87, wherein applying the antigen binding construct or minibody, comprises administering the antigen binding construct to a subject.89. The method of any one of arrangements 86-88, wherein detecting the presence or absence of binding of the antigen binding construct or minibody comprises at least one of positron emission tomography or single-photon emission computed tomography.90. The method of any one of arrangements 86-89, the method further comprising applying a secondary antigen binding construct to the sample, wherein the secondary antigen binding construct binds specifically to the antigen binding construct.91. The method of any one of arrangements 86-90, wherein the antigen binding construct or minibody, is incubated with the sample for no more than 20 hours.92. The method of any one of arrangements 86-91, wherein the antigen binding construct or minibody, is incubated with the sample for no more than 6 hours.93. The method of any one of arrangements 86-92, wherein the antigen binding construct or minibody, is administered to a host, and wherein a first quantity of antigen binding construct or minibody, thereof is unbound to DLL3, and a second quantity of antigen bindingconstruct or minibody, is bound to DLL3, wherein at least about 80% of the first quantity of antigen binding construct or minibody, is eliminated in no more than 12 hours.94. A method of targeting a therapeutic agent to DLL3, the method comprising administering to a subject an antigen binding construct or minibody, of any one of the preceding arrangements, wherein the antigen binding construct is conjugated to a therapeutic agent.95a. A therapeutic composition targeting DLL3, wherein the therapeutic composition comprises the antigen binding construct or the minibody of any one of arrangements 1-76.95b. A therapeutic composition targeting DLL3, wherein the therapeutic composition comprises: an antigen binding construct that comprises: a variable light (VL) domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85; a variable heavy (VH) domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82; and a therapeutic agent, toxic payload, and / or a detectable marker.96. A therapeutic composition targeting DLL3, wherein the therapeutic composition comprises: a minibody that binds to DLL3, the minibody comprising: a single-chain variable fragment (scFv) that binds to DLL3, the scFv comprising a variable light (VL) domain linked to a variable heavy (VH) domain, the VL domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85; the VH domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82;a hinge-extension domain comprising a IgGl hinge region; a IgG CH3 sequence; and a therapeutic agent, toxic payload, and / or a detectable marker.97. A therapeutic composition targeting DLL3, wherein the therapeutic composition comprises a minibody that binds to DLL3, the minibody comprising any one of SEQ ID NO:110-135 (with or without the signal sequence), or a sequence at least 85% identical thereto.98. A therapeutic composition targeting DLL3, wherein the therapeutic composition comprises: a cys-diabody that binds to DLL3, the cys-diabody comprising a polypeptide that comprises: a single-chain variable fragment (scFv) comprising a variable light (VL) domain linked to a variable heavy (VH) domain; the VL domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85; the VH domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82; and a therapeutic agent, toxic payload, and / or a detectable marker.99. The therapeutic composition of any of the preceding arrangements, wherein the detectable marker is a radiolabel.100. The therapeutic composition of any of the preceding arrangements, wherein the detectable marker is an alpha-emitter radiolabel.101. The therapeutic composition of any of the preceding arrangements, wherein the detectable marker is a beta-emitter radiolabel.102. The therapeutic composition of any of the preceding arrangements, wherein the detectable marker is a positron-emitter radiolabel.103. The therapeutic composition of any of the preceding arrangements, wherein the detectable marker comprises Lutetium-177.104. The antigen binding construct or minibody of any one of the preceding arrangements, or the composition of any one of the preceding arrangements, or the kit of any one of the preceding arrangements, or the method of any one of the preceding arrangements, wherein the therapeutic agent comprises Terbium-149, Terbium-161, or Lead-212.105. The antigen binding construct of any one of the preceding arrangements, or the composition of any one of the preceding arrangements, or the kit of any one of the preceding arrangements, or the method of any one of the preceding arrangements, wherein the antigen binding construct is an scFv-Fc comprising: a single-chain variable fragment (scFv) that binds to DLL3, the scFv comprising the variable light (VL) domain linked to the variable heavy (VH) domain; a hinge domain; and an Fc region.106. An antigen binding construct that binds DLL3, wherein the antigen binding construct is a nanobody®-Fc that binds DLL3 and comprises a variable heavy (VH) domain linked to a Fc region via a hinge domain.107. The antigen binding construct of arrangement 106, wherein the variable heavy (VH) domain comprises: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82.108. The antigen binding construct of arrangement 107, wherein the HCDR1 is or comprises SEQ ID NO:26, the HCDR2 is or comprises SEQ ID NO:27, the HCDR3 is or comprises SEQ ID NO:28.109. The antigen binding construct of arrangement 107 or 108, wherein the VH domain comprises: the HCDR1 that is the HCDR1 in SEQ ID NO:24, the HCDR2 that is the HCDR2 in SEQ ID NO:24; and the HCDR3 that is the HCDR3 in SEQ ID NO:24.110. The antigen binding construct of any one of arrangements 107-109, wherein the VH domain comprises a sequence of the VH domain in any one of SEQ ID NOs:24 and 33-44, or a sequence at least 90% identical thereto.111. The antigen binding construct of any one of arrangements 107-110, wherein the VH domain comprises a sequence of the VH domain in SEQ ID NO: 33, or a sequence at least 90% identical thereto.112. The antigen binding construct, nucleic acid, cell line, kit, composition or method of any one of the preceding arrangements, wherein the antigen binding construct or minibody comprises the HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3 sequences of the corresponding HCDR and LCDR sequences, or sequences at least 90% identical thereto respectively, in any one of the antigen binding constructs depicted in any one of Figs. 1-6 and in the arrangement of the HCDR and LCDR sequences as set forth in the any one of Figs. 1-6, or set forth in any one of Tables 1-6 and in the arrangement of the HCDR and LCDR sequences as set forth in the any one of Tables 1-6.113. The antigen binding construct, nucleic acid, cell line, kit, composition or method of any one of the preceding arrangements, wherein the antigen binding construct or minibody comprises the VH and VL sequences of the corresponding VH and VL sequences, or sequences at least 80% identical thereto respectively, in any one of the antigen binding constructs depicted in Figs. 1-6 and in the arrangement of the VH and VL sequences as set forth in the Figs. 1-6, or set forth in Table 11 and in the arrangement of the VH and VL sequences as set forth in the Table 11.114. The antigen binding construct, nucleic acid, cell line, kit, composition or method of any one of the preceding arrangements, wherein the antigen binding construct or minibody comprises the sequence, or a sequence at least 80% identical thereto, of any one of the antigen binding constructs depicted in Figs. 1-6, or set forth in Table 12.

