B cell maturation antigen-binding protein

Abstract

To provide a single domain BCMA binding protein that can be used to diagnose and treat signs correlated with B-cell maturation antigen (BCMA) expression.SOLUTION: Provided is a polynucleotide encoding a single domain B cell maturation agent (BCMA) binding protein, the single domain B cell maturation agent (BCMA) binding protein comprising complementarity determining regions CDR1, CDR2, and CDR3, the CDR1, CDR2, and CDR3 each comprising a specific amino acid sequence, the single domain B cell maturation agent (BCMA) binding protein being 80% to 99% identical to the specific amino acid sequence.SELECTED DRAWING: Figure 29

Description

[Technical Field]

[0001] cross reference This application claims the benefit of U.S. Provisional Patent Application No. 62 / 572,375, filed October 13, 2017, which is incorporated herein by reference in its entirety.

[0002] Sequence Listing This application contains a Sequence Listing that has been submitted electronically in ASCII format and is incorporated herein by reference. The ASCII copy, created on October 11, 2018, has the filename 47517-722_601_SL.txt and is 232,688 bytes in size. [Background technology]

[0003] Cancer is the second leading cause of human death after coronary artery disease. Globally, millions of people die from cancer each year. In the United States alone, cancer claims the lives of well over 500,000 people each year, with approximately 1.4 million new cases diagnosed each year. While deaths from heart disease have declined significantly, deaths attributable to cancer in general are increasing. Early in the next century, cancer is predicted to become the leading cause of death.

[0004] Furthermore, even cancer patients who survive early primary cancers share a common experience of their lives being dramatically altered. Many cancer patients experience intense anxiety due to the awareness of the possibility of recurrence or treatment failure. Many cancer patients experience significant physical debilitation after treatment.

[0005] Generally speaking, a fundamental problem in the management of most deadly cancers is the lack of effective, non-toxic systemic therapies. Cancer is a complex disease characterized by genetic mutations that lead to uncontrolled cell proliferation. Cancer cells are present in all organisms, and under normal circumstances, their excessive proliferation is tightly controlled by various physiological factors. Summary of the Invention

[0006] The present disclosure provides single domain B-cell maturation antigen (BCMA) binding proteins that can be used to diagnose and treat indications that correlate with BCMA expression.

[0007] Provided herein are single-domain B-cell maturation agent (BCMA) binding proteins, the BCMA binding proteins comprising complementarity determining regions CDR1, CDR2, and CDR3, wherein (a) the amino acid sequence of CDR1 is as set forth in X1X2X3X4X5X6X7PX8G (SEQ ID NO:1), where X1 is T or S; X2 is N, D, or S; X3 is I, D, Q, H, V, or E; X4 is F, S, E, A, T, M, V, I, D, Q, P, R, or G; X5 is S, M, R, or N; X6 is I, K, S, T, R, E, D, N, V, H, L, A, Q, or G; X7 is S, T, Y, R, or N; and X8 is M, G, or Y; (b) the amino acid sequence of CDR2 is AIX9GX 10 X 11 TX 12 YADSVK (SEQ ID NO:2), wherein X9 is H, N, or S; 10 is F, G, K, R, P, D, Q, H, E, N, T, S, A, I, L, or V; X 11 is S, Q, E, T, K, or D; and X 12 is L, V, I, F, Y, or W; and (c) the amino acid sequence of CDR3 is VPWGX. 13 YHPX 14 X 15 VX 16 (SEQ ID NO:3), wherein X 13 is D, I, T, K, R, A, E, S, or Y; X 14 is R, G, L, K, T, Q, S, or N; X 15 is N, K, E, V, R, M, or D; and X 16 is Y, A, V, K, H, L, M, T, R, Q, C, S, or N.

[0008] In one embodiment, CDR1 does not comprise the amino acid sequence of SEQ ID NO:473. In one embodiment, CDR2 does not comprise the amino acid sequence of SEQ ID NO:474. In one embodiment, CDR3 does not comprise the amino acid sequence of SEQ ID NO:475. In one embodiment, CDR1 and CDR2 do not comprise the amino acid sequences of SEQ ID NOs:473 and 474, respectively. In one embodiment, CDR1 and CDR3 do not comprise the amino acid sequences of SEQ ID NOs:473 and 475, respectively. In one embodiment, CDR2 and CDR3 do not comprise the amino acid sequences of SEQ ID NOs:474 and 475, respectively. In one embodiment, CDR1, CDR2, and CDR3 do not comprise the amino acid sequences of SEQ ID NOs:473, 474, and 475, respectively.

[0009] Provided herein are single domain BCMA binding proteins, wherein the single domain BCMA binding proteins comprise the following formula: f1-r1-f2-r2-f3-r3-f4, where r1 is SEQ ID NO:1; r2 is SEQ ID NO:2; and r3 is SEQ ID NO:3; wherein f1, f2, f3, and f4 are framework residues selected such that the protein is about eighty percent (80%) to about 99% identical to the amino acid sequence set forth in SEQ ID NO:346 or 472. Provided herein are single domain BCMA binding proteins, wherein the single domain BCMA binding protein comprises the following formula: f1-r1-f2-r2-f3-r3-f4, where r1 is SEQ ID NO:1; r2 is SEQ ID NO:2; and r3 is SEQ ID NO:3; where f1, f2, f3, and f4 are framework residues selected such that the protein is about 80% to about 90% identical to the amino acid sequence set forth in SEQ ID NO:346 or 472. In one embodiment, the amino acid sequence of the single domain BCMA binding protein does not include SEQ ID NO:472.

[0010] In some non-limiting examples, r1 comprises the amino acid sequence set forth as any one of SEQ ID NOs:4-117.

[0011] In some non-limiting examples, r2 comprises the amino acid sequence set forth as any one of SEQ ID NOs:118-231.

[0012] In some non-limiting examples, r3 comprises the amino acid sequence set forth as any one of SEQ ID NOs:232-345.

[0013] In other non-limiting examples, the protein comprises the amino acid sequence set forth as any one of SEQ ID NOs:346-460.

[0014] In single domain BCMA binding proteins, f1 may comprise SEQ ID NO:461 or 462.

[0015] In a single domain BCMA binding protein, f2 may comprise SEQ ID NO:463.

[0016] In single domain BCMA binding proteins, f3 may comprise SEQ ID NO:464 or 465.

[0017] In single domain BCMA binding proteins, f4 may comprise SEQ ID NO:466 or 467.

[0018] In one non-limiting example, r1 comprises SEQ ID NO: 76, 114, 115, 116, or 117. In one non-limiting example, r1 comprises SEQ ID NO: 76.

[0019] In one non-limiting example, r1 comprises SEQ ID NO:76, r2 is SEQ ID NO:190, and r3 is SEQ ID NO:304.

[0020] In one non-limiting example, r1 comprises SEQ ID NO:114, r2 comprises SEQ ID NO:228, and r3 comprises SEQ ID NO:342.

[0021] In one non-limiting example, r1 comprises SEQ ID NO:115, r2 comprises SEQ ID NO:229, and r3 comprises SEQ ID NO:343.

[0022] In one non-limiting example, r1 comprises SEQ ID NO:117, r2 comprises SEQ ID NO:231, and r3 comprises SEQ ID NO:345.

[0023] In one non-limiting example, r1 comprises SEQ ID NO:116, r2 comprises SEQ ID NO:230, and r3 comprises SEQ ID NO:344.

[0024] The single domain BCMA binding protein may have an elimination half-life of at least 12 hours, at least 20 hours, at least 25 hours, at least 30 hours, at least 35 hours, at least 40 hours, at least 45 hours, at least 50 hours, at least 100 hours, or more. In some embodiments, the single domain BCMA binding protein further comprises an Fc domain. In some embodiments, the single domain BCMA binding protein further comprises an anti-cancer agent.

[0025] Provided herein is a single domain BCMA binding protein, parent llama anti-BCMA 253BH10 SEQ ID NO:472, or a humanized version of this llama sequence, BH2T, SEQ ID NO 346, comprising a substitution of one or more amino acid residues selected from amino acid positions 26, 27, 28, 29, 30, 31, 32, and 34 of CDR1; positions 52, 54, 55, and 57 of CDR2; and positions 101, 105, 106, and 108 of CDR3, wherein amino acid position 26, if substituted, is substituted with S; amino acid position 27, if substituted, is substituted with D or S; Position 28, if substituted, is substituted with D, Q, H, V, or E; amino acid position 29, if substituted, is substituted with S, E, A, T, M, V, I, D, Q, P, R, or G; amino acid position 30, if substituted, is substituted with M, R, or N; amino acid position 31, if substituted, is substituted with K, S, T, R, E, D, N, V, H, L, A, Q, or G; and amino acid position 32, if substituted, is substituted with T, Y, R. or N; amino acid position 34, if substituted, is substituted with G or Y; amino acid position 52, if substituted, is substituted with N or S; amino acid position 54, if substituted, is substituted with G, K, R, P, D, Q, H, E, N, T, S, A, I, L, or V; amino acid position 55, if substituted, is substituted with Q, E, T, K, or D; amino acid position 57, if substituted, is substituted with V, I, F, Y, or or W; amino acid position 101, if substituted, is substituted with I, T, K, R, A, E, S, or Y; amino acid position 105, if substituted, is substituted with G, L, K, T, Q, S, or N; amino acid position 106, if substituted, is substituted with K, E, V, R, M, or D; and amino acid position 108, if substituted, is substituted with A, V, K, H, L, M, T, R, Q, C, S, or N.

[0026] Such single domain BCMA binding proteins may be human, humanized, affinity matured, or a combination thereof.

[0027] Provided herein are methods for treating or ameliorating a B-cell hematology cancer in a subject, the method comprising administering to the subject a single domain BCMA binding protein described herein.

[0028] Provided herein are multispecific binding proteins, including the single domain BCMA binding proteins described herein.

[0029] Provided herein are methods for treating or ameliorating a B-cell hematopoietic cancer in a subject, the methods comprising administering to the subject a multispecific binding protein described herein.

[0030] The B-cell lineage cancer can be a primary cancer or a metastatic cancer.

[0031] The B-cell hematopoietic cancers treated using the methods described herein can be multiple myeloma, leukemia, lymphoma.

[0032] Incorporation by Reference All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. [Brief explanation of the drawings]

[0033] The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings. [Figure 1] Illustrates the effect of exemplary BCMA-targeting molecules (01H08, 01F07, 02F02, and BH253) containing anti-BCMA binding proteins according to the present disclosure in killing BCMA-expressing EJM cells compared to a negative control. [Figure 2]1 is an image of an SDS-PAGE of a representative purified BCMA trispecific molecule. Lane 1: 01F07-M34Y TriTAC non-reduced; lane 2: 01F07-M34G-TriTAC non-reduced; lane 3: 02B05 TriTAC non-reduced; lane 4: 02G02-M34Y TriTAC non-reduced; lane 5: 02G02 M34G TriTAC non-reduced; lane 6: broad-range SDS-PAGE standard (Bio-Rad #1610317); lane 7: 01F07-M34Y TriTAC non-reduced; lane 8: 01F07-M34G-TriTAC non-reduced; lane 9: 02B05 TriTAC non-reduced; lane 10: 02G02-M34Y TriTAC non-reduced; lane 11: 02G02 M34G TriTAC non-reduced; and lane 12: broad-range SDS-PAGE standard (Bio-Rad #1610317). [Figure 3A] 1 illustrates the effect of an exemplary BCMA trispecific targeting molecule containing an anti-BCMA binding protein of the present disclosure in killing BCMA-expressing Jeko1 (AC), MOLP-8 (DF), or OPM-2 (GI) cells compared to a negative control. [Figure 3B] 1 illustrates the effect of an exemplary BCMA trispecific targeting molecule containing an anti-BCMA binding protein of the present disclosure in killing BCMA-expressing Jeko1 (AC), MOLP-8 (DF), or OPM-2 (GI) cells compared to a negative control. [Figure 3C] 1 illustrates the effect of an exemplary BCMA trispecific targeting molecule containing an anti-BCMA binding protein of the present disclosure in killing BCMA-expressing Jeko1 (AC), MOLP-8 (DF), or OPM-2 (GI) cells compared to a negative control. [Figure 3D] 1 illustrates the effect of an exemplary BCMA trispecific targeting molecule containing an anti-BCMA binding protein of the present disclosure in killing BCMA-expressing Jeko1 (AC), MOLP-8 (DF), or OPM-2 (GI) cells compared to a negative control. [Figure 3E]1 illustrates the effect of an exemplary BCMA trispecific targeting molecule containing an anti-BCMA binding protein of the present disclosure in killing BCMA-expressing Jeko1 (AC), MOLP-8 (DF), or OPM-2 (GI) cells compared to a negative control. [Figure 3F] 1 illustrates the effect of an exemplary BCMA trispecific targeting molecule containing an anti-BCMA binding protein of the present disclosure in killing BCMA-expressing Jeko1 (AC), MOLP-8 (DF), or OPM-2 (GI) cells compared to a negative control. [Figure 3G] 1 illustrates the effect of an exemplary BCMA trispecific targeting molecule containing an anti-BCMA binding protein of the present disclosure in killing BCMA-expressing Jeko1 (AC), MOLP-8 (DF), or OPM-2 (GI) cells compared to a negative control. [Figure 3H] 1 illustrates the effect of an exemplary BCMA trispecific targeting molecule containing an anti-BCMA binding protein of the present disclosure in killing BCMA-expressing Jeko1 (AC), MOLP-8 (DF), or OPM-2 (GI) cells compared to a negative control. [Figure 3I] 1 illustrates the effect of an exemplary BCMA trispecific targeting molecule containing an anti-BCMA binding protein of the present disclosure in killing BCMA-expressing Jeko1 (AC), MOLP-8 (DF), or OPM-2 (GI) cells compared to a negative control. [Figure 4] Illustrates binding of an exemplary BCMA trispecific targeting protein of the present disclosure (02B05) to purified T cells from four different human donors: Donor 02 (A), Donor 35 (B), Donor 81 (C), Donor 86 (D). [Figure 5] Illustrates binding of an exemplary BCMA trispecific targeting protein (02B05) to cells expressing BCMA, NCI-H929 (A), EJM (B), OPM2 (D), RPMI8226 (E), or to cell lines lacking expression of BCMA, NCI-H510A (C), and DMS-153 (F). [Figure 6]Illustrates the results of a TDCC assay using an exemplary BCMA trispecific target protein (02B05) and BCMA-expressing EJM cells in the presence or absence of human serum albumin (HSA). [Figure 7] Illustrates the results of a TDCC assay using an exemplary BCMA trispecific targeting protein (02B05) and BCMA-expressing EJM cells using varying effector cell to target cell ratios. [Figure 8] Illustrates the results of a TDCC assay using an exemplary BCMA trispecific targeting protein (02B05) and BCMA-expressing OPM2 cells using varying effector cell to target cell ratios. [Figure 9] Illustrates the results of a TDCC assay using an exemplary BCMA trispecific targeting protein (02B05) and BCMA-expressing NCI-H929 cells using various time points and a 1:1 effector to target cell ratio. [Figure 10] Illustrates the results of a TDCC assay using an exemplary BCMA trispecific target protein (02B05), BCMA-expressing EJM cells, and T cells from four different donors in the presence of human serum albumin (HSA). [Figure 11] Illustrates the results of a TDCC assay using an exemplary BCMA trispecific target protein (02B05), BCMA-expressing NCI-H929 cells, and T cells from four different donors in the presence of human serum albumin (HSA). [Figure 12] Illustrates the results of a TDCC assay using an exemplary BCMA trispecific target protein (02B05), BCMA-expressing OPM2 cells, and T cells from four different donors in the presence of human serum albumin (HSA). [Figure 13] Illustrates the results of a TDCC assay using an exemplary BCMA trispecific target protein (02B05), BCMA-expressing RPMI8226 cells, and T cells from four different donors in the presence of human serum albumin (HSA). [Figure 14] Illustrates the results of a TDCC assay using an exemplary BCMA trispecific target protein (02B05), BCMA non-expressing OVCAR8 cells, and T cells from four different donors in the presence of human serum albumin (HSA). [Figure 15] Illustrates the results of a TDCC assay using an exemplary BCMA trispecific target protein (02B05), BCMA non-expressing NCI-H510A cells, and T cells from four different donors in the presence of human serum albumin (HSA). [Figure 16] Illustrates the results of a TDCC assay using an exemplary BCMA trispecific target protein (02B05), BCMA-expressing NCI-H929 cells, and peripheral blood mononuclear cells (PBMCs) from two different cynomolgus monkeys in the presence of human serum albumin (HSA). [Figure 17] Illustrates the results of a TDCC assay using an exemplary BCMA trispecific targeting protein (02B05) comprising a BCMA binding protein of the present disclosure, BCMA-expressing RPMI8226 cells, and peripheral blood mononuclear cells (PBMCs) from two different cynomolgus donors in the presence of human serum albumin (HSA). [Figure 18] FIG. 1 illustrates the expression levels of the T cell activation biomarker CD69 following a TDCC assay using an exemplary BCMA trispecific targeting protein (02B05) comprising a BCMA binding protein of the disclosure and BCMA-expressing EJM cells. [Figure 19] FIG. 1 illustrates the expression levels of the T cell activation biomarker CD25 following a TDCC assay using an exemplary BCMA trispecific targeting protein (02B05) comprising a BCMA binding protein of the disclosure and BCMA-expressing EJM cells. [Figure 20] FIG. 1 illustrates the expression levels of the T cell activation biomarker CD69 following a TDCC assay using an exemplary BCMA trispecific targeting protein (02B05) comprising a BCMA binding protein of the disclosure and BCMA-expressing OPM2 cells. [Figure 21]FIG. 1 illustrates the expression levels of the T cell activation biomarker CD25 following a TDCC assay using an exemplary BCMA trispecific targeting protein (02B05) comprising a BCMA binding protein of the disclosure and BCMA-expressing OPM2 cells. [Figure 22] FIG. 1 illustrates the expression levels of the T cell activation biomarker CD69 following a TDCC assay using an exemplary BCMA trispecific targeting protein (02B05) comprising a BCMA binding protein of the disclosure and BCMA-expressing RPMI8226 cells. [Figure 23] FIG. 1 illustrates the expression levels of the T cell activation biomarker CD25 following a TDCC assay using an exemplary BCMA trispecific targeting protein (02B05) comprising a BCMA binding protein of the disclosure and BCMA-expressing RPMI8226 cells. [Figure 24] 1 illustrates the expression levels of the T cell activation biomarker CD69 following a TDCC assay using an exemplary BCMA trispecific targeting protein (02B05) comprising a BCMA binding protein of the disclosure and BCMA non-expressing OVCAR8 cells. [Figure 25] 1 illustrates the expression levels of the T cell activation biomarker CD25 following a TDCC assay using an exemplary BCMA trispecific targeting protein (02B05) comprising a BCMA binding protein of the disclosure and BCMA non-expressing OVCAR8 cells. [Figure 26] FIG. 1 illustrates the expression levels of the T cell activation biomarker CD69 following a TDCC assay using an exemplary BCMA trispecific targeting protein (02B05) comprising a BCMA binding protein of the disclosure and BCMA non-expressing NCI-H510A cells. [Figure 27] FIG. 1 illustrates the expression levels of the T cell activation biomarker CD25 following a TDCC assay using an exemplary BCMA trispecific targeting protein (02B05) comprising a BCMA binding protein of the present disclosure and BCMA non-expressing NCI-H510A cells. [Figure 28]1 illustrates the expression levels of the cytokine, TNF-α, in co-cultures of T cells and BCMA-expressing target cells (EJM cells) treated with increasing concentrations of an exemplary BCMA-targeted trispecific protein (02B05) comprising a BCMA-binding protein of the present disclosure, or a negative control GFP trispecific protein. [Figure 29] FIG. 1 illustrates the reduction in tumor growth in an RPMI8226 xenograft model treated with an exemplary BCMA-targeted trispecific protein (02B05) comprising a BCMA-binding protein of the present disclosure at various concentrations, or with a vehicle control. [Figure 30] FIG. 1 illustrates the reduction in tumor growth in a Jeko1 xenograft model treated with an exemplary BCMA-targeted trispecific protein (02B05) comprising a BCMA-binding protein of the present disclosure at various concentrations, or with a vehicle control. [Figure 31] FIG. 1 illustrates the concentration of BCMA-targeted trispecific protein in serum samples from cynomolgus monkeys administered various concentrations of an exemplary BCMA-targeted trispecific protein (02B05) comprising a BCMA-binding protein of the disclosure. [Figure 32] 1 shows the results of a TDCC assay using a BCMA-targeting trispecific protein obtained from serum samples of cynomolgus monkeys administered various concentrations of an exemplary BCMA-targeting trispecific protein (02B05), BCMA-expressing EJM cells, and purified human T cells comprising a BCMA-binding protein of the present disclosure, in the presence of serum from cynomolgus monkeys that were not exposed to the BCMA trispecific targeting protein. DETAILED DESCRIPTION OF THE INVENTION

