RAPID CLEARANCE OF ANTIGEN COMPLEXES USING NOVEL ANTIBODIES

[0001] This application claims priority to U.S. Provisional Application Ser. No. 62/028,695, filed Jul. 24, 2014, which is expressly incorporated by reference in the entirety.

[0002] U.S. Ser. Nos. 11/124,620, 13/294,103, 12/341,769 and 12/156,183 are all expressly incorporated by reference in their entirety, particularly for the recitation of amino acid positions and substitutions, and all data, figures and legends relating thereto.

[0003] The present disclosure relates to methods of using polypeptides with two domains, a first domain that bind a ligand (such as the variable region of an immunoglobulin or a fusion partner) and a second domain, an Fc domain, that binds FcγRIIb, particularly human FcγRIIb, with high affinity. These methods resulting in rapid and accelerated clearance of the polypeptide-ligand complexes, e.g. the antibody-antigen complexes in the case of antibody polypeptides. Such methods are useful for treating a variety of conditions.

[0004] Antigen recognition by B cells is mediated by the B cell receptor (BCR), a surface-bound immunoglobulin in complex with signaling components CD79a (Igα) and CD79b (Igβ). Crosslinking of BCR upon engagement of antigen results in phosphorylation of immunoreceptor tyrosine-based activation motifs (ITAMs) within CD79a and CD79b, initiating a cascade of intracellular signaling events that recruit downstream molecules to the membrane and stimulate calcium mobilization. This leads to the induction of diverse B cell responses (e.g., cell survival, proliferation, antibody production, antigen presentation, differentiation, etc.) which lead to a humoral immune response (DeFranco, A. L., 1997, Curr. Opin. Immunol. 9, 296-308; Pierce, S. K., 2002, Nat. Rev. Immunol. 2, 96-105; Ravetch, J. V. & Lanier, L. L., 2000, Science 290, 84-89). Other components of the BCR coreceptor complex enhance (e.g., CD19, CD21, and CD81) or suppress (e.g., CD22 and CD72) BCR activation signals (Doody, G. M. et al., 1996, Curr. Opin. Immunol. 8, 378-382; L1, D. H. et al., 2006, J. Immunol. 176, 5321-5328). In this way, the immune system maintains multiple BCR regulatory mechanisms to ensure that B cell responses are tightly controlled.

[0005] When antibodies are produced to an antigen, the circulating level of immune complexes (e.g., antigen bound to antibody) increases. These immune complexes downregulate antigen-induced B cell activation. It is believed that these immune complexes downregulate antigen-induced B cell activation by coengaging cognate BCR with the low-affinity inhibitory receptor FcγRIIb, the only IgG receptor on B cells (Heyman, B., 2003, Immunol. Lett. 88, 157-161). It is also believed that this negative feedback of antibody production requires interaction of the antibody Fc domain with FcγRIIb since immune complexes containing F(ab′)₂ antibody fragments are not inhibitory (Chan, P. L. & Sinclair, N. R., 1973, Immunology 24, 289-301). The intracellular immunoreceptor tyrosine-based inhibitory motif (ITIM) of FcγRIIb is necessary to inhibit BCR-induced intracellular signals (Amigorena, S. et al., 1992, Science 256, 1808-1812; Muta, T., et al., 1994, Nature 368, 70-73). This inhibitory effect occurs through phosphorylation of the FcγRIIb ITIM, which recruits SH2-containing inositol polyphosphate 5-phosphatase (SHIP) to neutralize ITAM-induced intracellular calcium mobilization (Kiener, P. A., et al., 1997, J. Biol. Chem. 272, 3838-3844; Ono, M., et al., 1996, Nature 383, 263-266; Ravetch, J. V. & Lanier, L. L., 2000, Science 290, 84-89). In addition, FcγRIIb-mediated SHIP phosphorylation inhibits the downstream Ras-MAPK proliferation pathway (Tridandapani, S. et al., 1998, Immunol. 35, 1135-1146).

[0006] A recently recognized function of FcγRIIb is to serve as a scavenger receptor in the liver, clearing antibody:antigen immune complexes from circulation. FcγRIIb is thus an important component of the classical reticulo-endothelial system. For example, Anderson and colleagues (Ganesan et al., J Immunol 2012) published a study demonstrating that three quarters of mouse FcγRIIb is expressed in the liver, with 90% of it being expressed in Liver Sinusoidal Endothelial Cells (LSEC). Moreover, the authors demonstrated that clearance of radiolabeled small immune complexes (SIC) is significantly impaired in an FcγRIIb knockout strain compared to wild-type mice. This is therefore a natural property of the immune system, which can be accentuated by Fc engineering for enhanced affinity to FcγRIIb.

[0007] Of relevance in the present invention are allergic diseases. Allergic diseases and conditions, such as asthma, allergic rhinitis, atopic dermatitis, and food allergy, have become increasingly prevalent over the past few decades and now affect 10-40% of the population in industrialized countries. Allergic diseases profoundly affect the quality of life, and can result in serious complications, including death, as may occur in serious cases of asthma and anaphylaxis. Allergies are prevalent, and are the largest cause of time lost from work and school and their impact on personal lives as well as their direct and indirect costs to the medical systems and economy are enormous. For example, allergic rhinitis (hay fever) affects 22% or more of the population of the USA, whereas allergic asthma is thought to affect at least 20 million residents of the USA. The economic impact of allergic diseases in the United States, including health care costs and lost productivity, has been estimated to amount to $6.4 billion in the early nineties alone.

[0008] Most allergic diseases are caused by immunoglobulin E (IgE)-mediated hypersensitivity reactions. IgE is a class of antibody normally present in the serum at minute concentrations. It is produced by IgE-secreting plasma cells that express the antibody on their surface at a certain stage of their maturation. Allergic patients produce elevated levels of IgE with binding specificity for ordinarily innocuous antigens to which they are sensitive. These IgE molecules circulate in the blood and bind to IgE-specific receptors on the surface of basophils in the circulation and mast cells along mucosal linings and underneath the skin. Binding of antigen or allergen to IgE on mast cells, basophils, and other cell types, crosslink the IgE molecules, and aggregate the underlying receptors, thus triggering the cells to release vasoactive and neuronal stimulatory mediators such as histamines, leukotrienes, prostaglandins, bradykinin, and platelet-activating factor. The rapid reaction of the immune system to antigen caused by antibody immune complexes has led to the term immediate or antibody-mediated hypersensitivity reaction, in contrast to delayed or cell-mediated hypersensitivity reactions that are mediated by T cells. IgE-mediated immune reactions are specifically referred to as type I hypersensitivity reactions.

[0009] The high affinity receptor for IgE (FcεRI) is a key mediator for immediate allergic manifestations. In addition to mast cells and basophils, the primary mediators of allergic reactions, FcεRI is found on a number of other cell types including eosinophils, platelets and on antigen-presenting cells such as monocytes and dendritic cells. An additional receptor for IgE is FcεRII, also known as CD23 or the low-affinity IgE Fc receptor. FcεRII is expressed broadly on B lymphocytes, macrophages, platelets, and many other cell types such as airway smooth muscle. FcεRII may play a role in the feedback regulation of IgE expression and subsequently FcεRII surface expression.