[0198] Embodiments of the present disclosure are further defined in the following Examples. It should be understood that these Examples are given by way of illustration only. From the above discussion and these Examples, one skilled in the art can ascertain the essential characteristics of the present disclosure, and without departing from the spirit and scope thereof, can make various changes and modifications of the embodiments of the disclosure to adapt it to various usages and conditions. Thus, various modifications of the embodiments of the disclosure, in addition to those shown and described herein, will be apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of theappended claims. The disclosure of each reference set forth herein is incorporated herein by reference in its entirety, and for the disclosure referenced herein.EXAMPLESExample 1: Isolation and characterization of novel antigen binding constructs

[0199] The isolation of a series of novel antigen binding constructs as described herein can also be performed using any standard methodology known to one skilled in the art.

[0200] As disclosed herein, a series of antigen binding constructs specific against DLL3 were designed and isolated. DLL3 binding clones were generated by immunization in mice and hybridoma fusions, followed by humanization (FIGs. 1-6). Each antigen binding construct was either human or murine, and either an antibody or a minibody. In one example, the variable region from a parental antibody was converted to a scFv and engrafted in a minibody scaffold. In another example, the variable region from a parental antibody tested for immunogenic epitopes through in-silico methods known in the art, converted to a scFv and engrafted in a minibody scaffold. Furthermore, each construct comprised a heavy chain and light chain, with a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82; a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84 and a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85.

[0201] Clone 9B6 construct (murine or humanized) comprised a heavy chain and light chain, with a HCDR1 that is any of SEQ ID NO: 3 or 18; a HCDR2 that is of SEQ ID NO: 4; a HCDR3 that is any one of SEQ ID NO: 5 or 19; a LCDR1 that is of SEQ ID NO: 6; a LCDR2 that is of SEQ ID NO: 7 and a LCDR3 that is of SEQ ID NO: 8 as illustrated in FIG. 1.

[0202] Clone 3H2 construct (murine or humanized) comprised a heavy chain and light chain, with a HCDR1 that is of SEQ ID NO: 26; a HCDR2 that is of SEQ ID NO: 27; a HCDR3 that is of SEQ ID NO: 28; a LCDR1 that is of SEQ ID NO: 29; a LCDR2 that is of SEQ ID NO: 30 and a LCDR3 that is any one of SEQ ID NO: 31 or 32 as illustrated in FIG. 2.

[0203] Clone 5C5 construct (murine or humanized) comprised a heavy chain and light chain, with a HCDR1 that is of SEQ ID NO: 47; a HCDR2 that is of SEQ ID NO: 48; a HCDR3that is of SEQ ID NO: 49; a LCDR 1 that is of SEQ ID NO: 50; a LCDR2 that is of SEQ ID NO:51 and a LCDR3 that is of SEQ ID NO: 52 as illustrated in FIG. 3.

[0204] Clone 1D1 construct (murine or humanized) comprised a heavy chain and light chain, with a HCDR1 that is of SEQ ID NO: 59; a HCDR2 that is of SEQ ID NO: 60; a HCDR3 that is any one of SEQ ID NO: 61 or 62; a LCDR1 that is of SEQ ID NO: 63; a LCDR2 that is of SEQ ID NO: 64 and a LCDR3 that is of SEQ ID NO: 65 as illustrated in FIG. 4.

[0205] Clone 11C9 construct (murine or humanized) comprised a heavy chain and light chain, with a HCDR1 that is of SEQ ID NO: 70; a HCDR2 that is of SEQ ID NO: 71; a HCDR3 that is of SEQ ID NO: 72; a LCDR1 that is of SEQ ID NO: 73; a LCDR2 that is of SEQ ID NO:74 and a LCDR3 that is of SEQ ID NO: 75 as illustrated in FIG.5.

[0206] Clone 13C3 construct (murine or humanized) comprised a heavy chain and light chain, with a HCDR1 that is of SEQ ID NO: 80; a HCDR2 that is of SEQ ID NO: 81; a HCDR3 that is of SEQ ID NO: 82; a LCDR1 that is of SEQ ID NO: 83; a LCDR2 that is of SEQ ID NO: 84 and a LCDR3 that is of SEQ ID NO: 85 as illustrated in FIG.6.