[0034] While preferred embodiments of the present invention have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, changes, and substitutions will occur to those skilled in the art without departing from the invention. It is understood that various alternatives to the embodiments of the invention described herein may be utilized in practicing the invention. The following claims define the scope of the invention, and it is intended that methods and structures within the scope of these claims and their equivalents be covered thereby.

[0035] Specific Definitions The terms used herein are for the purpose of describing particular instances only and are not intended to limit the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, to the extent that the terms "including," "includes," "having," "has," "with," or variations thereof are used in either the detailed description and / or claims, such terms are intended to be included in a manner similar to the term "comprising."

[0036] The terms "about" or "approximately" mean within an acceptable error range for a particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, e.g., the limitations of the measurement system. For example, "about" can mean 1 or more than 1 standard deviation per practice for any value. When particular values ​​are described in this application and in the claims, unless otherwise specified, the term "about" should be assumed to mean within an acceptable error range for the particular value.

[0037] The terms "individual," "patient," or "subject" are used interchangeably. None of the terms require or are limited to a condition characterized by or under the supervision (e.g., continuous or intermittent) of a health care professional (e.g., a physician, registered nurse, nurse practitioner, physician assistant, janitor, or hospice worker).

[0038] "Antibody" typically refers to a Y-shaped tetrameric protein containing two heavy (H) and two light (L) polypeptide chains held together by covalent disulfide bonds and noncovalent interactions. Human light chains contain a variable domain (VL) and a constant domain (CL), which can be easily classified as kappa or lambda based on amino acid sequence and gene locus. Each heavy chain contains one variable domain (VH) and a constant region, which in the case of IgG, IgA, and IgD, contains three domains called CH1, CH2, and CH3 (IgM and IgE have a fourth domain, CH4). In the classification of IgG, IgA, and IgD, the CH1 and CH2 domains are separated by a flexible hinge region, a proline- and cysteine-rich segment of variable length (usually about 10 to about 60 amino acids in IgG). The variable domains of both the light and heavy chains are connected to the constant domains by a "J" region of about 12 or more amino acids, with heavy chains having a "D" region of about 10 additional amino acids. Each class of antibody contains interchain and intrachain disulfide bonds formed by paired cysteine ​​residues. Immunoglobulin molecules have two types of natural disulfide bridges or bonds: interchain and intrachain disulfide bonds. The location and number of interchain disulfide bonds vary depending on the immunoglobulin class and species. Interchain disulfide bonds are located on the surface of the immunoglobulin, are solvent accessible, and are usually relatively easily reduced. In the human IgG1 isotype, there are four interchain disulfide bonds: one from each heavy chain to the light chain and two between heavy chains. Interchain disulfide bonds are not required for chain attachment. As is well known, the cysteine-rich IgG1 hinge region of the heavy chain is generally maintained as consisting of three parts: the upper hinge, the core hinge, and the lower hinge. Those skilled in the art will appreciate that the IgG1 hinge region contains cysteines in the heavy chain that comprise interchain disulfide bonds (two heavy / heavy, two heavy / light), providing structural flexibility that facilitates Fab movement. The interchain disulfide bond between the light and heavy chains of IgG1 is formed between C214 of the kappa or lambda light chain and C220 in the upper hinge region of the heavy chain.The interchain disulfide bonds between the heavy chains are at positions C226 and C229 (all numbered according to the EU index according to Kabat, et al., below).

[0039] As used herein, the term "antibody" includes polyclonal antibodies, multiclonal antibodies, monoclonal antibodies, chimeric antibodies, humanized and primatized antibodies, CDR-grafted antibodies, human antibodies, recombinantly produced antibodies, intrabodies, multispecific antibodies, bispecific antibodies, monovalent antibodies, multivalent antibodies, anti-idiotypic antibodies, synthetic antibodies, immunospecific antibody fragments such as Fd, Fab, F(ab'), F(ab')2 fragments, single-chain fragments (e.g., ScFv and ScFvFc), disulfide-linked Fvs (sdFv), Fd fragments consisting of VH and CH1 domains, linear antibodies, single domain antibodies (VH, VL, or VHH domains, such as heavy-chain-only antibodies lacking light chains) such as sdAbs, including muteins and variants thereof, and any other immunoreactive molecule so long as it contains a domain with a binding site for preferential association with or binding to a BCMA protein; and derivatives thereof, including Fc fusions and other modifications, and any other immunoreactive molecule so long as it contains a domain with a binding site for preferential association with or binding to a BCMA protein. Furthermore, unless contextual constraints dictate otherwise, this term further includes all classes of antibodies (i.e., IgA, IgD, IgE, IgG, and IgM) and all subclasses (i.e., IgG1, IgG2, IgG3, IgG4, IgA1, and IgA2). The heavy-chain constant domains that correspond to the various classes of antibodies are typically designated by the corresponding lowercase Greek letters α, δ, ε, γ, and μ, respectively. The light chains of antibodies of any vertebrate species can be assigned to one of two clearly distinct types, called kappa (κ) and lambda (λ), based on the amino acid sequence of their constant domains.

[0040] The terms "framework" or "FR" residues (or regions) refer to variable domain residues other than the CDR or hypervariable region residues as defined herein. A "human consensus framework" is a framework representing the most commonly occurring amino acid residues in the selection of human immunoglobulin VL or VH framework sequences.

[0041] As used herein, the terms "variable region" or "variable domain" refer to the fact that certain portions of the variable domains differ significantly in sequence among antibodies and are used in the binding and specificity of each particular antibody for its particular antigen. However, variability is not uniformly distributed throughout the variable domains of antibodies. It is concentrated in three segments called complementarity-determining regions (CDRs) or hypervariable regions in both the light- and heavy-chain variable domains. The more highly conserved portions of the variable domains are called framework regions (FRs). Naturally occurring heavy- and light-chain variable domains each contain four FR regions adopting a β-sheet structure, connected by three CDRs that form loops that connect, and in some cases form part of, the β-sheet structure. The CDRs of each chain are held together in close proximity by the FR regions and, together with the CDRs from the other chain, contribute to the formation of the antigen-binding site of antibodies (see Kabat et al., Sequences of Proteins of Immunological Interest, Fifth Edition, National Institutes of Health, Bethesda, Md. (1991)). The constant domains are not directly involved in binding an antibody to an antigen, but exhibit various effector functions, such as participation of the antibody in antibody-dependent cellular toxicity. "Kabat-like variable domain residue numbering" or "Kabat-like amino acid position numbering," and variations thereof, refer to the numbering system used for the heavy chain variable domain or light chain variable domain of the compilation of antibodies in Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991). Using this numbering system, the actual linear amino acid sequence may contain fewer or additional amino acids corresponding to omissions of, or insertions into, FRs or CDRs of the variable domain.For example, a heavy chain variable domain may contain a single amino acid insertion after residue 52 of H2 (residue 52a according to Kabat) and inserted residues after heavy chain FR residue 82 (e.g., residues 82a, 82b, and 82c according to Kabat). The Kabat numbering of residues can be determined for a given antibody by aligning them in the regions of homology with the sequence of the antibody having the "standard" Kabat numbered sequence. It is not intended that the CDRs of this disclosure necessarily correspond to the Kabat numbering convention.

[0042] In some embodiments, the BCMA-binding protein comprises a heavy chain-only antibody, such as a VH or VHH domain. Optionally, the BCMA-binding trispecific protein comprises a heavy chain-only antibody that is an engineered human VH domain. In some examples, the engineered human VH domain is generated by panning a phage display library. In some embodiments, the BCMA-binding protein comprises a VHH. The term "VHH" as used herein refers to a single-chain antibody binding domain lacking light chains. Optionally, the VHH is derived from antibodies of the type found in camelids or cartilaginous fish that naturally lack light chains, or a synthetic non-immune VHH that can be constructed accordingly. Each heavy chain comprises a variable region encoded by V, D, and J exons. Optionally, the VHH is a naturally occurring VHH, e.g., a VHH from camelids, or a recombinant protein comprising a heavy chain variable domain. In some embodiments, the VHH is derived from a species selected from the group consisting of camel, llama, vicuña, guanaco, and cartilaginous fish (such as, but not limited to, shark). In another embodiment, the VHH is derived from an alpaca (such as, but not limited to, Huacaya Alpaca and Suri alpaca).

[0043] As used herein, the term "percent (%) amino acid sequence identity" for a sequence is defined as the percentage of amino acid residues in a candidate sequence that are identical to the amino acid residues in a specific sequence, after aligning the sequences to achieve the maximum percent sequence identity and introducing gaps as necessary, and without considering any conservative substitutions as part of the sequence identity.Alignment for the purpose of determining percent amino acid sequence identity can be achieved in various ways within the art, for example, using publicly available computer software programs such as EMBOSS MATCHER, EMBOSS WATER, EMBOSS STRETCHER, EMBOSS NEEDLE, EMBOSS LALIGN, BLAST, BLAST-2, ALIGN, or Megalign (DNASTAR) software.Those skilled in the art can determine the appropriate parameters for measuring alignment, including any algorithms required to achieve maximum alignment across the full length of the sequences being compared.

[0044] As used herein, "elimination half-life" is used in its ordinary sense, as described in Goodman and Gillman, The Pharmaceutical Basis of Therapeutics 21-25 (Alfred Goodman Gilman, Louis S. Goodman, and Alfred Gilman, eds., 6th ed. 1980). Briefly, the term is meant to encompass a quantitative measure of the time course of drug elimination. The elimination of most drugs is exponential (i.e., follows first-order kinetics) because the drug concentration usually does not reach the concentration required for saturation of the elimination process. The rate of an exponential process can be measured by its rate constant, k, which represents the fractional rate of change per unit of time, or by its half-life, t, which is the time required for 50% of the process to be completed. 1 / 2 The units of these two constants are time, -1 and time. The first-order reaction rate constant and the half-life of the reaction are simply related (k × t 1 / 2=0.693), which may be exchanged accordingly. First-order elimination kinetics dictates that a constant fraction of the drug is lost per unit of time, so a plot of the logarithm of drug concentration versus time is linear for all times after the initial distribution phase (i.e., after drug absorption and distribution are complete). The half-life of drug elimination can be accurately determined from such a graph.

[0045] As used herein, the term "binding affinity" refers to the affinity of a protein described in this disclosure for a binding target and is expressed numerically using a "Kd" value. When two or more proteins are shown to have comparable binding affinities for their binding targets, the Kd values ​​for the binding of each protein to the binding targets are within ±2-fold of each other. When two or more proteins are shown to have comparable binding affinities for a single binding target, the Kd values ​​for the binding of each protein to the single binding target are within ±2-fold of each other. When proteins are shown to bind to two or more targets with comparable binding affinities, the Kd values ​​for the binding of each protein to the two or more targets are within ±2-fold of each other. Generally, a high Kd value corresponds to weak binding. In some embodiments, "Kd" is measured by radiolabeled antigen binding assay (RIA) or surface plasmon resonance assay using a BIACORE®-2000 or BIACORE®-3000 (BIAcore, Inc., Piscataway, NJ). In one embodiment, the "on-rate" or "rate of association" or "k" and the "off-rate" or "rate of dissociation" or "k" are also determined by surface plasmon resonance technology using a BIACORE®-2000 or BIACORE®-3000 (BIAcore, Inc., Piscataway, NJ). In a further embodiment, the "K", "k", and "k" are measured using OCTET® Systems (Pall Life Sciences). In an exemplary method for measuring binding affinity using OCTET® Systems, a ligand, e.g., biotinylated human BCMA, is immobilized on the OCTET® streptavidin capillary sensor tip surface, and the streptavidin tip is then probed with approximately 20-50 μg / ml of human BCMA protein according to the manufacturer's instructions.A solution of PBS / casein is also introduced as a blocking agent. For binding kinetic measurements, the BCMA-binding protein variants are introduced at concentrations ranging from about 10 ng / mL to about 100 μg / mL, about 50 ng / mL to about 5 μg / mL, or about 2 ng / mL to about 20 μg / mL. In some embodiments, the BCMA-binding single domain protein is used at a concentration ranging from about 2 ng / mL to about 20 μg / mL. Complete dissociation is observed in the negative control, assay buffer without binding protein. The kinetic parameters of the binding reaction are then determined using an appropriate tool, for example, ForteBio software.

[0046] Provided herein are BCMA-binding proteins, pharmaceutical compositions, as well as nucleic acids, recombinant expression vectors, and host cells for producing the BCMA-binding proteins. Also provided are methods of using the disclosed BCMA-binding proteins in the prevention and / or treatment of diseases, conditions, and disorders. The BCMA-binding proteins can specifically bind to BCMA. In some embodiments, the BCMA-binding proteins comprise additional domains, such as a CD3-binding domain and an albumin-binding domain.