[0010] Since IgE plays a central role in mediating most allergic reactions, devising treatments to control IgE levels in the body and regulating IgE synthesis has been of great interest. Several strategies have been proposed to treat IgE-mediated allergic diseases by downregulating IgE levels. One strategy involves neutralizing the IgE molecules by binding the &chain of IgE in or near the Fc-receptor binding site. For example, Omalizumab (Xolair) is a recombinant humanized monoclonal anti-IgE antibody that binds to IgE on the same Fc site as FcεRI. Omalizumab causes a reduction in total serum or circulating IgE in atopic patients, which attenuates the amount of antigen-specific IgE that can bind to and sensitize tissue mast cells and basophils. This, in turn, leads to a decrease in symptoms of allergic diseases. Interestingly, serum IgE levels increase after start of therapy because of omalizumab-IgE complex formation and may remain high up to a year after stopping therapy. Consequently, this issue may lead to false-negatives on diagnostic tests and therefore IgE levels must be routinely checked. Accordingly, there exists a need for improved methods and compositions to reduce IgE-mediated diseases and disease symptoms.

[0011] Of additional relevance in the present invention is the fact that antibody/antigen immune complexes are well established mediators of inflammation in various autoimmune diseases. Moreover, circulating immune complexes can be deposited in the kidney, ultimately resulting in nephritis, the leading cause of death in systemic lupus erythematosus (SLE). Finally, nucleic-acid (RNA or DNA) containing immune complexes, observed most notably in SLE, can interact with toll-like receptors (TLRs) on immune cells, inducing the release of inflammatory cytokines such as interferon alpha, contributing to disease pathogenesis. The complement system naturally recognizes these antibody-antigen immune complexes (ICs), resulting in complement-component C3 ‘tagging’ of the immune complexes with a variety of fragments of C3 (including C3b, C3b(i), C3d, and C3g). Under healthy conditions, these tagged immune complexes are cleared through interaction with a variety of complement receptors and FcγRs. C3b-C3b-IgG covalent complexes are immediately formed on interaction of serum C3 with IgG-IC. These C3b-C3b dimers constitute the core for the assembly of C3/C5-convertase on the IC, which are subsequently converted into iC3b-iC3b-IgG by the complement regulators. Further processing of iC3b can occur through interaction with these regulators, to produce C3d and C3g. ICs tagged with various forms of C3 have been detected in a variety of autoimmune disease, and C3d-IC levels in particular have been shown to correlate directly with disease activity level in SLE. See Toong C, Adelstein S, Phan T G (2011) Int J Nephrol Renovasc Dis “Clearing the complexity: immune complexes and their treatment in lupus nephritis,” 4:17-28, which is hereby incorporated by reference in its entirety and in particular all figures, legends and disclosure related to models of DNA-anti-DNA immune complex generation and glomerular damage in lupus nephritis and potential therapeutic targets. See also Sekita K, Doi T, Muso E, Yoshida H, Kanatsu K, Hamashima Y (1984) Clin Exp Immunol “Correlation of C3d fixing circulating immune complexes with disease activity and clinical parameters in patients with systemic lupus erythematosus,” 55(3):487-494, which is hereby incorporated by reference in its entirety and in particular all figures, legends and disclosure related to CIC levels and anti-C3d assays from patients with various diseases.

[0012] The natural receptor for C3d is the complement receptor 2 (CR2), also known as CD21, expressed on the surface of B cells. CR2 serves as a link to from the innate to the adaptive immune system, and in healthy conditions, the interaction of C3d-tagged immune complexes leads to an amplified B cell/antibody response to the offending antigen. Unfortunately, in autoimmune diseases this amplification can lead to continuation of an auto-antibody response to autoantigen, further exacerbating the disease.

[0013] Soluble CRs, CR-Fc fusions, and anti-C3d antibodies have been described for therapeutic purposes. These include CR1, CR2-Fc (U.S. Pat. No. 6,458,360), CR2-fH (CR2-factor H), anti-C3d antibodies (Thurman et al., J. Clinical Invest. 123(5):2218 (2013); US20130129728A1), and others. However, while these approaches generally block interaction of C3-tagged ICs with their associated receptors, they do not necessarily remove the immune complexes from circulation. Most of the complement receptors and regulatory proteins are composed of one or more so-called short complement repeat (SCR) domains, also called complement control protein (CCP) modules or Sushi domains. Typically, only a subset of the domains is involved in direct recognition of the associated complement fragment ligand. For example, it has been demonstrated that only the first two SCRs of CR2 are essential for C3d binding. The SCR domains are stable and well-behaved, making them suitable for use in the development of therapeutic proteins.

[0014] Of further relevance to the present invention relates to the mechanisms of hemophilia. One issue with hemophiliacs is the effect that Factor VIII (FVIII (not to be confused with “Fv”)) inhibitors play in disease. Currently, these FVIII inhibitors (generally FVIII antibodies, as shown in FIG. 28) are a huge problem for hemophiliacs.

[0015] Accordingly, in one aspect the present invention provides compositions and methods for rapidly lowering the serum concentration of an antigen in a patient comprising administering an antibody comprising a variable region that binds the antigen and a variant Fc domain comprising an amino acid substitution as compared to a parent Fc domain wherein said variant Fc domain binds humanFcγRIIb with increased affinity as compared to said parent Fc domain. These antibodies bind to said antigen to form an antibody-antigen complex and said complex is cleared at least two fold faster than the antigen alone.

[0016] In a further aspect, the present invention provides compositions and methods for lowering the free antigen in a patient comprising administering an antibody comprising a variable region that binds the antigen and a variant Fc domain comprising an amino acid substitution as compared to a parent Fc domain wherein said variant Fc domain binds FcγRIIb with increased affinity as compared to said parent Fc domain. The administration results in the concentration of said free antigen decreasing at least 50% more rapidly than the decrease in concentration seen with an antibody comprising the parent Fc domain.

[0017] In a further aspect, the present invention provides compositions and methods for differentially clearing an antibody-antigen complex in a patient compared to antibody alone, comprising administering an antibody comprising a variable region that binds the antigen and a variant Fc domain comprising an amino acid substitution as compared to a parent Fc domain wherein said variant Fc domain binds FcγRIIb with increased affinity as compared to said parent Fc domain. These antibodies bind to the antigen to form an antibody-antigen complex and the complex is cleared at least two fold faster than the antigen alone.

[0018] In one embodiment and in accordance with any of the above, the invention provides methods wherein the variant Fc domain comprises amino acid substitutions selected from the group consisting of those of FIG. 30, FIG. 47, and FIG. 48.