[0207] These antigen binding constructs were then transfected into Expi293™ cell-line using a liposome transfection protocol (Thermo Exp293 kit). The vector contained a cleavable signal peptide (or signal sequence) METDTLLLWVLLLWVPGSTG (SEQ ID NO: 158). In other alternatives, the sequence of the antigen binding constructs can be inserted into any cell line using any conventional method, such as electroporation.

[0208] The half-maximal effective concentration (ECso, in nM) was assessed by ELISA and flow cytometry (FIGS. 7-15).

[0209] Binding affinity of the novel antigen binding constructs to a purified human DLL3 antigen was assessed using ELISA (FIG. 7). For this assay, a 96 well ELISA plate was coated with the DLL3 antigen diluted to a concentration of 2mg / mL in coating buffer (0.05M sodium carbonate -bicarbonate buffer, pH 9.6). lOOpl of this coating solution was added to each well in the plate and incubate at 4°C overnight. The plate was washed 3 times with 300pl per well of washing buffer (PBS with 0.05% Tween-20). After the last wash, the plate was blocked by adding to each well 200pl of blocking buffer (PBS with 1% BSA) warmed to room temperature. The plate was then incubated at room temperature for 1 hour under gentle agitation. After blocking, the plate was washed 3 times with 300p I per well of washing buffer. Dilution samples for each minibody were created by making 2.5X dilutions from a starting sample at lOOng / mL, or250ng / mL, or 1000ng / mL or 3000ng / mL in lOOpL sample buffer (PBS with 1 % BSA). The dilution samples were transferred to the assay plate and incubated at room temperature for 1 hour under gentle agitation. The plate was then washed 3 times with 300p I per well of washing buffer.

[0210] Detection was performed by adding lOOpl of HRP labeled detection secondary antibody at an appropriate dilution and incubating the plate at room temperature for 1 hour under gentle agitation. The plate was then washed 3 times with 300pl per well of washing buffer. For color development, lOOpl of TMB substrate regent, pre-warmed to room temperature, was added to the plate and incubated in the dark at room temperature for 15 min. The reaction was then stopped by adding lOOpl of 650nm stop solution to the plate and mixed for 1 min at room temperature under gentle agitation. The plate is recorded by reading OD at 650nm in a plate reader within 20min after terminating the reaction.

[0211] The humanized minibodies showed comparable or lower ECso values (in nM) for binding to human DLL3 as determined by ELISA compared to the parental antibodies (FIGs. 8, 9, 11-13, 15).

[0212] As disclosed herein, the binding of constructs to cellular targets was assessed using flow cytometry. Stock of 2.5X serial dilution of minibodies were created starting from a concentration of lOOnM in 150 pl FACS buffer (PBS 2% FBS). Cells were added to a Corning V- bottom polypropylene cell culture plate at 100,000 cells / well. The cells were centrifuged at lOOOrpm for 3 minutes and the supernatant discarded. The minibody dilution series were transferred to the plate containing cell pellets and incubated for Ihr at 4°C. The plate was then washed 3 times with FACS buffer at 200 pl / well, discarding supernatant after each wash by centrifugation at lOOOrpm. 100 p Ewell of detection APC-mouse anti-human IgG (SouthernBiotech) was added at a 1:1000 dilution in FACS buffer and incubated at 4oC Ihr. The plate was washed 2 times with FACS buffer at 200 pl / well, discarding supernatant after each wash by centrifuging at lOOOrpm. The plate was washed a final time with PBS at 200pl / well, discarding supernatant by centrifuging at lOOOrpm. Cells were then fixed by adding lOOpl of 1% paraformaldehyde in PBS and incubated at room temperature for 15 minutes. 100 pl of PBS was added to each well and the plate was analyzed by flow cytometry using the allophycocyanin fluorescence setting.

[0213] ECso (in nM) for binding to cells expressing DLL3 was determined by flowcytometry (FIGs. 10, 14).Example 2: Use of the antigen binding constructs for treatment of a subject in need thereof

[0214] The methods of utilizing the novel antigen binding constructs described herein as a medicament to a subject in need thereof may confer a benefit to the subject.

[0215] As disclosed herein, a pharmaceutical composition is made comprising a novel antigen binding construct against DLL3, alone or in combination with a chemotherapy, or an immuno-oncology drug, or a DNA repair inhibitor, and a pharmaceutically acceptable carrier. In other alternatives, the dosage is a radioactive dose. In other alternatives, the dosage is not fixed. In other alternatives, the dosage is provided as fractionated doses. In other alternatives, the dosage is measured in mCi or MBq. In other alternatives, the composition can have more than one antigen binding construct. In other alternatives, the antigen binding construct can be an antibody or minibody, or another combination thereof. In other alternatives, the antigen binding construct may be present in the composition at any pharmaceutically effective concentration, such as about 0.01 mg / kg to about 25 mg / kg. In other alternatives, the immuno-oncology drug may be omitted from the composition. In other alternatives, the immuno-oncology drug may be replaced by one or more small molecule, therapeutic, or antigen binding construct effective in treating a disease, such as an antibody, a chemotherapy drug, a DNA repair inhibitor, an alkylating agent, a metabolic inhibitor, a radiosensitizer agent, an anti-tumor antibiotic, a topoisomerase inhibitor, a mitotic inhibitor, a nitrosourea, a corticosteroid, an anti-angiogenic, an apoptosis inducer, an anti-microtubule agent, a vinca alkaloid, a taxane, an anthracycline, an anti-androgen, a VEGF pathway inhibitor, a VEGF pathway inhibitor, a MAPK / Ras / Raf pathway inhibitor, and an EGFR pathway inhibitor.

