BAFF-r bispecific t-cell engager antibody

Abstract

To provide new therapeutic antibodies against an alternative specific target on malignant cells, and a method of treating cancer and an autoimmune disease.SOLUTION: Provided herein are recombinant proteins (e.g., a bispecific antibody) capable of binding BAFF-R. The recombinant proteins (e.g., bispecific antibody) provided herein are, inter alia, useful for the treatment of cancer and autoimmune disease.SELECTED DRAWING: Figure 4

Description

[Background technology]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 782,317, filed December 19, 2018, which is incorporated by reference in its entirety and for all purposes.

[0002] AN "Sequence Listing", Table, or Computer Program Listing Appendix Submitted as an ASCII File The sequence listing set forth in file 048440-715001WO_SEQUENCE_LISTING_ST25, 45,056 bytes, machine format IBM-PC, MS Windows Operating System, created on Dec. 12, 2019, is incorporated herein by reference.

[0003] Antibody therapy is one of the most successful immunotherapies that can be used in the clinic to treat hematological malignancies. A typical case is rituximab, which targets CD20 and elicits cytotoxic effects on B-cell lymphoma. However, a major concern with rituximab is the emergence of rituximab resistance, which is believed to be due to downregulation of CD20, preventing the antibody from binding to target cells. Therefore, the art is in need of new therapeutic antibodies against other specific targets on malignant cells. Provided herein are compositions of BAFF-R bispecific antibodies and methods of using them that address these and other problems in the art. Summary of the Invention

[0004] In one aspect, there is provided a recombinant protein comprising (i) a first antibody region capable of binding to an effector cell ligand, and (ii) (a) a second antibody region comprising a light chain variable domain and a heavy chain variable domain. The light chain variable domain comprises CDR L1 as set forth in SEQ ID NO: 1, CDR L2 as set forth in SEQ ID NO: 2, and CDR L3 as set forth in SEQ ID NO: 3. The heavy chain variable domain comprises CDR H1 as set forth in SEQ ID NO: 4, CDR H2 as set forth in SEQ ID NO: 5, and CDR H3 as set forth in SEQ ID NO: 6.

[0005] In one aspect, there is provided a recombinant protein comprising (i) a first antibody region capable of binding to an effector cell ligand, and (ii) (a) a second antibody region comprising a light chain variable domain and a heavy chain variable domain. The light chain variable domain comprises CDR L1 as set forth in SEQ ID NO: 38, CDR L2 as set forth in SEQ ID NO: 39, and CDR L3 as set forth in SEQ ID NO: 40. The heavy chain variable domain comprises CDR H1 as set forth in SEQ ID NO: 41, CDR H2 as set forth in SEQ ID NO: 42, and CDR H3 as set forth in SEQ ID NO: 43.

[0006] In one aspect, a pharmaceutical composition is provided that comprises a therapeutically effective amount of a recombinant protein provided herein, including embodiments thereof, and a pharma- ceutically acceptable excipient.

[0007] In one aspect, there is provided a method of treating cancer in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a recombinant protein described herein, including embodiments thereof, thereby treating cancer in the subject.

[0008] In another aspect, there is provided a method of treating an autoimmune disease in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a recombinant protein described herein, including embodiments thereof, thereby treating the autoimmune disease in the subject. [Brief description of the drawings]

[0009] [Figure 1A] Generation of BAFF-R Bispecific Antibody (BAFF-R BiTE, a recombinant protein presented herein including embodiments thereof) by knob-hole technology. A schematic diagram of BAFF-R BiTE is shown. [Figure 1B] Generation of BAFF-R bispecific antibodies (BAFF-R BiTEs, recombinant proteins as presented herein, including embodiments thereof) by knob-hole technology. Reducing and non-reducing gel conditions for BAFF-R BiTEs (H90Bi) are shown. Controls include control / irrelevant BiTEs (Cont.Bi, 4-4Bi) and humanized BAFF-R antibodies (e.g., H90 Ab, also referred to herein as "humanized C90" and, depending on the framework sequence, "humanized C90-1", "humanized C90-2", "humanized C90-3", "C90", "C90-1", "C90-2", or "C90-3"). [Diagram 2] Binding specificity of bispecific antibodies. FACS histograms of BAFF-R / CD3 bispecific antibody (H90 BiTE) binding wild-type mouse fibroblast L cells, modified BAFF-R expressing L cells (B2D L cells), and T cells isolated from a healthy donor. [Diagram 3] Specific cytotoxicity of bispecific antibodies against BAFF-R expressing L cells. The plot shows the specific cytotoxicity percentage calculated from chromium release assay. BAFF-R / CD3 bispecific antibody (H90BiTE) was incubated with chromium-labeled target wild type (left) or BAFF-R expressing L cells (right) together with effector CD8 T cells isolated from a single healthy donor. The ratio of effector cells to isolated CD8 T cells was 10:1. The incubation time was 4 h. [Figure 4] Cytotoxicity of bispecific antibodies against malignant B cell lines. The plot shows the specific cytotoxicity percentage calculated from chromium release assay against various malignant B cell lines as indicated. The ratio of effector cells to isolated CD8 T cells was 10:1. The incubation time was 4 hours. [Diagram 5]Dose-dependent cytotoxicity of bispecific antibodies. The plot shows the specific cytotoxicity percentage calculated from chromium release assay against JeKo-1 mantle cell lymphoma and isolated normal B cells. The ratio of effector cells to isolated CD8 T cells was 10:1. The incubation time was 4 hours. [Figure 6] Timeline of the treatment schedule for tumor challenge and treatment with BAFF-R BiTE in NSG mice. The schematic shows the treatment schedule for the Z-138 MCL tumor model with dosing time points indicated on the horizontal line. Bioluminescence imaging was performed weekly and mice were observed up to 90 days after tumor challenge. [Figure 7] Z-138 model treated with BAFF-R BiTE. Bioluminescence images of groups of NSG mice (n=5 / group) following intravenous (IV) tumor challenge (5x104 cells / mouse) with Z-138 MCL on day 0. Experimental groups (BAFF-R BiTE 300μg) received 300μg BAFF-R BiTE + 5x106 T cells. Control groups received 5x106 T cells from the same donor or saline (PBS). [Figure 8A-1] FACS plots of BAFF-R BiTE antibody staining show binding to parental L cells (FIG. 8A) compared to BAFF-R positive L cells (B2D) (FIG. 8B) or donor T cells (FIG. 8C). [Figure 8A-2] FACS plots of BAFF-R BiTE antibody staining show binding to parental L cells (FIG. 8A) compared to BAFF-R positive L cells (B2D) (FIG. 8B) or donor T cells (FIG. 8C). [Figure 8B-1] FACS plots of BAFF-R BiTE antibody staining show binding to parental L cells (FIG. 8A) compared to BAFF-R positive L cells (B2D) (FIG. 8B) or donor T cells (FIG. 8C). [Figure 8B-2] FACS plots of BAFF-R BiTE antibody staining show binding to parental L cells (FIG. 8A) compared to BAFF-R positive L cells (B2D) (FIG. 8B) or donor T cells (FIG. 8C). [Figure 8C-1] FACS plots of BAFF-R BiTE antibody staining show binding to parental L cells (FIG. 8A) compared to BAFF-R positive L cells (B2D) (FIG. 8B) or donor T cells (FIG. 8C). In FIGS. 8A-C, staining includes secondary antibody and BAFF-R humanized antibody as a control for L cells, and a combination of secondary antibody and CD3 antibody as a control for T cells. [Figure 8C-2] FACS plots of BAFF-R BiTE antibody staining show binding to parental L cells (FIG. 8A) compared to BAFF-R positive L cells (B2D) (FIG. 8B) or donor T cells (FIG. 8C). In FIGS. 8A-C, staining includes secondary antibody and BAFF-R humanized antibody as a control for L cells, and a combination of secondary antibody and CD3 antibody as a control for T cells. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] I. Definition While various embodiments and aspects of the present invention have been shown and described herein, it will be apparent to those skilled in the art that such embodiments and aspects are provided by way of example only. Numerous variations, changes, and substitutions will occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments described herein may be employed in the practice of the invention.

[0011] The section headings used herein are for organizational purposes only and should not be construed as limiting the subject matter described. All documents or portions of documents cited in this application (including, but not limited to, patents, patent applications, articles, books, manuals, papers) are expressly incorporated by reference in their entirety for any purpose.

[0012] "Nucleic acid" refers to nucleotides (e.g., deoxyribonucleotides or ribonucleotides) and polymers thereof in either single-, double-, or multi-stranded form, or their complements, or nucleosides (e.g., deoxyribonucleosides or ribonucleosides). In some embodiments, "nucleic acid" does not include nucleosides. The terms "polynucleotide," "oligonucleotide," "oligo," and the like refer to a linear sequence of nucleotides in the normal, customary sense. The term "nucleoside" refers to a glycosylamine containing a nucleobase and a five-carbon sugar (ribose or deoxyribose) in the normal, customary sense. Non-limiting examples of nucleosides include cytidine, uridine, adenosine, guanosine, thymidine, and inosine. The term "nucleotide" refers to a unit, i.e., a monomer, of a polynucleotide in the normal, customary sense. A nucleotide can be a ribonucleotide, a deoxyribonucleotide, or a modified form thereof. Examples of polynucleotides contemplated herein include single-stranded and double-stranded DNA, single-stranded and double-stranded RNA, and hybrid molecules having a mixture of single-stranded and double-stranded DNA and RNA. Examples of nucleic acids, e.g., polynucleotides, contemplated herein include any type of RNA, e.g., mRNA, siRNA, miRNA, and guide RNA, as well as any type of DNA, genomic DNA, plasmid DNA, and minicircle DNA, and any fragments thereof. The term "double-stranded" in the context of polynucleotides refers to double helicity in the usual and customary sense. Nucleic acids can be linear or branched. For example, nucleic acids can be linear chains of nucleotides, or branched chains, e.g., including one or more arms or branches of nucleotides. Optionally, branched nucleic acids are repeatedly branched to form higher order structures, such as dendrimers.

[0013] The term also encompasses nucleic acids that contain known nucleotide analogs or modified backbone residues or backbone linkages, which are synthetic, naturally occurring, and non-naturally occurring, and have similar binding properties as the related nucleic acids and are metabolized in the same manner as the related nucleotides. Examples of such analogs include, but are not limited to, for example, phosphoramidates, phosphorodiamidates, phosphorothioates (also known as phosphothioates, which replace the oxygen in the phosphate with a double bond sulfur), phosphorodithioates, phosphonocarboxylic acids, phosphonocarboxylates, phosphonoacetic acids, phosphonoformic acids, methylphosphonates, boron phosphonates, or O-methyl phosphoramidite linkages (see Eckstein, Oligonucleotides and Analogues: A Practical Approach, Oxford University Press), as well as modifications to nucleotide bases such as 5-methylcytidine or pseudouridine, and phosphodiester derivatives that include peptide nucleic acid backbones and linkages. Other analog nucleic acids include those with cationic backbones, non-ionic backbones, modified sugars, and non-ribose backbones (e.g., phosphorodiamidate morpholino oligos or locked nucleic acids (LNAs) as known in the art), including those described in U.S. Pat. Nos. 5,235,033 and 5,034,506, and chapters 6 and 7 of ASC Symposium Series 580, Carbohydrate Modifications in Antisense Research, Sanghui & Cook, eds. Nucleic acids containing one or more carbocyclic sugars are also included within one definition of nucleic acid. Modifications of the ribose-phosphate backbone can be made for a variety of reasons, such as to increase the stability and half-life of such molecules in physiological environments or as probes on biochips. Mixtures of naturally occurring nucleic acids and analogs can be made, or mixtures of different nucleic acid analogs and mixtures of naturally occurring nucleic acids and analogs can be made.In some embodiments, the internucleotide linkages in the DNA are phosphodiester, phosphodiester derivatives, or a combination of both.

[0014] The term "amino acid" refers to naturally occurring and synthetic amino acids, as well as amino acid analogs and amino acid mimetics that function similarly to naturally occurring amino acids. Naturally occurring amino acids are those encoded by the genetic code, as well as those that are later modified (e.g., hydroxyproline, γ-carboxyglutamate, and O-phosphoserine). Amino acid analogs refer to compounds that have the same basic chemical structure as a naturally occurring amino acid, i.e., an alpha carbon that is attached to a hydrogen, a carboxyl group, an amino group, and an R group, such as homoserine, norleucine, methionine sulfoxide, and methionine methylsulfonium. Such analogs have modified R groups (e.g., norleucine) or modified peptide backbones, but retain the same basic chemical structure as a naturally occurring amino acid. Amino acid mimetics refer to compounds that have a structure that is different from the general chemical structure of an amino acid, but that function similarly to a naturally occurring amino acid. The terms "non-naturally occurring amino acid" and "unnatural amino acid" refer to amino acid analogs, synthetic amino acids, and amino acid mimetics that are not found in nature.

[0015] Amino acids may be referred to herein by either their commonly known three letter symbols or by the one-letter symbols recommended by the IUPAC-IUB Biochemical Nomenclature Commission. Similarly, nucleotides may be referred to by their commonly accepted single-letter codes.

[0016] "Conservatively modified variants" applies to both amino acid and nucleic acid sequences. With respect to a particular nucleic acid sequence, "conservatively modified variants" refers to nucleic acids that code for the same or essentially the same amino acid sequence. Due to the degeneracy of the genetic code, many nucleic acid sequences code for any given protein. For example, the codons GCA, GCC, GCG, and GCU all code for the amino acid alanine. Thus, at every position where alanine is specified by a codon, the codon can be altered to any of the corresponding codons described without altering the encoded polypeptide. Such nucleic acid variations are "silent variations," which are one type of conservatively modified variation. Every nucleic acid sequence herein that codes for a polypeptide also represents every possible silent variation of the nucleic acid. Those skilled in the art will understand that each codon in a nucleic acid (except AUG, which is usually the only codon for methionine, and TGG, which is usually the only codon for tryptophan) can be modified to produce a functionally identical molecule. Thus, every silent variation of a nucleic acid that codes for a polypeptide is implicit in each described sequence.

[0017] With respect to amino acid sequences, one of skill in the art will understand that individual substitutions, deletions, or additions to a nucleic acid, peptide, polypeptide, or protein sequence that alter, add, or delete a single amino acid or a small number of amino acids in the encoded sequence are "conservatively modified variants," which alterations result in the substitution of a chemically similar amino acid. Conservative substitution tables providing functionally similar amino acids are well known in the art. Such conservatively modified variants are in addition to, and do not exclude, polymorphic variants, interspecies homologs, and alleles of the present invention.

[0018] Each of the following eight groups contains amino acids that are conservative substitutions for one another: 1) Alanine (A), Glycine (G) 2) Aspartic acid (D), glutamic acid (E) 3) Asparagine (N), Glutamine (Q) 4) Arginine (R), Lysine (K) 5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V) 6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W) 7) Serine (S), Threonine (T) 8) Cysteine ​​(C), Methionine (M) (See, e.g., Creighton, Proteins (1984)).

[0019] "Percentage of sequence identity" is determined by comparing two optimally aligned sequences over a comparison window, where the portion of the polynucleotide or polypeptide sequence in the comparison window may contain additions or deletions (i.e., gaps) as compared to a reference sequence for optimal alignment of the two sequences (which does not contain additions or deletions). This percentage is calculated by determining the number of positions where an identical nucleic acid base or amino acid residue is present in both sequences to generate a number of matched positions, dividing the number of matched positions by the total number of positions in the comparison window, and multiplying the result by 100 to generate a percentage of sequence identity.

[0020] In the context of two or more nucleic acid or polypeptide sequences, the term "identical" or percentage "identity" refers to two or more sequences or subsequences that are identical or have a certain percentage of identical amino acid residues or nucleotides (i.e., 60% identity, optionally 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or 99% identity, for example, over the entire polypeptide sequence of the invention or over a particular region of an individual domain of a polypeptide of the invention) when compared and aligned for maximum correspondence over a comparison window, or when designated regions are evaluated according to one of the sequence comparison algorithms below or by manual alignment and visual inspection. Such sequences are then said to be "substantially identical." This definition also refers to the complement of a test sequence. Optionally, the identity exists over a region that is at least about 50 nucleotides in length, and more preferably over a region that is 100 to 500 or 1000 or more nucleotides in length. The present invention includes polypeptides that are substantially identical to any of SEQ ID NOs: 7 to 12 or 44 to 49.

[0021] When comparing sequences, typically, one sequence serves as a reference sequence, and test sequences are compared to it.When using sequence comparison algorithm, test sequences and reference sequences are input into computer, partial sequence coordinates are designated as necessary, and sequence algorithm program parameters are designated.Default program parameters can be used, or alternative parameters can be designated.The sequence comparison algorithm then calculates the percent sequence identity of test sequences compared to reference sequences based on program parameters.

[0022] A "comparison window" as used herein includes, for example, a reference to a full length sequence or any segment of a number of consecutive positions selected from the group consisting of 20 to 600, about 50 to about 200, or about 100 to about 150 amino acids or nucleotides, in which the same number of consecutive positions of a sequence can be compared with a reference sequence after optimally aligning the two sequences. Methods of sequence alignment for comparison are well known in the art. Optimal alignment of sequences for comparison can be performed, for example, by the local homology algorithm of Smith and Waterman (1970) Adv. Appl. Math. 2:482c, the homology alignment algorithm of Needleman and Wunsch (1970) J. Mol. Biol. 48:443, the search for similarity algorithm of Pearson and Lipman (1988) Proc. Nat'l. Acad. Sci. USA 85:2444, computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Dr., Madison, Wis.), or by manual alignment and visual inspection (see, for example, Ausubel et al., Current Protocols in Molecular Biology (1995 supplement)).

[0023] Examples of suitable algorithms for determining percent sequence identity and sequence similarity are the BLAST and BLAST 2.0 algorithms, which are described in Altschul et al. (1977) Nuc. Acids Res. 25:3389-3402, and Altschul et al. (1990) J. Mol. Biol. 215:403-410, respectively. Software for performing BLAST analyses is publicly available from the National Center for Biotechnology Information (http: / / www.ncbi.nlm.nih.gov / ). This algorithm involves first identifying high-scoring sequence pairs (HSPs) by identifying short words of length W in a query sequence that match or satisfy a certain positive threshold score T when aligned with words of the same length in a database sequence. T is referred to as the neighborhood word score threshold (Altschul et al., supra). These initial neighborhood word hits act as seeds for initiating searches to find longer HSPs containing them. The word hits are extended in both directions along each sequence for as far as the cumulative alignment score can be increased. Cumulative scores are calculated using, for nucleotide sequences, the parameters M (reward score for a pair of matching residues, always >0) and N (penalty score for mismatching residues, always <0). For amino acid sequences, a scoring matrix is ​​used to calculate the cumulative score. Extension of the word hits in each direction is stopped when the cumulative alignment score falls by a quantity X from the highest achieved value, when the cumulative score becomes zero or less due to the accumulation of one or more negatively scoring residue alignments, or when the end of either sequence is reached. The BLAST algorithm parameters W, T, and X determine the sensitivity and speed of the alignment. The BLASTN program (for nucleotide sequences) uses as defaults a wordlength (W) of 11, an expectation (E) of 10, M=5, N=-4, and a comparison of both strands.For amino acid sequences, the BLASTP program uses as defaults a wordlength of 3, an expectation (E) of 10, and the BLOSUM62 scoring matrix (see Henikoff and Henikoff (1989) Proc. Natl. Acad. Sci. USA 89:10915), alignment (B) of 50, expectation (E) of 10, M=5, N=-4, and a comparison of both strands.

