Antibody purification

Abstract

This invention provides a method for purifying antibodies. The purification method involves using hydroxyapatite (HA) resin to separate the antibody of interest from one or more impurities.

Description

Antibody purification The present invention relates to methods for purifying antibodies from impurities such as antibody degradation products. The purification methods disclosed herein involve the use of hydroxyapatite resin. Antibodies are important biomolecules used in medicine, diagnostics, industry, and other applications. Although many methods and reagents are available for the recombinant production of antibodies, due to, for example, the size and molecular complexity of antibodies, it is often difficult to efficiently produce and purify the recombinant antibodies of interest, especially at large / industrial scale production levels. For example, during the production of a recombinant antibody of interest, degradation products associated with the antibody of interest may sometimes appear; these degradation products are unwanted impurities. These degradation products have some molecular properties that are very similar to those of the antibody of interest (e.g., identical or nearly identical amino acid sequence or mass). Due to the molecular similarity between the intact antibody of interest and the degraded form of the antibody, it may be very difficult to effectively separate the intact antibody from the degraded antibody. Therefore, there is a need for new and improved methods for purifying antibodies from impurities. Provided herein are methods for purifying an antibody of interest from one or more impurities. In some embodiments, provided herein are methods of purifying an antibody, the methods comprising: A) loading an antibody preparation in a loading buffer onto a hydroxyapatite (HA) resin, wherein: the antibody preparation comprises: I) an intact antibody of interest and II) a trimmed form of the antibody of interest, wherein the trimmed form of the antibody of interest is a degradation product of the intact antibody of interest and has a mass that differs by less than 10% from the mass of the intact bispecific antibody of interest; and B) eluting the intact antibody of interest from the HA resin with an elution buffer. In some embodiments, provided herein are methods for purifying a bispecific antibody, the method comprising: A) loading an antibody preparation in a loading buffer onto a hydroxyapatite (HA) resin, wherein: the antibody preparation comprises: I) an intact bispecific antibody of interest; and II) at least one impurity, wherein the impurity is selected from the group consisting of: a) a trimmed form of the bispecific antibody of interest, wherein the trimmed form of the bispecific antibody of interest is a degradation product of the intact bispecific antibody of interest and has a mass that differs by less than 10% from the mass of the intact bispecific antibody of interest; b) a first parent antibody, wherein the first parent antibody is a monospecific antibody with the same antigenic specificity as the first arm of the intact bispecific antibody; c) a second parent antibody, wherein the second parent antibody is a monospecific antibody with the same antigenic specificity as the second arm of the intact bispecific antibody; and d) high molecular mass species (HMMS); and B) eluting the intact bispecific antibody of interest from the HA resin with an elution buffer. In some embodiments, provided herein are methods for purifying bispecific antibodies, the methods comprising: A) loading an antibody preparation in a loading buffer onto a hydroxyapatite (HA) resin, wherein: I) the antibody preparation comprises: a) an intact bispecific antibody of interest and b) a trimmed form of the bispecific antibody of interest, wherein the trimmed form of the antibody of interest is a degradation product of the intact bispecific antibody of interest and its mass differs by less than 10% from the mass of the intact bispecific antibody of interest; and II) the ratio of trimmed bispecific antibody molecules to intact bispecific antibody molecules in the antibody preparation is at least 1:50 and no greater than 1:5; B) eluting the intact bispecific antibody from the HA resin with an elution buffer. In some embodiments, the method further comprises the steps of: C) collecting purified fractions eluted from the HA resin, wherein the purified fractions comprise the intact bispecific antibody. In some embodiments, provided herein are methods of purifying an antibody, the methods comprising: A) loading an antibody preparation in a loading buffer onto a hydroxyapatite (HA) resin, wherein: I) the antibody preparation comprises: a) an intact antibody of interest and b) a trimmed form of the antibody of interest, wherein the trimmed form of the antibody of interest is a degradation product of the intact antibody of interest and has a mass that differs by less than 10% from the mass of the intact antibody of interest; and II) the trimmed form of the antibody comprises at least 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, or 20% (by mass) of the antibody preparation; B) eluting the intact antibody from the HA resin with an elution buffer, and C) collecting purified fractions eluted from the HA resin, wherein the purified fractions comprise intact antibody and comprise less than 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, or 20% by mass of the trimmed antibody, wherein the purified fractions comprise a lower percentage of trimmed antibody by mass than the antibody preparation. In some embodiments, in the methods provided herein involving eluting an antibody of interest from an HA resin with an elution buffer, the elution buffer comprises ions. Optionally, the concentration of the ions in the buffer is increased during elution. Optionally, the concentration of the ions in the buffer surrounding the HA resin is increased during elution. In some embodiments, in the methods provided herein involving antibodies, the antibody is a heterodimeric bispecific antibody. In some embodiments, in the methods provided herein involving collecting purified fractions eluted from an HA resin, wherein the purified fractions comprise an intact antibody of interest, the purified fractions comprise at least 80%, 90%, 95%, 96%, 97%, 98%, or 99% by mass of the intact antibody of interest. In some embodiments, in the methods provided herein involving purified fractions comprising intact bispecific antibodies and trimmed bispecific antibodies, the ratio of trimmed bispecific antibody molecules to intact bispecific antibody molecules in the purified fractions is no greater than 1:400, 1:200, 1:100, or 1:50. In some embodiments, in the methods provided herein involving the antibody of interest being an anti-CD3 antibody or a bispecific antibody comprising an anti-CD3 arm, the antibody comprises at least one of the following: i) a VH region comprising the amino acid sequence set forth in SEQ ID NO: 1; ii) a heavy chain comprising the amino acid sequence set forth in SEQ ID NO: 2; iii) a VH region comprising the amino acid sequence set forth in SEQ ID NO: 1 and a VL region comprising the amino acid sequence set forth in SEQ ID NO: 3; or iv) a heavy chain comprising the amino acid sequence set forth in SEQ ID NO: 2 and a light chain comprising the amino acid sequence set forth in SEQ ID NO: 4. In some embodiments, in the methods provided herein involving bispecific antibodies, the bispecific antibody is: i) an anti-BCMA / anti-CD3 bispecific antibody comprising an anti-BCMA arm and an anti-CD3 arm, or ii) an anti-FLT3 / anti-CD3 bispecific antibody comprising an anti-FLT3 arm and an anti-CD3 arm. In some embodiments, in the methods provided herein involving a bispecific antibody comprising an anti-BCMA arm, the anti-BCMA arm comprises at least one of: i) a VH region comprising the amino acid sequence set forth in SEQ ID NO: 5; ii) a heavy chain comprising the amino acid sequence set forth in SEQ ID NO: 6; iii) a VH region comprising the amino acid sequence set forth in SEQ ID NO: 5 and a VL region comprising the amino acid sequence set forth in SEQ ID NO: 7; or iv) a heavy chain comprising the amino acid sequence set forth in SEQ ID NO: 6 and a light chain comprising the amino acid sequence set forth in SEQ ID NO: 8. In some embodiments, in the methods provided herein involving bispecific antibodies comprising an anti-FLT3 arm, the anti-FLT3 arm comprises at least one of the following: i) a VH region comprising the amino acid sequence set forth in SEQ ID NO: 9; ii) a heavy chain comprising the amino acid sequence set forth in SEQ ID NO: 10; iii) a VH region comprising the amino acid sequence set forth in SEQ ID NO: 9 and a VL region comprising the amino acid sequence set forth in SEQ ID NO: 11; or iv) a heavy chain comprising the amino acid sequence set forth in SEQ ID NO: 10 and a light chain comprising the amino acid sequence set forth in SEQ ID NO: 12. In some embodiments, in the methods provided herein involving loading an antibody formulation onto a HA resin, the antibody formulation is loaded onto the HA resin so that the density on the resin is between 2, 3, 4, or 5 g / L and 8, 9, 10, 12, 15, or 20 g / L. In some embodiments, in the methods provided herein involving loading an antibody preparation onto a HA resin, at least 1, 5, 10, 50, 100, 500, 1000, or 5000 grams of the antibody preparation is loaded onto the HA resin. In some embodiments, in the methods provided herein involving antibody preparations, the antibody preparation comprises at least 50%, 60%, 70%, or 80% and less than 90%, 95%, 97%, 98%, or 99% by mass of the intact antibody of interest. In some embodiments, in the methods provided herein involving trimmed antibodies, the mass of the trimmed antibody differs from the mass of the intact antibody by less than 0.1%, 0.5%, 1%, or 2%. In some embodiments, in the methods provided herein involving trimmed antibodies, the mass of the trimmed antibody is between about 5 and 100 Daltons greater than the mass of the intact antibody. In some embodiments, in the methods provided herein involving trimmed antibodies, the mass of the trimmed antibody is about 18 Daltons greater than the mass of the intact antibody. In some embodiments, in the methods provided herein involving trimmed antibodies, the trimmed antibody has a cleaved peptide bond in the polypeptide chain of the antibody, and wherein the cleaved peptide bond is in the heavy chain of the antibody. In some embodiments, in the methods provided herein involving trimmed antibodies, the trimmed antibody has a cleaved peptide bond in the polypeptide chain of the antibody, and wherein the cleaved peptide bond is in the light chain of the antibody. In some embodiments, in the methods provided herein involving trimmed antibodies, the trimmed antibody comprises the same number of amino acids and the same amino acid sequence as the intact antibody. Alternatively, in some embodiments, the trimmed antibody comprises a different number of amino acids than the intact antibody. In some embodiments, in the methods provided herein involving antibodies of interest comprising VH and VL domains that specifically bind to CD3, the corresponding trimmed antibodies comprise a cleaved peptide bond in the VH domain that specifically binds to CD3. In some embodiments, in the methods provided herein involving HA resins, the HA resin is a ceramic hydroxyapatite (cHA) resin. In some embodiments, in the methods provided herein, after loading the antibody preparation onto the HA resin but before eluting the intact bispecific antibody from the resin, the HA resin is washed with a wash buffer comprising phosphate ions. Optionally, the wash buffer comprises phosphate ions at a concentration between about 5, 10, 15, 20 mM and 30, 40, or 50 mM. In some embodiments, in the methods provided herein involving an elution buffer comprising an ion, the ion is phosphate. In some embodiments, the concentration of phosphate ions during elution can be increased from about 30, 40, or 50 mM to about 60, 70, 80, 100, 150, or 200 mM. In some embodiments, in the methods provided herein, the pH of at least one of the loading buffer, wash buffer, and elution buffer is at or between about pH 7.0 and 8.0. In some embodiments, in the methods provided herein involving antibody preparations, the antibody preparation comprises a protein pre-loaded onto and eluted from at least one of: i) a protein A resin and ii) an ion exchange resin. Optionally, the antibody preparation comprises a protein pre-loaded onto and eluted from both: i) a protein A resin and ii) an ion exchange resin. In some embodiments, antibodies produced using the methods described herein are isolated and / or purified for use as a pharmaceutical or for the preparation of a pharmaceutical. In some embodiments, antibodies purified using the methods described herein are provided. This application claims the benefit of U.S. Provisional Application No. 62 / 635,943, filed February 27, 2018, which is incorporated herein by reference in its entirety. Provided herein is a method for the purification of antibodies of concern from one or more impurities. The method provided herein relates to using hydroxyapatite resin to separate antibodies of concern from impurities. In certain embodiments, antibodies of concern are bispecific antibodies. In certain embodiments, impurities are antibodies related to antibodies of concern (that is, they have an amino acid sequence similar to or identical to antibodies of concern), but change in one or more ways compared to antibodies of concern, and their quality is different from antibodies of concern. Optionally, the quality of antibody impurity substances is very similar to the quality of antibodies of concern. For example, in certain embodiments, the quality of antibody impurity substances differs from the quality of antibodies of concern by less than 5%, 2%, 1%, 0.5%, 0.2%, 0.1%, 0.05%, 0.02% or 0.01%. Optionally, the method provided herein can be used for the purification of antibodies of concern from one or more impurities on a large scale. Definitions Unless otherwise defined, all technical terms, symbols, and other scientific terms or terminology used herein are intended to have the meanings commonly understood by those skilled in the art to which this invention pertains. In some cases, terms with commonly understood meanings are defined herein for clarity and / or ease of reference, and the inclusion of such definitions herein should not necessarily be construed as representing a substantial difference from what is commonly understood in the art. Unless otherwise indicated, the following terms shall be understood to have the following meanings: "Antibody" is an immunoglobulin molecule that is capable of specifically binding to a target (such as a carbohydrate, polynucleotide, lipid, polypeptide, etc.) through at least one antigen recognition site located in the variable region of the immunoglobulin molecule. As used herein, the term includes not only complete polyclonal or monoclonal antibodies, but also fragments thereof (such as Fab, Fab', F(ab') 2, Fv), single chain (ScFv) and domain antibodies (including (for example) shark and camelid antibodies), bifunctional antibodies and fusion proteins comprising antibodies, and any other modified configuration of immunoglobulin molecules comprising antigen recognition sites. The term "antibody" includes monospecific, bispecific and multispecific antibodies. Antibodies include antibodies of any class, such as IgG, IgA or IgM (or their subclasses), and the antibodies need not be of any particular class. Immunoglobulins can be assigned to different classes depending on the antibody amino acid sequence of the constant