[0216] The compositions of the invention may be employed in combination therapies with other agents to achieve an improved therapeutic outcome for the subject. The other agents which may be employed in combination include therapeutic agents, immunotherapeutic agents, chemotherapeutic agents, radioprotective agents and kidney protecting agents. Immunotherapeutic agents useful in combination with the invention include Atezolizumab (Tecentriq), Avelumab (Bavencio), Dostarlizumab (Jemperli), Durvalumab (Imfinzi), Ipilimumab (Yervoy), Nivolumab (Opdivo), Pcmbrolizumab (Kcytruda), and other immunotherapeutic agents in clinical development.

[0217] As disclosed herein, the composition is administered to a human subject at a pharmaceutically acceptable dose for treating SCLC. In other alternatives, the disease may be otherneuroendocrine tumors such as, neuroendocrine prostate cancer, glioblastoma, fibrosis, cancer, a tumor, a solid tumor, an autoimmune disease, cardiovascular disease, metabolic disease, bone cancer, bone sarcoma, breast cancer, carcinoid, cervical cancer, colon cancer, colorectal cancer, endometrial carcinoma, epithelial ovarian cancer, esophageal cancer, gastric cancer, gastrointestinal cancer, glioma, head and neck cancer, hepatocellular cancer, kidney cancer, leukemia, liver cancer, lung cancer, lymphoma, medullary thyroid carcinoma, melanoma, nonsmall cell lung cancer, osteosarcoma, oral squamous cell carcinoma, oral cancer, ovarian carcinoma, ovarian cancer, pancreatic adenocarcinoma, pancreatic cancer, prostate cancer, rectal cancer, renal cancer, skin cancer, stomach cancer, testis cancer, thyroid cancer, urothelial cancer, or any other disease associated with changing DLL3 expression. In other alternatives, the composition is administered to a subject for inhibiting or ameliorating the disease.

[0218] After administration, the disease is monitored through the imaging of relevant cells, tissues, or organs in the subject using the method outlined in the example below. As seen through the imaging, the cancer cells are damaged following administration of the composition to the subject. In other alternatives, the cancer cell is inhibited, ameliorated, damaged, killed, or has induced apoptosis in response to contact with the composition.Example 3: Use of the antigen binding constructs for diagnostics

[0219] The methods of utilizing the novel antigen binding constructs described herein for diagnostics thereof may confer a benefit to a subject suspected of having a disease.

[0220] As disclosed herein, the novel antigen binding construct is used for imaging the tissue of a human subject suspected of having cancer. In other alternatives, the antigen binding constructs can be used for imaging a cell, cultured cell line, fraction of tissue, organ, organ sectional, multi-tissue, multi-organ, or whole subject. In other alternatives, the subject can be screened for a tumor, fibrosis, autoimmune disease, cardiovascular disease, or any other disease or abnormality associated with DLL3. In other alternatives, the subject can be any mammal, including mice, rats, dogs, minipig and non-human primates.

[0221] The antigen binding construct is administered to the epithelial tissue of a subject and screened for binding to DLL3. The subject is evaluated for the presence of DLL3 by methods of in-vivo diagnostic medical imaging such as, positron emission tomography (PET), or Singlephoton emission computed tomography (SPECT). The binding of the antigen binding construct toDLL3 indicates a high likelihood for the presence of cancer in the tissue. In other alternatives, the absence of binding of the antigen binding construct to DLL3 indicates a low likelihood for the presence of cancer in the tissue. In other alternatives, the binding of the antigen binding construct to DLL3 is determined by a payload added to the antigen binding construct, such as18F,18F-FAC,010 010 000 007 00Pb, Bi, Ra, Th or Ac. In other alternatives, the binding of the antigen binding construct to DLL3 is determined through a PET scan.

[0222] As used herein, the section headings are for organizational purposes only and are not to be construed as limiting the described subject matter in any way. All literature and similar materials cited in this application, including but not limited to, patents, patent applications, articles, books, treatises, and internet web pages are expressly incorporated by reference in their entirety for any purpose, including the disclosures specifically referenced herein. When definitions of terms in incorporated references appear to differ from the definitions provided in the present teachings, the definition provided in the present teachings shall control. It will be appreciated that there is an implied “about” prior to the temperatures, concentrations, times, etc. discussed in the present teachings, such that slight and insubstantial deviations are within the scope of the present teachings herein.

[0223] Although this disclosure has been presented in the context of certain embodiments and examples, those skilled in the art will understand that the present disclosure extends beyond the specifically disclosed embodiments to other alternative embodiments and / or uses of the disclosure and obvious modifications and equivalents thereof. In addition, while several variations of the present disclosure have been shown and described in detail, other modifications, which are within the scope of this disclosure, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the present disclosure. It should be understood that various features and aspects of the disclosed embodiments can be combined with, or substituted for, one another in order to form varying modes or embodiments of the present disclosure. Thus, it is intended that the scope of the presentdisclosure herein presented should not be limited by the particular disclosed embodiments described above.

[0224] It should be understood, however, that this detailed description, while indicating preferred embodiments of the disclosure, is given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art.