[0024] The BLAST algorithm also performs a statistical analysis of the similarity between two sequences (see, e.g., Karlin and Altschul (1993) Proc. Natl. Acad. Sci. USA 90:5873-5787). One measure of similarity provided by the BLAST algorithm is the smallest sum probability (P(N)), which provides an indication of the probability that a match between two nucleotide or amino acid sequences would occur by chance. For example, a nucleic acid is considered to be similar to a reference sequence if the smallest sum probability in the comparison of the test nucleic acid to the reference nucleic acid is less than about 0.2, more preferably less than about 0.01, and most preferably less than about 0.001.

[0025] An indication that two nucleic acid sequences or polypeptides are substantially identical is that the polypeptide encoded by the first nucleic acid immunologically cross-reacts with an antibody against the polypeptide encoded by the second nucleic acid, as described below. Thus, a polypeptide is typically substantially identical to a second polypeptide, for example, when the two peptides differ only by conservative substitutions. Another indication that two nucleic acid sequences are substantially identical is that the two molecules or their complements hybridize to each other under stringent conditions, as described below. Yet another indication that two nucleic acid sequences are substantially identical is that the same primers can be used to amplify the sequences.

[0026] An amino acid residue in an antibody "corresponds" to a particular residue if it occupies the same essential structural position as that particular residue in the antibody. For example, a selected residue of a comparative antibody corresponds to position 48 (according to the Kabat numbering system described herein) of an antibody provided herein if the selected residue occupies the same essential spatial or structural relationship as Kabat position 48 as assessed using methods applicable in the art. For example, the comparative antibody can be aligned with the antibody provided herein for maximum sequence homology, and the position of the aligned comparative antibody that matches at Kabat position 48 can be determined as corresponding thereto. Alternatively, instead of (or in addition to) the primary sequence alignment described above, a three-dimensional structural alignment can be used, for example, the structure of the comparative antibody is aligned with the antibody provided herein for maximum correspondence, and the overall structures are compared. In this case, the amino acid that occupies the same essential position as Kabat position 48 in the structural model can be said to correspond.

[0027] The terms "polypeptide," "peptide," and "protein" are used interchangeably herein to refer to a polymer of amino acid residues, which may optionally be linked to moieties not composed of amino acids. The term applies to amino acid polymers in which one or more amino acid residues are artificial chemical mimetics of a corresponding naturally occurring amino acid, as well as to naturally occurring and non-naturally occurring amino acid polymers. A "fusion protein" refers to a chimeric protein encoding two or more separate protein sequences that are recombinantly expressed as a single moiety. A "recombinant protein" refers to a protein that may result from the expression of recombinant DNA.

[0028] The terms "peptidyl" and "peptidyl moiety" refer to a monovalent peptide.

[0029] Antibodies are large, complex molecules (molecular weight about 150,000 Da, or about 1320 amino acids) with a complex internal structure. A natural antibody molecule contains two identical pairs of polypeptide chains, each pair having one light chain and one heavy chain. The light and heavy chains each consist of two regions: a variable ("V") region, which is responsible for binding the target antigen, and a constant ("C") region, which interacts with other components of the immune system. The variable regions of the light and heavy chains come together in three-dimensional space to form the variable region that binds to the antigen (e.g., a receptor on the surface of a cell). Within each variable region of the light or heavy chain are three short segments (average 10 amino acids in length) called complementarity determining regions ("CDRs"). The six CDRs of an antibody variable domain (three from the light chain and three from the heavy chain) fold together in three-dimensional space to form the actual antibody binding site (paratope), which docks to the target antigen (epitope). The positions and lengths of the CDRs are precisely defined by Kabat, E. et al., Sequences of Proteins of Immunological Interest, U.S. Department of Health and Human Services, 1983, 1987. The portions of the variable regions not included in the CDRs are called the framework ("FR"), which forms the surroundings for the CDRs.

[0030] An "antibody variant" as provided herein refers to a polypeptide that can bind to an antigen and comprises one or more structural domains of an antibody or fragment thereof (e.g., a light chain variable domain, a heavy chain variable domain). Non-limiting examples of antibody variants include single domain antibodies or nanobodies, monospecific Fabs, and the like. 2 , bispecific Fab 2 , trispecific Fab 3, monovalent IgG, scFv, bispecific diabody, trispecific triabody, scFv-Fc, minibody, IgNAR, V-NAR, hcIgG, VhH, or peptibody. As provided herein, "peptibody" refers to a peptide moiety attached (via a covalent or non-covalent linker) to the Fc domain of an antibody. Further non-limiting examples of antibody variants known in the art include antibodies produced by cartilaginous fish or camelids. A general description of antibodies and their variable regions from camelids, and methods of their production, isolation, and use can be found in references WO 97 / 49805 and WO 97 / 49805, which are incorporated herein by reference in their entirety for all purposes. Similarly, antibodies and their variable regions from cartilaginous fish, and methods of their production, isolation, and use can be found in WO 2005 / 118629, which are incorporated herein by reference in their entirety for all purposes.

[0031] The terms "bispecific T cell engager (BiTE)", "BiTe" or "bispecific antibody" as provided herein are used according to their conventional meanings known in the art to refer to a bispecific recombinant protein capable of binding, e.g., simultaneously, to two different antigens. In contrast to conventional monoclonal antibodies, BiTE antibodies consist of two independent antibody regions (e.g., two single chain variable fragments (scFvs)), each of which binds to a different antigen. One antibody region engages an effector cell (e.g., a T cell) by binding to an effector cell-specific antigen (e.g., a CD3 molecule), and the other antibody region binds to a target cell (e.g., a cancer cell or an autoimmune reactive cell) via a cell surface antigen (e.g., BAFF-R) expressed by the target cell. Binding of BiTE to two antigens results in the binding of the effector cell (e.g., a T cell) to the target cell (e.g., a tumor cell) and activation of the effector cell (e.g., a T cell) via effector cell-specific antigen signaling (e.g., CD3 signaling). Activated effector cells (eg, T cells) exert cytotoxic activity against target cells (eg, tumor cells).

[0032] The terms "CDR L1", "CDR L2" and "CDR L3" as provided herein refer to complementarity determining regions (CDRs) 1, 2 and 3 of the variable light chain (L) of an antibody. In some embodiments, the variable light chains provided herein comprise, from the N-terminus to the C-terminus, CDR L1, CDR L2 and CDR L3. Similarly, the terms "CDR H1", "CDR H2" and "CDR H3" as provided herein refer to complementarity determining regions (CDRs) 1, 2 and 3 of the variable heavy chain (H) of an antibody. In some embodiments, the variable heavy chains provided herein comprise, from the N-terminus to the C-terminus, CDR H1, CDR H2 and CDR H3.

[0033] The terms "FR L1", "FR L2", "FR L3" and "FR L4" provided herein are used according to their general meaning in the art and refer to framework regions (FR) 1, 2, 3 and 4 of the variable light chain (L) of an antibody. In some embodiments, the variable light chain provided herein comprises, from N-terminal to C-terminal, FR L1, FR L2, FR L3 and FR L4. Similarly, the terms "FR H1", "FR H2", "FR H3" and "FR H4" provided herein are used according to their general meaning in the art and refer to framework regions (FR) 1, 2, 3 and 4 of the variable heavy chain (H) of an antibody. In some embodiments, the variable heavy chain provided herein comprises, from N-terminal to C-terminal, FR H1, FR H2, FR H3 and FR H4.

[0034] The term "antibody" is used according to its commonly known meaning in the art. Antibodies exist, for example, as intact immunoglobulins or as a number of well-characterized fragments produced by digestion with various peptidases. Thus, for example, pepsin digests antibodies below the disulfide bonds in the hinge region to produce V fragments that are themselves bound by disulfide bonds. H -C H1 A dimer of Fab, a light chain bound to F(ab)' 2 F(ab)' is produced. 2 can be reduced under mild conditions to disrupt the disulfide bonds in the hinge region, thereby forming F(ab)' 2Dimers can be converted to Fab' monomers. Fab' monomers are essentially Fab' with part of the hinge region (see Fundamental Immunology (Paul ed., 3rd ed. 1993)). Although various antibody fragments have been defined in terms of the digestion of intact antibodies, one skilled in the art will appreciate that such fragments can be synthesized de novo, either chemically or using recombinant DNA methodology. Thus, the term antibody as used herein also includes antibody fragments produced by the modification of whole antibodies or those synthesized de novo using recombinant DNA methodology (e.g., single chain Fv) or those identified using phage display libraries (see, e.g., McCafferty et al., Nature 348:552-554 (1990)).

[0035] An exemplary immunoglobulin (antibody) structural unit comprises a tetramer. Each tetramer consists of two identical pairs of polypeptide chains, each pair having one "light" chain (about 25 kD) and one "heavy" chain (about 50-70 kD). The N-terminus of each chain defines a variable region of about 100-110 or more amino acids primarily responsible for antigen recognition. The terms variable light chain (VL) or light chain variable region, and variable heavy chain (VH) or heavy chain variable region refer to these light and heavy chain regions, respectively. The terms variable light chain (VL) and light chain variable region referred to herein may be used interchangeably. The terms variable heavy chain (VH) and heavy chain variable region referred to herein may be used interchangeably. The Fc (i.e., fragment crystallizable region) is the "base" or "tail" of an immunoglobulin and is usually composed of two heavy chains contributing two or three constant domains, depending on the class of the antibody. The Fc region binds to specific proteins, ensuring that each antibody elicits an appropriate immune response to a specific antigen. The Fc region also binds to various cellular receptors, such as Fc receptors, and other immune molecules, such as complement proteins.

[0036] Single chain variable fragments (scFv) are usually fusion proteins of the variable regions of immunoglobulin heavy (VH) and light (VL) chains, connected by a short linker peptide of 10 to about 25 amino acids. The linker can usually be rich in glycine for flexibility or rich in serine or threonine for solubility. The linker can connect the N-terminus of VH to the C-terminus of VL, or vice versa.

[0037] The term "antigen" as provided herein refers to a molecule that can bind to an antibody binding domain as provided herein. An "antigen binding domain" as provided herein is a region of an antibody that binds to an antigen (epitope). As described above, an antigen binding domain is generally composed of one constant domain and one variable domain of each of the heavy and light chains (CH, CL, VH, and VL, respectively). The paratope or antigen binding site is formed at the N-terminus of the antigen binding domain. The two variable domains of the antigen binding domain usually bind to an epitope on the antigen.

[0038] For the production of monoclonal or polyclonal antibodies, any technique known in the art can be used (see, for example, Kohler & Milstein, Nature 256:495-497 (1975); Kozbor et al., Immunology Today 4:72 (1983); Cole et al., pp.77-96 in Monoclonal Antibodies and Cancer Therapy (1985)). A "monoclonal" antibody (mAb) refers to an antibody derived from a single clone. Techniques for the production of single chain antibodies (U.S. Pat. No. 4,946,778) can be adapted to produce antibodies against the polypeptides of the invention. Transgenic mice, or other organisms such as other mammals, may also be used to express humanized antibodies. Alternatively, phage display technology can be used to identify antibodies and heteromeric Fab fragments that specifically bind to a selected antigen (see, e.g., McCafferty et al., Nature 348:552-554 (1990); Marks et al., Biotechnology 10:779-783 (1992)).

[0039] The epitope of a mAb is the region of its antigen to which the mAb binds. Two antibodies bind to the same or overlapping epitopes if each competitively inhibits (blocks) the binding of the other to the antigen. That is, a 1-fold, 5-fold, 10-fold, 20-fold, or 100-fold excess of one antibody inhibits the binding of the other antibody by at least 30%, preferably 50%, 75%, 90%, or even 99%, as measured in a competitive binding assay (see, e.g., Junghans et al., Cancer Res. 50:1495, 1990). Alternatively, two antibodies have the same epitope if essentially all amino acid mutations in the antigen that reduce or eliminate binding of one antibody reduce or eliminate binding of the other antibody. Two antibodies have overlapping epitopes if some amino acid mutations that reduce or eliminate binding of one antibody reduce or eliminate binding of the other antibody.

[0040] An "antibody region" as provided herein refers to a monovalent or multivalent protein moiety that forms part of a protein provided herein, including embodiments thereof, and that is capable of binding to an antigen (epitope). An antibody region as provided herein may comprise a domain of an antibody or a fragment thereof (e.g., Fab). Thus, an antibody region may comprise a light chain variable domain (VL) and / or a heavy chain variable domain (VH). In some embodiments, an antibody region as provided herein comprises a light chain variable (VL) domain. In some embodiments, an antibody region is a light chain variable (VL) domain.

[0041] As stated above, the term "light chain variable (VL) domain" as provided herein refers to the variable region of the light chain of an antibody, antibody variant, or fragment thereof. Similarly, the term "heavy chain variable (VH) domain" as provided herein refers to the variable region of the heavy chain of an antibody, antibody variant, or fragment thereof. The light chain variable domain and the heavy chain variable domain together form a paratope, which binds to an antigen (epitope). The paratope or antigen binding site is formed at the N-terminus of an antibody, antibody variant, or fragment thereof. In some embodiments, the light chain variable (VL) domain comprises CDR L1, CDR L2, CDR L3, and FR L1, FR L2, FR L3, and FR L4 (framework regions) of an antibody light chain. In some embodiments, the heavy chain variable (VH) domain comprises CDR H1, CDR H2, CDR H3, and FR H1, FR H2, FR H3, and FR H4 (framework regions) of an antibody heavy chain. In some embodiments, the light chain variable (VL) domain and the light chain constant (CL) domain form part of an antibody light chain. In some embodiments, the heavy chain variable (VH) domain and the heavy chain constant (CH1) domain form part of an antibody heavy chain. In some embodiments, the heavy chain variable (VH) domain and one or more heavy chain constant (CH1, CH2, or CH3) domains form part of an antibody heavy chain. Thus, in some embodiments, the light chain variable (VL) domain forms part of an antibody. In some embodiments, the heavy chain variable (VH) domain forms part of an antibody. In some embodiments, the light chain variable (VL) domain forms part of a therapeutic antibody. In some embodiments, the heavy chain variable (VH) domain forms part of a therapeutic antibody. In some embodiments, the light chain variable (VL) domain forms part of a human antibody. In some embodiments, the heavy chain variable (VH) domain forms part of a human antibody. In some embodiments, the light chain variable (VL) domain forms part of a human antibody. In some embodiments, the light chain variable (VL) domain forms part of a humanized antibody. In some embodiments, the heavy chain variable (VH) domain forms part of a humanized antibody. In some embodiments, the light chain variable (VL) domain forms part of a chimeric antibody. In some embodiments, the heavy chain variable (VH) domain forms part of a chimeric antibody.In some embodiments, the light chain variable (VL) domain forms part of an antibody fragment. In some embodiments, the heavy chain variable (VH) domain forms part of an antibody fragment. In some embodiments, the light chain variable (VL) domain forms part of an antibody variant. In some embodiments, the heavy chain variable (VH) domain forms part of an antibody variant. In some embodiments, the light chain variable (VL) domain forms part of a Fab. In some embodiments, the heavy chain variable (VH) domain forms part of a Fab. In some embodiments, the light chain variable (VL) domain forms part of an scFv. In some embodiments, the heavy chain variable (VH) domain forms part of an scFv. In some embodiments, the light chain variable (VL) domain forms part of a bispecific antibody. In some embodiments, the heavy chain variable (VH) domain forms part of a bispecific antibody.

[0042] When applied to a protein, the term "isolated" means that the protein is essentially free from other cellular components with which it is associated in the natural state. It may be in a dry or aqueous solution, but is preferably in a homogeneous state. Purity and homogeneity are usually determined using analytical chemistry techniques such as polyacrylamide gel electrophoresis or high performance liquid chromatography. A protein that is present as the predominant species in a preparation is substantially purified. The term "purified" means that the protein gives rise to essentially one band in an electrophoretic gel. In particular, it means that the protein is at least 85% pure, more preferably at least 95% pure, and most preferably at least 99% pure.

[0043] When referring to a protein or peptide, the phrases "specifically (or selectively) bind" or "specifically (or selectively) immunoreact" refer to a binding reaction that is determinative of the presence of the protein in a heterogeneous population of proteins and other biologics. Thus, under specified immunoassay conditions, a particular antibody binds to a particular protein at least twice as much as background and does not bind in any substantial significant amount to other proteins present in the sample. Typically, a specific or selective reaction is at least twice the background signal or noise, and more typically, is greater than 10 to 100 times background.

[0044] A "humanized antibody" is generally an engineered antibody in which at least one CDR (or a functional fragment thereof) from a mouse antibody (the "donor antibody", which may be a rat, hamster, or other non-human species) has been grafted onto a human antibody (the "acceptor antibody"). In some embodiments, more than one mouse CDR is grafted (e.g., all six mouse CDRs are grafted). The sequence of the acceptor antibody may be, for example, a mature human antibody sequence (or a fragment thereof), a consensus sequence of a human antibody sequence (or a fragment thereof), or a germline region sequence (or a fragment thereof). Thus, a humanized antibody may be an antibody having one or more CDRs from a donor antibody and a variable region framework (FR). The FR may form part of the constant and / or variable region in a human antibody. Furthermore, to retain high binding affinity, an amino acid in the human acceptor sequence may be replaced with a corresponding amino acid from the donor sequence, e.g., if (1) the amino acid is in a CDR, or (2) the amino acid is in a human framework region (e.g., if the amino acid is immediately adjacent to one of the CDRs). See U.S. Patent Nos. 5,530,101 and 5,585,089, which are incorporated herein by reference, which provide detailed methods for the construction of humanized antibodies. A humanized antibody often incorporates all six CDRs from a murine antibody (e.g., those defined by Kabat, but often also including the hypervariable loop H1 defined by Chothia), but it can be made with fewer murine CDRs and / or with less than the entire murine CDR sequences (e.g., functional fragments of the CDRs). (See, e.g., Pascalis et al., J. Immunol. 169:3076, 2002; Vajdos et al., Journal of Molecular Biology, 320:415-428, 2002; Iwahashi et al., Mol. Immunol. 36:1079-1091, 1999; Tamura et al., Journal of Immunology, 164:1432-1441, 2000).

[0045] Typically, a humanized antibody provided herein may comprise (i) a light chain variable region comprising at least one (often three) CDRs (also referred to herein as mouse CDRs) derived from a mouse antibody and a human variable region framework, and (ii) a heavy chain variable region comprising at least one (often three) CDRs derived from a mouse antibody and a human variable region framework (FR). The light and heavy chain variable region frameworks (FR) may be a mature human antibody variable region framework sequence (or a fragment thereof), a germline variable region framework sequence (combined with a J region sequence) (or a fragment thereof), or a consensus sequence of a human antibody variable region framework sequence (or a fragment thereof). In some embodiments, the humanized antibody comprises a light chain variable region as described in (i) and a heavy chain variable region as described in (ii), together with a light chain human constant region and a heavy chain human constant region.