[0047] B cell maturation antigen (BCMA) B-cell maturation antigen (BCMA, TNFRSF17, CD269) is a transmembrane protein belonging to the tumor necrosis family of receptors (TNFR) superfamily that is expressed primarily on terminally differentiated B cells. BCMA expression is restricted to the B-cell lineage, present on plasma cells and plasmablasts, and to some extent on memory B cells, but virtually absent from peripheral naive B cells. BCMA is expressed on multiple myeloma (MM) cells, leukemia cells, and lymphoma cells.

[0048] BCMA was identified by molecular analysis of the t(4;16)(q26;p13) translocation found in human intestinal T-cell lymphoma, and the in-frame sequence was mapped to chromosomal band 16p13.1.

[0049] The human BCMA cDNA has a 552 bp open reading frame encoding a 184 amino acid polypeptide. The BCMA gene is organized into three exons separated by two introns, each flanking a GT donor and an AG receptor consensus splice site, and encodes a 1.2 kb transcript. The BCMA protein structure contains an integral integral transmembrane protein based on a central 24 amino acid hydrophobic region in an α-helical structure.

[0050] The mouse BCMA gene is located on chromosome 16, syntenic to the human 16p13 region, and contains three additional exons separated by two introns. The gene encodes a 185-amino acid protein. Mouse BCMA mRNA is expressed as a 404-bp transcript, with maximal levels in plasmacytoma cells (J558) and moderate levels in the A20 B-cell lymphoma line. Mouse BCMA mRNA transcripts were detected at lower levels in T-cell lymphoma (EL4, BW5147) and dendritic cell (CB1D6, D2SC1) lines, in contrast to human cell lines of T-cell and dendritic cell origin. The mouse BCMA cDNA sequence shares 69.3% nucleotide identity with the human BCMA cDNA sequence, with slightly higher identity (73.7%) when comparing the coding regions between these two cDNA sequences. The mouse BCMA protein is 62% identical to the human BCMA protein and, like human BCMA, contains one hydrophobic region that may be an internal transmembrane segment. The N-terminal 40-amino acid domain of both mouse and human BCMA proteins contains six conserved cysteine ​​residues, consistent with the formation of a cysteine ​​repeat motif found in the extracellular domain of TNFRs. Similar to members of the TNFR superfamily, BCMA proteins contain conserved aromatic residues 4-6 residues C-terminal from the first cysteine.

[0051] BCMA is not expressed on the cell surface, but rather is located in the Golgi apparatus. The amount of BCMA expression is proportional to the stage of differentiation of the cell (highest in plasma cells).

[0052] BCMA is involved in B cell development and homeostasis through its interaction with its ligands BAFF (B cell-activating factor, also known as TALL-1 or TNFSF13B) and APRIL (A proliferation-inducing ligand).

[0053] BCMA, along with its family members TACI (transmembrane activator and cyclophilin ligand interactor) and BAFF-R (B-cell activating factor receptor, also known as tumor necrosis factor receptor superfamily member 13C), regulates various aspects of humoral immunity, B-cell development, and homeostasis. BCMA expression appears somewhat late in B-cell differentiation and contributes to the long-term survival of plasmablasts and plasma cells in the bone marrow. BCMA also supports the growth and survival of multiple myeloma (MM) cells.

[0054] BCMA is primarily known for its functional activity in mediating the survival of plasma cells that maintain long-term humoral immunity.

[0055] There is a need to have treatment options for solid tumor diseases associated with overexpression of BCMA, such as cancer, multiple myeloma, leukemia, and lymphoma. The present disclosure provides, in certain embodiments, single domain proteins that specifically bind to BCMA on the surface of tumor target cells.

[0056] BCMA-binding proteins BCMA binding proteins are contemplated herein. In certain embodiments, provided herein are binding proteins, such as anti-BCMA single domain antibodies or antibody variants, that bind to an epitope in the BCMA protein. In some embodiments, the BCMA binding protein binds to a human BCMA protein comprising the sequence of SEQ ID NO:468. In some embodiments, the BCMA binding protein binds to a human BCMA protein that comprises a truncated sequence compared to SEQ ID NO:468. In one non-limiting example, the BCMA binding protein binds to a human BCMA protein comprising amino acid residues 5-51 of SEQ ID NO:468.

[0057] In some embodiments, the BCMA binding proteins of the present disclosure can be expressed within multidomain proteins comprising additional immunoglobulin domains. Such multidomain proteins can act by both antitoxin-based inhibition of tumor growth and induction of antibody-dependent cellular cytotoxicity (ADCC). In some embodiments, multidomain proteins comprising the BCMA binding proteins of the present disclosure exhibit complement-dependent cytotoxicity (CDC) activity. In some embodiments, multidomain proteins comprising the BCMA binding proteins of the present disclosure exhibit both ADCC and CDC activity against BCMA-expressing cancer cells. An Fc domain amino acid sequence can be added to the BCMA binding proteins described herein to induce ACDD or CDC. Fc domain amino acid sequences are known in the art and are contemplated herein.

[0058] The BCMA binding proteins described herein bind to the extracellular domain of BCMA. In one example, the BCMA binding proteins described herein bind to amino acid residues 5-51 of human BCMA.

[0059] In some embodiments, the BCMA binding protein is an anti-BCMA antibody or antibody variant. As used herein, the term "antibody variant" refers to variants and derivatives of the antibodies described herein. In certain embodiments, amino acid sequence variants of the anti-BCMA antibodies described herein are contemplated. For example, in certain embodiments, amino acid sequence variants of the anti-BCMA antibodies described herein are contemplated to improve the binding affinity and / or other biological properties of the antibody. Exemplary methods for preparing amino acid variants include, but are not limited to, introducing appropriate modifications into the nucleotide sequence encoding the antibody or peptide synthesis. Such modifications include, for example, deletions from, and / or insertions and / or substitutions of, residues within the amino acid sequence of the antibody.

[0060] Any combination of deletion, insertion, and substitution can be made to arrive at the final construct, provided that the final construct possesses the desired characteristics (e.g., antigen-binding). In certain embodiments, antibody variants with one or more amino acid substitutions are provided. Target sites for substitutional mutagenesis include the CDRs and framework regions. Examples of such substitutions are described below. Amino acid substitutions may be introduced into the desired antibody, and the products may be screened for the desired activity, e.g., retained / improved antigen binding, reduced immunogenicity, or improved antibody-dependent cellular cytotoxicity (ADCC) or complement-dependent cytotoxicity (CDC). Conservative and non-conservative amino acid substitutions are contemplated for preparing antibody variants.

[0061] In another example of substitutions to create variant anti-BCMA antibodies, one or more hypervariable region residues of a parent antibody are substituted. Generally, variants are selected based on a desired improved characteristic compared to the parent antibody, e.g., increased affinity, decreased affinity, decreased immunogenicity, or increased pH-dependent binding. For example, affinity-matured variant antibodies can be generated using, for example, phage display-based affinity maturation techniques, such as those described herein or known in the art.

[0062] In some embodiments, the BCMA-binding proteins described herein are single-domain antibodies, such as the heavy chain variable domain (VH) or variable domain (VHH) of a llama-derived sdAb specific for BCMA, a peptide, a ligand, or a small molecule entity. In some embodiments, the BCMA-binding domain of the BCMA-binding proteins described herein is any domain that binds to BCMA, including, but not limited to, a domain from a monoclonal antibody, a polyclonal antibody, a recombinant antibody, a human antibody, or a humanized antibody. In certain embodiments, the BCMA-binding protein is a single-domain antibody. In other embodiments, the BCMA-binding protein is a peptide. In further embodiments, the BCMA-binding protein is a small molecule.

[0063] It should be noted that, in general, the term "single domain antibody," as used herein in its broadest sense, is not limited to a particular biological source or a particular method of preparation. A single domain antibody is an antibody whose complementarity-determining regions are part of a single domain polypeptide. Examples include, but are not limited to, heavy chain antibodies, antibodies that naturally lack light chains, single domain antibodies derived from traditional four-chain antibodies, engineered antibodies, and single domain scaffolds other than those derived from antibodies. Single domain antibodies can be any of the art or future single domain antibodies. Single domain antibodies can be derived from any species, including, but not limited to, mouse, human, camel, llama, goat, rabbit, and cow. For example, in some embodiments, single domain antibodies of the disclosure are obtained by: (1) isolation of a VHH domain of a naturally occurring heavy chain antibody; (2) expression of a nucleotide sequence encoding a naturally occurring VHH domain; (3) "humanization" of a naturally occurring VHH domain or expression of a nucleic acid encoding such a humanized VHH domain; (4) "camelization" of a naturally occurring VH domain from any animal species, and in particular from mammalian species such as humans, or expression of a nucleic acid encoding such a camelized VH domain; (5) "camelization" of a "domain antibody" or "Dab" or expression of a nucleic acid encoding such a camelized VH domain; (6) use of synthetic or semi-synthetic techniques to prepare proteins, polypeptides, or other amino acid sequences; (7) preparation of a nucleic acid encoding a single domain antibody using techniques known in the art, followed by expression of the nucleic acid obtained as above; and / or (8) any combination of one or more of the foregoing.

[0064] In one embodiment, the single domain antibody corresponds to a VHH domain of a naturally occurring heavy chain antibody directed against BCMA. As further described herein, such VHH sequences can typically be generated or obtained by appropriately immunizing a species of llama with BCMA (i.e. to generate an immune response and / or heavy chain antibodies directed against BCMA), by obtaining a suitable biological sample from said llama (such as a blood sample, serum sample or B cell sample), and generating the VHH sequence directed against BCMA starting from said sample using any suitable technique known in the art.

[0065] In another embodiment, such naturally occurring VHH domains against BCMA are obtained from a naive library of camelid VHH sequences, e.g., by screening such a library using BCMA or at least one portion, fragment, antigenic determinant, or epitope thereof using at least one screening technique known in the art. Such libraries and techniques are described, for example, in WO99 / 37681, WO01 / 90190, WO03 / 025020, and WO03 / 035694. Alternatively, improved synthetic or semi-synthetic libraries derived from naive VHH libraries are used, such as VHH libraries obtained from naive VHH libraries by techniques such as random mutagenesis and / or CDR shuffling, as described in WO00 / 43507.

[0066] In a further embodiment, yet another technique for obtaining VHH sequences directed against BCMA involves appropriately immunizing a transgenic mammal capable of expressing heavy chain antibodies (i.e., to produce an immune response and / or heavy chain antibodies directed against BCMA), obtaining a suitable biological sample from said transgenic mammal (a blood sample, a serum sample, or a sample of B cells), and generating VHH sequences directed against BCMA starting from said sample using any suitable technique known in the art. For example, heavy chain antibody-expressing rats or mice and methods and techniques such as those described in WO02 / 085945 and WO04 / 049794 can be used for this purpose.

[0067] In some embodiments, anti-BCMA antibodies include single domain antibodies having an amino acid sequence that corresponds to the amino acid sequence of a naturally occurring VHH domain, as described herein, but that has been "humanized", i.e., by replacing one or more amino acid residues in the amino acid sequence of said naturally occurring VHH sequence (and in particular within the framework sequences) with one or more amino acid residues occurring at the corresponding positions in a VH domain from a conventional four-chain antibody of human origin (e.g., as shown above). This can be done in a manner known in the art that will be apparent to the skilled artisan, for example, based on the description further below. Again, such humanized anti-BCMA single domain antibodies of the present disclosure can be obtained in any suitable manner known per se (i.e., as indicated in points (1)-(8) above), and are therefore not strictly limited to polypeptides obtained using a polypeptide comprising a naturally occurring VHH domain as starting material. In some further embodiments, single-domain BCMA antibodies include single-domain antibodies having an amino acid sequence that corresponds to the amino acid sequence of a naturally occurring VH domain as described herein, but that has been "camelized," i.e., by replacing one or more amino acid residues in the amino acid sequence of a naturally occurring VH domain from a conventional four-chain antibody with one or more amino acid residues that occur at the corresponding position in a VHH domain of a heavy-chain antibody. Such "camelizing" substitutions are preferably inserted at amino acid positions that form and / or are present at the VH-VL interface and / or so-called camelid-prominent residues (see, e.g., WO 94 / 04678 and Davies and Riechmann (1994 and 1996)). Preferably, the VH sequence used as starting material or starting point for generating or designing a camelized single domain is a VH sequence, preferably from a mammal, more preferably a human VH sequence, such as a VH3 sequence.It should be noted, however, that in certain embodiments, such camelized anti-BCMA single domain antibodies of the present disclosure are obtained in a manner known in the art (i.e., as set forth in points (1)-(8) above), and are therefore not strictly limited to polypeptides obtained using a naturally occurring VH domain-containing polypeptide as the starting material. For example, as further described herein, both "humanization" and "camelization" are carried out by providing a nucleotide sequence encoding a naturally occurring VHH domain or VH domain, and then altering one or more codons in the provided nucleotide sequence such that the new nucleotide sequence encodes a "humanized" or "camelized" single domain antibody, respectively. This nucleic acid can then be expressed to provide the desired anti-BCMA single domain antibody of the present disclosure. Alternatively, in other embodiments, the amino acid sequence of each of the desired humanized or camelized anti-BCMA single domain antibodies of the present disclosure is designed based on the amino acid sequence of a naturally occurring VHH domain or VH domain, respectively, and then synthesized de novo using known techniques of peptide synthesis. In some embodiments, a nucleotide sequence encoding the desired humanized or camelized anti-BCMA single chain antibody of the disclosure is designed based on the amino acid or nucleotide sequence of a naturally occurring VHH domain or VH domain, respectively, and then synthesized de novo using known techniques for nucleic acid synthesis, and the resulting nucleic acid is then expressed using known expression techniques to obtain the desired anti-BCMA single domain antibody of the disclosure.

[0068] Other suitable methods and techniques for obtaining an anti-BCMA single domain antibody of the disclosure and / or a nucleic acid encoding the anti-BCMA single domain antibody, starting from a naturally occurring VH or VHH sequence, include, for example, combining one or more parts of one or more naturally occurring VH sequences (such as one or more framework (FR) sequences and / or complementarity determining region (CDR) sequences), one or more parts of one or more naturally occurring VHH sequences (such as one or more FR sequences or CDR sequences), and / or one or more synthetic or semi-synthetic sequences in a suitable manner to provide an anti-BCMA single domain antibody of the disclosure or a nucleotide sequence or nucleic acid encoding the same.

[0069] In some embodiments, it is contemplated that the BCMA binding protein is quite small, in some embodiments, no more than 25 kD, no more than 20 kD, no more than 15 kD, or no more than 10 kD, hi certain examples, the BCMA binding protein is 5 kD or less when it is a peptide or small molecule entity.

[0070] In some embodiments, the BCMA binding protein comprises an anti-BCMA-specific antibody comprising a heavy chain variable complementarity determining region CDR1, a heavy chain variable CDR2, a heavy chain variable CDR3, a light chain variable CDR1, a light chain variable CDR2, and a light chain variable CDR3. In some embodiments, the BCMA binding protein comprises any domain that binds to BCMA, including but not limited to a monoclonal antibody, a polyclonal antibody, a recombinant antibody, a human antibody, a humanized antibody, or an antigen-binding fragment such as a single domain antibody (sdAb), Fab, Fab', F(ab)2, and Fv fragments, fragments composed of one or more CDRs, single-chain antibodies (e.g., single-chain Fv fragments (scFv)), disulfide-stabilized (dsFv) Fv fragments, heteroconjugate antibodies (e.g., bispecific antibodies), pFv fragments, heavy chain monomers or dimers, light chain monomers or dimers, and dimers consisting of one heavy chain and one light chain. In some embodiments, the BCMA binding protein is a single domain antibody. In some embodiments, the anti-BCMA single domain antibody comprises heavy chain variable complementarity determining regions (CDRs): CDR1, CDR2, and CDR3.

[0071] In some embodiments, a BCMA binding protein of the disclosure is a polypeptide comprising an amino acid sequence made up of four framework regions / sequences (f1-f4) interrupted by three complementarity determining regions / sequences, as represented by the formula: f1-r1-f2-r2-f3-r3-f4, where r1, r2, and r3 are complementarity determining regions CDR1, CDR2, and CDR3, respectively, and f1, f2, f3, and f4 are framework residues. The r1 residues of BCMA binding proteins of the disclosure include, for example, amino acid residues 26, 27, 28, 29, 30, 31, 32, 33, and 34; the r2 residues of BCMA binding proteins of the disclosure include, for example, amino acid residues 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, and 63; and the r3 residues of BCMA binding proteins of the disclosure include, for example, amino acid residues 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, and 108. In some embodiments, the BCMA binding protein comprises an amino acid sequence selected from SEQ ID NOs:346-460.