[0019] In a further embodiment and in accordance with any of the above, the present invention provides compositions and methods wherein the variant Fc domain further comprises amino acid substitutions selected from the group consisting of 434S, 434A, 428L, 308F, 259I, 428L/434S, 259I/308F, 436I/428L, 436I or V/434S, 436V/428L and 259I/308F/428L.

[0020] In a yet further embodiment and in accordance with any of the above, according to any previous claim, the present invention provides compositions and methods wherein the increased affinity seen with the variant Fc domain is at least a 5-fold or a 10-fold increase as compared to the parent Fc domain as measured by a Biacore assay.

[0021] In a still further embodiment and in accordance with any of the above, the present invention provides compositions and methods that lower serum concentration of antigen, where the antigen is selected from the group consisting of IgE, oxoLDL, and FVIII inhibitor.

[0022] In a still further embodiment and in accordance with any of the above, the present invention provides compositions and methods in which the antibody includes a variable region VH domain that comprises a CDR1 of SEQ ID NO:2, a CDR2 of SEQ ID NO:3 and a CDR3 of SEQ ID NO:4 and a variable region VL domain that comprises a CDR1 of SEQ ID NO:6, a CDR2 of SEQ ID NO:7 and a CDR3 of SEQ ID NO:8.

[0023] In a still further embodiment and in accordance with any of the above, the present invention provides compositions and methods in which the antibody includes a variable region VH domain that comprises a CDR1 of SEQ ID NO:18, a CDR2 of SEQ ID NO:19 and a CDR3 of SEQ ID NO:20 and a variable region VL domain that comprises a CDR1 of SEQ ID NO:22, a CDR2 of SEQ ID NO:23 and a CDR3 of SEQ ID NO:24.

[0024] In a still further embodiment and in accordance with any of the above, the present invention provides compositions and methods in which the variant Fc domain comprises amino acid substitutions selected from the group consisting of S267E, S267D, L328F, P238D, S267E/L328F, G236N/S267E, G236D/S267E.

[0025] In a further aspect, the present invention provides a method of rapidly lowering the serum concentration of an antigen in a patient, where the method includes the step of: administering an Fc fusion protein comprising: (i) a binding moiety that binds the antigen; and (ii) a variant Fc domain comprising an amino acid substitution as compared to a parent Fc domain, wherein the variant Fc domain binds FcγRIIb with increased affinity as compared to the parent Fc domain and the Fc fusion protein binds to the antigen to form a protein-antigen complex that is cleared at least two fold faster than the antigen alone.

[0026] In a further aspect, the present invention provides compositions and methods for lowering the free antigen in a patient comprising administering an Fc fusion protein comprising a binding moiety that binds the antigen and a variant Fc domain comprising an amino acid substitution as compared to a parent Fc domain wherein said variant Fc domain binds FcγRIIb with increased affinity as compared to said parent Fc domain. The administration results in the concentration of said free antigen decreasing at least 50% more rapidly than the decrease in concentration seen with an antibody comprising the parent Fc domain.

[0027] In a further aspect, the present invention provides compositions and methods for clearing an antibody-antigen complex in a patient compared to antibody alone, by administering an Fc fusion protein comprising: (i) a binding moiety that binds to the antigen; and (ii) a variant Fc domain comprising an amino acid substitution as compared to a parent Fc domain, wherein the variant Fc domain binds FcγRIIb with increased affinity as compared to said parent Fc domain; and wherein the Fc fusion protein binds to said antigen to form a protein-antigen complex and said complex is cleared at least two fold faster than the protein alone.

[0028] In a further embodiment in accordance with any of the above, the methods and compositions of the invention include the use of a fusion protein containing a binding moiety that has a sequence selected from FIG. 33A or 33B.

[0029] In a further embodiment in accordance with any of the above, the methods and compositions of the invention include the use of an Fc fusion protein that has a first monomer and a second monomer, and the first monomer comprises the sequence shown in FIG. 33C and the second monomer has the sequence shown in FIG. 33D.

[0030] In a further embodiment in accordance with any of the above, the methods and compositions of the invention include the use of an Fc fusion protein that has a first monomer and a second monomer, and the first monomer comprises the sequence shown in FIG. 33E and the second monomer has the sequence shown in FIG. 33D.

[0031] In a yet further embodiment in accordance with any of the above, the methods and compositions of the invention include the use of an Fc fusion protein that has a first domain comprising a CR2 sequence and a second domain comprising an engineered Fc domain. In still further embodiments, the fusion protein sequence is selected from the sequences depicted in FIG. 40.

[0032] In a further aspect, the present invention provides methods and compositions for treating an IgE-mediated disease in a patient by rapidly lowering serum concentration of IgE in said patient by administering an antibody that has (i) a variable region that binds IgE; and (ii) a variant Fc domain comprising an amino acid substitution as compared to a parent Fc domain, where variant Fc domain binds FcγRIIb with increased affinity as compared to the parent Fc domain, and where the antibody binds to the IgE to form an antibody-IgE complex and the complex is cleared at least two fold faster than IgE alone. In certain embodiments, the variant Fc domain comprises amino acid substitutions selected from the group consisting of S267E, S267D, L238F, P238D, S267E/L328F, G236N/S267E, G236D/S267E. In further embodiments, the IgE mediated disease is selected from the group consisting of: asthma, allergic rhinitis, atopic dermatitis, and food allergy.

[0033] In a further aspect, the present invention provides methods and compositions for treating an autoimmune disorder in a patient by rapidly lowering serum concentration of C3d in the patient by administering a rapid clearance molecule comprising: (i) a variable region that binds C3d; and (ii) a variant Fc domain comprising an amino acid substitution as compared to a parent Fc domain, where the variant Fc domain binds FcγRIIb with increased affinity as compared to said parent Fc domain, and where the rapid clearance molecule binds to the C3d to form a molecule-C3d complex and the complex is cleared at least two fold faster than C3d alone. In certain embodiments, the variant Fc domain comprises amino acid substitutions selected from the group consisting of S267E, S267D, L238F, P238D, S267E/L328F, G236N/S267E, G236D/S267E. In further embodiments, the autoimmune disorder is selected from the group consisting of: systemic lupus erythematosus and rheumatoid arthritis. In yet further embodiments, the rapid clearance molecule is an antibody or an Fc fusion protein.

[0034] In a further aspect, the present invention provides methods and compositions for treating atherosclerosis in a patient by rapidly lowering serum concentration of oxLDL in the patient by administering a rapid clearance molecule that has: (i) a variable region that binds oxLDL; and (ii) a variant Fc domain comprising an amino acid substitution as compared to a parent Fc domain, where the variant Fc domain binds FcγRIIb with increased affinity as compared to the parent Fc domain; and where the rapid clearance molecule binds to the oxLDL to form a molecule-oxLDL complex that is cleared at least two fold faster than oxLDL alone. In certain embodiments, the variant Fc domain comprises amino acid substitutions selected from the group consisting of S267E, S267D, L238F, P238D, S267E/L328F, G236N/S267E, G236D/S267E. In yet further embodiments, the rapid clearance molecule is an antibody or an Fc fusion protein.