[0046] Other approaches to engineer humanized antibodies may be used to achieve the same results as the methods of U.S. Pat. Nos. 5,530,101 and 5,585,089, supra, such as "superhumanization" (see Tan et al., J. Immunol 169:1119, 2002, and U.S. Pat. No. 6,881,557), or the method of Studnicak et al., Protein Eng. 7:805, 1994. Additionally, other approaches to producing engineered, less immunogenic mAbs include "reshaping," "hyperchimerization," and veneering / resurfacing, as described, for example, in Vaswami et al., Annals of Allergy, Asthma and Immunology 81:105, 1998; Roguska et al., Protein Eng. 9:895, 1996; and U.S. Pat. Nos. 6,072,035 and 5,639,641.

[0047] "Ligand" refers to a substance, such as a polypeptide or other molecule, that can bind to a receptor molecule (eg, an antibody).

[0048] "Contacting" is used according to its plain and ordinary meaning to refer to a process that allows at least two different species (e.g., chemical compounds, including biological molecules or cells) to come into sufficient proximity to react, interact, or come into physical contact. However, it should be understood that the resulting reaction product may be produced directly from the reaction between the added reagents, or may be produced from an intermediate that may be produced in the reaction mixture derived from one or more added reagents.

[0049] The term "contacting" can include allowing two species to react, interact, or come into physical contact, where the two species can be an antibody and a BAFF-R protein as described herein. In some embodiments, contacting includes, for example, allowing a humanized antibody as described herein to interact with BAFF-R.

[0050] As used herein, a "cell" refers to a cell that performs metabolic or other functions sufficient to preserve or replicate its genomic DNA. Cells may be identified by methods well known in the art, including, for example, the presence of an intact membrane, staining with a particular dye, the ability to produce progeny, or, in the case of gametes, the ability to combine with a second gamete to produce viable progeny. Cells may include prokaryotic and eukaryotic cells. Prokaryotic cells include, but are not limited to, bacteria. Eukaryotic cells include, but are not limited to, yeast cells and cells derived from plants and animals, such as mammalian cells, insect cells (e.g., Spodoptera), and human cells.

[0051] As defined herein, the terms "inhibitor," "inhibit," "inhibit," "inhibiting," and the like, with respect to protein-inhibitor interactions, refer to adversely affecting (e.g., decreasing) the activity or function of a protein compared to the activity or function of the protein in the absence of the inhibitor. In some embodiments, inhibition refers to the alleviation of a disease or a symptom of a disease (e.g., cancer or an autoimmune disease). Thus, inhibition includes at least a partial, or partial, or complete blocking of stimulation, or decreasing, preventing, or delaying activation, or inactivating, desensitizing, or downregulating signal transduction, or enzyme activity, or the amount of a protein. Similarly, an "inhibitor" is a compound or protein that inhibits activity, for example, by binding, partial or complete blocking, decreasing, preventing, delaying, inactivating, desensitizing, or downregulating.

[0052] The term "disease" or "condition" refers to an existing state or health condition of a patient or subject that can be treated with the compounds, pharmaceutical compositions, or methods provided herein. In some embodiments, the disease is cancer (e.g., lung cancer, ovarian cancer, osteosarcoma, bladder cancer, cervical cancer, liver cancer, kidney cancer, skin cancer (e.g., Merkel cell carcinoma), testicular cancer, leukemia, lymphoma, head and neck cancer, colorectal cancer, prostate cancer, pancreatic cancer, melanoma, breast cancer, neuroblastoma). The disease can be an autoimmune disease, an inflammatory disease, a cancer, an infectious disease, a metabolic disease, a developmental disease, a cardiovascular disease, a liver disease, an intestinal disease, an endocrine disease, a neurological disease, or other disease.

[0053] As used herein, the term "cancer" refers to all types of cancer, neoplasms, or malignant tumors found in mammals, including leukemia, lymphoma, melanoma, neuroendocrine tumors, carcinomas, and sarcomas. Exemplary cancers that may be treated with the compounds, pharmaceutical compositions, or methods provided herein include lymphoma, sarcoma, bladder cancer, bone cancer, brain cancer, cervical cancer, colon cancer, esophageal cancer, gastric cancer, head and neck cancer, kidney cancer, myeloma, thyroid cancer, leukemia, prostate cancer, breast cancer (e.g., triple negative, ER positive, ER negative, chemotherapy resistant, herceptin resistant, HER2 positive, doxorubicin resistant, tamoxifen resistant, ductal carcinoma, lobular carcinoma, primary, metastatic), ovarian cancer, and the like. , pancreatic cancer, liver cancer (e.g., hepatocellular carcinoma), lung cancer (e.g., non-small cell lung cancer, squamous cell lung cancer, adenocarcinoma, large cell lung cancer, small cell lung cancer, carcinoid, sarcoma), glioblastoma multiforme, glioma, melanoma, prostate cancer, castration-resistant prostate cancer, breast cancer, triple-negative breast cancer, glioblastoma, ovarian cancer, lung cancer, squamous cell carcinoma (e.g., head, neck, or esophageal), colorectal cancer, leukemia, acute myeloid leukemia, lymphoma, B-cell lymphoma, or multiple myeloma. Additional examples include thyroid cancer, endocrine system cancer, brain cancer, breast cancer, cervical cancer, colon cancer, head and neck cancer, esophageal cancer, liver cancer, kidney cancer, lung cancer, non-small cell lung cancer, melanoma, mesothelioma, ovarian cancer, sarcoma, gastric cancer, uterine cancer, or medulloblastoma, Hodgkin's disease, non-Hodgkin's lymphoma, multiple myeloma, neuroblastoma, glioma, glioblastoma multiforme, ovarian cancer, rhabdomyosarcoma, primary thrombocythemia, primary macroglobulinemia, primary brain tumors, cancer, malignant pancreatic insulinoma, linoma, malignant carcinoid, bladder cancer, premalignant skin lesions, testicular cancer, lymphoma, thyroid cancer, neuroblastoma, esophageal cancer, genitourinary cancer, malignant hypercalcemia, endometrial cancer, adrenal cortical carcinoma, endocrine or exocrine pancreatic neoplasms, medullary thyroid cancer, medullary thyroid carcinoma, melanoma, colorectal cancer, papillary thyroid cancer, hepatocellular carcinoma, Paget's disease of the nipple, phyllodes tumor, lobular carcinoma, ductal carcinoma, pancreatic stellate cell carcinoma, hepatic stellate cell carcinoma, or prostate cancer.

[0054] The term "leukemia" refers broadly to progressive, malignant diseases of the blood-forming organs and is generally characterized by distorted proliferation and development of white blood cells and their precursor cells in the blood and bone marrow. Leukemias are generally classified clinically based on (1) the duration and characteristics of the disease (acute or chronic), (2) the type of cells involved (bone marrow (myeloid), lymph (lymphogenetic), or monocytic), and (3) the increase or absence of an increase in the number of abnormal cells in the blood leukemic or non-leukemic (subleukemic). Exemplary leukemias that may be treated with the compounds, pharmaceutical compositions, or methods provided herein include, for example, acute nonlymphocytic leukemia, chronic lymphocytic leukemia, acute granulocytic leukemia, chronic granulocytic leukemia, acute promyelocytic leukemia, adult T-cell leukemia, non-leukemic leukemia, leukemic leukemia, basophilic leukemia, blast cell leukemia, bovine leukemia, chronic myelocytic leukemia, leukemia cutis, fetal leukemia, Eosinophilic leukemia, Gross leukemia, Hairy cell leukemia, Hemoblastic leukemia, Hemoblastic leukemia, Histiocytic leukemia, Stem cell leukemia, Acute monocytic leukemia, Leukopenic leukemia, Lymphocytic leukemia, Lymphoblastic ... leukemia, small myeloblastic leukemia, monocytic leukemia, myeloblastic leukemia, myeloblastic leukemia, myelogranulocytic leukemia, myelomonocytic leukemia, Naegeli leukemia, plasma cell leukemia, multiple myeloma, plasma cell leukemia, promyelocytic leukemia, Rieder cell leukemia, Schilling leukemia, stem cell leukemia, subleukemic leukemia, or anaplastic cell leukemia.

[0055] As used herein, the terms "metastasis", "metastatic" and "metastatic cancer" can be used interchangeably and refer to the spread of a proliferative disease or disorder, e.g., cancer, from one organ or another non-adjacent organ or part of the body. Cancer begins at a site of origin, e.g., the breast, referred to as a primary tumor, e.g., primary breast cancer. Some cancer cells in the primary tumor or site of origin acquire the ability to penetrate and invade surrounding normal tissues in the local area and / or penetrate the walls of the lymphatic or vascular system and circulate through the system to other sites and tissues of the body. A clinically detectable secondary tumor formed from cancer cells of the primary tumor is called a metastatic or secondary tumor. When cancer cells metastasize, the metastatic tumor and its cells are presumed to be similar to those of the original tumor. Thus, when lung cancer metastasizes to the breast, the secondary tumor at the breast site is composed of abnormal lung cells, not abnormal breast cells. A secondary tumor in the breast is referred to as metastatic lung cancer. Thus, the phrase metastatic cancer refers to a disease in which a subject has or has had a primary tumor, and has one or more secondary tumors.The phrase non-metastatic cancer or a subject with non-metastatic cancer refers to a disease in which a subject has a primary tumor but does not have one or more secondary tumors.For example, metastatic lung cancer refers to a disease in a subject who has or has had a history of a primary lung tumor, and has one or more secondary tumors, for example, in a second location in the breast or in multiple locations.

[0056] In the context of a substance or an activity or function of a substance that is related to a disease (cancer (e.g., leukemia, lymphoma, B-cell lymphoma, multiple myeloma, etc.)), the term "related to" or "related to" means that the disease (cancer (e.g., leukemia, lymphoma, B-cell lymphoma, multiple myeloma, etc.)) is caused (in whole or in part) or a symptom of the disease is caused (in whole or in part) by the substance or an activity or function of the substance.

[0057] The term "autoimmune disease" as used herein refers to a disease or condition in which a subject's immune system exhibits an abnormal immune response to a substance that does not normally elicit an immune response in healthy subjects. Examples of autoimmune diseases that can be treated with the compounds, pharmaceutical compositions, or methods described herein include acute disseminated encephalomyelitis (ADEM), acute necrotizing hemorrhagic leukoencephalitis, Addison's disease, agammaglobulinemia, skin rash, amyloidosis, ankylosin spondylomyelitis, anti-GBM / anti-TBM nephritis, antiphospholipid syndrome (APS), autoimmune angioedema, autoimmune aplastic anemia, autoimmune dysautonomia, autoimmune hepatitis, autoimmune hyperlipidemia, autoimmune immunodeficiency, autoimmune inner ear disease (AIED), autoimmune inflammatory bowel ... Autoimmune myocarditis, autoimmune oophoritis, autoimmune pancreatitis, autoimmune retinitis, autoimmune pancreatic hormonopathy thrombocytopenic purpura (ATP), autoimmune thyroid disease, autoimmune urticaria, axonal or neuronal neuropathy, Baro's disease, Behcet's disease, bullous pephigoid, cardiomyopathy, Castleman's disease, celiac disease, Chagas' disease, chronic fatigue syndrome, chronic inflammatory demyelinating polyneuropathy (CIDP), chronic relapsing granulomatosis with polyangiitis (CRMO), Churg-Strauss syndrome, cicatricial scaly / benign mucous membrane malformation, Crohn's disease, Coron's disease, Gunn's syndrome, cold agglutinin disease, congenital heart block, Coxsackie myocarditis, CREST disease, essential mixed cryoglobulinemia, demyelinating neuropathy, dermatitis herpetiformis, dermatomyositis, Devic's disease (neuromyelitis optica), discoid lupus, Dressler's syndrome, endometriosis, eosinophilic esophagitis, eosinophilic fasciitis, conjunctivitis, experimental allergic encephalomyelitis, Evans syndrome, fibromyalgia, fibrosing alveolitis, giant cell arteritis (temporal arteritis), giant cell myocarditis, glomerulonephritis, Goodpasture's syndrome, polyangiitis Granulomatous granulomatosis (GPA) (previously called Wegener's granulomatosis), Graves' disease, Guillain-Barr syndrome, Hashimoto's encephalitis, Hashimoto's thyroiditis, hemolytic anemia, Henoch-Schoon disease, hemolytic anemia, hypogammaglobulinemia, idiopathic thrombocytopenic purpura (ITP), IgA nephropathy, IgG4-related sclerosing disease, immunomodulatory lipoproteins, inclusion body myositis, interstitial cystitis, juvenile arthritis, juvenile diabetes mellitus (type 1 diabetes), juvenile myositis, Kawasaki syndrome, Lambert-Eaton vasculitis, leukemic lichen, lichen planus, lichen sclerosus, lymphocytic conjunctivitis,Linear immunoglobulin A disease (LAD), lupus (SLE), Lyme disease, chronic, Meniere's disease, microscopic polyangiitis, mixed connective tissue disease (MCTD), Mooren's ulcer, Mucha-Habermann disease, multiple sclerosis, severe myositis, myositis, narcolepsy, neuromyelitis optica (Devic's), neutropenia, ocular cicatricial uveitis, ocular neuritis, relapsing rheumatism, PANDAS (pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection), paraneoplastic Cerebellar degeneration, paroxysmal nocturnal hemoglobinuria (PNH), Parry-Romberg syndrome, Parsonage-Turner syndrome, Persplanitis (peripheral uveitis), Pemfigus, peripheral neuropathy, periphratic encephalomyelitis, pernicious anemia, POEMS syndrome, polyarteritis nodosa, autoimmune polyglandular syndrome types I, II, and III, polymyalgia rheumatica, polymyositis, post-myocardial infarction syndrome, post-pericardiotomy syndrome, progesterone dermatitis, primary angina, psoriatic arthritis, primary sclerosing cholangitis, psoriasis, psoriatic arthritis, idiopathic pulmonary fibrosis, ganglionic pyoderma, pure red cell hypoplasia, Raynaud's phenomenon, reactive arthritis, reflex sympathetic dystrophy, Reiter's syndrome, relapsing polychondritis, restless leg syndrome, retroperitoneal fibrosis, rheumatic fever, rheumatoid arthritis, sarcoid arthritis, Schmidt's syndrome, scleritis, scleroderma, Sjogren's syndrome, spermatozoa and spermatozoa These include focal autoimmunity, stiffening syndrome, subacute bacterial endocarditis (SBE), Sazac syndrome, sympathetic ophthalmopathy, Takayasu's arteritis, temporal arteritis-giant cell arteritis, thrombocytopenic purpura (TTP), Tolosa-Hunt syndrome, transverse myelitis, type 1 diabetes, ulcerative colitis, undifferentiated connective tissue disease (UCTD), uveitis, vasculitis, bullous dermatoses, vitiligo, or Wegener's granulomatosis (i.e., granulomatosis with polyangiitis (GPA)).

[0058] "B cells" or "B lymphocytes" refer to their standard usage in the art. B cells are lymphocytes, a type of white blood cell (leukocyte), that develop into plasma cells ("mature B cells") and produce antibodies. "Immature B cells" are cells that can develop into mature B cells. Generally, pro-B cells undergo immunoglobulin heavy chain rearrangement to become pro-B pre-B cells, which then undergo immunoglobulin light chain rearrangement to become immature B cells. Immature B cells include T1 and T2 B cells.

[0059] As used herein, "T cells" or "T lymphocytes" are a type of lymphocyte (a subtype of white blood cell) that plays a central role in cell-mediated immunity. They can be distinguished from other lymphocytes, such as B cells and natural killer cells, by the presence of T cell receptors on the cell surface. T cells include, for example, natural killer T (NKT) cells, cytotoxic T lymphocytes (CTL), regulatory T (Treg) cells, and T helper cells. The various types of T cells can be distinguished using T cell detection agents.

[0060] "Memory T cells" are T cells that have previously encountered and responded to their alloantigen during a previous infection, cancer encounter, or previous vaccination. Upon a second encounter with the alloantigen, memory T cells can replicate (divide) and mount a faster and stronger immune response than when the immune system first responded to the pathogen.

[0061] "Regulatory T cells" or "suppressor T cells" are lymphocytes that regulate the immune system, maintain tolerance to self-antigens, and prevent autoimmune diseases.

[0062] The term "effector cell ligand" provided herein refers to a cell surface molecule expressed on an effector cell of the immune system (e.g., cytotoxic T cells, helper T cells, B cells, natural killer cells). Upon binding of the first antibody region to the effector cell ligand expressed on the effector cell, the effector cell is activated and can exert its function (e.g., selective killing or eradication of malignant, infected, or other unhealthy cells). In some embodiments, the effector cell ligand is a CD3 protein. In some embodiments, the effector cell ligand is a CD16 protein. In some embodiments, the effector cell ligand is a CD32 protein. In some embodiments, the effector cell ligand is a NKp46 protein. The first antibody region provided herein can be an antibody, an antibody variant, a fragment of an antibody, or a fragment of an antibody variant.

[0063] A "CD3 protein" as referred to herein includes any recombinant or naturally occurring form of cluster of differentiation 3 (CD3) protein or variant or homologue thereof that comprises the CD3 complex, mediates signal transduction, and maintains CD3 complex activity (e.g., within at least 50%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% of the activity as compared to the CD3 complex). In some embodiments, the variant or homologue has at least 90%, 95%, 96%, 97%, 98%, 99%, or 100% amino acid sequence identity over the entire sequence or a portion of the sequence (e.g., a portion of 50, 100, 150, or 200 contiguous amino acids) as compared to a naturally occurring CD3 protein in the CD3 complex.

[0064] A "CD16 protein" as referred to herein includes any recombinant or naturally occurring form of Cluster of Differentiation 16 (CD16), also known as the low affinity immunoglobulin gamma Fc region receptor III-A, or a variant or homolog thereof, that maintains CD16 activity (e.g., within at least 50%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% activity compared to CD16). In some embodiments, the variant or homolog has at least 90%, 95%, 96%, 97%, 98%, 99%, or 100% amino acid sequence identity over the entire sequence or a portion of the sequence (e.g., a portion of 50, 100, 150, or 200 contiguous amino acids) compared to a naturally occurring CD16 protein. In some embodiments, the CD16 protein is substantially identical to the protein identified by UniProt reference number P08637, or a variant or homolog having substantial identity thereto.

[0065] As referred to herein, a "CD32 protein" includes any recombinant or naturally occurring form of cluster of differentiation 32 (CD32), also known as the low affinity immunoglobulin gamma Fc region receptor II-A, or a variant or homolog thereof, that maintains CD32 activity (e.g., within at least 50%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% activity compared to CD32). In some embodiments, the variant or homolog has at least 90%, 95%, 96%, 97%, 98%, 99%, or 100% amino acid sequence identity over the entire sequence or a portion of the sequence (e.g., a portion of 50, 100, 150, or 200 contiguous amino acids) compared to a naturally occurring CD32 protein. In some embodiments, the CD32 protein is substantially identical to the protein identified by UniProt reference number P12318, or a variant or homolog having substantial identity thereto.

[0066] As referred to herein, an "NKp46 protein" includes any recombinant or naturally occurring form of the NKp46 protein or variant or homolog thereof that maintains NKp46 activity, also known as cytotoxicity-inducing receptor 1 (e.g., within at least 50%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% activity compared to NKp46). In some aspects, the variant or homolog has at least 90%, 95%, 96%, 97%, 98%, 99%, or 100% amino acid sequence identity over the entire sequence or a portion of the sequence (e.g., a 50, 100, 150, or 200 contiguous amino acid portion) compared to a naturally occurring NKp46 protein. In some embodiments, the NKp46 protein is substantially identical to a protein identified by UniProt reference number O76036, or a variant or homolog having substantial identity thereto.