[0072] In one embodiment, CDR1 does not comprise the amino acid sequence of SEQ ID NO: 473. In one embodiment, CDR2 does not comprise the amino acid sequence of SEQ ID NO: 474. In one embodiment, CDR3 does not comprise the amino acid sequence of SEQ ID NO: 475.

[0073] In some embodiments, the CDR1 comprises the amino acid sequence set forth in SEQ ID NO:1 or a variant thereof having 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions. An exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:4. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:5. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:6. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:7. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:8. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:9. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:10. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:11. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:12. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:13. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:14. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:15. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:16. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:17. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:18. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:19. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:20. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:21. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:22. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:23. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 24. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 25.Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:26. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:27. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:28. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:29. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:30. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:31. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:32. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:33. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:34. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:35. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:36. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:37. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:38. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:39. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:40. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:41. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:42. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:43. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:44. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:45. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:46. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:47. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 48. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 49. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 50.Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:51. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:52. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:53. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:54. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:55. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:56. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:57. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:58. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:59. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:60. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:61. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:62. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:63. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:64. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:65. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:66. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:67. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:68. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:69. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:70. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:71. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:72. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 73. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 74. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 75.Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:76. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:77. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:78. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:79. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:80. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:81. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:82. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:83. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:84. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:85. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:86. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:87. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:88. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:89. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:90. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:91. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:92. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:93. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:94. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:95. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:96. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO:97. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 98. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 99. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 100.Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 101. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 102. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 103. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 104. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 105. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 106. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 107. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 108. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 109. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 110. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 111. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 112. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 113. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 114. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 115. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 116. Another exemplary CDR1 comprises the amino acid sequence set forth in SEQ ID NO: 117.

[0074] In some embodiments, the CDR2 comprises the sequence set forth in SEQ ID NO:2 or a variant having 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions in SEQ ID NO:2. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:118. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:119. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:120. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:121. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:122. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:123. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:124. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:125. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 126. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 127. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 128. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 129. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 130. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 131. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 132. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 133. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 134. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 135. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 136. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 137. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 138.Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 139. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 140. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 141. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 142. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 143. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 144. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 145. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 146. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 147. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 148. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 149. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:150. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:151. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:152. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:153. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:154. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:155. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:156. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:157. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:158. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:159. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:160. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 161. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 162.Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 163. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 164. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 165. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 166. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 167. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 168. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 169. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 170. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 171. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 172. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 173. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 174. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 175. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 176. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 177. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 178. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 179. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 180. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 181. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 182. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 183. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 184. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 185. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 186.Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 187. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 188. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 189. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 190. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 191. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 192. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 193. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 194. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 195. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 196. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 197. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:198. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:199. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:200. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:201. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:202. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:203. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:204. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:205. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:206. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:207. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:208. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 209. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO: 210.Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:211. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:212. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:213. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:214. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:215. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:216. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:217. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:218. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:219. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:220. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:221. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:222. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:223. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:224. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:225. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:226. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:227. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:228. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:229. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:230. Another exemplary CDR2 comprises the amino acid sequence set forth in SEQ ID NO:231.

[0075] In some embodiments, the CDR3 comprises the sequence set forth in SEQ ID NO:3 or a variant having 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions in SEQ ID NO:3. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:232. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:233. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:234. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:235. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:236. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:237. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:238. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:239. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:240. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:241. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:242. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:243. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:244. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:245. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:246. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:247. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:248. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:249. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:250. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO: 251. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO: 252.Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:253. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:254. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:255. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:256. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:257. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:258. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:259. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:260. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:261. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:262. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:263. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:264. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:265. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:266. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:267. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:268. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:269. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:270. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:271. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:272. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:273. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:274. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO: 275. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO: 276.Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:277. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:278. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:279. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:280. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:281. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:282. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:283. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:284. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:285. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:286. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:287. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:288. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:289. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:290. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:291. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:292. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:293. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:294. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:295. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:296. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:297. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:298. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO: 299. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO: 300.Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:301. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:302. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:303. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:304. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:305. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:306. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:307. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:308. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:309. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:310. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:311. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:312. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:313. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:314. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:315. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:316. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:317. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:318. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:319. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:320. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:321. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:322. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO: 323. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO: 324.Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:325. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:326. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:327. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:328. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:329. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:330. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:331. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:332. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:333. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:334. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:335. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:336. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:337. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:338. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:339. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:340. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:341. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:342. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:343. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:344. Another exemplary CDR3 comprises the amino acid sequence set forth in SEQ ID NO:345.

[0076] In various embodiments, the BCMA binding proteins of the disclosure have a CDR1 with an amino acid sequence that is at least about 75%, about 76%, about 77%, about 78%, about 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%, about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, about 99%, or about 100% identical to an amino acid sequence selected from SEQ ID NOs:4-117.

[0077] In various embodiments, the BCMA binding proteins of the disclosure have a CDR2 with an amino acid sequence that is at least about 75%, about 76%, about 77%, about 78%, about 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%, about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, about 99%, or about 100% identical to an amino acid sequence selected from SEQ ID NOs: 118-231.

[0078] In various embodiments, the complementarity determining regions of the BCMA binding proteins of the disclosure have a CDR3 with an amino acid sequence that is at least about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%, about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, about 99%, or about 100% identical to an amino acid sequence selected from SEQ ID NOs:232-345.

[0079] In various embodiments, the BCMA binding proteins of the disclosure have an amino acid sequence that is at least about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%, about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, about 99%, or about 100% identical to an amino acid sequence selected from SEQ ID NOs:346-460.

[0080] In various embodiments, the BCMA binding proteins of the disclosure have a framework 1 (f1) having an amino acid sequence that is at least about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%, about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, about 99%, or about 100% identical to the amino acid sequence set forth in SEQ ID NO:461 or SEQ ID NO:462.

[0081] In various embodiments, the BCMA binding proteins of the disclosure have a framework 2 (f2) having an amino acid sequence that is at least about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%, about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, about 99%, or about 100% identical to the amino acid sequence set forth in SEQ ID NO:463.

[0082] In various embodiments, the BCMA binding proteins of the disclosure have a framework 3 (f3) having an amino acid sequence that is at least about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%, about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, about 99%, or about 100% identical to the amino acid sequence set forth in SEQ ID NO:464 or SEQ ID NO:465.

[0083] In various embodiments, the BCMA binding proteins of the disclosure have a framework 4 (f4) having an amino acid sequence that is at least about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%, about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, about 99%, or about 100% identical to the amino acid sequence set forth in SEQ ID NO:466 or SEQ ID NO:467.

[0084] In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:346. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:347. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:348. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:349. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:350. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:351. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:352. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:353. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:354. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:355. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:356. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:357. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:358. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:359.

[0085] In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:360. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:361. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:362. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:363. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:364. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:365. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:366. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:367. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:368. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:369.

[0086] In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:370. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:371. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:372. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:373. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:374. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:375. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:376. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:377. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:378. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:379.

[0087] In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:380. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:381. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:382. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:383. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:384. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:385. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:386. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:387. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:388. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:389.

[0088] In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:390. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:391. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:392. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:393. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:394. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:395. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:396. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:397. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:398. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:399.

[0089] In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:400. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:401. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:402. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:403. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:404. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:405. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:406. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:407. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:408. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:409.

[0090] In some embodiments, the BCMA binding protein is a humanized single domain antibody comprising the sequence of SEQ ID NO:410. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:411. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:412. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:413. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:414. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:415. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:416. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:417. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:418. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:419.

[0091] In some embodiments, the BCMA binding protein is a humanized single domain antibody comprising the sequence of SEQ ID NO:420. In some embodiments, the BCMA binding protein is a humanized single domain antibody comprising the sequence of SEQ ID NO:421. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:422. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:423. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:424. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:425. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:426. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:427. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:428. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:429.

[0092] In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:430. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:431. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:432. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:433. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:434. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:435. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:436. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:437. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:438. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:439.

[0093] In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:440. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:441. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:442. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:443. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:444. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:445. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:446. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:447. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:448. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO: 449. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO: 450.

[0094] In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:451. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:452. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:453. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:454. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:455. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:456. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:457. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:458. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:459. In some embodiments, the BCMA binding protein is a single domain antibody comprising the sequence of SEQ ID NO:460.

[0095] The BCMA binding proteins described herein can bind to human BCMA with a Kd ranging from about 0.1 nM to about 500 nM. In some embodiments, the hKd range is from about 0.1 nM to about 450 nM. In some embodiments, the hKd range is from about 0.1 nM to about 400 nM. In some embodiments, the hKd range is from about 0.1 nM to about 350 nM. In some embodiments, the hKd range is from about 0.1 nM to about 300 nM. In some embodiments, the hKd range is from about 0.1 nM to about 250 nM. In some embodiments, the hKd range is from about 0.1 nM to about 200 nM. In some embodiments, the hKd range is from about 0.1 nM to about 150 nM. In some embodiments, the hKd range is from about 0.1 nM to about 100 nM. In some embodiments, the hKd range is from about 0.1 nM to about 90 nM. In some embodiments, the hKd range is about 0.2 nM to about 80 nM. In some embodiments, the hKd range is about 0.3 nM to about 70 nM. In some embodiments, the hKd range is about 0.4 nM to about 50 nM. In some embodiments, the hKd range is about 0.5 nM to about 30 nM. In some embodiments, the hKd range is about 0.6 nM to about 10 nM. In some embodiments, the hKd range is about 0.7 nM to about 8 nM. In some embodiments, the hKd range is about 0.8 nM to about 6 nM. In some embodiments, the hKd range is about 0.9 nM to about 4 nM. In some embodiments, the hKd range is about 1 nM to about 2 nM.

[0096] In some embodiments, any of the aforementioned BCMA binding proteins are affinity peptide tagged to facilitate purification. In some embodiments, the affinity peptide tag is six consecutive histidine residues, also known as a His tag or a 6X-His tag (e.g., SEQ ID NO:471).

[0097] In certain embodiments, the BCMA binding proteins of the present disclosure may be incorporated into a BCMA-targeted trispecific protein. In some examples, the trispecific binding protein comprises a CD3-binding domain, a human serum albumin (HSA)-binding domain, and an anti-BCMA binding domain according to the present disclosure. In some examples, the trispecific binding protein comprises the above domains in the following orientation: BCMA-HSA-CD3.

[0098] In certain embodiments, the BCMA binding proteins of the present disclosure preferentially bind membrane-bound BCMA over soluble BCMA. Membrane-bound BCMA refers to the presence of BCMA in or on the cell membrane surface of cells that express BCMA. Soluble BCMA refers to BCMA that is no longer present in or on the cell membrane surface of cells that express or have expressed BCMA. In certain examples, the soluble BCMA is present in the blood and / or lymphatic circulation of a subject. In one embodiment, the BCMA binding protein binds at least 5-fold, 10-fold, 15-fold, 20-fold, 25-fold, 30-fold, 40-fold, 50-fold, 100-fold, 500-fold, or 1000-fold more membrane-bound BCMA than soluble BCMA. In one embodiment, the trispecific antigen binding protein of the present disclosure preferentially binds membrane-bound BCMA 30-fold more than soluble BCMA. Determining the preferential binding of an antigen binding protein to membrane-bound BCMA over soluble BCMA can be readily determined using assays well known in the art.

[0099] Incorporation into chimeric antigen receptors (CARs) The BCMA-binding proteins of the present disclosure, e.g., anti-BCMA single-domain antibodies, can be incorporated into chimeric antigen receptors (CARs), in certain instances. Engineered immune effector cells, e.g., T cells or NK cells, can be used to express CARs comprising anti-BCMA single-domain antibodies as described herein. In one embodiment, a CAR comprising an anti-BCMA single-domain antibody as described herein is linked via a hinge region to a transmembrane domain and to a costimulatory domain, e.g., a functional signaling domain obtained from OX40, CD27, CD28, CD5, ICAM-1, LFA-1 (CD11a / CD18), ICOS (CD278), or 4-1BB. In some embodiments, the CAR further comprises sequences encoding intracellular signaling domains, such as 4-1BB and / or CD3 zeta.

[0100] Multispecific proteins targeting BCMA One embodiment provides a multispecific protein comprising a BCMA-binding domain, wherein the BCMA-binding domain is according to any one of the above embodiments. In some embodiments, the multispecific protein comprises a BCMA-binding domain (anti-BCMA domain), a CD3-binding domain (anti-CD3 domain), and an albumin-binding domain (anti-ALB domain) according to any one of the above embodiments. In some embodiments, the BCMA-targeted multispecific protein is a trispecific protein, wherein the trispecific protein has a domain order of H2N-(C)-(A)-(B)-COOH. In some embodiments, the anti-BCMA domain (anti-targeting domain, T), the anti-CD3 domain (C), and the anti-ALB domain (A) are in an orientation of anti-CD3:anti-ALB:anti-BCMA (CAT). In some embodiments, the anti-BCMA domain (anti-targeting domain, T), the anti-CD3 domain (C), and the anti-ALB domain (A) are in an orientation of anti-BCMA:anti-ALB:anti-CD3 (TAC).

[0101] Tumor growth suppression properties In certain embodiments, the BCMA-binding proteins of the present disclosure, when administered to a subject bearing tumor cells that express BCMA, inhibit tumor cell growth in vivo. Measurement of tumor cell growth inhibition can be determined by several different methods known in the art. Non-limiting examples include direct measurement of tumor size, measurement of excised tumor masses and comparison with control subjects, and measurement by imaging techniques (e.g., CT or MRI) with or without the use of isotopes or luminescent molecules (e.g., luciferase) to enhance analysis. In certain embodiments, administration of an antigen-binding agent of the present disclosure results in at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100% inhibition of tumor cell growth in vivo compared to a control antigen-binding agent, with about 100% inhibition of tumor growth indicating complete tumor remission or disappearance. In further embodiments, administration of an antigen binding agent of the disclosure results in about 50-100%, about 75-100%, or about 90-100% inhibition of tumor cell proliferation in vivo compared to a control antigen binding agent, hi further embodiments, administration of an antigen binding agent of the disclosure results in about 50-60%, about 60-70%, about 70-80%, about 80-90%, or about 90-100% inhibition of tumor cell proliferation in vivo compared to a control antigen binding agent.

[0102] Modification of BCMA-binding proteins The BCMA binding proteins described herein include derivatives or analogs in which (i) amino acids are substituted with amino acid residues not encoded by the genetic code, (ii) the mature polypeptide is fused with another compound, such as polyethylene glycol, or (iii) additional amino acids are fused to the protein, such as leader or secretory sequences, or sequences for blocking immunogenic domains and / or for purification of the protein.

[0103] Exemplary modifications include, but are not limited to, acetylation, acylation, ADP-ribosylation, amidation, covalent attachment of flavin, covalent attachment of a heme moiety, covalent attachment of a nucleotide or nucleotide derivative, covalent attachment of a lipid or lipid derivative, covalent attachment of phosphatidylinositol, cross-linking, cyclization, disulfide bond formation, demethylation, formation of covalent cross-links, formation of cystine, formation of pyroglutamate, formylation, gamma carboxylation, glycosylation, GPI anchor formation, hydroxylation, iodination, methylation, myristylation, oxidation, protein processing, phosphorylation, prenylation, racemization, selenoylation, sulfation, transfer-RNA-mediated addition of amino acids to proteins, e.g., arginylation, and ubiquitination.

[0104] Modifications may occur anywhere in the BCMA binding proteins described herein, including the peptide backbone, amino acid side chains, and the amino or carboxyl termini. Certain common peptide modifications useful for modifying BCMA binding proteins include glycosylation, lipid conjugation, sulfation, gamma-carboxylation of glutamic acid residues, hydroxylation, blocking of amino or carboxyl groups, or both, in the polypeptide by covalent modifications, and ADP-ribosylation.

[0105] Polynucleotides encoding BCMA-binding proteins In some embodiments, polynucleotide molecules encoding the BCMA binding proteins described herein are also provided. In some embodiments, the polynucleotide molecules are provided as DNA constructs. In other embodiments, the polynucleotide molecules are provided as messenger RNA transcripts.

[0106] Polynucleotide molecules are constructed by known methods, such as by combining a gene encoding an anti-BCMA binding protein operably linked to a suitable promoter and to a suitable transcription terminator, and expressing it in bacteria or other suitable expression systems, e.g., CHO cells.

[0107] In some embodiments, the polynucleotide is inserted into a vector, preferably an expression vector, representing a further embodiment. The recombinant vector can be constructed according to known methods. Vectors of particular interest include plasmids, phagemids, phage derivatives, viruses (e.g., retroviruses, adenoviruses, adeno-associated viruses, herpes viruses, lentiviruses, etc.), and cosmids.