[0035] In a further aspect, the present invention provides methods and compositions for treating treating hemophilia in a patient by rapidly lowering serum concentration of FVIII inhibitor in said patient by administering a rapid clearance molecule comprising (i) a variable region that binds said FVIII inhibitor; and (ii) a variant Fc domain comprising an amino acid substitution as compared to a parent Fc domain, wherein the variant Fc domain binds FcγRIIb with increased affinity as compared to the parent Fc domain and wherein the rapid clearance molecule binds to the FVIII inhibitor to form a molecule-inhibitor complex and the complex is cleared at least two fold faster than FVIII inhibitor alone. In certain embodiments, the variant Fc domain comprises amino acid substitutions selected from the group consisting of S267E, S267D, L238F, P238D, S267E/L328F, G236N/S267E, G236D/S267E. In yet further embodiments, the rapid clearance molecule is an antibody or an Fc fusion protein.

[0087] The in vivo pharmacokinetic properties of therapeutic antibodies can be altered through modification of their Fc domain. Such modifications may include amino acid substitutions, deletions, or additions as well as other modifications such as chemical modifications. In the present invention, modifications that increase affinity of molecules such as antibodies for the inhibitory Fc receptor FcγRIIb (CD32b) are utilized to facilitate rapid in vivo clearance of complexes comprising the antigen and the molecule of the invention. Incorporation of the IIb-enhancing affinity modifications (also referred to herein as “FcγRIIb variants” or “FcγRIIb variations” or grammatical equivalents thereof) into various antibodies leads to a novel phenomenon whereby the antibody-target complex is cleared extremely rapidly while the antibody alone retains a reasonably long half-life. Although much of the discussion herein is directed to antibodies for the sake of clarity, it will be appreciated that discussion of the FcγRIIb variants described herein are applicable to any of the rapid clearance molecules described herein, including polypeptides, antibodies, and Fc fusion proteins.

[0088] The present invention provides methods of rapidly lowering the serum concentration of an antigen in a subject by administering an antibody that has both a variable region that binds the antigen and a variant Fc domain that binds the FcγRIIb receptor with increased affinity as compared to an un-modified Fc domain. Without being bound by theory, it appears that an antibody of the invention binds to the antigen to form an antibody-antigen complex that is cleared more rapidly than the unbound antigen. Thus, the free antigen concentration in the patient, e.g. the serum concentration of free antigen in the patient, is rapidly decreased. In other words, the antigen-antibody complex is differentially cleared (e.g. clearance of complex/clearance of antigen ratio is greater than 1). In some cases, the methods and compositions of the present invention clear an antibody-antigen complex at least 2, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300-fold faster than clearance of the antigen alone. In certain cases the methods and compositions of the present invention clear an antibody-antigen complex 5-500, 50-450, 100-400, 200-350, 100-200-fold faster than clearance of the antigen alone. In other cases, clearance rates of 25× faster than antigen alone, 50×, 75× and 100× or more are provided by methods and compositions of the present invention. In some cases, the methods and compositions of the present invention decrease the clearance rate of an antibody-antigen complex by at least 30%, 40%, 50%, 60%, 70%, 80% 90%, 95%, or 99% as compared to the clearance rate of the antigen alone. In some cases, the methods and compositions of the present invention decrease the clearance rate of an antibody-antigen complex by at least 30%, 40%, 50%, 60%, 70%, 80% 90%, 95%, or 99% as compared to the clearance rate mediated by an antibody comprising a parent (un-modified) Fc domain.

[0089] Thus, compositions of the present invention include such “rapid clearance” molecules (also referred to as “scrubbers”) of the present invention that lead to clearance of the antibody-antigen complex more rapidly than the unbound antigen or antibody alone. Such rapid clearance compositions are generally polypeptides that comprise two domains: an antigen or ligand binding portion and an Fc domain that exhibits increased FcγRIIb binding as compared to a non-engineered Fc region. In some embodiments, as is further described herein, the rapid clearance molecules are antibodies, comprising a standard antigen binding Fv region, and a variant FcγRIIb binding region, e.g. an engineered Fc region. In alternative embodiments, the rapid clearance molecule is an Fc fusion protein, with a binding ligand or receptor as one domain (e.g. a CR domain) and an Fc region with increased FcγRIIb binding. In addition to the fasterclearance rates described above as compared to clearance of antigen alone, rapid clearance molecules of the invention further clear the antigen-containing complex more rapidly than IgG antibodies with the same selectivity would mediate.

[0090] Application of different FcγRIIb-enhancing Fc amino acid substitutions with varying affinities to the FcγRIIb receptor (e.g. S267E, S267D, L328F, P238D, S267E/L328F, G236N/S267E, and G236D/S267E, as further described herein) can allow some “tuning” of how fast the complex antigen is cleared while maintaining significant half life of the rapid clearance composition of the invention (including antibodies). That is, different amino acid substitutions that alter FcγRIIb binding affinity may lead to different balances between the complex clearance rate and the antibody clearance rate, allowing for tailoring toward optimal therapeutic profile and dosing. This tuning may be accomplished by using amino acid substitutions in the Fc domain that increase binding to FcγRIIb as compared to the parent Fc domain. This increase in binding may be tuned by using Fc variants with 1-100, 5-90, 10-80, 15-70, 20-60, 30-50, 10-20 fold greater affinity as compared to the parent Fc domain. This increase in binding may also be tuned by using Fc variants with 50-200, 60-190, 70-180, 80-170, 90-160, 100-150, 110-140, 120-130, 50-100 greater affinity as compared to the parent Fc domain. In some cases, affinity is measured by Biacore as described in Example 2.

[0091] In certain cases, molecules of the invention incorporate FcγRIIb receptor variants that can range from very tight differential binding to FcγRIIb to variants that display increased (as compared to wild type Fc domains) binding affinity but at a lower level. For example, very tight (or heavy) binding to FcγRIIb receptor may include FcγRIIb variants that show at least 50, 75, 100, 125, 150, 175, 200, 225, 250-fold greater affinity to FcγRIIb receptor as compared to the parent Fc domain. In contrast, a lower level (or light, also referred to herein as “lite”) increase in binding may include FcγRIIb variants that show no more than 50, 40, 30, 20, 10, 5-fold greater affinity to FcγRIIb receptor as compared to the parent Fc domain.

[0092] The effects of molecules of the invention may be further tuned by combining amino acid substitutions that alter FcγRIIb binding affinity with amino acid substitutions that affect binding to FcRn. Proteins with amino acid substitutions that affect binding to FcRn (also referred to herein as “FcRn variants”) may in certain situations also increase serum half-life in vivo as compared to the parent protein. As will be appreciated, any combination of Fc and FcRn variants may be used to tune clearance of the antigen-antibody complex. Suitable FcRn variants that may be combined with any of the Fc variants described herein include without limitation 434A, 434S, 428L, 308F, 259I, 428L/434S, 259I/308F, 436I/428L, 436I/434S, 436V/434S, 436V/428L, 252Y, 252Y/254T/256E, and 259I/308F/428L.