[0067] As referred to herein, "BAFF-R," "BAFF receptor," or "BAFF-R protein" includes any recombinant or naturally occurring form of B-cell activating factor receptor (BAFF-R), also known as tumor necrosis factor receptor superfamily member 13C (TNFRSF13C), or a variant or homolog thereof, that maintains BAFF-R activity (e.g., within at least 50%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% activity compared to BAFF-R). In some embodiments, the variant or homolog has at least 90%, 95%, 96%, 97%, 98%, 99%, or 100% amino acid sequence identity over the entire sequence or a portion of the sequence (e.g., a portion of 50, 100, 150, or 200 contiguous amino acids) compared to naturally occurring BAFF-R. In some embodiments, BAFF-R is substantially identical to the protein identified by UniProt reference number Q96RJ3, or a variant or homolog having substantial identity thereto. In some embodiments, BAFF-R is substantially identical to the protein identified by UniProt reference number Q9D8D0, or a variant or homolog having substantial identity thereto. In some embodiments, BAFF-R is substantially identical to the protein identified by NCBI reference number GI:16445027, or a variant or homolog having substantial identity thereto. In some embodiments, BAFF-R is substantially identical to the protein identified by NCBI reference number GI:16306481, or a variant or homolog having substantial identity thereto. II. Recombinant Protein Compositions

[0068] Provided herein, inter alia, are recombinant proteins (e.g., bispecific antibodies) capable of binding to BAFF-R and effector cells through binding to an effector cell expressed antigen (e.g., CD3). The recombinant proteins (e.g., bispecific antibodies) comprise (i) a first antibody region capable of binding to an effector cell ligand (e.g., CD3) and (ii) a second antibody region capable of binding to a second antibody antigen (e.g., human BAFF-R protein), and bind to human BAFF-R protein with high affinity and specificity. The recombinant proteins (e.g., bispecific antibodies) provided herein simultaneously bind to an antigen on an effector cell (e.g., CD3 on an effector T cell) and BAFF-R on a B cell, resulting in effector cells (e.g., T cells) killing malignant or autoreactive B cells. Thus, the compositions and methods provided herein may be used, inter alia, to treat cancer (e.g., B cell malignancies) or autoimmune diseases. In the present invention, the second antibody region provided herein, including embodiments thereof, includes any of the BAFF-R specific antibodies described in published international application PCT / US2017 / 036178, which is hereby incorporated by reference for all purposes. For example, the second antibody region may include any of the humanized BAFF-R antibodies referred to herein as "H90 Ab," "humanized C90," "humanized C90-1," "humanized C90-2," "humanized C90-3," "C90," "C90-1," "C90-2," or "C90-3."

[0069] In one aspect, a recombinant protein is provided comprising (i) a first antibody region capable of binding to an effector cell ligand (e.g., CD3) and (ii) (a) a second antibody region comprising a light chain variable domain and a heavy chain variable domain. The light chain variable domain comprises CDR L1 as set forth in SEQ ID NO:1, CDR L2 as set forth in SEQ ID NO:2, and CDR L3 as set forth in SEQ ID NO:3. The heavy chain variable domain comprises CDR H1 as set forth in SEQ ID NO:4, CDR H2 as set forth in SEQ ID NO:5, and CDR H3 as set forth in SEQ ID NO:6. In some embodiments, the second antibody region binds to a BAFF-R protein or a fragment thereof. When a CDR as set forth herein is "set forth" in a SEQ ID NO (e.g., SEQ ID NO:1, 2, 3, 4, 5, 6, 38, 38, 40, 41, 42, 43), the CDR has the sequence referenced by that SEQ ID NO. In general, when a sequence is set forth in a particular SEQ ID NO, the sequence has the sequence referenced by that SEQ ID NO.

[0070] The recombinant proteins provided herein include light and heavy chain variable regions derived from various antibody clones (e.g., C90-1, C90-2, C90-3, C55-1, C55-2, C55-3) and include the same CDRs and different FRs (e.g., C90-1, C90-2, and C90-3) or different CDRs (e.g., CDRs from the C90 clone and CDRs from the C55 clone). The second antibody region of the recombinant proteins provided herein, including its embodiments, can be an scFv. When the second antibody region is an scFv, the second antibody region is referred to as H90, C90-1, C90-2, or C90-3 and includes CDR L1 as set forth in SEQ ID NO:1, CDR L2 as set forth in SEQ ID NO:2, CDR L3 as set forth in SEQ ID NO:3, CDR H1 as set forth in SEQ ID NO:4, CDR H2 as set forth in SEQ ID NO:5, and CDR H3 as set forth in SEQ ID NO:6. In some embodiments, the second antibody region is an scFv and is referred to as C55-1, C55-2 or C55-3 and comprises CDR L1 set forth in SEQ ID NO:38, CDR L2 set forth in SEQ ID NO:39, CDR L3 set forth in SEQ ID NO:40, CDR H1 set forth in SEQ ID NO:41, CDR H2 set forth in SEQ ID NO:42, and CDR H3 set forth in SEQ ID NO:43.

[0071] In some embodiments, the light chain variable domain comprises the sequence of SEQ ID NO:7, SEQ ID NO:8, or SEQ ID NO:9. In some embodiments, the light chain variable domain comprises the sequence of SEQ ID NO:7. In some embodiments, the light chain variable domain comprises the sequence of SEQ ID NO:8. In some embodiments, the light chain variable domain comprises the sequence of SEQ ID NO:9. In some embodiments, the light chain variable domain is the sequence of SEQ ID NO:7. In some embodiments, the light chain variable domain is the sequence of SEQ ID NO:8. In some embodiments, the light chain variable domain is the sequence of SEQ ID NO:9.

[0072] In some embodiments, the heavy chain variable domain comprises the sequence of SEQ ID NO: 10, SEQ ID NO: 11, or SEQ ID NO: 12. In some embodiments, the heavy chain variable domain comprises the sequence of SEQ ID NO: 10. In some embodiments, the heavy chain variable domain comprises the sequence of SEQ ID NO: 11. In some embodiments, the heavy chain variable domain comprises the sequence of SEQ ID NO: 12. In some embodiments, the heavy chain variable domain is the sequence of SEQ ID NO: 10. In some embodiments, the heavy chain variable domain is the sequence of SEQ ID NO: 11. In some embodiments, the heavy chain variable domain is the sequence of SEQ ID NO: 12.

[0073] In some embodiments, the light chain variable domain comprises FR L1 set forth in SEQ ID NO: 13, FR L2 set forth in SEQ ID NO: 14, FR L3 set forth in SEQ ID NO: 15, and FR L4 set forth in SEQ ID NO: 16. In some embodiments, the heavy chain variable domain comprises FR H1 set forth in SEQ ID NO: 25, FR H2 set forth in SEQ ID NO: 26, FR H3 set forth in SEQ ID NO: 27, and FR H4 set forth in SEQ ID NO: 28.

[0074] In some embodiments, the light chain variable domain comprises FR L1 set forth in SEQ ID NO: 17, FR L2 set forth in SEQ ID NO: 18, FR L3 set forth in SEQ ID NO: 19, and FR L4 set forth in SEQ ID NO: 20. In some embodiments, the heavy chain variable domain comprises FR H1 set forth in SEQ ID NO: 29, FR H2 set forth in SEQ ID NO: 30, FR H3 set forth in SEQ ID NO: 31, and FR H4 set forth in SEQ ID NO: 32.

[0075] In some embodiments, the light chain variable domain comprises FR L1 set forth in SEQ ID NO: 21, FR L2 set forth in SEQ ID NO: 22, FR L3 set forth in SEQ ID NO: 23, and FR L4 set forth in SEQ ID NO: 24. In some embodiments, the heavy chain variable domain comprises FR H1 set forth in SEQ ID NO: 33, FR H2 set forth in SEQ ID NO: 34, FR H3 set forth in SEQ ID NO: 35, and FR H4 set forth in SEQ ID NO: 36.

[0076] In some embodiments, the second antibody region comprises a light chain variable domain of SEQ ID NO: 7 and a heavy chain variable region of SEQ ID NO: 10. In some embodiments, the second antibody region is C90-1. In additional embodiments, the second antibody region comprises a light chain variable domain of SEQ ID NO: 7 and a heavy chain variable region of SEQ ID NO: 10.

[0077] In some embodiments, the second antibody region comprises a light chain variable domain of SEQ ID NO: 8 and a heavy chain variable region of SEQ ID NO: 11. In some embodiments, the second antibody region is C90-2. In additional embodiments, the second antibody region comprises a light chain variable domain of SEQ ID NO: 8 and a heavy chain variable region of SEQ ID NO: 11.

[0078] In some embodiments, the second antibody region comprises a light chain variable domain of SEQ ID NO: 9 and a heavy chain variable region of SEQ ID NO: 12. In some embodiments, the second antibody region is C90-3. In additional embodiments, the second antibody region comprises a light chain variable domain of SEQ ID NO: 9 and a heavy chain variable region of SEQ ID NO: 12.

[0079] In one aspect, there is provided a recombinant protein comprising (i) a first antibody region capable of binding an effector cell ligand, and (ii) (a) a second antibody region comprising a light chain variable domain and a heavy chain variable domain. The light chain variable domain comprises CDR L1 as set forth in SEQ ID NO: 38, CDR L2 as set forth in SEQ ID NO: 39, and CDR L3 as set forth in SEQ ID NO: 40. The heavy chain variable domain comprises CDR H1 as set forth in SEQ ID NO: 41, CDR H2 as set forth in SEQ ID NO: 42, and CDR H3 as set forth in SEQ ID NO: 43.

[0080] In some embodiments, the light chain variable domain comprises the sequence of SEQ ID NO: 44, SEQ ID NO: 45, or SEQ ID NO: 46. In some embodiments, the light chain variable domain comprises the sequence of SEQ ID NO: 44. In some embodiments, the light chain variable domain comprises the sequence of SEQ ID NO: 45. In some embodiments, the light chain variable domain comprises the sequence of SEQ ID NO: 46. In some embodiments, the light chain variable domain is the sequence of SEQ ID NO: 44. In some embodiments, the light chain variable domain is the sequence of SEQ ID NO: 45. In some embodiments, the light chain variable domain is the sequence of SEQ ID NO: 46.

[0081] In some embodiments, the heavy chain variable domain comprises the sequence of SEQ ID NO: 47, SEQ ID NO: 48, or SEQ ID NO: 49. In some embodiments, the heavy chain variable domain comprises the sequence of SEQ ID NO: 47. In some embodiments, the heavy chain variable domain comprises the sequence of SEQ ID NO: 48. In some embodiments, the heavy chain variable domain comprises the sequence of SEQ ID NO: 49. In some embodiments, the heavy chain variable domain is the sequence of SEQ ID NO: 47. In some embodiments, the heavy chain variable domain is the sequence of SEQ ID NO: 48. In some embodiments, the heavy chain variable domain is the sequence of SEQ ID NO: 49.

[0082] In some embodiments, the light chain variable domain comprises FR L1 set forth in SEQ ID NO: 50, FR L2 set forth in SEQ ID NO: 51, FR L3 set forth in SEQ ID NO: 52, and FR L4 set forth in SEQ ID NO: 53. In some embodiments, the heavy chain variable domain comprises FR H1 set forth in SEQ ID NO: 62, FR H2 set forth in SEQ ID NO: 63, FR H3 set forth in SEQ ID NO: 64, and FR H4 set forth in SEQ ID NO: 65.

[0083] In some embodiments, the light chain variable domain comprises FR L1 set forth in SEQ ID NO: 54, FR L2 set forth in SEQ ID NO: 55, FR L3 set forth in SEQ ID NO: 56, and FR L4 set forth in SEQ ID NO: 57. In some embodiments, the heavy chain variable domain comprises FR H1 set forth in SEQ ID NO: 66, FR H2 set forth in SEQ ID NO: 67, FR H3 set forth in SEQ ID NO: 68, and FR H4 set forth in SEQ ID NO: 69.

[0084] In some embodiments, the light chain variable domain comprises FR L1 set forth in SEQ ID NO: 58, FR L2 set forth in SEQ ID NO: 59, FR L3 set forth in SEQ ID NO: 60, and FR L4 set forth in SEQ ID NO: 61. In some embodiments, the heavy chain variable domain comprises FR H1 set forth in SEQ ID NO: 70, FR H2 set forth in SEQ ID NO: 71, FR H3 set forth in SEQ ID NO: 72, and FR H4 set forth in SEQ ID NO: 73.

[0085] In some embodiments, the second antibody region comprises a light chain variable domain of SEQ ID NO: 44 and a heavy chain variable region of SEQ ID NO: 47. In some embodiments, the second antibody region is C55-1. In additional embodiments, the second antibody region comprises a light chain variable domain of SEQ ID NO: 44 and a heavy chain variable region of SEQ ID NO: 47.

[0086] In some embodiments, the second antibody region comprises a light chain variable domain of SEQ ID NO: 45 and a heavy chain variable region of SEQ ID NO: 48. In some embodiments, the second antibody region is C55-2. In additional embodiments, the second antibody region comprises a light chain variable domain of SEQ ID NO: 45 and a heavy chain variable region of SEQ ID NO: 48.

[0087] In some embodiments, the second antibody region comprises a light chain variable domain of SEQ ID NO: 46 and a heavy chain variable region of SEQ ID NO: 49. In some embodiments, the second antibody region is C55-3. In additional embodiments, the second antibody region comprises a light chain variable domain of SEQ ID NO: 46 and a heavy chain variable region of SEQ ID NO: 49.

[0088] The positions of CDRs and FRs are defined by the Kabat numbering system (Kabat et al., Sequences of Proteins of Immunological Interest, 5th ed., U.S. Department of Health and Human Services, U.S. Government Printing Office (1991)). Similarly, the positions occupied by individual residues in the light or heavy chains of an antibody can be defined by the Kabat numbering system. Thus, the positions of residues required for binding in the light and heavy chains of a humanized antibody can be defined by the position of the residues according to the Kabat numbering system, which is well known in the art. As described above, a humanized antibody can be an antibody having CDRs from a donor antibody (e.g., mouse) and variable region frameworks (FRs) from a human antibody. The framework regions (FRs) are said to hold the CDRs in place in the humanized antibody. From the amino terminus, these regions are referred to as FR L1, FR L2, FR L3, and FR L4 for the light chain and FR H1, FR H2, FR H3, and FR H4 for the heavy chain, respectively. Surprisingly, the present invention provides recombinant proteins (e.g., bispecific antibodies) that comprise one or more residues in the framework region that are important for epitope binding of the second antibody region. Framework region residues that are involved (or important) in epitope binding (e.g., BAFF-R binding) are referred to herein as binding framework region residues. Binding framework region residues are present in the framework regions of the light chain variable domain (i.e., FR L1, FR L2, FR L3, FR L4) or in the frameworks of the heavy chain variable domain (i.e., FR H1, FR H2, FR H3, FR H4). Binding framework region residues present in the FR L3 region of the light chain are referred to herein as FR L3 binding framework region residues. Accordingly, binding framework region residues present in the FR H3 region of the heavy chain are referred to herein as FR H3 binding framework region residues.

[0089] In some embodiments, the second antibody region comprises at least one binding framework region residue. In some embodiments, the light chain variable domain comprises at least one binding framework region residue. In some embodiments, the light chain variable domain comprises one or more FR L1, FR L2, FR L3 or FR L4 binding framework region residues. In some embodiments, the light chain variable domain comprises one or more FR L1 binding framework region residues. In some embodiments, the light chain variable domain comprises one or more FR L2 binding framework region residues. In some embodiments, the light chain variable domain comprises one or more FR L3 binding framework region residues. In some embodiments, the light chain variable domain comprises one or more FR L4 binding framework region residues. In some embodiments, the heavy chain variable domain comprises one or more FR H1, FR H2, FR H3 or FR H4 binding framework region residues. In some embodiments, the heavy chain variable domain comprises one or more FR H1 binding framework region residues. In some embodiments, the heavy chain variable domain comprises one or more FR H2 binding framework region residues. In some embodiments, the heavy chain variable domain comprises one or more FR H3 binding framework region residues. In some embodiments, the heavy chain variable domain comprises one or more FR H4-binding framework region residues.

[0090] In some embodiments, the light chain variable domain comprises a nucleotide sequence similar to that of at least one binding framework region residue (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, or more residues). A heavy chain variable domain comprises at least one binding framework region residue (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50 or more residues). The positions of binding framework region residues within an antibody or antibody region may be defined by the Kabat numbering system, similar to the positions of the CDR residues.

[0091] In some embodiments, the light chain variable domain comprises a serine at a position corresponding to Kabat position 7. In some embodiments, the light chain variable domain comprises a proline at a position corresponding to Kabat position 8. In some embodiments, the light chain variable domain comprises a valine at a position corresponding to Kabat position 15. In some embodiments, the light chain variable domain comprises a threonine at a position corresponding to Kabat position 22. In some embodiments, the light chain variable domain comprises a glutamine at a position corresponding to Kabat position 24. In some embodiments, the light chain variable domain comprises a glycine at a position corresponding to Kabat position 41. In some embodiments, the light chain variable domain comprises a lysine at a position corresponding to Kabat position 42. In some embodiments, the light chain variable domain comprises an alanine at a position corresponding to Kabat position 43. In some embodiments, the light chain variable domain comprises a proline at a position corresponding to Kabat position 44. In some embodiments, the light chain variable domain comprises a threonine at a position corresponding to Kabat position 56. In some embodiments, the light chain variable domain comprises a threonine at a position corresponding to Kabat position 72. In some embodiments, the light chain variable domain comprises a phenylalanine at a position corresponding to Kabat position 73. In some embodiments, the light chain variable domain comprises a glutamine at a position corresponding to Kabat position 79. In some embodiments, the light chain variable domain comprises a valine at a position corresponding to Kabat position 104.

[0092] In some embodiments, the light chain variable domain comprises as binding framework region residues a serine at position corresponding to Kabat position 7, a proline at position corresponding to Kabat position 8, a valine at position corresponding to Kabat position 15, a threonine at position corresponding to Kabat position 22, a glutamine or serine at position corresponding to Kabat position 24, a glycine at position corresponding to Kabat position 41, a lysine at position corresponding to Kabat position 42, an alanine or threonine at position corresponding to Kabat position 43, a proline at position corresponding to Kabat position 44, a threonine at position corresponding to Kabat position 56, a threonine at position corresponding to Kabat position 72, a phenylalanine or lysine at position corresponding to Kabat position 73, a glutamine at position corresponding to Kabat position 79, or a valine at position corresponding to Kabat position 104.

[0093] In some embodiments, the light chain variable domain comprises as binding framework region residues a serine at a position corresponding to Kabat position 7, a proline at a position corresponding to Kabat position 8, a valine at a position corresponding to Kabat position 15, a threonine at a position corresponding to Kabat position 22, a glutamine or serine at a position corresponding to Kabat position 24, a glycine at a position corresponding to Kabat position 41, a lysine at a position corresponding to Kabat position 42, an alanine or threonine at a position corresponding to Kabat position 43, a proline at a position corresponding to Kabat position 44, a threonine at a position corresponding to Kabat position 56, a threonine at a position corresponding to Kabat position 72, a phenylalanine or lysine at a position corresponding to Kabat position 73, a glutamine at a position corresponding to Kabat position 79, or a valine at a position corresponding to Kabat position 104.