region of their heavy chains. There are five major classes of immunoglobulins: IgA, IgD, IgE, IgG and IgM, and several of them can be further divided into subclasses (isotypes), for example, IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2. The heavy chain constant regions corresponding to the different classes of immunoglobulins are called α, δ, ε, γ and μ, respectively. The subunit structures and three-dimensional configurations of the different classes of immunoglobulins are well known. As used herein, the terms "heavy chain," "light chain," "variable region," "variable domain," "framework region," "constant domain," and similar terms have their ordinary meanings in the art of immunology and refer to domains in naturally occurring immunoglobulins and corresponding domains in recombinant binding proteins (e.g., humanized antibodies, bispecific antibodies, single-chain antibodies, chimeric antibodies, etc.). The basic structural unit of a naturally occurring immunoglobulin is a tetramer comprising two light chains and two heavy chains, typically represented by a glycoprotein of approximately 150,000 Da. The amino-terminal (N-terminal) portion of each chain comprises a variable region of approximately 100-110 or more amino acids primarily responsible for antigen recognition. The carboxyl-terminal (C-terminal) portion of each chain defines the constant region. Each light chain comprises a light chain variable domain (VL) and a light chain constant domain (CL). Each heavy chain comprises a heavy chain variable region (VH) and a heavy chain constant region, which have CH1, hinge, CH2, and CH3 domains. The variable region of an IgG molecule comprises an area of ​​hypervariability, called the complementarity determining region (CDR), which includes residues that contact the antigen, and non-CDR segments, called the framework region (FR), which generally maintain structure and determine the positioning of the CDR loops, although some framework residues may also contact the antigen. Each VH and VL comprises three CDRs and four FRs arranged from amino-terminus to carboxyl-terminus in the following structure: n-FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4-c. Immunoglobulin molecules can be of any type (e.g., IgG, IgE, IgM, IgD, IgA, and IgY) and class (e.g., IgG1, IgG2, IgG3, IgG4, IgA1, and IgA2) or subclass. "Bispecific" or "dual specificity" refers to a hybrid antibody with two different antigen-binding sites. The two antigen-binding sites of a bispecific antibody bind to two different antigenic determinants, which can be located on the same or different protein targets. An "intact" antibody refers to a recombinant antibody that contains all the expected peptide bonds and amino acids of a recombinant antibody (i.e., as expected based on the nucleic acid sequence encoding the polypeptide of the antibody). In contrast, a "trimmed" antibody refers to a form of the corresponding "intact" antibody that lacks at least one peptide bond compared to the corresponding "intact" antibody. Unless the context clearly dictates otherwise, references herein to an "antibody of interest" generally refer to the intact antibody of interest. Reference herein to "about" a value or parameter includes embodiments for the value or parameter itself as well as embodiments for values ​​or parameters that are 10% lower or 10% higher than the stated value of the parameter. For example, reference to "about 5 mg" includes 5 mg as well as any value between 4.5 mg and 5.5 mg. Methods The methods provided herein can be used to purify an antibody of interest from one or more impurities. In the methods provided herein, an antibody preparation comprising an antibody of interest and one or more impurity molecules (also referred to herein as a "starting sample") is loaded onto a hydroxyapatite (HA) resin, which is bound to the antibody of interest and, if necessary, to one or more impurity molecules. The HA resin is then washed to remove any loosely bound impurities. (In some embodiments, all impurity molecules may flow through but not bind to the HA resin.) Next, the antibody of interest is eluted from the HA resin using a phosphate elution buffer, which is typically introduced onto the resin via an increasing gradient of phosphate ion concentration. Elution of the antibody of interest from the HA resin produces a purified sample comprising the antibody of interest, and has fewer (or no) impurities than those present in the starting sample with the antibody of interest. During the elution of the antibody of interest from the HA resin, any impurity molecules bound to the HA resin may also be eluted at a certain point during the increasing gradient of phosphate ion concentration. However, impurity molecules are eluted from the HA resin under conditions that are significantly different from the elution conditions of the antibody of interest, so that the antibody of interest can be effectively separated from the impurity molecules during the elution process. Additional details regarding the above-described method steps and related materials and steps are provided below. Hydroxyapatite Resins Various hydroxyapatite resins are commercially available, and any available form of the material can be used with the methods provided herein. Optionally, the hydroxyapatite is in crystalline form. Optionally, the hydroxyapatite is agglomerated to form particles and sintered at high temperature to form a stable porous ceramic block. In some embodiments, the HA resin provided herein is a ceramic hydroxyapatite (cHA) resin. "Ceramic hydroxyapatite" / "cHA" refers to a hydroxyapatite resin of the formula Ca 10 (PO 4) 6(OH) 2 insoluble hydroxylated calcium phosphate, which has been sintered at high temperature to form a spherical macroporous ceramic form. Unless otherwise specified, as used herein, "ceramic hydroxyapatite" / "cHA" includes, but is not limited to, Type I and Type II ceramic hydroxyapatite, and also includes any suitable particle size. Typical cHA particle sizes that can be used with the methods provided herein include, for example, particle sizes between 1 and 100 μm or 1 and 1000 μm in diameter, such as 20 μm, 40 μm, or 80 μm. Exemplary cHA resins that can be used with the methods provided herein include CHT™ Type I and Type II resins (Bio-Rad). Any reference herein to "HA resin" or the like includes cHA resins. Typically, in the methods provided herein, the HA resin is provided in one or more chromatography columns. Column properties (e.g., column diameter, length, and packing density) can be selected based on various factors, including the requirements of a particular purification project (i.e., the amount of protein to be purified) and factors related to the HA resin to be used in the column (such as its pore size, particle size, compressibility, loading capacity, and dynamic binding capacity). In addition, the methods provided herein generally describe HA resins in chromatography columns; however, other suitable configurations of the resin are not excluded. In addition, references herein to "HA columns" or the like refer to chromatography columns filled with HA resins. Equilibration before protein loading HA In some embodiments, the methods provided herein can include a step of pre-equilibrating the column with one or more equilibration buffers prior to loading a sample comprising an antibody of interest onto the HA column. The equilibration buffer can be introduced onto the column, for example, to ensure that the HA resin is clean at the start of the method (i.e., to ensure that the resin is free of impurities already bound to the resin) and / or to ensure that the solution surrounding the HA resin is compatible with the sample to be loaded onto the resin. In some embodiments, the equilibration buffer is a phosphate buffer comprising, for example, sodium phosphate, wherein the concentration of phosphate ions in the buffer is about 100 to 500 mM. Such equilibration buffers may also be referred to herein as "high phosphate equilibration buffers" or similar terms. For example, in one embodiment, the high phosphate equilibration buffer may comprise about 250 to 450 mM phosphate ions; in other embodiments, it may comprise about 200, 250, 300, 350, 400, or 450 mM phosphate ions. The equilibration buffer comprises a relatively high concentration of phosphate ions in the buffer to elute any contaminants / impurities already present on the HA resin (i.e., contaminants / impurities present before the sample comprising the protein of interest is loaded onto the resin; such impurities may be present, for example, if the HA resin has been previously used in a purification method and the resin was not completely cleared after the previous use). The high phosphate equilibration buffer may have a pH of about 6.0 to 9.0. For example, in one embodiment, the high phosphate equilibration buffer may have a pH of about 7.0 to 8.0; in other embodiments, it may have a pH of about 7.0, 7.5, or 8.0. In one embodiment, the high phosphate equilibration buffer comprises about 400 mM phosphate ions and has a pH of about 7.5. In some embodiments, the high phosphate equilibration buffer may also be referred to herein as "equilibration buffer 1." In some embodiments, the equilibration buffer is a phosphate buffer comprising, for example, sodium phosphate, wherein the concentration of phosphate ions in the buffer is about 1 to 20 mM. Such equilibration buffers may also be referred to herein as "low phosphate equilibration buffers" or similar terms. For example, in one embodiment, the low phosphate equilibration buffer may comprise about 1 to 10 mM phosphate ions; in other embodiments, it may comprise about 1, 2, 3, 4, 5, or 10 mM phosphate ions. The equilibration buffer comprises a relatively low concentration of phosphate ions in the buffer to create conditions around the HA resin that facilitate binding of the protein of interest to the resin. Optionally, the low phosphate equilibration buffer may further comprise HEPES at a concentration of about 1 to 50 mM. For example, in one embodiment, the low phosphate equilibration buffer may comprise about 2 to 30 mM HEPES; in other embodiments, it may comprise about 5, 10, 15, 20, or 25 mM HEPES. The low phosphate equilibration buffer may have a pH of about 6.0 to 9.0. For example, in one embodiment, the low phosphate equilibration buffer can have a pH of about 7.0 to 8.0; in other embodiments, it can have a pH of about 7.0, 7.5, or 8.0. In one embodiment, the low phosphate equilibration buffer comprises about 2 mM phosphate ions, 20 mM HEPES, and has a pH of about 7.5. In some embodiments, the low phosphate equilibration buffer may also be referred to herein as "equilibration buffer 2." However, it is important to note that using the methods provided herein, the low phosphate equilibration buffer can be used to pre-equilibrate the resin, eliminating the need for pre-equilibration with a high phosphate equilibration buffer during the method. Load the sample containing the antibody of interest HA Once the HA column is ready to load protein, the sample containing the antibody of interest and impurities is immediately loaded onto the HA column. The buffer in which the sample is loaded onto the HA column may be referred to as "loading buffer" in this article. In some embodiments, when a sample containing the antibody of interest is obtained for use with the method as provided herein, the sample is already contained in a suitable loading buffer for loading the sample onto the HA column. However, in other embodiments, before the sample is loaded onto the HA column, the sample may be processed (e.g., diluted, concentrated, or buffer exchanged) to change the buffer conditions of the sample so that the sample is contained in a suitable buffer for loading onto the column. For example, using the method provided herein, loading buffer cannot have a high concentration of phosphate ions, which would hinder the antibody of interest from binding to the HA resin. Therefore, if the initial sample containing the antibody of interest contains a high concentration of phosphate ions, the sample needs to be diluted or buffer exchanged, for example, until the concentration of phosphate ions in the sample is reduced to a suitably low concentration, allowing the antibody of interest to bind to the HA resin. In some embodiments, the loading buffer comprises no more than about 10 mM phosphate ions. For example, in some embodiments, the loading buffer comprises less than about 10 mM, 5 mM, 4 mM, 3 mM, 2 mM, or 1 mM phosphate ions. In some embodiments, the loading buffer comprises 0 mM phosphate ions. Optionally, the loading buffer may comprise various other salts or buffer components (e.g., Tris, glycine). The loading buffer may have a pH of about 6.0 to 9.0. For example, in one embodiment, the loading buffer may have a pH of about 7.0 to 8.0; in other embodiments, it may have a pH of about 7.0, 7.5, or 8.0. In some embodiments, the sample comprising the antibody of interest can be loaded onto the HA resin to a density on the resin of at least 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 12 g / L, 15 g / L, 20 g / L, 25 g / L, or 30 g / L. In some embodiments, the sample comprising the antibody of interest can be loaded onto the HA resin at a density on the resin of at least 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 12 g / L, 15 g / L, 20 g / L, or 25 g / L and no greater than 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 12 g / L, 15 g / L, 20 g / L, 25 g / L, or 30 g / L, wherein the second value is greater than the first value. washing HA After loading the sample comprising the antibody of interest and impurities onto the HA column, but before eluting the antibody of interest, the methods provided herein may optionally include a further step of washing the loaded column with one or more wash buffers, for example, to remove non-specifically immobilized impurities or otherwise prepare or equilibrate the column for the elution step. The properties of any wash buffer can be determined by one of ordinary skill in the art. In one embodiment, the wash buffer is a phosphate buffer comprising, for example, sodium phosphate, and the concentration of phosphate ions in the buffer is about 5 to 50 mM. For example, in one embodiment, the wash buffer may comprise about 10 to 40 mM phosphate ions; in other embodiments, it may comprise about 10, 20, 30, 40, or 50 mM phosphate ions. Optionally, the wash buffer may further comprise HEPES at a concentration of about 1 to 50 mM. For example, in one embodiment, the wash buffer may comprise about 2 to 30 mM HEPES; in other embodiments, it may comprise about 5, 10, 15, 20, or 25 mM HEPES. The wash buffer may have a pH of about 6.0 to 9.0. For example, in one embodiment, the wash buffer may have a pH of about 7.0 to 8.0; in other embodiments, it may have a pH of about 7.0, 7.5, or 8.0. In one embodiment, the wash buffer comprises about 40 mM phosphate ions, 20 mM HEPES, and has a pH of about 7.5. since HA Column elution of the antibody of interest The methods provided herein include the step of eluting the bound antibody of interest from the HA resin. The bound antibody of interest is eluted by one or more elution buffers. Typically, the elution buffer comprises one or more salts or ions, and the concentration of the salts or ions increases during the elution period. In some embodiments, the elution buffer provided herein comprises phosphate ions. Optionally, the concentration of phosphate ions in the elution buffer is increased from an initial concentration of about 20 mM to about 200 mM during elution. For example, in one embodiment, the concentration of phosphate ions in the elution buffer is increased from an initial concentration of about 40 mM to about 80 mM or from an