[0093] Without being bound by theory, it appears that the accelerated clearance of antibodies containing amino acid substitutions that confer high affinity (as compared to the parent Fc domain) to the inhibitory receptor FcγRIIb is likely mediated by interaction with FcγRIIb-expressing cells, possibly liver sinusoidal endothelial cells. In addition, it appears that the accelerated clearance is due to the clearance of the antigen-antibody complex via interactions with the FcγRIIb receptor.

[0094] In addition, unexpectedly, administration of antibodies including the FcγRIIb binding affinity variants described herein leads to near instantaneous drops in total antigen levels, whereas administration of other antibodies to the antigen that lack modifications that lead to increased FcγRIIb binding affinity often lead to increases in total antigen levels. Furthermore, the greater reduction in total antigen levels seen with antibodies with increased FcγRIIb binding affinity leads to superior reduction of free antigen relative to levels seen with antibodies that lack the FcγRIIb variants.

[0095] In addition, in some cases, compositions and methods of the invention provide sufficient increased affinity to the FcγRIIb receptor to allow for rapid clearance of the antibody-antigen complex while allowing appropriate serum half lives of the unbound antibodies.

[0096] The invention is exemplified in the case of XmAb7195. XmAb7195 is an anti-IgE antibody that sequesters IgE and prevents its interaction with FceR1 on mast cells and basophils. The variable region is similar to the variable region of omalizumab (Xolair, an anti-IgE antibody). The XmAb7195 Fc domain was engineered with the S267E/L328F substitutions (Kabat numbering) to confer high affinity to human FcγRIIb. A single 5 mg/kg dose of XmAb7195 was administered via intravenous injection to chimpanzees (n=3) and its effects on free and total IgE were compared to that of omalizumab (anti-IgE with native IgG1 Fc domain). As shown in FIG. 22, the XmAb7195 antibody had a relatively short half-life of approximately 2 days, and the omalizumab exhibited a longer half-life of approximately 11 days.

[0097] Unexpectedly, the XmAb7195 antibody also led to a near-instantaneous drop of total IgE levels, whereas the omalizumab treatment led to an increase in total IgE (as observed in humans treated with omalizumab). The XmAb7195-IgE complexes exhibited greatly accelerated clearance presumably via their interaction with FcRIIb. Furthermore, the greater reduction of total IgE using XmAb7195 led to superior reductions of free IgE relative to omalizumab-treated animals. PK/PD simulations suggest that the half-life of the XmAb7195/IgE complexes are on the order of 1 hour—versus an 8 day half-life reported for omalizumab/IgE complexes. Furthermore, the present invention also suggests that rapid recovery of the antigen can occur after cessation of antibody administration.

[0098] This surprising and unexpected result, e.g. that adding FcγRIIb variants to existing antibodies can rapidly clear antigen in patients leads to a number of useful applications. Any therapeutic target antigen system in which rapid clearance of the antigen is desired can be subjected to the present invention. For example, disease systems in which the antigen load is high find particular use in the present invention. Similarly, disease systems where rapid recovery of the antigen is desired after antibody administration can be treated with the antibodies of the invention. For example, during the use of TNF antibody inhibitors, patients frequently get infections. Withdrawing the antibody treatment will allow rapid recovery of the TNF to fight the infection. Similarly, these antibodies can be used to treat pathogen infection when rapid pathogen clearance is desired (for example, when a patient scheduled for surgery gets an infection, the present invention can be used to clear the infection rapidly, the therapeutic antibody rapidly clears as well and surgery can progress). In addition, these antibodies may be particularly useful in situations where existing antibodies do not neutralize the antigen, or where pathogens evolve to evade neutralization.

[0099] In addition, the invention finds use in the treatment of hemophiliacs. One issue with hemophiliacs is the effect that Factor VIII (FVIII (not to be confused with “Fv”)) inhibitors play in disease. Currently, these FVIII inhibitors (generally FVIII antibodies, as shown in FIG. 28) are a huge problem for hemophiliacs. The present invention works as generally outlined in FIGS. 28 and 29. Fc fusion proteins, comprising an Fc domain with FcγRIIb amino acid variants, fused to FVIIIa components as outlined herein, will sequester the inhibitor antibodies, rapidly clear the inhibitor antibodies, and will inhibit FVII-reactive B cells (to prohibit the further production of the inhibitors).

[0100] The rapid clearance mechanisms of the present invention are also used to remove oxidized low-density lipoprotein (oxidized LDL or oxLDL) from the blood. OxLDL is a key facilitator of atherosclerosis via macrophage uptake and foam cell formation (see FIG. 42). In this embodiment, increased affinity for the inhibitory Fc receptor FcγRIIb (CD32b) is utilized to facilitate rapid in vivo clearance of oxLDL via their interaction with Fc-containing oxLDL-binding proteins. Incorporation of the Ilb-enhancing affinity substitutions into various Fc-containing oxLDL-binding proteins leads to a novel phenomenon whereby the complex is cleared extremely rapidly. Application of different IIb-enhancing substitutions (including without limitation S267E, S267D, L328F, P238D, S267E/L328F, G236N/S267E, and G236D/S267E, which are useful for all the rapid clearance molecules herein) may lead to different balances between the complex clearance rate and the Fc-containing oxLDL-binding protein clearance rate, allowing for tailoring toward optimal therapeutic profile and dosing.

[0101] In addition, the invention finds use in a variety of diseases or situations where plasmapherisis is typically applied to clear the body of pathogens, autoantibodies, or other pathogenic factors. Such diseases include, but are not limited to, the following: Guillain-Barré syndrome; Chronic inflammatory demyelinating polyneuropathy; Goodpasture's syndrome; Hyperviscosity syndromes: Cryoglobulinemia; Paraproteinemia; Waldenström macroglobulinemia; Myasthenia gravis; Thrombotic thrombocytopenic purpura (TTP)/hemolytic uremic syndrome; Wegener's granulomatosis; Lambert-Eaton Syndrome; Antiphospholipid Antibody Syndrome (APS or APLS); Microscopic polyangiitis; Recurrent focal and segmental glomerulosclerosis in the transplanted kidney; HELLP syndrome; PANDAS syndrome; Refsum disease; Behcet syndrome; HIV-related neuropathy; Graves' disease in infants and neonates; Pemphigus vulgaris; Multiple sclerosis; Rhabdomyolysis; Toxic Epidermal Necrolysis (TEN). That is, by using FcγRIIb antibodies with variable regions specific to these antigens, clearance of the antigens in a rapid manner can occur.

[0102] Described herein are several definitions. Such definitions are meant to encompass grammatical equivalents.