[0108] A variety of expression vector / host systems can be utilized to contain and express the polynucleotide encoding the described BCMA binding protein polypeptides. Examples of expression vectors expressed in E. coli include pSKK (Le Gall et al., J Immunol Methods. (2004) 285(1):111-27), pcDNA5 (Invitrogen) for expression in mammalian cells, PICHIAPINK™ Yeast Expression Systems (Invitrogen), and BACUVANCE™ Baculovirus Expression System (GenScript).

[0109] Thus, the BCMA binding proteins described herein are, in some embodiments, produced by introducing a vector encoding such a protein into a host cell and culturing the host cell under conditions whereby the protein domain can be expressed, isolated, and optionally further purified.

[0110] Pharmaceutical Composition In some embodiments, pharmaceutical compositions are provided comprising a BCMA binding protein described herein, a vector comprising a polynucleotide encoding a BCMA binding protein polypeptide, or a host cell transformed with this vector, and at least one pharmaceutically acceptable carrier. The term "pharmaceutically acceptable carrier" includes, but is not limited to, a carrier that does not interfere with the effectiveness of the biological activity of the components and is not toxic to the patient to whom it is administered. Examples of suitable pharmaceutical carriers are well known in the art and include phosphate-buffered saline, water, emulsions such as oil / water emulsions, various types of wetting agents, sterile solutions, etc. Such carriers can be formulated by conventional methods and administered to a subject in an appropriate dosage. Preferably, the compositions are sterilized. These compositions may also contain adjuvants such as preservatives, emulsifiers, and dispersing agents. Prevention of microbial action can be ensured by the inclusion of various antibacterial and antifungal agents. Further embodiments provide one or more of the above-mentioned binding proteins, such as an anti-BCMA single domain antibody or antigen-binding fragment thereof, packaged in lyophilized form or in an aqueous medium.

[0111] In some embodiments of the pharmaceutical composition, the BCMA binding protein described herein is encapsulated in a nanoparticle. In some embodiments, the nanoparticle is a fullerene, a liquid crystal, a liposome, a quantum dot, a superparamagnetic particle, a dendrimer, or a nanorod. In other embodiments of the pharmaceutical composition, the BCMA binding protein is bound to a liposome. In some examples, the BCMA binding protein is bound to the surface of the liposome. In some examples, the BCMA binding protein is encapsulated within the shell of the liposome. In some examples, the liposome is a cationic liposome.

[0112] The BCMA binding proteins described herein are intended for use as pharmaceuticals. Administration can be achieved by different methods, for example, intravenous, intraperitoneal, subcutaneous, intramuscular, topical, or intradermal administration. In some embodiments, the route of administration depends on the type of treatment and the type of compound contained in the pharmaceutical composition. The administration regimen will be determined by the attending physician and other clinical factors. The dosage for a patient will depend on many factors, including the patient's size, body surface area, age, sex, the specific compound being administered, the time and route of administration, the type of treatment, health status, and other drugs being administered concomitantly. An "effective amount" refers to an amount of active ingredient sufficient to affect the course and severity of the disease, thereby causing a reduction or remission of such pathology, and can be determined using known methods.

[0113] In some embodiments, the BCMA binding proteins of the disclosure are administered weekly at a dose of up to 10 mg / kg. In some cases, the dose ranges from about 1 ng / kg to about 10 mg / kg. In some embodiments, the dose ranges from about 1 ng / kg to about 10 ng / kg, about 5 ng / kg to about 15 ng / kg, about 12 ng / kg to about 20 ng / kg, about 18 ng / kg to about 30 ng / kg, about 25 ng / kg to about 50 ng / kg, about 35 ng / kg to about 60 ng / kg, about 45 ng / kg to about 70 ng / kg, about 65 ng / kg to about 85 ng / kg, about 80 ng / kg to about 1 μg / kg, or about 0. 5 μg / kg to about 5 μg / kg, about 2 μg / kg to about 10 μg / kg, about 7 μg / kg to about 15 μg / kg, about 12 μg / kg to about 25 μg / kg, about 20 μg / kg to about 50 μg / kg, about 35 μg / kg to about 70 μg / kg, about 45 μg / kg to about 80 μg / kg, about 65 μg / kg to about 90 μg / kg, about 85 μg / kg to about 0.1 mg / kg, and about 0.095 mg / kg to about 10 mg / kg. In some embodiments, the dosage is about 0.1 mg / kg to about 0.2 mg / kg, about 0.25 mg / kg to about 0.5 mg / kg, about 0.45 mg / kg to about 1 mg / kg, about 0.75 mg / kg to about 3 mg / kg, about 2.5 mg / kg to about 4 mg / kg, about 3.5 mg / kg to about 5 mg / kg, about 4.5 mg / kg to about 6 mg / kg, about 5.5 mg / kg to about 7 mg / kg, about 6.5 mg / kg to about 8 mg / kg, about 7.5 mg / kg to about 9 mg / kg, or about 8.5 mg / kg to about 10 mg / kg. The frequency of administration, in some embodiments, is about less than daily, every other day, less than once a day, twice a week, weekly, once every seven days, once every two weeks, once every three weeks, once every four weeks, or once a month. In some cases, the frequency of administration is weekly. In some cases, the frequency of administration is weekly and the dose is up to 10 mg / kg. In some cases, the duration of administration is from about 1 day to about 4 weeks or more.

[0114] Treatment method Also provided herein, in some embodiments, are methods and uses for stimulating the immune system of an individual, comprising administering a BCMA binding protein as described herein. In some instances, administration of a BCMA binding protein described herein causes and / or sustains cytotoxicity to cells expressing a target antigen. In some instances, the cells expressing the target antigen are terminally differentiated B cells that are cancer cells or tumor cells, or metastatic cancer cells or tumor cells.

[0115] Also provided herein are methods and uses for the treatment of a BCMA-associated disease, disorder, or condition comprising administering to an individual a BCMA binding protein, or a multispecific binding protein comprising a BCMA binding protein described herein.

[0116] BCMA-associated diseases, disorders, or conditions include, but are not limited to, cancers or metastases of the B-cell lineage.

[0117] Cancers that may be treated, prevented, or managed by the BCMA binding proteins and methods of using the present disclosure include, but are not limited to, primary or metastatic cancers.

[0118] Examples of leukemia include, but are not limited to, acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), and chronic myeloid leukemia (CML), as well as many less common types, such as hairy cell leukemia (HCL), T-cell prolymphocytic leukemia (T-PLL), large granular lymphocytic leukemia, and adult T-cell leukemia. Acute lymphoblastic leukemia (ALL) subtypes to be treated include, but are not limited to, precursor B acute lymphoblastic leukemia, precursor T acute lymphoblastic leukemia, Burkitt's leukemia, and acute mixed lineage leukemia. Chronic lymphocytic leukemia (CLL) subtypes to be treated include, but are not limited to, B-cell prolymphocytic leukemia. Acute myeloid leukemia (AML) subtypes to be treated include, but are not limited to, acute promyelocytic leukemia, acute myeloblastic leukemia, and acute megakaryoblastic leukemia.Chronic myeloid leukemia (CML) subtypes to be treated include, but are not limited to, chronic myelomonocytic leukemia.

[0119] Examples of lymphomas to be treated by the subject method include, but are not limited to, Hodgkin's disease, non-Hodgkin's disease, or any subtype of lymphoma.

[0120] Examples of such multiple myeloma include, but are not limited to, multiple myeloma of tissues such as bone, eg, smoldering multiple myeloma, non-secretory myeloma, osteosclerotic myeloma, and the like.

[0121] For a review of such disorders, see Fishman et al., 1985, Medicine, 2d Ed., J.B. Lippincott Co., Philadelphia and Murphy et al., 1997, Informed Decisions: The Complete Book of Cancer Diagnosis, Treatment, and Recovery, Viking Penguin, Penguin Books USA, Inc., United States of America).

[0122] As used herein, in some embodiments, "treatment," "treating," or "treated" refers to therapeutic treatment aimed at delaying (reducing) an undesired physiological disease, disorder, or condition, or achieving a beneficial or desired clinical outcome. For purposes described herein, beneficial or desired clinical outcomes include, but are not limited to, alleviation of symptoms; reduction in the severity of the disease, disorder, or condition; stabilization of the disease, disorder, or condition (i.e., not worsening); delaying the onset or progression of the disease, disorder, or condition; improvement of the disease, disorder, or condition; and remission (partial or total) of, or enhancement or amelioration of, the disease, disorder, or condition, whether detectable or not. Treatment includes the elicitation of a clinically significant response without excessive levels of side effects. Treatment further includes prolonging survival compared to expected survival in the absence of treatment. In other embodiments, "treatment," "treating," or "treated" refers to prophylactic treatment, the purpose of which is to delay the onset of or reduce the severity of an unwanted physiological disease, disorder, or condition, e.g., in an individual predisposed to the condition (e.g., an individual bearing a genetic marker for a condition such as breast cancer).

[0123] In some embodiments of the methods described herein, a BCMA binding protein as described herein is administered in combination with an agent for the treatment of a particular disease, disorder, or condition. The agent includes, but is not limited to, antibodies, small molecules (e.g., chemotherapeutic agents), hormones (steroids, peptides, etc.), radiation therapy (gamma rays, X-rays, and / or directed delivery of radioisotopes, microwaves, UV radiation, etc.), gene therapy (e.g., antisense, retroviral therapy, etc.), and other immunotherapeutic treatments. In some embodiments, a BCMA binding protein as described herein is administered in combination with an antidiarrheal, antiemetic, analgesic, opioid, and / or nonsteroidal anti-inflammatory drug. In some embodiments, a BCMA binding protein as described herein is administered in combination with an anti-cancer agent. Non-limiting examples of anti-cancer agents that may be used in various embodiments of the present disclosure, including the pharmaceutical compositions, dosage forms, and kits of the present disclosure, include: acivicin; aclarubicin; acodazole hydrochloride; acronine; adozelesin; aldesleukin; altretamine; ambomycin; amethanthrone acetate; aminoglutethimide; amsacrine; anastrozole; anthramycin; asparaginase; asperlin; azacytidine; azetepa; aztomycin; batimastat; benzodepa; bicalutamide; bisantrene hydrochloride; bisnafide dimesylate; biceresin; bleomycin sulfate; brequinar sodium; bropirimine; busulfan; cactinomycin; calste Lon; Caracemide; Carbetimer; Carboplatin; Carmustine; Carubicin hydrochloride; Carzelcin; Cedefingal; Chlorambucil; Cilolemycin; Cisplatin; Cladribine; Crisnatol mesylate; Cyclophosphamide; Cytarabine; Dacarbazine; Dactinomycin; Daunorubicin hydrochloride; Decitabine; Dextromaplatin; Dezaguamine; Dezaguamine mesylate; Diazicon; Docetaxel; Doxorubicin; Doxorubicin hydrochloride; Droloxifene; Droloxifene citrate; Dromostanolone propionate; Duazomycin; Edatrexate; Eflornithine hydrochloride; Elsamitrucin; Enloplatin; Enpromate; Epipropizine;Epirubicin hydrochloride; Elbrozole; Esorubicin hydrochloride; Estramustine; Estramustine phosphate sodium; Etanidazole; Etoposide; Etoposide phosphate; Etoprine; Fadrozole hydrochloride; Fazarabine; Fenretinide; Floxuridine; Fludarabine phosphate; Fluorouracil; Flurocitabine; Foskidone; Fostriecin sodium; Gemcitabine; Gemcitabine hydrochloride; Hydroxyurea; Idarubicin hydrochloride; Ifosfamide; Ilmofosine; Interleukin II (recombinant interleukin II, or rIL2) (including interferon alpha-2a; interferon alpha-2b; interferon alpha-n1, interferon alpha-n3; interferon beta-Ia; interferon gamma-Ib; iproplatin; irinotecan hydrochloride; lanreotide acetate; letrozole; leuprolide acetate; liarozole hydrochloride; lometrexol sodium; lomustine; losoxantrone hydrochloride; masoprocol; maytansine; mechlorethamine hydrochloride; megestrol acetate; melengestrol acetate; melphalan; menogaril; mercaptopurine; methotrexate Cert; methotrexate sodium; metoprine; meturedepa; mitindomide; mitocalcin; mitochromin; mitodilline; mitomarcine; mitomycin; mitosper; mitotane; mitoxantrone hydrochloride; mycophenolic acid; nocodazole; nogalamycin; ormaplatin; ocsislan; paclitaxel; pegaspargase; periomycin; pentamastine; peplomycin sulfate; perfosfamide; pipobroman; piposulfan; piroxantrone hydrochloride; plicamycin; promestane; porfimer sodium; porfiromycin; Prednimastine; Procarbazine hydrochloride; Puromycin; Puromycin hydrochloride; Pyrazofurin; Ribopurine; Rogletimide; Safingol; Safingol hydrochloride; Semustine; Simtrazene; Sparfosate sodium; Sparsomycin; Spirogermanium hydrochloride; Spiromastine; Spiroplatin; Streptonigrin; Streptozocin; Surofenal; Tallysomycin; Tecogalan sodium; Tegafur; Trexatron hydrochloride; Temoporfin; Teniposide; Teloxylon; Testolactone; Thiamiprine; Thioguanine; Thiotepa;Tiazofurin; tirapazamine; toremifene citrate; trestron acetate; tricibirine phosphate; trimetrexate; trimetrexate glucuronate; triptorelin; tuburozole hydrochloride; uracil mustard; uredepa; vapreotide; verteporfin; vinblastine sulfate; vincristine sulfate; vindesine; vindesine sulfate; binepidine sulfate; vinglisinate sulfate; vinleurodine sulfate; vinorelbine tartrate; vinzoquidine sulfate; vinzoquidine sulfate; vorozole; zeniplatin; zinostatin; zorubicin hydrochloride. Other examples of anti-cancer agents include, but are not limited to, 20-epi-1,25 dihydroxyvitamin D3; 5-ethynyluracil; abiraterone; aclarubicin; akylfulvene; adecipenol; adozelesin; aldesleukin; ALL-TK antagonists; altretamine; ambamastine; amidox; amifostine; aminolevulinic acid; amrubicin; amsacrine; anagrelide; anastrozole; andrographolide; angiogenesis inhibitors; antagonist D; antagonist G; antarelix; anti-dorsalizing morphogenetic protein-1 (anti-dorsalizing morphogenetic protein-1) protein-1); antiandrogens, prostate cancer; antiestrogens; antineoplastons; antisense oligonucleotides; aphidicolin glycinate; apoptosis gene modulators; cell death regulators; apurinic acid; ara-CDP-DL-PTBA; arginine deaminase; asulaculin; atamestane; atrimastine; axinastatin 1; axinastatin 2; axinastatin 3; azasetron; azatoxins; azatyrosine; baccatin III derivatives; balanol; batimastat; BCR / A BL antagonists; benzotyroline; benzoylstaurosporine; beta-lactam derivatives; beta-arretin; betaclamycin B; betulinic acid; bFGF inhibitors; bicalutamide; bisantrene; visaziridinylspermine; visnafide; bisstraten A; biceresin; brefulate; bropirimine; budotitanium; buthionine sulfoximine; calcipotriol; calphostin C; camptothecin derivatives; canaripox IL-2; capecitabine; carboxamido-amino-triazoles; carboxyamidotriazoles;CaRest M3; CARN 700; Cartilage-derived inhibitor; Carzelcin; Casein kinase inhibitor (ICOS); Castanospermine; Cecropin B; Cetrorelix; Chlorin; Chloroquinoxaline sulfonamide; Cicaprost; Cis-porphyrin; Cladribine; Clomiphene analogs; Clotrimazole; Collismycin A; Collismycin B; Combretastatin A4; Combretastatin analogs; Conagenin; Crambescidin 816; Crisnatol; Cryptophycin 8; Cryptophycin A derivatives; Crasin A; Cis Clopentane tiraquinose; cycloplatin; sipemycin; cytarabine ocphosphate; cytotoxic factors; cytostatin; daclizumab; decitabine; dehydrodidemin B; deslorelin; dexamethasone; dexifosfamide; dexrazoxane; dexverapamil; diazicon; didemin B; didox; diethylnorspermine; dihydro-5-azacytidine; dihydrotaxol, 9-; dioxamycin; diphenylspiromastine; docetaxel; docosanol; dolasetron; doxifluridine droloxifene; dronabinol; zuocarmycin SA; ebselen; ecomustine; edelfosine; edrecolomab; eflornithine; elemene; emitefur; epirubicin; epristeride; estramustine analogs; estrogen agonists; estrogen antagonists; etanidazole; etoposide phosphate; exemestane; fadrozole; fazarabine; fenretinide; filgrastim; finasteride; flavopiridol; flazelastine; fluasterone; fludarabine; fluoxetine hydrochloride Orodaunornithin; Forfenimex; Formestane; Fostriecin; Fotemustine; Gadolinium texapyrin; Gallium nitrate; Galocitabine; Ganirelix; Gelatinase inhibitors; Gemcitabine; Glutathione inhibitors; Hapsulfame; Heregulin; Hexamethylene bisacetamide; Hypericin; Ibandronic acid; Idarubicin; Idoxifene; Idramantone; Ilmofosine; Ilmostat; Imidazoacridones; Imiquimod; Immunostimulant peptides;Insulin-like growth factor I receptor inhibitors; interferon agonists; interferons; interleukins; iobenguane; iododoxorubicin; ipomeanol, 4-; ilopract; irsogladine; isobengazole; isohomohalichondrin B; itasetron; jasplakinolide; kahalalide F; lamellarin-N triacetate; lanreotide; leinamycin; lenograstim; lentinan sulfate; leptolstatin; letrozole; leukemia inhibitory factor; leukocyte alpha interferon; leuprolide + estrogen + progesterone; Leuprorelin; levamisole; liarozole; linear polyamine analogs; lipophilic disaccharide peptides; lipophilic platinum compounds; lissoclinamide; lobaplatin; lombricin; lometerexol; lonidamine; losoxantrone; HMG-CoA reductase inhibitors (such as, but not limited to, lovastatin, pravastatin, fluvastatin, statins, simvastatin, and atorvastatin); loxolive; raltotecan; lutetium texapyrrin; lisofylline; cytolytic peptides; maytansine; mannostatin A; marimastat; massoprocol; maspin; matrilysin inhibitors; matrix metalloproteinase inhibitors; menogaril; melbarone; metalarelin; methioninase; metoclopramide; MIF inhibitors; mifepristone; miltefosine; millimostim; mismatched double-stranded RNA; mitoguazone; mitolactol; mitomycin analogs; mitonafide; mitotoxin fibroblast growth factor-saporin; mitoxantrone; mofalotene; molgramostim; monoclonal antibodies, human placental gonadotropin; monophosphoryl lipid A + miova Mycobacterium cell wall SK; Mopidamol; Multidrug resistance gene inhibitors; Exogenous tumor suppressor gene 1-based therapeutics; Mustard anticancer drugs; Mycaperoxide B; Mycobacterium cell wall extract; Mirapolon; N-acetyldinaline; N-substituted benzamides; Nafarelin; Nagrestip; Naloxone + pentazocine; Napavine; Nafterpine; Nartograstim; Nedaplatin; Nemorubicin; Nilidronic acid; Neutral endopeptidase; Nilutamide; Nisamycin; Nitric oxide modulators; Nitroxide antioxidants; Nitrulline; O6-benzylguanine;Octreotide; Oxenon; Oligonucleotides; Onapristone; Ondansetron; Ondansetron; Oracin; Oral cytokine inducers; Ormaplatin; Osateron; Oxaliplatin; Oxaunomycin; Paclitaxel; Paclitaxel analogs; Paclitaxel derivatives; Palau; Amines; Palmitoylrhizoxin; Pamidronate; Panaxytriol; Panomyphen; Parabactin; Pazeliptin; Pegaspargase; Perdecin; Pentosan polysulfate sodium; Pentostatin; Pentorozole; Perflubron; Perfosfamide; Peryl alcohol; Phenazinomycin; Phenyl acetate; Phosphatase inhibitors; Picibanil; Pilocarpine hydrochloride; Pirarubicin; Piritrexim; Prasetin A; Prasetin B; Plasminogen activator inhibitors; Platinum complexes; Platinum compounds; Platinum triamine complexes; Porfimer sodium; Porfiromycin; Pre Donisone; Propylbis-acridone; Prostaglandin J2; Proteasome inhibitors; Protein A-based immunomodulators; Protein kinase C inhibitors; Protein kinase C inhibitors, microalgae; Protein tyrosine phosphatase inhibitors; Purine nucleoside phosphorylase inhibitors; Purpurin; Pyrazoloacridine; Pyridoxylated hemoglobin-polyoxyethylene conjugates; RAF antagonists; Raltitrexed; Ramosetron; RAS farnesyl protein transferase inhibitors; RAS inhibitors; RAS-GAP inhibitors; Demethylated leteriptin; Rhenium Re 186 etidronate; Rhizoxin; Ribozyme; RII retinamide; Rogletimide; Rohitukin; Romurtide; Roquinimex; Ravidinone B1; Lavoxil; Safingol; Saintopin; SarCNU; Sarcophytol A; Sargramostim; Sdi 1 mimetics; semustine; senescence-derived inhibitors 1; sense oligonucleotides; signal transduction inhibitors; signal transduction modulators; single-chain antigen-binding proteins; sizofiran; sobuzoxane; sodium borocaptate; sodium phenylacetate; salvalor; somatomedin-binding proteins; sonarmin; sparfosic acid; spicamycin D; spiromastine; splenopentin; spongistatin 1; squalamine; stem cell inhibitors; stem cell division inhibitors; stipiamid; stromelysin inhibitors; sulfinodine; superactive vasoactive intestinal peptide antagonists; saladista; suramin; swainsonine; synthetic glycosaminoglycans; talimustine; tamoxifen methiodide; tauromastine; tazarotene; tecogalan sodium; tegafur;Terlapyrium; telomerase inhibitors; temoporfin; temozolomide; teniposide; tetrachlorodecaoxide; tetrazomine; saliblastine; thiocoraline; thrombopoietin; thrombopoietin mimetics; thymalfadine; thymopoietin receptor agonists; thymotrin; thyroid-stimulating hormone; tin ethyl etioproprine; tirapazamine; titanocene dichloride; topsentin; toremifene; totipotent stem cell factor; translation inhibitors; tretinoin; triacetyluridine; trichibirine; trimethoprim Rexart; triptorelin; tropisetron; turosteride; tyrosine kinase inhibitors; tyrphostins; UBC inhibitors; ubenimex; urogenital sinus-derived growth inhibitors; urokinase receptor antagonists; vapreotide; variolin B; vector systems, erythroid gene therapy drugs; veraresol; veramine; turicola; verteporfin; vinorelbine; vinzartine; VITAXIN®; vorozole; zanoterone; zeniplatin; zilascorub; and zinostatin stimalamer. Additional anticancer agents are 5-fluorouracil and leucovorin. These two agents are particularly useful when used in methods utilizing thalidomide and topoisomerase inhibitors. In some embodiments, the anti-BCMA single domain binding proteins of the present disclosure are used in combination with gemcitabine.

