Molecules for treatment of cancer

Abstract

Bispecific molecules comprising a 4-1BB binding protein and a PD-L1 binding protein are provided herein. Related monospecific molecules binding to either 4-1BB or PD-L1 are also provided herein. Methods of treatment comprising administering a pharmaceutical composition comprising a bispecific or monospecific molecule as described herein are further provided.

Description

[0001] MOLECULES FOR TREATMENT OF CANCER CROSS REFERENCE TO RELATED APPLICATIONS [1] This application claims the benefit of U.S. Provisional Application Serial No.63 / 580,194, filed September 01, 2023, and U.S. Provisional Application Serial No.63 / 606,175, filed December 05, 2023. The foregoing applications are incorporated by reference in its entirety. INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ELECTRONICALLY [2] Incorporated by reference in its entirety is a computer-readable nucleotide / amino acid sequence listing submitted concurrently herewith and identified as follows: 10669-US02-PRI_SeqListing; created November 30, 2023. FIELD OF THE INVENTION [3] The present invention relates to antigen binding proteins, for example, bispecific molecules, for the treatment of cancer. BACKGROUND [4] The PD-1 / PD-L1 axis is involved in the suppression of T cell immune responses in cancer. Antagonists of this pathway have been clinically validated across a number of solid tumor indications. Nivolumab and pembrolizumab are two such inhibitors that target the PD-1 pathway, and each has been approved by the U.S. Food and Drug Administration (FDA) for the treatment of metastatic melanoma. Recently, researchers have tested the paradigm of checkpoint inhibition in the setting of other tumor types. While some advances have been made, checkpoint inhibition therapy still remains in the shadows of other cancer treatment options. [5] Studies of checkpoint inhibitors in combination with other agents are underway or recently have been completed. The combination of nivolumab and ipilimumab, a CTLA-4 receptor blocking antibody, for example, was tested in a Phase III clinical trial on patients with unresectable stage III or IV melanoma. In this study, the percentage of patients achieving a complete response was the highest among those that received the combination of nivolumab and ipilimumab, beating the outcome exhibited by those in the group receiving either drug alone. However, the response to immunotherapies that block CTLA-4 and PD- 1 checkpoint receptors is not universal, and multiple mechanisms by which tumors evade response have been identified. As an approach to enhance the overall efficacy and to limit tumor resistance, combination therapies targeting multiple pathways represent a rational next step. [6] 4-1BB, which is also known as CD137 or TNFRSF9, is a member of the TNF receptor superfamily. 4-1BB was first identified as a molecule whose expression is induced by T-cell activation (Kwon Y.H. and Weissman S.M. (1989), Proc. Natl. Acad. Sci. USA 86, 1963-1967). Subsequent studies demonstrated expression of 4-1BB in T- and B-lymphocytes, NK-cells, NKT-cells, monocytes, neutrophils, and dendritic cells as well as cells of non- hematopoietic origin such as endothelial and smooth muscle cells. Expression of 4-1BB in different cell types is mostly inducible and driven by various stimulatory signals, such as T-cell receptor (TCR) or B-cell receptor triggering, as well as signaling induced through co- stimulatory molecules or receptors of pro-inflammatory cytokines. [7] 4-1BB signaling is known to stimulate IFNγ secretion and proliferation of NK cells, as well as to promote DC activation as indicated by their increased survival and capacity to secret cytokines and upregulate co- stimulatory molecules. However, 4-1BB is best characterized as a co-stimulatory molecule which modulates TCR- induced activation in both the CD4+ and CD8+ subsets of T-cells. In combination with TCR triggering, agonistic 4-1BB-specific antibodies enhance proliferation of T-cells, stimulate lymphokine secretion and decrease sensitivity of T-lymphocytes to activation-induced cells death (Snell L.M. et al. (2011) Immunol. Rev.244, 197-217). In line with these co-stimulatory effects of 4-1BB antibodies on T-cells in vitro, their administration to tumor bearing mice leads to potent anti-tumor effects in many experimental tumor models (Melero I. et al. (1997), Nat. Med.3, 682-685; Narazaki H. et al. (2010), Blood 115, 1941-1948). In vivo depletion experiments demonstrated that CD8+ T-cells play the most critical role in anti-tumoral effect of 4-1BB-specific antibodies. However, depending on the tumor model or combination therapy, which includes anti-4-1BB, contributions of other types of cells such as DCs, NK-cells or CD4+ T-cells have been reported (MuriUo O. et al. (2009), Eur. J. Immunol.39, 2424- 2436; Stagg J. et al. (2011), Proc. Natl. Acad. Sci. USA 108, 7142-7147). [8] In addition to their direct effects on different lymphocyte subsets, 4- 1BB agonists can also induce infiltration and retention of activated T-cells in the tumor through 4-1BB -mediated upregulation of intercellular adhesion molecule 1 (ICAM1) and vascular cell adhesion molecule 1 (VCAM1) on tumor vascular endothelium.4-1BB triggering may also reverse the state of T-cell anergy induced by exposure to soluble antigen that may contribute to disruption of immunological tolerance in the tumor micro- environment or during chronic infections. [9] It has been reported that systemic administration of 4-1BB-specific agonistic antibodies induces expansion of CD8+ T-cells associated with liver toxicity (Dubrot J. et al. (2010), Cancer Immunol. Immunother.59, 1223-1233). In human clinical trials (ClinicalTrials.gov, NCT00309023), 4-1BB agonistic antibodies (BMS-663513) administered once every three weeks for 12 weeks induced stabilization of the disease in patients with melanoma, ovarian or renal cell carcinoma. However, the same antibody given in another trial (NCT00612664) caused grade 4 hepatitis leading to termination of the trial (Simeone E. and Ascierto P.A. (2012), J. Immunotoxicology 9, 241-247).

[0010] Thus, there is a need for new generation agonists that effectively engage 4-1BB while avoiding undesired side effects. There also is a need for therapies which target multiple pathways including the PD-1 pathway in order to enhance the overall efficacy and to limit the tumor resistance of checkpoint inhibitor therapy. SUMMARY