initial concentration of about 40 mM to about 100 mM during elution. The specific method and rate for increasing the concentration of phosphate ions in the elution buffer can be determined to be suitable for the antibody of interest, taking into account the type of impurity molecules that are also bound to the HA resin. For example, the concentration of phosphate ions in the elution buffer can be increased gradually / shallow linear gradient. Using a shallow gradient can allow one or more molecules eluted from the HA resin to be effectively separated under similar but different conditions. Alternatively, in some embodiments, the concentration of phosphate ions in the elution buffer can be increased by a steep gradient, or can be increased stepwise. Optionally, the elution buffer can additionally comprise HEPES at a concentration of about 1 to 50 mM. For example, in one embodiment, the elution buffer may comprise about 2 to 30 mM HEPES; in other embodiments, it may comprise about 5, 10, 15, 20, or 25 mM HEPES. The elution buffer may have a pH of about 6.0 to 9.0. For example, in one embodiment, the elution buffer may have a pH of about 7.0 to 8.0; in other embodiments, it may have a pH of about 7.0, 7.5, or 8.0. In one embodiment, the elution buffer comprises about 40-80 mM phosphate ions (increasing in a gradient), 20 mM HEPES, and has a pH of about 7.5. Elution conditions include, but are not limited to, the properties of an elution buffer suitable for use with the HA resin (such as buffer composition, pH, concentration, ionic strength, and the like); any necessary step or gradient changes in the properties of the elution buffer; the number of column volumes of elution buffer to be used; the flow rate, and the like, which can be determined to optimize elution of the antibody of interest from the HA column and separation of the antibody of interest from impurity molecules. After elution, one or more peak fractions containing the antibody of interest are collected individually or separately as needed and optionally combined, the pH is adjusted as needed, filtered as needed, and then stored as needed before additional processing. The collected peak fractions can be identified by any suitable method, such as using UV at A280 for identification and starting collection when the UV signal is above a desired amount and / or when at a desired point in the elution conditions. The material eluted from the HA resin and containing the antibody of interest may be referred to herein as a "purified fraction" or similar term, as appropriate. A purified fraction may comprise material from a single fraction eluted from the HA resin, or it may be a combination of multiple fractions eluted from the HA resin that have been combined together. Typically, purified fractions are prepared so that a balance is struck between collecting a large amount of the antibody of interest and a small amount of impurity molecules. These competing goals must often be balanced, for example, because there may be at least a fraction overlap between the conditions when the antibody of interest is eluted from the HA resin and when an impurity molecule is eluted from the HA resin. Any buffer used in the methods provided herein (e.g., equilibration buffer, loading buffer, wash buffer, or elution buffer) may also contain additional or alternative suitable components such as acetate, succinate, MES, ACES, MOPSO, PIPES, BES, TAPSO, AMPSO, TRICINE, EPPS, Bicine, DIPSO, HEPPSO, imidazole, Tris, Bis-tris, TAPS, arginine, glycine, acetonitrile, ethanol, methanol, 1% sodium lauryl sulfate (SDS), or other surfactants and the like. In some embodiments, any buffer provided herein can have a pH of about 6.0 to 9.0. In other embodiments, any buffer provided herein can have a pH of about 5.0 to 9.0, 5.5 to 9.0, 6.5 to 9.0, 7.0 to 9.0, 7.5 to 9.0, 7.0 to 8.0, or 6.5 to 8.5. In buffers described herein as comprising "phosphate ions," the phosphate ions can be generated in the buffer from any suitable phosphate salt, such as sodium phosphate or potassium phosphate. In addition, solutions described herein as being prepared with "sodium phosphate" can be prepared with any suitable sodium phosphate salt, such as sodium dihydrogen phosphate or disodium hydrogen phosphate. After the antibody of interest has been eluted from the HA column, the HA column is optionally cleaned to remove impurities and other components that degrade the column resin and prepared for subsequent storage. In one embodiment, the column is first regenerated using a buffer (such as a buffer containing sodium phosphate at a concentration of about 0.4 M and a pH of about 7.5); an optional sanitization step is then performed using a cleaning solution (such as about 1 M NaOH and about 0.5 M potassium phosphate), and then prepared for storage using a storage solution (such as about 0.1 M NaOH). Antibodies The methods provided herein can be used to purify an antibody of interest from one or more impurities. For example, the purified antibody can be used as a pharmaceutical or in the preparation of a pharmaceutical. In some embodiments, the antibodies purified according to the methods provided herein are any type of antibodies provided herein. For example, the antibodies purified according to the methods provided herein can be full-length antibodies or antibody fragments (e.g., scFv or Fab), and they can be monospecific or bispecific. Typically, the antibodies of interest purified according to the methods provided herein are recombinant antibodies. IgG Antibodies In some embodiments, the antibodies purified according to the methods provided herein are immunoglobulin G (IgG) antibodies. As is known in the art, IgG antibodies comprise two heavy chains and two light chains and have a general "Y" shape. In a standard IgG molecule, the two heavy chains have the same amino acid sequence, and the two light chains have the same amino acid sequence. IgG antibodies can be described as having two "arms" (i.e., a "first arm" and a "second arm"), each of which comprises a heavy chain and a light chain linked together by a disulfide bond. In a standard IgG molecule, the first arm of the antibody is identical to the second arm of the antibody (due to each arm comprising a heavy chain and a light chain, each having the same amino acid sequence as the heavy chain and light chain in the other arm). The N-terminal region of the heavy chain comprises the heavy chain variable region (VH), and the N-terminal region of the light chain comprises the light chain variable region (VL). The VH and VL regions comprise the portion of the antibody that specifically binds to the antigen. Thus, each arm of the IgG antibody can specifically bind to the antigen. In a standard IgG molecule, both the first and second arms of the IgG antibody bind to the same antigen (due to the fact that both arms contain heavy and light chains with the same respective amino acid sequences). Based on having two identical arms, standard IgG antibodies can be referred to as "homodimeric." IgG antibodies purified according to the methods provided herein can be of subclass IgG1, IgG2, IgG3, or IgG4. Bispecific IgG In some embodiments, the antibodies purified according to the methods provided herein are bispecific IgG antibodies. In a bispecific IgG antibody, each of the two arms of the antibody specifically binds to a different antigen. In addition, the amino acid sequence of the heavy chain in the first arm of the bispecific IgG antibody is different from the amino acid sequence of the heavy chain in the second arm of the same bispecific IgG antibody, and similarly, the amino acid sequence of the light chain in the first arm of the bispecific IgG antibody is generally different from the amino acid sequence of the light chain in the second arm of the same bispecific IgG antibody. Therefore, based on having two different arms, bispecific IgG antibodies can be referred to as "heterodimers." The first arm of the bispecific IgG antibody can be described as having specificity for the "first antigen," and the second arm of the bispecific IgG antibody can be described as having specificity for the "second antigen." In some embodiments, the bispecific antibodies have IgG1, IgG2, IgG3, or IgG4 isotypes. In some embodiments, the bispecific antibodies comprise an immunologically inert Fc region. Bispecific IgG Antibody - Preparation Methods Methods for preparing bispecific antibodies are known in the art (see, e.g., Suresh et al., Methods in Enzymology 121:210, 1986). Traditionally, recombinant production of bispecific antibodies is based on the co-expression of two immunoglobulin heavy chain-light chain pairs, where the two heavy chains have different specificities (Millstein and Cuello, Nature 305, 537-539, 1983). Recently, methods have been developed for producing bispecific heterodimeric antibodies using the following general steps: 1) A first homodimeric antibody (also referred to herein as the "first parent antibody") and a second homodimeric antibody (also referred to herein as the "second parent antibody") are separately expressed and purified. The first homodimeric antibody is specific for the first target antigen of the bispecific antibody being produced, and the second homodimeric antibody is specific for the second target antigen of the bispecific antibody being produced. Thus, for example, if the goal is to produce a bispecific antibody specific for BCMA and CD3, a monoclonal anti-BCMA antibody (the "first parent antibody") and a monoclonal anti-CD3 antibody (the "second parent antibody") are separately expressed and purified. 2) Next, the purified first homodimer / parent antibody and the purified second homodimer / parent antibody are mixed and cultured together under conditions that promote antibody arm exchange, so that a heterodimeric bispecific antibody comprising a first arm from the first parent antibody and a second arm from the second parent antibody is formed. These conditions typically involve a series of reducing conditions followed by oxidizing conditions. The reducing conditions promote the cleavage of the disulfide bonds that connect the two heavy chains of the homodimeric antibody, thereby allowing the exchange of antibody arms between the first and second parent antibodies. The subsequent oxidizing conditions form new disulfide bonds that stabilize the newly formed bispecific antibody. This general method for producing bispecific antibodies is summarized in Figure 1. In Figure 1, a first parent antibody ("parent antibody A"; gray) and a second parent antibody ("parent antibody B"; black) are depicted, each of which is a monospecific homodimer and comprises a first arm and a second arm. Typically, the first and second parent antibodies are specific for different antigens. The first and second parent antibodies are then mixed together and exposed to reduction and oxidation steps, resulting in the formation of the bispecific antibody of interest comprising a first arm from parent antibody A and a second arm from parent antibody B, and the respective specificities of both arms. Optionally, the amino acid sequence of the antibody heavy chain can be modified in one or more ways to promote the formation of bispecific antibodies. For example, the heavy chain of one arm of a bispecific antibody may include amino acid modifications in the first hinge region so that the substituted / replaced amino acid in the first hinge region has a charge opposite to that of the corresponding amino acid in the hinge region of the other arm of the formed bispecific antibody. This is described in, for example, International Patent Application No. PCT / US2011 / 036419 (WO2011 / 143545). In another method, the formation of a desired heteromultimer or heterodimer protein (e.g., a bispecific antibody) is enhanced by changing or transforming the interface between the first and second immunoglobulin-like Fc regions (e.g., hinge region and / or CH3 region). In this method, the bispecific antibody may comprise a CH3 region, wherein the CH3 region comprises a first CH3 polypeptide and a second CH3 polypeptide, which together interact to form a CH3 interface, wherein one or more amino acids within the CH3 interface destabilize homodimer formation and are not electrostatically unfavorable for homodimer formation. This method is also described in International Patent Application No. PCT / US2011 / 036419 (WO2011 / 143545). The above methods and other methods for preparing bispecific antibodies are further described in, for example, International Patent Application Nos. PCT / IB2011 / 054899 (WO2012 / 059882), PCT / US2011 / 036419 (WO2011 / 143545), and Giese et al., Biotechnology Progress, "Bispecific Antibody Process Development: Assembly and Purification of Knob and Hole Bispecific Antibodies," January 17, 2018, and references cited therein, each of which is incorporated herein by reference for all purposes. The methods for purifying antibodies provided herein can be used to purify bispecific antibodies prepared by any suitable method. Bispecific IgG Antibody - Specificity In some embodiments, the antibodies that can be purified according to the methods provided herein are full-length human bispecific IgG antibodies, wherein the first antibody variable domain of the first arm of the bispecific antibody is capable of binding to a first antigen, and the second antibody variable domain of the second arm of the bispecific antibody is capable of binding to a second antigen. The first and second antigens may have any of the characteristics of the antigens described herein. In some embodiments, the first antigen is present on a first cell type, and the second antigen is present on a second cell type. In some embodiments, the antibodies that can be purified according to the methods provided herein are fully human bispecific IgG antibodies, wherein the first antibody variable domain of the antibody is capable of recruiting the activity of human immune effector cells by specifically binding to an effector antigen located on the human immune effector cells, and wherein the second antibody variable domain of the antibody is capable of specifically binding to the target antigen. The human immune effector cells that can be bound by the antibodies provided herein can be any of a variety of immune effector cells known in the art. For example, immune effector cells can be members of human lymphocyte lineages, including but not limited to T cells (e.g., cytotoxic T cells), B cells, and natural killer (NK) cells. Immune effector cells can also be members of, for example, human bone marrow lineages, including but not limited to monocytes, neutrophils, and dendritic cells. Such immune effector cells can have cytotoxic or apoptotic effects on target cells or have other desired effects after activation by the combination of effector antigens. The effector antigen is an antigen (e.g., protein or polypeptide) expressed on human immune effector cells. Examples of effector antigens that can be bound by the antibodies provided herein include but are not limited to human CD3 (or CD3 (differentiation cluster) complex), CD16, NKG2D, NKp46, CD2, CD28, CD25, CD64, and CD89. Target antigens are expressed on target cells in disease conditions (e.g., inflammatory diseases, proliferative diseases (e.g., cancer), immune diseases, neurological diseases, neurodegenerative diseases, autoimmune diseases, infectious diseases (e.g., viral or parasitic infections, allergic reactions, graft-versus-host disease, or host-versus-graft disease). Target antigens are not effector antigens. Examples of target antigens include, but are not limited to, BCMA, EpCAM (epithelial cell adhesion molecule), CCR5 (chemokine receptor type 5), CD19, HER (human epidermal growth factor receptor)-2 / neu, HER-3, HER-4, EGFR (epidermal growth factor receptor), FLT3 (Fms-like tyrosine kinase 3), PSMA, CEA, MUC-1 (mucin), MUC2, MUC3, MUC4, MUC5AC, MUC5B, MUC7, CIhCG, Lewis-Y, CD20, CD33, CD30, ganglioside GD3, 9-O-acetyl-GD3, GM2, Globo H, fucosyl GM1, Poly SA, GD2, carbonic anhydrase IX (MN / CA IX), CD44v6, Shh (Sonic Hedgehog), Wue-1, plasma cell antigen, (membrane-bound) IgE, MCSP (melanoma chondroitin sulfate proteoglycan), CCR8, TNF-α precursor, STEAP, mesothelin, A33 antigen, PSCA (prostate stem cell antigen), Ly-6; desmosome 4, E-cadherin neoantigen, fetal acetylcholine receptor, CD25, CA19-9 marker, CA-125 marker, and type II MIS (Muellerian inhibitory substance) receptor, sTn (sialyl Tn antigen; TAG-72), FAP (fibroblast activation antigen), endosialin, EGFRvIII, LG, SAS and CD63. In some embodiments, the antibody purified according to the methods provided herein may be any antibody described in U.S. application Ser. No. 15 / 085,644, filed Mar. 30, 2016 (Pub. No. US20160297885), or U.S. application Ser. No. 15 / 993,874, filed May 31, 2018 (Pub. No. US20180346601), which are incorporated herein by reference in their entireties for all purposes. In some embodiments, the antibodies purified according to the methods provided herein can be bispecific IgG antibodies in which one arm of the antibody specifically binds to cluster of differentiation 3 (CD3). Information about CD3 is provided, for example, by UniProtKB ID # P07766. In some embodiments, in a bispecific IgG antibody wherein one arm of the antibody specifically binds to CD3, the VH region of the heavy chain of the CD3-binding arm has an amino acid sequence comprising the following amino acid sequence: EVQLVESGGGLVQPGGSLRLSCAASGFTFSDYYMTWVRQAPGKGLEWVAFIRNRARGYTSDHNPSVKGRFTISRDNAKNSLYLQMNSLRAEDTAVYYCARDRPSYYVLDYWGQGTTVTVSS (SEQ ID NO: 1). In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to CD3, the heavy chain of the CD3-binding arm has an amino acid sequence comprising the following amino acid sequence: EVQLVESGGGLVQPGGSLRLSCAASGFTFSDYYMTWVRQAPGKGLEWVAFIRNRARGYTSDHNPSVKGRFTISRDNAKNSLYLQMNSLRAEDTAVYYCARDRPSYYVLDYWGQGTTVTVSSastkgpsvfplapcsrstsestaalgclvkdyfpepvtvswnsgaltsgvhtfpavlqssglyslssvvt vpssnfgtqtytcnvdhkpsntkvdktverkcrvrcprcpappvagpsvflfppkpkdtlmisrtpevtcvvvavshedpevqfnwyvdgvevhnaktkpreeqfnstfrvvsvltvvhqdwlngkeykckvsnkglpssiektisktkgqprepqvytlppsreemtknqvsltclvkgfypsdiavewesngqpennykttppmldsdgsfflysrltvdksrwqqgnvfscsvmhealhnhytqkslslspgk (SEQ ID NO: 2). In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to CD3, the VH region of the heavy chain of the CD3-binding arm has an amino acid sequence comprising CDR1, CDR2, and CDR3 of the VH sequence shown in SEQ ID NO: 1. In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to CD3, the VL region of the light chain of the CD3-binding arm has an amino acid sequence comprising the following amino acid sequence: DIVMTQSPDSLAVSLGERATINCKSSQSLFNVRSRKNYLAWYQQKPGQPPKLLISWASTRESGVPDRFSGSGSGTDFTLTISSLQAEDVAVYYCKQSYDLFTFGSGTKLEIK (SEQ ID NO: 3). In some embodiments, in a bispecific IgG antibody wherein one arm of the antibody specifically binds to CD3, the light chain of the CD3-binding arm has an amino acid sequence comprising the following amino acid sequence: DIVMTQSPDSLAVSLGERATINCKSSQSLFNVRSRKNYLAWYQQKPGQPPKLLISWASTRESGVPDRFSGSGSGTDFTLTISSLQAEDVAVYYCKQSYDLFTFGSGTKLEIKrtvaapsvfifppsdeqlksgtasvvcllnnfypreakvqwkvdnalqsgnsqesvteqdskdstyslsstltlskadyekhkvyacevthqglsspvtksfnrgec (SEQ ID NO: 4). In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to CD3, the VL region of the light chain of the CD3-binding arm has an amino acid sequence comprising CDR1, CDR2, and CDR3 of the VL sequence shown in SEQ ID NO: 3. In some embodiments, in a bispecific IgG antibody wherein one arm of the antibody specifically binds to CD3, the VH region of the heavy chain of the CD3-binding arm has an amino acid sequence comprising the amino acid sequence shown in SEQ ID NO: 1, and the VL region of the light chain of the CD3-binding arm has an amino acid sequence comprising the amino acid sequence shown in SEQ ID NO: 3. In some embodiments, in a bispecific IgG antibody wherein one arm of the antibody specifically binds to CD3, the heavy chain of the CD3-binding arm has an amino acid sequence comprising the amino acid sequence shown in SEQ ID NO: 2, and the light chain of the CD3-binding arm has an amino acid sequence comprising the amino acid sequence shown in SEQ ID NO: 4. In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to CD3, the VH region of the heavy chain of the CD3-binding arm has an amino acid sequence comprising CDR1, CDR2, and CDR3 of the VH sequence shown in SEQ ID NO: 1, and the VL region of the light chain of the CD3-binding arm has an amino acid sequence comprising CDR1, CDR2, and CDR3 of the VL sequence shown in SEQ ID NO: 3. In some embodiments, the antibodies purified according to the methods provided herein may be bispecific IgG antibodies in which one arm of the antibody specifically binds to B-cell mutant antigen (BCMA). Information about BCMA is provided by, for example, UniProtKB ID # Q02223. In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to BCMA, the VH region of the heavy chain of the BCMA-binding arm has an amino acid sequence comprising the following amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYPMSWVRQAPGKGLEWVSAIGGSGGSLPYADIVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARYWPMDIWGQGTLVTVSS (SEQ ID NO: 5). In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to BCMA, the heavy chain of the BCMA-binding arm has an amino acid sequence comprising the following amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYPMSWVRQAPGKGLEWVSAIGGSGGSLPYADIVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARYWPMDIWGQGTLVTVSSastkgpsvfplapcsrstsestaalgclvkdyfpepvtvswnsgaltsgvhtfpavlqssglyslssvvtv In some embodiments, in a bispecific IgG antibody wherein one arm of the antibody specifically binds to BCMA, the VH region of the heavy chain of the BCMA-binding arm has an amino acid sequence comprising CDR1, CDR2, and CDR3 of the VH sequence shown in SEQ ID NO: 5. In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to BCMA, the VL region of the light chain of the BCMA-binding arm has an amino acid sequence comprising the following amino acid sequence: EIVLTQSPGTLSLSPGERATLSCRASQSVSSSYLAWYQQKPGQAPRLLMYDASIRATGIPDRFSGSGSGTDFTLTISRLEPEDFAVYYCQQYQSWPLTFGQGTKVEIK (SEQ ID NO: 7). In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to BCMA, the light chain of the BCMA-binding arm has an amino acid sequence comprising the following amino acid sequence: EIVLTQSPGTLSLSPGERATLSCRASQSVSSSYLAWYQQKPGQAPRLLMYDASIRATGIPDRFSGSGSGTDFTLTISRLEPEDFAVYYCQQYQSWPLTFGQGTKVEIKrtvaapsvfifppsdeqlksgtasvvcllnnfypreakvqwkvdnalqsgnsqesvteqdskdstyslsstltlskadyekhkvyacevthqglsspvtksfnrgec (SEQ ID NO: 8). In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to BCMA, the VL region of the light chain of the BCMA-binding arm has an amino acid sequence comprising CDR1, CDR2, and CDR3 of the VL sequence shown in SEQ ID NO: 7. In some embodiments, in a bispecific IgG antibody wherein one arm of the antibody specifically binds to BCMA, the VH region of the heavy chain of the BCMA-binding arm has an amino acid sequence comprising the amino acid sequence shown in SEQ ID NO: 5, and the VL region of the light chain of the BCMA-binding arm has an amino acid sequence comprising the amino acid sequence shown in SEQ ID NO: 7. In some embodiments, in a bispecific IgG antibody wherein one arm of the antibody specifically binds to BCMA, the heavy chain of the BCMA-binding arm has an amino acid sequence comprising the amino acid sequence shown in SEQ ID NO: 6, and the light chain of the BCMA-binding arm has an amino acid sequence comprising the amino acid sequence shown in SEQ ID NO: 8. In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to BCMA, the VH region of the heavy chain of the BCMA-binding arm has an amino acid sequence comprising CDR1, CDR2, and CDR3 of the VH sequence shown in SEQ ID NO: 5, and the VL region of the light chain of the BCMA-binding arm has an amino acid sequence comprising CDR1, CDR2, and CDR3 of the VL sequence shown in SEQ ID NO: 7. In some embodiments, in a bispecific IgG antibody wherein one arm of the antibody specifically binds to BCMA, the VH region of the heavy chain of the BCMA-binding arm has an amino acid sequence comprising the following amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYPMSWVRQAPGKGLEWVSAIGgSGGSLPYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARYWPMDIWGQGTLVTVSS (SEQ ID NO: 13). In some embodiments, in a bispecific IgG antibody wherein one arm of the antibody specifically binds to BCMA, the VL region of the light chain of the BCMA-binding arm has an amino acid sequence comprising the following amino acid sequence: EIVLTQSPGTLSLSPGERATLSCRASQSVSSTYLAWYQQKPGQAPRLLMYDASIRATGIPDRFSGSGSGTDFTLTISRLEPEDFAVYYCQQYQEWPLTFGQGTKVEIK (SEQ ID NO: 14). In some embodiments, where any of the antibodies described herein comprise a VH region comprising the amino acid sequence set forth in SEQ ID NO: 5, the antibody may alternatively comprise a VH region comprising the amino acid sequence set forth in SEQ ID NO: 13. In some embodiments, where any of the antibodies described herein comprise a VL region comprising the amino acid sequence set forth in SEQ ID NO: 7, the antibody may alternatively comprise a VL region comprising the amino acid sequence set forth in SEQ ID NO: 14. Similarly, anti-BCMA heavy and light chains comprising the VH and VL sequences of SEQ ID NO: 13 and SEQ ID NO: 14, respectively, are also encompassed herein. In some embodiments, the antibodies purified according to the methods provided herein can be bispecific IgG antibodies, wherein one arm of the antibody specifically binds to fms-like tyrosine kinase 3 (FLT3). Information about FLT3 is provided by, for example, UniProtKB ID # P36888. In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to FLT3, the VH region of the heavy chain of the FLT3-binding arm has an amino acid sequence comprising the following amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMNWVRQAPGKGLEWVSAISGGGRSTYYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARDLSPSDVGWGYGFDIWGQGTLVTVSS (SEQ ID NO: 9). In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to FLT3, the heavy chain of the FLT3-binding arm has an amino acid sequence comprising the following amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMNWVRQAPGKGLEWVSAISGGGRSTYYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARDLSPSDVGWGYGFDIWGQGTLVTVSSASTKGPSVFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLS SVVTVPSSNFGTQTYTCNVDHKPSNTKVDKTVERKCEVECPECPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVVAVSHEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTFRVVSVLTVVHQDWLNGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTCEVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPG (SEQ ID NO: 10). In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to FLT3, the VH region of the heavy chain of the FLT3-binding arm has an amino acid sequence comprising CDR1, CDR2, and CDR3 of the VH sequence shown in SEQ ID NO: 9. In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to FLT3, the VL region of the light chain of the FLT3-binding arm has an amino acid sequence comprising the following amino acid sequence: EIVLTQSPATLSLSPGERATLSCRASQSVSSNLAWYQQKPGQAPRLLIYDTFTRATGIPARFSGSGSGTDFTLTISSLEPEDFAVYYCQQYGSSPPTFGQGTRLEIK (SEQ ID NO: 11). In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to FLT3, the light chain of the FLT3-binding arm has an amino acid sequence comprising the following amino acid sequence: EIVLTQSPATLSLSPGERATLSCRASQSVSSNLAWYQQKPGQAPRLLIYDTFTRATGIPARFSGSGSGTDFTLTISSLEPEDFAVYYCQQYGSSPPTFGQGTRLEIKRTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 12). In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to FLT3, the VL region of the light chain of the FLT3-binding arm has an amino acid sequence comprising CDR1, CDR2, and CDR3 of the VL sequence shown in SEQ ID NO: 11. In some embodiments, in a bispecific IgG antibody wherein one arm of the antibody specifically binds to FLT3, the VH region of the heavy chain of the FLT3-binding arm has an amino acid sequence comprising the amino acid sequence set forth in SEQ ID NO: 9, and the VL region of the light chain of the FLT3-binding arm has an amino acid sequence comprising the amino acid sequence set forth in SEQ ID NO: 11. In some embodiments, in a bispecific IgG antibody wherein one arm of the antibody specifically binds to FLT3, the heavy chain of the FLT3-binding arm has an amino acid sequence comprising the amino acid sequence set forth in SEQ ID NO: 10, and the light chain of the FLT3-binding arm has an amino acid sequence comprising the amino acid sequence set forth in SEQ ID NO: 12. In some embodiments, in a bispecific IgG antibody in which one arm of the antibody specifically binds to FLT3, the VH region of the heavy chain of the FLT3-binding arm has an amino acid sequence comprising CDR1, CDR2, and CDR3 of the VH sequence shown in SEQ ID NO: 9, and the VL region of the light chain of the FLT3-binding arm has an amino acid sequence comprising CDR1, CDR2, and CDR3 of the VL sequence shown in SEQ ID NO: 11. In some embodiments, provided herein are bispecific anti-BCMA / anti-CD3 antibodies, wherein the anti-BCMA arm of the antibody has any of the features described above for the anti-BCMA arm, and the anti-CD3 arm of the antibody has any of the features described above for the anti-CD3 arm. In some embodiments, provided herein are bispecific anti-FLT3 / anti-CD3 antibodies, wherein the anti-FLT3 arm of the antibody has any of the features described above for the anti-FLT3 arm, and the anti-CD3 arm of the antibody has any of the features described above for the anti-CD3 arm. Also provided herein are methods for purifying monospecific antibodies having affinity for any of the above antigens and / or comprising any of the above amino acid sequences. For example, also provided herein are methods for purifying monospecific, homodimeric anti-CD3 antibodies comprising the VH amino acid sequence shown in SEQ ID NO: 1. Impurities The methods provided herein can be used to purify an antibody of interest from one or more impurities. Impurities include, for example, trimmed forms of the antibody of interest, protein aggregates, and, in the case of bispecific antibodies of interest, parent monospecific antibodies associated with the formation of the bispecific antibody of interest. These different impurities may also be referred to herein as different "impurity species," "impurity molecules," or similar terms. Trimmed Forms of Antibodies of Interest "Trimmed forms of antibodies of interest," "trimmed antibodies," or similar terms refer to recombinant antibodies in which one or more polypeptide bonds in the antibody have been cleaved compared to the corresponding intact antibody of interest. In contrast, an "intact" antibody refers to a recombinant antibody that contains all expected peptide bonds and amino acids of the recombinant antibody (i.e., as expected based on the nucleic acid sequence encoding the polypeptide of the antibody). Thus, trimmed antibodies can be considered degradation products associated with the antibody of interest.Cleavage of peptide bonds in antibodies can occur, for example, by enzymatic (eg, protease-mediated) or non-enzymatic activities. In some embodiments, when a peptide bond in an antibody polypeptide is cleaved, the cleaved portion of the polypeptide chain may no longer be covalently attached to the rest of the antibody after cleavage; in this case, the cleaved portion of the polypeptide chain may dissociate from the rest of the antibody. This most commonly occurs when cleaving a peptide bond located near the N- or C-terminus of an α polypeptide chain, and