[0094] In some embodiments, the light chain variable domain comprises as binding framework region residues a serine at position corresponding to Kabat position 7, a proline at position corresponding to Kabat position 8, a valine at position corresponding to Kabat position 15, a threonine at position corresponding to Kabat position 22, a glutamine or serine at position corresponding to Kabat position 24, a glycine at position corresponding to Kabat position 41, a lysine at position corresponding to Kabat position 42, an alanine or threonine at position corresponding to Kabat position 43, a proline at position corresponding to Kabat position 44, a threonine at position corresponding to Kabat position 56, a threonine at position corresponding to Kabat position 72, a phenylalanine or lysine at position corresponding to Kabat position 73, a glutamine at position corresponding to Kabat position 79, or a valine at position corresponding to Kabat position 104.

[0095] In some embodiments, the heavy chain variable domain comprises a threonine or an alanine at a position corresponding to Kabat position 10. In some embodiments, the heavy chain variable domain comprises a lysine at a position corresponding to Kabat position 11. In some embodiments, the heavy chain variable domain comprises a valine at a position corresponding to Kabat position 12. In some embodiments, the heavy chain variable domain comprises a threonine at a position corresponding to Kabat position 15. In some embodiments, the heavy chain variable domain comprises a threonine at a position corresponding to Kabat position 19. In some embodiments, the heavy chain variable domain comprises a threonine at a position corresponding to Kabat position 23. In some embodiments, the heavy chain variable domain comprises a proline at a position corresponding to Kabat position 41. In some embodiments, the heavy chain variable domain comprises an alanine at a position corresponding to Kabat position 44. In some embodiments, the heavy chain variable domain comprises a proline or threonine at a position corresponding to Kabat position 61. In some embodiments, the heavy chain variable domain comprises an arginine at a position corresponding to Kabat position 66. In some embodiments, the heavy chain variable domain comprises a threonine at a position corresponding to Kabat position 70. In some embodiments, the heavy chain variable domain comprises a lysine at a position corresponding to Kabat position 75. In some embodiments, the heavy chain variable domain comprises a valine at a position corresponding to Kabat position 79. In some embodiments, the heavy chain variable domain comprises a threonine at a position corresponding to Kabat position 81. In some embodiments, the heavy chain variable domain comprises a methionine at a position corresponding to Kabat position 82. In some embodiments, the heavy chain variable domain comprises an asparagine at a position corresponding to Kabat position 82B. In some embodiments, the heavy chain variable domain comprises a methionine at a position corresponding to Kabat position 82C. In some embodiments, the heavy chain variable domain comprises a proline at a position corresponding to Kabat position 84. In some embodiments, the heavy chain variable domain comprises a valine at a position corresponding to Kabat position 85. In some embodiments, the heavy chain variable domain comprises a lysine at a position corresponding to Kabat position 108. In some embodiments, the heavy chain variable domain comprises a valine at a position corresponding to Kabat position 109.

[0096] In some embodiments, the heavy chain variable domain comprises a threonine or alanine at a position corresponding to Kabat position 10, a lysine at a position corresponding to Kabat position 11, a valine at a position corresponding to Kabat position 12, a threonine at a position corresponding to Kabat position 15, a threonine at a position corresponding to Kabat position 19, a threonine at a position corresponding to Kabat position 23, a proline at a position corresponding to Kabat position 41, an alanine at a position corresponding to Kabat position 44, a proline, serine or threonine at a position corresponding to Kabat position 61, an arginine at a position corresponding to Kabat position 66, a threonine at a position corresponding to Kabat position 70, a lysine at a position corresponding to Kabat position 75, a valine at a position corresponding to Kabat position 79, a threonine or lysine at a position corresponding to Kabat position 81, a methionine at a position corresponding to Kabat position 82, an asparagine at a position corresponding to Kabat position 82B, a methionine at a position corresponding to Kabat position 82C, a proline at a position corresponding to Kabat position 84, a valine at a position corresponding to Kabat position 85, a lysine at a position corresponding to Kabat position 108, or a valine at a position corresponding to Kabat position 109.

[0097] In some embodiments, the heavy chain variable domain comprises a threonine or alanine at a position corresponding to Kabat position 10, a lysine at a position corresponding to Kabat position 11, a valine at a position corresponding to Kabat position 12, a threonine at a position corresponding to Kabat position 15, a threonine at a position corresponding to Kabat position 19, a threonine at a position corresponding to Kabat position 23, a proline at a position corresponding to Kabat position 41, an alanine at a position corresponding to Kabat position 44, a proline, serine or threonine at a position corresponding to Kabat position 61, an arginine at a position corresponding to Kabat position 66, a threonine at a position corresponding to Kabat position 70, a lysine at a position corresponding to Kabat position 75, a valine at a position corresponding to Kabat position 79, a threonine or lysine at a position corresponding to Kabat position 81, a methionine at a position corresponding to Kabat position 82, an asparagine at a position corresponding to Kabat position 82B, a methionine at a position corresponding to Kabat position 82C, a proline at a position corresponding to Kabat position 84, a valine at a position corresponding to Kabat position 85, a lysine at a position corresponding to Kabat position 108, and a valine at a position corresponding to Kabat position 109.

[0098] In some embodiments, the heavy chain variable domain comprises a threonine or alanine at a position corresponding to Kabat position 10, a lysine at a position corresponding to Kabat position 11, a valine at a position corresponding to Kabat position 12, a threonine at a position corresponding to Kabat position 15, a threonine at a position corresponding to Kabat position 19, a threonine at a position corresponding to Kabat position 23, a proline at a position corresponding to Kabat position 41, an alanine at a position corresponding to Kabat position 44, a proline, serine or threonine at a position corresponding to Kabat position 61, an arginine at a position corresponding to Kabat position 66, a threonine at a position corresponding to Kabat position 70, a lysine at a position corresponding to Kabat position 75, a valine at a position corresponding to Kabat position 79, a threonine or lysine at a position corresponding to Kabat position 81, a methionine at a position corresponding to Kabat position 82, an asparagine at a position corresponding to Kabat position 82B, a methionine at a position corresponding to Kabat position 82C, a proline at a position corresponding to Kabat position 84, a valine at a position corresponding to Kabat position 85, a lysine corresponding to Kabat position 108, or a valine corresponding to Kabat position 109.

[0099] The recombinant proteins provided herein, including embodiments thereof (e.g., bispecific antibodies), may comprise one or more Fab' fragments. The recombinant proteins provided herein, including embodiments thereof (e.g., bispecific antibodies), may comprise a first antibody region and a second antibody region, and the first antibody region may be a first Fab' fragment, or the second antibody region may be a second Fab' fragment. When the recombinant proteins provided herein (e.g., bispecific antibodies) comprise a Fab' fragment, the recombinant protein may comprise a first antibody binding region and a second antibody binding region, each independently comprising a heavy chain (e.g., comprising a constant region and a variable region) and a light chain (e.g., comprising a constant region and a variable region). In some embodiments, the Fab' fragment comprises a humanized heavy chain (e.g., comprising a constant region and a variable region) and a humanized light chain (e.g., comprising a constant region and a variable region). Thus, in some embodiments, the first antibody region is a first Fab' fragment, or the second antibody region is a second Fab' fragment. In some embodiments, the first antibody region is a first Fab' fragment. In some embodiments, the second antibody region is a second Fab' fragment. In some embodiments, the first antibody region is a first Fab' fragment and the second antibody region is a second Fab' fragment.

[0100] The first antibody region or the second antibody region can be a first scFv or a second scFv, respectively. Single chain antibodies include a variable light chain and a variable heavy chain. Those skilled in the art will immediately understand that single chain antibodies, in contrast to immunoglobulin antibodies, include a single light chain and a single heavy chain, and include two identical pairs of polypeptide chains, each pair having one light chain and one heavy chain. Each light and heavy chain consists of two regions: a variable ("V") region (i.e., a variable light chain and a variable heavy chain) that are involved in binding the target antigen, and a constant ("C") region that interacts with other components of the immune system. The variable light chain and the variable heavy chain in a single chain antibody can be linked via a linker peptide. In some embodiments, the linker peptide comprises the sequence set forth in SEQ ID NO:37. In some embodiments, the linker peptide is the sequence set forth in SEQ ID NO:37. Examples of linker peptides for single chain antibodies are described in Bird, RE, Hardman, KD, Jacobson, JW, Johnson, S., Kaufman, BM, Lee, SM, Lee, T., Pope, SH, Riordan, GS, and Whitlow, M. (1988). Methods for generating scFv antibodies have been described. See Huse et al., Science 246:1275-1281 (1989); Ward et al., Nature 341:544-546 (1989); and Vaughan et al., Nature Biotech 14:309-314 (1996). Briefly, mRNA is isolated from B cells from immunized animals and cDNA is prepared. The cDNA is amplified using primers specific for the variable domains of immunoglobulin heavy and light chains. The PCR products are purified and the nucleic acid sequences are joined. If a linker peptide is required, a nucleic acid sequence encoding the peptide is inserted between the nucleic acid sequence of the heavy chain and the nucleic acid sequence of the light chain. The nucleic acid encoding the scFv is inserted into a vector and expressed in a suitable host cell.

[0101] In some embodiments, the first antibody region is a first single chain variable fragment or the second antibody region is a second single chain variable fragment. In some embodiments, the first antibody region is a first single chain variable fragment. In some embodiments, the second antibody region is a second single chain variable fragment. In some embodiments, the first antibody region is a first single chain variable fragment and the second antibody region is a second single chain variable fragment.

[0102] The ability of an antibody to bind to a particular epitope (e.g., BAFF-R) is determined by the equilibrium dissociation constant (K D The equilibrium dissociation constant (K D ) is the ratio of the dissociation rate (K-off) to the association rate (K-on) of the second antibody region capable of binding to the BAFF-R protein. It is expressed by the following formula: K D = K-off / K-on Thus, in some embodiments, the second antibody region has an equilibrium dissociation constant (K D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K) of less than about 4.5 nM. D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K) of less than about 4 nM. D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K) of less than about 3.5 nM. D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K) of less than about 3 nM. D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K) of less than about 2.5 nM. D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K DIn some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K) of less than about 1.5 nM. D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K) of less than about 0.5 nM. D ) can bind to the BAFF-R protein.

[0103] In some embodiments, the second antibody region has an equilibrium dissociation constant (K D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K D In some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K DIn some embodiments, the second antibody region can bind to the BAFF-R protein with an equilibrium dissociation constant (K D ) can bind to the BAFF-R protein.

[0104] In one embodiment, the K is less than about 4 nM. D In another embodiment, a recombinant protein capable of binding to BAFF-R with a K of less than about 4 nM is provided. D In some embodiments, the antibody does not induce BAFF-R activity.

[0105] The recombinant protein provided herein comprises a first antibody region capable of binding to an effector cell ligand. In some embodiments, the effector cell ligand is a CD3 protein. In some embodiments, the first antibody region comprises (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 74, CDR L2 as set forth in SEQ ID NO: 75, and CDR L3 as set forth in SEQ ID NO: 76, and (b) a heavy chain variable domain comprising CDR H1 as set forth in SEQ ID NO: 77, CDR H2 as set forth in SEQ ID NO: 78, and CDR H3 as set forth in SEQ ID NO: 79.

[0106] In some embodiments, the first antibody region comprises (a) a light chain variable domain comprising CDR L1 set forth in SEQ ID NO: 81, CDR L2 set forth in SEQ ID NO: 82, and CDR L3 set forth in SEQ ID NO: 83, and (b) a heavy chain variable domain comprising CDR H1 set forth in SEQ ID NO: 84, CDR H2 set forth in SEQ ID NO: 85, and CDR H3 set forth in SEQ ID NO: 86.

[0107] In some embodiments, the first antibody region is a first single chain variable fragment (scFv). In some embodiments, the first scFv comprises the sequence of SEQ ID NO: 80 or SEQ ID NO: 87. In some embodiments, the first scFv comprises the sequence of SEQ ID NO: 80. In some embodiments, the first scFv comprises the sequence of SEQ ID NO: 87. In some embodiments, the first scFv is the sequence of SEQ ID NO: 80 or SEQ ID NO: 87. In some embodiments, the first scFv is the sequence of SEQ ID NO: 80. In some embodiments, the first scFv is the sequence of SEQ ID NO: 87.

[0108] In some embodiments, the second antibody region binds to a BAFF-R protein. In some embodiments, the BAFF-R protein is a human BAFF-R protein. In some embodiments, the BAFF-R protein is encoded by a nucleic acid sequence identified by NCBI Gene ID number 115650. In some embodiments, the BAFF-R protein forms part of a cell. In some embodiments, the BAFF-R protein is expressed on the surface of the cell. In some embodiments, the cell is a lymphocytic cell. In some embodiments, the cell is a B cell. In some embodiments, the cell is a cancer cell. In some embodiments, the cancer cell is a lymphoma cell.

[0109] In one embodiment, the recombinant protein comprises a first antibody region comprising: (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 74, CDR L2 as set forth in SEQ ID NO: 75, and CDR L3 as set forth in SEQ ID NO: 76; and (b) a heavy chain variable domain comprising CDR H1 as set forth in SEQ ID NO: 77, CDR H2 as set forth in SEQ ID NO: 78, and CDR H3 as set forth in SEQ ID NO: 79; and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO: 7 and a heavy chain variable domain having the sequence of SEQ ID NO: 10.

[0110] In one embodiment, the recombinant protein comprises a first antibody region comprising (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 74, CDR L2 as set forth in SEQ ID NO: 75, and CDR L3 as set forth in SEQ ID NO: 76, and (b) a heavy chain variable domain comprising CDR H1 as set forth in SEQ ID NO: 77, CDR H2 as set forth in SEQ ID NO: 78, and CDR H3 as set forth in SEQ ID NO: 79, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO: 8 and a heavy chain variable domain having the sequence of SEQ ID NO: 11.

[0111] In one embodiment, the recombinant protein comprises a first antibody region comprising (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 74, CDR L2 as set forth in SEQ ID NO: 75, and CDR L3 as set forth in SEQ ID NO: 76, and (b) a heavy chain variable domain comprising CDR H1 as set forth in SEQ ID NO: 77, CDR H2 as set forth in SEQ ID NO: 78, and CDR H3 as set forth in SEQ ID NO: 79, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO: 9 and a heavy chain variable domain having the sequence of SEQ ID NO: 12.

[0112] In one embodiment, the recombinant protein comprises a first antibody region comprising (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 81, CDR L2 as set forth in SEQ ID NO: 82, and CDR L3 as set forth in SEQ ID NO: 83, and (b) a heavy chain variable domain comprising CDR H1 as set forth in SEQ ID NO: 84, CDR H2 as set forth in SEQ ID NO: 85, and CDR H3 as set forth in SEQ ID NO: 86, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO: 7 and a heavy chain variable domain having the sequence of SEQ ID NO: 10.

[0113] In one embodiment, the recombinant protein comprises a first antibody region comprising (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 81, CDR L2 as set forth in SEQ ID NO: 82, and CDR L3 as set forth in SEQ ID NO: 83, and (b) a heavy chain variable domain comprising CDR H1 as set forth in SEQ ID NO: 84, CDR H2 as set forth in SEQ ID NO: 85, and CDR H3 as set forth in SEQ ID NO: 86, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO: 8 and a heavy chain variable domain having the sequence of SEQ ID NO: 11.

[0114] In one embodiment, the recombinant protein comprises a first antibody region comprising (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 81, CDR L2 as set forth in SEQ ID NO: 82, and CDR L3 as set forth in SEQ ID NO: 83, and (b) a heavy chain variable domain comprising CDR H1 as set forth in SEQ ID NO: 84, CDR H2 as set forth in SEQ ID NO: 85, and CDR H3 as set forth in SEQ ID NO: 86, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO: 9 and a heavy chain variable domain having the sequence of SEQ ID NO: 12.

[0115] In one embodiment, the recombinant protein comprises a first antibody region comprising (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 74, CDR L2 as set forth in SEQ ID NO: 75, and CDR L3 as set forth in SEQ ID NO: 76, and (b) a heavy chain variable domain comprising CDR H1 as set forth in SEQ ID NO: 77, CDR H2 as set forth in SEQ ID NO: 78, and CDR H3 as set forth in SEQ ID NO: 79, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO: 44 and a heavy chain variable domain having the sequence of SEQ ID NO: 47.

[0116] In one embodiment, the recombinant protein comprises a first antibody region comprising (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 74, CDR L2 as set forth in SEQ ID NO: 75, and CDR L3 as set forth in SEQ ID NO: 76, and (b) a heavy chain variable domain comprising CDR H1 as set forth in SEQ ID NO: 77, CDR H2 as set forth in SEQ ID NO: 78, and CDR H3 as set forth in SEQ ID NO: 79, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO: 45 and a heavy chain variable domain having the sequence of SEQ ID NO: 48.

[0117] In one embodiment, the recombinant protein comprises a first antibody region comprising (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 74, CDR L2 as set forth in SEQ ID NO: 75, and CDR L3 as set forth in SEQ ID NO: 76, and (b) a heavy chain variable domain comprising CDR H1 as set forth in SEQ ID NO: 77, CDR H2 as set forth in SEQ ID NO: 78, and CDR H3 as set forth in SEQ ID NO: 79, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO: 46 and a heavy chain variable domain having the sequence of SEQ ID NO: 49.

[0118] In one embodiment, the recombinant protein comprises a first antibody region comprising (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 81, CDR L2 as set forth in SEQ ID NO: 82, and CDR L3 as set forth in SEQ ID NO: 83, and (b) a heavy chain variable domain comprising CDR H1 as set forth in SEQ ID NO: 84, CDR H2 as set forth in SEQ ID NO: 85, and CDR H3 as set forth in SEQ ID NO: 86, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO: 44 and a heavy chain variable domain having the sequence of SEQ ID NO: 47.

[0119] In one embodiment, the recombinant protein comprises a first antibody region comprising (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 81, CDR L2 as set forth in SEQ ID NO: 82, and CDR L3 as set forth in SEQ ID NO: 83, and (b) a heavy chain variable domain comprising CDR H1 as set forth in SEQ ID NO: 84, CDR H2 as set forth in SEQ ID NO: 85, and CDR H3 as set forth in SEQ ID NO: 86, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO: 45 and a heavy chain variable domain having the sequence of SEQ ID NO: 48.

[0120] In one embodiment, the recombinant protein comprises a first antibody region comprising (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 81, CDR L2 as set forth in SEQ ID NO: 82, and CDR L3 as set forth in SEQ ID NO: 83, and (b) a heavy chain variable domain comprising CDR H1 as set forth in SEQ ID NO: 84, CDR H2 as set forth in SEQ ID NO: 85, and CDR H3 as set forth in SEQ ID NO: 86, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO: 46 and a heavy chain variable domain having the sequence of SEQ ID NO: 49.

[0121] In one embodiment, the recombinant protein comprises a first antibody region having the sequence of SEQ ID NO:80, a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO:7, and a heavy chain variable domain having the sequence of SEQ ID NO:10.

[0122] In one embodiment, the recombinant protein comprises a first antibody region having the sequence of SEQ ID NO:80, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO:8, and a heavy chain variable domain having the sequence of SEQ ID NO:11.

[0123] In one embodiment, the recombinant protein comprises a first antibody region having the sequence of SEQ ID NO:80, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO:9, and a heavy chain variable domain having the sequence of SEQ ID NO:12.

[0124] In one embodiment, the recombinant protein comprises a first antibody region having the sequence of SEQ ID NO:87, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO:7, and a heavy chain variable domain having the sequence of SEQ ID NO:10.