[0011] Based on the disclosure provided herein, those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following embodiments (E). E1. A 4-1BB antigen-binding protein comprising a heavy chain variable domain (VH) and a light chain variable domain (VL), wherein said protein binds to the Cysteine-rich pseudo repeat 1 (CRD1) of human 4-1BB (corresponding to residues 24-45 of SEQ ID NO: 272), and is a crosslinking-dependent agonist. E2. The 4-1BB antigen-binding protein of E1, comprising (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 151, 159, 324 or 167; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 152, 160, 325, or 168. E3. The 4-1BB antigen-binding protein of E1, comprising: (i) a CDR-H1 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 55, 79 or 103; (ii) a CDR-H2 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 56, 80, or 104; (iii) a CDR-H3 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 57, 81, or 105; (iv) a CDR-L1 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 58, 82, or 106; (v) a CDR-L2 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 59, 83, or 107; and (vi) a CDR-L3 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 60, 84, or 108. E4. The 4-1BB antigen-binding protein of any one of E1-E3, comprising: (1) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.55-60, respectively (14A5); (2) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.79-84, respectively (14A5.002); or (3) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.103-108, respectively (16D1.001). E5. A 4-1BB antigen-binding protein comprising a heavy chain variable domain (VH) and a light chain variable domain (VL), wherein said protein binds to the Cysteine-rich pseudo repeat 2 (CRD2) of human 4-1BB (corresponding to residues 47-86 of SEQ ID NO: 272), and is a crosslinking-dependent agonist. E6. The 4-1BB antigen-binding protein of E5, comprising (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 149, 161, 157, 169, 147, 163, 165, 153, 171, 175, 155, 404, 406, 408, or 410; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 150, 162, 158, 170, 148, 164, 166, 154, 172, 176, 156, 405, 407, 409, or 411. E7. The 4-1BB antigen-binding protein of E5, comprising: (i) a CDR-H1 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 49, 85, 73, 109, 43, 91, 97, 61, 115, 127, 67, 386, or 392; (ii) a CDR-H2 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 50, 86, 74, 110, 44, 92, 98, 62, 116, 128, 68, 387, or 393; (iii) a CDR-H3 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 51, 87, 75, 111, 45, 93, 99, 63, 117, 129, 69, 388, or 394; (iv) a CDR-L1 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 52, 88, 76, 112, 46, 94, 100, 64, 118, 130, 70, 389, or 395; (v) a CDR-L2 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 53, 89, 77, 113, 47, 95, 101, 65, 119, 131, 71, 390, or 396; and (vi) a CDR-L3 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 54, 90, 78, 114, 48, 96, 102, 66, 120, 132, 72, 391, or 397. E8. The 4-1BB antigen-binding protein of any one of E5-E7, comprising: (1) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.49-54, respectively (6F9); (2) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.85-90, respectively (6F9.009); (3) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.73-78, respectively (14G12.017); (4) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.109-114, respectively (17H1.009); (5) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.43-48, respectively (6C7); (6) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.91-96, respectively (6C7.018); (7) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.97-102, respectively (4E9.020); (8) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.61-66, respectively (19G1); (9) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.115-120, respectively (19G1.016); (10) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.127-132, respectively (19G1.016.001); (11) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.67-72, respectively (15A12.012); (12) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.386-391, respectively (56039); or (13) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.392-397, respectively (56040). E9. A 4-1BB antigen-binding protein comprising a heavy chain variable domain and a light chain variable domain, wherein said protein binds to the Cysteine-rich pseudo repeat 3 (CRD3) of human 4- 1BB (corresponding to residues 87-118 of SEQ ID NO: 272), and is a crosslinking-dependent agonist. E10. The 4-1BB antigen-binding protein of E9, comprising (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 173; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 174. E11. The 4-1BB antigen-binding protein of E9, comprising: (i) a CDR-H1 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 121; (ii) a CDR-H2 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 122; (iii) a CDR-H3 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 123; (iv) a CDR-L1 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 124; (v) a CDR-L2 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 125; and (vi) a CDR-L3 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 126. E12. The 4-1BB antigen-binding protein of any one of E9-E11, comprising: a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs: 121-126, respectively (15A6.011). E13. A 4-1BB antigen-binding protein comprising a heavy chain variable domain and a light chain variable domain, wherein said VH comprises: (i) a CDR-H1 comprising X1 Y X2 X3 X4 (SEQ ID NO: 474), wherein: X1 = R, S, T, N, or G; X2 = Y, A, S, or G; X3 = W, M, or L; and X4 = S, N, or H; (ii) a CDR-H2 comprising X1 I X2 X3 X4 X5 X6 X7 X8 Y X9 X10 X11 X12 X13 X14 K X15 (SEQ ID NO:475), wherein X1 = Y, R, A, V, or L; X2 = D, Y, S, W, or G; X3 = G, S, Y, I, or absent; X4 = D, Y, T, or S; X5 = S, G, A, or T; X6 = G or S; X7 = N, H, S, T, Q, or A; X8 = T, I, E, or K; X9 = N or Y; X10 = Y or D; X11 = N, A, or V; X12 = P, D, or E; X13 = S or P; X14 = L or V; and X15 = S or G; and (iii) a CDR-H3 comprising X1 X2 X3 X4 X5 X6 X7 X8 Y X9 X10 X11 X12 X13 X14 X15 X16 X17 D X18 (SEQ ID NO: 476), wherein X1 = G, T, E, or D; X2 = V, D, T, G, L, A, E, or H; X3 = A, Y, G, I, N, V, I, or L; X4 = A, Y, F, T, D, L, or V; X5 = G, Y, or A; X6 = R, F, D, E, T, G, N, or Y; X7 = G or absent; X8 = K or absent; X9 = T or absent; X10 = T, A, P, or absent; X11 = S, L, T, A, S, Y, L, or absent; X12 = G, L, Y, or absent; X13 = Y, H, or absent; X14 = Y, H, or absent; X15 = D, Y, F, R, or absent; X16 = E, W, G, A, Y, or absent; X17 = I, M, F, or L; and X18 = P, V, Y, or F; and wherein said VL comprises: (i) a CDR-L1 comprising X1 X2 X3 X4 X5 X6 X7 X8 Y X9 X10 X11 X12 X13 X14 X15 X16 (SEQ ID NO: 477), wherein X1 = G, S, R, or K; X2 = G, A, or S; X3 = N, S, D, or G; X4 = N, Q, K, or A; X5 = S or absent; X6 = N, L, or absent; X7 = L or absent; X8 = H, R, or absent; X9 = T, S, or absent; X10 = I, S, L, G, or D; X11 = G, I, or P; X12 = S, K, D, or G; X13 = K, S, R, N, or T; X14 = N, A, or Y; X15 = V, L, or A; and X16 = H, N, C, Y, F, A, or S; (ii) a CDR-L2 comprising X1 X2 X3 X4 X5 X6 S (SEQ ID NO:478), wherein X1 = D, S, A, Q, or E; X2 = D, N, A, or L; X3 = S, H, or A; X4 = D, Q, S, R, K, N, V, or T; X5 = R, or L; and X6 = P, Q, or F; and (iii) a CDR-L3 comprising X1 X2 X3 X4 X5 X6 X7 X8 Y X9 X10 X11 (SEQ ID NO: 479), wherein X1 = Q, E, L, Y, or M; X2 = V, A, Q, T, S, or K; X3 = W, R, T, Y, or S; X4 = D, F, Y, I, or N; X5 = S, D, E, H, or Q; X6 = S, I, A, L, V, T, or R; X7 = S, L, P, A, or absent; X8 = D or N; X9 = H or G; X10 = V, P, F, L, G, or W ; and X11 = V, T, M, or A. E14. A 4-1BB antigen-binding protein comprising a heavy chain variable domain and a light chain variable domain, wherein said VH is a VH3 that comprises: (i) a CDR-H1 comprising X1 Y X2 X3 X4 (SEQ ID NO:484), wherein X1 = S, T, N, or G, X2 = A, S, or G; X3 = M or L; and X4 = N, or H; or a CDR-H1 comprising X1 X2 A M S (SEQ IDNO:485), wherein X1 = H, Y, or S; and X2 = Y or P; (ii) a CDR-H2 comprising X1 I X2 X3 X4 X5 X6 X7 X8 Y X9 X10 X11 S V K G (SEQ ID NO:486), X1 = X2 = = X4 = D = = H; X3 = I, N, G, D, A, I, V, or L; X4 = F, I, D, L, T, Y or A; X5 = G, Y, L, or A; X6 = V, F, G, T, E, Y, or absent; X7 = V, Y, A, G, T, L, or absent; X8 = K, Y, L, or absent; X9 = T, Y, or absent; X10 = N, P, or absent; X11 = Y or absent; X12 = Y or absent; X13 = Y, H, or absent; X14 = Y, H, A, I, or absent; X15 = I, F, Y, E, R, or absent; X16 = Y, G, A, N, or absent; X17 = M, F, or L; X18 = D or Q; and X19 = Y, V, H, or F; or a CDR-H3 comprising X1 X2 X3 X4 G X5 X6 X7 Y Y Y G M D V (SEQ ID NO:488), wherein X1 = G or S; X2 = Y or G; X3 = S or Y; X4 = Y or V; X5 = Y or E; X6 = Y or L; and X7 = Y or L. E15. A 4-1BB antigen-binding protein comprising a heavy chain variable domain and a light chain variable domain, wherein said VH is a VH4 that comprises: (i) a CDR-H1 comprising X1 Y Y W S (SEQ IDNO:489), wherein X1 = S or R; (ii) a CDR-H2 comprising X1 I X2 X3 S G X4 T N Y N P X5 L K S (SEQ ID NO: 490), wherein X1 = Y or R; X2 = Y or D; X3 = Y, D or T; X4 = S, N, Q, or H; and X5 = S or P; and (iii) a CDR-H3 comprising X1 X2 X3 X4 X5 X6 X7 X8 Y X9 X10 X11 X12 X13 X14 D X15 (SEQ ID NO:491), wherein X1 = G, R, T, L, or E; X2 = I, V, D, or T; X3 = A, G, or Y; X4 = A, Y, or N; X5 = A, G, N, Y, or absent; X6 = G, Y, D, or absent; X7 = Y, T, or absent; X8 = Y, S, or absent; X9 = G or absent; X10 = Y or absent; X11 = Y or absent; X12 = N, Y, F, D, or absent; X13 = W, R, G, or E; X14 = F, I, or M; and X15 = P or V. E16. The 4-1BB antigen-binding protein of E14 or E15, wherein said VL is a Vκ2 that comprises: (i) a CDR-L1 comprising K S S Q S L L X1 X2 X3 G K T Y L X4 (SEQ ID NO: 492), wherein X1 = R or H; X2 = S or T; X3 = D or S; and X4 = Y or F; (ii) a CDR-L2 comprising X1 X2 S N R F S (SEQ ID NO: 493), wherein X1 = E or D; and X2 = V or L; and (iii) a CDR-L3 comprising M Q X1 I X2 X3 P X4 T (SEQ ID NO: 494), wherein X1 = S or T; X2 = Q or H; X3 = L or R; and X4 = W or F. E17. The 4-1BB antigen-binding protein of E14 or E15, wherein said VL is a Vκ1 that comprises: (i) a CDR-L1 comprising R A S Q X1 I X2 X3 Y L N (SEQ ID NO: 495), wherein X1 = S, G, or T; X2 = S, G, or K; and X3 = S, T, N, or R; (ii) a CDR-L2 comprising A X1 S X2 L Q S (SEQ ID NO: 496), wherein X1 = A or I; and X2 = S, T, or N; and (iii) a CDR-L3 comprising X1 X2 X3 X4 X5 X6 X7 X8 T (SEQ ID NO: 497), wherein X1 = Q or L; X2 = Q or K; X3 = S, T, Y, or R; X4 = Y, N, or F; X5 = S or absent; X6 = T, S, V, or I; X7 = P or A; and X8 = L or F. E18. The 4-1BB antigen-binding protein of E14 or E15, wherein said VL is a Vλ3 that comprises: (i) a CDR-L1 comprising X1 G X2 X3 X4 X5 X6 X7 X8 X9 X10 (SEQ ID NO: 498), wherein X1 = G or S; X2 = N or D; X3 = N, A, or K; X4 = I or L; X5 = G or P; X6 = S, K, or D; X7 = K or N; X8 = S, = S or A; and X3 = D, K, or R; and (iii) a CDR-L3 comprising X1 X2 X3 D S X4 X5 X6 X7 X8 X9 (SEQ ID NO: 500), wherein X1 = Q or Y; X2 = V, S, A, or T; X3 = W, T, or R; X4 = S or absent; X5 = S, G, or absent; X6 = D, N, T, or S; X7 = H or A; X8 = V or G; and X9 = V, A, or M. E19. The 4-1BB antigen-binding protein of E14 or E15, wherein said VL is a Vλ1 that comprises: (i) a CDR-L1 comprising S G X1 X2 S N I G S X3 X4 V N (SEQ ID NO: 501), wherein X1 = G or S; X2 = S or N; X3 = N (ii) a CDR-L2 (iii) a CDR-L3 comprising X1 A W D D S L N G X2 V (SEQ ID NO: 503), wherein X1 = A or E; and X2 = P or V. E20. The 4-1BB antigen-binding protein of any one of E1-E17, comprising a VL framework derived from a human germline Vκ framework sequence. E21. The 4-1BB antigen-binding protein of any one of E1-E15 and E18-E19, comprising a VL framework derived from a human germline Vλ framework sequence. E22. The 4-1BB antigen-binding protein of any one of E1-E21, comprising a VH framework derived from a human germline VH1, VH2, VH3, VH4, or VH5 framework sequence. E23. The 4-1BB antigen-binding protein of any one of E1-E21, comprising a VH framework derived from a human germline VH1 framework sequence. E24. The 4-1BB antigen-binding protein of any one of E1-E21, comprising a VH framework derived from a human germline VH3 framework sequence. E25. The 4-1BB antigen-binding protein of any one of E1-E21, comprising a VH framework derived from a human germline VH4 framework sequence. E26. The 4-1BB antigen-binding protein of any one of E1-E21, comprising a VH framework derived from a human germline VH2 framework sequence. E27. The 4-1BB antigen-binding protein of any one of E1-E21, comprising a VH framework derived from a human germline VH5 framework sequence. E28. The 4-1BB antigen-binding protein of any one of E14-E27, comprising a VL framework sequence and a VH framework sequence, and wherein one or both of the VL framework sequence or VH framework sequence is at least 90% identical to the human germline framework sequence from which it is derived. E29. The 4-1BB antigen-binding protein of any one of E14-E28, comprising a VL framework sequence and a VH framework sequence, and wherein one or both of the VL framework sequence or VH framework sequence is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to the human germline framework sequence from which it is derived. E30. The 4-1BB antigen-binding protein of any one of E1-E29, comprising: a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to any one of SEQ ID NOs: 147, 149, 151, 153, 155, 157, 159, 324, 161, 163, 165, 167, 169, 171, 173, 175, 404, 406, 408, and 410. E31. The 4-1BB antigen-binding protein of any one of E1-E30, comprising: a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to any one of SEQ ID NOs: 148, 150, 152, 154, 156, 158, 160, 325, 162, 164, 166, 168, 170, 172, 174, 176, 405, 407, 409, and 411. E32. The 4-1BB antigen-binding protein of any one of E1-E31, comprising: (a) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.147, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.148; (b) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.149, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.150; (c) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.151, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.152; (d) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.153, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.154; (e) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.155, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.156; (f) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.157, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.158; (g) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.159 or 324, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.160 or 325; (h) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.161, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.162; (i) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.163, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.164; (j) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.165, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.166; (k) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.167, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.168; (l) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.169, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.170; (m) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.171, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.172; (n) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.173, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.174; (o) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.175, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.176; (p) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.404, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.405; (q) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.406, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.407; (r) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.408, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.409; or (s) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.410, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.411. E33. A 4-1BB antigen-binding protein that comprises a heavy chain variable domain (VH) and does not comprise a light chain variable domain (VL), wherein said protein comprises the CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, or 385. E34. A 4-1BB antigen-binding protein that comprises a heavy chain variable domain (VH) and does not comprise a light chain variable domain (VL), wherein said VH comprises: (i) a CDR-H1 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 326, 329, 332, 335, 338, 341, 344, 347, 350, 353, 356, 359, 362, 365, or 368; (ii) a CDR-H2 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 327, 330, 333, 336, 339, 342, 345, 348, 351, 354, 357, 360, 363, 366, 369; and (iii) a CDR-H3 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 328, 331, 334, 337, 340, 343, 346, 349, 352, 355, 358, 361, 364, 367, 370. E35. The 4-1BB antigen-binding protein of E33 or E34, comprising: (1) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.326-328, respectively; (2) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.329-331, respectively; (3) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.332-334, respectively; (4) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.335-337, respectively; (5) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.338-340, respectively; (6) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.341-343, respectively; (7) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.344-346, respectively; (8) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.347-349, respectively; (9) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.350-352, respectively; (10) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.353-355, respectively; (11) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.356-358, respectively; (12) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.359-361, respectively; (13) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.362-364, respectively; (14) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.365-367, respectively; or (15) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.368-370, respectively; E36. A 4-1BB antigen-binding protein that comprises a heavy chain variable domain (VH) and does not comprise a light chain variable domain (VL), wherein said VH comprises: (i) a CDR-H1 comprising X1 X2 X3 M X4 (SEQ ID NO: 480), wherein X1 = S, D, T, or N; X2 = F, Y, or S; X3 = A, W, G, Y, N, or V; and X4 = T, S, H, N, or I; (ii) a CDR-H2 comprising X1 I X2 X3 X4 X5 X6 G X7 X8 Y X9 X10 X11 X12 X13 X14 X15 X16 G (SEQ ID NO: 481), wherein X1 = A, F, N, E, V, G, or Y; X2 = S, R, N, T, or H; X3 = G, S, Q, Y, D, or W; X4 = K or absent; X5 = A, T, or absent; X6 = S, N, D, G, or Y; X7 = G, S, D, T, or E; X8 = S, T, E, K, or D; X9 = T, K, or I; X10 = Y, E, F, G, or S; X11 = Y or S; X12 = A, V, or P; X13 = G, A, D, or E; X14 = S or A; X15 = V, E, or M; and (ii) a CDR-H3 comprising X1 X2 X3 X4 X5 X6 ID NO:482), wherein X1 = E, D, G, L, M, F, or M, G, P, R, Y, L, or T; X4 = E, P, T, D, G, R, S, or L; X5 = S, P, A, E, V, I, H, or Y; X6 = S, L, P, T, V, I, G, or F; X7 = L, A, or absent; X8 = V, M, A, G, I, or absent; X9 = Y, L, A, T, P, G, W, S, or absent; X10 = Y, R, N, T, or absent; X11 = T, G, S, V, R, H, P, E, A, or absent; X12 = T, Y, S, G, or A; X13 = S, H, N, T, G, or A; X14 = F or L; X15 = D or E; and X16 = Y or I. E37. The 4-1BB antigen-binding protein of any one of E33-E36, comprising a VH framework derived from a human germline VH1, VH2, VH3, VH4, or VH5 framework sequence. E38. The 4-1BB antigen-binding protein of any one of E33-E37, comprising a VH framework derived from a human germline VH1 framework sequence. E39. The 4-1BB antigen-binding protein of any one of E33-E37, comprising a VH framework derived from a human germline VH3 framework sequence. E40. The 4-1BB antigen-binding protein of any one of E33-E37, comprising a VH framework derived from a human germline VH4 framework sequence. E41. The 4-1BB antigen-binding protein of any one of E33-E37, comprising a VH framework derived from a human germline VH2 framework sequence. E42. The 4-1BB antigen-binding protein of any one of E33-E37, comprising a VH framework derived from a human germline VH5 framework sequence. E43. The 4-1BB antigen-binding protein of any one of E33-E42, comprising a VH framework sequence is at least 90% identical to the human germline framework sequence from which it is derived. E44. The 4-1BB antigen-binding protein of any one of E33-E43, comprising a VH framework sequence is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to the human germline framework sequence from which it is derived. E45. The 4-1BB antigen-binding protein of any one of E33-E44, comprising: a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to any one of SEQ ID NOs: 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, and 385. E46. The 4-1BB antigen-binding protein of any one of E33-E45, comprising: (a) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.371; (b) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.372; (c) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.373; (d) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.374; (e) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.375; (f) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.376; (g) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.377; (h) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.378; (i) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.379; (j) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.380; (k) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.381; (l) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.382; (m) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.383; (n) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.384; or (o) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.385. E47. The 4-1BB antigen-binding protein of any one of E1-E46 and E315-E342, further comprising a heavy chain CH1 domain. E48. The 4-1BB antigen-binding protein of E47, wherein said CH1 domain is the CH1 domain of an IgG (for example IgG1, lgG2, lgG3, or lgG4). E49. The 4-1BB antigen-binding protein of E47 or E48, wherein said CH1 domain is the CH1 domain of a human IgG (for example, human IgG1, human IgG2, human IgG3, or human IgG4). E50. The 4-1BB antigen-binding protein of any one of E47-E49, wherein said CH1 domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 242, 259, 261, 265, 269, 422, or 425. E51. The 4-1BB antigen-binding protein of any one of E47-E50, wherein said CH1 domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 242, 259, 422, or 425. E52. The 4-1BB antigen-binding protein of any one of E1-E51 and E315-E342, further comprising an Fc region. E53. The 4-1BB antigen-binding protein of E52, wherein the Fc region is the Fc region of an IgA (for example IgA1 or lgA2), IgD, IgE, IgM, or IgG (for example IgG1, lgG2, lgG3, or lgG4). E54. The 4-1BB antigen-binding protein of E52 or E53, wherein the Fc region is the Fc region of an IgG. E55. The 4-1BB antigen-binding protein of E54, wherein the IgG is selected from the group consisting of IgG1, lgG2, lgG3, and lgG4. E56. The 4-1BB antigen-binding protein of E55, wherein the IgG is IgG1, IgG2, or IgG4. E57. The 4-1BB antigen-binding protein of any one of E52-E56, wherein said Fc region is derived from an IgG Fc, and further comprises one or more mutations selection from the group consisting of: L234A, L235A, L235E, G237A, and combination thereof (numbering according to the EU index). E58. The 4-1BB antigen-binding protein of E57, comprising L234A and L235A mutations. E59. The 4-1BB antigen-binding protein of any one of E52-E58, wherein said Fc region is derived from an IgG Fc, and further comprises one or more mutations selection from the group consisting of: V259C, A287C, R292C, V302C, L306C, V323C, I332C, and a combination thereof (numbering according to the EU index). E60. The 4-1BB antigen-binding protein of any one of E52-E59, wherein said Fc region is derived from an IgG Fc, and further comprises one or more mutations selection from the group consisting of: L242C, A287C, R292C, N297G, V302C, L306C, K334C, and a combination thereof (numbering according to the EU index). E61. The 4-1BB antigen-binding protein of E60, comprising a N297G mutation. E62. The 4-1BB antigen-binding protein of E60, comprising A287C, N297G, and L306C mutations. E63. The 4-1BB antigen-binding protein of E60, comprising R292C, N297G, and V302C mutations. E64. The 4-1BB antigen-binding protein of any one of E52-E63, wherein said Fc region is derived from an IgG Fc, and further comprises one or more mutations selection from the group consisting of: M252Y, S254T, T256E, and a combination thereof. E65. The 4-1BB antigen-binding protein of E64, comprising M252Y, S254T, T256E mutations. E66. The 4-1BB antigen-binding protein of any one of E52-E65, wherein the lysine residue (K) at the C-terminus of the Fc region is deleted. E67. The 4-1BB antigen-binding protein of any one of E52-E65, wherein the lysine residue (K) at the C-terminus of the Fc region is present. E68. The 4-1BB antigen-binding protein of any one of E52-E65, wherein the glycine and lysine residues (GK) at the C-terminus of the Fc region are present. E69. The 4-1BB antigen-binding protein of any one of E52-E65, wherein the glycine and lysine residues (GK) at the C-terminus of the Fc region are deleted. E70. The 4-1BB antigen-binding protein of any one of E52-E69, wherein said Fc region comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 243, 250, 251, 252, 253, 254, 255, 413, 423, or 426. E71. The 4-1BB antigen-binding protein of any one of E52-E69, wherein said Fc region comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 263, 267, or 483. E72. The 4-1BB antigen-binding protein of any one of E1-E71 and E315-E342, further comprising a heavy chain constant domain. E73. The 4-1BB antigen-binding protein of E72, wherein said constant domain is the constant domain of an IgA (for example IgA1 or lgA2), IgD, IgE, IgM, or IgG (for example IgG1, lgG2, lgG3, or lgG4). E74. The 4-1BB antigen-binding protein of E72 or E73, wherein said constant domain is the constant domain of an IgG (for example IgG1, IgG2, IgG3, or IgG4), preferably a human IgG (for example, human IgG1, human IgG2, human IgG3, or human IgG4). E75. The 4-1BB antigen-binding protein of any one of E72-E74, wherein said constant domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 244, 245, 246, 247, 248, 249, 256, 257, 258, 260, 412, 415, 417, 418, or 427. E76. The 4-1BB antigen-binding protein of any one of E72-E74, wherein said constant domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 264, 268, or 271. E77. The 4-1BB antigen-binding protein of any one of E1-E32 and E47-E76, further comprising a kappa or lambda light chain constant domain. E78. The 4-1BB antigen-binding protein of any one of E1-E32 and E47-E77, further comprising a kappa light chain constant domain that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 236, 237, 240, 414, 416, 419, 420, 421, or 428. E79. The 4-1BB antigen-binding protein of any one of E1-E32 and E47-E77, further comprising a lambda light chain constant domain that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 238, 239, 241, or 424. E80. The 4-1BB antigen-binding protein of any one of E1-E32 and E47-E79, comprising: (i) a heavy chain (HC) comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to any one of SEQ ID NOs: 191, 193, 195, 197, 199, 201, 203, 205, 207, 209, 211, 213, 215, 217, and 219; and (ii) a light chain (LC) comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to any one of SEQ ID NOs: 192, 194, 196, 198, 200, 202, 204, 206, 208, 210, 212, 214, 216, 218, and 220. E81. The 4-1BB antigen-binding protein of any one of E1-E32 and E47-E80, comprising: (a) a heavy chain (HC) comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.191, and a light chain (LC) comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.192; (b) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.193, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.194; (c) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.195, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.196; (d) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.197, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.198; (e) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.199, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.200; (f) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.201, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.202; (g) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.203, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.204; (h) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.205, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.206; (i) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.207, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.208; (j) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.209, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.210; (k) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.211, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.212; (l) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.213, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.214; (m) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.215, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.216; (n) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.217, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.218; or (o) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.219, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.220. E82. The 4-1BB antigen-binding protein of any one of E1-E32 and E47-E81, which is an antibody. E83. The 4-1BB antigen-binding protein of any one of E1-E32 and E47-E81, which is an antigen- binding fragment of an antibody, such as a Fab fragment. E84. The 4-1BB antigen-binding protein of any one of E1-E32 and E47-E81, which is an scFv. E85. The 4-1BB antigen-binding protein of E84, wherein said scFv comprises a first linker between VH and VL. E86. The 4-1BB antigen-binding protein of E85, wherein said first linker comprises: (a) a glycine rich peptide; (b) a peptide comprising glycine and serine; (c) a peptide comprising (Gly-Gly-Ser)n, wherein n is 1 , 2, 3, 4, 5, or 6 (SEQ ID NO: 234); (d) a peptide comprising (Gly-Gly-Gly-Ser)n, wherein n is 1 , 2, 3, 4, 5, or 6 (SEQ ID NO: 232); (e) a peptide comprising (Gly-Gly-Gly-Gly-Ser)n, wherein n is 1 , 2, 3, 4, 5, or 6 (SEQ ID NO: 233); (f) a peptide comprising (Gly-Gly-Gly-Gly-Gln)n, wherein n is 1 , 2, 3, 4, 5, or 6 (SEQ ID NO: 235), or (g) a peptide comprising any one of SEQ ID NOs.221-235 and 504. E87. The 4-1BB antigen-binding protein of E85, wherein said first linker comprises the amino acid sequence of (Gly-Gly-Gly-Gly-Ser)3 (SEQ ID NO: 230). E88. The 4-1BB antigen-binding protein of any one of E1-E32 and E84-E87, comprising a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 291 (14A5.002 scFv). E89. The 4-1BB antigen-binding protein of any one of E1-E32 and E84-E87, comprising a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 445 (14A5.002 scFv #2). E90. The 4-1BB antigen-binding protein of any one of E1-E32 and E47-E81, which is a Fab. E91. The 4-1BB antigen-binding protein of E90, comprising a Fab heavy chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 298, and a Fab light chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 300 (6F9.009 Fab). E92. The 4-1BB antigen-binding protein of E90, comprising a Fab heavy chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 305, and a Fab light chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 307 (19G1.016 Fab). E93. The 4-1BB antigen-binding protein of E90, comprising a Fab heavy chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 316, and a Fab light chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 317 (6C7.018 Fab). E94. The 4-1BB antigen-binding protein of E90, comprising a Fab heavy chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to residues 1-227 of SEQ ID NO: 434, and a Fab light chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 435 (4-1BB Fab of 56039). E95. The 4-1BB antigen-binding protein of E90, comprising a Fab heavy chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to residues 1-227 of SEQ ID NO: 449, and a Fab light chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 450 (4-1BB Fab of 56040). E96. The 4-1BB antigen-binding protein of any one of E1-E95, wherein the antigen-binding protein binds to 4-1BB with a KD value of or less than: about 500nM, about 400nM, about 300nM, about 200nM, about 150nM, about 100nM, about 90nM, about 80nM, about 70nM, about 60nM, about 50nM, about 40nM, about 30nM, about 25nM, about 20nM, about 15nM, about 10nM, about 9nM, about 8nM, about 7nM, about 6nM, about 5nM, about 4nM, about 3nM, about 2nM, about 1 nM, about 900pM, about 800pM, about 700pM, about 600pM, about 500pM, about 400pM, about 300pM, about 250pM, about 200pM, about 150pM, about 100pM, about 50pM, about 40pM, about 30pM, about 25pM, about 20pM, about 15pM, about 10pM, about 5pM, or about 1pM. E97. A 4-1BB antigen-binding protein that competes for binding to 4-1BB with any one of the 4-1BB antigen binding protein of E1-E96 and E315-E342. E98. A 4-1BB antigen-binding protein that binds to substantially the same epitope as any one of the 4- 1BB antigen binding protein of E1-E96 and E315-E342. E99. A bispecific molecule that comprises the 4-1BB antigen-binding protein of any one of E1-E98 and E315-E342, and further comprises a second antigen-binding moiety. E100. The bispecific molecule of E99, wherein said second antigen-binding moiety binds to a protein of the immune checkpoint pathway. E101. The bispecific molecule of E100, wherein the protein of the immune checkpoint pathway is CTLA- 4, PD-1, PD-L1, PD-L2, B7-H3, B7-H4, CEACAM-1, TIGIT, LAG3, CD112, CD112R, CD96, TIM3, or BTLA. E102. The bispecific molecule of E101, wherein the protein of the immune checkpoint pathway is PD- L1. E103. A PD-L1 antigen-binding protein, comprising (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 133, 135, 137, 139, 141, 143, 322, 145, 398, 400, or 402; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 134, 136, 138, 140, 142, 144, 323, 146, 399, 401, or 403. E104. A PD-L1 antigen-binding protein, comprising: (i) a CDR-H1 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 1, 7, 13, 19, 25, 31, or 37; (ii) a CDR-H2 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 2, 8, 14, 20, 26, 32, or 38; (iii) a CDR-H3 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 3, 9, 15, 21, 27, 33, or 39; (iv) a CDR-L1 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 4, 10, 16, 22, 28, 34, or 40; (v) a CDR-L2 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 5, 11, 17, 23, 29, 35, or 41; and (vi) a CDR-L3 comprising a sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 6, 12, 18, 24, 30, 36, or 42. E105. The PD-L1 antigen-binding protein of E103 or E104, comprising: (1) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.1-6, respectively; (2) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.7-12, respectively; (3) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.13-18, respectively; (4) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.19-24, respectively; (5) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.25-30, respectively; (6) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.31-36, respectively; or (7) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.37-42, respectively. E106. The PD-L1 antigen-binding protein of any one of E103-E105, comprising a VL framework derived from a human germline Vκ framework sequence. E107. The PD-L1 antigen-binding protein of any one of E103-E105, comprising a VL framework derived from a human germline Vλ framework sequence. E108. The PD-L1 antigen-binding protein of any one of E103-E107, comprising a VH framework derived from a human germline VH1, VH2, VH3, VH4, or VH5 framework sequence. E109. The PD-L1 antigen-binding protein of any one of E103-E107, comprising a VH framework derived from a human germline VH1 framework sequence. E110. The PD-L1 antigen-binding protein of any one of E103-E107, comprising a VH framework derived from a human germline VH2 framework sequence. E111. The PD-L1 antigen-binding protein of any one of E103-E107, comprising a VH framework derived from a human germline VH3 framework sequence. E112. The PD-L1 antigen-binding protein of any one of E103-E107, comprising a VH framework derived from a human germline VH4 framework sequence. E113. The PD-L1 antigen-binding protein of any one of E103-E107, comprising a VH framework derived from a human germline VH5 framework sequence. E114. The PD-L1 antigen-binding protein of any one of E103-E113, comprising a VL framework sequence and a VH framework sequence, and wherein one or both of the VL framework sequence or VH framework sequence is at least 90% identical to the human germline framework sequence from which it is derived. E115. The PD-L1 antigen-binding protein of any one of E103-E114, comprising a VL framework sequence and a VH framework sequence, and wherein one or both of the VL framework sequence or VH framework sequence is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to the human germline framework sequence from which it is derived. E116. The PD-L1 antigen-binding protein of any one of E103-E115, comprising a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to any one of SEQ ID NOs:133, 135, 137, 139, 141, 143, 322, 145, 398, 400, and 402 E117. The PD-L1 antigen-binding protein of any one of E103-E116, comprising a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to any one of SEQ ID NOs: 134, 136, 138, 140, 142, 323144, 146, 399, 401, and 403. E118. The PD-L1 antigen-binding protein of any one of E103-E117, comprising: (1) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.133, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.134; (2) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.135, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.136; (3) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.137, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.138; (4) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.139, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.140; (5) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.141, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.142; (6) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.143, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.144; (7) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.322, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.323; (8) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.145, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.146; (9) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.398, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.399; (10) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.400, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.401; or (11) a VH comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.402, and a VL comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.403. E119. The PD-L1 antigen-binding protein of any one of E103-E118, further comprising a heavy chain CH1 domain. E120. The PD-L1 antigen-binding protein of E119, wherein said CH1 domain is the CH1 domain of an IgG (for example IgG1, lgG2, lgG3, or lgG4). E121. The PD-L1 antigen-binding protein of E119 or E120, wherein said CH1 domain is the CH1 domain of a human IgG (for example, human IgG1, human IgG2, human IgG3, or human IgG4). E122. The PD-L1 antigen-binding protein of any one of E119-E121, wherein said CH1 domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 242, 259, 261, 265, 269, 422, or 425. E123. The PD-L1 antigen-binding protein of any one of E119-E121, wherein said CH1 domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 242, 259, 422, or 425. E124. The PD-L1 antigen-binding protein of any one of E103-E123, further comprising an Fc region. E125. The PD-L1 antigen-binding protein of E124, wherein the Fc region is the Fc region of an IgA (for example IgA1 or lgA2), IgD, IgE, IgM, or IgG (for example IgG1, lgG2, lgG3, or lgG4). E126. The PD-L1 antigen-binding protein of E124 or E125, wherein the Fc region is the Fc region of an IgG. E127. The PD-L1 antigen-binding protein of E126, wherein the IgG is selected from the group consisting of IgG1, lgG2, lgG3, and lgG4. E128. The PD-L1 antigen-binding protein of E126, wherein the IgG is IgG1, IgG2, or IgG4. E129. The PD-L1 antigen-binding protein of any one of E124-E128, wherein said Fc region is derived from an IgG Fc, and further comprises one or more mutations selection from the group consisting of: L234A, L235A, L235E, G237A, and combination thereof (numbering according to the EU index). E130. The PD-L1 antigen-binding protein of E129, comprising L234A and L235A mutations. E131. The PD-L1 antigen-binding protein of any one of E124-E130, wherein said Fc region is derived from an IgG Fc, and further comprises one or more mutations selection from the group consisting of: V259C, A287C, R292C, V302C, L306C, V323C, I332C, and a combination thereof (numbering according to the EU index). E131. The PD-L1 antigen-binding protein of any one of E124-E130, wherein said Fc region is derived from an IgG Fc, and further comprises one or more mutations selection from the group consisting of: L242C, A287C, R292C, N297G, V302C, L306C, K334C, and a combination thereof (numbering according to the EU index). E132. The PD-L1 antigen-binding protein of E131, comprising a N297G mutation. E133. The PD-L1 antigen-binding protein of E131, comprising A287C, N297G, and L306C mutations. E134. The PD-L1 antigen-binding protein of E131, comprising R292C, N297G, and V302C mutations. E135. The PD-L1 antigen-binding protein of any one of E124-E134, wherein said Fc region is derived from an IgG Fc, and further comprises one or more mutations selection from the group consisting of: M252Y, S254T, T256E, and a combination thereof. E136. The PD-L1 antigen-binding protein of E135, comprising M252Y, S254T, T256E mutations. E137. The PD-L1 antigen-binding protein of any one of E124-E136, wherein the lysine residue (K) at the C-terminus of the Fc region is deleted. E138. The PD-L1 antigen-binding protein of any one of E124-E136, wherein the lysine residue (K) at the C-terminus of the Fc region is present. E139. The PD-L1 antigen-binding protein of any one of E124-E136, wherein the glycine and lysine residues (GK) at the C-terminus of the Fc region are present. E140. The PD-L1 antigen-binding protein of any one of E124-E136, wherein the glycine and lysine residues (GK) at the C-terminus of the Fc region are deleted. E141. The PD-L1 antigen-binding protein of any one of E124-E140, wherein said Fc region comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 243, 250, 251, 252, 253, 254, 255, 413, 423, or 426. E142. The PD-L1 antigen-binding protein of any one of E124-E140, wherein said Fc region comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 263, 267, or 483. E143. The PD-L1 antigen-binding protein of any one of E103-E142, further comprising a heavy chain constant domain. E144. The PD-L1 antigen-binding protein of E143, wherein said constant domain is the constant domain of an IgA (for example IgA1 or lgA2), IgD, IgE, IgM, or IgG (for example IgG1, lgG2, lgG3, or lgG4). E145. The PD-L1 antigen-binding protein of E143 or E144, wherein said constant domain is the constant domain of an IgG (for example IgG1, IgG2, IgG3, or IgG4), preferably a human IgG (for example, human IgG1, human IgG2, human IgG3, or human IgG4). E146. The PD-L1 antigen-binding protein of any one of E143-E145, wherein said constant domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 244, 245, 246, 247, 248, 249, 256, 257, 258, 260, 412, 415, 417, 418, or 427. E147. The PD-L1 antigen-binding protein of any one of E143-E145, wherein said constant domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 264, 268, or 271. E148. The PD-L1 antigen-binding protein of any one of E103-E147, further comprising a kappa or lambda light chain constant domain. E149. The PD-L1 antigen-binding protein of any one of E103-E148, further comprising a kappa light chain constant domain that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 236, 237, 240, 414, 416, 419, 420, 421, or 428. E150. The PD-L1 antigen-binding protein of any one of E103-E148, further comprising a lambda light chain constant domain that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 238, 239, 241, or 424. E151. The PD-L1 antigen-binding protein of any one of E103-E150, comprising: (i) a heavy chain (HC) comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to any one of SEQ ID NOs: 177, 179, 181, 183, 185, 187, and 189; and (ii) a light chain (LC) comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to any one of SEQ ID NOs: 178, 180, 182, 184, 186, 188, and 190. E152. The PD-L1 antigen-binding protein of any one of E103-E151, comprising: (a) a heavy chain (HC) comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.177, and a light chain (LC) comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.178; (b) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.179, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.180; (c) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.181, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.182; (d) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.183, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.184; (e) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.185, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.186; (f) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.187, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.188; or (g) a HC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.189, and a LC comprising an amino acid sequence at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO.190. E153. The PD-L1 antigen-binding protein of any one of E103-E152, which is an antibody. E154. PD-L1 antigen-binding protein of any one of E103-E152, which is an antigen-binding fragment of an antibody, such as a Fab fragment. E155. The PD-L1 antigen-binding protein of any one of E103-E152, which is an scFv. E156. The PD-L1 antigen-binding protein of E155, wherein said scFv comprises a first linker between VH and VL. E157. The PD-L1 antigen-binding protein of E156, wherein said first linker comprises: (a) a glycine rich peptide; (b) a peptide comprising glycine and serine; (c) a peptide comprising (Gly-Gly-Ser)n, wherein n is 1 , 2, 3, 4, 5, or 6 (SEQ ID NO: 234); (d) a peptide comprising (Gly-Gly-Gly-Ser)n, wherein n is 1 , 2, 3, 4, 5, or 6 (SEQ ID NO: 232); (e) a peptide comprising (Gly-Gly-Gly-Gly-Ser)n, wherein n is 1 , 2, 3, 4, 5, or 6 (SEQ ID NO: 233); (f) a peptide comprising (Gly-Gly-Gly-Gly-Gln)n, wherein n is 1 , 2, 3, 4, 5, or 6 (SEQ ID NO: 235), or (g) a peptide comprising any one of SEQ ID NOs.221-235 and 504. E158. The PD-L1 antigen-binding protein of E156, wherein said first linker comprises the amino acid sequence of (Gly-Gly-Gly-Gly-Ser)3 (SEQ ID NO: 230). E159. The PD-L1 antigen-binding protein of any one of E155-E158, comprising a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 284 (26F6.002.009 scFv). E160. The PD-L1 antigen-binding protein of any one of E155-E158, comprising a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 436 (scFv from 56039). E161. The PD-L1 antigen-binding protein of any one of E103-E152, which is a Fab. E162. The PD-L1 antigen-binding protein of E161, comprising a Fab heavy chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to residues 1-221 SEQ ID NO: 451, and a Fab light chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 452 (Fab from 56041). E163. The PD-L1 antigen-binding protein of any one of E103-E162, wherein the protein binds PD-L1 with a KD value of or less than: about 10nM, about 5nM, about 2nM, about 1 nM, about 900pM, about 800pM, about 700pM, about 600pM, about 500pM, about 400pM, about 300pM, about 250pM, about 200pM, about 150pM, about 100pM, about 50pM, about 40pM, about 30pM, about 25pM, about 20pM, about 15pM, about 10pM, about 5pM, or about 1 pM. E164. A PD-L1 antigen-binding protein that competes for binding to PD-L1 with any one of the PD-L1 antigen binding protein of E103-E163. E165. A PD-L1 antigen-binding protein that binds to substantially the same epitope as any one of the PD-L1 antigen binding protein of E103-E163. E166. A bispecific molecule comprising the PD-L1 antigen-binding protein of any one of E103-E165, and further comprising a second antigen-binding moiety. E167. The bispecific molecule of E166, wherein the second antigen-binding moiety binds to a T-cell co- stimulatory molecule (such as: CD28, Inducible