[0103] By “ablation” herein is meant a decrease or removal of activity. Thus for example, “ablating FcγR binding” means the Fc region amino acid variant has less than 50% starting binding as compared to an Fc region not containing the specific variant, with less than 70-80-90-95-98% loss of activity being preferred, and in general, with the activity being below the level of detectable binding in a Biacore assay. Of particular use in the ablation of FcγR binding is the double variant 236R/328R, and 236R and 328R separately as well.

[0104] By “ADCC” or “antibody dependent cell-mediated cytotoxicity” as used herein is meant the cell-mediated reaction wherein nonspecific cytotoxic cells that express FcγRs recognize bound antibody on a target cell and subsequently cause lysis of the target cell. The role of high affinity binding to FcγRIIIa to ADCC activity is well established. In some cases, as described herein, amino acid substitutions in the Fc domain can be used to increase or decrease binding to one or more of the FcγR receptors, as is generally outlined in US Publication 2006/0024298, hereby incorporated by reference in its entirety and in particular for the amino acid substitutions disclosed therein, FIG. 41 as well as the other figures and their accompanying legends in particular. In addition, for some embodiments outlined herein, it may be desirable to ablate binding to one or more of the FcγR receptors. For example, the L328F variant ablates FcγRIIIa binding, such that ADCC mechanisms are not triggered. In addition, significant ablatement of FcγR binding to all receptors can be accomplished using 236R/328R variants.

[0105] By “ADCP” or antibody dependent cell-mediated phagocytosis as used herein is meant the cell-mediated reaction wherein nonspecific cytotoxic cells that express FcγRs recognize bound antibody on a target cell and subsequently cause phagocytosis of the target cell.

[0106] By “amino acid modification” herein is meant an amino acid substitution, insertion, and/or deletion in a polypeptide sequence. By “amino acid substitution” or “substitution” herein is meant the replacement of an amino acid at a particular position in a parent polypeptide sequence with a different amino acid. In particular, in some embodiments, the substitution is to an amino acid that is not naturally occurring at the particular position, either not naturally occurring within the organism or in any organism. For example, the substitution E272Y refers to a variant polypeptide, in this case an Fc variant, in which the glutamic acid at position 272 is replaced with tyrosine. For clarity, a protein which has been engineered to change the nucleic acid coding sequence but not change the starting amino acid (for example exchanging CGG (encoding arginine) to CGA (still encoding arginine) to increase host organism expression levels) is not an “amino acid substitution”; that is, despite the recombinant creation of a new gene encoding the same protein, if the protein has the same amino acid at the particular position that it started with, it is not an amino acid substitution.—By “amino acid insertion” or “insertion” as used herein is meant the addition of an amino acid at a particular position in a parent polypeptide sequence. By “amino acid deletion” or “deletion” as used herein is meant the removal of an amino acid at a particular position in a parent polypeptide sequence.

[0107] By “antibody” herein is meant a protein consisting of one or more polypeptides substantially encoded by all or part of the recognized immunoglobulin genes. The recognized immunoglobulin genes, for example in humans, include the kappa (κ), lambda (λ), and heavy chain genetic loci, which together comprise the myriad variable region genes, and the constant region genes mu (ν), delta (δ), gamma (γ), sigma (σ), and alpha (α) which encode the IgM, IgD, IgG (IgG1, IgG2, IgG3, and IgG4), IgE, and IgA (IgA1 and IgA2) isotypes respectively. Antibody herein is meant to include full length antibodies and antibody fragments, and may refer to a natural antibody from any organism, an engineered antibody, or an antibody generated recombinantly for experimental, therapeutic, or other purposes.

[0108] By “amino acid” and “amino acid identity” as used herein is meant one of the 20 naturally occurring amino acids or any non-natural analogues that may be present at a specific, defined position.

[0109] By “CD32b+ cell” or “FcγRIIb+ cell” as used herein is meant any cell or cell type that expresses CD32b (FcγRIIb). CD32b+ cells include but are not limited to B cells, plasma cells, dendritic cells, macrophages, neutrophils, mast cells, basophils, or eosinophils.

[0110] By “IgE+ cell” as used herein is meant any cell or cell type that expresses IgE. In preferred embodiments of the invention, IgE+ cells express membrane-anchored IgE (m IgE). IgE+ cells include but are not limited to B cells and plasma cells.

[0111] By “CDC” or “complement dependent cytotoxicity” as used herein is meant the reaction wherein one or more complement protein components recognize bound antibody on a target cell and subsequently cause lysis of the target cell.

[0112] By “molecule” or grammatical equivalents is meant a bifunctional molecule capable of binding both antigen and FcγRIIb wherein the Kd for binding of the molecule to FcγRIIb is less than about 100 nM on a cell surface resulting in simultaneous binding of both the antigen to which the antibody is directed and FcγRIIb.

[0113] By “constant region” of an antibody as defined herein is meant the region of the antibody that is encoded by one of the light or heavy chain immunoglobulin constant region genes. By “constant light chain” or “light chain constant region” as used herein is meant the region of an antibody encoded by the kappa (Cκ) or lambda (Cλ) light chains. The constant light chain typically comprises a single domain, and as defined herein refers to positions 108-214 of Cκ or Cλ, wherein numbering is according to the EU index. By “constant heavy chain” or “heavy chain constant region” as used herein is meant the region of an antibody encoded by the mu, delta, gamma, alpha, or epsilon genes to define the antibody's isotype as IgM, IgD, IgG, IgA, or IgE, respectively. For full length IgG antibodies, the constant heavy chain, as defined herein, refers to the N-terminus of the CH1 domain to the C-terminus of the CH3 domain, thus comprising positions 118-447, wherein numbering is according to the EU index.

[0114] By “effector function” as used herein is meant a biochemical event that results from the interaction of an antibody Fc region with an Fc receptor or ligand. Effector functions include FcγR-mediated effector functions such as ADCC and ADCP, and complement-mediated effector functions such as CDC.

[0115] By “effector cell” as used herein is meant a cell of the immune system that expresses one or more Fc and/or complement receptors and mediates one or more effector functions. Effector cells include but are not limited to monocytes, macrophages, neutrophils, dendritic cells, eosinophils, mast cells, platelets, B cells, large granular lymphocytes, Langerhans' cells, natural killer (NK) cells, and γδ T cells, and may be from any organism including but not limited to humans, mice, rats, rabbits, and monkeys.

[0116] By “Fab” or “Fab region” as used herein is meant the polypeptides that comprise the VH, CH1, VH, and CL immunoglobulin domains. Fab may refer to this region in isolation, or this region in the context of a full length antibody or antibody fragment.

[0117] By “Fc” or “Fc region”, as used herein is meant the polypeptide comprising the constant region of an antibody excluding the first constant region immunoglobulin domain and in some cases, part of the hinge. Thus Fc refers to the last two constant region immunoglobulin domains of IgA, IgD, and IgG, and the last three constant region immunoglobulin domains of IgE and IgM, and the flexible hinge N-terminal to these domains. For IgA and IgM, Fc may include the J chain. For IgG, Fc comprises immunoglobulin domains Cgamma2 and Cgamma3 (Cγ2 and Cγ3) and the hinge between Cgamma1 (Cγ1) and Cgamma2 (Cγ2). Although the boundaries of the Fc region may vary, the human IgG heavy chain Fc region is usually defined to comprise residues C226 or P230 to its carboxyl-terminus, wherein the numbering is according to the EU index as in Kabat. Fc may refer to this region in isolation, or this region in the context of an Fc polypeptide, as described below.