results in a trimmed antibody that has lost one or more amino acids compared to the corresponding intact antibody. Due to the loss of one or more amino acids in the antibody, these trimmed antibodies have less mass than the corresponding intact antibody. Alternatively, in some other embodiments, when a peptide bond in an antibody polypeptide is cleaved, the cleaved portion of the polypeptide chain may remain covalently attached to the rest of the antibody after cleavage (e.g., via an intra- or inter-chain disulfide bond). In this case, even after the peptide bond of the antibody is cleaved, the cleaved portion of the polypeptide chain will remain tethered to the rest of the antibody via the intact covalent bond connecting the cleaved portion of the polypeptide chain to the rest of the antibody. In this case, the trimmed antibody will still have the same number of amino acids and amino acid sequence as the intact antibody. Additionally, in at least some embodiments, this type of trimmed antibody may have a slightly greater mass than the corresponding intact antibody. This increase in mass may be the result of one or more chemical reactions that occur upon peptide bond cleavage. In these reactions, one or more atoms (e.g., H, O) may react with atoms of the antibody polypeptide chain and become covalently attached to the antibody chain, resulting in an increase in the mass of the trimmed antibody compared to the corresponding intact antibody. Since "trimmed" antibodies are generated from corresponding "intact" antibodies, the "trimmed" form of the antibody has the same amino acid sequence (no amino acids are lost in the antibody due to peptide bond cleavage) or almost the same amino acid sequence (one or more amino acid sequences are lost in the antibody due to peptide bond cleavage) as the corresponding "intact" form of the antibody. Typically, a trimmed form of an antibody has a mass similar to that of the corresponding intact antibody. As described above, in some embodiments, a trimmed antibody may have a mass less than that of the corresponding intact antibody (e.g., where trimming results in the loss of one or more amino acids from the antibody). Alternatively, in some embodiments, a trimmed antibody may have a mass greater than that of the corresponding intact antibody (where trimming does not result in the loss of any amino acids from the antibody, but rather results in the gain of at least one atom through one or more reactions resulting from peptide bond cleavage). In some embodiments, the mass of the trimmed form of an antibody differs by no more than 50%, 40%, 30%, 25%, 20%, 15%, 10%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, 0.05%, 0.04%, 0.03%, 0.02%, or 0.01% from the mass of the corresponding intact antibody of interest. In other words, in some embodiments, the mass of the trimmed form of an antibody of interest differs by no more than 50%, 40%, 30%, 25%, 20%, 15%, 10%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, 0.05%, 0.04%, 0.03%, 0.02%, or 0.01% from the mass of the corresponding intact antibody of interest. As described above, in some embodiments, the trimmed form of an antibody of interest has a mass that is less than the mass of the corresponding intact antibody of interest. For example, in some embodiments, the mass of the trimmed form of an antibody is no more than 50%, 40%, 30%, 25%, 20%, 15%, 10%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, 0.05%, 0.04%, 0.03%, 0.02%, 0.01% less than the mass of the corresponding intact antibody of interest. In other words, if the mass of the trimmed form of an antibody is no more than 10% less than the mass of the corresponding intact antibody of interest, for example, if the mass of the intact antibody of interest is 100,000 Da, then the mass of the trimmed form of the antibody is no more than 10,000 Da less than 100,000 Da (10% of 100,000 is 10,000) - i.e., it has a mass between 90,000 Da and 100,000 Da. As also described above, in some embodiments, the trimmed form of an antibody of interest has a mass greater than the corresponding intact antibody of interest. For example, in some embodiments, the mass of the trimmed form of an antibody is no more than 5%, 4%, 3%, 2%, 1%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, 0.05%, 0.04%, 0.03%, 0.02%, or 0.01% greater than the mass of the corresponding intact antibody of interest. In other words, if the mass of the trimmed form of an antibody is no more than 1% greater than the mass of the corresponding intact antibody of interest, for example, if the mass of the intact antibody of interest is 100,000 Da, then the mass of the trimmed form of the antibody is no more than 1,000 Da greater than 100,000 Da (1% of 100,000 is 1,000) - i.e., it has a mass between 100,000 Da and 101,000 Da. High molecular weight substances (HMMS) / Protein Aggregates In some embodiments, impurities associated with the methods provided herein are referred to as "high molecular mass species" (HMMS). HMMS refers to any high molecular mass contaminant or impurity, but is typically an association of at least two proteins that form an aggregate. For example, HMMS can include aggregates of multiple molecules of an antibody of interest and / or aggregates of proteins from host cells used to produce the antibody of interest. Aggregates can be generated by any method, including, for example, covalent or non-covalent attachment of molecules. Parent Antibodies In some embodiments, impurities associated with the methods provided herein are "parent antibodies" or similar terms. This type of impurity molecule is relevant to the methods provided herein where the antibody of interest is a bispecific antibody produced from two different parent antibodies, for example, as outlined in FIG1 . These parent antibodies are monospecific, homodimers. Parent antibodies may be present in an antibody preparation with the bispecific antibody of interest due to a variety of possible mechanisms, such as: i) in some cases, some parent antibody molecules do not separate into the first and second arms during the reduction step, separating the parent antibodies into single first and second arms (and thus, the antibodies remain as monospecific homodimers); or ii) in some cases, separate first and second arms from parent antibodies of the same type are linked together such that they form a monospecific homodimer (rather than participating in the formation of a heterodimeric bispecific antibody). As used herein, "parent antibody" refers to a homodimeric molecule produced by any of the above mechanisms. Additionally, antibody preparations as provided herein may contain parent antibodies from one or both parents as impurities. Purification of an Antibody of Interest from Impurities Provided herein are methods for purifying an antibody of interest from one or more impurities. In some embodiments, in the methods provided herein, the antibody of interest is in the form of an antibody preparation (also referred to herein as a "starting sample") comprising the antibody of interest and one or more impurity molecules. In the starting material for the methods provided herein, the antibody of interest may comprise, for example, at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90% or 95% (by mass) of the protein in the antibody preparation. Then, in some embodiments of the methods provided herein, the purified fractions (also referred to herein as "purified samples") are collected as eluates from the HA resin. The purified fractions comprise the antibody of interest and, in some embodiments, still comprise one or more impurity molecules. In some embodiments, in the purified fractions provided herein, the antibody of interest may comprise, for example, at least about 20%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% (by mass) of the protein in the purified fractions. In some embodiments, in the methods provided herein, the starting sample is at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, or 95% by mass of the antibody of interest, and a subsequent purified sample in the same method is at least about 20%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% by mass of the antibody of interest, wherein the second value is greater than the first value. In some embodiments, in the methods provided herein, the starting sample comprises at least about 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, or 25% by mass of the trimmed form of the antibody of interest. In some embodiments, in the methods provided herein, the purified sample comprises no more than about 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, or 20% by mass of the trimmed form of the antibody of interest. In some embodiments, in the methods provided herein, the starting sample comprises at least about 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, or 25% by mass of the trimmed form of the antibody of interest, and subsequent purified samples in the same method comprise no more than about 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, or 20% by mass of the trimmed form of the antibody of interest, wherein the second value is less than the first value. In some embodiments, in the methods provided herein, the starting sample comprises an intact antibody of interest and a trimmed form of the antibody of interest, wherein the ratio of trimmed antibody to intact antibody is at least about 1:100, 1:50, 1:25, 1:20, 1:10, 1:5, 1:4, or 1:3. In some embodiments, in the methods provided herein, the purified sample comprises an intact antibody of interest and a trimmed form of the antibody of interest, wherein the ratio of trimmed antibody to intact antibody is no more than about 1:100, 1:50, 1:25, 1:20, or 1:10. In some embodiments, in the methods provided herein, the starting sample comprises an intact antibody of interest and a trimmed form of the antibody of interest, wherein the ratio of trimmed antibody to intact antibody in the starting sample is at least about 1:100, 1:50, 1:25, 1:20, 1:10, 1:5, 1:4, or 1:3 and wherein the ratio of trimmed antibody to intact antibody in a subsequent purified sample in the same method does not exceed about 1:200, 1:100, 1:50, 1:25, 1:20, or 1:10, wherein the second ratio is less than the first ratio. In some embodiments, in the methods provided herein, the starting sample comprises an intact antibody of interest and a trimmed form of the antibody of interest, wherein the ratio of trimmed antibodies to intact antibodies in the starting sample is between about one ratio in Group A (Group A ratios: 1:100, 1:50, 1:25, 1:20, 1:10, 1:5, or 1:4) and one ratio in Group B (Group B ratios: 1:50, 1:25, 1:20, 1:10, 1:5, 1:4, or 1:3) and wherein the ratio of trimmed antibodies to intact antibodies in subsequent purified samples in the same method does not exceed about 1:200, 1:100, 1:50, 1:25, 1:20, or 1:10, wherein the ratio in the purified sample is less than that in the starting sample. In some embodiments, the starting sample provided according to the methods provided herein comprises at least 1, 5, 10, 15, 20, 25, 50, 100, 200, 500, 1000, 2000, 5000, or 10,000 grams of intact antibodies of interest. In some embodiments, the purified sample provided according to the methods provided herein comprises at least 1, 5, 10, 15, 20, 25, 50, 100, 200, 500, 1000, 2000, 5000, or 10,000 grams of intact antibodies of interest. In some embodiments, the starting sample provided according to the methods provided herein comprises at least 5, 10, 15, 20, 25, 50, 100, 200, 500, 1000, 2000, 5000, or 10,000 grams of intact antibodies of interest. Subsequent purified samples in the same method contain at least 1, 5, 10, 15, 20, 25, 50, 100, 200, 500, 1000, 2000, or 5000 grams of intact antibody of interest, wherein the first value is greater than the second value. In addition, any of the above descriptions regarding a) the amount of the antibody of interest in the starting sample or purified sample or b) purity can be used with reference to the same sample. For example, as described above, the starting sample can contain at least about 80% by mass of the antibody of interest; further, as also described above, the starting sample can contain at least about 10 grams of the antibody of interest. Thus, starting samples comprising at least about 80% by mass of the antibody of interest and at least 10 grams of the antibody of interest are also provided herein. General Techniques The practice of the present invention will employ, unless otherwise indicated, conventional techniques of molecular biology (including recombinant techniques), microbiology, cell biology, biochemistry, and immunology, which are within the skill of the art. Such techniques are fully explained in the literature, for example, in Molecular Cloning: A Laboratory Manual, 2nd ed. (Sambrook et al., 1989) Cold Spring Harbor Press; Oligonucleotide Synthesis (MJ Gait, ed., 1984); Methods in Molecular Biology, Humana Press; Cell Biology: A Laboratory Notebook (JE Cellis, ed., 1998) Academic Press; Animal Cell Culture (RI Freshney, ed., 1987); Introduction to Cell and Tissue Culture (JP Mather and PE Roberts, 1998) Plenum Press; Cell and Tissue Culture: Laboratory Procedures (A. Doyle, JB Griffiths and DG Newell, eds., 1993-1998) J. Wiley & Sons; Methods in Enzymology (Academic Press, Inc.); Handbook of Experimental Immunology (DM Weir and CC Blackwell, eds.); Gene Transfer Vectors for Mammalian Cells (JM Miller and MP Calos, 1987); Current Protocols in Molecular Biology (F. M. Ausubel et al., 1987); PCR: The Polymerase Chain Reaction (Mullis et al., 1994); Current Protocols in Immunology (J. E. Coligan et al., 1991); Short Protocols in Molecular Biology (Wiley and Sons, 1999); Immunobiology (C. A. Janeway and P. Travers, 1997); Antibodies (P.Finch, 1997); Antibodies: a practical approach (D. Catty, ed., IRL Press, 1988-1989); Monoclonal antibodies: a practical approach (P. Shepherd and C. Dean, eds., Oxford University Press, 2000); Using antibodies: a laboratory manual (E. Harlow and D. Lane, Cold Spring Harbor Laboratory Press, 1999); The Antibodies (M. Zanetti and J.D. Capra, eds., Harwood Academic Publishers, 1995), and subsequent versions of the above references and corresponding websites (if applicable). The following examples are provided for illustrative purposes only and are not intended to limit the scope of the present invention in any way. Indeed, various modifications of the present invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description and fall within the scope of the appended claims. Examples Examples 1 :Through cHA Resin chromatography to purify the -BCMA / anti- -CD3 Bispecific antibodies Objective: In this example, we examined methods for separating a full-length bispecific human IgG of interest from various impurities. The antibody of interest is a heterodimeric bispecific anti-BCMA / anti-CD3 antibody (i.e., one arm of the bispecific antibody is specific for BCMA and the other arm is specific for CD3). Impurities present with the bispecific antibody of interest at the start of purification include: i) a trimmed form of the full-length anti-BCMA / anti-CD3 bispecific antibody of interest; ii) a homodimeric, monospecific anti-BCMA parent antibody; iii) a homodimeric, monospecific anti-CD3 antibody; and iv) protein aggregates / high molecular mass species (HMMS). Purifying the intact bispecific antibody of interest from its trimmed form presents a particular challenge because the trimmed form contains the same number of amino acids and the same amino acid sequence as the intact bispecific antibody of interest, and its mass differs from that of the intact bispecific antibody by only 18 Daltons (Da). Specifically, the mass of the intact anti-BCMA / CD3 bispecific antibody is 148,095.5 Da, while the mass of the corresponding