Co-Stimulator (ICOS), CTLA4 (Cytotoxic T-Lymphocyte- Associated protein 4), 4-1BB (also known as CD137), OX40 (also known as CD134), CD27, CD30, DR3, Glucocorticoid-Induced TNFR family Related (GITR), or Herpes Virus Entry Mediator (HVEM)). E168. The bispecific molecule of E167, wherein the T-cell co-stimulatory molecule is 4-1BB. E169. A bispecific molecule comprising (i) a 4-1BB antigen-binding moiety comprising any one of E1- E98 and E315-E342, and (ii) a PD-L1 antigen-binding moiety of any one of embodiments E103-E165. E170. A bispecific molecule, comprising: (i) two copies of a heavy chain that comprises, from N-terminus to C-terminus: VHA – CH1 – monomeric CH2 – monomeric CH3 – first linker - scFv, wherein said scFv comprises a VHBand a VLB, and wherein said VHBand VLBare connected via a second linker; and (ii) two copies of a light chain that comprises, from N-terminus to C-terminus: VLA – CL; wherein said VHA-CH1 and said VLA-CL form a Fab that binds to PD-L1, said scFv binds to 4-1BB, and said two copies of monomeric CH2 – monomeric CH3 form a Fc region. (IgG-scFv(C2), Fig.14A) E171. A bispecific molecule, comprising: (i) two copies of a heavy chain that comprises, from N-terminus to C-terminus: VHA – CH1 – monomeric CH2 – monomeric CH3 – first linker - scFv, wherein said scFv comprises a VHB and a VLB, and wherein said VHBand VLBare connected via a second linker; and (ii) two copies of a light chain that comprises, from N-terminus to C-terminus: VLA– CL; wherein said VHA-CH1 and said VLA-CL form a Fab that binds to 4-1BB, said scFv binds to PD-L1, and said two copies of monomeric CH2 – monomeric CH3 form a Fc region. (IgG-scFv(C2), Fig.14A) E172. A bispecific molecule, comprising: (i) two copies of a heavy chain that comprises, from N-terminus to C-terminus: VHA– CH1 – first linker – scFv – third linker – monomeric CH2 – monomeric CH3, wherein said scFv comprises a VHB and a VLB, and wherein said VHB and VLB are connected via a second linker; and (ii) two copies of a light chain that comprises, from N-terminus to C-terminus: VLA– CL; wherein said VHA-CH1 and said VLA-CL form a Fab that binds to PD-L1, said scFv binds to 4-1BB, and said two copies of monomeric CH2 – monomeric CH3 form a Fc region. (Fab-scFv(M2)-Fc, Fig.14B) E173. A bispecific molecule, comprising: (i) two copies of a heavy chain that comprises, from N-terminus to C-terminus: VHA– CH1 – first linker – scFv – third linker – monomeric CH2 – monomeric CH3, wherein said scFv comprises a VHB and a VLB, and wherein said VHB and VLB are connected via a second linker; and (ii) two copies of a light chain that comprises, from N-terminus to C-terminus: VLA – CL; wherein said VHA-CH1 and said VLA-CL form a Fab that binds to 4-1BB, said scFv binds to PD-L1, and said two copies of monomeric CH2 – monomeric CH3 form a Fc region. (Fab-scFv(M2)-Fc, Fig.14B) E174. A bispecific molecule, comprising: (i) two copies of a heavy chain that comprises, from N-terminus to C-terminus: VHA – CH1 – monomeric CH2 – monomeric CH3 – first linker – VHB– CH1’; and (ii) two copies of a first light chain that comprises, from N-terminus to C-terminus: VLA– CL; (iii) two copies of a second light chain that comprises, from N-terminus to C-terminus: VLB – CL’; wherein said VHA-CH1 and VLA-CL form a first Fab that binds to PD-L1, said VHB-CH1’ and VLB-CL’ form a second Fab that binds to 4-1BB, and said two copies of monomeric CH2 – monomeric CH3 form a Fc region. (IgG-Fab, Fig.2B) E175. A bispecific molecule, comprising: (i) two copies of a heavy chain that comprises, from N-terminus to C-terminus: VHA– CH1 – monomeric CH2 – monomeric CH3 – first linker – VHB– CH1’; and (ii) two copies of a first light chain that comprises, from N-terminus to C-terminus: VLA – CL; (iii) two copies of a second light chain that comprises, from N-terminus to C-terminus: VLB – CL’; wherein said VHA-CH1 and VLA-CL form a first Fab that binds to 4-1BB, said VHB-CH1’ and VLB-CL’ form a second Fab that binds to PD-L1, and said two copies of monomeric CH2 – monomeric CH3 form a Fc region. (IgG-Fab, Fig.2B) E176. The bispecific molecule of E174 or E175, wherein (i) said CH1 comprises a mutation to a positively charged residue and said CL comprises a mutation to a negatively charged residue, such that said CH1 and CL form a first charge pair, and (ii) said CH1’ comprises a mutation to a negatively charged residue and said CL’ comprises a mutation to a positively charged residue, such that said CH1’ and CL’ form a second charge pair. E177. The bispecific molecule of E176, wherein said CH1 comprises a mutation to K or R (preferably K) at position 183 (EU index numbering), or at a position that corresponds to residue 66 of SEQ ID NO:246. E178. The bispecific molecule of E176 or E177, wherein said CL comprises mutation to E or D (preferably E) at position 176 (Kabat numbering), or at a position that corresponds to residue 69 of SEQ ID NO:237 or 239. E179. The bispecific molecule of any one of E176- E178, wherein said CH1’ comprises a mutation to E or D (preferably E) at position 183 (EU index numbering), or at a position that corresponds to residue 66 of SEQ ID NO:246. E180. The bispecific molecule of any one of E176- E179, wherein said CL’ comprises a mutation to K or R (preferably K) at position 176 (Kabat numbering), or at a position that corresponds to residue 69 of SEQ ID NO:237 or 239. E181. The bispecific molecule of E174 or E175, wherein (i) said CH1 comprises a mutation to a negatively charged residue and said CL comprises a mutation to a positively charged residue, such that said CH1 and CL form a first charge pair, and (ii) said CH1’ comprises a mutation to a positively charged residue and said CL’ comprises a mutation to a negatively charged residue, such that said CH1’ and CL’ form a second charge pair. E182. The bispecific molecule of E181, wherein said CH1 comprises a mutation to E or D (preferably E) at position 183 (EU index numbering), or at a position that corresponds to residue 66 of SEQ ID NO:246. E183. The bispecific molecule of E181 or E182, wherein said CL comprises mutation to K or R (preferably R) at position 176 (Kabat numbering), or at a position that corresponds to residue 69 of SEQ ID NO:237 or 239. E184. The bispecific molecule of any one of E181- E183, wherein said CH1’ comprises a mutation to K or R (preferably K) at position 183 (EU index numbering), or at a position that corresponds to residue 66 of SEQ ID NO:246. E185. The bispecific molecule of any one of E181- E184, wherein said CL’ comprises a mutation to E or D (preferably E) at position 176 (Kabat numbering), or at a position that corresponds to residue 69 of SEQ ID NO:237 or 239. E186. A bispecific molecule, comprising: (i) two copies of a heavy chain that comprises, from N-terminus to C-terminus: VHA– CH1 – first linker – VHB – second linker – monomeric CH2 – monomeric CH3; and (ii) two copies of a light chain that comprises, from N-terminus to C-terminus: VLA – CL; wherein said VHA-CH1 and said VLA-CL form a Fab that binds to PD-L1, said VHBbinds to 4-1BB, and said two copies of monomeric CH2 – monomeric CH3 form a Fc region. (Fab-VH(M2)-Fc, Fig.14D). E187. A bispecific molecule, comprising: (i) two copies of a heavy chain that comprises, from N-terminus to C-terminus: VHA – CH1 – first linker – VHB– second linker – monomeric CH2 – monomeric CH3; and (ii) two copies of a light chain that comprises, from N-terminus to C-terminus: VLA– CL; wherein said VHA-CH1 and said VLA-CL form a Fab that binds to 4-1BB, said VHB binds to PD-L1, and said two copies of monomeric CH2 – monomeric CH3 form a Fc region. (Fab-VH(M2)-Fc, Fig.14D). E188. A bispecific molecule, comprising: (i) two copies of a heavy chain that comprises, from N-terminus to C-terminus: VHA– CH1 – monomeric CH2 – monomeric CH3 – first linker - VHB; and (ii) two copies of a light chain that comprises, from N-terminus to C-terminus: VLA – CL; wherein said VHA-CH1 and said VLA-CL form a Fab that binds to PD-L1, said VHBbinds to 4-1BB, and said two copies of monomeric CH2 – monomeric CH3 form a Fc region. (IgG-VH(C2), Fig.14C) E189. A bispecific molecule, comprising: (i) two copies of a heavy chain that comprises, from N-terminus to C-terminus: VHA – CH1 – monomeric CH2 – monomeric CH3 – first linker - VHB; and (ii) two copies of a light chain that comprises, from N-terminus to C-terminus: VLA– CL; wherein said VHA-CH1 and said VLA-CL form a Fab that binds to 4-1BB, said VHB binds to PD-L1, and said two copies of monomeric CH2 – monomeric CH3 form a Fc region. (IgG-VH(C2), Fig.14C) E190. A bispecific molecule, comprising: (i) a first heavy chain that comprises, from N-terminus to C-terminus: VHA– CH1 – monomeric CH2 – monomeric CH3 – first linker – scFv; wherein said scFv comprises a VHBand a VLB, and wherein said VHB and VLB are connected via a second linker; (ii) a second heavy chain that comprises, from N-terminus to C-terminus: VHA – CH1 – monomeric CH2’ – monomeric CH3’; and (iii) two copies of a light chain that comprises, from N-terminus to C-terminus: VLA– CL; wherein said VHA-CH1 and said VLA-CL form two Fab domains that binds to 4-1BB, said scFv binds to PD-L1, and said monomeric CH2 – monomeric CH3 from (i) and monomeric CH2’ – monomeric CH3’ from (ii) form a Fc region. (IgG-scFv(C1), Fig.13C) E191. A bispecific molecule, comprising: (i) a first heavy chain that comprises, from N-terminus to C-terminus: VHA – CH1 – monomeric CH2 – monomeric CH3 – first linker – scFv; wherein said scFv comprises a VHB and a VLB, and wherein said VHBand VLBare connected via a second linker (ii) a second heavy chain that comprises, from N-terminus to C-terminus: VHA– CH1 – monomeric CH2’ – monomeric CH3’; and (iii) two copies of a light chain that comprises, from N-terminus to C-terminus: VLA – CL; wherein said VHA-CH1 and said VLA-CL form two Fab domains that binds to PD-L1, said scFv binds to 4- 1BB, and said monomeric CH2 – monomeric CH3 from (i) and monomeric CH2’ – monomeric CH3’ from (ii) form a Fc region. (IgG-scFv(C1), Fig.13C) E192. A bispecific molecule, comprising: (i) a first heavy chain that comprises, from N-terminus to C-terminus: VHA– CH1 – first linker – scFv – third linker – monomeric CH2 – monomeric CH3; wherein said scFv comprises a VHBand a VLB, and wherein said VHB and VLB are connected via a second linker; (ii) a second heavy chain that comprises, from N-terminus to C-terminus: VHA – CH1 – monomeric CH2’ – monomeric CH3’; and (iii) two copies of a light chain that comprises, from N-terminus to C-terminus: VLA– CL; wherein said VHA-CH1 and said VLA-CL form two Fab domains that binds to 4-1BB, said scFv binds to PD-L1, and said monomeric CH2 – monomeric CH3 from (i) and monomeric CH2’ – monomeric CH3’ from (ii) form a Fc region. (Fab-scFv(M1)-Fc, Fig.13D) E193. A bispecific molecule, comprising: (i) a first heavy chain that comprises, from N-terminus to C-terminus: VHA – CH1 – first linker – scFv – third linker – monomeric CH2 – monomeric CH3; wherein said scFv comprises a VHB and a VLB, and wherein said VHBand VLBare connected via a second linker; (ii) a second heavy chain that comprises, from N-terminus to C-terminus: VHA – CH1 – monomeric CH2’ – monomeric CH3’; and (iii) two copies of a light chain that comprises, from N-terminus to C-terminus: VLA– CL; wherein said VHA-CH1 and said VLA-CL form two Fab domains that binds to PD-L1, said scFv binds to 4- 1BB, and said monomeric CH2 – monomeric CH3 from (i) and monomeric CH2’ – monomeric CH3’ from (ii) form a Fc region. (Fab-scFv(M1)-Fc, Fig.13D) E194. A bispecific molecule, comprising: (i) a first heavy chain that comprises, from N-terminus to C-terminus: VHA – CH1 – monomeric CH2 – monomeric CH3; (ii) a second heavy chain that comprises, from N-terminus to C-terminus: scFv – second linker – monomeric CH2’ – monomeric CH3’, wherein said scFv comprises a VHBand a VLB, and wherein said VHB and VLB are connected via a first linker; and (iii) a light chain that comprises, from N-terminus to C-terminus: VLA – CL; wherein said VHA-CH1 and said VLA-CL form a Fab that binds to PD-L1, said scFv binds to 4-1BB, and said monomeric CH2 – monomeric CH3 from (i) and monomeric CH2’ – monomeric CH3’ from (ii) form a Fc region. ([Fab*scFv] hetero-Fc, Fig.13G) E195. A bispecific molecule, comprising: (i) a first heavy chain that comprises, from N-terminus to C-terminus: VHA– CH1 – monomeric CH2 – monomeric CH3; (ii) a second heavy chain that comprises, from N-terminus to C-terminus: scFv – second linker – monomeric CH2’ – monomeric CH3’, wherein said scFv comprises a VHB and a VLB, and wherein said VHBand VLBare connected via a first linker; and (iii) a light chain that comprises, from N-terminus to C-terminus: VLA– CL; wherein said VHA-CH1 and said VLA-CL form a Fab that binds to 4-1BB, said scFv binds to PD-L1, and said monomeric CH2 – monomeric CH3 from (i) and monomeric CH2’ – monomeric CH3’ from (ii) form a Fc region. ([Fab*scFv] hetero-Fc, Fig.13G) E196. A bispecific molecule, comprising: (i) a first heavy chain that comprises, from N-terminus to C-terminus: VHA – CH1 – monomeric CH2 – monomeric CH3; (ii) a second heavy chain that comprises, from N-terminus to C-terminus: VHB– first linker – monomeric CH2’ – monomeric CH3’; and (iii) a light chain that comprises, from N-terminus to C-terminus: VLA – CL; wherein said VHA-CH1 and said VLA-CL form a Fab that binds to PD-L1, said VHB binds to 4-1BB, and said monomeric CH2 – monomeric CH3 from (i) and monomeric CH2’ – monomeric CH3’ from (ii) form a Fc region. ([Fab*VH] hetero-Fc, Fig.13H) E197. A bispecific molecule, comprising: (i) a first heavy chain that comprises, from N-terminus to C-terminus: VHA– CH1 – monomeric CH2 – monomeric CH3; (ii) a second heavy chain that comprises, from N-terminus to C-terminus: VHB – first linker – monomeric CH2’ – monomeric CH3’; and (iii) a light chain that comprises, from N-terminus to C-terminus: VLA– CL; wherein said VHA-CH1 and said VLA-CL form a Fab that binds to 4-1BB, said VHBbinds to PD-L1, and said monomeric CH2 – monomeric CH3 from (i) and monomeric CH2’ – monomeric CH3’ from (ii) form a Fc region. ([Fab*VH] hetero-Fc, Fig.13H) E198. A bispecific molecule, comprising: (i) a first heavy chain that comprises, from N-terminus to C-terminus: scFv – second linker – VHA– CH1 – monomeric CH2 – monomeric CH3, wherein said scFv comprises a VHB and a VLB, and wherein said VHB and VLB are connected via a first linker; (ii) a second heavy chain that comprises, from N-terminus to C-terminus: VHA– CH1 – monomeric CH2’ – monomeric CH3’; and (iii) two copies of a light chain that comprises, from N-terminus to C-terminus: VLA – CL; wherein said VHA-CH1 and said VLA-CL form a Fab that binds to PD-L1, said scFv binds to 4-1BB, and said monomeric CH2 – monomeric CH3 from (i) and monomeric CH2’ – monomeric CH3’ from (ii) form a Fc region. (scFv(N1)-IgG, Fig.13J) E199. A bispecific molecule, comprising: (i) a first heavy chain that comprises, from N-terminus to C-terminus: scFv – second linker – VHA – CH1 – monomeric CH2 – monomeric CH3, wherein said scFv comprises a VHBand a VLB, and wherein said VHBand VLBare connected via a first linker; (ii) a second heavy chain that comprises, from N-terminus to C-terminus: VHA – CH1 – monomeric CH2’ – monomeric CH3’; and (iii) two copies of a light chain that comprises, from N-terminus to C-terminus: VLA– CL; wherein said VHA-CH1 and said VLA-CL form a Fab that binds to 4-1BB, said scFv binds to PD-L1, and said monomeric CH2 – monomeric CH3 from (i) and monomeric CH2’ – monomeric CH3’ from (ii) form a Fc region. (scFv(N1)-IgG, Fig.13J) E200. A bispecific molecule, comprising: (i) a first heavy chain that comprises, from N-terminus to C-terminus: scFv – second linker – monomeric CH2(1)– monomeric CH3(1), wherein said scFv comprises a VHB and a VLB, and wherein said VHB and VLB are connected via a first linker; (ii) a second heavy chain that comprises, from N-terminus to C-terminus: VHA– CH1 – monomeric CH2(2)– monomeric CH3(2)– monomeric CH2(3)– monomeric CH3(3); (iii) a light chain that comprises, from N-terminus to C-terminus: VLA – CL; and (iv) a fourth chain comprising monomeric CH2(4)– monomeric CH3(4); wherein said VHA-CH1 and said VLA-CL form a Fab that binds to PD-L1, said scFv binds to 4-1BB, said monomeric CH2(1)– monomeric CH3(1)from (i) and monomeric CH2(2)– monomeric CH3(2)from (ii) form a first Fc region, and said monomeric CH2(3)– monomeric CH3(3)from (ii) and monomeric CH2(4)– monomeric CH3(4)from (iv) form a second Fc region. ([scFv*Fab] hetero-Fc)-Fc, (Fig.13K) E201. A bispecific molecule, comprising: (i) a first heavy chain that comprises, from N-terminus to C-terminus: scFv – second linker – monomeric CH2(1)– monomeric CH3(1), wherein said scFv comprises a VHB and a VLB, and wherein said VHBand VLBare connected via a first linker; (ii) a second heavy chain that comprises, from N-terminus to C-terminus: VHA– CH1 – monomeric CH2(2)– monomeric CH3(2)– monomeric CH2(3)– monomeric CH3(3); (iii) a light chain that comprises, from N-terminus to C-terminus: VLA – CL; and (iv) a fourth chain comprising monomeric CH2(4)– monomeric CH3(4); wherein said VHA-CH1 and said VLA-CL form a Fab that binds to 4-1BB, said scFv binds to PD-L1, said monomeric CH2(1)– monomeric CH3(1)from (i) and monomeric CH2(2)– monomeric CH3(2)from (ii) form a first Fc region, and said monomeric CH2(3)– monomeric CH3(3)from (ii) and monomeric CH2(4)– monomeric CH3(4)from (iv) form a second Fc region. ([scFv*Fab] hetero-Fc)-Fc, (Fig.13K) E202. A bispecific molecule, comprising: (i) a first heavy chain that comprises, from N-terminus to C-terminus: VHA – CH1 – monomeric CH2 – monomeric CH3; (ii) a second heavy chain that comprises, from N-terminus to C-terminus: VHB– CH1’ – monomeric CH2’ – monomeric CH3’; (iii) a first light chain that comprises, from N-terminus to C-terminus: VLA – CL; and (iv) a second light chain that comprises, from N-terminus to C-terminus: VLB – CL’; wherein said VHA-CH1 and said VLA-CL form a first Fab that binds to 4-1BB, wherein said VHB-CH1’ and said VLB-CL’ form a second Fab that to PD-L1, and wherein said monomeric CH2 – monomeric CH3 from (i) and monomeric CH2’ – monomeric CH3’ from (ii) form a Fc region. (hetero-IgG, Fig.13I) E203. A bispecific molecule, comprising: (i) a first heavy chain that comprises, from N-terminus to C-terminus: VHA– CH1 – monomeric CH2 – monomeric CH3; (ii) a second heavy chain that comprises, from N-terminus to C-terminus: VHB – CH1’ – monomeric CH2’ – monomeric CH3’; (iii) a first light chain that comprises, from N-terminus to C-terminus: VLA– CL; and (iv) a second light chain that comprises, from N-terminus to C-terminus: VLB– CL’; wherein said VHA-CH1 and said VLA-CL form a first Fab that binds to PD-L1, wherein said VHB-CH1’ and said VLB-CL’ form a second Fab that to 4-1BB, and wherein said monomeric CH2 – monomeric CH3 from (i) and monomeric CH2’ – monomeric CH3’ from (ii) form a Fc region. (hetero-IgG, Fig.13I) E204. The bispecific molecule of any one of E202 or E203, wherein (i) said CH1 comprises a mutation to a positively charged residue and said CL comprises a mutation to a negatively charged residue, such that said CH1 and CL form a first charge pair, and (ii) said CH1’ comprises a mutation to a negatively charged residue and said CL’ comprises a mutation to a positively charged residue, such that said CH1’ and CL’ form a second charge pair. E205. The bispecific molecule of E204, wherein said CH1 comprises a mutation to K or R (preferably K) at position 183 (EU index numbering), or at a position that corresponds to residue 66 of SEQ ID NO:246. E206. The bispecific molecule of E204 or E205, wherein said CL comprises mutation to E or D (preferably E) at position 176 (Kabat numbering), or at a position that corresponds to residue 69 of SEQ ID NO:237 or 239. E207. The bispecific molecule of any one of E204- E206, wherein said CH1’ comprises a mutation to E or D (preferably E) at position 183 (EU index numbering), or at a position that corresponds to residue 66 of SEQ ID NO:246. E208. The bispecific molecule of any one of E204- E207, wherein said CL’ comprises a mutation to K or R (preferably K) at position 176 (Kabat numbering), or at a position that corresponds to residue 69 of SEQ ID NO:237 or 239. E209. The bispecific molecule of E202 or E203, wherein (i) said CH1 comprises a mutation to a negatively charged residue and said CL comprises a mutation to a positively charged residue, such that said CH1 and CL form a first charge pair, and (ii) said CH1’ comprises a mutation to a positively charged residue and said CL’ comprises a mutation to a negatively charged residue, such that said CH1’ and CL’ form a second charge pair. E210. The bispecific molecule of E209, wherein said CH1 comprises a mutation to E or D (preferably E) at position 183 (EU index numbering), or at a position that corresponds to residue 66 of SEQ ID NO:246. E211. The bispecific molecule of E209 or E210, wherein said CL comprises mutation to K or R (preferably R) at position 176 (Kabat numbering), or at a position that corresponds to residue 69 of SEQ ID NO:237 or 239. E212. The bispecific molecule of any one of E209- E211, wherein said CH1’ comprises a mutation to K or R (preferably K) at position 183 (EU index numbering), or at a position that corresponds to residue 66 of SEQ ID NO:246. E213. The bispecific molecule of any one of E209- E212, wherein said CL’ comprises a mutation to E or D (preferably E) at position 176 (Kabat numbering), or at a position that corresponds to residue 69 of SEQ ID NO:237 or 239. E214. The bispecific molecule of any one of E190- E213, wherein said CH2, or CH2’, or CH2(1), or CH2(2), or CH2(3), or CH2(4)comprises a mutation wherein a positively charged residue is mutated to a negatively charge residue, or a mutation wherein a negatively charged residue is mutated to a positively charge residue. E215. The bispecific molecule of any one of E190- E214, wherein said CH3, or CH3’, or CH3(1), or CH3(2), or CH3(3), or CH3(4)comprises a mutation wherein a positively charged residue is mutated to a negatively charge residue, or a mutation wherein a negatively charged residue is mutated to a positively charge residue. E216. The bispecific molecule of any one of E190- E215, wherein said CH3, or CH3’, or CH3(1), or CH3(2), or CH3(3), or CH3(4)comprises a mutation from K to E or D (preferably D) at position 392 (EU index numbering), or at a position that corresponds to residue 275 of SEQ ID NO:246. E217. The bispecific molecule of any one of E190- E216, wherein said CH3, or CH3’, or CH3(1), or CH3(2), or CH3(3), or CH3(4)comprises a mutation from K to D or E (preferably D) at position 409 (EU index numbering), or at a position that corresponds to residue 292 of SEQ ID NO:246. E218. The bispecific molecule of any one of E190- E217, wherein said CH3, or CH3’, or CH3(1), or CH3(2), or CH3(3), or CH3(4)comprises a mutation from K to E or D (preferably D) at position 439 (EU index numbering), or at a position that corresponds to residue 322 of SEQ ID NO:246. E219. The bispecific molecule of any one of E170- E219, wherein said CH1 or CH1’ is the CH1 domain of a human IgG (for example, human IgG1, human IgG2, human IgG3, or human IgG4). E220. The PD-L1 antigen-binding protein of any one of E170-E219, wherein said CH1 or CH1’ domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 242, 259, 261, 265, 269, 422, or 425. E221. The bispecific molecule of any one of E170-E220, wherein said CH1 or CH1’ domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 242, 259, 422, or 425. E222. The bispecific molecule of any one of E170-E221, wherein said Fc is the Fc region of an IgG. E223. The bispecific molecule of E222, wherein the IgG is selected from the group consisting of IgG1, lgG2, lgG3, and lgG4. E224. The bispecific molecule of E223, wherein the IgG is IgG1, IgG2, or IgG4. E225. The bispecific molecule of any one of E170-E224, wherein said Fc is derived from an IgG Fc, and further comprises one or more mutations selection from the group consisting of: L234A, L235A, L235E, G237A, and combination thereof (numbering according to the EU index). E226. The bispecific molecule of E225, comprising L234A and L235A mutations. E227. The bispecific molecule of any one of E170-E226, wherein said Fc region is derived from an IgG Fc, and further comprises one or more mutations selection from the group consisting of: V259C, A287C, R292C, V302C, L306C, V323C, I332C, and a combination thereof (numbering according to the EU index). E228. The bispecific molecule of any one of E170-E227, wherein said Fc region is derived from an IgG Fc, and further comprises one or more mutations selection from the group consisting of: L242C, A287C, R292C, N297G, V302C, L306C, K334C, and a combination thereof (numbering according to the EU index). E229. The bispecific molecule of E228, comprising a N297G mutation. E230. The bispecific molecule of E228, comprising A287C, N297G, and L306C mutations. E231. The bispecific molecule of E228, comprising R292C, N297G, and V302C mutations. E232. The bispecific molecule of any one of E170-E231, wherein said Fc region is derived from an IgG Fc, and further comprises one or more mutations selection from the group consisting of: M252Y, S254T, T256E, and a combination thereof. E233. The bispecific molecule of E232, comprising M252Y, S254T, T256E mutations. E234. The bispecific molecule of any one of E170-E233, wherein the lysine residue (K) at the C- terminus of the Fc region is deleted. E235. The bispecific molecule of any one of E170-E233, wherein the lysine residue (K) at the C- terminus of the Fc region is present. E236. The bispecific molecule of any one of E170-E233, wherein the glycine and lysine residues (GK) at the C-terminus of the Fc region are present. E237. The bispecific molecule of any one of E170-E233, wherein the glycine and lysine residues (GK) at the C-terminus of the Fc region are deleted. E238. The bispecific molecule of any one of E170-E237, wherein said Fc comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 243, 250, 251, 252, 253, 254, 255, 413, 423, or 426. E239. The bispecific molecule of any one of E170-E237, wherein said Fc region comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 263, 267, or 483. E240. The bispecific molecule of any one of E170-E239, wherein said CL or CL’ is a kappa or lambda light chain constant domain. E241. The bispecific molecule of any one of E170-E240, wherein said CL or CL’ is a kappa light chain constant domain that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 236, 237, 240, 414, 416, 419, 420, 421, or 428. E242. The bispecific molecule of any one of E170-E241, wherein said CL or CL’ a lambda light chain constant domain that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 238, 239, 241, or 424. E243. The bispecific molecule of any one of E170-E242, comprising a 4-1BB antigen-binding protein of any one of E1-E98 and E315-E342. E244. The bispecific molecule of any one of E170-E243, comprising PD-L1 antigen-binding protein of any one of E103-E165. E245. The bispecific molecule of any one of E170-E244, wherein said first linker, second linker, or third linker, each independently comprises: (a) a glycine rich peptide; (b) a peptide comprising glycine and serine; (c) a peptide comprising (Gly-Gly-Ser)n, wherein n is 1 , 2, 3, 4, 5, or 6 (SEQ ID NO: 234); (d) a peptide comprising (Gly-Gly-Gly-Ser)n, wherein n is 1 , 2, 3, 4, 5, or 6 (SEQ ID NO: 232); (e) a peptide comprising (Gly-Gly-Gly-Gly-Ser)n, wherein n is 1 , 2, 3, 4, 5, or 6 (SEQ ID NO: 233); (f) a peptide comprising (Gly-Gly-Gly-Gly-Gln)n, wherein n is 1 , 2, 3, 4, 5, or 6 (SEQ ID NO: 235), or (g) a peptide comprising any one of SEQ ID NOs.221-235 and 504. E246. The bispecific molecule of any one of E170-E245, wherein said first linker, second linker, or third linker, each independently comprises: (a) GGGG (SEQ ID NO: 222); (b) GGGGSGGGGSGGGGS (SEQ ID NO: 230); (c) GGGGQGGGGQ (SEQ ID NO: 504); or (d) GGGGSGGGGS (SEQ ID NO: 229). E247. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 283, and (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 220. E248. A bispecific molecule comprising two copies of SEQ ID NO: 283, and two copies of SEQ ID NO: 220. (clone 11250) E249. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 287, and (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 206. E250. A bispecific molecule comprising two copies of SEQ ID NO: 287, and two copies of SEQ ID NO: 206. (clone 11252) E251. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 290, and (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 184. E252. A bispecific molecule comprising two copies of SEQ ID NO: 290, and two copies of SEQ ID NO: 184. (clone 11253) E253. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 294, and (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 186. E254. A bispecific molecule comprising two copies of SEQ ID NO: 294, and two copies of SEQ ID NO: 186. (clone 11255). E255. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 297; (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 299; and (iii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 300. E256. A bispecific molecule comprising two copies of SEQ ID NO: 297, two copies of SEQ ID NO: 299, and two copies of SEQ ID NO: 300. (clone 11259) E257. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 304; (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 306; and (iii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 307. E258. A bispecific molecule comprising two copies of SEQ ID NO: 304, two copies of SEQ ID NO: 306, and two copies of SEQ ID NO: 307. (clone 11258) E259. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 311; (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 312; and (iii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 307. E260. A bispecific molecule comprising two copies of SEQ ID NO: 311, two copies of SEQ ID NO: 312, and two copies of SEQ ID NO: 307. (clone 11262) E261. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 315; (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 312; and (iii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 317. E262. A bispecific molecule comprising two copies of SEQ ID NO: 315, two copies of SEQ ID NO: 312, and two copies of SEQ ID NO: 317. (clone 11264) E263. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 320; (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 312; and (iii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 300. E264. A bispecific molecule comprising two copies of SEQ ID NO: 320, two copies of SEQ ID NO: 312, and two copies of SEQ ID NO: 300. (clone 11265) E265. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 443, and (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 444. E266. A bispecific molecule comprising two copies of SEQ ID NO: 443, and two copies of SEQ ID NO: 444. (clone 44988) E267. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 434, and (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 435. E268. A bispecific molecule comprising two copies of SEQ ID NO: 434, and two copies of SEQ ID NO: 435. (clone 56039) E269. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 449, and (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 450. E270. A bispecific molecule comprising two copies of SEQ ID NO: 449, and two copies of SEQ ID NO: 450. (clone 56040) E271. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 451, and (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 452. E272. A bispecific molecule comprising two copies of SEQ ID NO: 451, and two copies of SEQ ID NO: 452. (clone 56041) E273. A bispecific molecule comprising (i) an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 437, (ii) an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 438, (iii) an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 439, and (iv) an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 440. E274. A bispecific molecule comprising: one copy of SEQ ID NO: 449, one copy of SEQ ID NO: 450, one copy of SEQ ID NO:439, and one copy of SEQ ID NO: 440. (clone 56042) E275. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 432, and (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 433. E276. A bispecific molecule comprising two copies of SEQ ID NO: 432, and two copies of SEQ ID NO: 433. (clone 56132) E277. A bispecific molecule comprising (i) an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 446, (ii) an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 447, and (iii) an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 448. E278. A bispecific molecule comprising: one copy of SEQ ID NO: 446, one copy of SEQ ID NO: 447, and one copy of SEQ ID NO: 448. (clone 56639) E279. A bispecific molecule comprising (i) an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 429, (ii) an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 430, and (iii) an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 431. E280. A bispecific molecule comprising: one copy of SEQ ID NO: 429, one copy of SEQ ID NO: 430, and one copy of SEQ ID NO: 431. (clone 56761) E281. A bispecific molecule comprising (i) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 442, and (ii) two copies of an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical SEQ ID NO: 441. E282. A bispecific molecule comprising two copies of SEQ ID NO: 442, and two copies of SEQ ID NO: 441. (clone 56762) E283. The bispecific molecule of any one of E99-E102 and E166-E282, wherein said bispecific molecule is a crosslinking dependent agonist of 4-1BB. E284. The bispecific molecule of any one of E99-E102 and E166-E282, wherein said bispecific molecule activates 4-1BB upon binding to PD-L1. E285. A nucleic acid comprising a nucleotide sequence encoding the 4-1BB antigen-binding protein of any one of E1-E98 and E319-E346, the PD-L1 antigen-binding protein of any one of E103-E165, the bispecific molecule of any one of E99-E102 and E166-E284, or one of the polypeptide chains of any one of the foregoing. E286. The nucleic acid of E285, comprising a nucleotide sequence that is at least 80%, at least 81%, at least 82%, at least 83%, at least 84%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical any one of SEQ ID NOs: 285, 286, 288, 289, 292, 293, 295, 296, 301, 302, 303, 308, 309, 310, 313, 314, 318, 319, 321, 466, 467, 458, 459, 471, 472, 473, 505, 460, 462, 461, 463, 456, 457, 468, 469, 470, 453, 454, 455, 464, and 465. E287. A vector comprising the nucleic acid of E285 or E286. E288. A host cell comprising the nucleic acid of E285 or E286, or the vector of E287. E289. The host cell of E288, wherein said host cell is a mammalian cell. E290. The host cell of E289, wherein said host cell is a CHO cell or a HEK-293 cell, or an Sp2.0 cell. E291. A kit comprising (i) the 4-1BB antigen-binding protein of any one of E1-E98 and E319-E346, the PD-L1 antigen-binding protein of any one of E103-E165, the bispecific molecule of any one of E99-E102 and E166-E284, the nucleic acid of E285 or E286, the vector of E287, the host cell of E288-E290, or a combination thereof; and (ii) instructions for use. E292. A pharmaceutical composition comprising (i) the 4-1BB antigen-binding protein of any one of E1- E98 and E319-E346, the PD-L1 antigen-binding protein of any one of E103-E165, the bispecific molecule of any one of E99-E102 and E166-E284, the nucleic acid of E285 or E286, the vector of E287, the host cell of E288-E290, or a combination thereof; and (ii) a pharmaceutically acceptable carrier, excipient, or diluent. E293. A method of making the 4-1BB antigen-binding protein of any one of E1-E98 and E319-E346, the PD-L1 antigen-binding protein of any one of E103-E165, or the bispecific molecule of any one of E99- E102 and E166-E284, comprising culturing the host cell of any one of E288-E290, under a condition wherein the 4-1BB antigen-binding protein, the PD-L1 antigen-binding protein, or the bispecific molecule, is expressed. E294. The method of E293, further comprising harvesting the expressed the 4-1BB antigen-binding protein of any one of E1-E98 and E319-E346, the PD-L1 antigen-binding protein of any one of E103- E165, or the bispecific molecule of any one of E99-E102 and E166-E284. E295. A method of treating cancer, comprising administering to a subject in need thereof a therapeutically effective amount of the 4-1BB antigen-binding protein of any one of E1-E98 and E319- E346, the PD-L1 antigen-binding protein of any one of E103-E165, the bispecific molecule of any one of E99-E102 and E166-E284, or the pharmaceutical composition of E292. E296. The method of E295, wherein cancer is solid tumor. E297. The method of E295 or E296, wherein said subject is a human. E298. The method of any one of E295-E297, wherein said cancer comprises cells that express PD-L1. E299. The method of any one of E295-E298, wherein the cancer is brain cancer, bladder cancer, breast cancer, clear cell kidney cancer, cervical cancer, colon cancer, rectal cancer, endometrial cancer, gastric cancer, head / neck squamous cell carcinoma, lip cancer, oral cancer, liver cancer, lung squamous cell carcinoma, melanoma, mesothelioma, non-small-cell lung cancer (NSCLC), non-melanoma skin cancer, ovarian cancer, pancreatic cancer, prostate cancer, renal cell carcinoma, sarcoma, small-cell lung cancer (SCLC), Squamous Cell Carcinoma of the Head and Neck (SCCHN), triple negative breast cancer, renal cell carcinoma, or thyroid cancer. E300. The method of any one of E295-E298, wherein the cancer is adrenocortical tumor, alveolar soft part sarcoma, carcinoma, chondrosarcoma, desmoid tumors, desmoplastic small round cell tumor, endocrine tumors, endodermal sinus tumor, epithelioid hemangioendothelioma, Ewing sarcoma, germ cell tumor, hepatoblastoma, hepatocellular carcinoma, melanoma, nephroma, neuroblastoma, non- rhabdomyosarcoma soft tissue sarcoma (NRSTS), osteosarcoma, paraspinal sarcoma, retinoblastoma, rhabdomyosarcoma, synovial sarcoma, or Wilms tumor. E301. The method of any one of E295-E298, wherein the cancer is acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), or chronic myeloid leukemia (CML). E302. The method of any one of E295-E298, wherein the cancer is diffuse large B-cell lymphoma (DLBCL), follicular lymphoma, Hodgkin's lymphoma (HL), mantle cell lymphoma (MCL), multiple myeloma (MM), myelodysplastic syndrome (MDS), non-Hodgkin's lymphoma (NHL), or small lymphocytic lymphoma (SLL). E303. The method of any one of E295-E302, wherein said 4-1BB antigen-binding protein, PD-L1 antigen-binding protein, bispecific molecule, or pharmaceutical composition is administered intravenously. E304. The method of any one of E295-E302, wherein said 4-1BB antigen-binding protein, PD-L1 antigen-binding protein, bispecific molecule, or pharmaceutical composition is administered subcutaneously. E305. The method of any one of E295-E302, wherein said 4-1BB antigen-binding protein, PD-L1 antigen-binding protein, bispecific molecule, fusion protein, polypeptide, or pharmaceutical composition is administered about twice a week, once a week, once every two weeks, once every three weeks, once every four weeks, once every five weeks, once every six weeks, once every seven weeks, once every eight weeks, once every nine weeks, once every ten weeks, twice a month, once a month, once every two months, once every three months, or once every four months. E306. The 4-1BB antigen-binding protein of any one of E1-E98 and E319-E346, the PD-L1 antigen- binding protein of any one of E103-E165, the bispecific molecule of any one of E99-E102 and E166- E284, or the pharmaceutical composition of E292 for use as a medicament. E307. The 4-1BB antigen-binding protein of any one of E1-E98 and E319-E346, the PD-L1 antigen- binding protein of any one of E103-E165, the bispecific molecule of any one of E99-E102 and E166- E284, or the pharmaceutical composition of E292 for use in treating cancer in a subject. E308. Use of the 4-1BB antigen-binding protein of any one of E1-E98 and E319-E346, the PD-L1 antigen-binding protein of any one of E103-E165, the bispecific molecule of any one of E99-E102 and E166-E284, or the pharmaceutical composition of E292 in the manufacture of a medicament for treating cancer in a subject. E309. Use of the 4-1BB antigen-binding protein of any one of E1-E98 and E319-E346, the PD-L1 antigen-binding protein of any one of E103-E165, the bispecific molecule of any one of E99-E102 and E166-E284, or the pharmaceutical composition of E292 for treating cancer in a subject. E310. A method of assessing immunogenicity of a bispecific molecule, wherein said immunogenicity is attributed to a T-cell epitope, and wherein said bispecific molecule comprises two domains: (1) a first domain that binds to a Dendritic Cell (DC) surface antigen; and (2) a second domain that binds to a T cell co-stimulatory molecule, the method comprises: (a) obtaining a first protein that comprises said first domain but does not comprise said second domain; (b) obtaining a second protein that comprises said second domain but does not comprise said first domain; (c) incubating said first protein and second protein with a cell culture that comprises DCs and T cells; and (d) assessing the activation or proliferation of T cells, wherein the activation or proliferation of T cells is indicative that said bispecific molecule comprises an immunogenic T cell epitope. E311. The method of E310, wherein said DC surface antigen is PD-L1. E312. The method of E311, wherein said DC surface antigen is CD8A, CLEC9A, ITGAE, ITGAX, THBD (CD141), XCR, CD1C, CD207, ITGAM, NOTCH2, SIRPA, CLEC4C, LILRB4, NRP1, CCR7, CD14, MRC1 (CD206), CD209, or CD1A. E313. The method of any one of E310-E312, wherein said T-cell co-stimulatory molecule is CD28, Inducible Co-Stimulator (ICOS), CTLA4 (Cytotoxic T-Lymphocyte-Associated protein 4), 4-1BB (also known as CD137), OX40 (also known as CD134), CD27, CD30, DR3, Glucocorticoid-Induced TNFR family Related (GITR), or Herpes Virus Entry Mediator (HVEM). E314. The method of any one of E310-E313, wherein said T-cell co-stimulatory molecule is 4-1BB. E315. The method of any one of E310-E314, wherein said first protein further comprise an IgG Fc domain. E316. The method of any one of E310-E315, wherein said second protein further comprise an IgG Fc domain. E317. The method of E315 or E316, wherein said Fc domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 243, 250, 251, 252, 253, 254, 255, 413, 423, or 426. E318. The method of E315 or E316, wherein said Fc domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 263, 267, or 483. E319. A 4-1BB antigen-binding protein, comprising a heavy chain variable domain (VH) and does not comprise light chain variable domain (VL), wherein said protein binds to an epitope that comprises residues C102, V71, and Q104, according to the numbering of SEQ ID NO:272. E320. The 4-1BB antigen-binding protein of E319, wherein said epitope further comprises residue P90, according to the numbering of SEQ ID NO:272. E321. The 4-1BB antigen-binding protein of E319 or E320, wherein said epitope further comprises one or more residues selected from the group consisting of: K69, T89, F92, M101, and L112, according to the numbering of SEQ ID NO:272. E322. The 4-1BB antigen-binding protein of any one of E319-E321, wherein said epitope further comprises residues K69, T89, F92, M101, and L112, according to the numbering of SEQ ID NO:272. E323. The 4-1BB antigen-binding protein of any one of E319-E322, wherein one or more of the following substitutions substantially disrupts the binding of said antigen-binding protein to said epitope: (1) C102 is replaced by A; (2) Q104 is replaced by A; or (3) K69 is replaced by A. E324. The 4-1BB antigen-binding protein of any one of E319-E313, wherein said antigen-binding protein binds to said epitope with a binding affinity (KD) value that is at least 100-fold less, at least 200-fold less, at least 300-fold less, at least 400-fold less, at least 500-fold less, at least 600-fold less, at least 700-fold less, at least 800-fold less, at least 900-fold less, or at least 1000-fold less, than its KD value for an epitope comprising one or more of the following substitutions: (1) C102 is replaced by A; (2) Q104 is replaced by A; or (3) K69 is replaced by A. E325. The 4-1BB antigen-binding protein of E323 or E324, wherein said KD value is measured by surface plasmon resonance (SPR), optionally using a Biacore T200 instrument. E326. The 4-1BB antigen-binding protein of E323 or E324, wherein said KD value is measured by bio- layer interferometry (BLI), optionally using a ForteBio Octet instrument. E327. The 4-1BB antigen-binding protein of any one of E319-E326, wherein said 4-1BB is a human 4- 1BB. E328. The 4-1BB antigen-binding protein of E327, wherein said 4-1BB comprises SEQ ID NO:566. E329. The 4-1BB antigen-binding protein of any one of E319-E328, wherein said epitope is determined by X-ray crystallography or cryoEM. E330. The 4-1BB antigen-binding protein of any one of E319-E329, wherein said VH comprises (VH numbering according to Kabat): (1) H45 is Leu, Phe, Ile, or Tyr; (2) H47 is Trp, Phe, Leu, or Tyr; (3) H100B is Tyr, Arg, His, Lys, or Met; (4) H100D is Thr, Ala, Asn, Cys, Gln, Lys, Met, or Val; and (5) H100F is Phe, Trp or Tyr. E331. The 4-1BB antigen-binding protein of any one of E319-E330, wherein said VH comprises (VH numbering according to Kabat): (1) H45 is Leu or Phe; (2) H47 is Trp or Leu; (3) H100B is Tyr or Met; (4) H100D is Thr or Val; and (5) H100F is Phe or Trp. E332. The 4-1BB antigen-binding protein of any one of E319-E331, wherein said VH comprises (VH numbering according to Kabat): (1) H45 is Leu; (2) H47 is Trp; (3) H100B is Tyr; (4) H100D is Thr; and (5) H100F is Phe. E333. The 4-1BB antigen-binding protein of any one of E319-E332, wherein said VH comprises (VH numbering according to Kabat): (6) H97 is Ser, Arg, Asn, Gln, Glu, His,,Leu, Lys, Met, Phe, Thr, Trp, Tyr, or Val; (7) H100E is Ser, Ala, Asn, Asp, Cys, His, Trp, Tyr, or Val; and (9) H102 is Tyr, Ile, Lys, or Val. E334. The 4-1BB antigen-binding protein of any one of E319-E333, wherein said VH comprises (VH numbering according to Kabat): (6) H97 is Ser or Leu; (7) H100E is Ser or Val; and (9) H102 is Tyr or Lys. E335. The 4-1BB antigen-binding protein of any one of E319-E334, wherein said VH comprises (VH numbering according to Kabat): (6) H97 is Ser; (7) H100E is Ser; and (9) H102 is Tyr. E336. The 4-1BB antigen-binding protein of any one of E319-E335, wherein: (a) said VH comprises: (i) a CDR-H3 comprising any one of SEQ ID NOs:576-578 and 580; and (ii) framework residue H45 is Leu and framework residue H47 is Trp; or (b) said VH comprise: (i) a CDR-H2 comprising SEQ ID NO:574, (ii) a CDR-H3 comprising SEQ ID NO: 579; and (iii) framework residue H45 is Leu. E337. The 4-1BB antigen-binding protein of E336, wherein said CDR-H3 and framework residues contact one or more 4-1BB residues selected from the group consisting of: C102, V71, Q104, P90, K69, T89, F92, M101, and L112 (numbering according to SEQ ID NO:272). E338. The 4-1BB antigen-binding protein of E337, wherein said contacting is defined as within 4.5Å distance between a heavy atom in 4-1BB and a heavy atom in the 4-1BB antigen-binding protein, as determined by X-ray crystallography or cyroEM. E339. The 4-1BB antigen-binding protein of any one of E319-E338, comprising a VH framework derived from a human germline VH1, VH2, VH3, VH4, or VH5 framework sequence. E340. The 4-1BB antigen-binding protein of any one of E310-E338, comprising a VH framework derived from a human germline VH1 framework sequence. E341. The 4-1BB antigen-binding protein of any one of E319-E338, comprising a VH framework derived from a human germline VH3 framework sequence. E342. The 4-1BB antigen-binding protein of any one of E319-E338, comprising a VH framework derived from a human germline VH4 framework sequence. E343. The 4-1BB antigen-binding protein of any one of E319-E338, comprising a VH framework derived from a human germline VH2 framework sequence. E344. The 4-1BB antigen-binding protein of any one of E319-E338, comprising a VH framework derived from a human germline VH5 framework sequence. E345. The 4-1BB antigen-binding protein of any one of E319-E344, comprising a VH framework sequence is at least 90% identical to the human germline framework sequence from which it is derived. E346. The 4-1BB antigen-binding protein of any one of E319-E345, comprising a VH framework sequence is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to the human germline framework sequence from which it is derived. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG.1A is a schematic of the steps taken to generate 4-1BB mAbs and PD-L1 mAbs of the present disclosure. FIG.1B is a schematic of the steps taken to generate bispecific molecules comprising a 4-1BB binding protein and PD-L1 binding protein of the present disclosure.