[0125] In one embodiment, the recombinant protein comprises a first antibody region having the sequence of SEQ ID NO:87, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO:8, and a heavy chain variable domain having the sequence of SEQ ID NO:11.

[0126] In one embodiment, the recombinant protein comprises a first antibody region having the sequence of SEQ ID NO:87, a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO:9, and a heavy chain variable domain having the sequence of SEQ ID NO:12.

[0127] In one embodiment, the recombinant protein comprises a first antibody region having the sequence of SEQ ID NO:80, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO:44, and a heavy chain variable domain having the sequence of SEQ ID NO:47.

[0128] In one embodiment, the recombinant protein comprises a first antibody region having the sequence of SEQ ID NO:80, a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO:45, and a heavy chain variable domain having the sequence of SEQ ID NO:48.

[0129] In one embodiment, the recombinant protein comprises a first antibody region having the sequence of SEQ ID NO:80, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO:46, and a heavy chain variable domain having the sequence of SEQ ID NO:49.

[0130] In one embodiment, the recombinant protein comprises a first antibody region having the sequence of SEQ ID NO:87, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO:44, and a heavy chain variable domain having the sequence of SEQ ID NO:47.

[0131] In one embodiment, the recombinant protein comprises a first antibody region having the sequence of SEQ ID NO:87, a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO:45, and a heavy chain variable domain having the sequence of SEQ ID NO:48.

[0132] In one embodiment, the recombinant protein comprises a first antibody region having the sequence of SEQ ID NO:87, and a second antibody region comprising a light chain variable domain having the sequence of SEQ ID NO:46, and a heavy chain variable domain having the sequence of SEQ ID NO:49.

[0133] III. Pharmaceutical Compositions The agents of the present invention (e.g., recombinant proteins provided herein) are often administered as pharmaceutical compositions, i.e., containing an active therapeutic agent and various other pharma- ceutically acceptable ingredients. See Remington's Pharmaceutical Science (15th ed., Mack Publishing Company, Easton, Pennsylvania, 1980). The preferred form varies depending on the intended mode of administration and therapeutic application. The composition may also contain pharma- ceutically acceptable non-toxic carriers or diluents, defined as media commonly used to formulate pharmaceutical compositions for animal or human administration, depending on the desired formulation. The diluents are selected so as not to affect the biological activity of the combination. Examples of such diluents are distilled water, phosphate-buffered saline, Ringer's solution, dextrose solution, and Hank's solution. In addition, the pharmaceutical composition or formulation may also contain other carriers, adjuvants, or non-toxic, non-therapeutic, non-immunogenic stabilizers, and the like.

[0134] The composition may be administered for therapeutic or prophylactic treatment. In therapeutic applications, the composition is administered to a patient suffering from a disease (e.g., cancer) in a "therapeutically effective dose". Amounts effective for this use will vary depending on the severity of the disease and the general health of the patient. Single or multiple administrations of the composition may be administered as needed and at a dosage and frequency tolerated by the patient. In the present invention, a "patient" or "subject" includes both humans and other animals, particularly mammals. Thus, the method is applicable to both human treatment and veterinary applications. In a preferred embodiment, the patient is a mammal, preferably a primate, and in a most preferred embodiment, the patient is human.

[0135] Formulations suitable for oral administration consist of (a) liquid solutions, e.g., of the antibodies provided herein suspended in a diluent such as water, saline, or PEG 400, (b) capsules, sachets, or tablets, each containing a predetermined amount of the active ingredient as a liquid, solid, granules, or gelatin, (c) suspensions in suitable liquids, and (d) suitable emulsions. Tablet forms may contain one or more of lactose, sucrose, mannitol, sorbitol, calcium phosphate, corn starch, potato starch, microcrystalline cellulose, gelatin, colloidal silicon dioxide, talc, magnesium stearate, stearic acid, and other excipients, colorants, fillers, binders, diluents, buffers, wetting agents, preservatives, flavoring agents, dyes, disintegrants, and pharma- ceutically compatible carriers. Lozenge dosage forms can contain the active ingredient in a flavoring (e.g., sucrose) or the lozenge can contain the active ingredient in an inert base such as gelatin and glycerin or sucrose and acacia emulsion, gel, etc., and can contain, in addition to the active ingredient, carriers known in the art.

[0136] Pharmaceutical compositions may also include large, slowly metabolized macromolecules such as proteins, polysaccharides such as chitosan, polylactic acids, polyglycolic acids and copolymers (such as latex-functionalized Sepharose™, agarose, cellulose, etc.), polymeric amino acids, amino acid copolymers, and lipid aggregates (such as oil droplets and liposomes). Additionally, these carriers may function as immunostimulating agents (i.e., adjuvants).

[0137] The preparation suitable for rectal administration includes, for example, suppositories that consist of nucleic acid packaged with a suppository base.Suitable suppository bases include natural or synthetic triglycerides or paraffin hydrocarbons.In addition, it is also possible to use gelatin rectal capsules that consist of the combination of selected compound with bases that include, for example, liquid triglycerides, polyethylene glycols, and paraffin hydrocarbons.

[0138] Formulations suitable for parenteral administration, such as by intra-articular (intra-articular), intravenous, intramuscular, intratumoral, intradermal, intraperitoneal, and subcutaneous routes, can include aqueous and non-aqueous isotonic sterile injection solutions, which can include antioxidants, buffers, bacteriostats, and solutes that render the formulation isotonic with the blood of the intended recipient, as well as aqueous and non-aqueous sterile suspensions, which can include suspending agents, solubilizing agents, thickening agents, stabilizers, and preservatives. In the practice of the invention, compositions can be administered, for example, by intravenous infusion, orally, topically, intraperitoneally, intravesically, or intrathecally. Parenteral, oral, and intravenous administration are preferred methods of administration. Formulations of the compounds can be provided in unit-dose or multi-dose sealed containers, such as ampoules and vials.

[0139] Injection solutions and suspensions can be prepared from sterile powders, granules, and tablets of the kind previously described. Cells transduced with nucleic acid for ex vivo therapy can also be administered intravenously or parenterally as described above.

[0140] The pharmaceutical preparation is preferably in unit dosage form. In such form, the preparation is subdivided into unit doses containing appropriate amounts of the active ingredient. The unit dosage form can be a packaged preparation, the package containing discrete quantities of the preparation, such as packeted tablets, capsules, and powders in vials or ampoules. The unit dosage form can also be a capsule, tablet, cachet, or lozenge itself, or the appropriate number of any of these in packaged form. The composition can also contain other compatible therapeutic agents, if desired.

[0141] Concomitant administration contemplates simultaneous administration, using separate formulations or a single pharmaceutical formulation, or sequential administration in any order, preferably wherein there is a period of time during which both (or all) active agents exert their biological activity simultaneously.

[0142] Effective amounts of the compositions provided herein will vary depending on many different factors, including the means of administration, the target site, the physiological condition of the patient, whether the patient is human or animal, other drugs administered, and whether the treatment is prophylactic or therapeutic, however, one of skill in the art will readily recognize appropriate and / or equivalent dosages by looking to the dosages of approved compositions for treating and preventing cancer as a guide.

[0143] In one aspect, there is provided a pharmaceutical composition comprising a therapeutically effective amount of a recombinant protein provided herein, including embodiments thereof, and a pharma- ceutically acceptable excipient.

[0144] The therapeutically effective amount provided herein refers to an amount effective to achieve its intended purpose. The actual amount effective for a particular application will vary, inter alia, depending on the condition being treated. When administered in a method for treating a disease, the pharmaceutical compositions described herein will contain an amount of active recombinant protein (e.g., bispecific antibody) effective to achieve a desired result, such as, for example, modulating the activity of a target molecule (e.g., BAFF-R), activating an effector cell (e.g., T cell), and / or reducing, eliminating, or slowing the progression of a disease symptom (e.g., cancer, autoimmune disease). Determining a therapeutically effective amount of the recombinant protein (e.g., bispecific antibody) provided herein is well within the capabilities of one of ordinary skill in the art, especially in light of the detailed disclosure herein.

[0145] IV. Treatment method In one aspect, a method of treating cancer in a subject in need thereof is provided, the method comprising administering to the subject a therapeutically effective amount of a recombinant protein (e.g., a bispecific antibody) described herein, including embodiments thereof, thereby treating the cancer in the subject. In some embodiments, the cancer is lymphoma, leukemia, or myeloma. In some embodiments, the cancer is lymphoma. In some embodiments, the lymphoma is mantle cell lymphoma, follicular lymphoma, diffuse large B-cell lymphoma, marginal zone lymphoma, or Burkitt lymphoma. In some embodiments, the lymphoma is mantle cell lymphoma. In some embodiments, the lymphoma is follicular lymphoma. In some embodiments, the lymphoma is diffuse large B-cell lymphoma. In some embodiments, the lymphoma is marginal zone lymphoma. In some embodiments, the lymphoma is Burkitt lymphoma.

[0146] In some embodiments, the cancer is leukemia. In some embodiments, the leukemia is lymphoblastic leukemia, chronic lymphocytic leukemia, or hairy cell leukemia. In some embodiments, the leukemia is lymphoblastic leukemia. In some embodiments, the leukemia is chronic lymphocytic leukemia. In some embodiments, the leukemia is hairy cell leukemia.

[0147] In some embodiments, the cancer is a myeloma. In some embodiments, the myeloma is multiple myeloma.

[0148] In some embodiments, the method further comprises administering a second therapeutic agent to the subject. In some embodiments, the therapeutic agent is a chimeric monoclonal antibody capable of binding to the CD20 antigen. In some embodiments, the therapeutic agent is rituximab. The term "rituximab" refers in its usual sense to a monoclonal antibody against the protein CD20, identified by the ATC code L01XC02.

[0149] In another aspect, a method of treating an autoimmune disease in a subject in need thereof is provided. The method comprises administering to the subject a therapeutically effective amount of a recombinant protein (e.g., a bispecific antibody) provided herein, including embodiments thereof, thereby treating the autoimmune disease in the subject. In some embodiments, the autoimmune disease is rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, glomerulonephritis, Sjogren's syndrome, or autoimmune hemolytic anemia. In some embodiments, the autoimmune disease is rheumatoid arthritis. In some embodiments, the autoimmune disease is systemic lupus erythematosus. In some embodiments, the autoimmune disease is multiple sclerosis. In some embodiments, the autoimmune disease is glomerulonephritis. In some embodiments, the autoimmune disease is Sjogren's syndrome. In some embodiments, the autoimmune disease is autoimmune hemolytic anemia. In some embodiments, the method further comprises administering to the subject a second therapeutic agent.

[0150] The therapeutically effective amount provided herein refers to an amount effective to achieve its intended purpose. The actual amount effective for a particular application will vary, inter alia, depending on the condition being treated. When administered in a method for treating a disease, the pharmaceutical compositions described herein will contain an active recombinant protein (BAFF-R bispecific antibody) provided herein, including embodiments thereof, in an amount effective to achieve a desired result, such as, for example, modulating the activity of a target molecule (e.g., BAFF-R), activating effector cells, and / or reducing, eliminating, or slowing the progression of a disease symptom (e.g., cancer, autoimmune disease). Determining a therapeutically effective amount of the recombinant protein (e.g., BAFF-R bispecific antibody) provided herein is well within the capabilities of one of ordinary skill in the art, especially in light of the detailed disclosure herein.

[0151] Acceptable carriers, excipients or stabilizers are non-toxic to recipients at the dosages and concentrations employed and typically include buffers such as phosphate, citrate, or acetate at a pH of 5.0 to 8.0, optionally 6.0 to 7.0, salts such as sodium chloride, potassium chloride to render them isotonic, antioxidants, preservatives, low molecular weight polypeptides, proteins, hydrophilic polymers such as polysorbate 80, amino acids such as glycine, carbohydrates, chelating agents, sugars, and other standard components known to those of skill in the art {Remington: The Science and Practice of Pharmacy, 22nd Edition, Loyd V. Allen et al., editors, Pharmaceutical Press (2012)). The mAb may be present in a concentration of 0.1 to 100 mg / ml, e.g., 1 to 10 mg / ml, or 10 to 50 mg / ml, e.g., 5, 10, 20, 30, 40, 50, or 60 mg / ml.

[0152] Pharmaceutical compositions comprising the recombinant proteins (BAFF-R bispecific antibodies) presented herein, including embodiments thereof, can be administered by various methods known in the art. The route and / or mode of administration will vary depending on the desired results. Optionally, administration is intravenous, intramuscular, intraperitoneal, or subcutaneous, or administered proximal to the target site. The pharmaceutically acceptable excipient may be suitable for intravenous, intramuscular, subcutaneous, parenteral, spinal or epidermal administration (e.g., by injection or infusion).

[0153] Pharmaceutical compositions of the recombinant proteins (BAFF-R bispecific antibodies) presented herein, including embodiments thereof, can be prepared according to methods well known and routinely practiced in the art. See, for example, Remington: The Science and Practice of Pharmacy, 22nd ed., Loyd V. Allen et al., editors, Pharmaceutical Press (2012), and Sustained and Controlled Release Drug Delivery Systems, J R. Robinson, ed., Marcel Dekker, Inc., New York, 1978. Pharmaceutical compositions are preferably manufactured under GMP conditions. Typically, a therapeutically effective amount or therapeutically effective amount of the recombinant proteins (BAFF-R bispecific antibodies) presented herein, including embodiments thereof, is used in the pharmaceutical composition. The recombinant proteins (BAFF-R bispecific antibodies) presented herein, including embodiments thereof, can be formulated into pharma- ceutically acceptable dosage forms by conventional methods known to those skilled in the art. Dosage regimens are adjusted to provide the optimum desired response (e.g., therapeutic response). For example, it may be administered in a single bolus dose, or in several divided doses administered over time, or the dose may be relatively reduced or increased as indicated by the exigencies of the therapeutic situation. It may be advantageous to formulate the recombinant protein (BAFF-R bispecific antibody) provided herein, including its embodiments, in combination with other therapies or drugs. For ease of administration and uniformity of dosage, it may be advantageous to formulate parenteral compositions in dosage unit form. As used herein, dosage unit form refers to physically discrete units suitable as a unitary dosage for the subject to be treated, each unit containing a predetermined amount of the recombinant protein (BAFF-R bispecific antibody) provided herein, including its embodiments, together with the necessary pharmaceutical excipients, calculated to produce the desired therapeutic effect.

[0154] The actual dosage of the active ingredient in the pharmaceutical composition may vary such that for a particular patient, composition, and method of administration, an amount of the active ingredient effective to obtain the desired therapeutic response is received in a manner that is non-toxic to the patient. The dosage level selected will depend on a variety of pharmacokinetic factors, including the activity of the particular composition employed, the route of administration, the time of administration, the rate of excretion of the particular antibody employed, the duration of treatment, other drugs, compounds and / or substances used in combination with the particular composition employed, factors such as the age, sex, weight, symptoms, general health and previous medical history of the patient being treated.

[0155] A physician or veterinarian may begin administration of the recombinant protein (BAFF-R bispecific antibody) used in the pharmaceutical compositions provided herein, including embodiments thereof, at a level lower than that required to achieve the desired therapeutic effect, and gradually increase the dose until the desired effect is achieved. In general, the effective amount of the composition may vary depending on many different factors, including the particular disease or condition being treated, the means of administration, the target site, the physiological condition of the patient, whether the patient is human or animal, administration of other agents, and whether the treatment is prophylactic or therapeutic. Treatment dosages should be titrated to optimize safety and efficacy. When administering bispecific antibodies, dosages range from about 0.0001 to 100 mg / kg, more commonly 0.01 to 5 mg / kg, of the host body weight. For example, dosages may be 1 mg / kg body weight or 10 mg / kg body weight, or within the range of 1 to 10 mg / kg. Exemplary treatment regimens involve administration once every 2 or 3 weeks, or once a month, or once every 3 to 6 months.

[0156] The recombinant proteins (BAFF-R bispecific antibodies) provided herein, including embodiments thereof, can be administered multiple times. The intervals between administrations can be weekly, monthly, or yearly. The intervals can also be irregular, depending on the patient's blood levels of the bispecific antibody as indicated by measurements. In some methods, the dosage is adjusted to achieve a plasma antibody concentration of 1-1000 μg / ml, and in some methods, to achieve a plasma antibody concentration of 25-300 μg / ml.

[0157] Alternatively, the recombinant protein (BAFF-R bispecific antibody) provided herein, including its embodiments, can be administered as a sustained release formulation, in which case less frequent administration is required. The dosage and frequency will depend on the half-life of the recombinant protein (BAFF-R bispecific antibody) provided herein, including its embodiments, in the patient. The dosage and frequency may vary depending on whether the treatment is preventative or therapeutic. In preventative applications, relatively low doses are administered relatively infrequently over an extended period of time. Some patients continue to receive treatment for the rest of their lives. In therapeutic applications, relatively high doses may be required at relatively short intervals until the progression of the disease is reduced or terminated, preferably until the patient shows partial or complete improvement of the symptoms of the disease. The patient can then be administered a prophylactic regimen. EXAMPLES

[0158] Working Example Bispecific T cell engagers (BiTEs) are a class of bispecific monoclonal antibodies that can be used as targeted immunotherapeutic agents. Unlike traditional monoclonal antibodies, BiTE antibodies are composed of two unique variable fragments arranged as two single-chain variable fragments (scFvs); one engages the T cell via the CD3 molecule and the other targets a cell surface antigen on the tumor cell. Targeting the two molecules not only allows the T cell to bind to the tumor cell but also activates the T cell via CD3 signaling. The activated T cell exerts cytotoxic activity against the tumor cell.

[0159] BAFF-R BiTEs (bispecific antibodies) were constructed using scFvs derived from the heavy and light chains of a previously developed humanized anti-BAFF-R monoclonal antibody described in the aforementioned International Application PCT / US2017 / 036178. Preliminary testing of BAFF-R BiTEs demonstrated strong specific binding to BAFF-R and human T cells. BAFF-R BiTEs can elicit strong T cell responses against lymphoma and leukemia lines expressing BAFF-R in vitro. Healthy donor B cells were also subject to cytotoxicity due to normal BAFF-R expression in the presence of BAFF-R BiTEs and T cell effectors.

[0160] BAFF-R BiTE bispecific antibodies were generated by the knob-into-hole method. To promote heterodimer formation, a knob-into-hole structure was applied to the bispecific antibodies. Gels were run under reducing and non-reducing conditions for BAFF-R BiTE (H90Bi). Controls included a control / irrelevant BiTE (Cont.Bi, 4-4Bi) and the original humanized BAFF-R antibody (H90 Ab, also referred to herein as C90).

[0161] The binding specificity of the bispecific antibody was measured using FACS histograms of BAFF-R / CD3 bispecific antibody (H90 BiTE) binding to wild-type mouse fibroblast L cells, modified BAFF-R expressing L cells (B2D L cells), and T cells isolated from healthy donors, as described in Figure 2. Antibody concentrations ranged from 0.05 μg to 5 μg. An irrelevant BiTE antibody was used as a control. An anti-human IgG antibody was used as the secondary antibody. BAFF-R BiTE binding was further assessed using FACS plots and confirmed to bind independently to BAFF-R and T cells, as shown in Figure 8A-C.