[0225] The terminology used in the description presented herein is not intended to be interpreted in any limited or restrictive manner. Rather, the terminology is simply being utilized in conjunction with a detailed description of embodiments of the systems, methods and related components. Furthermore, embodiments may comprise several novel features, no single one of which is solely responsible for its desirable attributes or is believed to be essential to practicing the disclosures herein described.

Claims

WHAT IS CLAIMED IS:

1. An antigen binding construct comprising: a variable light (VL) domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85; and a variable heavy (Vn) domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82.

2. An antigen binding construct comprising: a variable light (VL) domain comprising: a LCDR1 that is an LCDR1 in any one of SEQ ID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69 or 79; a LCDR2 that is an LCDR2 in any one of SEQ ID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69 or 79; a LCDR3 that is an LCDR3 in any one of SEQ ID NO: 2, 14, 15, 16, 17, 25, 46, 58, 69 or 79; and a variable heavy (VH) domain comprising: a HCDR1 that is an HCDR1 in any one of SEQ ID NO:1, 10, 11, 12, 13, 24, 45, 57, 68 or 78; a HCDR2 that is an HCDR2 in any one of SEQ ID NO: 1, 10, 11, 12, 13, 24, 45, 57, 68 or 78; and a HCDR3 that is an HCDR3 in any one of SEQ ID NO: 1, 10, 11, 12, 13, 24, 45, 57, 68 or 78.

3. The antigen binding construct of claim 1 or 2, wherein the antigen binding construct is an antibody.

4. A minibody that binds to DLL3, the minibody comprising:a single-chain variable fragment (scFv) that binds to DLL3, the scFv comprising a variable light (VL) domain linked to a variable heavy (VH) domain, the VL domain comprising: a LCDR1 that is any one of SEQ ID NO: 6, 29, 50, 63, 73, or 83; a LCDR2 that is any one of SEQ ID NO: 7, 30, 51, 64, 74, or 84; a LCDR3 that is any one of SEQ ID NO: 8, 31, 32, 52, 65, 75, or 85; and the Vn domain comprising: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27, 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82; a hinge-extension domain comprising a hinge region; and a CH3 domain.

5. An antigen binding construct comprising: a VL domain comprising: a LCDR1 that is of SEQ ID NO: 6; a LCDR2 that is of SEQ ID NO: 7; a LCDR3 that is of SEQ ID NO: 8; and a VH domain comprising: a HCDR1 that is any one of SEQ ID NO: 3 or 18; a HCDR2 that is of SEQ ID NO: 4; and a HCDR3 that is any one of SEQ ID NO: 5 or 19; a hinge-extension domain comprising a hinge region; and a CH3 domain.

6. The antigen binding construct or minibody of any one of the preceding claims, wherein the VH domain comprises an amino acid sequence having at least 90% identity to a VH domain in any one of SEQ ID NO: 1, 9, 10, 11, 12 or 13.

7. The antigen binding construct or minibody of any one of the preceding claims, wherein the antigen binding construct or minibody, comprises a T25S, Y27G, R28T and / or C95S mutation (Kabat).

8. An antigen binding construct comprising: a VL domain comprising:a LCDR1 that is of SEQ ID NO: 29; a LCDR2 that is of SEQ ID NO: 30; a LCDR3 that is any one of SEQ ID NO: 31 or 32; and a VH domain comprising: a HCDR1 that is of SEQ ID NO: 26; a HCDR2 that is of SEQ ID NO: 27; and a HCDR3 that is of SEQ ID NO: 28; a hinge-extension domain comprising a hinge region; and a CH3 domain.

9. The antigen binding construct or minibody of any one of claims 1 to 4 or 8, wherein the VL domain comprises an amino acid sequence having at least 90% identity to a VL domain of SEQ ID NO: 25.

10. The antigen binding construct or minibody of any one of claims 1 to 4, 8, or 9, wherein the antigen binding construct or minibody, comprises a D93N mutation (Kabat).

11. An antigen binding construct comprising: a VL domain comprising: a LCDR1 that is of SEQ ID NO: 50; a LCDR2 that is of SEQ ID NO: 51; a LCDR3 that is of SEQ ID NO: 52; and a VH domain comprising: a HCDR1 that is of SEQ ID NO: 47; a HCDR2 that is of SEQ ID NO: 48; and a HCDR3 that is of SEQ ID NO: 49; a hinge-extension domain comprising a hinge region; and a CH3 domain.

12. An antigen binding construct comprising: a VL domain comprising: a LCDR1 that is of SEQ ID NO: 63; a LCDR2 that is of SEQ ID NO: 64; a LCDR3 that is of SEQ ID NO: 65; and a VH domain comprising:a HCDR1 that is of SEQ ID NO: 59; a HCDR2 that is of SEQ ID NO: 60; and a HCDR3 that is any one of SEQ ID NO: 61 or 62; a hinge-extension domain comprising a hinge region; and a CH3 domain.

13. The antigen binding construct or minibody of any one of the claims 1 to 4 or 12, wherein the Vn domain comprises an amino acid sequence having at least 90% identity to a VH domain of SEQ ID NO: 57.

14. The antigen binding construct or minibody of any one of the claims 1 to 4, 12 or 13, wherein the antigen binding construct or minibody, comprises a K94R mutation (Kabat).

15. An antigen binding construct comprising: a VL domain comprising: a LCDR1 that is of SEQ ID NO: 73; a LCDR2 that is of SEQ ID NO: 74; a LCDR3 that is of SEQ ID NO: 75; and a VH domain comprising: a HCDR1 that is of SEQ ID NO: 70; a HCDR2 that is of SEQ ID NO: 71; and a HCDR3 that is of SEQ ID NO: 72; a hinge-extension domain comprising a hinge region; and a CH3 domain.