[0013] FIG.2A is an illustration of a bispecific molecule comprising an IgG moiety and a scFv moiety. FIG. 2B is an illustration of a bispecific molecule comprising an IgG moiety and a Fab moiety.

[0014] FIG.3 is a table listing engineered binding proteins and characteristics thereof.

[0015] FIG.4 is a table listing bispecific molecules generated herein and characteristics thereof.

[0016] FIG.5 is a schematic representation of bispecific molecules of interest (dotted lines showing where the IdeS enzyme cleaves), and 2 representative LC-MS spectra of the bispecific molecules. Representative graphs from clones 11259 and 11262 are shown. All IgG-Fabs (11258, 11259, 11262, 11264, and 11265) have been confirmed to have correct HC-LC Pairs.

[0017] FIG.6A is a graph of the IL-2 produced by T-cells activated by artificial APCs plotted as a function of bispecific molecule concentration. FIG.6B is a graph of the IL-2 produced by T-cells activated by artificial APCs plotted as a function of bispecific molecule concentration.

[0018] FIGs.7A-7D are graphs of the tumor volume plotted as a function of time following tumor implant for mice treated with the active agent indicated at the top of each graph.

[0019] FIG.8A is a graph of the tumor volume plotted as a function of time following tumor implant for mice treated with the active agents indicated in the key. FIG.8B is a graph of the percent survival plotted as a function of time following tumor implant for mice treated with the active agents indicated in the key.

[0020] FIG.9 is a table listing characteristics of 4-1BB antigen-binding proteins described herein.

[0021] FIGs.10A-10B are graphs showing crosslinking dependent activity of 4-1BB UniAbs compared to crosslinker independent control.

[0022] FIGs.11A-11D are graphs showing cell binding dose curves for anti-41BB UniAbs using activated T-cells, CHO-human 4-1BB, CHO cyno 4-1BB, off target cell lines compared to a crosslinker independent control.

[0023] FIG.12 a schematic of the steps taken to generate bispecific molecules comprising a 4-1BB binding protein and PD-L1 binding protein of the present disclosure.

[0024] FIGs.13A-13K are illustrations of bispecific molecule format used in second round of screening. Letters “a” and “b” are used to indicate the first antigen (“a”) or the second antigen (“b”) that the bispecific molecule binds to. Letters “N” means that the second antigen-binding moiety is fused at the N-terminus of the first antigen-binding molecule, and the number refers to the number of antigen-binding moieties. N2 = two “b” antigen-binding moieties fused at the N-termini of the “a’ antigen-binding molecule. “B” means the second antigen-binding moiety is fused at the hinge region, and “C” means the second antigen-binding moiety is fused at the C-terminus.

[0025] FIGs.14A-14D provides domain information of certain bispecific formats, including IgG-scFv, Fab- scFv-Fc, IgG-VH, and Fab-VH-Fc.

[0026] FIGs.15A-15B summarizes the biophysical properties of the bispecific molecules disclosed herein.

[0027] FIGs.16A-16C show the potencies of the bispecific molecules disclosed herein.

[0028] FIG.17 shows that the activation of 4-1BB by the bispecific molecule is dependent on the binding of PDL1.

[0029] FIGs.18A-18B show the pre-ADA assessment of the bispecific molecules disclosed herein.

[0030] FIGs.19A-19B shows the immunogenicity assessment of the bispecific molecules disclosed herein.

[0031] FIG.20A shows the overall structure of human 4-1BB and molecule 380984. The crystal structure of human 4-1BB in complex with 380984 is shown as cartoon.4-1BB is in light gray color, and Amgen- 380984 is in dark gray color. The N-, C- terminus, and CDR-3 are labeled. The residues engaged in ligand 4-1BBL binding are marked as sphere. FIG.20B shows the close-up view of the contact between human 4-1BB and 380984. Human 4-1BB (colored in light gray) and Amgen-380984 (colored in dark gray) are illustrated as transparent cartoon. All interacting residues are shown as sticks; the back-bone nitrogen atoms are shown as sphere. Hydrogen bonds are represented as gray dashed lines.

[0032] FIGs 21A-21G are graphs showing the comparison of 4-1BB binders and their potential orientation on cell membrane. The structure of human 4-1BB is shown as surface in color light gray; its binders are shown as cartoon in color dark gray. (A), Three human 4-1BB receptors bind to a trimeric ligand 4-1BBL, each protomer of human 4-1BB are labeled as number 1, 2, 3. PDB: 6mgp. (B). Protomer 2 of the 4-1BB- 4-1BBL complex is shown in the same orientation as in A. (C). The structure of human 4-1BB and Urelumab complex (BMS, PDB:6MHR) is superimposed to the protomer 2 of 4-1BB-4-BBL complex by aligning on the CRDs 3 and 4. The location of Fc is labeled. (D). Protomer 1 of the 4-1BB-4-1BBL complex is shown in the same orientation as in A. (E). The structure of human 4-1BB and 380984 is superimposed to the protomer 1 of 4-1BB-4-BBL complex by aligning the CRDs 3 and 4. The location of Fc is labeled. (F). The structure of human 4-1BB and Utomilumac (Pfizer, PDB: 6MI2) is superimposed to the promotor by aligning the CRDs 3 and 4. The location of Fc are labeled. (G). The structure of Utomilumac and 380984 are superimposed to the same 4-1BB protomer. The sketch models of the full antibody in complex with its binders are shown on the left of each structure. The relative location of cell membrane is also shown at the bottom of each structure. DETAILED DESCRIPTION 1. Overview

[0033] 4-1BB is an immune co-stimulatory protein expressed on activated T cells.4-1BB agonist antibodies have demonstrated efficacy in prophylactic and therapeutic settings in both monotherapy and combination therapy tumor models, and have established protective & durable anti-tumor T-cell memory responses. Agonizing 4-1BB by crosslinking antibody enhances T cell proliferation, survival and cytokine production upon TCR engagement. However, clinical development of 4-1BB agonistic antibodies has been hampered by dose-limiting hepatotoxicity. For example, phase I and II data from Urelumab (BMS- 663513) revealed a liver toxicity that appeared to be on target and dose dependent, halting initial clinical development of Urelumab. The anti-hu4-1BB huIgG2 utomilumab (PF-05082566) displays a better safety profile but lower agonistic potency.