trimmed form of the bispecific antibody is 148,113.5 (determined by mass spectrometry). Therefore, the mass of the trimmed bispecific antibody differs from that of the intact bispecific antibody by less than 0.1% (or even less than 0.02%) (i.e., 0.1% of 148,095 Da is 148 Da; 0.02% of 148,095 Da is 29.6 Da). In other words, the mass of the trimmed bispecific antibody is 100.01% of the mass of the intact bispecific antibody of interest. Therefore, the mass of the trimmed bispecific antibody is very similar to that of the intact bispecific antibody of interest. The trimmed form of the bispecific antibody contains a cleavage in the peptide bond of the anti-CD3 heavy chain (between amino acids 56 and 57 of the heavy chain). The anti-CD3 heavy chain has the amino acid sequence set forth in SEQ ID NO: 2, and accordingly, a cleavage occurs between amino acids R and G in the "RG" sequence of SEQ ID NO: 2 ("RG" appears only once in SEQ ID NO: 2). It is believed that this cleavage results in the addition of one oxygen atom and two hydrogen atoms to the trimmed bispecific antibody compared to the intact bispecific antibody (which would correspond to an 18 Da mass increase). Furthermore, despite the presence of the cleaved peptide bond in the anti-CD3 heavy chain, the cleaved 56-amino acid portion of the heavy chain (i.e., the first 56 amino acids of the chain) remains bound to the remainder of the antibody via an intact, retained intrachain disulfide bond. The intrachain disulfide bond is located between C22 and C98 of the anti-CD3 heavy chain (i.e., C22 and C98 of the sequence set forth in SEQ ID NO: 2). The continuous tethering of the cleaved 56 amino acid portion to the rest of the antibody via intrachain peptide bonds is shown schematically in FIG2 . In Figure 2, the schematic diagram on the left depicts the complete bispecific antibody of interest, which comprises the complete heavy and light chains of the anti-CD3 and anti-BCMA arms of the bispecific antibody (in this figure, the longer chain represents the heavy chain of the antibody, and the shorter chain represents the light chain). In addition, Figure 2 also shows various intra-antibody disulfide bonds, including intrachain disulfide bonds (e.g., connecting different amino acids in the same light or heavy chain) and interchain disulfide bonds (e.g., connecting the heavy chain of the anti-BCMA arm to the heavy chain of the anti-CD3 arm, or connecting the light chain of the anti-CD3 arm to the light chain of the anti-CD3 arm). Another challenge presented in developing methods for purifying intact bispecific antibodies of interest from various impurities is the goal of developing methods that can effectively separate the bispecific antibodies of interest from impurities when purifying relatively large quantities of the bispecific antibodies of interest. For example, one goal of the work related to this example was to develop a method for purifying bispecific antibodies that would be effective for methods that purify at least 1 gram of bispecific antibodies. As is known in the art, large-scale purification of proteins often presents many difficulties that are not present (or significantly less problematic) during small-scale purification of the same protein, due to, for example, the difficulty in achieving significant chromatographic resolution between different proteins when performing chromatography on a large scale. Materials and Methods: The starting material for this work was an antibody preparation comprising the bispecific IgG anti-BCMA / CD3 antibody of interest and various impurities, such as those described above. The amino acid sequences of the bispecific antibody polypeptides are shown in the following SEQ ID NOs: BCMA heavy chain: SEQ ID NO: 6; BCMA light chain: SEQ ID NO: 8; CD3 heavy chain: SEQ ID NO: 2; CD3 light chain: SEQ ID NO: 4. As previously described herein, the bispecific antibodies of interest were prepared from two separate parent antibodies. More specifically, the parent monospecific anti-CD3 and anti-BCMA antibodies were purified by protein-A chromatography, and these purified parent monospecific anti-CD3 and anti-BCMA antibodies were used to generate the bispecific anti-BCMA / CD3 antibodies of interest. The resulting bispecific anti-BCMA / CD3 antibodies were then purified by ion exchange chromatography. The antibody preparation used as the starting material for the purification work in this example was eluted from an ion exchange column containing the bispecific antibody of interest and various residual impurities, and had a buffer / salt concentration of approximately 50 mM Tris and 60 mM glycine (pH 7.5). This antibody preparation contained over 85% (by mass) of the intact bispecific antibody of interest; it also contained approximately 8% trimmed bispecific antibody, approximately 1% monospecific anti-BCMA parent antibody, approximately 1% monospecific anti-CD3 parent antibody, and approximately 2% protein aggregates / high molecular mass species (HMMS). Therefore, although the antibody preparation used as the starting material in this method contained the intact bispecific antibody of interest, which was already relatively pure, the goal of this method was to develop a method to increase the purity of the intact bispecific antibody. Results: A variety of different chromatography resins and conditions were tested in an attempt to identify suitable resins and buffer conditions that allowed efficient purification of the intact anti-BCMA / CD3 bispecific antibody of interest from trimmed bispecific antibodies, monospecific parental antibodies, and protein aggregates. During this process, for example, a variety of different ion exchange and hydrophobic interaction resins, as well as various buffer and pH conditions, were tested. After extensive testing, hydroxyapatite resin was the only resin that allowed efficient purification of the intact anti-BCMA / CD3 bispecific antibody from a variety of impurities, including trimmed bispecific antibodies. Figure 3 shows the chromatographic profiles of the elution of the bispecific antibody of interest from a ceramic hydroxyapatite ("cHA") resin column and the simultaneous separation of the anti-BCMA / CD3 bispecific antibody of interest from a variety of impurities (including a trimmed form of the bispecific antibody, two parental antibodies, and high-molecular-weight proteinaceous species). For the chromatographic run depicted in Figure 3 , the antibody preparation loaded onto the cHA resin was supplemented with additional parental anti-BCMA and parental anti-CD3 antibodies to more clearly identify the positions at which these molecules eluted from the cHA column (however, no additional intact or trimmed bispecific antibodies were added). In Figure 3 , the X-axis depicts the sequence of eluates from the cHA column from left to right (i.e., material on the left elutes from the cHA column earlier / at lower salt than material on the right). Typically, eluate is collected from the column in successive fractions; therefore, the X-axis can also be considered to depict the order of eluate fractions from the cHA resin column. The Y-axis depicts UV absorbance (at 280 nM) and conductivity, as indicated separately in the figure. UV absorbance corresponds to the presence of eluted protein, and conductivity corresponds to the salt concentration in the eluted material. Thus, Figure 3 depicts the elution profiles of different proteins from a cHA resin column as the salt concentration in the elution buffer flowing through the cHA resin increases. Following the UV plot in Figure 3 (from left to right), the figure shows individual peaks and shoulders corresponding to either the intact bispecific anti-BCMA / CD3 antibody of interest or various impurities. Specifically, from left to right, the first UV peak corresponds to the elution of the first parent antibody ("Parent 1"; monospecific anti-BCMA homodimer). The early fraction of the next major peak (and the largest peak in the figure) corresponds to the intact bispecific antibody protein of interest ("POI"). The rear end / tail end of this same major peak corresponds to a trimmed form of the bispecific antibody ("Trim"). While there was some overlap between the elution profiles of the intact bispecific antibody and the trimmed bispecific antibody, both antibody types eluted from the cHA column under sufficiently different salt conditions and fractions to significantly separate the intact bispecific antibody from the trimmed form of the bispecific antibody. Finally, after the elution of the trimmed form of the bispecific antibody, the last major peak / shoulder on the cHA column corresponded to the elution of the second parent antibody (monospecific anti-CD3 homodimer) and high molecular mass species ("HMMS") (also known as protein aggregates) from the cHA column. Thus, the graph in FIG3 demonstrates that intact anti-BCMA / CD3 antibody can be efficiently purified from a variety of impurities, including related trimmed and parent antibody species, by chromatography on a cHA resin. Figure 4 provides a graph showing more detailed information about the different molecular species present in sequentially eluted fractions from a cHA resin column, based on the cHA elution profile depicted in Figure 3. Specifically, Figure 4 provides detailed information about the relative amounts of: i) the intact anti-BCMA / CD3 bispecific antibody protein of interest ("POI"); ii) a trimmed form of the bispecific antibody; iii) the first parent antibody / monospecific anti-BCMA antibody; iv) the second parent antibody / monospecific anti-CD3 antibody; and v) high molecular mass species ("HMMS") in different fractions eluted from the cHA column. The x-axis of Figure 4 depicts the order of eluates from the cHA column from left to right (i.e., from low salt to high salt; each data point indicates a fraction eluted from the column). The Y-axis in Figure 4 plots the percentages of: i) the intact anti-BCMA / CD3 bispecific antibody protein of interest ("POI"), ii) the trimmed form of the bispecific antibody, iii) the first parent antibody / monospecific anti-BCMA antibody, and iv) the second parent antibody / monospecific anti-CD3 antibody in each fraction. The Y-axis in Figure 4 plots the HMMS% in each fraction on the right. The method used to generate the data in Figure 3 was also used with an antibody preparation to which no additional antibody had been added; the data from this chromatographic run are shown in Figure 5. Thus, the data in Figure 5 reflect a typical antibody preparation eluted from an ion exchange column during the preparation of an anti-BCMA / CD3 bispecific antibody by purification on cHA resin, primarily containing the intact anti-BCMA / CD3 bispecific antibody of interest, as well as various impurities (including pruned forms of the bispecific antibody). In Figure 5, the X-axis plots the order of eluted material from the cHA column from left to right. The Y-axis plots UV absorbance (at 280 nM) and conductivity, as indicated separately in the figure. The Parent 1 and Parent 2 peaks are smaller in Figure 5 than in Figure 3 because, for Figure 5, the sample loaded onto the cHA column was not spiked with additional Parent 1 and Parent 2 antibodies (whereas for Figure 3, the sample was spiked with additional Parent 1 and Parent 2 antibodies). Figure 6 provides a graph showing additional information regarding the recovery of intact anti-BCMA / CD3 bispecific antibodies of interest from cHA resin and the relative amounts of trimmed bispecific antibodies in various eluted fractions from the cHA resin. The X-axis depicts the order of eluates from the cHA column from left to right (i.e., from low salt to high salt; each data point indicates a fraction eluted from the column). Along the vertical / Y-axis, three different variables are plotted for each fraction: Variable 1) (diamonds): Cumulative recovery of intact bispecific antibody ("POI %"), which is the total amount of intact anti-BCMA / CD3 bispecific antibody (i.e., protein of interest) recovered from the cHA column by that fraction during the chromatography run (in other words, it is as if all material eluting from the cHA column during the run and including that fraction were collected and pooled, and the total amount of intact anti-BCMA / CD3 bispecific antibody in the pooled material was then determined); in addition, the "POI %" value is expressed as a percentage of the total amount of intact anti-BCMA / CD3 bispecific antibody / protein of interest loaded onto the cHA column that was recovered (i.e., not expressed as a value in grams). Variable 2) (squares): The % of protein in each fraction that was a trimmed bispecific antibody ("Trimmed %"). Variable 3 (triangles): Cumulative recovery of the trimmed bispecific antibody ("Cumulative Trimmed"), which is the total amount of trimmed bispecific antibody recovered from the cHA column in this fraction during the chromatography run. Additionally, in the graph of Figure 6 , the left Y-axis lists POI% values, and the right Y-axis lists % Trimmed values. Figure 6 also includes information showing the extent to which certain fractions in Figure 6 correspond to different UV absorbance points in the chromatographic curve shown in Figure 5 . Thus, for example, Figure 5 shows that the largest peak of UV absorbance / protein elution from the cHA resin corresponds to the protein of interest / intact anti-BCMA / CD3 bispecific antibody. The top of this large peak of UV absorbance / protein elution from the cHA column is also referred to as the "apex" of the run; the chromatographic fraction peak corresponding to this apex is labeled in Figure 6 . Furthermore, various points following the apex peak are also labeled in Figure 6 . These points are "90%," "80%," "70%," "60%," and "50%," and can be calculated as follows. The UV absorbance value below the apex is used as the starting point for additional calculations. The UV value that is 90% of the apex UV value is then determined. The 90% apex UV value occurring after the apex UV value is achieved during the chromatography run (i.e., toward the tail of the peak) is recorded as the "90%" fraction; it may also be referred to herein as the "90% post-apex" fraction or similar terminology. This process is repeated to obtain 80%, 70%, 60%, and 50% values ​​(i.e., each of these values ​​is further down from the tail of the peak and therefore represents an increasingly larger amount of collected material). As shown in Figure 6, as the % apex value decreases, the % trimmed in the fraction increases. This is consistent with the intact anti-BCMA / CD3 bispecific antibody eluting from the cHA column at a later time / under higher salt conditions than the trimmed bispecific antibody. Therefore, if more fractions with an apex peak are collected (i.e., to a lower % post-apex fraction), more trimmed bispecific antibody will also be collected due to the partial overlap between the elution profiles of the intact bispecific antibody and the trimmed bispecific antibody. The various values ​​from Figure 6 are also provided in Table 1 below. As shown in Table 1, according to the cHA purification method provided herein, for example, if 90% of the eluate after the peak apex from the cHA column is collected (i.e., by the POI% recovery of the "90% after the peak apex" fraction), 54% of the intact bispecific antibody / protein of interest loaded onto the cHA column is recovered, and the recovered protein pool contains 0% trimmed bispecific antibodies. In another example, if 50% of the eluate after the peak apex from the cHA column is collected (i.e., by the POI% recovery of the "50% after the peak apex" fraction), 74% of the intact bispecific antibody / protein of interest loaded onto the cHA column is recovered, and the recovered protein