[0124] In some embodiments, a BCMA binding protein as described herein is administered before, during, or after surgery.

[0125] In some embodiments, the anti-cancer agent is conjugated via any suitable means to the trispecific protein.

[0126] Methods for detecting BCMA expression and diagnosing BCMA-associated cancers According to another embodiment of the present disclosure, a kit for detecting BCMA expression in vitro or in vivo is provided. The kit includes a BCMA-binding protein (e.g., a labeled anti-BCMA single domain antibody or antigen-binding fragment thereof) and one or more compounds for detecting the label. In some embodiments, the label is selected from the group consisting of a fluorescent label, an enzymatic label, a radioactive label, a nuclear magnetic resonance active label, a luminescent label, and a chromophore label.

[0127] In some cases, BCMA expression is detected in a biological sample.The sample can be any sample, including but not limited to tissues derived from biopsy, autopsy, and pathological specimens.Biological samples also include tissue sections, such as frozen sections obtained for histological purposes.Biological samples also include body fluids such as blood, serum, plasma, sputum, cerebrospinal fluid, or urine.Biological samples are typically obtained from mammals, such as humans or non-human primates.

[0128] In one embodiment, a method is provided for determining whether a subject has cancer by contacting a sample from the subject with an anti-BCMA single domain antibody as disclosed herein; and detecting binding of the single domain antibody to the sample. Increased binding of the antibody to the sample compared to binding of the antibody to a control sample identifies the subject as having cancer.

[0129] In another embodiment, a method is provided for confirming a diagnosis of cancer in a subject diagnosed with cancer by contacting the subject with an anti-BCMA single domain antibody as disclosed herein and detecting binding of the antibody to the sample. Increased binding of the antibody to the sample compared to binding of the antibody to a control sample confirms the diagnosis of cancer in the subject.

[0130] In some examples of the disclosed methods, the single domain antibody is directly labeled.

[0131] In some examples, the method includes contacting the sample with a second antibody that specifically binds to the single domain antibody; and detecting binding of the second antibody. An increase in binding of the second antibody to the sample compared to binding of the second antibody to a control sample detects cancer in the subject or confirms a diagnosis of cancer in the subject.

[0132] In some cases, the cancer is lymphoma, leukemia, or multiple myeloma.

[0133] In some instances, the control sample is a sample from a subject without cancer. In particular instances, the sample is a blood or tissue sample.

[0134] In some cases, the antibody that binds (e.g., specifically binds) BCMA is directly labeled with a detectable label. In another embodiment, the antibody that binds (e.g., specifically binds) BCMA (the first antibody) is unlabeled, and a second antibody or other molecule capable of binding to the antibody that specifically binds BCMA is labeled. The second antibody is selected to specifically bind to the specific species and class of the first antibody. For example, if the first antibody is a llama IgG, the second antibody can be an anti-llama IgG. Other molecules that can bind to antibodies include, but are not limited to, protein A and protein G, both of which are commercially available. Suitable labels for antibodies or second antibodies are described above and include various enzymes, prosthetic group groups, fluorescent materials, luminescent materials, magnetic agents, and radioactive materials. Non-limiting examples of suitable enzymes include horseradish peroxidase, alkaline phosphatase, β-galactosidase, or acetylcholinesterase. Non-limiting examples of suitable prosthetic group complexes include streptavidin / biotin and avidin / biotin. Non-limiting examples of suitable fluorophores include umbelliferone, fluorescein, fluorescein isothiocyanate, rhodamine, dichlorotriazinylamine fluorescein, dansyl chloride, or phycoerythrin. A non-limiting exemplary luminescent material is luminol; a non-limiting exemplary magnetic agent is gadolinium, and non-limiting exemplary radioactive labels include I, I, S, or H.

[0135] In an alternative embodiment, BCMA can be assayed in a biological sample by a competitive immunoassay that utilizes a BCMA standard labeled with a detectable substance and an unlabeled antibody that specifically binds to BCMA. In this assay, the labeled BCMA standard and the antibody that specifically binds to BCMA are combined, and the amount of labeled BCMA standard bound to the unlabeled antibody is determined. The amount of BCMA in the biological sample is inversely proportional to the amount of labeled BCMA standard bound to the antibody that specifically binds to BCMA.

[0136] The immunoassays and methods disclosed herein can be used for a number of purposes. In one embodiment, an antibody that specifically binds to BCMA may be used to detect BCMA production in cells in cell culture. In another embodiment, the antibody can be used to detect the amount of BCMA in a biological sample, such as a tissue sample or a blood or serum sample. In some instances, the BCMA is cell-surface BCMA. In other instances, the BCMA is soluble BCMA (e.g., BCMA in a cell culture supernatant or soluble BCMA in a body fluid sample, such as a blood or serum sample).

[0137] In one embodiment, a kit is provided for detecting BCMA in a biological sample, such as a blood sample or tissue sample. For example, to confirm a cancer diagnosis in a subject, a biopsy can be performed to obtain a tissue sample for histological examination. Alternatively, a blood sample can be obtained and the presence of soluble BCMA protein or fragments can be detected. Kits for detecting polypeptides typically include a single domain antibody according to the present disclosure that specifically binds to BCMA. In some embodiments, an antibody fragment, such as an scFv fragment, a VH domain, or a Fab, is included in the kit. In further embodiments, the antibody is labeled (e.g., with a fluorescent, radioactive, or enzymatic label).

[0138] In one embodiment, the kit includes instructional materials disclosing means of using antibodies that bind BCMA. The instructional materials may be written in electronic form (such as a computer disk or compact disk), viewable (such as a video file), or provided via an electronic network on the Internet, World Wide Web, an intranet, or other network. The kit may also include additional components to facilitate the particular use for which the kit is designed. Thus, for example, the kit may additionally include means for detecting the label (such as an enzyme substrate for an enzymatic label, a filter set for detecting a fluorescent label, an appropriate secondary label such as a second antibody, etc.). The kit may additionally include buffers and other reagents routinely used in practicing a particular method. Such kits and suitable contents are well known to those of skill in the art.

[0139] In one embodiment, the diagnostic kit comprises an immunoassay. While the details of the immunoassay may vary depending on the particular format employed, methods for detecting BCMA in a biological sample typically involve contacting the biological sample with an antibody that specifically reacts with a BCMA polypeptide under immunologically reactive conditions. The antibody is allowed to specifically bind under immunologically reactive conditions to form an immune complex, and the presence of the immune complex (bound antibody) is detected directly or indirectly.

[0140] Methods for determining the presence or absence of cell surface markers are well known in the art. For example, antibodies can be conjugated to other compounds, including, but not limited to, enzymes, magnetic beads, colloidal magnetic beads, haptens, fluorescent dyes, metal compounds, radioactive compounds, or drugs. Antibodies can also be used in immunoassays, such as, but not limited to, radioimmunoassays (RIA), ELISA, or immunohistochemistry assays. Antibodies can also be used in fluorescence-activated cell sorting (FACS). FACS utilizes multiple color channels, low-angle and obtuse-angle light scattering detection channels, and impedance channels, among other more sophisticated detection levels, to separate or sort cells (see U.S. Patent No. 5,061,620). Any of the single-domain antibodies that bind to BCMA, as disclosed herein, can be used in these assays. Thus, antibodies can be used in conventional immunoassays, including, but not limited to, ELISA, RIA, FACS, tissue immunohistochemistry, Western blot, or immunoprecipitation. [Example]

[0141] The present application may be further understood by reference to the following non-limiting examples, which are provided as exemplary embodiments of the present application. The following examples are presented to more particularly illustrate the embodiments, but should not be construed as limiting the broad scope of the present application.

[0142] Example 1 Ability of exemplary anti-BCMA trispecific domain antibodies, including the BCMA binding proteins of the present disclosure, to mediate T cell killing of BCMA-expressing cancer cells in a TDCC (T cell dependent cytotoxicity) assay

[0143] Protein production

[0144] The sequence of a BCMA-targeted trispecific molecule comprising a BCMA-binding protein according to the present disclosure was cloned into the mammalian expression vector pCDNA 3.4 (Invitrogen) preceded by a leader sequence and followed by a 6x histidine tag (SEQ ID NO:471). Expi293 cells (Life Technologies A14527) were maintained in suspension in Optimum Growth Flasks (Thomson) at 0.2-8x1e6 cells / ml in Expi293 medium. Purified plasmid DNA was transfected into Expi293 cells according to the Expi293 Expression System Kit (Life Technologies A14635) protocol and maintained for 4-6 days post-transfection. The amount of a representative trispecific protein being tested in the conditioned medium from transfected Expi293 cells was quantified using an Octet instrument equipped with a Protein A chip and using a control trispecific protein against a standard curve.

[0145] T cell dependent cytotoxicity test

[0146] A titration of the conditioned medium was used in a TDCC assay (T-cell dependent cell cytotoxicity assay) to assess whether anti-BCMA single domain antibodies could form synapses between T cells and BCMA-expressing cell lines, causing the T cells to kill the BCMA-expressing cell lines. In this assay (Nazarian et al., 2015. J. Biomol. Screen., 20:519-27), T cells and target cancer cell lines were mixed at a 10:1 ratio in a 384-well plate, and varying amounts of the trispecific protein being tested were added. The tumor cell lines were engineered to express luciferase protein. After 48 hours, a STEADY-GLO® Luminescent Assay (Promega) was used to quantify the remaining viable tumor cells.

[0147] This example uses EJM cells, a cell line that serves as an in vitro model for multiple myeloma and plasma cell leukemia. EJM cell viability is measured after 48 hours. The trispecific proteins were confirmed to mediate T cell killing. Figure 1 shows an example of a cell viability assay using test proteins 01H08, 01F07, 02F02, and BH253 compared to a negative control. The EC2 activity of various other trispecific proteins relative to TDCC activity was also assessed. 50 are listed in Table 1 below.

[0148] binding affinity

[0149] In this study, the binding affinity of human BCMA protein to BCMA targeting trispecific proteins, including BCMA binding proteins of the present disclosure, was determined. Affinity measurements are listed in Table 1.

[0150] [Table 1-1]

[0151] [Table 1-2]

[0152] [Table 1-3]

[0153] [Table 1-4]

[0154] ND: Not determined.