[0034] Seeking to overcome this challenge, the inventors designed bispecific molecules to promote target- mediated clustering of 4-1BB. It is understood that 4-1BB undergoes trimerization upon binding to its ligand (4-1BBL); and 4-1BB multimerization and clustering (“crosslinking”) is a prerequisite for its signaling pathway. Therefore, the 4-1BB antibodies were specifically selected as “crosslinking dependent,” meaning that the agonistic activity of the antibody is dependent upon the crosslinking of 4- 1BB. Without 4-1BB crosslinking, the binding of the antibody to 4-1BB leads to minimal agonist activity, thereby avoiding toxicities exhibited by Urelumab. Urelumab is believed to be a crosslinking independent agonist antibody, meaning the binding of Urelumab to 4-1BB is sufficient to trigger 4-1BB activation. The bispecific molecules disclosed herein take advantage of this crosslinking dependent effect, and the activation of 4-1BB is controlled through a PD-L1 binding moiety, which its expression further limits where the crosslinking events can be happening.

[0035] PD-L1, which is also known as B7-H1 or CD274, is expressed in multiple types of cancers (e.g., breast cancer, lung cancer, melanoma). In the tumor microenvironment, PD-L1, expressed on tumor cells, binds to the inhibitory checkpoint receptor, PD-1, on activated tumor infiltrating lymphocytes. The interaction between PD-L1 and PD-1 delivers an inhibitory signal to T cells and ultimately prevents tumor elimination.

[0036] Presented herein are data demonstrating simultaneous activation of the 4-1BB co-stimulatory pathway and blockade of the PD-L1 / PD-1 inhibitory pathway upon administration of bispecific molecules comprising a 4-1BB binding protein and a PD-L1 binding protein. The data also demonstrate the dual activity upon administration of a combination of a monospecific 4-1BB binding protein and a monospecific PD-L1 binding protein. Without being bound to a particular theory, it is believed that (i) agonizing 4-1BB enhances T-cell proliferation, survival & cytokine production upon TCR engagement; and (ii) simultaneously blocking PD-L1 and agonizing 4-1BB can have synergistic anti-tumor activities.

[0037] In addition, the bispecific molecules described herein address the dose-limiting hepatotoxicity of systemic 4-1BB agonism, because 4-1BB activation is crosslinking dependent. For normal tissues that do not express PD-L1 or express low levels of PD-L1 (such as hepatic cell), minimal crosslinking of 4-1BB will occur, and 4-1BB activation will be limited. In contrast, in cancer cells that express high level of PD- L1, through PD-L1-binding, the bispecific molecules are brought to the proximity of each other, thus promoting 4-1BB crosslinking and T-cell co-stimulation. Systemic toxicities should be limited because 4- 1BB activation will be largely confined to tumors that express high level of PD-L1.

[0038] Accordingly, the present disclosure provides bispecific molecules comprising a 4-1BB binding protein and a PD-L1 binding protein. Related antigen binding proteins, including, for instance, monospecific 4-1BB binding proteins and monospecific PD-L1 binding proteins, are further provided. 2. Antigen Binding Proteins 2.1 Antigen Binding Protein Types

[0039] The antigen-binding proteins of the present disclosure can take any one of many forms of antigen- binding proteins known in the art. In exemplary aspects, the antigen-binding protein is an antibody or immunoglobulin, or an antigen binding fragment of an antibody or immunoglobulin, or an antibody protein product.

[0040] Collectively, antibodies form a family of plasma proteins known as immunoglobulins and comprise of immunoglobulin domains. (Janeway et al., Immunobiology: The Immune System in Health and Disease, 4thed., Elsevier Science Ltd. / Garland Publishing, 1999). As used herein, the term “antibody” refers to a protein having a conventional immunoglobulin format, comprising heavy and light chains, and comprising variable and constant regions. For example, an antibody may be an IgG which is a “Y-shaped” structure of two identical pairs of polypeptide chains, each pair having one “light” (typically having a molecular weight of about 25 kDa) and one “heavy” chain (typically having a molecular weight of about 50-70 kDa). An antibody has a variable region and a constant region. In IgG formats, the variable region is generally about 100-110 or more amino acids, comprises three complementarity determining regions (CDRs), is primarily responsible for antigen recognition, and substantially varies among other antibodies that bind to different antigens. The constant region allows the antibody to recruit cells and molecules of the immune system. The variable region is made of the N-terminal regions of each light chain and heavy chain, while the constant region is made of the C-terminal portions of each of the heavy and light chains. (Janeway et al., “Structure of the Antibody Molecule and the Immunoglobulin Genes”, Immunobiology: The Immune System in Health and Disease, 4thed. Elsevier Science Ltd. / Garland Publishing, (1999)).

[0041] Antibodies can comprise any constant region known in the art. Human light chains are classified as kappa and lambda light chains. Heavy chains are classified as mu, delta, gamma, alpha, or epsilon, and define the antibody's isotype as IgM, IgD, IgG, IgA, and IgE, respectively. IgG has several subclasses, including, but not limited to IgG1, IgG2, IgG3, and IgG4. IgM has subclasses, including, but not limited to, IgM1 and IgM2. Embodiments of the present disclosure include all such classes or isotypes of antibodies. The light chain constant region can be, for example, a kappa- or lambda-type light chain constant region, e.g., a human kappa- or lambda-type light chain constant region. The heavy chain constant region can be, for example, an alpha-, delta-, epsilon-, gamma-, or mu-type heavy chain constant regions, e.g., a human alpha-, delta-, epsilon-, gamma-, or mu-type heavy chain constant region. Accordingly, in exemplary embodiments, the antibody is an antibody of isotype IgA, IgD, IgE, IgG, or IgM, including any one of IgG1, IgG2, IgG3 or IgG4.

[0042] The antibody can be a monoclonal antibody or a polyclonal antibody. In some embodiments, the antibody comprises a sequence that is substantially similar to a naturally-occurring antibody produced by a mammal, e.g., mouse, rabbit, goat, horse, chicken, hamster, human, and the like. In this regard, the antibody can be considered as a mammalian antibody, e.g., a mouse antibody, rabbit antibody, goat antibody, horse antibody, chicken antibody, hamster antibody, human antibody, and the like. In certain aspects, the antibody is a human antibody. In certain aspects, the antibody is a chimeric antibody or a humanized antibody. The term "chimeric antibody" refers to an antibody containing domains from two or more different antibodies. A chimeric antibody can, for example, contain the constant domains from one species and the variable domains from a second, or more generally, can contain stretches of amino acid sequence from at least two species. A chimeric antibody also can contain domains of two or more different antibodies within the same species. The term "humanized" when used in relation to antibodies refers to antibodies having at least CDR regions from a non-human source which are engineered to have a structure and immunological function more similar to true human antibodies than the original source antibodies. For example, humanizing can involve grafting a CDR from a non-human antibody, such as a mouse antibody, into a human antibody. Humanizing also can involve select amino acid substitutions to make a non-human sequence more similar to a human sequence.

[0043] An antibody can be cleaved into fragments by enzymes, such as, e.g., papain and pepsin. Papain cleaves an antibody to produce two Fab fragments and a single Fc fragment. Pepsin cleaves an antibody to produce a F(ab’)2fragment and a pFc’ fragment. In exemplary aspects of the present disclosure, the antigen binding protein of the present disclosure comprises an antigen binding fragment of an antibody. As used herein, “antigen binding fragment” of an antibody refers to a portion of an antibody molecule that retains the ability to specifically bind to an antigen (preferably with substantially the same binding affinity). Examples of an antigen-binding fragment include but not limited to: (i) a Fab fragment, a monovalent fragment consisting of the VL, VH, CL and CH1 domains; (ii) a F(ab')2 fragment, a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region; (iii) a Fd fragment consisting of the VH and CH1 domains; (iv) a Fv fragment consisting of the VL and VH domains of a single arm of an antibody, (v) a dAb fragment (Ward et al., 1989 Nature 341 :544-546), which consists of a VH domain.

[0044] The architecture of antibodies has been exploited to create a growing range of alternative formats that span a molecular-weight range of at least about 12–150 kDa and has a valency (n) range from monomeric (n = 1), to dimeric (n = 2), to trimeric (n = 3), to tetrameric (n = 4), and potentially higher; such alternative formats are referred to herein as “antibody protein products.”

[0045] The building block that is most frequently used to create novel antibody-based formats is the single-chain variable (V)-domain antibody fragment (scFv). Although the two domains of the Fv fragment, VL and VH, are coded for by separate genes, they can be joined, using recombinant methods, by a synthetic linker that enables them to be made as a single protein chain in which the VL and VH regions pair to form monovalent molecules (see e.g., Bird et al. Science 242:423- 426 (1988) and Huston et al., 1988, Proc. Natl. Acad. Sci. USA 85:5879-5883).

[0046] Other forms of single chain antibody protein products, such as diabodies are also encompassed. Diabodies are bivalent, bispecific antibody protein products in which VH and VL domains are expressed on a single polypeptide chain, but using a linker that is too short to allow for pairing between the two domains on the same chain, thereby forcing the domains to pair with complementary domains of another chain and creating two antigen-binding sites (see e.g., Holliger et al, 1993, Proc. Natl. Acad. Sci. USA 90:6444-6448; Poljak et al., 1994, Structure 2:1121 -1123).

[0047] Other antibody protein products include disulfide-bond stabilized scFv (ds-scFv), single chain Fab (scFab), as well as di- and multimeric antibody formats like dia-, tria- and tetra-bodies, or minibodies (miniAbs) that comprise different formats consisting of scFvs linked to oligomerization domains. The smallest fragments are VHH / VH of camelid heavy chain Abs as well as single domain Abs (sdAb). A peptibody or peptide-Fc fusion is yet another antibody protein product. The structure of a peptibody consists of a biologically active peptide grafted onto an Fc domain. Peptibodies are well-described in the art. See, e.g., Shimamoto et al., mAbs 4(5): 586-591 (2012).

[0048] Antigen-binding proteins disclosed herein also include “heavy chain only” molecules. This type of antigen-binding proteins lack the light chain of a conventional antibody. Examples of such “heavy chain only” molecules include, for example, single domain molecules such as UniDabs® (VH only); and homodimeric molecules comprising the VH antigen-binding domain and the CH2 and CH3 constant domains, in the absence of the CH1 domain (e.g., UniAb®). Non-limiting examples of “heavy chain only” antigen binding proteins are described, for example, in WO2018 / 039180. Such heavy chain only molecules can be produced by UniRat®, which is a triple knockout rat wherein the expressions of the native variable coding sequences and the heavy and light chain constant regions have been inactivated. The UniRat has been genetically modified to exclusively express the full human VDJ repertoire (all VH families), with transgenes of human heavy chain variable domains linked to a conserved rat Fc. Immunization of the UniRat elicits a normal antibody response that results in the expression of UniAbs, human heavy-chain-only antibodies of approximately 80 kDa, contrasting with the standard ~150 kDa human IgG. In particular, VH domains from the UniRat, called UniDab, approximately 12.5 kDa (~100 amino acids), can be assembled as modular domains of multispecific antigen binding proteins.

[0049] Bispecific formats can generally be divided into five major classes: BsIgG, appended IgG, BsAb fragments, bispecific fusion proteins and BsAb conjugates. See, e.g., Spiess et al., Molecular Immunology 67(2) Part A: 97-106 (2015).

[0050] In exemplary aspects, the antigen binding protein of the present disclosure comprises any one of these antibody protein products. In exemplary aspects, the antigen binding protein of the present disclosure comprises any one of an scFv, Fab, VHH, VH, Fv fragment, ds-scFv, scFab, UniDab, dimeric antibody, multimeric antibody (e.g., a diabody, triabody, tetrabody), miniAb, peptibody VHH / VH of camelid heavy chain antibody, sdAb, diabody; UniAb; a triabody; a tetrabody; a bispecific or trispecific antibody, BsIgG, appended IgG, BsAb fragment, bispecific fusion protein, and BsAb conjugate.

[0051] In exemplary instances, the antigen binding protein of the present disclosure comprises an antibody protein product in monomeric form, or polymeric, oligomeric, or multimeric form. In certain embodiments in which the antibody comprises two or more distinct antigen binding regions fragments, the antibody is considered bispecific, trispecific, or multi-specific, or bivalent, trivalent, or multivalent, depending on the number of distinct epitopes that are recognized and bound by the antibody.

[0052] Many of the antigen-binding proteins disclosed herein comprise two different chains, one derived from the heavy chain of an antibody, and one derived from the light chain of an antibody. Although the heavy / light chain has been modified and is no longer the classical immunoglobulin heavy / light chain, for convenience, it is still generally called “heavy chain” or “HC” if it is based on heavy chain backbone, and “light chain” or “LC” if it is based on light chain backbone. For example, for tetravalent bispecific molecule IgG-scFv, the “HC” comprises an IgG heavy chain fused to an scFv. It would be apparent to a skilled artisan whether HC is a traditional immunoglobulin heavy chain or a modified version based on immunoglobulin heavy chain backbone. 2.2 Binding Location

[0053] Some exemplary antigen binding proteins disclosed herein are characterized by the location or epitopes they bind to, or by the paratopes that they comprise. An “epitope” refers to the area or region of an antigen to which an antigen binding protein specifically binds, e.g., an area or region comprising residues that interacts with the antigen-binding protein. Epitopes can be linear or conformational. Epitopes can be determined by any method well known in the art. For example, epitopes can be determined by conventional immunoassays. Alternatively, one may competitively screen antigen-binding proteins for binding to the same epitope. An approach to achieve this is to conduct competition and cross- competition studies to find antigen-binding proteins that compete or cross-compete with one another for binding to an antigen (such as 4-1BB).

[0054] The term “paratope” is derived from the above definition of “epitope” by reversing the perspective, and refers to the area or region of an antigen-binding protein which is involved in binding of an antigen, e.g., an area or region comprising residues that interacts with the antigen. A paratope may be linear or conformational (such as discontinuous residues in CDRs).

[0055] The epitope / paratope can be defined and characterized at different levels of detail using a variety of experimental and computational epitope mapping methods. The experimental methods include mutagenesis, X-ray crystallography, Nuclear Magnetic Resonance (NMR) spectroscopy, Hydrogen / deuterium exchange Mass Spectrometry (HX-MS), cryo-EM, and various competition binding methods. As each method relies on a unique principle, the description of an epitope is linked to the method by which it has been determined. Thus, the epitope / paratope for a given binding pair will be defined differently depending on the mapping method employed.

[0056] At its most detailed level, the epitope / paratope for the interaction between the antigen and the antigen-binding protein can be defined by the spatial coordinates defining the atomic contacts present in the interaction, as well as information about their relative contributions to the binding thermodynamics. At one level, an epitope / paratope residue can be characterized by the spatial coordinates defining the atomic contacts between the binding pair. In one aspect, the epitope / paratope residue can be defined by a specific criterion, e.g., distance between atoms in the antigen and the antigen-binding protein (e.g., a distance of equal to or less than 4.5 Å from a heavy atom of the antigen and a heavy atom of the antigen- binding protein ("contact" residues)). In another aspect, an epitope / paratope residue can be characterized as participating in a hydrogen bond interaction with the cognate antibody / antigen, or with a water molecule that is also hydrogen bonded to the antigen / antigen-binding protein (water-mediated hydrogen bonding). In another aspect, an epitope / paratope residue can be characterized as forming a salt bridge with a residue of the cognate antibody / antigen. In yet another aspect, an epitope / paratope residue can be characterized as a residue having a non-zero change in buried surface area (BSA) due to the interaction between the antigen and the antigen-binding protein.

[0057] At a further less detailed level, epitope / paratope can be characterized through function, e.g., by competition binding with other antigen-binding molecules. The epitope / paratope can also be defined more generically as comprising amino acid residues for which substitution by another amino acid will alter the characteristics of the interaction between the binding pair (e.g., alanine scanning).

[0058] In the context of an X-ray derived crystal structure or cryo-EM structure, as exemplified herein with respect to 4-1BB antigen-binding proteins, unless otherwise specified, a 4-1BB epitope residue refers to a 4-1BB residue: (i) having a heavy atom (i.e., a non-hydrogen atom) that is within a distance of 4.5 Å from a heavy atom of the antigen-binding protein (also called “contact” residues); (ii) participating in a hydrogen bond with a residue of the antigen-binding protein, or with a water molecule that is also hydrogen bonded to the antigen-binding protein (water- mediated hydrogen bonding), (iii) participating in a salt bridge to a residue of the antigen-binding protein, and / or (iv) having a non-zero change in buried surface area (BSA) due to interaction with the antigen-binding protein. In general, a cutoff is imposed for BSA to avoid inclusion of residues that have minimal interactions. Therefore, unless otherwise specified, epitope residues under category (iv) are selected if it has a BSA of 20 Å2or greater, or is involved in electrostatic interactions when the antigen-binding protein binds to 4-1BB. Similarly, in the context of an X-ray derived crystal structure or cryo-EM structure, unless otherwise specified or contradicted by context, a paratope residue, refers to an antigen-binding protein residue (i) having a heavy atom (i.e., a non-hydrogen atom) that is within a distance of 4.5 Å from a heavy atom of 4-1BB (also called “contact” residues), (ii) participating in a hydrogen bond with an antigen residue, or with a water molecule that is also hydrogen bonded to 4-1BB (water-mediated hydrogen bonding), (iii) participating in a salt bridge to a residue of 4-1BB, and / or (iv) having a non-zero change in buried surface area due to interaction with 4- 1BB. Again, unless otherwise specified, paratope residues under category (iv) are selected if it has a BSA of 20 Å2or greater, or is involved in electrostatic interactions when the antigen-binding protein binds to 4- 1BB.

[0059] Dependent on the epitope mapping method used, and obtained at different levels of detail, it follows that comparison of epitopes for different antigen-binding protein on the same antigen can similarly be conducted at different levels of detail. For example, epitopes described on the amino acid level, e.g., determined from an X-ray or cryo-EM structure, are said to be identical if they contain the same set of amino acid residues. Epitopes are said to be separate (unique) if no amino acid residue is shared by the epitopes. Epitopes characterized by competition binding are said to be overlapping if the binding of two molecules are mutually exclusive, i.e., binding of one molecule excludes simultaneous or consecutive binding of the other molecule; and epitopes are said to be separate (unique) if the antigen is able to accommodate binding of both molecules simultaneously.

[0060] 4-1BB is a glycosylated type I membrane protein comprises four cysteine-rich pseudo repeats (CRDs) forming the extracellular domain, a short helical transmembrane domain, and a cytoplasmic signaling domain. Human 4-1BB (SEQ ID NO: 272; UniProtKB - Q07011) comprises 255 amino acid residues: residues 1-23 forms signal peptide that is cleaved before mature protein is produced, residues 24 – 186 forms extracellular domain, residues 187 – 213 forms transmembrane helical structure, and residues 214 – 255 forms cytoplasmic domain. The four CRD domains of human 4-1BB are defined as follows: CRD1: residues 24-45; CDR2, residues 47-86; CRD3: residues 87-118, and CRD4: residues 119- 159.

[0061] In certain aspects, the 4-1BB antigen-binding proteins described herein bind to an epitope in CRD1 of 4-1BB. In certain aspects, the 4-1BB antigen-binding proteins described herein bind to an epitope in CRD2 of 4-1BB. In certain aspects, the 4-1BB antigen-binding proteins described herein bind to an epitope in CRD3 of 4-1BB. In certain aspects, the 4-1BB antigen-binding proteins described herein bind to an epitope in CRD4 of 4-1BB.

[0062] In certain aspects, the 4-1BB antigen-binding proteins described herein bind to CRD1 of 4-1BB. In certain aspects, the 4-1BB antigen-binding proteins described herein bind to CRD2 of 4-1BB. In certain aspects, the 4-1BB antigen-binding proteins described herein bind to CRD3 of 4-1BB. In certain aspects, the 4-1BB antigen-binding proteins described herein bind to CRD4 of 4-1BB.

[0063] In particular, as exemplified in Example 14, certain epitope residues within CRD3 were found to be particularly advantageous. Although not wishing to be bound by a particular theory, FIGs.21A-21G illustrate the advantageous of the binding location as exemplified in Example 14. As shown in FIGs.21C, Urelumab binds to CRD1, and is orientated away from cell surface. Because Urelumab does not compete with 4-1BBL for binding, it is believed that simultaneous binding of Urelumab and 4-1BBL may cause synergistic or additive effect, resulting in undesired activation of 4-1BB pathway in normal tissues. This may help explain the observation that Urelumab activates 4-1BB pathway in hepatic cells, resulting in liver toxicity. FIGs.21F and 21G show the binding of Utomilumab to 4-1BB. Utomilumab binds to the CDR4 domain. The antibody is close to cell surface and oriented parallel to the cell surface. This orientation results in a large distance between 4-1BB monomers, making 4-1BB crosslinking more difficult (Fig.21F). That may explain the weak activity of Utomilumab. Molecule 380984, on the other hand, binds to CDR3 and is orientated vertically to the cell surface, which is much more desirable than parallel orientation. Compared with Utomilumab, the distance between 4-1BB monomers is much smaller due to its vertical orientation (Fig.21E).

[0064] The term “bind” here refers to specific binding, a term well understood in the art, and methods to determine such specific binding are also well known in the art. A molecule is said to exhibit “binding” if it reacts or associates more frequently, more rapidly, with greater duration and / or with greater affinity with a particular cell or substance than it does with alternative cells or substances. For example, an antigen- binding protein “binds” to a target if it binds with greater affinity, avidity, more readily, and / or with greater duration than it binds to other substances. For example, a 4-1BB binding protein that binds to the CRD1 domain is a protein that binds this domain with greater affinity, avidity, more readily, and / or with greater duration than it binds to other domains and regions of 4-1BB, or other proteins that are not 4-1BB. It is also understood by reading this definition that, for example, an antigen-binding protein which specifically or preferentially binds to a first target may or may not specifically bind to a second target. As such, “binding,” “specific binding” or “preferential binding” does not necessarily require (although it can include) exclusive binding. If numerical examples are of interest, an antigen-binding protein may bind with a KD value that is numerically less than 1x10-6M, 1x10-7M, 1x10-8M, or 1x10-9M.

[0065] In some embodiments, the present disclosure provides a 4-1BB antigen-binding protein that binds to an epitope that comprises residues C102, V71, and Q104. In certain embodiments, the epitope may further comprise P90. In certain embodiments, the epitope may further comprise one or more residues selected from the group consisting of: K69, T89, F92, M101, and L112. These epitope residues are numbered according to the numbering of SEQ ID NO:272 (human 4-1BB). Corresponding residues from other 4-1BB homologs, isoforms, variants, or fragments can be identified according to sequence alignment or structural alignment that is known in the art. For example, alignments can be done by hand or by using well-known sequence alignment programs such as ClustalW2, or "BLAST 2 Sequences" using default parameters. As exemplified by the structural data, C102, V71, and Q104 were found to be “primary” residues for molecule 380984 binding; P90 was found to be “contributing” residues for scFv32211 binding; and K69, T89, F92, M101, and L112, while involved in H-bonding and Van Der Waals interactions with 380984, were found to be “optional” residue for 380984 binding.

[0066] Based on the structural studies, one or more of the following substitutions would likely substantially disrupt the binding of 380984 binding to 4-1BB: (i) C102 is replaced with A; (ii) A104 is replaced with A; or(iii) K69 is replaced with A. An Alanine-scan shows that none of the epitope residues potentially abrogate the VH binding because the hydrogen bonds are mostly thought backbone. The C102 is highly conserved disulfide within 4-1BB CRD3 domain, maintaining its structural stability, which mutation would potentially break the fold and also affect the VH binding. 2.3 Structure of 4-1BB Antigen Binding Proteins

[0067] As used herein, “Complementarity Determining Regions” (CDRs) can be identified according to the definitions of the Kabat, Chothia, the accumulation of both Kabat and Chothia, AbM, contact, North, and / or conformational definitions or any method of CDR determination well known in the art. See, e.g., Kabat et al., 1991, Sequences of Proteins of Immunological Interest, 5th ed. (hypervariable regions); Chothia & Lesk, 1987, J Mol Biol., 196:901-917 (structural loop structures). The identity of the amino acid residues in a particular antibody that make up a CDR can be determined using methods well known in the art. AbM definition of CDRs is a compromise between Kabat and Chothia and uses Oxford Molecular’s AbM antibody modeling software (Accelrys®). The “contact” definition of CDRs is based on observed antigen contacts, set forth in MacCallum et al., 1996, J. Mol. Biol., 262:732-745. The “conformational” definition of CDRs is based on residues that make enthalpic contributions to antigen binding (see, e.g., Makabe et al., 2008, J. Biol. Chem., 283:1156-1166). North has identified canonical CDR conformations using a different preferred set of CDR definitions (North et al., 2011, J. Mol. Biol.406: 228-256). In another approach, referred to herein as the “conformational definition” of CDRs, the positions of the CDRs may be identified as the residues that make enthalpic contributions to antigen binding (Makabe et al., 2008, J Biol. Chem.283:1156-1166). Martin definition (also called enhanced Chothia definition) combines the Kabat and Chothia definitions and differs from them only in the heavy chain, where CDR- H1 includes all residues of Kabat and Chothia while CDR-H2 is seven residues shorter than that defined by Kabat (Martin, Bioinformatics tools for antibody engineering. Handbook of Therapeutic Antibodies. Weinheim: Wiley-VCH Verlag GmbH; (2008). p.95–117; see also the database maintained by the Institute of Structural and Molecular Biology at the University College London, http: / / www.bioinf.org.uk / abs / #cdrid). Still other CDR boundary definitions may not strictly follow one of the above approaches, but will nonetheless overlap with at least a portion of the Kabat CDRs, although they may be shortened or lengthened in light of prediction or experimental findings that particular residues or groups of residues or even entire CDRs do not significantly impact antigen binding. For example, “combined” CDRs may also be used. Therefore, a CDR may refer to CDRs defined by any approach known in the art, including combinations of approaches. For any given embodiment containing more than one CDR, the CDRs (or other residue of the antibody) may be defined in accordance with any of Kabat, Chothia, North, AbM, Contact, IMGT, Martin, combined Kabat and Chothia, and / or conformational definitions.