pool contains 0.2% trimmed bispecific antibodies. Therefore, as shown in Figure 6 and Table 1, robust purification of the intact bispecific antibody of interest from trimmed bispecific antibodies can be effectively achieved by cHA resin. Table 1 For the cHA chromatography results shown in Figures 3 to 6, cHA chromatography can be performed as follows. An antibody preparation containing the bispecific anti-BCMA / CD3 antibody of interest and various impurities is loaded onto a chromatography column containing a cHA resin. The cHA resin is type 1 cHA, 40 μm bead size (Bio-Rad). For the chromatography runs depicted in Figures 3 and 4, the protein density of the cHA resin loading sample onto the cHA resin is 30 g / L. For the chromatography runs depicted in Figures 5 and 6, the protein density of the cHA resin loading sample onto the cHA resin is 10 g / L. Prior to loading the sample onto the cHA resin, the resin is pre-equilibrated with 5 column volumes of equilibration buffer 1 and then pre-equilibrated with 5 column volumes of equilibration buffer 2. The compositions of the various buffers described in this method are listed in Table 2 below. An antibody preparation containing a partially purified bispecific anti-BCMA / CD3 antibody of interest was loaded onto a cHA resin column in a loading buffer containing approximately 50 mM Tris and 60 mM glycine (pH 7.5). After loading the antibody preparation onto the cHA resin column, the column was washed with 3 column volumes of wash buffer. The bispecific antibody of interest (i.e., intact bispecific antibody) was then eluted from the cHA resin using 20 column volumes of elution buffer, wherein the sodium phosphate concentration in the elution buffer was increased from 40 mM to 80 mM during the elution process. As shown in Figures 3 to 6, various impurities present in the antibody preparation along with the bispecific antibody of interest were also eluted from the cHA column using the elution buffer, but they were eluted at a completely different salt concentration than the intact anti-BCMA / CD3 bispecific antibody of interest, allowing the intact bispecific antibody to be effectively separated from various impurities (including trimmed forms of the intact bispecific antibody). After eluting the protein of interest from the cHA resin column with elution buffer according to the above protocol, the cHA resin can then be stripped with 5 column volumes of stripping buffer, followed by sanitization with 5 column volumes of sanitization buffer, and then 5 column volumes of storage buffer. For each of the above analytes in the different materials eluted from the cHA column, the types and amounts of different molecular species in each fraction / pool were determined by analytical cation exchange (CEX) analysis. Table 2 Examples 2 :Through cHA Resin chromatography ( Mass loading challenges ) Purified antibody -BCMA / anti- -CD3 Bispecific antibodies The objective of this example was to determine whether the bispecific antibody purification method described in Example 1 could be effectively used in conjunction with various cHA resin column mass loading challenges. For example, one particular objective was to determine whether greater than 50% of the input bispecific antibody could be consistently recovered for various mass loading challenges on a cHA resin column while recovering no more than 1% of the trimmed bispecific antibody as an impurity in the purified bispecific antibody product. Materials and Methods: The materials and methods used in this example were the same as in Example 1, except that the cHA resin was loaded with the antibody preparation samples to a protein density of 8 g / L, 10 g / L, or 12 g / L on the cHA resin (in different chromatography runs). Results: The results of these chromatography runs are summarized in Table 3 below. For all three chromatography runs, 90% of the material after the peak apex was collected (as described in Example 1) and analyzed. As shown in Table 3, for each of the 8 g / L, 10 g / L, and 12 g / L mass challenges, more than 50% of the loaded intact bispecific antibody was recovered as purified bispecific antibody, and the recovered purified bispecific antibody product contained less than 1% of the trimmed bispecific antibody as an impurity. Thus, these experiments demonstrate that intact bispecific antibodies of interest can be effectively separated from trimmed bispecific antibodies by cHA resin chromatography under various cHA resin mass loading challenges. Table 3 Examples 3 :Through cHA Resin chromatography ( different pH challenge ) Purified antibody -BCMA / anti- -CD3 Bispecific antibodies Target The purpose of this example was to determine whether the bispecific antibody purification method described in Example 1 could be effectively performed under different pH conditions. Materials and Methods: The materials and methods used in this example were the same as those in Example 1, except that the pH of the buffer used throughout the method was pH 7.0, pH 7.5, or pH 8.0 (in different chromatography runs). For these chromatography runs, the cHA resin was loaded with the antibody formulation sample to a protein density of 30 g / L on the cHA resin. Results: The results of these chromatography runs are summarized in Table 4 below. For all three chromatography runs, peak apex material was collected (as described in Example 1) and analyzed. As shown in Table 4, the intact bispecific antibody protein of interest was successfully recovered for each of the different pH conditions tested, with pH 7.5 yielding the highest recovery of the protein of interest. (For these chromatography runs, the amount of pruned bispecific antibody in the purified material was not separately determined.) Therefore, these experiments show that the intact bispecific antibodies of interest can be efficiently purified by cHA resin chromatography under different pH conditions. Table 4 Examples 4 :Through cHA Resin chromatography to purify the -FLT3 / anti- -CD3 Bispecific antibodies Objective: The objective of this example was to determine whether the bispecific antibody purification method described in Example 1 could be effectively performed using a different bispecific antibody than that used in Example 1, where it was also necessary to separate the intact bispecific antibody of interest from various impurities (including related trimmed bispecific antibodies of similar mass). In this example, the antibody of interest was a heterodimeric bispecific anti-FLT3 / anti-CD3 antibody. Materials and Methods: The heterodimeric bispecific anti-FLT3 / anti-CD3 antibody used in this example contained the same anti-CD3 heavy and light chains as in Example 1. The amino acid sequences of the polypeptides in the FLT3 arm of the bispecific antibody are shown in the following SEQ ID NOs: FLT3 heavy chain: SEQ ID NO: 10; FLT3 light chain: SEQ ID NO: 12. The trimmed version of the bispecific antibody in this example has trims in the same positions as the anti-CD3 heavy chain described in Example 1 . The materials and methods used in this example were the same as those in Example 1, except that, as described above, the antibody preparation sample comprised a bispecific anti-FLT3 / anti-CD3 antibody. The antibody preparation sample was loaded onto the cHA resin at a protein density of 10 g / L. Results: Figure 7 shows a graph providing information regarding the recovery of intact bispecific anti-FLT3 / CD3 antibodies of interest from the cHA resin, as well as the relative amounts of trimmed bispecific antibodies in various eluted fractions from the cHA resin. The X-axis depicts the order of eluates from the cHA column from left to right (i.e., from low salt to high salt; each data point indicates a fraction eluted from the column). Along the vertical / Y-axis, three different variables are plotted for each fraction: variable 1 (diamonds): POI%; variable 2 (squares): Trimmed%; and variable 3 (triangles), each of which was determined as described in Example 1 for Figure 6. Additionally, in the graph of Figure 7, the left Y-axis lists POI% values, and the right Y-axis lists Trimmed% values. Figure 7 also includes information showing the extent to which certain fractions in Figure 7 correspond to different UV absorbance points (not shown) in the corresponding chromatographic curves. The points labeled "Top," "85%," and "60%" were determined in the same manner as described for Figure 6. Various values ​​from Figure 7 are also provided below in Table 5. As shown in Table 5, the cHA resin purification methods provided herein allow, for example, the recovery of over 80% of the intact, two-chain, specific anti-FLT3 / CD3 antibody of interest, while having less than 1% of the trimmed bispecific antibody in the purified antibody product. Therefore, as shown in Figure 7 and Table 5, purification of intact bispecific anti-FLT3 / CD3 from trimmed bispecific antibodies can be efficiently achieved by cHA resin. Table 5 Although the disclosed teachings have been described with reference to various applications, methods, kits, and compositions, it should be understood that various changes and modifications may be made without departing from the teachings herein and the inventions claimed below. The foregoing examples are provided to better illustrate the disclosed teachings and are not intended to limit the scope of the teachings presented herein. Although the present teachings have been described based on these exemplary embodiments, those skilled in the art will readily appreciate that many variations and modifications of these exemplary embodiments are possible without undue experimentation. All such variations and modifications are within the scope of the present teachings. All references cited herein (including patents, patent applications, articles, textbooks, and the like), and the references cited therein, are hereby incorporated by reference in their entirety to the extent not already provided. In the event that one or more of the incorporated literature and similar materials differs from or contradicts this application (including but not limited to defined terms, term usage, described techniques, or the like), this application controls. The foregoing description and examples detail certain specific embodiments of the present invention and describe the best mode contemplated by the inventors. However, it should be understood that no matter how detailed the foregoing may appear in text, the invention can be implemented in many ways and should be construed in accordance with the appended claims and any equivalents thereof. It should be understood that when any embodiment is described herein with the phrase "comprising," other similar embodiments described with "consisting of" and / or "consisting essentially of" are also provided. Where aspects or embodiments of the invention are described in terms of Markush groups or other alternative groups, the invention includes not only the entire group listed as a whole, but also each individual member of the group and all possible subgroups of the main group, as well as the main group without one or more of the group members. The invention also contemplates the specific exclusion of one or more of any group members from the claimed invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention pertains. In the event of a conflict, the present specification, including definitions, will control. In this specification and the claims, the word "comprise" or variations such as "comprises" or "comprising" will be understood to mean including a stated integer or group of integers but not excluding any other integer or group of integers. Unless the context requires otherwise, singular terms shall include the plural and plural terms shall include the singular. Any examples following the term "e.g., for example" are not intended to be exhaustive or limiting. Unless the context clearly indicates otherwise, the term "or," when used in the context of a list of multiple options (e.g., "A, B, or C"), should be interpreted to include any one or more of those options. Exemplary methods and materials are described herein; however, methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention. These materials, methods, and examples are illustrative only and not intended to be limiting. FIG1 depicts an overview of methods for preparing bispecific antibodies that can be purified according to the methods provided herein. Figure 2 depicts an overview of exemplary i) intact bispecific antibodies (left panel) and ii) trimmed forms of bispecific antibodies (right panel), where the trimmed bispecific antibodies are impurities that may be present in antibody preparations along with the intact bispecific antibodies. FIG3 depicts a chromatogram showing the separation of the anti-BCMA / anti-CD3 bispecific antibody of interest (“POI”) from various impurities by elution from HA resin. 4 depicts a graph showing the relative amounts of different proteins, including the antibody of interest and various impurities, in different fractions eluted from the HA resin according to an HA chromatography run as depicted in the chromatogram of FIG. 3 . FIG5 depicts a chromatogram showing the separation of the anti-BCMA / anti-CD3 bispecific antibody of interest (“POI”) from various impurities by elution from HA resin. FIG6 depicts a graph showing the relative amounts of different kinds of proteins (including the antibody of interest and various impurities) in different fractions eluted from the HA resin according to an HA chromatography run as depicted in the chromatogram of FIG5 , wherein the anti-BCMA / anti-CD3 bispecific antibody of interest ("POI") is separated from a variety of different impurities by elution from the HA resin. 