16. An antigen binding construct comprising: a single-chain variable fragment (scFv) that binds to DLL3, the scFv comprising a variable light (VL) domain linked to a variable heavy (VH) domain, the VL domain comprising: a LCDR1 that is of SEQ ID NO: 83; a LCDR2 that is of SEQ ID NO: 84; a LCDR3 that is of SEQ ID NO: 85; and a VH domain comprising: a HCDR1 that is of SEQ ID NO: 80; a HCDR2 that is of SEQ ID NO: 81 ; anda HCDR3 that is of SEQ ID NO: 82; a hingc-cxtcnsion domain comprising a hinge region; and a CH3 domain.

17. The antigen binding construct or minibody of any one of the preceding claims, wherein the antigen binding construct or minibody, further comprises a signal peptide that is SEQ ID NO: 158.

18. The antigen binding construct or minibody of any one of the preceding claims, wherein the antigen binding construct or minibody, comprises a linker that is any one of SEQ ID NO: 159-164.

19. The antigen binding construct or minibody of any one of the preceding claims, wherein the CH3 domain is an IgG CH3 domain.

20. The antigen binding construct or minibody of any one of the preceding claims, wherein the IgG CH3 domain is an IgGl, IgG2, IgG3, or IgG4 CH3 domain.

21. The antigen binding construct or minibody of any one of the preceding claims, wherein the IgG CH3 domain comprises an IgGl CH3 domain that is any one of SEQ ID NO: 202- 205.

22. The antigen binding construct or minibody of any one of the preceding claims, wherein the IgG CH3 domain comprises an IgGl CH3 domain that is any one of SEQ ID NO: 206- 208.

23. The antigen binding construct or minibody of any one of the preceding claims, wherein the IgG CH3 domain comprises an IgGl CH3 domain that is any one of SEQ ID NO: 209- 229.

24. The antigen binding construct or minibody of any one of the preceding claims, wherein the IgG CH3 domain comprises an IgGl CH3 domain that is any one of SEQ ID NO: 220- 222.

25. The antigen binding construct or minibody of any one of the preceding claim, wherein the antigen binding construct or minibody, binds specifically to DLL3.

26. The antigen binding construct or minibody of any one of the preceding claims, further comprising a detectable marker.

27. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker is a fluorescently detectable marker.

28. A minibody comprising an amino acid sequence of any one of SEQ ID NO: 110- 135 (with or without the signal sequence), or a sequence at least 90% identical thereto.

29. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker comprises a phototherapy compatible dye.

30. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker comprises boron.

31. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker is compatible for use with Boron Neutron Capture therapy (BNCT).

32. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker is a radiolabel.

33. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker is an alpha-emitter radiolabel.

34. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker is a beta-emitter radiolabel.

35. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker is a positron-emitter radiolabel.

36. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker comprises Lutetium- 177.

37. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker is a gamma-emitter radiolabel.

38. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker is suitable for use with Auger electron spectroscopy.

39. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker comprises an isotope.

40. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker comprises a bioluminescent compound.

41. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker comprises a chemiluminescent compound.

42. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker comprises an enzyme.

43. The antigen binding construct or minibody of any one of the preceding claims, wherein the detectable marker comprises a metal chelator.

44. The antigen binding construct or minibody of any one of the preceding claims, further comprising a therapeutic agent.

45. The antigen binding construct or minibody of any one of the preceding claims, wherein the therapeutic agent comprises a therapeutic isotope or ion.

46. The antigen binding construct or minibody of any one of the preceding claims, wherein the therapeutic agent is a radiolabel.

47. The antigen binding construct or minibody of any one of the preceding claims, wherein the therapeutic agent is an alpha-emitter radiolabel.

48. The antigen binding construct or minibody of any one of the preceding claims, wherein the therapeutic agent is a beta-emitter radiolabel.

49. The antigen binding construct or minibody of any one of the preceding claims, wherein the therapeutic agent is a positron-emitter radiolabel.

50. The antigen binding construct or minibody of any one of the preceding claims, wherein the therapeutic agent is a gamma-emitter radiolabel.

51. The antigen binding construct or minibody of any one of the preceding claims, wherein the therapeutic agent comprises Lutetium-177.

52. The antigen binding construct or minibody of any one of the preceding claims, wherein the therapeutic agent comprises a phototherapy compatible dye.

53. The antigen binding construct or minibody of any one of the preceding claims, wherein the therapeutic agent comprises boron.

54. The antigen binding construct or minibody of any one of the preceding claims, wherein the therapeutic agent is compatible for use with Boron Neutron Capture therapy (BNCT).

55. The antigen binding construct or minibody of any one of the preceding claims, wherein the therapeutic agent and / or detectable marker comprise a toxic payload.

56. The antigen binding construct or minibody of any one of the preceding claims, wherein the antigen binding construct or minibody, is bispecific.

57. The antigen binding construct or minibody of any one of the preceding claims, wherein the antigen binding construct or minibody comprises a monovalent scFv.

58. The antigen binding construct or minibody of any one of the preceding claims, wherein the order of the variable domains, from N terminus to C terminus of the polypeptide is VL, VH.