[0068] For example, Table N1 shows several commonly used definitions of CDRs: Table N1. Definitions of CDRs. Loop Kabat AbM Chothia1Contact2IMGT L1 L24-L34 L24-L34 L26-L32 L30-L36 L27-L32 7; C - : 6-3 ; C - : 5 -56; C - 3: 95- 0 . abe s a consensus o C ot a de nton based upon Chothia & Lesk (1987) (e.g., CDR-H3) and Chothia et al., 1989, Nature 342:877-883 (e.g., CDR-H2). 2. Any of the numbering schemes can be used for these CDR definitions, except the contact definition uses the Chothia or Martin (Enhanced Chothia) definition. 3. The end of the Chothia CDR-H1 loop when numbered using the Kabat numbering convention varies between H32 and H34 depending on the length of the loop. (This is because the Kabat numbering scheme places the insertions at H35A and H35B.)

[0069] The CDR sequences provided in the Sequence Tables are based on the Kabat definition. However, other definitions for CDRs may also be used. Accordingly, in some embodiments, the 4-1BB antigen- binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO:147, 149, 151, 153, 155, 157, 159, 324, 161, 163, 165, 167, 169, 171, 173, 175, 404, 406, 408, or 410; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 148, 150, 152, 154, 156, 158, 160, 325, 162, 164, 166, 168, 170, 172, 174, 176, 405, 407, 409, or 411. In some embodiments, the three heavy chain CDRs and three light chain CDRs come from the same clone as shown in Sequence Table B and Table K1. In exemplary embodiments, the CDRs are defined according to Kabat, Chothia, AbM, contact, or IMGT.

[0070] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:147; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:148. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0071] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:149; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:150. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0072] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:151; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:152. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0073] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:153; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:154. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0074] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:155; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:156. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0075] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:157; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:158. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0076] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:159 or 324; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:160 or 325. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0077] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:161; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:162. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0078] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:163; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:164. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0079] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:165; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:166. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0080] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:167; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:168. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0081] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:169; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:170. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0082] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:171; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:172. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0083] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:173; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:174. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0084] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:175; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:176. The antigen binding protein may further bind to its target 4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0085] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:404; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:405. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0086] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:406; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:407. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0087] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:408; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:409. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0088] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:410; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:411. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0089] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 147, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 148.

[0090] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 149, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 150.

[0091] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 151, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 152.

[0092] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 153, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 154.

[0093] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 155, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 156.

[0094] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 157, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 158.

[0095] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 159 or 324, and (ii) the light chain CDR-L1, CDR- L2, and CDR-L3 of SEQ ID NO: 160 or 325.

[0096] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 161, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 162.

[0097] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 163, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 164.

[0098] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 165, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 166.

[0099] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 167, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 168.

[0100] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 169, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 170.

[0101] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 171, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 172.

[0102] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 173, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 174.

[0103] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 175, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 176.

[0104] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 404, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 405.

[0105] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 406, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 407.

[0106] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 408, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 409.

[0107] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 410, and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 411.

[0108] In exemplary aspects, the 4-1BB antigen binding proteins comprise (a) CDR-H1 amino acid sequence set forth in Sequence Table B and Table K1, or a variant sequence thereof which differs by only 1-4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set for in Table B or Table K1; (b) CDR-H2 amino acid sequence set forth in Sequence Table B and Table K1, or a variant sequence thereof which differs by only 1-4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set forth in Table B or Table K1; (c) a CDR-H3 amino acid sequence set forth in Sequence Table B and Table K1, or a variant sequence thereof which differs by only 1-4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set forth in Table B or Table K1; (d) a CDR-L1 amino acid sequence set forth in Sequence Table B and Table K1, or a variant sequence thereof which differs by only 1-4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set forth in Table B or Table K1; (e) a CDR-L2 amino acid sequence set forth in Sequence Table B and Table K1, or a variant sequence thereof which differs by only 1-4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set forth in Table B or Table K1; (f) a CDR-L3 amino acid sequence set forth in Sequence Table B and Table K1, or a variant sequence thereof which differs by only 1-4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set forth in Table B or Table K1; or (g) a combination of any two, three, four, five, or six of (a)-(f). The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0109] In exemplary embodiments, the 4-1BB antigen binding protein comprises 3, 4, 5, or all 6 of the amino acid sequences designated by the SEQ ID NOs under the same clone name in Sequence Table B and Table K1. In exemplary embodiments, the antigen binding protein comprises each of the LC CDR amino acid sequences designated by the SEQ ID NOs under the same clone name in Sequence Table B and Table K1 and at least 1 or 2 of the HC CDR amino acid sequences designated by the SEQ ID NOs in under the same clone name of Sequence Table B and Table K1. In exemplary embodiments, the antigen binding protein comprises each of the HC CDR amino acid sequences designated by the SEQ ID NOs under the same clone name in Sequence Table B and Table K1 and at least 1 or 2 of the LC CDR amino acid sequences designated by the SEQ ID NOs under the same clone name in Sequence Table B and Table K1. In exemplary embodiments, the antigen binding protein comprises six CDR amino acid sequences listed under the same clone name in Sequence Tables or comprising six CDR amino acid sequences selected from the group consisting of: (1) SEQ ID NOs: 43-48, (2) SEQ ID NOs: 49-54, (3) SEQ ID NOs: 55-60, (4) SEQ ID NOs: 61-66, (5) SEQ ID NOs: 67-72, (6) SEQ ID NOs: 73-78, (7) SEQ ID NOs: 79-84, (8) SEQ ID NOs: 85-90, (9) SEQ ID NOs: 91-96, (10) SEQ ID NOs: 97-102, (11) SEQ ID NOs: 103-108, (12) SEQ ID NOs: 109-114, (13) SEQ ID NOs: 115-120, (14) SEQ ID NOs: 121-126, (15) SEQ ID NOs: 127-132, (16) SEQ ID NOs: 386-391, (17) SEQ ID NOs.: 392-397.

[0110] The CDR sequences of the exemplary 4-1BB antigen-binding proteins disclosed herein can be aligned to identify consensus sequences. In one alignment, the CDR sequences are aligned according to Kabat numbering (i.e., residues with the same Kabat numbering are aligned), and the results are shown in Tables N2 & N3. Table N2. Light chain CDR alignment based on Kabat numbering (SEQ ID numbers of these CDR sequences can be found in Table B) Clone name CDR-L1 CDR-L2 CDR-L3 7 NN I KNVH DDDRP VWD DHVV 14A5 RASQ-----SIKRYLN AASSLQS QQRFSIP--FT 19G1 SGDK-----LGDNYAC QDSRRPS QTWDSSA--VM 15A12.012 RASQ-----SISTYLN AASSLQS LQTYSA---LT (SEQ ID numbers of these sequences can be found in Table B) Clone name CDR-H1 CDR-H2 CDR-H3 6C7 RYYWS YID-DSGNTNYNPSLKS GVAAGR----------IDP

[0111] For Kabat CDR-H2, additional residues are assigned between H52 and H53 (e.g., H52A, H52B, H52C), those positions are represented by a gap if a particular CDR-H2 does not have a corresponding residue. Similarly, gaps are used to align Kabat CDR-H3, between H100 and H101 (H100A-H100K according to Kabat numbering), Kabat CDR-L1 between L27 and L28 (L27A-L27F according to Kabat numbering), and Kabat CDR-L3 between L95 and L96 (L95A-L95F according to Kabat numbering). Table N4 summarizes the consensus sequences derived from this method. Table N4. Consensus Sequences of CDRs Seq No.Name Sequence 4-1 BB CDR- X1 I X2 X3 X4 X5 X6 X7 X8 Y X9 X10 X11 X12 X13 X14 K X15 H2 X1 = Y, R, A, V, or L X2 = D, Y, S, W, or G 17 X4 = D, Q, S, R, K, N, V, or T X5 = R, or L X6 = P, Q, or F

[0112] Alternatively, the CDR sequences can be aligned according to the germline sequences those clones are derived from. Table N5-N7 summarize such alignment. Germline sequences are in bold. Table N5. Heavy chain germline alignment (SEQ ID numbers of these sequences can be found in Table B and Table M1) H_CDR1 H_CDR2 H_CDR3 VH3|3-33 / D3|3-3|RF3 / JH4SYGMH VIWYDGSNKYYADSVKG ITIFGVV IIYFDYYVVVVVVVVHFVVVVVV VH4|4-59 / D6|6-13|RF2 / JH5SYYWS YIYY-SGSTNYNPSLKS GIAAAG--------NWFDP6C7RYYWS YIDD-SGNTNYNPSLKS GVAAG----------RIDPPVVPP (SEQ ID numbers of these sequences can be found in Table B and Table M2) K_CDR1 K_CDR2 K_CDR3 VK2|A2 / JK1KSSQSLLHSDGKTYLY EVSNRFS MQSIQLPWT . (SEQ ID numbers of these sequences can be found in Table B and Table M3) L_CDR1 L_CDR2 L_CDR3 19G1 SGD--KLGDNYAC QDSRRPS QTWDS--SAVM 19G1.016 SGD--KLGDNYAS QDSRRPS QTWDS--SAVM , le N8. Table N8. Consensus CDR sequences based on germline alignment X1 Y X2 X3 X4 4-1 BB CDR- X1 = S, T, N, or G 484 H1 (VH3 X2 = A S or G 17 X1 X2 X3 X4 G X5 X6 X7 Y Y Y G M D V X1 = G or S 1 BB CDR X2 = Y or G X4 = Y, N, or F X5 = S or absent X6 = T, S, V, or I

[0114] Also provided herein are VH-only 4-1BB antigen-binding proteins, in particular, UniDabs that are derived from UniRat technology.

[0115] For example, exemplified herein are 4-1BB antigen-binding protein that comprises a heavy chain variable domain (VH) and does not comprise a light chain variable domain (VL), wherein said protein comprises the CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, or 385. As explained in detail above, CDRs can be identified according to the definitions of the Kabat, Chothia, the accumulation of both Kabat and Chothia, AbM, contact, North, and / or conformational definitions or any method of CDR determination well known in the art. The CDR sequences shown in Table I are defined according to Kabat. However, other definitions for CDRs may also be used.

[0116] In some embodiments, the present disclosure provides a 4-1BB antigen binding protein comprising a heavy chain variable domain (VH) but does not comprise a light chain variable domain (VL), wherein said 4-1BB antigen binding protein comprises the following paratope residues (VH numbering according to Kabat): (1) H45 is Leu, Phe, Ile, or Tyr; (2) H47 is Trp, Phe, Leu, or Tyr; (3) H100B is Tyr, Arg, His, Lys, or Met; (4) H100D is Thr, Ala, Asn, Cys, Gln, Lys, Met, or Val; and (5) H100F is Phe, Trp or Tyr. Based on structural studies, these paratope residues were found to be “primary” residues from clone 380984 that bind to 4-1BB. Preferably, (1) H45 is Leu or Phe; (2) H47 is Trp or Leu; (3) H100B is Tyr or Met; (4) H100D is Thr or Val; and (5) H100F is Phe or Trp. More preferably, (1) H45 is Leu; (2) H47 is Trp; (3) H100B is Tyr; (4) H100D is Thr; and (5) H100F is Phe.

[0117] The 4-1BB antigen binding protein may further comprise the following paratope residues: (VH according to Kabat): (6) H97 is Ser, Arg, Asn, Gln, Glu, His,,Leu, Lys, Met, Phe, Thr, Trp, Tyr, or Val; (7) H100E is Ser, Ala, Asn, Asp, Cys, His, Trp, Tyr, or Val; and (9) H102 is Tyr, Ile, Lys, or Val. Based on structural studies, these paratope residues were found to be “optional” residues from clone 380984that bind to 4-1BB. Preferably, ((6) H97 is Ser or Leu; (7) H100E is Ser or Val; and (9) H102 is Tyr or Lys. More preferably, (6) H97 is Ser; (7) H100E is Ser; and (9) H102 is Tyr.

[0118] Based on structural studies, it was discovered that, for 380984, among the three complementarity determining regions (CDRs), CDR-H3 is responsible for contacting FAP residues. In addition, Leu45 and Trp47 are characterize as framework residues under Kabat, AbM, Chothia, and IMGT definitions. Contact definition characterizes Trp47 as part of CDR-H2. Accordingly, in certain embodiments, the 4-1BB antigen-binding protein comprises (a) a VH that comprises: (i) a CDR-H3 comprising any one of SEQ ID NOs:576-578 and 580; and (ii) framework residue H45 is Leu and framework residue H47 is Trp; or (b) a VH that comprises: (i) a CDR-H2 comprising SEQ ID NO:574, (ii) a CDR-H3 comprising SEQ ID NO: 579; and (iii) framework residue H45 is Leu. In certain embodiments, said framework residues, CDR-H2, or CDR-H3 contact 4-1BB residues C102, V71, Q104, P90, K69, T89, F92, M101, or L112, according to the numbering of SEQ ID NO:272.

[0119] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:371. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0120] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:372. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0121] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:373. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0122] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:374. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0123] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:375. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0124] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:376. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0125] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:377. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0126] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:378. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0127] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:379. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0128] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:380. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0129] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:381. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0130] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:382. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0131] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:383. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0132] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:384. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0133] In various embodiments, the 4-1BB antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:385. The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0134] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 371.

[0135] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 372.

[0136] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 373.

[0137] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 374.

[0138] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 375.

[0139] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 376.

[0140] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 377.

[0141] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 378.

[0142] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 379.

[0143] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 380.

[0144] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 381.

[0145] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 382.

[0146] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 383.

[0147] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 384.

[0148] In some embodiments, the 4-1BB antigen-binding protein disclosed herein comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 385.

[0149] In exemplary aspects, the 4-1BB antigen binding proteins comprise (a) CDR-H1 amino acid sequence set forth in Sequence Table I, or a variant sequence thereof which differs by only 1-4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set forth in Sequence Table I; (b) CDR-H2 amino acid sequence set forth in Sequence Table I, or a variant sequence thereof which differs by only 1- 4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set forth in Sequence Table I; (c) a CDR-H3 amino acid sequence set forth in Sequence Table I, or a variant sequence thereof which differs by only 1-4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set forth in Sequence Table I; or (d) a combination of any two, or three (a)-(c). The antigen binding protein may further bind to its target (4-1BB) with a KD value of 100 nM or less, or a KD value of 500 nM or less.

[0150] In exemplary embodiments, the 4-1BB antigen binding protein comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising: (1) SEQ ID NOs: 326-328, respectively (2) SEQ ID NOs: 329-331, respectively, (3) SEQ ID NOs: 332-334, respectively, (4) SEQ ID NOs: 335-337, respectively, (5) SEQ ID NOs: 338-340, respectively, (6) SEQ ID NOs: 341-343, respectively, (7) SEQ ID NOs: 344-346, respectively, (8) SEQ ID NOs: 347-349, respectively, (9) SEQ ID NOs: 350-352, respectively, (10) SEQ ID NOs: 353-355, respectively, (11) SEQ ID NOs: 356-358, respectively, (12) SEQ ID NOs: 359-361, respectively, (13) SEQ ID NOs: 362-364, respectively, (14) SEQ ID NOs: 365-367, respectively, or (15) SEQ ID NOs: 368-370, respectively.

[0151] The CDR sequences of these VH-only 4-1BB antigen-binding proteins can be aligned to identify consensus sequences. In one alignment, the CDR sequences are aligned according to Kabat numbering (i.e., residues with the same Kabat numbering are aligned), and the results are shown in Table N9. Gaps represent absent residues in Kabat CDR-H2, between H52 and H53 (H52A-H52C), and in Kabat CDR- H3, between H100 and H101 (H100A-H100K). Table N10 summarizes the consensus sequences derived from this method. Table N9. UniDab CDR alignment based on Kabat numbering clone CDR1 CDR2 CDR3 386340 VH SFAMT AISG--SGGSTYYAGSVKG EAYESS-GYYTTSFDY Y Y Y Y Y Y Y I I I Y I I Y Table N10. UniDab CDR consensus sequences Seq No.Name SequenceX1 X2 X3 M X4 16

[0152] In general, CDRs are separated by “framework” (FR) residues. A VH or VL domain framework comprises four framework sub-regions, FR1, FR2, FR3 and FR4, interspersed with CDRs in the following structure: FR1 - CDR1 - FR2 - CDR2 - FR3 - CDR3 - FR4. Accordingly, the antigen binding proteins described herein may comprise a VH framework, such as a human germline VH framework sequence, and a VL framework, such as human germline VL framework sequences.

[0153] Preferred human germline light chain frameworks are frameworks derived from Vκ or Vλ germlines. It will be understood that if a sequence is “derived from” one or more germlines, what is referred to is a structural relationship, in which the features of a sequence correspond to the noted germline sequences, but may comprise somatic mutations or other amino acid differences relative to the noted germline sequence. For a sequence to be “derived from” a germline, an actual process of deriving that sequence from a germline sequence (either via molecular biology or computational analysis) is not necessarily required. For example, VL frameworks may be derived from one of the framework of the following germlines: DPK9 (IMGT name: IGKV1-39), DPK12 (IMGT name: IGKV2D-29), DPK18 (IMGT name: IGKV2-30), DPK24 (IMGT name: IGKV4-1), HK102_V1 (IMGT name: IGKV1-5), DPK1 (IMGT name: IGKV1-33), DPK8 (IMGT name: IGKV1-9), DPK3 (IMGT name: IGKV1-6), DPK21 (IMGT name: IGKV3- 15), Vg_38K (IMGT name: IGKV3-11 ), DPK22 (IMGT name: IGKV3-20), DPK15 (IMGT name: IGKV2- 28), DPL16 (IMGT name: IGLV3-19), DPL8 (IMGT name: IGLV1-40), V1-22 (IMGT name: IGLV6-57). Alternatively, or in addition, the framework sequence may be derived from a human germline consensus framework sequence, such as the framework of human Vλ1 consensus sequence, Vλ3 consensus sequence, Vκ1 consensus sequence, Vκ2 consensus sequence, Vκ3 consensus sequence. Sequences of human germline frameworks are available from various public databases, such as V-base, IMGT, NCBI, or Abysis.

[0154] The 4-1BB antigen binding proteins described herein may comprise a VL framework, wherein the framework may comprise one or more amino acid substitutions, additions, or deletions, while still retaining functional and structural similarity with the germline from which it was derived. In some aspects, the VL framework is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to a human germline VL framework sequence. In some aspects, the antigen binding protein, antibody, or antigen binding fragment thereof, comprises a VL framework comprising 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 amino acid substitutions, additions or deletions relative to the human germline VL framework sequence.

[0155] The VH framework sequence can be derived from a human VH3 germline, a VH1 germline, a VH5 germline, a human VH2 germline, or a VH4 germline. Preferred human germline heavy chain frameworks are frameworks derived from VH1, VH2, VH3, or VH4 germlines. For example, VH frameworks may be derived from the framework of one of the following germlines: DP54 or IGHV3-7, DP47 or IGHV3-23, DP71 or IGHV4-59, DP75 or IGHV1-2_02, DP10 or IGHV1-69, DP7 or IGHV1-46, DP49 or IGHV3-30, DP51 or IGHV3-48, DP38 or IGHV3-15, DP79 or IGHV4-39, DP78 or IGHV4-30-4, DP73 or IGHV5-51, DP50 or IGHV3-33, DP46 or IGHV3-30-3, DP31 or IGHV3-9. Alternatively, or in addition, the framework sequence may be derived from the framework of a consensus sequence, such as: VH3 germline consensus sequence, VH1 germline consensus sequence, VH5 germline consensus sequence, VH2 germline consensus sequence, or VH4 germline consensus sequence.

[0156] The antigen binding proteins described herein may comprise a VH framework, wherein the framework may comprise one or more amino acid substitutions, additions, or deletions, while still retaining functional and structural similarity with the germline from which it was derived. In some aspects, the VH framework is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to a human germline VH framework sequence. In some aspects, the antigen binding protein, antibody, or antigen binding fragment thereof, comprises a VH framework comprising 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 amino acid substitutions, additions or deletions relative to the human germline VH framework sequence.

[0157] In exemplary embodiments, the 4-1BB antigen-binding protein comprises a VH that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 147, 149, 151, 153, 155, 157, 159, 324, 161, 163, 165, 167, 169, 171, 173, 175, 404, 406, 408, or 410. In exemplary embodiments, the 4-1BB antigen-binding protein comprises a VL that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 148, 150, 152, 154, 156, 158, 160, 325, 162, 164, 166, 168, 170, 172, 174, 176, 405, 407, 409, or 411. Preferably, the 4-1BB antigen binding protein comprises a pair of VH and VL sequences listed under the same clone name in Table B and Table K1.

[0158] In exemplary embodiments, the 4-1BB antigen-binding protein comprises a VH but does not comprise a VL, wherein said VH comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, or 385.

[0159] In some embodiments, the 4-1BB antigen binding protein comprises a CH1 domain, preferably a human CH1 domain (such as a human IgG1 CH1, a human IgG2 CH1, a human IgG3 CH1, or a human IgG4 CH1). Non-limiting examples of human CH1 sequences are provided in the Sequence Tables. In some embodiments, the CH1 domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 242, 259, 261, 265, 269, 422, or 425.

[0160] In certain embodiments, the 4-1BB antigen binding proteins described herein comprises an Fc domain. The Fc domain can be derived from IgA (e.g., IgA1 or lgA2), IgG, IgE, or IgG (e.g., IgG1, lgG2, lgG3, or lgG4). In some embodiments, the Fc domain comprises wild type sequence of a human Fc domain. Non-limiting examples of human Fc domain sequences are provided in the Sequence Table.

[0161] In some embodiments, the Fc domain comprises one or more mutations resulting in altered biological activity, such as to improve half-life / stability or to render the antibody more suitable for expression / manufacturability. For example, mutations may be introduced into the Fc domain to reduce the effector activity (e.g., WO 2005 / 063815), and / or to increase the homogeneity during the production of the recombinant protein.

[0162] In general, amino acid residues in the IgG heavy constant domain of an antibody are numbered according the EU index of Edelman et al., 1969, Proc. Natl. Acad. Sci. USA 63(1):78-85 as described in Kabat et al., 1991, referred to herein as the “EU index numbering.” Typically, the constant domain comprises from residue 118 to 447, and the Fc domain comprises from residue 236 to 447 of the human lgG1 constant domain. Comparison between EU numbering and other numbering systems can be found, e.g., at IGMT database.

[0163] Amino acid residues of the light chain constant domain are numbered according to Kabat et al., 1991, "Sequences of Proteins of Immunological Interest 5th Ed.", 1991, NATIONAL INSTITUTES OF HEALTH. Kappa light chain also has EU index numbering, and the EU index and Kabat numbering are identical. Lambda light chain does not have EU index numbering.

[0164] In some embodiments, the Fc domain is the Fc domain of human lgG1 and comprises one or more of the following effector-null mutations: L234A, L235A, and G237A (numbering according to the EU index), often referred as “LALA” mutations.

[0165] It has been reported that a single mutation of L235E was sufficient for knocking out binding to Fc receptors on U937 cells. Furthermore, the 100-fold reduction in binding to FcγR also resulted in lower T cell activation and proliferation in the presence of the L235E Fc mutant IgG1. Building upon this initial mutation it was found that the combination of L234A and L235A (commonly called LALA mutations) eliminated FcγRIIa binding. These two mutations were later shown to eliminate detectable binding to FcγRI, IIa, and IIIa for both IgG1 and IgG4. Other sites have been reported to knockout Fc receptor binding, such as Gly237Ala, Glu318Ala, Asp265Ala and Glu233Pro mutations.

[0166] In exemplary embodiments, the Fc region comprises a Stable Effector Functionless (SEFL) mutation to inhibit or reduce the ability to interact with Fcγ receptors, sequence. SEFL mutations are known in the art. See, e.g., Liu et al., J Biol Chem 292: 1876-1883 (2016); and Jacobsen et al., J. Biol. Chem.292: 1865-1875 (2017), and Estes et al., iScience, Volume 24, Issue 12, 2021,103447. Further, US US9546203 discloses a Fc region comprising a N297G mutation, and one or more substitutions at position V259, A287, R292, V302, L306, V323, or I332, using EU numbering scheme, with a cysteine amino acid residue. In exemplary aspects, the SEFL mutation comprises one or more of the following mutations, numbered according to the EU system: L242C, A287C, R292C, N297G, V302C, L306C, and / or K334C. In exemplary aspects, the SEFL mutation comprises N297G. In exemplary aspects, the SEFL mutation comprises A287C, N297G, and L306C. In other exemplary aspects, the SEFL mutation comprises R292C, N297G, and V302C (i.e., SEFL2-2).

[0167] In exemplary embodiments, the Fc region comprises a YTE mutation. The M252Y / S254T / T256E (EU index numbering, referred to “YTE”) triple mutation have been shown to increase IgG half-life in cynomolgus monkeys by an approximate 4-fold increase.