7 depicts a graph showing the relative amounts of different proteins, including the antibody of interest and various impurities, in different fractions eluted from an HA resin according to an HA chromatography run, wherein the anti-FLT3 / anti-CD3 bispecific antibody of interest is separated from a variety of different impurities by elution from the HA resin. <![CDATA[ <110> Pfizer Inc. <![CDATA[ <120> Antibody Purification]]> <![CDATA[ <140> TW 108106273]]> <![CDATA[ <141> February 25, 2019 <![CDATA[ <150> US 62 / 635,943 <![CDATA[ <151> February 27, 2018 <![CDATA[ <160> 12 ]]> <![CDATA[ <170> PatentIn version 3.5 <![CDATA[ <210> 1]]> <![CDATA[ <211> 121]]> <![CDATA[ <212> PRT]]> <![CDATA[<213> Artificial sequence]]> <![CDATA[<220>]]> <![CDATA[<223> Synthetic construct]]> <![CDATA[<400> 1]]> Glu Val Gln Leu Val Glu Ser Gly Gly Gly Leu Val Gln Pro Gly Gly 1 5 10 15 Ser Leu Arg Leu Ser Cys Ala Ala Ser Gly Phe Thr Phe Ser Asp Tyr 20 25 30 Tyr Met Thr Trp Val Arg Gln Ala Pro Gly Lys Gly Leu Glu Trp Val 35 40 45 Ala Phe Ile Arg Asn Arg Ala Arg Gly Tyr Thr Ser Asp His Asn Pro 50 55 60 Ser Val Lys Gly Arg Phe Thr Ile Ser Arg Asp Asn Ala Lys Asn Ser 65 70 75 80 Leu Tyr Leu Gln Met Asn Ser Leu Arg Ala Glu Asp Thr Ala Val Tyr 85 90 95 Tyr Cys Ala Arg Asp Arg Pro Ser Tyr Tyr Val Leu Asp Tyr Trp Gly 100 105 110 Gln Gly Thr Thr Val Thr Val Ser Ser 115 120 <![CDATA[<210> 2]]> <![CDATA[<211> 447]]> <![CDATA[<212> PRT]]> <![CDATA[<213> Artificial sequence]]> <![CDATA[<220>]]> <![CDATA[<223> Synthetic construct]]> <![CDATA[<400> 2]]> Glu Val Gln Leu Val Glu Ser Gly Gly Gly Leu Val Gln Pro Gly Gly 1 5 10 15 Ser Leu Arg Leu Ser Cys Ala Ala Ser Gly Phe Thr Phe Ser Asp Tyr 20 25 30 Tyr Met Thr Trp Val Arg Gln Ala Pro Gly Lys Gly Leu Glu Trp Val 35 40 45 Ala Phe Ile Arg Asn Arg Ala Arg Gly Tyr Thr Ser Asp His Asn Pro 50 55 60 Ser Val Lys Gly Arg Phe Thr Ile Ser Arg Asp Asn Ala Lys Asn Ser <![CDATA[ ]]> 65 70 75 80 Leu Tyr Leu Gln Met Asn Ser Leu Arg Ala Glu Asp Thr Ala Val Tyr 85 90 95 Tyr Cys Ala Arg Asp Arg Pro Ser Tyr Tyr Val Leu Asp Tyr Trp Gly 100 105 110 Gln Gly Thr Thr Val Thr Val Ser Ser Ala Ser Thr Lys Gly Pro Ser 115 120 125 Val Phe Pro Leu Ala Pro Cys Ser Arg Ser Thr Ser Glu Ser Thr Ala 130 135 140 Ala Leu Gly Cys Leu Val Lys Asp Tyr Phe Pro Glu Pro Val Thr Val 145 150 155 160 Ser Trp Asn Ser Gly Ala Leu Thr Ser Gly Val His Thr Phe Pro Ala 165 170 175 Val Leu Gln Ser Ser Gly Leu Tyr Ser Leu Ser Ser Val Val Thr Val 180 185 190 Pro Ser Ser Asn Phe Gly Thr Gln Thr Tyr Thr Cys Asn Val Asp His 195 200 205 Lys Pro Ser Asn Thr Lys Val Asp Lys Thr Val Glu Arg Lys Cys Arg 210 215 220 Val Arg Cys Pro Arg Cys Pro Ala Pro Pro Val Ala Gly Pro Ser Val 225 230 235 240 Phe Leu Phe Pro Pro Lys Pro Lys Asp Thr Leu Met Ile Ser Arg Thr 245 250 255 Pro Glu Val Thr Cys Val Val Val Ala Val Ser His Glu Asp Pro Glu 260 265 270 Val Gln Phe Asn Trp Tyr Val Asp Gly Val Glu Val His Asn Ala Lys 275 280 285 Thr Lys Pro Arg Glu Glu Gln Phe Asn Ser Thr Phe Arg Val Val Ser 290 295 300 Val Leu Thr Val Val His Gln Asp Trp Leu Asn Gly Lys Glu Tyr Lys 305 310 315 320 Cys Lys Val Ser Asn Lys Gly Leu Pro Ser Ser Ile Glu Lys Thr Ile 325 330 335 Ser Lys Thr Lys Gly Gln Pro Arg Glu Pro Gln Val Tyr Thr Leu Pro 340 345 350 Pro Ser Arg Glu Glu Met Thr Lys Asn Gln Val Ser Leu Thr Cys Leu 355 360 365 Val Lys Gly Phe Tyr Pro Ser Asp Ile Ala Val Glu Trp Glu Ser Asn 370 375 380 Gly Gln Pro Glu Asn Asn Tyr Lys Thr Thr Pro Pro Met Leu Asp Ser 385 390 395 400 Asp Gly Ser Phe Phe Leu Tyr Ser Arg Leu Thr Val Asp Lys Ser Arg 405 410 415 Trp Gln Gln Gly Asn Val Phe Ser Cys Ser Val Met His Glu Ala Leu 420 425 430 His Asn His Tyr Thr Gln Lys Ser Leu Ser Leu Ser Pro Gly Lys 435 440 445 <![CDATA[<210> 3]]> <![CDATA[<211> 112]]> <![CDATA[<212> PRT]]> <![CDATA[<213> Artificial Sequence]]> <![CDATA[<220="">]]> <![CDATA[<223> Synthetic Construct]]> <![CDATA[<400> 3]]> Asp Ile Val Met Thr Gln Ser Pro Asp Ser Leu Ala Val Ser Leu Gly 1 5 10 15 Glu Arg Ala Thr Ile Asn Cys Lys Ser Ser Gln Ser Leu Phe Asn Val 20 25 30 Arg Ser Arg Lys Asn Tyr Leu Ala Trp Tyr Gln Gln Lys Pro Gly Gln 35 40 45 Pro Pro Lys Leu Leu Ile Ser Trp Ala Ser Thr Arg Glu Ser Gly Val 50 55 60 Pro Asp Arg Phe Ser Gly Ser Gly Ser Gly Thr Asp Phe Thr Leu Thr 65 70 75 80 Ile Ser Ser Leu Gln Ala Glu Asp Val Ala Val Tyr Tyr Cys Lys Gln 85 90 95 Ser Tyr Asp Leu Phe Thr Phe Gly Ser Gly Thr Lys Leu Glu Ile Lys 100 105 110 <![CDATA[<210> 4]]> <![CDATA[<211> 219]]> <![CDATA[<212> PRT]]> <![CDATA[<213> Artificial Sequence]]> <![CDATA[<220>]]> <![CDATA[<223> Synthetic Construct]]> <![CDATA[<400> 4]]> Asp Ile Val Met Thr Gln Ser Pro Asp Ser Leu Ala Val Ser Leu Gly 1 5 10 15 Glu Arg Ala Thr Ile Asn Cys Lys Ser Ser Gln Ser Leu Phe Asn Val 20 25 30 Arg Ser Arg Lys Asn Tyr Leu Ala Trp Tyr Gln Gln Lys Pro Gly Gln 35 40 45 Pro Pro Lys Leu Leu Ile Ser Trp Ala Ser Thr Arg Glu Ser Gly Val 50 55 60 Pro Asp Arg Phe Ser Gly Ser Gly Ser Gly Thr Asp Phe Thr Leu Thr 65 70 75 80 Ile Ser Ser Leu Gln Ala Glu Asp Val Ala Val Tyr Tyr Cys Lys Gln 85 90 95 Ser Tyr Asp Leu Phe Thr Phe Gly Ser Gly Thr Lys Leu Glu Ile Lys 100 105 110 Arg Thr Val Ala Ala Pro Ser Val Phe Ile Phe Pro Pro Ser Asp Glu 115 120 125 Gln Leu Lys Ser Gly Thr Ala Ser Val Val Cys Leu Leu Asn Asn Phe 130 135 140 Tyr Pro Arg Glu Ala Lys Val Gln Trp Lys Val Asp Asn Ala Leu Gln 145 150 155 160 Ser Gly Asn Ser Gln Glu Ser Val Thr Glu Gln Asp Ser Lys Asp Ser 165 170 175 Thr Tyr Ser Leu Ser Ser Thr Leu Thr Leu Ser Lys Ala Asp Tyr Glu 180 185 190 Lys His Lys Val Tyr Ala Cys Glu Val Thr His Gln Gly Leu Ser Ser 195 200 205 Pro Val Thr Lys Ser Phe Asn Arg Gly Glu Cys 210 215 <![CDATA[<210> 5]]> <![CDATA[<211> 115]]> <![CDATA[<212> PRT]]> <![CDATA[<213> Artificial sequence]]> <![CDATA[<220>]]> <![CDATA[<223> Synthetic construct]]> <![CDATA[<400> 5]]> Glu Val Gln Leu Leu Glu Ser Gly Gly Gly Leu Val Gln Pro Gly Gly 1 5 10 15 Ser Leu Arg Leu Ser Cys Ala Ala Ser Gly Phe Thr Phe Ser Ser Tyr 20 25 30 Pro Met Ser Trp Val Arg Gln Ala Pro Gly Lys Gly Leu Glu Trp Val 35 40 45 Ser Ala Ile Gly Gly Ser Gly Gly Ser Leu Pro Tyr Ala Asp Ile Val 50 55 60 Lys Gly Arg Phe Thr Ile Ser Arg Asp Asn Ser Lys Asn Thr Leu Tyr 65 70 75 80 Leu Gln Met Asn Ser Leu Arg Ala Glu Asp Thr Ala Val Tyr Tyr Cys 85 90 95 <s Ala Arg Tyr Trp Pro Met Asp Ile Trp Gly Gln Gly Thr Leu Val Thr 100 105 110 Val Ser Ser 115 <![CDATA[<210> 6]]> <![CDATA[<211> 441]]> <![CDATA[<212> PRT]]> <![CDATA[<213> Artificial Sequence]]> <![CDATA[<220>]]> <![CDATA[<223> Synthetic Construct]]> <![CDATA[<400> 6]]> Glu Val Gln Leu Leu Glu Ser Gly Gly Gly Leu Val Gln Pro Gly Gly 1 5 10 15 Ser Leu Arg Leu Ser Cys Ala Ala Ser Gly Phe Thr Phe Ser Ser Tyr 20 25 30 Pro Met Ser Trp Val Arg Gln Ala Pro Gly Lys Gly Leu Glu Trp Val 35 40 45 Ser Ala Ile Gly Gly Ser Gly Gly Ser Leu Pro Tyr Ala Asp Ile Val 50 55 60 Lys Gly Arg Phe Thr Ile Ser Arg Asp Asn Ser Lys Asn Thr Leu Tyr 65 70 75 80 Leu Gln Met Asn Ser Leu Arg Ala Glu Asp Thr Ala Val Tyr Tyr Cys 85 90 95 Ala Arg Tyr Trp Pro Met Asp Ile Trp Gly Gln Gly Thr Leu Val Thr 100 105 110 Val Ser Ser Ala Ser Thr Lys Gly Pro Ser Val Phe Pro Leu Ala Pro [[ID=?]] 115 120 125 Cys Ser Arg Ser Thr Ser Glu Ser Thr Ala Ala Leu Gly Cys Leu Val 130 135 140 Lys Asp Tyr Phe Pro Glu Pro Val Thr Val Ser Trp Asn Ser Gly Ala 145 150 155 160 Leu Thr Ser Gly Val His Thr Phe Pro Ala Val Leu Gln Ser Ser Gly 165 170 175 Leu Tyr Ser Leu Ser Ser Val Val Thr Val Pro Ser Ser Asn Phe Gly 180 185 190 Thr Gln Thr Tyr Thr Cys Asn Val Asp His Lys Pro Ser Asn Thr Lys 195 200 205 Val Asp Lys Thr Val Glu Arg Lys Cys Glu Val Glu Cys Pro Glu Cys 210 215 220 Pro Ala Pro Pro Val Ala Gly Pro Ser Val Phe Leu Phe Pro Pro Lys 225 230 235 240 Pro Lys Asp Thr Leu Met Ile Ser Arg Thr Pro Glu Val Thr Cys Val 245 250 255 Val Val Ala Val Ser His Glu Asp Pro Glu Val Gln Phe Asn Trp Tyr 260 265 270 Val Asp Gly Val Glu Val His Asn Ala Lys Thr Lys Pro Arg Glu Glu 275 280 285 Gln Phe Asn Ser Thr Phe Arg Val Val Ser Val Leu Thr Val Val His 290 295 300 Gln Asp Trp Leu Asn Gly Lys Glu Tyr Lys Cys Lys Val Ser Asn Lys 305 310 315 320 Gly Leu Pro Ser Ser Ile Glu Lys Thr Ile Ser Lys Thr Lys Gly Gln 325 330 335 Pro Arg Glu Pro Gln Val Tyr Thr Leu Pro Pro Ser Arg Glu Glu Met 340 345 350 Thr Lys Asn Gln Val Ser Leu Thr Cys Glu Val Lys Gly Phe Tyr Pro 355 360 365 Ser Asp Ile Ala Val Glu Trp Glu Ser Asn Gly Gln Pro Glu Asn Asn 370 375 380 Tyr Lys Thr Thr Pro Pro Met Leu Asp Ser Asp Gly Ser Phe Phe Leu 385 390 395 400 Tyr Ser Lys Leu Thr Val Asp Lys Ser Arg Trp Gln Gln Gly Asn Val 405 410 415 Phe Ser Cys Ser Val Met His Glu Ala Leu His Asn His Tyr Thr Gln 420 425 430 Lys Ser Leu Ser Leu Ser Pro Gly Lys 435 440 <![CDATA[<210> 7]]> <![CDATA[<211> 108]]> <![CDATA[<212> PRT]]> <![CDATA[<213> Artificial Sequence]]> <![CDATA[<220>]]> <![CDATA[<223> Synthetic Construct]]> <![CDATA[<400> 7]]> Glu Ile Val Leu Thr Gln Ser Pro Gly Thr Leu Ser Leu Ser Pro Gly 1 5 10 15 Glu Arg Ala Thr Leu Ser Cys Arg Ala Ser Gln Ser Val Ser Ser Ser 20 25 30 Tyr Leu Ala Trp Tyr Gln Gln Lys Pro Gly Gln Ala Pro Arg Leu Leu 35 40 45 Met Tyr Asp Ala Ser Ile Arg Ala Thr Gly Ile Pro Asp Arg Phe Ser 50 55 60 Gly Ser Gly Ser Gly Thr Asp Phe Thr Leu Thr Ile Ser Arg Leu Glu 65 70 75 80 Pro Glu Asp Phe Ala Val Tyr Tyr Cys Gln Gln Tyr Gln Ser Trp Pro 85 90 95 Leu Thr Phe Gly Gln Gly Thr Lys Val Glu Ile Lys 100 105 <![CDATA[<210> 8]]> <![CDATA[<211> 215]]> <![CDATA[<212> PRT]]> <![CDATA[<213> Artificial sequence]]> <![CDATA[<220>]]> <![CDATA[<223> Synthetic construct]]> <![CDATA[<400> 8]]> Glu Ile Val Leu Thr Gln Ser Pro Gly Thr Leu Ser Leu Ser Pro Gly 1 5 10 15 Glu Arg Ala Thr Leu Ser Cys Arg Ala Ser Gln Ser Val Ser Ser Ser 20 25 30 Tyr Leu Ala Trp Tyr Gln Gln Lys Pro Gly Gln Ala Pro Arg Leu Leu 35 40 45 Met Tyr Asp Ala Ser Ile Arg Ala Thr Gly Ile Pro Asp Arg Phe Ser 50 55 60 Gly Ser Gly Ser Gly Thr Asp Phe Thr Leu Thr Ile Ser Arg Leu Glu 65 70 75 80 Pro Glu Asp Phe Ala Val Tyr Tyr Cys Gln Gln Tyr Gln Ser Trp Pro 85 90 95 Leu Thr Phe Gly Gln Gly Thr Lys Val Glu Ile Lys Arg Thr Val Ala 100 105 110 Ala Pro Ser Val Phe Ile Phe Pro Pro Ser Asp Glu Gln Leu Lys Ser 115 120 125 Gly Thr Ala Ser Val Val Cys Leu Leu Asn Asn Phe Tyr Pro Arg Glu 130 135 140 Ala Lys Val Gln Trp Lys Val Asp Asn Ala Leu Gln Ser Gly Asn Ser 145 150 155 160 Gln Glu Ser Val Thr Glu Gln Asp Ser Lys Asp Ser Thr Tyr Ser Leu 165 170 175 Ser Ser Thr Leu Thr Leu Ser Lys Ala Asp Tyr Glu Lys His Lys Val 180 185 190 Tyr Ala Cys Glu Val Thr His Gln Gly Leu Ser Ser Pro Val Thr Lys 195 200 205 Ser Phe Asn Arg Gly Glu Cys 210 215 <![CDATA[<210> 9]]> <![CDATA[<211> 124]]> <![CDATA[<212> PRT]]> <![CDATA[<213> Artificial Sequence]]> <![CDATA[<220>]]> <![CDATA[<223> Synthetic Construct]]> <![CDATA[<400> 9]]> Glu Val Gln Leu Leu Glu Ser Gly Gly Gly Leu Val Gln Pro Gly Gly 1 5 10 15 Ser Leu Arg Leu Ser Cys Ala Ala Ser Gly Phe Thr Phe Ser Ser Tyr 20 25 30 Ala Met Asn Trp Val Arg Gln Ala Pro Gly Lys Gly Leu Glu Trp Val 35 40 45 Ser Ala Ile Ser Gly Gly Gly Arg Ser Thr Tyr Tyr Ala Asp Ser Val 50 55 60 Lys Gly Arg Phe Thr Ile Ser Arg Asp Asn Ser Lys Asn Thr Leu Tyr 65 70 75 80 Leu Gln Met Asn Ser Leu Arg Ala Glu Asp Thr Ala Val Tyr Tyr Cys 85 90 95 Ala Arg Asp Leu Ser Pro Ser Asp Val Gly Trp Gly Tyr Gly Phe Asp 100 105 110 Ile Trp Gly Gln Gly Thr Leu Val Thr Val Ser Ser 115 120 <![CDATA[<210> 10]]> <![CDATA[<211> 449]]> <![CDATA[<212> PRT]]> <![CDATA[<213> Synthetic Sequence]]> <![CDATA[<220>]]> <![CDATA[<223> Synthetic construct]]> <![CDATA[<400> 10]]> Glu Val Gln Leu Leu Glu Ser Gly Gly Gly Leu Val Gln Pro Gly Gly 1 5 10 15 Ser Leu Arg Leu Ser Cys Ala Ala Ser Gly Phe Thr Phe Ser Ser Tyr 20 25 30 Ala Met Asn Trp Val Arg Gln Ala Pro Gly Lys Gly Leu Glu Trp Val 35 40 45 Ser Ala Ile Ser Gly Gly Gly Arg Ser Thr Tyr Tyr Ala Asp Ser Val 50 55 60 Lys Gly Arg Phe Thr Ile Ser Arg Asp Asn Ser Lys Asn Thr Leu Tyr 65 70 75 80 Leu Gln Met Asn Ser Leu Arg Ala Glu Asp Thr Ala Val Tyr Tyr Cys 85 90 95 Ala Arg Asp Leu Ser Pro Ser Asp Val Gly Trp Gly Tyr Gly Phe Asp 100 105 110 Ile Trp Gly Gln Gly Thr Leu Val Thr Val Ser Ser Ala Ser Thr Lys 115 120 125 Gly Pro Ser Val Phe Pro Leu Ala Pro Cys Ser Arg Ser Thr Ser Glu 130 135 140 Ser Thr Ala Ala Leu Gly Cys Leu Val Lys Asp Tyr Phe Pro Glu Pro 145 150 155 160 Val Thr Val Ser Trp Asn Ser Gly Ala Leu Thr Ser Gly Val His Thr 165 170 175 Phe Pro Ala Val Leu Gln Ser Ser Gly Leu Tyr Ser Leu Ser Ser Val 180 185 190 Val Thr Val Pro Ser Ser Asn Phe Gly Thr Gln Thr Tyr Thr Cys Asn 195 200 205 Val Asp His Lys Pro Ser Asn Thr Lys Val Asp Lys Thr Val Glu Arg 210 215 220 Lys Cys Glu Val Glu Cys Pro Glu Cys Pro Ala Pro Pro Val Ala Gly 225 230 235 240 Pro Ser Val Phe Leu Phe Pro Pro Lys Pro Lys Asp Thr Leu Met Ile 245 250 255 Ser Arg Thr Pro Glu Val Thr Cys Val Val Val Ala Val Ser His Glu 260 265 270 Asp Pro Glu Val Gln Phe Asn Trp Tyr Val Asp Gly Val Glu Val His 275 280 285 Asn Ala Lys Thr Lys Pro Arg Glu Glu Gln Phe Asn Ser Thr Phe Arg 290 295 300 Val Val Ser Val Leu Thr Val Val His Gln Asp Trp Leu Asn Gly Lys 305 310 315 320 Glu Tyr Lys Cys Lys Val Ser Asn Lys Gly Leu Pro Ser Ser Ile Glu 325 330 335 Lys Thr Ile Ser Lys Thr Lys Gly Gln Pro Arg Glu Pro Gln Val Tyr 340 345 350 Thr Leu Pro Pro Ser Arg Glu Glu Met Thr Lys Asn Gln Val Ser Leu 355 360 365 Thr Cys Glu Val Lys Gly Phe Tyr Pro Ser Asp Ile Ala Val Glu Trp 370 375 380 Glu Ser Asn Gly Gln Pro Glu Asn Asn Tyr Lys Thr Thr Pro Pro Met 385 390 395 400 Leu Asp Ser Asp Gly Ser Phe Phe Leu Tyr Ser Lys Leu Thr Val Asp 405 410 415 Lys Ser Arg Trp Gln Gln Gly Asn Val Phe Ser Cys Ser Val Met His 420 425 430 Glu Ala Leu His Asn His Tyr Thr Gln Lys Ser Leu Ser Leu Ser Pro 435 440 445 Gly <![CDATA[ <210> 11]]> <![CDATA[ <211> 107]]> <![CDATA[ <212> PRT]]> <![CDATA[ <213> artificial sequence]]> <![CDATA[ <220> ]]> <![CDATA[ <223> Synthesize structure]]> <![CDATA[ <400> 11]]> Glu Ile Val Leu Thr Gln Ser Pro Ala Thr Leu Ser Leu Ser Pro Gly 1 5 10 15 Glu Arg Ala Thr Leu Ser Cys Arg Ala Ser Gln Ser Val Ser Ser Asn 20 25 30 Leu Ala Trp Tyr Gln Gln Lys Pro Gly Gln Ala Pro Arg Leu Leu Ile 35 40 45 Tyr Asp Thr Phe Thr Arg Ala Thr Gly Ile Pro Ala Arg Phe Ser Gly 50 55 60 Ser Gly Ser Gly Thr Asp Phe Thr Leu Thr Ile Ser Ser Leu Glu Pro 65 70 75 80 Glu Asp Phe Ala Val Tyr Tyr Cys Gln Gln Tyr Gly Ser Ser Pro Pro 85 90 95 Thr Phe Gly Gln Gly Thr Arg Leu Glu Ile Lys 100 105 <![CDATA[<210> 12]]> <![CDATA[<211> 214]]> <![CDATA[<212> PRT]]> <![CDATA[<213> Artificial sequence]]> <![CDATA[<220>]]> <![CDATA[<223> Synthetic construct]]> <![CDATA[<400> 12]]> Glu Ile Val Leu Thr Gln Ser Pro Ala Thr Leu Ser Leu Ser Pro Gly 1 5 10 15 Glu Arg Ala Thr Leu Ser Cys Arg Ala Ser Gln Ser Val Ser Ser Asn 20 25 30 Leu Ala Trp Tyr Gln Gln Lys Pro Gly Gln Ala Pro Arg Leu Leu Ile 35 40 45 Tyr Asp Thr Phe Thr Arg Ala Thr Gly Ile Pro Ala Arg Phe Ser Gly 50 55 60 Ser Gly Ser Gly Thr Asp Phe Thr Leu Thr Ile Ser Ser Leu Glu Pro 65 70 75 80 Glu Asp Phe Ala Val Tyr Tyr Cys Gln Gln Tyr Gly Ser Ser Pro Pro 85 90 95 Thr Phe Gly Gln Gly Thr Arg Leu Glu Ile Lys Arg Thr Val Ala Ala 100 105 110 Pro Ser Val Phe Ile Phe Pro Pro Ser Asp Glu Gln Leu Lys Ser Gly 115 120 125 Thr Ala Ser Val Val Cys Leu Leu Asn Asn Phe Tyr Pro Arg Glu Ala 130 135 140 Lys Val Gln Trp Lys Val Asp Asn Ala Leu Gln Ser Gly Asn Ser Gln 145 150 155 160 Glu Ser Val Thr Glu Gln Asp Ser Lys Asp Ser Thr Tyr Ser Leu Ser 165 170 175 Ser Thr Leu Thr Leu Ser Lys Ala Asp Tyr Glu Lys His Lys Val Tyr 180 185 190 Ala Cys Glu Val Thr His Gln Gly Leu Ser Ser Pro Val Thr Lys Ser 195 200 205 Phe Asn Arg Gly Glu Cys 210

Claims

1. A composition comprising a complete anti-BCMA / anti-CD3 bispecific antibody and a trimmed form of the bispecific antibody, wherein a) the bispecific antibody comprises an anti-BCMA arm and an anti-CD3 arm, the anti-CD3 arm comprising a VH region comprising an amino acid sequence as shown in SEQ ID NO: 1 and a VL region comprising an amino acid sequence as shown in SEQ ID NO: 3, and the anti-BCMA arm comprising a VH region comprising an amino acid sequence as shown in SEQ ID NO: 5 and a VL region comprising an amino acid sequence as shown in SEQ ID NO: 7; b) the trimmed form of the bispecific antibody has a molecular weight difference of less than 1% from the complete bispecific antibody; and the composition comprises at least 90% by mass of the complete bispecific antibody of the protein in the composition, and 0.1% to 8% by mass of the trimmed version of the bispecific antibody of the protein in the composition; In the trimmed form of this bispecific antibody, except that the peptide bond between N-terminal amino acid residues 56 and 57 in the VH region of the anti-CD3 arm of the trimmed bispecific antibody is cleaved, the trimmed bispecific antibody has the same amino acid sequence as the intact bispecific antibody, and the trimmed 56 amino acid portions of the VH region of the anti-CD3 arm of the trimmed bispecific antibody are held together by disulfide bonds to bind to the rest of the trimmed bispecific antibody.

2. The composition of claim 1, wherein the trimmed form of the bispecific antibody has a molecular weight greater than 18 Daltons of the intact bispecific antibody.

3. The composition of claim 1 or 2, wherein the composition comprises at least 90% by mass of an intact bispecific antibody of the protein in the composition, and 0.1% to 5% by mass of a cleaved version of the bispecific antibody of the protein in the composition.

4. The composition of claim 1 or 2, wherein the composition comprises at least 90% by mass of an intact bispecific antibody of the protein in the composition, and 0.1% to 3% by mass of a cleaved version of the bispecific antibody of the protein in the composition.

5. The composition of claim 1 or 2, wherein the anti-CD3 arm comprises a heavy chain comprising an amino acid sequence as shown in SEQ ID NO: 2 and a light chain comprising an amino acid sequence as shown in SEQ ID NO: 4, and the anti-BCMA arm comprises a heavy chain comprising an amino acid sequence as shown in SEQ ID NO: 6 and a light chain comprising an amino acid sequence as shown in SEQ ID NO: 8.

Images