[0118] By “Fc polypeptide” as used herein is meant a polypeptide that comprises all or part of an Fc region. Fc polypeptides include antibodies, Fc fusions, isolated Fcs, and Fc fragments. Immunoglobulins may be Fc polypeptides.

[0119] By “Fc fusion” as used herein is meant a protein wherein one or more polypeptides is operably linked to Fc. Fc fusion is herein meant to be synonymous with the terms “immunoadhesin”, “Ig fusion”, “Ig chimera”, and “receptor globulin” (sometimes with dashes) as used in the prior art (Chamow et al., 1996, Trends Biotechnol 14:52-60; Ashkenazi et al., 1997, Curr Opin Immunol 9:195-200, both hereby entirely incorporated by reference). An Fc fusion combines the Fc region of an immunoglobulin with a fusion partner, which in general may be any protein, polypeptide or small molecule. The role of the non-Fc part of an Fc fusion, i.e., the fusion partner, is to mediate target binding, and thus it is functionally analogous to the variable regions of an antibody. Virtually any protein or small molecule may be linked to Fc to generate an Fc fusion. Protein fusion partners may include, but are not limited to, the target-binding region of a receptor, an adhesion molecule, a ligand, an enzyme, a cytokine, a chemokine, or some other protein or protein domain. Small molecule fusion partners may include any therapeutic agent that directs the Fc fusion to a therapeutic target. Such targets may be any molecule, e.g., an extracellular receptor that is implicated in disease.

[0120] By “Fc gamma receptor” or “FcγR” as used herein is meant any member of the family of proteins that bind the IgG antibody Fc region and are substantially encoded by the FcγR genes. In humans this family includes but is not limited to FcγRI (CD64), including isoforms FcγRIa, FcγRIb, and FcγRIlc; FcγRII (CD32), including isoforms FcγRIIa (including allotypes H131 and R131), FcγRIIb (including FcγRIIb-1 and FcγRIIb-2), and FcγRIIc; and FcγRIII (CD16), including isoforms FcγRIIIa (including allotypes V158 and F158) and FcγRIIIb (including allotypes FcγRIIIb-NA1 and FcγRIIlb-NA2) (Jefferis et al., 2002, Immunol Lett 82:57-65, incorporated entirely by reference), as well as any undiscovered human FcγRs or FcγR isoforms or allotypes. An FcγR may be from any organism, including but not limited to humans, mice, rats, rabbits, and monkeys. Mouse FcγRs include but are not limited to FcγRI (CD64), FcγRII (CD32), FcγRIII (CD16), and FcγRIII-2 (CD16-2), as well as any undiscovered mouse FcγRs or FcγR isoforms or allotypes.

[0121] By “Fc ligand” or “Fc receptor” as used herein is meant a molecule, e.g., a polypeptide, from any organism that binds to the Fc region of an antibody to form an Fc-ligand complex. Fc ligands include but are not limited to FcγRs, FcγRs, FcγRs, FcRn, C1q, C3, mannan binding lectin, mannose receptor, staphylococcal protein A, streptococcal protein G, and viral FcγR. Fc ligands also include Fc receptor homologs (FcRH), which are a family of Fc receptors that are homologous to the FcγRs (Davis et al., 2002, Immunological Reviews 190:123-136). Fc ligands may include undiscovered molecules that bind Fc.

[0122] By “full length antibody” as used herein is meant the structure that constitutes the natural biological form of an antibody, including variable and constant regions. For example, in most mammals, including humans and mice, the full length antibody of the IgG isotype is a tetramer and consists of two identical pairs of two immunoglobulin chains, each pair having one light and one heavy chain, each light chain comprising immunoglobulin domains VL and CL, and each heavy chain comprising immunoglobulin domains VH, Cγ1, Cγ2, and Cγ3. In some mammals, for example in camels and llamas, IgG antibodies may consist of only two heavy chains, each heavy chain comprising a variable domain attached to the Fc region.

[0123] By “immunoglobulin” herein is meant a protein comprising one or more polypeptides substantially encoded by immunoglobulin genes. Immunoglobulins include but are not limited to antibodies (including bispecific antibodies) and Fc fusions. Immunoglobulins may have a number of structural forms, including but not limited to full length antibodies, antibody fragments, and individual immunoglobulin domains.

[0124] By “immunoglobulin (Ig) domain” as used herein is meant a region of an immunoglobulin that exists as a distinct structural entity as ascertained by one skilled in the art of protein structure. Ig domains typically have a characteristic β-sandwich folding topology. The known Ig domains in the IgG isotype of antibodies are VH Cγ1, Cγ2, Cγ3, VL, and CL.

[0125] By “IgG” or “IgG immunoglobulin” or “immunoglobulin G” as used herein is meant a polypeptide belonging to the class of antibodies that are substantially encoded by a recognized immunoglobulin gamma gene. In humans this class comprises the subclasses or isotypes IgG1, IgG2, IgG3, and IgG4.

[0126] By “IgE” or “IgE immunoglobulin” or “immunoglobulin E” as used herein is meant a polypeptide belonging to the class of antibodies that are substantially encoded by a recognized immunoglobulin epsilon gene. IgE may be membrane-anchored (mIgE), or non-membrane-anchored, also referred to herein as circulating IgE.

[0127] By “inhibition” of cells or grammatical equivalents is meant preventing or reducing the activation, proliferation, maturation or differentiation of targeted cells.

[0128] By “isotype” as used herein is meant any of the subclasses of immunoglobulins defined by the chemical and antigenic characteristics of their constant regions. The known human immunoglobulin isotypes are IgG1, IgG2, IgG3, IgG4, IgA1, IgA2, IgM, IgD, and IgE.

[0129] By “modification” herein is meant an alteration in the physical, chemical, or sequence properties of a protein, polypeptide, antibody, or immunoglobulin. Modifications described herein include amino acid modifications and glycoform modifications.

[0130] By “glycoform modification” or “modified glycoform” or “engineered glycoform” as used herein is meant a carbohydrate composition that is covalently attached to a protein, for example an antibody, wherein said carbohydrate composition differs chemically from that of a parent protein. Modified glycoform typically refers to the different carbohydrate or oligosaccharide; thus for example an Fc variant may comprise a modified glycoform. Alternatively, modified glycoform may refer to the Fc variant that comprises the different carbohydrate or oligosaccharide.