[0162] The specific cytotoxicity of the bispecific antibodies was measured against BAFF-R expressing L cells. The plot shows the specific cytotoxicity percentage calculated from the chromium release assay (Figure 3). BAFF-R / CD3 bispecific antibodies (H90BiTE) were incubated for 4 h with chromium-labeled target wild-type or BAFF-R expressing L cells and effector CD8 T cells isolated from a single healthy donor at an effector-to-target (E:T) ratio of 10:1. Controls included control / irrelevant BiTE (Cont.Bi, 4-4Bi), the original humanized BAFF-R antibody (H90Ab), or CD8 T cells alone (no antibody).

[0163] The cytotoxicity of the bispecific antibodies was measured against malignant B cell lines. The plot shows the specific cytotoxicity percentage calculated from the chromium release assay against various malignant B cell lines as shown in (Figure 4). The BAFF-R / CD3 bispecific antibody (H90BiTE) was incubated with chromium-labeled target cell lines and effector CD8 T cells isolated from a single healthy donor at an effector-to-target (E:T) ratio of 10:1 for 4 h. Controls included control / irrelevant BiTE (Cont.Bi, 4-4Bi), the original humanized BAFF-R antibody (H90Ab), or CD8 T cells only (no antibody).

[0164] Dose-dependent cytotoxicity of the bispecific antibodies was measured. The plot shows the specific cytotoxicity percentage calculated from chromium release assay against JeKo-1 mantle cell lymphoma and normal isolated B cells (Figure 5). Various antibody concentrations of BAFF-R / CD3 bispecific antibody (H90BiTE) were incubated with chromium-labeled target JeKo-1 or normal B cells and effector CD8 T cells isolated from a single healthy donor at an effector-to-target (E:T) ratio of 10:1 for 4 h. Controls included control / irrelevant BiTE (Cont.Bi, 4-4Bi), original humanized BAFF-R antibody (H90Ab), or CD8 T cells alone (no antibody).

[0165] An exemplary treatment schedule for treating mice with BAFF-R BiTEs using the Z-138MCL tumor mouse model is illustrated in the schematic diagram of Figure 6. Mice were treated to evaluate the efficacy of the BiTEs in suppressing tumor growth. The effect of administration of BAFF-R BiTEs, control T cells, and PBS on tumor growth in these animals is shown in Figure 7.

[0166] Unofficial sequence listing Humanized C90 / H90 CDR L1: ESVDNYGIS (SEQ ID NO: 1)

[0167] Humanized C90 / H90 CDR L2: AAS (SEQ ID NO:2)

[0168] Humanized C90 / H90 CDR L3: QQSKEVPWT (SEQ ID NO: 3)

[0169] Humanized C90 / H90 CDR H1: GDSITSGY (SEQ ID NO: 4)

[0170] Humanized C90 / H90 CDR H2: ISYSGST (SEQ ID NO:5)

[0171] Humanized C90 / H90 CDR H3: ASPNYPFYAMDY (SEQ ID NO: 6)

[0172] Humanized C90-1 light chain variable domain protein sequence METDTLLLWVLLLWVPGSTGEIVLTQSPATLSLSPGERATLSCRASESVDNYGISFLNWFQQKPGQAPRLLIYAASNRATGIPARFSGSGSGTDFTLTISSLEPEDFAVYYCQQSKEVPWTFGGGTKVEIKRTV (SEQ ID NO: 7)

[0173] Humanized C90-2 light chain variable domain protein sequence METDTLLLWVLLLWVPGSTGDIVLTQSPATLSLSPGERATLSCRASESVDNYGISFMNWFQQKPGQAPRLLIYAASNRATGIPARFSGSGSGTDFTLTISSLEPEDFAVYYCQQSKEVPWTFGGGTKVEIKRTV (SEQ ID NO: 8)

[0174] Humanized C90-3 light chain variable domain protein sequence METDTLLLWVLLLWVPGSTGDIVMTQSPSSLSASVGDRVTITCRASESVDNYGISFMNWFQQKPGKAPKLLIYAASNLGSGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCQQSKEVPWTFGQGTKVEIKRTV (SEQ ID NO: 9)

[0175] Humanized C90-1 heavy chain variable domain protein sequence MDPKGSLSWRILLFLSLAFELSYGQVQLQESGPGLVKPSQTLSLTCTVSGDSITSGYWNWIRQHPGKGLEYIGYISYSGSTYYNPSLKSRVTISRDTSKNQFSLKLSSVTAADTAVYYCASPNYPFYAMDYWGQGTLVTVSS (SEQ ID NO: 10)

[0176] Humanized C90-2 heavy chain variable domain protein sequence MDPKGSLSWRILLFLSLAFELSYGEVQLQESGPGLVKPSQTLSLTCTVSGDSITSGYWNWIRQHPGKGLEYIGYISYSGSTYYNPSLKSRVTISRDTSKNQYSLKLSSVTAADTAVYYCASPNYPFYAMDYWGQGTLVTVSS (SEQ ID NO: 11)

[0177] Humanized C90-3 heavy chain variable domain protein sequence MDPKGSLSWRILLFLSLAFELSYGEVQLQESGPGLVKPSETLSLTCSVSGDSITSGYWNWIRQPPGKGLEYIGYISYSGSTYYNPSLKSRVTISRDTSKNQYSLRLSSVTAADTALYYCASPNYPFYAMDYWGQGTRVTVSS (SEQ ID NO: 12)

[0178] Humanized C90-1 FR L1: METDTLLLWVLLLWVPGSTGEIVLTQSPATLSLSPGERATLSCRAS (SEQ ID NO: 13)

[0179] Humanized C90-1 FR L2: FLNWFQQKPGQAPRLLIY (SEQ ID NO: 14)

[0180] Humanized C90-1 FR L3: NRATGIPARFSGSGSGTDFTLTISSLEPEDFAVYYC (SEQ ID NO: 15)

[0181] Humanized C90-1 FR L4: FGGGTKVEIKRTV (SEQ ID NO: 16)

[0182] Humanized C90-2 FR L1: METDTLLLWVLLLWVPGSTGDIVLTQSPATLSLSPGERATLSCRAS (SEQ ID NO: 17)

[0183] Humanized C90-2 FR L2: FMNWFQQKPGQAPRLLIY (SEQ ID NO: 18)

[0184] Humanized C90-2 FR L3: NRATGIPARFSGSGSGTDFTLTISSLEPEDFAVYYC (SEQ ID NO: 19)

[0185] Humanized C90-2 FR L4: FGGGTKVEIKRTV (SEQ ID NO: 20)

[0186] Humanized C90-3 FR L1: METDTLLLWVLLLWVPGSTGDIVMTQSPSSLSASVGDRVTITCRAS (SEQ ID NO: 21)

[0187] Humanized C90-3 FR L2: FMNWFQQKPGKAPKLLIY (SEQ ID NO: 22)

[0188] Humanized C90-3 FR L3: NLGSGVPSRFSGSGSGTDFTLTISSLQPEDFATYYC (SEQ ID NO: 23)

[0189] Humanized C90-3 FR L4: FGQGTKVEIKRTV (SEQ ID NO: 24)

[0190] Humanized C90-1 FR H1: MDPKGSLSWRILLFLSLAFELSYGQVQLQESGPGLVKPSQTLSLTCTVS (SEQ ID NO: 25)

[0191] Humanized C90-1 FR H2: WNWIRQHPGKGLEYIGY (SEQ ID NO: 26)

[0192] Humanized C90-1 FR H3: YYNPSLKSRVTISRDTSKNQFSLKLSSVTAADTAVYYC (SEQ ID NO: 27)

[0193] Humanized C90-1 FR H4:WGQGTLVTVSS (SEQ ID NO:28)

[0194] Humanized C90-2 FR H1: MDPKGSLSWRILLFLSLAFELSYGEVQLQESGPGLVKPSQTLSLTCTVS (SEQ ID NO: 29)

[0195] Humanized C90-2 FR H2: WNWIRQHPGKGLEYIGY (SEQ ID NO: 30)

[0196] Humanized C90-2 FR H3: YYNPSLKSRVTISRDTSKNQYSLKLSSVTAADTAVYYC (SEQ ID NO: 31)

[0197] Humanized C90-2 FR H4:WGQGTLVTVSS (SEQ ID NO:32)

[0198] Humanized C90-3 FR H1: MDPKGSLSWRILLFLSLAFELSYGEVQLQESGPGLVKPSETLSLTCSVS (SEQ ID NO: 33)

[0199] Humanized C90-3 FR H2: WNWIRQPPGKGLEYIGY (SEQ ID NO: 34)

[0200] Humanized C90-3 FR H3: YYNPSLKSRVTISRDTSKNQYSLRLSSVTAADTALYYC (SEQ ID NO: 35)

[0201] Humanized C90-3 FR H4:WGQGTRVTVSS (SEQ ID NO:36)

[0202] Humanized C90 or C55 linker: GGGSGGGSGGGS (SEQ ID NO: 37)

[0203] Humanized C55 CDR L1: QDISNY (SEQ ID NO: 38)

[0204] Humanized C55 CDR L2: YTS (SEQ ID NO: 39)

[0205] Humanized C55 CDR L3: HQFSELPWT (SEQ ID NO: 40)

[0206] Humanized C55 CDR H1: GFSLSTSGMG (SEQ ID NO: 41)

[0207] Humanized C55 CDR H2: IWWDDDK (SEQ ID NO: 42)

[0208] Humanized C55 CDR H3: ARSFGYGLDY (SEQ ID NO: 43)

[0209] Humanized C55-1 light chain variable domain protein sequence METDTLLLWVLLLWVPGSTGDIQMTQSPSSLSASVGDRVTITCQASQDISNYLNWYQQKPGKAPKLLIYYTSSLHTGVPSRFSGSGSGTDYTFTISSLQPEDIATYYCHQFSELPWTFGGGTKVEIKRTV (SEQ ID NO: 44)

[0210] Humanized C55-2 light chain variable domain protein sequence METDTLLLWVLLLWVPGSTGDIQMTQSPSSLSASVGDRVTITCSASQDISNYLNWYQQKPGKAPKLLIYYTSSLHTGVPSRFSGSGSGTDYTLTISSLQPEDIATYYCHQFSELPWTFGGGTKVEIKRTV (SEQ ID NO: 45)

[0211] Humanized C55-3 light chain variable domain protein sequence METDTLLLWVLLLWVPGSTGDIQMTQSPSSLSASVGDRVTITCQASQDISNYLNWYQQKPGKTPKLLIYYTSSLHTGVPSRFSGSGSGTDYTLTISSLQPEDIATYYCHQFSELPWTFGGGTKVEIKRTV (SEQ ID NO: 46)

[0212] Humanized C55-1 heavy chain variable domain protein sequence MDPKGSLSWRILLFLSLAFELSYGQVTLKESGPTLVKPTQTLTLTCTFSGFSLSTSGMGVGWIRQPPGKALEWLAHIWWDDDKYYNPSLKSRLTITKDTSKNQVVLTMTNMDPVDTATYYCARSFGYGLDYWGQGTLVTVSS (SEQ ID NO: 47)

[0213] Humanized C55-2 heavy chain variable domain protein sequence MDPKGSLSWRILLFLSLAFELSYGQVTLKESGPTLVKPTQTLTLTCTFSGFSLSTSGMGVGWIRQPPGKALEWLAHIWWDDDKYYNSSLKSRLTITKDTSKNQVVLTMTNMDPVDTATYYCARSFGYGLDYWGQGTLVTVSS (SEQ ID NO: 48)

[0214] Humanized C55-3 heavy chain variable domain protein sequence MDPKGSLSWRILLFLSLAFELSYGQVTLKESGPALVKPTQTLTLTCTFSGFSLSTSGMGVGWIRQPPGKALEWLAHIWWDDDKYYNTSLKSRLTITKDTSKNQVVLKMTNMDPVDTATYYCARSFGYGLDYWGQGTLVTVSS (SEQ ID NO: 49)

[0215] Humanized C55-1 FR L1: METDTLLLWVLLLWVPGSTGDIQMTQSPSSLSASVGDRVTITCQAS (SEQ ID NO: 50)

[0216] Humanized C55-1 FR L2: LNWYQQKPGKAPKLLIY (SEQ ID NO: 51)

[0217] Humanized C55-1 FR L3: SLHTGVPSRFSGSGSGTDYTFTISSLQPEDIATYYC (SEQ ID NO: 52)

[0218] Humanized C55-1 FR L4: FGGGTKVEIKRTV (SEQ ID NO: 53)

[0219] Humanized C55-2 FR L1: METDTLLLWVLLLWVPGSTGDIQMTQSPSSLSASVGDRVTITCSAS (SEQ ID NO:54)

[0220] Humanized C55-2 FR L2: LNWYQQKPGKAPKLLIY (SEQ ID NO: 55)

[0221] Humanized C55-2 FR L3: SLHTGVPSRFSGSGSGTDYTLTISSLQPEDIATYYC (SEQ ID NO: 56)

[0222] Humanized C55-2 FR L4: FGGGTKVEIKRTV (SEQ ID NO: 57)

[0223] Humanized C55-3 FR L1: METDTLLLWVLLLWVPGSTGDIQMTQSPSSLSASVGDRVTITCQAS (SEQ ID NO:58)

[0224] Humanized C55-3 FR L2: LNWYQQKPGKTPKLLIY (SEQ ID NO: 59)

[0225] Humanized C55-3 FR L3: SLHTGVPSRFSGSGSGTDYTLTISSLQPEDIATYYC (SEQ ID NO: 60)

[0226] Humanized C55-3 FR L4: FGGGTKVEIKRTV (SEQ ID NO: 61)

[0227] Humanized C55-1 FR H1: MDPKGSLSWRILLFLSLAFELSYGQVTLKESGPTLVKPTQTLTLTCTFS (SEQ ID NO: 62)

[0228] Humanized C55-1 FR H2: VGWIRQPPGKALEWLAH (SEQ ID NO: 63)

[0229] Humanized C55-1 FR H3: YYNPSLKSRLTITKDTSKNQVVLTMTNMDPVDTATYYC (SEQ ID NO: 64)

[0230] Humanized C55-1 FR H4:WGQGTLVTVSS (SEQ ID NO:65)

[0231] Humanized C55-2 FR H1: MDPKGSLSWRILLFLSLAFELSYGQVTLKESGPTLVKPTQTLTLTCTFS (SEQ ID NO: 66)

[0232] Humanized C55-2 FR H2: VGWIRQPPGKALEWLAH (SEQ ID NO: 67)

[0233] Humanized C55-2 FR H3: YYNSSLKSRLTITKDTSKNQVVLTMTNMDPVDTATYYC (SEQ ID NO: 68)

[0234] Humanized C55-2 FR H4:WGQGTLVTVSS (SEQ ID NO:69)

[0235] Humanized C55-3 FR H1: MDPKGSLSWRILLFLSLAFELSYGQVTLKESGPALVKPTQTLTLTCTFS (SEQ ID NO: 70)

[0236] Humanized C55-3 FR H2: VGWIRQPPGKALEWLAH (SEQ ID NO: 71)

[0237] Humanized C55-3 FR H3: YYNTSLKSRLTITKDTSKNQVVLKMTNMDPVDTATYYC (SEQ ID NO: 72)

[0238] Humanized C55-3 FR H4:WGQGTLVTVSS (SEQ ID NO:73)

[0239] Anti-CD3 scFv 1 CDR L1: TGAVTSGNY (SEQ ID NO: 74)

[0240] Anti-CD3 scFv 1 CDR L2: GTK (SEQ ID NO: 75)

[0241] Anti-CD3 scFv 1 CDR L3: VLWYSNRWV (SEQ ID NO: 76)

[0242] Anti-CD3 scFv 1 CDR H1: GFTFNKYA (SEQ ID NO: 77)

[0243] Anti-CD3 scFv 1 CDR H2: IRSKYNNYAT (SEQ ID NO: 78)

[0244] Anti-CD3 scFv 1 CDR H3: VRHGNFGNSYISYWAY (SEQ ID NO: 79)

[0245] Anti-CD3 scFv 1 protein sequence EVQLVESGGGLVQPGGSLKLSCAASGFTFNKYAMNWVRQAPGKGLEWVARIRSKYNNYATYYADSVKDRFTISRDDSKNTAYLQMNNLKTEDTAVYYCVRHGNFGNSYISYWAYWGQGTLVTVSSG GGGSGGGGSGGGGSQTVVTQEPSLTVSPGGTVTLTCGSSTGAVTSGNYPNWVQQKPGQAPRGLIGGTKFLAPGTPARFSGSLLGGKAALTLSGVQPEDEAEYYCVLWYSNRWVFGGGTKLTVL(SEQ ID NO:80)

[0246] Anti-CD3 scFv 2 CDR L1: SSVSY (SEQ ID NO: 81)

[0247] Anti-CD3 scFv 2 CDR L2: DTS (SEQ ID NO: 82)

[0248] Anti-CD3 scFv 2 CDR L3: QQWSSNPFT (SEQ ID NO: 83)

[0249] Anti-CD3 scFv 2 CDR H1: GYTFTRYT (SEQ ID NO: 84)

[0250] Anti-CD3 scFv 2 CDR H2: INPSRGYT (SEQ ID NO: 85)

[0251] Anti-CD3 scFv 2 CDR H3: ARYYDDHYCLDY (SEQ ID NO: 86)

[0252] Anti-CD3 scFv 2 protein sequence QVQLVQSGGGVVQPGRSLRLSCKASGYTFTRYTMHWVRQAPGKGLEWIGYINPSRGYTNYNQKVKDRFTISRDNSKNTAFLQMDSLRPEDTGVYFCARYYDDHYCLDYWGQGTPVTVSSGGGGSGGGGSGGGGSDIQMTQSPSSLSASVGDRVTITCSASSSVSYMNWYQQTPGKAPKRWIYDTSKLASGVPSRFSGSGSGTDYTFTISSLQPEDIATYYCQQWSSNPFTFGQGTKLQITR (SEQ ID NO: 87)

[0253] Embodiment Embodiment 1. A recombinant protein comprising: (i) a first antibody region capable of binding to an effector cell ligand; (ii) a second antibody region, (a) a light chain variable domain comprising a CDR L1 as set forth in SEQ ID NO: 1, a CDR L2 as set forth in SEQ ID NO: 2, and a CDR L3 as set forth in SEQ ID NO: 3; (b) a second antibody region comprising a heavy chain variable domain comprising the CDR H1 as set forth in SEQ ID NO:4, the CDR H2 as set forth in SEQ ID NO:5, and the CDR H3 as set forth in SEQ ID NO:6.

[0254] Embodiment 2. The recombinant protein of embodiment 1, wherein the light chain variable domain comprises the sequence of SEQ ID NO:7.

[0255] Embodiment 3. The recombinant protein of embodiment 1 or 2, wherein the heavy chain variable domain comprises the sequence of SEQ ID NO: 10.

[0256] Embodiment 4. The recombinant protein according to any one of embodiments 1 to 3, wherein the light chain variable domain comprises an FR L1 as set forth in SEQ ID NO: 13, an FR L2 as set forth in SEQ ID NO: 14, an FR L3 as set forth in SEQ ID NO: 15, and an FR L4 as set forth in SEQ ID NO: 16.

[0257] Embodiment 5. The recombinant protein according to any one of embodiments 1 to 4, wherein the heavy chain variable domain comprises a FR H1 as set forth in SEQ ID NO: 25, a FR H2 as set forth in SEQ ID NO: 26, a FR H3 as set forth in SEQ ID NO: 27, and a FR H4 as set forth in SEQ ID NO: 28.