59. The antigen binding construct or minibody of any one of claims 1-57, wherein the order of the variable domains, from N terminus to C terminus of the polypeptide is VH, VL.

60. The antigen binding construct or minibody of any one of the preceding claims, wherein the minibody is a humanized antigen binding construct or minibody.

61. The antigen binding construct or minibody of claim 60, wherein the subject is a mammal, optionally wherein the subject is a human.

62. The antigen binding construct or minibody of any one of the preceding claims, wherein the antigen binding construct or minibody, has an ECso of about 0.001, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 2, 2.1, 2.2, 2.3, 2.4 , 2.5 or 3 nM.

63. The antigen binding construct or minibody of any one of the preceding claims, wherein the antigen binding construct or minibody, has an EC50 of between about 0.001 and 3 nM, 0.001 and 0.17 nM, 0.001 and 0.12 nM, 0.01 and 0.20 nM, 0.01 and 0.17 nM, 0.01 and 0.12 nM, 0.05 and 0.20 nM, 0.05 and 0.17 nM. 0.05 and 0.15 nM, 0.05 and 0.12 nM, 0.08 and 0.20 nM, 0.08 and 0.17 nM, 0.08 and 0.12 nM, 0.12 and 0.22nM, 0.14 and 0.18nM, 0.3 and 0.4nM, 0.5 and InM, 1 and 1.4nM, 1.1 and 2. InM, or 1.5 and 2.5nM.

64. The antigen binding construct or minibody of any one of the preceding claims, wherein the antigen binding construct or minibody, has an EC50 of up to about 10 nM.

65. The antigen binding construct or minibody of any one of the preceding claims, wherein the LCDR1 is or comprises SEQ ID NO:29, the LCDR2 is or comprises SEQ ID NO:30, and the LCDR3 is or comprises SEQ ID NO:31 or 32, optionally wherein the LCDR3 is or comprises SEQ ID NO:31.

66. The antigen binding construct or minibody of any one of the preceding claims, wherein the VL domain comprises: the LCDR1 that is the LCDR1 in SEQ ID NO:25, the LCDR2 that is the LCDR2 in SEQ ID NO:25; andthe LCDR3 that is the LCDR3 in SEQ ID NO:25 or 40, optionally wherein the LCDR3 that is the LCDR3 in SEQ ID NO:25.

67. The antigen binding construct or minibody of any one of the preceding claims, wherein the HCDR1 is or comprises SEQ ID NO:26, the HCDR2 is or comprises SEQ ID NO:27, the HCDR3 is or comprises SEQ ID NO:28.

68. The antigen binding construct or minibody of any one of the preceding claims, wherein the Vn domain comprises: the HCDR1 that is the HCDR1 in SEQ ID NO:24, the HCDR2 that is the HCDR2 in SEQ ID NO:24; and the HCDR3 that is the HCDR3 in SEQ ID NO:24.

69. The antigen binding construct or minibody of any one of claims 65-68, wherein the VL domain comprises a sequence of the VL domain in any one of SEQ ID NOs: 25 and 33-44, or a sequence at least 90% identical thereto.

70. The antigen binding construct or minibody of any one of claims 65-69, wherein the VL domain comprises a sequence of the VL domain in SEQ ID NO: 33, or a sequence at least 90% identical thereto.

71. The antigen binding construct or minibody of any one of claims 65-70, wherein the VH domain comprises a sequence of the VH domain in any one of SEQ ID NOs:24 and 33-44, or a sequence at least 90% identical thereto.

72. The antigen binding construct or minibody of any one of claims 65-71, wherein the VH domain comprises a sequence of the VH domain in SEQ ID NO: 33, or a sequence at least 90% identical thereto.

73. The antigen binding construct or minibody of any one of the preceding claims, comprising an scFv comprising the sequence of any one of SEQ ID NOs: 25 and 33-44 (with or without the signal sequence), or a sequence at least 90% identical thereto.

74. The antigen binding construct or minibody of claim 73, wherein the scFv comprises the sequence of SEQ ID NO:33 (with or without the signal sequence), or a sequence at least 90% identical thereto.

75. The antigen binding construct or minibody of any one of the preceding claims, comprising the sequence of any one of SEQ ID NOs: 114-125 (with or without the signal sequence), or a sequence at least 90% identical thereto.

76. The antigen binding construct or minibody of claim 75, comprising the sequence of SEQ ID NO: 114 (with or without the signal sequence), or a sequence at least 90% identical thereto.

77. A nucleic acid encoding an antigen binding construct or minibody of any one of the preceding claims.

78. A cell line producing an antigen binding construct or minibody of any one of the preceding claims.

79. A cell line producing an antigen binding construct or minibody, of any one of the preceding claims.

80. A kit comprising: an antigen binding construct or minibody, of any one of the preceding claims; and a detectable marker.

81. A kit comprising: an antigen binding construct or minibody, of any one of the preceding claims; and a chelator, wherein the chelator allows incorporation of a detectable marker.

82. A kit comprising: an antigen binding construct or minibody, of any one of the preceding claims; and a chelator, wherein the chelator allows incorporation of a therapeutic isotope.

83. A kit comprising: an antigen binding construct or minibody, of any one of the preceding claims; and a linker, wherein the linker allows incorporation of a detectable marker.

84. A kit comprising: an antigen binding construct or minibody, of any one of the preceding claims; and a linker, wherein the linker allows incorporation of a therapeutic isotope.