[0155] Molecules 01H08, 01F07, 01H06, 02G02, 02B05, 01C01, 02F02, 02E05, 01E08, 02C 01, 02E06, 02B06, 02F04, 01G08, 02C06, 01H09, 01F04, 01D02, 02D11, 01A 07, 02C03, 02F07, 01E04, 02H09, 01E03, 02F05, 01B05, 01C05, 02F12, 01 H11, 02G06, 01E06, 01G11, 02A05, 01A08, 02G05, 01B09, 01G01, 01B06, 01 F10, 01E05, 02G01, 01A06, 02B04, 01D06, 02B07, 02B11, 01H04, 01D03, 01A05, 02F11, 01D04, 01B04, 02C05, 02E03, 01D05, 01C04, 01E07, 01G06, 02F06, 01B01, 01D07, 02A08, 01A02, 02G11, 01G04, 02F03, 01C06, and 01A01 showed at least a two-fold increase in TDCC potency and increased affinity compared to the molecule with the parent CDR, 253BH10.

[0156] Molecule 01H08, 01F07, 01H06, 02G02, 02B05, 01C01, 02F02, 02E05, 01E08, 02C01, 02E06, 02B 06, 02F04, 01G08, 02C06, 01H09, 01F04, 01D02, 02D11, 01A07, 02C03, 02F07, 01E04, 02 H09, 01E03, 02F05, 01B05, 01C05, 02F12, 01H11, 02G06, 01E06, 01G11, 02A05, 01A08, 02G05, and 01B09 showed at least a 10-fold increase in TDCC potency and also increased affinity compared to the molecule with the parent CDR, 253BH10.

[0157] An anti-GFP trispecific molecule included in these assays as a negative control had no detectable BCMA binding or effect on cell viability in the TDCC assay (not shown).

[0158] Example 2 Methods for assessing the binding and cytotoxic activity of purified exemplary trispecific antigen binding proteins comprising a BCMA-binding domain according to the present disclosure against Jeko1, MOLP8, and OPM2 cells

[0159] Protein production

[0160] The sequence of the BCMA-targeting trispecific molecule (SEQ ID NO:471), comprising the BCMA-binding protein of the present disclosure, preceded by a leader sequence and followed by a 6x histidine tag, was expressed using the vector and method previously described (Running Deer and Allison, 2004. Biotechnol Prog. 20:880-9), except that lipid-based reagents and nonlinearized plasmid DNA were used for cell transfection. The recombinant trispecific protein was purified using affinity chromatography, ion exchange, and / or size exclusion chromatography. The purified protein was quantified using theoretical extinction coefficients and spectrophotometry. Coomassie-stained SDS-PAGE images demonstrate the purity of the protein (Figure 2).

[0161] Cytotoxicity assay

[0162] A human T cell-dependent cytotoxicity (TDCC) assay was used to measure the ability of T cell engagers containing trispecific molecules to induce T cells to kill tumor cells (Nazarian et al., 2015. J. Biomol Screen. 20:519-27). In this assay, T cells and cells of the target cancer cell line were mixed at a 10:1 ratio in a 384-well plate, and variable amounts of the trispecific protein to be tested were added. The tumor cell line was engineered to express luciferase protein. After 48 hours, the STEADY-GLO® Luminescent Assay (Promega) was used to quantify the remaining viable tumor cells.

[0163] In this study, titrations of purified proteins were used in TDCC assays (T-cell dependent cytotoxicity assays) to assess whether anti-BCMA single domain antibodies could form synapses between T cells and BCMA-expressing cancer cell lines Jeko1, MOLP-8, and OPM-2. Jeko1 is a B-cell lymphoma cell line. MOLP-8 is a myeloid cell line. OPM-2 is a human myeloid cell line.

[0164] Cell viability was measured after 48 hours, confirming that the trispecific protein mediated T cell killing. Figure 3 shows an example of a cell viability assay using the test protein compared to a negative control. EC20 values ​​for the TDCC activity of various other trispecific proteins were also shown. 50 are listed below in Table 2. An anti-GFP trispecific molecule included in these assays as a negative control had no effect on cell viability (not shown).

[0165] [Table 2]

[0166] binding affinity

[0167] In this study, the binding affinity of human BCMA protein to BCMA targeting trispecific proteins, including BCMA binding proteins of the present disclosure, was determined.

[0168] [Table 3]

[0169] Example 3 ADCC Activity of Exemplary Anti-BCMA Multi-Domain Antibodies of the Disclosure

[0170] This study aimed to determine the ability of exemplary anti-BCMA multi-domain antibodies of the present disclosure to mediate ADCC compared to a parent llama anti-BCMA antibody that does not have sequence modifications or substitutions as the exemplary antibodies of the present disclosure. Both antibodies are expressed as multi-domain proteins that include an additional immunoglobulin Fc domain.

[0171] material

[0172] Donors are leukophoresed and NK cells are isolated from the leukopack by cell purification using the negative selection system of the Milteni AUTOMACS® Pro. NK cells are kept overnight on a rocker at 4°C, washed, counted and collected at 4 x 10 in complete RPMI for use in the ADCC assay. 6 Resuspend in 0.5% PBS containing 0.1% PBS.

[0173] target: Tumor cell targets are selected based on BCMA expression. Targets are washed and counted. 6 x 10 6 of targets are resuspended in complete RPMI and labeled with a final concentration of 10 μM calcein (Sigma #C1359-00UL calcein am 4 mm in anhydrous DMSO) for 40 minutes at 37°C, 5% CO2. Cells are washed twice in PBS, resuspended in complete RPMI, and incubated for 2 hours at 37°C, 5% CO2. After labeling, target cells are washed, recounted, and plated at 0.2 x 10 in complete RPMI for use in the ADCC assay. 6 Resuspend at 1000 cells / mL.

[0174] method

[0175] ADCC assays were performed in 96-well round-bottom tissue culture plates (Corning 3799). Test proteins were titrated from 20 μg / mL to 0.0002 μg / mL by delivering 10 μL (1:10 dilution) in 1000 μL of complete RPMI containing 10% FCS. 50 μL of calcein-labeled target was added, containing 10,000 cells. Target cells and various concentrations of multidomain proteins, including either representative anti-BCMA single-domain antibodies or comparison antibodies, were incubated for 40 minutes at 4°C, after which 50 μL of NK cell effector was added, containing 100,000 cells (10:1 E:T ratio). Cultures were incubated for 4 hours at 37°C, after which supernatants were withdrawn and calcein release was analyzed by measuring fluorescence at 485-535 nm on a Wallac Victor II 1420 Multilable HTS counter. The 100% lysis value is determined by lysing six wells of labeled target with IGEPAL® 630 detergent (3 μL per well), and the spontaneous lysis value is determined by measuring the fluorescence in the supernatant from target alone.

[0176] statistical analysis

[0177] Percent (%) specific lysis was determined as (sample fluorescence) - (spontaneous lysis fluorescence) / (100% lysis - spontaneous lysis fluorescence). Spontaneous lysis is determined by wells containing target only, and 100% lysis is determined by wells in which target is lysed with IGEPAL CA 630 detergent. Raw data are entered into an Excel spreadsheet with an embedded formula to calculate % specific lysis, and the resulting values ​​are transferred to a graphics program (GraphPad Prism) where the data are transformed into curve-fitting graphs. Subsequent analysis (linear regression calculations) was performed in GraphPad, and EC 50 Generate a value.

[0178] Example 4 CDC activity of exemplary anti-BCMA single domain antibodies of the present disclosure

[0179] To assess the anti-tumor activity of exemplary anti-BCMA single domain antibodies according to the present disclosure against cancer cells, their cytotoxic activity is tested in A431 / H9 and NCI-H226 cell models in the presence of human serum as a source of complement. Exemplary anti-BCMA single domain antibodies are expressed as multi-domain proteins that include an Fc domain.

[0180] Multi-domain proteins, including exemplary anti-BCMA single domain antibodies of the present disclosure, exert potent CDC activity by killing cancer cell lines and show no activity on BCMA-negative cell lines.

[0181] Example 5 Xenograft tumor model

[0182] An exemplary BCMA-targeted trispecific protein, 02B05 (SEQ ID NO:383), including an exemplary BCMA-binding protein of the present disclosure, was evaluated in a xenograft model.

[0183] On day 0, NCG mice were inoculated subcutaneously with RPMI-8226 cells and transplanted intraperitoneally with normal human peripheral blood mononuclear cells (PBMCs). Treatment with the exemplary BCMA-targeting trispecific protein also began on day 0 (qdx10) (once daily for 10 days). The doses of the trispecific protein 02B05, or vehicle as a control, were 5 μg / kg, 50 μg / kg, or 500 μg / kg. Tumor volume was determined for 25 days. As shown in Figure 29, the mean tumor volume was significantly smaller in mice treated with the exemplary BCMA-targeting trispecific protein (02B05) (50 μg / kg or 500 μg / kg) than in mice treated with vehicle or a low dose of the BCMA trispecific protein (02B05) (5 μg / kg).

[0184] On day 0, NCG mice were inoculated subcutaneously with Jeko1 cells and transplanted intraperitoneally with normal human peripheral blood mononuclear cells (PBMCs). Treatment with a representative BCMA-targeting trispecific protein also began on day 3 (qdx10) (once daily for 10 days). The doses of the trispecific protein 02B05, or vehicle as a control, were 5 μg / kg, 50 μg / kg, or 500 μg / kg. Tumor volume was determined for 25 days. As shown in Figure 30, the mean tumor volume was significantly smaller in mice treated with the representative BCMA-targeting trispecific protein (02B05) (500 μg / kg) than in mice treated with vehicle or low doses of the BCMA trispecific protein (02B05) (5 μg / kg or 50 μg / kg).

[0185] Example 6 Affinity measurements for human and cynomolgus monkey BCMA, CD3ε, and albumin using exemplary BCMA-targeted trispecifics comprising the BCMA-binding proteins of the present disclosure

[0186] The purpose of this study was to evaluate the affinity of an exemplary BCMA-targeted trispecific protein (02B05) (SEQ ID NO:383) of the present disclosure for human BCMA, cynomolgus BCMA, human CD3ε, cynomolgus CD3ε, human albumin, cynomolgus albumin, and mouse albumin. Affinity was measured using an Octet instrument. For these measurements, the streptavidin tip was first loaded with 2.5 nM human BCMA-Fc, 2.5 nM cynomolgus BCMA-Fc, 2.5 nM human CD3ε-Fc, 2.5 nM cynomolgus CD3ε-Fc, 50 nM human serum albumin (HSA), 50 nM cynomolgus serum albumin, or 50 nM mouse serum albumin. An exemplary BCMA-targeted trispecific protein, 02B05, comprising a BCMA-binding protein of the present disclosure was then incubated with the tip. After an association period, the tip was moved to a buffer solution to allow dissociation of the exemplary BCMA-targeted trispecific protein, 02B05, comprising a BCMA-binding protein of the present disclosure. The affinity for binding to human and cynomolgus BCMA and CD3ε was measured in the presence of 15 mg / ml human serum albumin. The average KD values ​​calculated from these tests are provided in Table 4 (n indicates the number of independent measurements, and n / d indicates no binding detected under the test conditions). Binding to human BCMA, human CD3ε, cynomolgus CD3ε, human serum albumin, cynomolgus serum albumin, and mouse serum albumin was detected. No binding to cynomolgus BCMA was detected under the test conditions.

[0187] [Table 4]

[0188] Example 7 Human T-cell binding capacity of exemplary BCMA-targeted trispecific proteins, including BCMA-binding proteins of the present disclosure

[0189] An exemplary BCMA-targeting trispecific protein, 02B05 (SEQ ID NO:383), including the BCMA binding protein of the present disclosure, was tested for its ability to bind to purified T cells. Briefly, the BCMA trispecific protein or phosphate-buffered saline (PBS) was incubated with purified T cells from four different anonymous human donors. After washing away unbound proteins, the T cells were incubated with an Alexa Fluor 647-conjugated antibody, which recognizes the anti-albumin domain in the 02B05 BCMA trispecific antigen-binding protein. The T cells were then analyzed by flow cytometry. A significant shift in Alexa Fluor 647-associated activity was observed in human T cells incubated with the 02B05 BCMA trispecific antigen-binding protein compared to cells incubated with PBS. The results are shown in Figures 4A, 4B, 4C, and 4D. In conclusion, this study demonstrated that exemplary BCMA-targeting trispecific proteins, including the BCMA binding protein of the present disclosure, were capable of binding to human T cells.

[0190] Example 8 Ability of exemplary BCMA-targeted trispecific proteins of the present disclosure to bind to BCMA-expressing cells

[0191] An exemplary BCMA-targeting trispecific protein, 02B05 (SEQ ID NO:383), including the BCMA-binding proteins of the present disclosure, was tested for its ability to bind to BCMA-expressing cells. Briefly, the 02B05 BCMA trispecific antigen-binding protein was incubated with cell lines expressing BCMA (NCI-H929; EJM; RPMI-8226; OPM2) or lacking BCMA (NCI-H510A; DMS-153). BCMA RNA expression in these cells is shown by the FPKM (fragments per million kilobases) values ​​listed in Figures 5A-F; RNA FPKM values ​​are from the Cancer Cell Line Encyclopedia (Broad Institute, Cambridge, MA, USA). After washing away unbound proteins, the cells were incubated with an Alexa Fluor 647-conjugated antibody, which recognizes the anti-albumin domain in the 02B05 BCMA trispecific antigen-binding protein. Cells were then analyzed by flow cytometry. As a negative control, cells were incubated with the trispecific protein targeting GFP. Cells expressing BCMA RNA and incubated with the BCMA trispecific protein had a significant shift associated with Alexa Fluor 647 staining compared to cells incubated with the GFP trispecific protein (as in Figures 5A, 5B, 5D, and 5E). However, cells lacking BCMA RNA yielded comparable Alexa Fluor 647 staining with the BCMA trispecific protein and the GFP trispecific protein (as seen in Figures 5C and 5F). Thus, this study demonstrated that a typical BCMA trispecific antigen binding protein was able to selectively bind to cells expressing BCMA.

[0192] Example 9 The ability of exemplary BCMA-targeted trispecific proteins, including the BCMA-binding proteins of the present disclosure, to mediate T-cell killing of BCMA-expressing cancer cells

[0193] An exemplary BCMA trispecific protein, 02B05 (SEQ ID NO:383), including the BCMA binding proteins of the present disclosure, was tested for its ability to induce T cells to kill BCMA-expressing cells in the presence or absence of human serum albumin (HSA) using a standard TDCC assay. Because the exemplary BCMA trispecific protein contains an anti-albumin domain, this experiment was performed to confirm that binding to albumin does not prevent the BCMA trispecific antigen binding protein from inducing T cells to kill BCMA-expressing cells. Five BCMA-expressing cell lines were tested: EJM, Jeko, OPM2, MOLP8, and NCI-H929. Representative data for the EJM cell experiment are shown in Figure 6. It was observed that EJM cell viability decreased with increasing amounts of the exemplary 02B05 BCMA trispecific antigen binding protein in the presence or absence of human serum albumin (HSA), while the control GFP trispecific protein had no effect on cell viability. In the presence of albumin, higher concentrations of BCMA trispecific protein were required to reduce EJM cell viability. EC1000- ... 50 Values ​​are provided in Table 5. In all five cell lines, the exemplary 02B05 BCMA trispecific antigen binding protein enabled T cells to kill target cells in the presence of HSA.

[0194] [Table 5]

[0195] Example 10 The ability of exemplary BCMA-targeted trispecific proteins, including the BCMA-binding proteins of the present disclosure, to mediate T cell killing of BCMA-expressing cancer cells using a smaller ratio of target cells to effector cells.

[0196] In a standard TDCC assay (as described in Example 1), a ratio of 1 target cell (EJM or OPM2 cells) to 10 effector cells (T cells) is used in a 48-hour assay. In this experiment, the ability of an exemplary BCMA-targeted trispecific protein, 02B05 (SEQ ID NO:383), comprising an exemplary BCMA-binding protein of the present disclosure, to induce T cells to kill target cells using a smaller target-to-effector cell ratio was examined. It was expected that fewer effector cells would be observed when fewer effector cells were used. Two BCMA-expressing cell lines, EJM and OPM2, were tested using target-to-effector cell ratios of 1:1, 1:3, and 1:10, and the experiment was performed in the presence of 15 mg / ml HSA. GFP-targeted trispecific proteins were used as a negative control. Data from this experiment are shown in Figure 7 (TDCC assay with EJM cells) and Figure 8 (TDCC assay with OPM2 cells). As expected, nearly complete killing of target cells was observed with a target to effector cell ratio of 1:10. The amount of killing decreased with decreasing effector cells. EC 50 The values ​​are listed in Table 6 (n / d is the EC 50 When fewer effector cells are present, EC 50 Therefore, as expected, the TDCC activity of the BCMA trispecific protein was reduced by the reduction in the number of effector cells relative to the target cells.

[0197] [Table 6]

[0198] Example 11 The ability of exemplary BCMA-targeted trispecific proteins, including the BCMA-binding proteins of the present disclosure, to mediate T cell killing of BCMA-expressing cancer cells in a time course study using a smaller ratio of target cells to effector cells.