[0168] C-terminal lysine clipping is a common phenomenon occurring during the bioproduction of monoclonal antibodies. Often, the lysine residue is removed via carboxypeptidase D (CpD), which results in generation of a mixture of antibody isoforms bearing zero or one C-terminal lysine residues on each heavy chain. Further, following C-terminal lysine cleavage, peptidylglycine α-amidating monooxygenase (PAM) catalyzes the hydroxylation of glycine and removal of the glyoxylate from the glycine residue, leaving an amidated C-terminal proline. Therefore, during recombinant production of a monoclonal antibody, the product is often a mixture of C-terminal processing variants, with heavy chain C-terminus ends at (amidated) proline, glycine, or lysine. Sometimes, it may be desirable to delete the C-terminal lysine of the Fc domain to increase the homogeneity during the production of the recombinant protein.

[0169] In some embodiments, the terminal lysine may be absent; in some embodiments, the terminal lysine may be present; in some embodiments, the terminal glycine-lysine may be absent; in some embodiments, the terminal glycine-lysine may be present. It will be appreciated that in some embodiments, a pharmaceutically suitable composition may comprise a mixture of species that do and do not comprise the terminal lysine and / or glycine-lysine.

[0170] In exemplary embodiments, the 4-1BB antigen binding proteins described herein comprise Fc that is derived from an IgG1. In some embodiments, the Fc comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 243, 250, 251, 252, 253, 254, 255, 413, 423, 426, 263, 267, or 483.

[0171] In exemplary embodiments, the 4-1BB antigen binding proteins described herein comprise an IgG1 heavy chain constant domain. In some embodiments, the heavy chain constant domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 244, 245, 246, 247, 248, 249, 256, 257, 258, 260, 412, 415, 417, 418, 427, 264, 268, or 271.

[0172] In some embodiments, the 4-1BB antigen-binding protein described herein comprising a kappa or lambda light chain constant domain. In some embodiments, the kappa light chain constant domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 236, 237, 240, 414, 416, 419, 420, 421, or 428. In some embodiments, the lambda light chain constant domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 238, 239, 241, or 424.

[0173] The 4-1BB antigen-binding protein may be a full-length immunoglobulin, a Fab, or an scFv. Exemplary full length 4-1BB binding immunoglobulins are shown as Sequence Table F. Exemplary Fab and scFV domains are shown in Sequence Table H and Table K6. The scFv may comprises a linker between VH and VL. Exemplary linker sequences, such as GS-based linkers, are provided in the Sequence Table G.

[0174] In some embodiments, the scFv described herein comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 291.

[0175] In some embodiments, the scFv described herein comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 445 (14A5.002 scFv #2).

[0176] In some embodiments, the Fab described herein comprises a Fab heavy chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 298, and a Fab light chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 300 (6F9.009 Fab).

[0177] In some embodiments, the Fab described herein comprises a Fab heavy chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 305, and a Fab light chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 307 (19G1.016 Fab).

[0178] In some embodiments, the Fab described herein comprises a Fab heavy chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 316, and a Fab light chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 317 (6C7.018 Fab).

[0179] In some embodiments, the Fab described herein comprises a Fab heavy chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to residues 1-227 of SEQ ID NO: 434, and a Fab light chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 435 (4-1BB Fab of 56039).

[0180] In some embodiments, the Fab described herein comprises a Fab heavy chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to residues 1-227 of SEQ ID NO: 449, and a Fab light chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 450 (4-1BB Fab of 56040). 2.4 Structure of PD-L1 Antigen Binding Proteins

[0181] Also provided herein are PD-L1 antigen-binding proteins. Examples of PD-L1 antigen-binding proteins are provided in the Sequence Tables. As discussed in detail above, the CDR sequences provided in the Sequence Tables are based on the Kabat definition. However, other definitions for CDRs may also be used. Accordingly, in some embodiments, the PD-L1 antigen-binding protein disclosed herein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 133, 135, 137, 139, 141, 143, 322, 145, 398, 400, or 402; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 134, 136, 138, 140, 142, 144, 323, 146, 399, 401, or 403. In some embodiments, the three heavy chain CDRs and three light chain CDRs come from the same clone as shown in Sequence Table C. In exemplary embodiments, the CDRs are defined according to Kabat, Chothia, AbM, contact, or IMGT

[0182] In various embodiments, the PD-L1 antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:133; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:134. The antigen binding protein may further bind to its target (PD-L1) with a KD value of 100 nM or less, or a KD value of 50 nM or less.

[0183] In various embodiments, the PD-L1 antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:135; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:136. The antigen binding protein may further bind to its target (PD-L1) with a KD value of 100 nM or less, or a KD value of 50 nM or less.

[0184] In various embodiments, the PD-L1 antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:137; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:138. The antigen binding protein may further bind to its target (PD-L1) with a KD value of 100 nM or less, or a KD value of 50 nM or less.

[0185] In various embodiments, the PD-L1 antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:139; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:140. The antigen binding protein may further bind to its target (PD-L1) with a KD value of 100 nM or less, or a KD value of 50 nM or less.

[0186] In various embodiments, the PD-L1 antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:141; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:142. The antigen binding protein may further bind to its target (PD-L1) with a KD value of 100 nM or less, or a KD value of 50 nM or less.

[0187] In various embodiments, the PD-L1 antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:143; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:144. The antigen binding protein may further bind to its target (PD-L1) with a KD value of 100 nM or less, or a KD value of 50 nM or less.

[0188] In various embodiments, the PD-L1 antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:322; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:323. The antigen binding protein may further bind to its target (PD-L1) with a KD value of 100 nM or less, or a KD value of 50 nM or less.

[0189] In various embodiments, the PD-L1 antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:145; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:146. The antigen binding protein may further bind to its target (PD-L1) with a KD value of 100 nM or less, or a KD value of 50 nM or less.

[0190] In various embodiments, the PD-L1 antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:398; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:399. The antigen binding protein may further bind to its target (PD-L1) with a KD value of 100 nM or less, or a KD value of 50 nM or less.

[0191] In various embodiments, the PD-L1 antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:400; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO: 401. The antigen binding protein may further bind to its target (PD-L1) with a KD value of 100 nM or less, or a KD value of 50 nM or less.

[0192] In various embodiments, the PD-L1 antigen binding protein comprises a VH comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% identical to the three heavy chain CDRs in SEQ ID NO:402; and a VL comprising three CDRs that in combination are at least 85%, at least 90%, or at least 95% to the three light chain CDRs in SEQ ID NO:403. The antigen binding protein may further bind to its target (PD-L1) with a KD value of 100 nM or less, or a KD value of 50 nM or less.

[0193] In some embodiments, the PD-L1 antigen-binding protein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO:133; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 134.

[0194] In some embodiments, the PD-L1 antigen-binding protein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO:1353; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 136.

[0195] In some embodiments, the PD-L1 antigen-binding protein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO:137; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 138.

[0196] In some embodiments, the PD-L1 antigen-binding protein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO:1393; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 140.

[0197] In some embodiments, the PD-L1 antigen-binding protein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO:141; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 142.

[0198] In some embodiments, the PD-L1 antigen-binding protein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO:143; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 144.

[0199] In some embodiments, the PD-L1 antigen-binding protein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO:322; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 323.

[0200] In some embodiments, the PD-L1 antigen-binding protein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO:145; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 146.

[0201] In some embodiments, the PD-L1 antigen-binding protein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO:398; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 399.

[0202] In some embodiments, the PD-L1 antigen-binding protein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO:400; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 401.

[0203] In some embodiments, the PD-L1 antigen-binding protein comprises: (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO:402; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 403.

[0204] In exemplary aspects, the PD-L1 antigen binding proteins comprise (a) CDR-H1 amino acid sequence set forth in Sequence Table A and Table K2, or a variant sequence thereof which differs by only 1-4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set forth in Sequence Table A or Table K2; (b) CDR-H2 amino acid sequence set forth in Sequence Table A and Table K2, or a variant sequence thereof which differs by only 1-4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set forth in Sequence Table A or Table K2; (c) a CDR-H3 amino acid sequence set forth in Sequence Table A and Table K2, or a variant sequence thereof which differs by only 1-4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set forth in Sequence Table A or Table K2; (d) a CDR-L1 amino acid sequence set forth in Sequence Table A and Table K2, or a variant sequence thereof which differs by only 1-4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set forth in Sequence Table A or Table K2; (e) a CDR-L2 amino acid sequence set forth in Sequence Table A and Table K2, or a variant sequence thereof which differs by only 1-4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set forth in Sequence Table A or Table K2; (f) a CDR-L3 amino acid sequence set forth in Sequence Table A and Table K2, or a variant sequence thereof which differs by only 1-4 amino acids (e.g., 1, 2, 3, 4 amino acids) or which has at least about 80%, at least about 85%, at least about 90%, or at least about 95% sequence identity to the sequence set forth in Sequence Table A or Table K2; or (g) a combination of any two, three, four, five, or six of (a)-(f). The antigen binding protein may further bind to its target (PD-L1) with a KD value of 100 nM or less, or a KD value of 50 nM or less.

[0205] In exemplary embodiments, the PD-L1 antigen binding protein comprises 3, 4, 5, or all 6 of the amino acid sequences designated by the SEQ ID NOs under the same clone name in Sequence Table A and Table K2. In exemplary embodiments, the antigen binding protein comprises each of the LC CDR amino acid sequences designated by the SEQ ID NOs under the same clone name in Sequence Table A and Table K2 and at least 1 or 2 of the HC CDR amino acid sequences designated by the SEQ ID NOs in under the same clone name of Sequence Table A and Table K2. In exemplary embodiments, the antigen binding protein comprises each of the HC CDR amino acid sequences designated by the SEQ ID NOs under the same clone name in Sequence Table A and Table K2, and at least 1 or 2 of the LC CDR amino acid sequences designated by the SEQ ID NOs under the same clone name in Sequence Table A and Table K2. In exemplary embodiments, the antigen binding protein comprises six CDR amino acid sequences listed under the same clone name in Sequence Table A and Table K2, or comprising six CDR amino acid sequences selected from the group consisting of: (1) SEQ ID NOs: 1-6, (2) SEQ ID NOs: 7- 12, (3) SEQ ID NOs: 13-18, (4) SEQ ID NOs: 19-24, (5) SEQ ID NOs: 25-30, (6) SEQ ID NOs: 31-36, and (7) SEQ ID NOs: 37-42.

[0206] Preferred VH and VL framework sequences for PD-L1 antigen-binding proteins disclosed herein are human framework sequences described in detail above.

[0207] In exemplary embodiments, the PD-L1 antigen-binding protein comprises a VH that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 133, 135, 137, 139, 141, 143, 322, 145, 398, 400, or 402. In exemplary embodiments, the PD-L1 antigen-binding protein comprises a VL that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 134, 136, 138, 140, 142, 323144, 146, 399, 401, or 403. Preferably, the PD-L1 antigen binding protein comprises sequences or variants of sequences from a pair of VH and VL sequences listed under the same clone name in Table C and Table K3.

[0208] The PD-L1 antigen-binding proteins disclosed herein may further comprises a CL, a CH1, and / or a Fc region as described in detail above.

[0209] In some embodiments, the PD-L1 antigen binding protein comprises a CH1 domain, preferably a human CH1 domain (such as a human IgG1 CH1, a human IgG2 CH1, a human IgG3 CH1, or a human IgG4 CH1). Non-limiting examples of human CH1 sequences are provided in the Sequence Tables. In some embodiments, the CH1 domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 242, 259, 261, 265, 269, 422, or 425.

[0210] In certain embodiments, the PD-L1 antigen binding proteins described herein comprises an Fc domain. The Fc domain can be derived from IgA (e.g., IgA1 or lgA2), IgG, IgE, or IgG (e.g., IgG1, lgG2, lgG3, or lgG4). In some embodiments, the Fc domain comprises wild type sequence of a human Fc domain. Non-limiting examples of human Fc domain sequences are provided in the Sequence Table.

[0211] In some embodiments, the Fc domain is the Fc domain of human lgG1 and comprises one or more of the following effector-null mutations: L234A, L235A, and G237A (numbering according to the EU index), often referred as “LALA” mutations.

[0212] In exemplary embodiments, the Fc region comprises a Stable Effector Functionless (SEFL) mutation to reduce the ability to interact with Fcγ receptors. In exemplary aspects, the SEFL mutation comprises one or more of the following mutations, numbered according to the EU system: L242C, A287C, R292C, N297G, V302C, L306C, and / or K334C. In exemplary aspects, the SEFL mutation comprises N297G. In exemplary aspects, the SEFL mutation comprises A287C, N297G, and L306C. In other exemplary aspects, the SEFL mutation comprises R292C, N297G, and V302C (i.e., SEFL2-2).

[0213] In exemplary embodiments, the Fc region comprises a YTE mutation. The M252Y / S254T / T256E (EU index numbering, referred to “YTE”) triple mutation have been shown to increase IgG half-life in cynomolgus monkeys by an approximate 4-fold increase.

[0214] In exemplary embodiments, the PD-L1 antigen binding proteins described herein comprise Fc that is derived from an IgG1. In some embodiments, the Fc comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 243, 250, 251, 252, 253, 254, 255, 413, 423, 426, 263, 267, or 483.

[0215] In exemplary embodiments, the PD-L1 antigen binding proteins described herein comprise an IgG1 heavy chain constant domain. In some embodiments, the heavy chain constant domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 244, 245, 246, 247, 248, 249, 256, 257, 258, 260, 412, 415, 417, 418, 427, 264, 268, or 271.

[0216] In some embodiments, the PD-L1 antigen-binding protein described herein comprising a kappa or lambda light chain constant domain. In some embodiments, the kappa light chain constant domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 236, 237, 240, 414, 416, 419, 420, 421, or 428. In some embodiments, the lambda light chain constant domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 238, 239, 241, or 424.

[0217] The PD-L1 antigen-binding protein may be a full-length immunoglobulin, a Fab, or an scFv. Exemplary full length 4-1BB binding immunoglobulins are shown as Sequence Table E. Exemplary Fab and scFV domains are shown in Sequence Table H and Table K6. The scFv may comprises a linker between VH and VL. Exemplary linker sequences, such as GS-based linkers, are provided in the Sequence Table G.

[0218] In some embodiments, the scFv disclosed herein comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 284 (26F6.002.009 scFv).

[0219] In some embodiments, the scFv disclosed herein comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 436 (scFv from 56039).

[0220] In some embodiments, the Fab disclosed herein comprises a Fab heavy chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to residues 1-221 SEQ ID NO: 451, and a Fab light chain sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 452 (Fab from 56041). 2.5 4-1BB x PD-L1 Bispecific Molecules.

[0221] In various aspects, the antigen binding protein is a bispecific molecule which binds to two different antigens or targets. In various instances, the bispecific molecule binds to both 4-1BB and PD-L1.

[0222] Many different formats of bispecific molecules have been exemplified, some of which are depicted in FIGs.2A-2B, FIGs.13A-13K, and FIGs.14A-14D.

[0223] In these exemplary configurations, different VH chains and VL chains are generally referred to as VHA, VHB, VLA, or VLB, indicating that they bind to two different antigens, a or b. VHA and VLA in general indicates that the variable domain binds to antigen a; VHBand VLBgenerally indicate that the variable domain binds to antigen b. Sometimes, the constant domain may also need to be engineered to ensure correct heavy chain and light chain pairing. Since the engineering in constant domains generally involve limited number of mutations, different versions of constant domains are generally distinguished by CH1 versus CH1’, CH2 vs CH2’, CH3 vs CH3’, or CL vs CL’. Occasionally, complex structures such as the one that is illustrated in FIG.13K may require designations such as CH2(1), CH2(2), CH2(3), CH2(4), etc. to illustrate different constant domains that are used.

[0224] In exemplary aspects, some of the bispecific molecule comprises disclosed herein have 4 antigen binding sites, 2 of which bind to 4-1BB protein and 2 of which bind to PD-L1. Optionally, each 4-1BB binding site is identical to the other and / or each PD-L1 binding site is identical to the other.

[0225] In one particular example, the bispecific molecule comprises an IgG moiety and a scFv moiety. As shown in FIG.14A, there are two Fab moieties that bind to one antigen (e.g., PD-L1 or 4-1BB). Each Fab moiety comprises two chains: a heavy chain comprising a heavy chain variable domain A (VHA) and a CH1 domain, and a light chain comprising a light chain variable domain A (VLA) and a CL domain. Each Fab is connected to one chain of Fc (monomeric CH2- monomeric CH3) to form an antibody (IgG). Because this part of the structure is essentially an IgG, there is no new linker between Fab and Fc (Fab and Fc are connected through “hinge” sequence just like a wildtype IgG). In addition, there are two scFv moieties that bind to the other antigen (e.g., 4-1BB or PD-L1). A first linker then connects the C-terminus of one CH3 domain to the N-terminus of one scFv. Each scFv comprises a heavy chain variable domain B (VHB) and a light chain variable domain B (VLB); and the VHB and VLB are connected via a second linker. This structure is sometimes referred to as “IgG-scFv” format (one or more scFv moieties attached to an IgG molecule). Because each target (PD-L1, 4-1BB) has two binding domains, the bispecific molecules exemplified in FIG.14A is often referred herein to as “bivalent” bispecific molecules; nonetheless, it should be noted that it is also acceptable in the art to refer to such kind of molecule as “tetravalent,” as altogether there are four binding domains. The configuration depicted in FIG.14A is also referred to IgG- scFv(C2) because two copies of scFv are attached at the C-termini of the IgG molecule.

[0226] In another particular example, the bispecific molecule comprises a scFv moiety that is inserted between the Fab and Fc (hinge) region of an immunoglobulin (sometimes referred to as “Fab-scFv-Fc”). For example, as shown in FIG.14B, the bispecific molecule may comprises: (i) two Fab moieties that bind to one antigen (e.g., 4-1BB or PD-L1), wherein each Fab moiety comprises two chains: a heavy chain comprising a heavy chain variable domain A (VHA) and a CH1 domain, and a light chain comprising a light chain variable domain A (VLA) and a CL domain; (ii) two scFv moieties that bind to another antigen (e.g., PD-L1 or 4-1BB), wherein each scFv comprises a heavy chain variable domain B (VHB) and a light chain variable domain B (VLB); and (iii) one Fc region that comprises two chains, each chain comprising a monomeric CH2 domain and a monomeric CH3 domain. A first linker connects the C-terminus of one CH1 domain to the N-terminus of one scFv, a second linker links the VHB and VLB of the scFv moiety, and a third linker connects the C-terminus of one scFv to the N-terminus of one chain of the Fc region. Similar to the IgG-scFv structure, the molecule exemplified in FIG.14B is essentially a tetravalent molecule, with two binding moieties for PD-L1 and two binding moieties for 4-1BB, but often called bivalent bispecific molecules. The configuration depicted in FIG.14B is also referred to Fab-scFv(M2)-Fc because two copies of scFv are inserted in the middle of the IgG molecule.

[0227] Another bispecific configuration is depicted in FIG.2B. The bispecific molecule comprises an antibody (IgG) moiety and a Fab moiety. As shown in FIG.2B, there are two Fab moieties that bind to one antigen (e.g., PD-L1 or 4-1BB). Each Fab moiety comprises two chains: a heavy chain comprising a heavy chain variable domain A (VHA) and a CH1 domain, and a light chain comprising a light chain variable domain A (VLA) and a CL domain. Each Fab is connected to one chain of Fc (monomeric CH2- monomeric CH3) to form an antibody (IgG). In addition, there are two Fab moieties that bind to the other antigen (e.g., 4-1BB or PD-L1). A first linker then connects the C-terminus of one CH3 domain to the N- terminus of one Fab. Each Fab comprises a heavy chain variable domain B (VHB) and a CH1’, and a light chain variable domain B (VLB) and a CL’ domain. This particular structure is sometimes referred to as “IgG-Fab” format (one or more Fab moieties attached to an IgG molecule).

[0228] To ensure that the heavy chain and light chain are paired correctly for an IgG-Fab (i.e., CH1 pairs with CL, and CH1’ pairs with CL’), charge pairs may need to be created. For example, in some aspects, (i) CH1 may comprises a mutation to a positively charged residue and CL may comprise a mutation to a negatively charged residue, such that said CH1 and CL form a first charge pair (top part of Fig.2B), and (ii) CH1’ may comprise a mutation to a negatively charged residue and CL’ may comprise a mutation to a positively charged residue, such that said CH1’ and CL’ form a second charge pair (bottom part of Fig. 2B). Because the CL comprises a negatively charged residue, and the CH1’ also comprises a negatively charged residue, the likelihood of CL and CH1’ mis-pairing is unlikely. That way, mixed pairing of 4-1BB light and PD-L1 heavy chain, or vice versa, can be reduced or inhibited.

[0229] The positively charged residues and negatively charged residues can be introduced at multiple positions in CH1 and CL domain, as long as the residue is present on the surface of the constant domain (such that it can interact with the corresponding residue to form a charge pair), and that the mutation does not generally disrupt the conformation of the constant domain. In an exemplary embodiment, the mutation is introduced at position 183 of the CH domain (EU index numbering), and position 176 of the CL domain (Kabat numbering).

[0230] In general, amino acid residues in the IgG heavy constant domain of an antibody are numbered according the EU index of Edelman et al., 1969, Proc. Natl. Acad. Sci. USA 63(1):78-85 as described in Kabat et al., 1991, referred to herein as the “EU index numbering.” Typically, the constant domain comprises from residue 118 to 447, and the Fc domain comprises from residue 236 to 447 of the human lgG1 constant domain. Comparison between EU numbering and other numbering systems can be found, e.g., at IGMT database.

[0231] The amino acid sequence of human IgG constant region is provided below (SEQ ID NO:246), with position 183 underlined. Position 183 corresponds to residue 66 of SEQ ID NO: 265. CH1 domain comprises residues 1-98, hinge region comprises residues 99-110, CH2 domain comprises residues 111- 223, and CH3 domain comprises residues 224-330. ASTKGPSVFP LAPSSKSTSG GTAALGCLVK DYFPEPVTVS WNSGALTSGV HTFPAVLQSS GLYSLSSVVT VPSSSLGTQT YICNVNHKPS NTKVDKKVEP KSCDKTHTCP PCPAPELLGG PSVFLFPPKP KDTLMISRTP EVTCVVVDVS HEDPEVKFNW YVDGVEVHNA KTKPREEQYN STYRVVSVLT VLHQDWLNGK EYKCKVSNKA LPAPIEKTIS KAKGQPREPQ VYTLPPSRDE LTKNQVSLTC LVKGFYPSDI AVEWESNGQP ENNYKTTPPV LDSDGSFFLY SKLTVDKSRW QQGNVFSCSV MHEALHNHYT QKSLSLSPGK

[0232] If the constant domain is derived from an immunoglobulin other than human IgG1, the sequence may be aligned against SEQ ID NO:246, and a mutation may be introduced at a position that corresponds to residue 66 of SEQ ID NO:246. An amino acid residue of a query sequence "corresponds to" a designated position of a reference sequence (e.g., position 66 of SEQ ID NO:246) when, by aligning the query amino acid sequence with the reference sequence, the position of the residue matches the designated position. Such alignments can be done by hand or by using well-known sequence alignment programs such as ClustalW2, or "BLAST 2 Sequences" using default parameters.

[0233] Amino acid residues of the light chain constant domain are numbered according to Kabat et al., 1991, "Sequences of Proteins of Immunological Interest 5th Ed.", 1991, NATIONAL INSTITUTES OF HEALTH. Kappa light chain also has EU index numbering, and the EU index and Kabat numbering are identical. Lambda light chain does not have EU index numbering.

[0234] The amino acid sequences of example human kappa and lambda constant regions are provided below (SEQ ID NOs:237 and 239), with position 176 underlined. Position 176 corresponds to residue 69 of SEQ ID NO: 237, and residue 69 of SEQ ID NO: 239. Note that the first residue (“R” in SEQ ID NO:237 and “G” in SEQ ID NO:239) is considered an optional junction residue. This residue sometimes is shown as the first residue in the CL domain, and sometimes as the last residue in the VL domain; both are accepted in the art. (R)TVAAPSVFI FPPSDEQLKS GTASVVCLLN NFYPREAKVQ WKVDNALQSG NSQESVTEQD SKDSTYSLSS TLTLSKADYE KHKVYACEVT HQGLSSPVTK SFNRGEC (kappa constant, SEQ ID NO:237) (G)QPKANPTVT LFPPSSEELQ ANKATLVCLI SDFYPGAVTV AWKADGSPVK AGVETTKPSK QSNNKYAASS YLSLTPEQWK SHRSYSCQVT HEGSTVEKTV APTECS (lambda constant, SEQ ID NO:239)

[0235] If the constant domain is derived from an immunoglobulin other than human kappa and lambda, the sequence may be aligned against SEQ ID NO:237 or 239, and a mutation may be introduced at a position that corresponds to residue 69 of SEQ ID NO:237 or 239. An amino acid residue of a query sequence "corresponds to" a designated position of a reference sequence (e.g., position 69 of SEQ ID NO:237 or 239) when, by aligning the query amino acid sequence with the reference sequence, the position of the residue matches the designated position. Such alignments can be done by hand or by using well-known sequence alignment programs such as ClustalW2, or "BLAST 2 Sequences" using default parameters.

[0236] Positively charged residues include lysine, arginine and histidine. In an exemplary embodiment, lysine (K) is used. In an exemplary embodiment, arginine (R) is used. Negatively charged residues include aspartic acid and glutamic acid. In an exemplary embodiment, glutamic acid (E) is used.

[0237] Other positions may also be used to introduce charge pairs. For example, positions 123 and 124 of the CL domains and positions 147 and 213 of CH1 domains may be replaced by positively charged residues or negatively charged residues. Further two or more residues in a constant domain may be changed to introduce additional charge pairs.