85. A kit comprising: an antigen binding construct or minibody, of any one of the preceding claims; and a detectable marker.

86. A method of detecting a presence or absence of a DLL3, the method comprising: applying the antigen binding construct or minibody, of any of the preceding claims to a sample; and detecting a presence or an absence of the antigen binding construct or minibody, thereby detecting a presence or absence of a DLL3.

87. The method of claim 86, wherein the antigen binding construct or minibody, is conjugated to a detectable marker.

88. The method of claim 86or 87, wherein applying the antigen binding construct or minibody, comprises administering the antigen binding construct to a subject.

89. The method of any one of claims 86-88, wherein detecting the presence or absence of binding of the antigen binding construct or minibody comprises at least one of positron emission tomography or single-photon emission computed tomography.

90. The method of any one of claims 86-89, the method further comprising applying a secondary antigen binding construct to the sample, wherein the secondary antigen binding construct binds specifically to the antigen binding construct.

91. The method of any one of claims 86-90, wherein the antigen binding construct or minibody, is incubated with the sample for no more than 20 hours.

92. The method of any one of claims 86-91, wherein the antigen binding construct or minibody, is incubated with the sample for no more than 6 hours.

93. The method of any one of claims 86-92, wherein the antigen binding construct or minibody, is administered to a host, and wherein a first quantity of antigen binding construct or minibody, thereof is unbound to DLL3, and a second quantity of antigen binding construct or minibody, is bound to DLL3, wherein at least about 80% of the first quantity of antigen binding construct or minibody, is eliminated in no more than 12 hours.

94. A method of targeting a therapeutic agent to DLL3, the method comprising administering to a subject an antigen binding construct or minibody, of any one of the preceding claims, wherein the antigen binding construct is conjugated to a therapeutic agent.

95. A therapeutic composition targeting DLL3, wherein the therapeutic composition comprises the antigen binding construct or the minibody of any one of claims 1-76.

96. The antigen binding construct or minibody of any one of the preceding claims, or the composition of any one of the preceding claims, or the kit of any one of the preceding claims, or the method of any one of the preceding claims, wherein the therapeutic agent comprises Terbium-149, Terbium-161, or Lead-212.

97. The antigen binding construct of any one of the preceding claims, or the composition of any one of the preceding claims, or the kit of any one of the preceding claims, or the method of any one of the preceding claims, wherein the antigen binding construct is an scFv- Fc comprising:a single-chain variable fragment (scFv) that binds to DLL3, the scFv comprising the variable light (VL) domain linked to the variable heavy (VH) domain; a hinge domain; and an Fc region.

98. An antigen binding construct that binds DLL3, wherein the antigen binding construct is a nanobody ®-Fc that binds DLL3 and comprises a variable heavy (VH) domain linked to a Fc region via a hinge domain.

99. The antigen binding construct of claim 98, wherein the variable heavy (VH) domain comprises: a HCDR1 that is any one of SEQ ID NO: 3, 18, 26, 47, 59, 70, or 80; a HCDR2 that is any one of SEQ ID NO: 4, 27 , 48, 60, 71, or 81; and a HCDR3 that is any one of SEQ ID NO: 5, 19, 28, 49, 61, 62, 72, or 82.

100. The antigen binding construct of claim 99, wherein the HCDR1 is or comprises SEQ ID NO:26, the HCDR2 is or comprises SEQ ID NO:27, the HCDR3 is or comprises SEQ ID NO:28.

101. The antigen binding construct of claim 99 or 100, wherein the VH domain comprises: the HCDR1 that is the HCDR1 in SEQ ID NO:24, the HCDR2 that is the HCDR2 in SEQ ID NO:24; and the HCDR3 that is the HCDR3 in SEQ ID NO:24.

102. The antigen binding construct of any one of claims 99-101, wherein the VH domain comprises a sequence of the VH domain in any one of SEQ ID NOs:24 and 33-44, or a sequence at least 90% identical thereto.

103. The antigen binding construct of any one of claims 99-102, wherein the VH domain comprises a sequence of the VH domain in SEQ ID NO: 33, or a sequence at least 90% identical thereto.

104. The antigen binding construct, nucleic acid, cell line, kit, composition or method of any one of the preceding claims, wherein the antigen binding construct or minibody comprises the HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3 sequences of the corresponding HCDR and LCDR sequences, or sequences at least 90% identical thereto respectively, in any one of the antigen binding constructs depicted in any one of Figs. 1-6 and in the arrangement of the HCDRand LCDR sequences as set forth in the any one of Figs. 1 -6, or set forth in any one of Tables 1 -6 and in the arrangement of the HCDR and LCDR sequences as set forth in the any one of Tables 1- 6.

105. The antigen binding construct, nucleic acid, cell line, kit, composition or method of any one of the preceding claims, wherein the antigen binding construct or minibody comprises the VH and VL sequences of the corresponding VH and VL sequences, or sequences at least 80% identical thereto respectively, in any one of the antigen binding constructs depicted in Figs. 1-6 and in the arrangement of the VH and VL sequences as set forth in the Figs. 1-6, or set forth in Table 11 and in the arrangement of the VH and VL sequences as set forth in the Table 11.

106. The antigen binding construct, nucleic acid, cell line, kit, composition or method of any one of the preceding claims, wherein the antigen binding construct or minibody comprises the sequence, or a sequence at least 80% identical thereto, of any one of the antigen binding constructs depicted in Figs. 1-6, or set forth in Table 12.

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