[0199] In a standard TDCC assay (Example 1), a ratio of 1 part target cells (OPM2) to 10 parts effector cells (T cells) is used for a 48-hour assay. In this experiment, a time course was performed using a 1:1 ratio of target cells (EJM cells) to effector cells (T cells). It was expected that a 1:1 ratio would result in target cell death with increasing time. TDCC assays were performed using EJM and a 1:1 ratio of target cells to effector cells, and experiments were performed in the presence of 15 mg / ml HSA. A GFP-targeted trispecific protein was used as a negative control. Target cell viability was measured on days 1, 2, 3, and 4 after incubation of target and effector cells at a 1:1 ratio in the presence of a typical 02B05 BCMA trispecific antigen-binding protein and 15 mg / ml HSA, or a GFP-targeted trispecific protein and 15 mg / ml HSA. While no target cell killing was observed on day 1, killing was observed at all other time points with the 02B05 BCMA trispecific antigen binding protein, with the amount of killing increasing over time (Figure 9). Target cell killing was not observed with the GFP-targeted trispecific protein. EC calculated for cell killing on each day. 50 The values ​​are given in Table 7 (n / d is the EC 50 The conclusion drawn from this study was that the typical 02B05 BCMA trispecific protein was able to induce T cell killing with a small number of effector cells, but more complete killing required more time.

[0200] [Table 7]

[0201] Example 12 Ability of exemplary BCMA-targeting trispecific proteins, including the BCMA-binding proteins of the present disclosure, to cause human T cells to kill BCMA-expressing cells

[0202] An exemplary BCMA trispecific protein, 02B05 (SEQ ID NO:383), including the BCMA binding proteins of the present disclosure, was tested for its ability to kill BCMA-expressing T cells from four different anonymous human donors in the presence of 15 mg / ml human serum albumin (HSA) using a standard TDCC assay as described in Example 1. The BCMA-expressing cell lines were EJM, NCI-H929, OPM2, and RPMI8226. As negative controls, two cell lines lacking BCMA expression, OVCAR8 and NCI-H510A, were also tested in the TDCC assay. A control GFP-targeted trispecific protein was also used as a negative control. In the four BCMA-expressing cell lines and all four T cell donors, cell viability decreased with increasing amounts of BCMA trispecific protein, but not with GFP trispecific protein (Figures 10, 11, 12, and 13). EC for cell killing 50 Values ​​are provided in Table 8. The exemplary 02B05 BCMA trispecific antigen binding protein did not induce killing of cell lines lacking BCMA expression (Figures 14 and 15). It can therefore be inferred that the exemplary 02B05 BCMA trispecific antigen binding protein was capable of enabling T cells from multiple donors to kill a variety of BCMA-expressing cell lines.

[0203] [Table 8]

[0204] Example 13 Ability of exemplary BCMA-targeting trispecific proteins, including BCMA-binding proteins of the present disclosure, to cause cynomolgus monkey T cells to kill BCMA-expressing cells

[0205] An exemplary BCMA-targeting trispecific protein, 02B05 (SEQ ID NO:383), comprising a BCMA-binding protein of the present disclosure, was tested for its ability to induce BCMA-expressing T cells from cynomolgus monkeys to kill BCMA-expressing cells in the presence of 15 mg / ml human serum albumin (HSA). Experimental conditions were the same as those described in Example 1, except that peripheral blood mononuclear cells (PBMCs) from cynomolgus monkeys were used as the source of T cells. Two BCMA-expressing cell lines, RPMI8226 and NCI-H929, were tested. As shown in Figures 16 and 17, the BCMA trispecific protein was able to induce T cells present in cynomolgus monkey PBMCs to kill the two BCMA-expressing cell lines. EC for cell killing 50 The values ​​are listed in Table 9. The GFP trispecific protein did not affect the viability of BCMA-expressing cells. Thus, a BCMA-expressing trispecific protein capable of binding to cynomolgus CD3ε (as shown in Example 6) can enable cynomolgus T cells to kill cells expressing human BCMA.

[0206] [Table 9]

[0207] Example 14 Exemplary BCMA-targeted trispecific proteins, including BCMA-binding proteins of the present disclosure, in mediating induction of T cell activation

[0208] An exemplary BCMA-targeting trispecific protein, 02B05 (SEQ ID NO:383), including the BCMA-binding protein of the present disclosure, was tested for its ability to activate T cells in the presence of BCMA-expressing cells. The BCMA-expressing cell lines were EJM, OPM2, and RPMI8226. Two cell lines lacking BCMA expression, OVCAR8 and NCI-H510A, were also included as negative controls. T cells were obtained from four different anonymous human donors. The assay was set up using standard TDCC assay conditions as described in Example 1, except that the assay was adapted to a 96-well format and performed in the presence of 15 mg / ml HSA. Forty-eight hours after the assay, T cell activation was assessed using flow cytometry to measure the expression of T cell activation biomarkers CD25 and CD69 on the T cell surface. With the increase in the exemplary 02B05 BCMA trispecific antigen-binding protein, increased expression of CD69 and CD25 was observed on T cells upon co-culture with BCMA-expressing cells (as shown in Figures 18-23). ​​Therefore, since little to no activation was observed with the control GFP trispecific (as shown in Figures 18-23) or target cells lacking BCMA expression (as shown in Figures 24-27), the observed interaction was dependent on interaction with the BCMA-binding sequence within the exemplary BCMA-targeted trispecific protein. Therefore, the exemplary BCMA-targeted trispecific protein activated T cells in co-cultures containing BCMA-expressing cells. Additional data support this conclusion. For example, expression of the cytokine, TNFα, was measured in media collected from co-cultures of T cells and BCMA-expressing target cells treated with increasing concentrations of the exemplary BCMA-targeted trispecific protein or the negative control GFP trispecific. Co-cultures were set up using standard TDCC assay conditions (as described in Example 1) supplemented with 15 mg / ml HSA. TNFα was measured using an electrochemiluminescence assay (Meso Scale Discovery).Robust induction of TNFα expression was observed with an exemplary BCMA-targeted trispecific protein, 02B05 (SEQ ID NO:383), which includes a BCMA-binding protein of the present disclosure, but not with a GFP trispecific protein ( FIG. 28 ). This result further confirms that an exemplary BCMA-targeted trispecific protein activated T cells in co-cultures containing BCMA-expressing cells.

[0209] Example 15 Pharmacokinetics of exemplary BCMA-targeted trispecific proteins, including BCMA-binding proteins of the present disclosure

[0210] Cynomolgus monkeys were administered a single intravenous dose of 0.01 mg / kg, 0.1 mg / kg, or 1 mg / kg of an exemplary BCMA-targeted trispecific protein (02B05) (SEQ ID NO:383) comprising a BCMA-binding protein of the present disclosure. Two animals were included per treatment group. After administration, serum samples were collected and analyzed by two different electrochemiluminescence assays. One assay used biotinylated CD3ε as the capture reagent and detected by sulfo-tagged BCMA (referred to as the functional assay). The other assay used a biotinylated antibody recognizing the anti-albumin domain in the exemplary BCMA-targeted trispecific protein 02B05 (SEQ ID NO:383) comprising a BCMA-binding protein of the present disclosure as the capture reagent, and a sulfo-tagged antibody (i.e., an anti-idiotypic antibody) recognizing the anti-CD3 binding domain in the exemplary BCMA-targeted trispecific protein comprising a BCMA-binding protein of the present disclosure as the detection reagent. The results of the electrochemiluminescence assay are plotted in Figure 31. As can be seen in Figure 31, the exemplary BCMA-targeted trispecific protein was detected in cynomolgus monkey serum samples even 504 hours after administration. The exemplary BCMA-targeted trispecific protein was identified by both sulfo-tagged BCMA (line labeled using the term "functional" in Figure 31) and an anti-idiotypic antibody (line labeled using the term "anti-idiotypic" in Figure 31).

[0211] To confirm that the exemplary BCMA-targeted trispecific protein retained the ability to induce T cells to kill BCMA-expressing EJM cells, serum samples at 168 hours after in vivo administration were tested in a TDCC assay (as described in Example 1) in the presence of 16.7% serum from cynomolgus monkeys that had not been exposed to the BCMA-targeted trispecific protein, and the exemplary BCMA-targeted trispecific protein was titrated using protein concentrations determined using an electrochemiluminescence assay (as shown in Figure 32). Freshly diluted exemplary BCMA-targeted trispecific protein 02B05 (SEQ ID NO:383), which comprises a BCMA-binding protein of the present disclosure, was compared to the BCMA trispecific protein collected from the test cynomolgus monkeys at 168 hours. GFP trispecific protein was included as a negative control. This study demonstrated that the representative BCMA-targeted trispecific protein collected from the serum of test cynomolgus monkeys had the same activity as the freshly diluted protein, and that the protein in the serum samples retained the ability to induce T cells to kill BCMA-expressing EJM cells.

[0212] While preferred embodiments of the present invention have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It is understood that various alternatives to the embodiments of the invention described herein may be utilized in practicing the invention. The following claims define the scope of the invention, and it is intended that methods and structures within the scope of these claims and their equivalents be covered thereby.

[0213] [Table 10-1]

[0214] [Table 10-2]

[0215] Table 10-3

[0216] Table 10-4

[0217] Table 10-5

[0218] Table 10-6

[0219] Table 10-7

[0220] Table 10-8

[0221] Table 10-9

[0222] Table 10-10

[0223] Table 10-11

[0224] Table 10-12

[0225] Table 10-13

[0226] Table 10-14

[0227] Table 10-15

[0228] Table 10-16

[0229] Table 10-17

[0230] Table 10-18

Claims

1. A polynucleotide encoding a single domain B-cell maturation agent (BCMA) binding protein comprising complementarity determining regions CDR1, CDR2, and CDR3, where: (a) the CDR1 comprises the amino acid sequence of SEQ ID NO: 5, 15, 18, 19, 22, 29, 34, 35, 43, 46, 76, or 95; (b) the CDR2 comprises the amino acid sequence of SEQ ID NO: 118, 121, 122, 125, 126, 129, 133, 137, 147, 156, 164, 173, 174, 190, or 203; (c) the CDR3 comprises the amino acid sequence set forth in SEQ ID NO: 304, and the single domain B-cell maturation agent (BCMA) binding protein is 80% to 99% identical to the sequence set forth in SEQ ID NO: 472; Polynucleotide.

2. The single domain B cell maturation agent (BCMA) binding protein has the following formula: f1-r1-f2-r2-f3-r3-f4 Including, wherein r1 is CDR1, r2 is CDR2, and r3 is CDR3; 2. The polynucleotide of claim 1, wherein f1, f2, f3, and f4 are framework regions.

3. 2. The polynucleotide of claim 1, wherein the single domain B-cell maturation agent (BCMA) binding protein comprises the amino acid sequence set forth as SEQ ID NO: 374, 383, 402, 403, 406, 411, 412, or 416.

4. 4. The polynucleotide of claim 3, wherein the single domain B-cell maturation agent (BCMA) binding protein comprises the amino acid sequence set forth as SEQ ID NO:

383.

5. The polynucleotide of claim 2, wherein f1 comprises SEQ ID NO: 461 or 462.

6. The polynucleotide of claim 2, wherein f2 comprises SEQ ID NO:

463.

7. The polynucleotide of claim 2, wherein f3 comprises SEQ ID NO: 464 or 465.

8. The polynucleotide of claim 2, wherein f4 comprises SEQ ID NO: 466 or 467.

9. 2. The polynucleotide of claim 1, wherein the single domain B-cell maturation agent (BCMA) binding protein has an elimination half-life of at least 12 hours when administered to a subject.

10. The polynucleotide of claim 1 , wherein the single domain B-cell maturation agent (BCMA) binding protein is humanized or affinity matured.

11. The polynucleotide of claim 1 , wherein the single domain B-cell maturation agent (BCMA) binding protein further comprises an Fc domain.

12. 2. The polynucleotide of claim 1, wherein the single domain B-cell maturation agent (BCMA) binding protein further comprises an anti-cancer agent.

13. The polynucleotide of claim 12 , wherein the anti-cancer agent binds to the single domain B-cell maturation agent (BCMA) binding protein.

14. 2. The polynucleotide of claim 1, wherein the single domain B-cell maturation agent (BCMA) binding protein comprises a sequence that is at least 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 374, 383, 402, 403, 406, 411, 412, and 416.

15. 15. The polynucleotide of claim 14, wherein the single domain B-cell maturation agent (BCMA) binding protein comprises a sequence that is at least 90% identical to SEQ ID NO:

383.

16. 2. The polynucleotide of claim 1, wherein the single domain B-cell maturation agent (BCMA) binding protein comprises a sequence that is at least 95% identical to a sequence selected from the group consisting of SEQ ID NOs: 374, 383, 402, 403, 406, 411, 412, and 416.

17. 17. The polynucleotide of claim 16, wherein the single domain B-cell maturation agent (BCMA) binding protein comprises a sequence that is at least 95% identical to SEQ ID NO:

383.

18. 2. The polynucleotide of claim 1, wherein the single domain B-cell maturation agent (BCMA) binding protein recognizes an epitope within the human BCMA protein comprising the sequence set forth in SEQ ID NO:

468.

19. A polynucleotide encoding a single domain B-cell maturation agent (BCMA) binding protein, said single domain B-cell maturation agent (BCMA) binding protein comprising complementarity determining regions CDR1, CDR2, and CDR3; wherein the CDR1 comprises the amino acid sequence of SEQ ID NO: 76, the CDR2 comprises the amino acid sequence of SEQ ID NO: 190, the CDR3 comprises the amino acid sequence of SEQ ID NO: 304, and the BCMA binding protein is 80% to 99% identical to the amino acid sequence set forth in SEQ ID NO:

472.

20. 1. A polynucleotide encoding a single domain B-cell maturation agent (BCMA) binding protein, the single domain B-cell maturation agent (BCMA) binding protein comprising: (i) CDR1 comprising the sequence of SEQ ID NO: 76, CDR2 comprising the sequence of SEQ ID NO: 190, and CDR3 comprising the sequence of SEQ ID NO: 304; (ii) CDR1 comprising the sequence of SEQ ID NO: 114, CDR2 comprising the sequence of SEQ ID NO: 163, and CDR3 comprising the sequence of SEQ ID NO: 304; (iii) CDR1 comprising the sequence of SEQ ID NO: 115, CDR2 comprising the sequence of SEQ ID NO: 163, and CDR3 comprising the sequence of SEQ ID NO: 304; (iv) a CDR1 comprising the sequence of SEQ ID NO: 116, a CDR2 comprising the sequence of SEQ ID NO: 174, and a CDR3 comprising the sequence of SEQ ID NO: 304; or (v) A polynucleotide comprising a CDR1 comprising the sequence of SEQ ID NO: 117, a CDR2 comprising the sequence of SEQ ID NO: 174, and a CDR3 comprising the sequence of SEQ ID NO:

304.

21. The polynucleotide of claim 20, wherein the single domain B-cell maturation agent (BCMA) binding protein comprises a CDR1 comprising the sequence of SEQ ID NO: 76, a CDR2 comprising the sequence of SEQ ID NO: 190, and a CDR3 comprising the sequence of SEQ ID NO:

304.

22. 2. The polynucleotide of claim 1, wherein the single domain B-cell maturation agent (BCMA) binding protein is a component of a multispecific binding protein.

23. 23. The polynucleotide of claim 22, wherein the multispecific binding protein is a BCMA-targeted trispecific protein comprising: (A) the single domain B-cell maturation agent (BCMA) binding protein; (B) a human serum albumin (HSA) binding domain; and (C) a CD3 binding domain.

24. 23. The polynucleotide of claim 22, wherein the single domain B-cell maturation agent (BCMA) binding protein comprises a sequence that is at least 90% identical to SEQ ID NO:

383.

25. The BCMA-targeted trispecific protein is ２ 24. The polynucleotide of claim 23, having a domain order of N-(A)-(B)-(C)-COOH.

26. 26. The polynucleotide of claim 25, wherein the single domain B-cell maturation agent (BCMA) binding protein comprises a sequence that is at least 90% identical to SEQ ID NO:

383.

27. A vector comprising the polynucleotide according to any one of claims 1 to 26.

28. A host cell comprising the polynucleotide of any one of claims 1 to 26.

29. A host cell comprising the vector of claim 27.

30. 30. A method for producing a single domain B-cell maturation agent (BCMA) binding protein, comprising culturing the host cell of claim 28 or 29 under conditions suitable for producing the single domain B-cell maturation agent (BCMA) binding protein.

31. 31. The method of producing a single domain B-cell maturation agent (BCMA) binding protein of claim 30, further comprising purifying the single domain B-cell maturation agent (BCMA) binding protein.

32. A single domain B-cell maturation agent (BCMA) binding protein produced by the method for producing a single domain B-cell maturation agent (BCMA) binding protein according to claim 30 or 31.

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