[0238] In another exemplary configuration, the bispecific molecule comprises two VH-only binding domains inserted between the Fab and Fc (hinge) region of an immunoglobulin (FIG.14D), sometime referred to as Fab-VH-Fc or Fab-VH(M2)-Fc. A first linker links the C-terminus of the Fab with the N- terminus of the VH, and a second linker linkers the C-terminus of the VH with the N-terminus of the Fc.

[0239] In another exemplary configuration, the bispecific molecule comprises two VH-only binding domains, each linked to one C-terminus of an IgG heavy chain (FIG.14C). This configuration is also referred to as IgG-VH or IgG-VH(C2).

[0240] In another exemplary configuration, the bispecific molecule comprises one scFv attached to the C- terminus of one of the two IgG heavy chains (FIG.13C). This configuration involves bivalent binding of one antigen, and monovalent binding of the second antigen, and referred to as IgG-scFv(C1). The two light chains are identical, whereas the two heavy chains are asymmetric.

[0241] In another exemplary configuration, the bispecific molecule comprises one scFv inserted between the CH1 domain and CH2 domain (hinge region) of one of the two IgG heavy chains (FIG.13D). This configuration involves bivalent binding of one antigen, and monovalent binding of the second antigen, and referred to as Fab-scFv(M1)-Fc. The two light chains are identical, whereas the two heavy chains are asymmetric.

[0242] In another exemplary configuration, the bispecific molecule is a hetero-IG, comprising one scFv linked to one CH2-CH3 chain, and one Fab linked to the other CH2-CH3 chain (FIG.13G). This configuration involves monovalent binding of one antigen through one Fab, and monovalent binding of the second antigen through one scFv. The two heavy chains are asymmetric and there is only one light chain. The configuration is also referred to as [Fab*scFv] hetero-Fc.

[0243] In another exemplary configuration, the bispecific molecule comprises one VH-only binding domain linked to one CH2-CH3 chain, and one Fab linked to the other CH2-CH3 chain (FIG.13H). This configuration involves monovalent binding of one antigen through one Fab, and monovalent binding of the second antigen through one VH-only binding domain. The two heavy chains are asymmetric and there is only one light chain. The configuration is also referred to as [Fab*VH] hetero-Fc.

[0244] In another exemplary configuration, the bispecific molecule comprises one scFv attached to the N- terminus of one of the two IgG heavy chains (FIG.13J). This configuration involves bivalent binding of one antigen, and monovalent binding of the second antigen, and is referred to as scFv(N1)-IgG because only one copy of the scFv is attached to the N-terminus of the IgG. The two light chains are identical, whereas the two heavy chains are asymmetric.

[0245] FIG.13K illustrates another configuration of a bispecific molecule, referred to as ([scFv*Fab] hetero-Fc)-Fc. The molecule comprises four chains, and is essentially a [scFv*Fab] hetero-Fc (Fig.13K) structure linked to a second Fc domain. The molecule comprises (i) a first heavy chain that comprises a scFv linked to a CH2(1)-CH3(1)chain, (ii) a second heavy chain that comprise an IgG heavy chain (with CH2(2)-CH3(2)) linked to a CH2(3)-CH3(3)(i.e., VH-CH1-CH2(2)-CH3(2)-CH2(3)-CH3(3)), (iii) a light chain, and (iv) a CH2(4)-CH3(4)chain. The CH2(1)-CH3(1)from (i) and the CH2(2)-CH3(2)from (ii) form a first Fc domain, and the CH2(3)-CH3(3)from (ii) and the CH2(4)-CH3(4)from (iv) form a second Fc domain. Each CH2-CH3 chain would require certain mutations to create certain charge pairs, such as the two Fc domains are paired correctly.

[0246] FIG.13I illustrates another configuration, essentially a hetero-IgG molecule. In this configuration, one heavy chain and one light chain form a Fab that binds to one antigen, and a second heavy chain and a second light chain form a second Fab that binds to a second antigen. The molecule is an asymmetric molecule with one 4-1BB binding domain and one PD-L1 binding domain. To ensure that the heavy chain and light chain are paired correctly (i.e., CH1 pairs with CL, and CH1’ pairs with CL’), charge pairs may need to be created in CH1, CH1’, CL, and CL’, as disclosed in detail above.

[0247] In addition, additional mutations need to be created such as two identical heavy chains do not pair with each other in the Fc region, such that an asymmetric IgG can be created. In some embodiments, one of the heavy chains uses wild type CH3 sequences, and the other heavy chain comprises mutations in which a positively charged residue in the original wild type is mutated to a negatively charged residue to promote heterologous chain pairing.

[0248] Referring to SEQ ID NO:246 again, CH3 domain comprises residues 224-330. In certain embodiments, a mutation from K to E or D (preferably D) at position 392 (EU index numbering), or at a position that corresponds to residue 275 of SEQ ID NO:246 if EU index is not available, is introduced. In certain embodiments, a mutation from K to D or E (preferably D) at position 409 (EU index numbering), or at a position that corresponds to residue 292 of SEQ ID NO:246 if EU index is not available, is introduced. In certain embodiments, a mutation from K to E or D (preferably D) at position 439 (EU index numbering), or at a position that corresponds to residue 322 of SEQ ID NO:246 if EU index is not available, is introduced. These K residues are underline below. ASTKGPSVFP LAPSSKSTSG GTAALGCLVK DYFPEPVTVS WNSGALTSGV HTFPAVLQSS GLYSLSSVVT VPSSSLGTQT YICNVNHKPS NTKVDKKVEP KSCDKTHTCP PCPAPELLGG PSVFLFPPKP KDTLMISRTP EVTCVVVDVS HEDPEVKFNW YVDGVEVHNA KTKPREEQYN STYRVVSVLT VLHQDWLNGK EYKCKVSNKA LPAPIEKTIS KAKGQPREPQ VYTLPPSRDE LTKNQVSLTC LVKGFYPSDI AVEWESNGQP ENNYKTTPPV LDSDGSFFLY SKLTVDKSRW QQGNVFSCSV MHEALHNHYT QKSLSLSPGK

[0249] A “linker” is a molecule or group of molecules that connects two separate entities (e.g., 4-1BB binding protein and PD-L1 binding protein) to one another and can provide spacing and flexibility between the two entities such that they are able to achieve a conformation in which they, e.g., specifically bind their respective targets (e.g., 4-1BB and PD-L1). Protein linkers are particularly preferred, and they may be expressed as a component of the recombinant protein using standard recombinant DNA techniques well-known in the art. For recombinant proteins described herein comprising two or more linkers (for example IgG-scFv and Fab-scFv-Fc formats), the linkers may all be the same, or some or all of the linkers may be different from each other.

[0250] In some embodiments, the linker is a peptidyl linker. In some embodiments, the peptidyl linker comprises about 1 to 30 amino acid residues. Exemplary linkers include, e.g., a glycine rich peptide; a peptide comprising glycine and serine; a peptide having a sequence [Gly-Gly-Ser]n (SEQ ID NO:436), wherein n is 1, 2, 3, 4, 5, or 6; or a peptide having a sequence [Gly-Gly-Gly-Gly-Ser]n (SEQ ID NO: 389), wherein n is 1, 2, 3, 4, 5, or 6. A glycine rich peptide linker comprises a peptide linker, wherein at least 25% of the residues are glycine. Glycine rich peptide linkers are well known in the art (e.g., Chichili et al. Protein Sci.2013 February; 22(2): 153-167). The peptidyl linker may also be a proline-threonine rich peptide linker.

[0251] As shown in FIGs.2A-2B, FIGs.13A-13K, and FIGs.14A-14D, when bispecific molecule comprises a scFv moiety, mutations may be introduced to scFv to further improve stability. For example, it has been reported that insufficient interface stability between the heavy and light chains of scFv fragments could be the main cause of irreversible scFv inactivation. Fv fragments have been reported to dissociate into heavy-chain variable domains (VH) and light-chain variable domains (VL) with KDvalues ranging from 10−9to 10−6M. An interdomain disulfide bond have been used to further improve scFv stability. For example, mutation to Cys at the site of H44 (Kabat numbering), and mutation to Cys at L100 (Kabat numbering) would not significantly affect the domain folding. The two cysteines can then form an intramolecular disulfide bond to further stabilize the scFv. Such mutation is sometimes referred to as “cysteine clamp.”

[0252] Specific examples of scFv comprising cysteine clamps are shown in Sequence Tables C and D, where mutations at H44 (Kabat numbering) and at L100 (Kabat numbering) were used to create disulfide bonds (referred to as “C-C”). Specific examples of scFv comprising cysteine clamp in a bispecific format are shown in Sequence Table H and K6.

[0253] A cysteine clamp has been introduced in some of the scFv for IgG-scFv bispecific molecules exemplified herein. In some of the Fab-scFv-Fc bispecific molecules, cysteine clamp is not present. Thus, the use (or non-use) of cysteine clamp may require evaluation of stability and biologically activities of the scFv. In general, it is believed that the removal of the constant domain (CH1 and Cλ or Cκ) lowers the stability of the Fv domain. This may require the addition of a linker fusion between the VH and VL domains to avoid molecule dissociation. With the decreased interface between the HC and LC, some Fv domains may have an increased probability of being in a dissociated state, exposing their hydrophobic VH and VL interfaces. This could cause increased aggregation, and require additional stability using a disulfide bond or cysteine clamp that covalently links the VH to the VL. On the other hand, although cysteine clamp tends to create a stabilized product post purification, it could also lead to other issues. A poorly positioned cys-clamp can alter the orientation of the VH and VL domains such that it exposes new interfaces or cause a loss in antigen binding due to a new paratope interface. If possible, a scFv domain lacking a cys-clamp with good biophysical properties could be preferential. In IgG-scFv format, because scFv is located at the C-terminus and more exposed, it appears that a cys-clamp can improve the biophysical properties of scFv, whereas in the Fab-scFv-Fc format, it appears that the scFv without cysteine clamp may be feasible under some circumstances because the scFv is sandwiched between Fab and Fc and thus more protected.

[0254] In some embodiments, the bispecific molecule disclosed herein comprises a CH1 domain, preferably a human CH1 domain (such as a human IgG1 CH1, a human IgG2 CH1, a human IgG3 CH1, or a human IgG4 CH1), as discussed in detail above. Non-limiting examples of human CH1 sequences are provided in the Sequence Tables. In some embodiments, the CH1 domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 242, 259, 261, 265, 269, 422, or 425.

[0255] In certain embodiments, the bispecific molecule disclosed herein comprises an Fc domain, as discussed in detail above. The Fc domain can be derived from IgA (e.g., IgA1 or lgA2), IgG, IgE, or IgG (e.g., IgG1, lgG2, lgG3, or lgG4). In some embodiments, the Fc domain comprises wild type sequence of a human Fc domain. Non-limiting examples of human Fc domain sequences are provided in the Sequence Table.

[0256] In some embodiments, the Fc domain is the Fc domain of human lgG1 and comprises one or more of the following effector-null mutations: L234A, L235A, and G237A (numbering according to the EU index), often referred as “LALA” mutations.

[0257] In exemplary embodiments, the Fc region comprises a Stable Effector Functionless (SEFL) mutation to reduce the ability to interact with Fcγ receptors. In exemplary aspects, the SEFL mutation comprises one or more of the following mutations, numbered according to the EU system: L242C, A287C, R292C, N297G, V302C, L306C, and / or K334C. In exemplary aspects, the SEFL mutation comprises N297G. In exemplary aspects, the SEFL mutation comprises A287C, N297G, and L306C. In other exemplary aspects, the SEFL mutation comprises R292C, N297G, and V302C (i.e., SEFL2-2).

[0258] In exemplary embodiments, the Fc region comprises a YTE mutation. The M252Y / S254T / T256E (EU index numbering, referred to “YTE”) triple mutation have been shown to increase IgG half-life in cynomolgus monkeys by an approximate 4-fold increase.

[0259] In exemplary embodiments, the bispecific molecule disclosed herein comprise Fc that is derived from an IgG1. In some embodiments, the Fc comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 243, 250, 251, 252, 253, 254, 255, 413, 423, 426, 263, 267, or 483.

[0260] In exemplary embodiments, the bispecific molecule disclosed herein comprise an IgG1 heavy chain constant domain. In some embodiments, the heavy chain constant domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 90%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 244, 245, 246, 247, 248, 249, 256, 257, 258, 260, 412, 415, 417, 418, 427, 264, 268, or 271.

[0261] In some embodiments, the bispecific molecule disclosed herein comprising a kappa or lambda light chain constant domain. In some embodiments, the kappa light chain constant domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 236, 237, 240, 414, 416, 419, 420, 421, or 428. In some embodiments, the lambda light chain constant domain comprises a sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO: 238, 239, 241, or 424.

[0262] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:283; and (ii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:220. The bispecific molecule may comprise two copies of each sequence.

[0263] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:287; and (ii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:206. The bispecific molecule may comprise two copies of each sequence.

[0264] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:290; and (ii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:184. The bispecific molecule may comprise two copies of each sequence.

[0265] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:294; and (ii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:186. The bispecific molecule may comprise two copies of each sequence.

[0266] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:297; (ii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:299; and (iii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:300. The bispecific molecule may comprise two copies of each sequence.

[0267] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:304; (ii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:306; and (iii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:307. The bispecific molecule may comprise two copies of each sequence.

[0268] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:311; (ii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:312; and (iii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:307. The bispecific molecule may comprise two copies of each sequence.

[0269] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:315; (ii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:312; and (iii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:317. The bispecific molecule may comprise two copies of each sequence.

[0270] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:320; (ii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:312; and (iii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:300. The bispecific molecule may comprise two copies of each sequence.

[0271] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:443; and (ii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:444. The bispecific molecule may comprise two copies of each sequence.

[0272] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:434; and (ii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:435. The bispecific molecule may comprise two copies of each sequence.

[0273] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:449; and (ii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:450. The bispecific molecule may comprise two copies of each sequence.

[0274] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:451; and (ii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:452. The bispecific molecule may comprise two copies of each sequence.

[0275] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:449; (ii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:450; (iii) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:439; and (iv) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to SEQ ID NO:440.

[0276] In exemplary embodiments, the bispecific molecule comprises: (i) an amino acid sequence at least 60%, at least 65%, at least 70%, at least 75%, at least 80%,...

Claims

WHAT IS CLAIMED:

1. A 4-1BB antigen-binding protein comprising a heavy chain variable domain (VH) and a light chain variable domain (VL), wherein (i) said VH comprises the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO:147, 149, 151, 153, 155, 157, 159, 324, 161, 163, 165, 167, 169, 171, 173, 175, 404, 406, 408, or 410; and (ii) said VL comprises the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 148, 150, 152, 154, 156, 158, 160, 325, 162, 164, 166, 168, 170, 172, 174, 176, 405, 407, 409, or 411.

2. The 4-1BB antigen-binding protein of claim 1, comprising: (1) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.43-48, respectively; (2) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.49-54, respectively; (3) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.55-60, respectively; (4) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.61-66, respectively; (5) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.67-72, respectively; (6) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.73-78, respectively; (7) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.79-84, respectively; (8) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.85-90, respectively; (9) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.91-96, respectively; (10) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.97-102, respectively; (11) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.103-108, respectively; (12) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.109-114, respectively; (13) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.115-120, respectively; (14) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.121-126, respectively;(15) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.127-132, respectively; (16) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.386-391, respectively; or (17) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.392-397, respectively.

3. The 4-1BB antigen-binding protein of claim 1 or 2, comprising a VL framework sequence and a VH framework sequence, and (i) wherein the VL framework sequence and / or the VH framework sequence is at least 90% identical to a human VL germline framework sequence or VH germline sequence, respectively, (ii) wherein said human germline VL framework sequence is the framework sequence of: DPK9, DPK12, DPK18, DPK24, HK102_V1 , DPK1 , DPK8, DPK3, DPK21 , Vg_38K, DPK22, DPK15, DPL16, DPL8, V1-22, Vλ consensus, Vλ1 consensus, Vλ3 consensus, Vκ consensus, Vκ1 consensus, Vκ2 consensus, or Vκ3 consensus, and (iii) wherein said human germline VH framework sequence is the framework sequence of: DP54, DP47, DP50, DP31 , DP46, DP71 , DP75, DP10, DP7, DP49, DP51 , DP38, DP79, DP78, DP73, VH3 consensus, VH5 consensus, VH1 consensus, VH2 consensus, or VH4 consensus.

4. The 4-1BB antigen-binding protein of any one of claims 1-3, comprising: (a) a heavy chain variable region (VH) that is at least 90% identical to SEQ ID NO: 147, 149, 151, 153, 155, 157, 159, 324, 161, 163, 165, 167, 169, 171, 173, 175, 404, 406, 408, or 410; (b) a light chain variable region (VL) that is at least 90% identical to SEQ ID NO: 148, 150, 152, 154, 156, 158, 160, 325, 162, 164, 166, 168, 170, 172, 174, 176, 405, 407, 409, or 411.

5. The 4-1BB antigen-binding protein of any one of claims 1-4, comprising: (1) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.147, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.148; (2) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.149, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.150; (3) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.151, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.152; (4) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.153, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.154; (5) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.155, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.156; (6) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.157, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.158;(7) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.159 or 324, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.160 or 325; (8) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.161, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.162; (9) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.163, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.164 (or 336); (10) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.165, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.166; (11) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.167, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.168; (12) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.169, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.170; (13) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.171, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.172 (or 337); (14) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.173, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.174; (15) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.175, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.176; (15) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.404, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.405; (16) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.406, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.407; (17) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.408, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.409; or (15) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.410, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.

411.

6. A 4-1BB antigen-binding protein that comprises a heavy chain variable domain (VH) and does not comprise a light chain variable domain (VL), wherein said protein comprises the CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, or 385.

7. The 4-1BB antigen-binding protein of claim 6, comprising: (1) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.326-328, respectively; (2) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.329-331, respectively; (3) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.332-334, respectively; (4) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.335-337, respectively; (5) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.338-340, respectively; (6) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.341-343, respectively;(7) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.344-346, respectively; (8) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.347-349, respectively; (9) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.350-352, respectively; (10) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.353-355, respectively; (11) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.356-358, respectively; (12) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.359-361, respectively; (13) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.362-364, respectively; (14) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.365-367, respectively; or (15) a CDR-H1, a CDR-H2, and a CDR-H3 comprising SEQ ID NOs.368-370, respectively; 8. A 4-1BB antigen-binding protein that comprises a heavy chain variable domain (VH) and does not comprise a light chain variable domain (VL), wherein said protein binds to an epitope that comprises residues C102, V71, and Q104, according to the numbering of SEQ ID NO:

272.

9. The 4-1BB antigen-binding protein of claim 8, wherein said epitope further comprises residue P90, according to the numbering of SEQ ID NO:

272.

10. The 4-1BB antigen-binding protein of claims 8 or 9, wherein said epitope further comprises one or more residues selected from the group consisting of: K69, T89, F92, M101, and L112, according to the numbering of SEQ ID NO:

272.

11. The 4-1BB antigen-binding protein of any one of claims 6-10, comprising a VH framework sequence, and (i) wherein said VH framework sequence is at least 90% identical to a human germline framework sequence, and (ii) wherein said human germline VH framework sequence is the framework sequence of: DP54, DP47, DP50, DP31 , DP46, DP71 , DP75, DP10, DP7, DP49, DP51 , DP38, DP79, DP78, DP73, VH3 consensus, VH5 consensus, VH1 consensus, VH2 consensus, or VH4 consensus.

12. The 4-1BB antigen-binding protein of any one of claims 6-11, comprising: a heavy chain variable region (VH) that is at least 90% identical to any one of SEQ ID NOs.371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, and 385.

13. The 4-1BB antigen-binding protein of any one of 6-12, comprising: (a) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.371; (b) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.372; (c) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.373; (d) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.374; (e) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.375; (f) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.376; (g) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.377;(h) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.378; (i) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.379; (j) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.380; (k) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.381; (l) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.382; (m) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.383; (n) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.384; or (o) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.

385.

14. The 4-1BB antigen-binding protein of any one of claims 1-13, wherein said 4-1BB antigen binding protein is a crosslinking dependent agonist of 4-1BB.

15. A PD-L1 antigen-binding protein, comprising (i) the heavy chain CDR-H1, CDR-H2, and CDR-H3 of SEQ ID NO: 133, 135, 137, 139, 141, 143, 322, 145, 398, 400, or 402; and (ii) the light chain CDR-L1, CDR-L2, and CDR-L3 of SEQ ID NO: 134, 136, 138, 140, 142, 144, 323, 146, 399, 401, or 403.

16. The PD-L1 antigen-binding protein of claim 15, comprising: (1) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.1-6, respectively; (2) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.7-12, respectively; (3) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.13-18, respectively; (4) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.19-24, respectively; (5) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.25-30, respectively; (6) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.31-36, respectively; or (7) a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 comprising SEQ ID NOs.37-42, respectively.

17. The PD-L1 antigen-binding protein of claim 15 or 16, comprising a VL framework sequence and a VH framework sequence, and (i) wherein the VL framework sequence and / or the VH framework sequence is at least 90% identical to a human VL germline framework sequence or VH germline framework sequence, respectively, (ii) wherein said human germline VL framework sequence is the framework sequence of: DPK9, DPK12, DPK18, DPK24, HK102_V1 , DPK1 , DPK8, DPK3, DPK21 , Vg_38K, DPK22, DPK15, DPL16, DPL8, V1-22, Vλ consensus, Vλ1 consensus, Vλ3 consensus, Vκ consensus, Vκ1 consensus, Vκ2 consensus, or Vκ3 consensus, and (iii) wherein said human germlineVH framework sequence is the framework sequence of: DP54, DP47, DP50, DP31 , DP46, DP71 , DP75, DP10, DP7, DP49, DP51 , DP38, DP79, DP78, DP73, VH3 consensus, VH5 consensus, VH1 consensus, VH2 consensus, or VH4 consensus.

18. The PD-L1 antigen-binding protein of any one of claims 15-17, comprising: (1) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.133, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.134; (2) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.135, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.136; (3) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.137, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.138; (4) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.139, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.140; (5) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.141, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.142; (6) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.143, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.144; (7) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.322, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.323; (8) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.145, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.146; (9) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.398, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.399; (10) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.400, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.401; or (11) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO.402, and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO.

403.

19. The 4-1BB binding protein of any one of claims 1-14, or the PD-L1 binding protein of any one of claims 15-18, further comprising a CH1 domain, a CH2 domain, a CH3 domain, a CL domain, or any combination thereof.

20. A bispecific molecule, comprising a 4-1BB binding protein of any one of claims 1-14 and a PD-L1 binding protein of any one of claims 15-18.

21. The bispecific molecule of claim 20, wherein the bispecific molecule is one of the following formats: Fab-scFv(M2)-Fc, Fab-VH(M2)-Fc, IgG-scFv(C1), Fab-scFv(M1)-Fc, IgG-scFv(C2), IgG-VH(C2), [Fab*scFv]hetero-Fc, [Fab*VH]hetero-Fc, hetero-IgG, scFv(N1)-IgG, ([scFv*Fab]hetero-Fc)-Fc, and IgG- Fab.

2. The bispecific molecule of claim 20 or 21, comprising: (1) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 283, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 220; (2) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 287, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 206; (3) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 290, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 184; (4) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 294, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 186; (5) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 297, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 300; (6) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 304, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 307; (7) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 311, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 307; (8) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO:312, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 317; (9) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 312, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 300; (10) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 443, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 444; (11) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 434, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 435; (12) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 449, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 450; (13) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 451, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 452; (14) (i) one copy of an amino acid sequence that is at least 90% identical to SEQ ID NO: 449, (ii) one copy of an amino acid sequence that is at least 90% identical SEQ ID NO: 450, (iii) one copy of an amino acid sequence that is at least 90% identical SEQ ID NO: 439; and (iv) one copy of an amino acid sequence that is at least 90% identical SEQ ID NO: 440; (15) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 432, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 433; (16) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 447, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO: 448;(17) (i) one copy of an amino acid sequence that is at least 90% identical to SEQ ID NO: 429, (ii) one copy of an amino acid sequence that is at least 90% identical SEQ ID NO: 430, and (iii) one copy of an amino acid sequence that is at least 90% identical SEQ ID NO:

431. (18) (i) two copies of an amino acid sequence that is at least 90% identical to SEQ ID NO: 442, and (ii) two copies of an amino acid sequence that is at least 90% identical SEQ ID NO:

441.

23. The bispecific molecule of any one of claims 20-22, wherein said bispecific molecule a crosslinking dependent agonist of 4-1BB. 24 A nucleic acid comprising a nucleotide sequence encoding the 4-1BB antigen-binding protein of any one of claims 1-14 or 19, the PD-L1 antigen-binding protein of any one of claims 15-19, the bispecific molecule of any one of claims 20-23, or a polypeptide chain of any one of the foregoing.

25. A vector comprising the nucleic acid of claim 24.

26. A host cell comprising the nucleic acid of claim 24 or the vector of claim 25.

27. A pharmaceutical composition comprising (i) the 4-1BB antigen-binding protein of any one of claims 1-14 or 19, the PD-L1 antigen-binding protein of any one of claims 15-19, or the bispecific molecule of any one of claims 20-23, and (ii) a pharmaceutically acceptable carrier, excipient, or diluent.

28. A method of making the 4-1BB antigen-binding protein of the 4-1BB antigen-binding protein of any one of claims 1-14 or 19, the PD-L1 antigen-binding protein of any one of claims 15-19, or the bispecific molecule of any one of claims 20-23, comprising culturing the host cell of claim 26, under a condition wherein the 4-1BB antigen-binding protein, the PD-L1 antigen-binding protein, or the bispecific molecule is expressed.

29. A method of treating cancer, comprising administering to a subject in need thereof a therapeutically effective amount of the 4-1BB antigen-binding protein of any one of claims 1-14 or 19, the PD-L1 antigen-binding protein of any one of claims 15-19, the bispecific molecule of any one of claims 20-23, or the pharmaceutical composition claim 27.

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