[0258] Embodiment 6 The recombinant protein of embodiment 1, wherein the light chain variable domain comprises the sequence of SEQ ID NO:8.

[0259] Embodiment 7 The recombinant protein of embodiment 1 or 6, wherein the heavy chain variable domain comprises the sequence of SEQ ID NO:11.

[0260] Embodiment 8. The recombinant protein of any one of embodiments 1, 6, or 7, wherein the light chain variable domain comprises FR L1 as set forth in SEQ ID NO: 17, FR L2 as set forth in SEQ ID NO: 18, FR L3 as set forth in SEQ ID NO: 19, and FR L4 as set forth in SEQ ID NO: 20.

[0261] Embodiment 9. The recombinant protein according to any one of embodiments 1 or 6 to 8, wherein the heavy chain variable domain comprises a FR H1 as set forth in SEQ ID NO:29, a FR H2 as set forth in SEQ ID NO:30, a FR H3 as set forth in SEQ ID NO:31, and a FR H4 as set forth in SEQ ID NO:32.

[0262] Embodiment 10 The recombinant protein of embodiment 1, wherein the light chain variable domain comprises the sequence of SEQ ID NO:9.

[0263] Embodiment 11. The recombinant protein of embodiment 1 or 10, wherein the heavy chain variable domain comprises the sequence of SEQ ID NO: 12.

[0264] Embodiment 12. The recombinant protein of any one of embodiments 1, 10, or 11, wherein the light chain variable domain comprises FR L1 as set forth in SEQ ID NO:21, FR L2 as set forth in SEQ ID NO:22, FR L3 as set forth in SEQ ID NO:23, and FR L4 as set forth in SEQ ID NO:24.

[0265] Embodiment 13. The recombinant protein according to any one of embodiments 1, or 10 to 12, wherein the heavy chain variable domain comprises a FR H1 as set forth in SEQ ID NO: 33, a FR H2 as set forth in SEQ ID NO: 34, a FR H3 as set forth in SEQ ID NO: 35, and a FR H4 as set forth in SEQ ID NO: 36.

[0266] Embodiment 14. A recombinant protein comprising: (i) a first antibody region capable of binding to an effector cell ligand; (ii) a second antibody region, (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 38, CDR L2 as set forth in SEQ ID NO: 39 and CDR L3 as set forth in SEQ ID NO: 40; (b) a second antibody region comprising a heavy chain variable domain comprising CDR H1 as set forth in SEQ ID NO: 41, CDR H2 as set forth in SEQ ID NO: 42, and CDR H3 as set forth in SEQ ID NO: 44.

[0267] Embodiment 15 The recombinant protein of embodiment 14, wherein the light chain variable domain comprises the sequence of SEQ ID NO:44.

[0268] Embodiment 16 The recombinant protein of embodiment 14 or 15, wherein the heavy chain variable domain comprises the sequence of SEQ ID NO: 47.

[0269] Embodiment 17. A recombinant protein according to any one of embodiments 14 to 16, wherein the light chain variable domain comprises an FR L1 as set forth in SEQ ID NO: 50, an FR L2 as set forth in SEQ ID NO: 51, an FR L3 as set forth in SEQ ID NO: 52, and an FR L4 as set forth in SEQ ID NO: 53.

[0270] Embodiment 18. The recombinant protein according to any one of embodiments 14 to 17, wherein the heavy chain variable domain comprises a FR H1 as set forth in SEQ ID NO: 62, a FR H2 as set forth in SEQ ID NO: 63, a FR H3 as set forth in SEQ ID NO: 64, and a FR H4 as set forth in SEQ ID NO: 65.

[0271] Embodiment 19 The recombinant protein of embodiment 14, wherein the light chain variable domain comprises the sequence of SEQ ID NO:45.

[0272] Embodiment 20 The recombinant protein of embodiment 14 or 19, wherein the heavy chain variable domain comprises the sequence of SEQ ID NO:48.

[0273] Embodiment 21. The recombinant protein of any one of embodiments 14, 19, or 20, wherein the light chain variable domain comprises FR L1 as set forth in SEQ ID NO:54, FR L2 as set forth in SEQ ID NO:55, FR L3 as set forth in SEQ ID NO:56, and FR L4 as set forth in SEQ ID NO:57.

[0274] Embodiment 22. The recombinant protein of any one of embodiments 14, or 19 to 21, wherein the heavy chain variable domain comprises a FR H1 set forth in SEQ ID NO: 66, a FR H2 set forth in SEQ ID NO: 67, a FR H3 set forth in SEQ ID NO: 68, and a FR H4 set forth in SEQ ID NO: 69.

[0275] Embodiment 23 The recombinant protein of embodiment 14, wherein the light chain variable domain comprises the sequence of SEQ ID NO:46.

[0276] Embodiment 24 The recombinant protein of embodiment 14 or 23, wherein the heavy chain variable domain comprises the sequence of SEQ ID NO:49.

[0277] Embodiment 25. The recombinant protein of any one of embodiments 14, 23, or 24, wherein the light chain variable domain comprises FR L1 as set forth in SEQ ID NO:58, FR L2 as set forth in SEQ ID NO:59, FR L3 as set forth in SEQ ID NO:60, and FR L4 as set forth in SEQ ID NO:61.

[0278] Embodiment 26. The recombinant protein according to any one of embodiments 14 or 23 to 25, wherein the heavy chain variable domain comprises a FR H1 as set forth in SEQ ID NO: 70, a FR H2 as set forth in SEQ ID NO: 71, a FR H3 as set forth in SEQ ID NO: 72, and a FR H4 as set forth in SEQ ID NO: 73.

[0279] Embodiment 27. A recombinant protein according to any one of embodiments 1 to 26, wherein the first antibody region is a first Fab' fragment or the second antibody region is a second Fab' fragment.

[0280] Embodiment 28. A recombinant protein according to any one of embodiments 1 to 26, wherein the first antibody region is a first single chain variable fragment (scFv) or the second antibody region is a second single chain variable fragment (scFv).

[0281] Embodiment 29. The second antibody region has an equilibrium dissociation constant (K D 29. The recombinant protein according to any one of embodiments 1 to 28, which is capable of binding to the BAFF-R protein at

[0282] Embodiment 30. The second antibody region has an equilibrium dissociation constant (K D 30. The recombinant protein according to any one of the preceding embodiments, which is capable of binding to the BAFF-R protein at the nucleotide position (A) of the recombinant protein.

[0283] Embodiment 31. The first antibody region comprises: (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 74, CDR L2 as set forth in SEQ ID NO: 75, and CDR L3 as set forth in SEQ ID NO: 76; (b) a heavy chain variable domain comprising the CDR H1 as set forth in SEQ ID NO: 77, the CDR H2 as set forth in SEQ ID NO: 78, and the CDR H3 as set forth in SEQ ID NO: 79.

[0284] Embodiment 32. The first antibody region comprises: (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 81, CDR L2 as set forth in SEQ ID NO: 82, and CDR L3 as set forth in SEQ ID NO: 83; (b) a heavy chain variable domain comprising CDR H1 of SEQ ID NO: 84, CDR H2 of SEQ ID NO: 85, and CDR H3 of SEQ ID NO: 86;

[0285] Embodiment 33. A recombinant protein according to any one of embodiments 1 to 32, wherein the first antibody region is a first single chain variable fragment (scFv).

[0286] Embodiment 34. The recombinant protein of embodiment 33, wherein the first scFv comprises the sequence of SEQ ID NO: 80 or the sequence of SEQ ID NO: 87.

[0287] Embodiment 35. A recombinant protein according to any one of embodiments 1 to 34, wherein the effector cell ligand is a CD3 protein.

[0288] Embodiment 36 The recombinant protein of any one of embodiments 1 to 35, wherein the second antibody region binds to a BAFF-R protein.

[0289] Embodiment 37 The recombinant protein of embodiment 36, wherein the BAFF-R protein is a human BAFF-R protein.

[0290] Embodiment 38 The recombinant protein of embodiment 36, wherein the BAFF-R protein forms part of a cell.

[0291] Embodiment 39 The recombinant protein of embodiment 38, wherein the BAFF-R protein is expressed on the surface of the cell.

[0292] Embodiment 40 The recombinant protein of embodiment 39, wherein the cell is a lymphocytic cell.

[0293] Embodiment 41 The recombinant protein of embodiment 39, wherein the cell is a B cell.

[0294] Embodiment 42 The recombinant protein of embodiment 39, wherein the cell is a cancer cell.

[0295] Embodiment 43. The recombinant protein of embodiment 42, wherein the cancer cell is a lymphoma cell.

[0296] Embodiment 44. A pharmaceutical composition comprising a therapeutically effective amount of a recombinant protein according to any one of embodiments 1 to 43 and a pharma- ceutical acceptable excipient.

[0297] Embodiment 45. A method for treating cancer in a subject in need of treatment, comprising administering to the subject a therapeutically effective amount of a recombinant protein described in any one of embodiments 1 to 43, thereby treating the cancer in the subject.

[0298] Embodiment 46 The method of embodiment 45, wherein the cancer is lymphoma, leukemia, or myeloma.

[0299] Embodiment 47. A method for treating an autoimmune disease in a subject in need of such treatment, comprising administering to the subject a therapeutically effective amount of a recombinant protein described in any one of embodiments 1 to 43, thereby treating the autoimmune disease in the subject.

[0300] SEQ ID NOs: 2, 39, 75 and 82, which were skipped when converting from the st.25-based sequence listing to the st.26-based sequence listing, are shown below. <210> 2 <211> 3 <212> PRT <213> Artificial Sequence <220> <223> Synthetic construct <400> 2 Ala Ala Ser 1 <210> 39 <211> 3 <212> PRT <213> Artificial Sequence <220> <223> Synthetic construct <400> 39 Tyr Thr Ser 1 <210> 75 <211> 3 <212> PRT <213> Artificial Sequence <220> <223> Synthetic construct <400> 75 Gly Thr Lys 1 <210> 82 <211> 3 <212> PRT <213> Artificial Sequence <220> <223> Synthetic construct <400> 82 Asp Thr Ser 1

Claims

1. A recombinant protein comprising: (i) a first antibody region capable of binding to an effector cell ligand; (ii) a second antibody region, (a) a light chain variable domain comprising a CDR L1 as set forth in SEQ ID NO:1, a CDR L2 as set forth in SEQ ID NO:2, and a CDR L3 as set forth in SEQ ID NO:3; (b) a second antibody region comprising a heavy chain variable domain comprising CDR H1 set forth in SEQ ID NO:4, CDR H2 set forth in SEQ ID NO:5, and CDR H3 set forth in SEQ ID NO:

6.

2. The recombinant protein of claim 1 , wherein the light chain variable domain comprises the sequence of SEQ ID NO:

7.

3. 3. The recombinant protein of claim 1 or 2, wherein the heavy chain variable domain comprises the sequence of SEQ ID NO:

10.

4. 2. The recombinant protein of claim 1, wherein the light chain variable domain comprises FR L1 as set forth in SEQ ID NO: 13, FR L2 as set forth in SEQ ID NO: 14, FR L3 as set forth in SEQ ID NO: 15, and FR L4 as set forth in SEQ ID NO:

16.

5. 2. The recombinant protein of claim 1, wherein the heavy chain variable domain comprises a FR H1 set forth in SEQ ID NO:25, a FR H2 set forth in SEQ ID NO:26, a FR H3 set forth in SEQ ID NO:27, and a FR H4 set forth in SEQ ID NO:

28.

6. The recombinant protein of claim 1 , wherein the light chain variable domain comprises the sequence of SEQ ID NO:

8.

7. 7. The recombinant protein of claim 1 or 6, wherein the heavy chain variable domain comprises the sequence of SEQ ID NO:

11.

8. 2. The recombinant protein of claim 1, wherein the light chain variable domain comprises FR L1 as set forth in SEQ ID NO: 17, FR L2 as set forth in SEQ ID NO: 18, FR L3 as set forth in SEQ ID NO: 19, and FR L4 as set forth in SEQ ID NO:

20.

9. 2. The recombinant protein of claim 1, wherein the heavy chain variable domain comprises a FR H1 set forth in SEQ ID NO:29, a FR H2 set forth in SEQ ID NO:30, a FR H3 set forth in SEQ ID NO:31, and a FR H4 set forth in SEQ ID NO:

32.

10. The recombinant protein of claim 1 , wherein the light chain variable domain comprises the sequence of SEQ ID NO:

9.

11. 11. The recombinant protein of claim 1 or 10, wherein the heavy chain variable domain comprises the sequence of SEQ ID NO:

12.

12. 2. The recombinant protein of claim 1, wherein the light chain variable domain comprises FR L1 as set forth in SEQ ID NO:21, FR L2 as set forth in SEQ ID NO:22, FR L3 as set forth in SEQ ID NO:23, and FR L4 as set forth in SEQ ID NO:

24.

13. 2. The recombinant protein of claim 1, wherein the heavy chain variable domain comprises a FR H1 set forth in SEQ ID NO:33, a FR H2 set forth in SEQ ID NO:34, a FR H3 set forth in SEQ ID NO:35, and a FR H4 set forth in SEQ ID NO:

36.

14. A recombinant protein comprising: (i) a first antibody region capable of binding to an effector cell ligand; (ii) a second antibody region, (a) a light chain variable domain comprising a CDR L1 as set forth in SEQ ID NO: 38, a CDR L2 as set forth in SEQ ID NO: 39, and a CDR L3 as set forth in SEQ ID NO: 40; (b) a second antibody region comprising a heavy chain variable domain comprising CDR H1 set forth in SEQ ID NO:41, CDR H2 set forth in SEQ ID NO:42, and CDR H3 set forth in SEQ ID NO:

43.

15. 15. The recombinant protein of claim 14, wherein the light chain variable domain comprises the sequence of SEQ ID NO:

44.

16. 16. The recombinant protein of claim 14 or 15, wherein the heavy chain variable domain comprises the sequence of SEQ ID NO:

47.

17. 15. The recombinant protein of claim 14, wherein the light chain variable domain comprises FR L1 as set forth in SEQ ID NO:50, FR L2 as set forth in SEQ ID NO:51, FR L3 as set forth in SEQ ID NO:52, and FR L4 as set forth in SEQ ID NO:

53.

18. 15. The recombinant protein of claim 14, wherein the heavy chain variable domain comprises a FR H1 set forth in SEQ ID NO:62, a FR H2 set forth in SEQ ID NO:63, a FR H3 set forth in SEQ ID NO:64, and a FR H4 set forth in SEQ ID NO:

65.

19. 15. The recombinant protein of claim 14, wherein the light chain variable domain comprises the sequence of SEQ ID NO:

45.

20. 20. The recombinant protein of claim 14 or 19, wherein the heavy chain variable domain comprises the sequence of SEQ ID NO:

48.

21. 15. The recombinant protein of claim 14, wherein the light chain variable domain comprises FR L1 as set forth in SEQ ID NO:54, FR L2 as set forth in SEQ ID NO:55, FR L3 as set forth in SEQ ID NO:56, and FR L4 as set forth in SEQ ID NO:

57.

22. 15. The recombinant protein of claim 14, wherein the heavy chain variable domain comprises a FR H1 set forth in SEQ ID NO:66, a FR H2 set forth in SEQ ID NO:67, a FR H3 set forth in SEQ ID NO:68, and a FR H4 set forth in SEQ ID NO:

69.

23. 15. The recombinant protein of claim 14, wherein the light chain variable domain comprises the sequence of SEQ ID NO:

46.

24. 24. The recombinant protein of claim 14 or 23, wherein the heavy chain variable domain comprises the sequence of SEQ ID NO:

49.

25. 15. The recombinant protein of claim 14, wherein the light chain variable domain comprises FR L1 as set forth in SEQ ID NO:58, FR L2 as set forth in SEQ ID NO:59, FR L3 as set forth in SEQ ID NO:60, and FR L4 as set forth in SEQ ID NO:

61.

26. 15. The recombinant protein of claim 14, wherein the heavy chain variable domain comprises a FR H1 set forth in SEQ ID NO: 70, a FR H2 set forth in SEQ ID NO: 71, a FR H3 set forth in SEQ ID NO: 72, and a FR H4 set forth in SEQ ID NO:

73.

27. 2. The recombinant protein of claim 1, wherein the first antibody region is a first Fab' fragment or the second antibody region is a second Fab' fragment.

28. 2. The recombinant protein of claim 1, wherein the first antibody region is a first single chain variable fragment (scFv) or the second antibody region is a second single chain variable fragment (scFv).

29. The second antibody region has an equilibrium dissociation constant (K Ｄ 2. The recombinant protein of claim 1, which is capable of binding to BAFF-R protein at the nucleotide sequence (SEQ ID NO: 1).

30. The second antibody region has an equilibrium dissociation constant (K Ｄ 2. The recombinant protein of claim 1, which is capable of binding to BAFF-R protein at the nucleotide sequence (SEQ ID NO: 1).

31. The first antibody region comprises: (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 74, CDR L2 as set forth in SEQ ID NO: 75, and CDR L3 as set forth in SEQ ID NO: 76; (b) a heavy chain variable domain comprising a CDR H1 set forth in SEQ ID NO:77, a CDR H2 set forth in SEQ ID NO:78, and a CDR H3 set forth in SEQ ID NO:

79.

32. The first antibody region comprises: (a) a light chain variable domain comprising CDR L1 as set forth in SEQ ID NO: 81, CDR L2 as set forth in SEQ ID NO: 82, and CDR L3 as set forth in SEQ ID NO: 83; (b) a heavy chain variable domain comprising a CDR H1 of SEQ ID NO:84, a CDR H2 of SEQ ID NO:85, and a CDR H3 of SEQ ID NO:

86.

33. 33. The recombinant protein of claim 1 or 32, wherein the first antibody region is a first single chain variable fragment (scFv).

34. The recombinant protein of claim 33, wherein the first scFv comprises the sequence of SEQ ID NO: 80 or the sequence of SEQ ID NO:

87.

35. The recombinant protein of claim 1 , wherein the effector cell ligand is a CD3 protein.

36. The recombinant protein of claim 1, wherein the second antibody region binds to a BAFF-R protein.

37. 37. The recombinant protein of claim 36, wherein the BAFF-R protein is a human BAFF-R protein.

38. 37. The recombinant protein of claim 36, wherein the BAFF-R protein forms part of a cell.

39. 39. The recombinant protein of claim 38, wherein the BAFF-R protein is expressed on the surface of the cell.

40. 40. The recombinant protein of claim 39, wherein the cell is a lymphocytic cell.

41. 40. The recombinant protein of claim 39, wherein the cell is a B cell.

42. 40. The recombinant protein of claim 39, wherein the cell is a cancer cell.

43. 43. The recombinant protein of claim 42, wherein the cancer cell is a lymphoma cell.

44. 13. A pharmaceutical composition comprising a therapeutically effective amount of the recombinant protein of claim 1 and a pharma- ceutically acceptable excipient.

45. 11. A method for treating cancer in a subject in need of treatment, comprising administering to the subject a therapeutically effective amount of the recombinant protein described in claim 1, thereby treating the cancer in the subject.

46. 46. ​​The method of claim 45, wherein the cancer is lymphoma, leukemia, or myeloma.

47. 11. A method for treating an autoimmune disease in a subject in need of treatment, comprising administering to the subject a therapeutically effective amount of the recombinant protein described in claim 1, thereby treating the autoimmune disease in the subject.

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