[0131] By “parent polypeptide”, “parent protein”, “parent immunoglobulin”, “parent Fc domain”, “precursor polypeptide”, “precursor protein”, or “precursor immunoglobulin” as used herein is meant an unmodified polypeptide, protein, Fc domain, or immunoglobulin that is subsequently modified to generate a variant, e.g., any polypeptide, protein or immunoglobulin which serves as a template and/or basis for at least one amino acid modification described herein. The parent polypeptide may be a naturally occurring polypeptide, or a variant or engineered version of a naturally occurring polypeptide. Parent polypeptide may refer to the polypeptide itself, compositions that comprise the parent polypeptide, or the amino acid sequence that encodes it. Accordingly, by “parent Fc polypeptide” as used herein is meant an Fc polypeptide that is modified to generate a variant Fc polypeptide, and by “parent antibody” as used herein is meant an antibody that is modified to generate a variant antibody (e.g., a parent antibody may include, but is not limited to, a protein comprising the constant region of a naturally occurring Ig).

[0132] By “position” as used herein is meant a location in the sequence of a protein. Positions may be numbered sequentially, or according to an established format, for example the EU index as described in Kabat. For example, position 297 is a position in the human antibody IgG1.

[0133] By “polypeptide” or “protein” as used herein is meant at least two covalently attached amino acids, which includes proteins, polypeptides, oligopeptides and peptides.

[0134] By “residue” as used herein is meant a position in a protein and its associated amino acid identity. For example, Asparagine 297 (also referred to as Asn297, also referred to as N297) is a residue in the human antibody IgG1.

[0135] By “rapid clearance” or grammatical equivalents herein is meant that the antigen-antibody complex composition is cleared from the blood more quickly than either the antigen alone or the antibody, or a complex between the antigen and a parent analog of the antibody. As is understood in the art, antibodies with different Fvs may have different half lives in serum, so the comparison is to the starting antibody (e.g. an anti-IgE antibody without the IIb variants outlined herein) to the IIb engineered antibody. In general, “rapid clearance” are clearance rates of 25× faster than parent antibody, 50×, 75× and 100× or more. For example, as outlined herein, the anti-IgE IIb antibody of the examples shows a one hour clearance rate in chimps as compared to 2 days of either the parent Xolair antibody or an Fc IIb polypeptide that does not contain a binding moiety for IgE. Similarly, “clearance” can be measured as a reduction in free target antigen of 10%, 25%, 50% with 90 to 99% percentage of starting serum antigen concentration being a preferred clearance.

[0136] By “target antigen” as used herein is meant the molecule that is bound by the variable region of a given antibody, or the fusion partner of an Fc fusion. A target antigen may be a protein, carbohydrate, lipid, or other chemical compound. An antibody or Fc fusion is said to be “specific” for a given target antigen based on having affinity for the target antigen. A variety of target antigens are listed below.

[0137] Virtually any antigen may be targeted by the polypeptides of the invention, including but not limited to proteins, subunits, domains, motifs, and/or epitopes belonging to the following list of target antigens, which includes both soluble factors such as cytokines and membrane-bound factors. Proteins that may be target antigens of the invention include without limitation: IgE (soluble and/or membrane-bound), cytokines, e.g., IL-4, IL-6, IL-13, and TNFα; chemokines, e.g., MCP-1, RANTES, TARC, and MDC; growth factors, e.g., VEGF, HGF, and NGF; also, immune complexes, blood factor inhibitors, e.g. FVIII inhibitors, LDL, oxidized LDL, SOST, and DKK1. Target antigens may also include without limitation: 17-IA, 4-1BB, 4Dc, 6-keto-PGF1a, 8-iso-PGF2a, 8-oxo-dG, A1 Adenosine Receptor, A33, ACE, ACE-2, Activin, Activin A, Activin AB, Activin B, Activin C, Activin RIA, Activin RIA ALK-2, Activin RIB ALK-4, Activin RIIA, Activin RIIB, ADAM, ADAM10, ADAM12, ADAM15, ADAM17/TACE, ADAMS, ADAM9, ADAMTS, ADAMTS4, ADAMTS5, Addressins, aFGF, ALCAM, ALK, ALK-1, ALK-7, alpha-1-antitrypsin, alpha-V/beta-1 antagonist, ANG, Ang, APAF-1, APE, APJ, APP, APRIL, AR, ARC, ART, Artemin, anti-Id, ASPARTIC, Atrial natriuretic factor, av/b3 integrin, Axl, b2M, B7-1, B7-2, B7-H, B-lymphocyte Stimulator (BlyS), BACE, BACE-1, Bad, BAFF, BAFF-R, Bag-1, BAK, Bax, BCA-1, BCAM, Bcl, BCMA, BDNF, b-ECGF, bFGF, BID, Bik, BIM, BLC, BL-CAM, BLK, BMP, BMP-2 BMP-2a, BMP-3 Osteogenin, BMP-4 BMP-2b, BMP-5, BMP-6 Vgr-1, BMP-7 (OP-1), BMP-8 (BMP-8a, OP-2), BMPR, BMPR-IA (ALK-3), BMPR-IB (ALK-6), BRK-2, RPK-1, BMPR-II (BRK-3), BMPs, b-NGF, BOK, Bombesin, Bone-derived neurotrophic factor, BPDE, BPDE-DNA, BTC, complement factor 3 (C3), C3a, C4, C5, C5a, C10, CA125, CAD-8, Calcitonin, cAMP, carcinoembryonic antigen (CEA), carcinoma-associated antigen, Cathepsin A, Cathepsin B, Cathepsin C/DPPI, Cathepsin D, Cathepsin E, Cathepsin H, Cathepsin L, Cathepsin O, Cathepsin S, Cathepsin V, Cathepsin X/Z/P, CBL, CCI, CCK2, CCL, CCL1, CCL11, CCL12, CCL13, CCL14, CCL15, CCL16, CCL17, CCL18, CCL19, CCL2, CCL20, CCL21, CCL22, CCL23, CCL24, CCL25, CCL26, CCL27, CCL28, CCL3, CCL4, CCL5, CCL6, CCL7, CCL8, CCL9/10, CCR, CCR1, CCR10, CCR10, CCR2, CCR3, CCR4, CCR5, CCR6, CCR7, CCR8, CCR9, CD1, CD2, CD3, CD3E, CD4, CD5, CD6, CD7, CD8, CD10, CD11a, CD11b, CD11c, CD13, CD14, CD15, CD16, CD18, CD19, CD20, CD21, CD22, CD23, CD25, CD27L, CD28, CD29, CD30, CD30L, CD32, CD33 (p67 proteins), CD34, CD38, CD40, CD40L, CD44, CD45, CD46, CD49a, CD52, CD54, CD55, CD56, CD61, CD64, CD66e, CD74, CD80 (B7-1), CD89, CD95, CD123, CD137, CD138, CD140a, CD146, CD147, CD148, CD152, CD164, CEACAM5, CFTR, cGMP, CINC, Clostridium botulinum toxin, Clostridium perfringens toxin, CKb8-1, CLC, CMV, CMV UL, CNTF, CNTN-1, COX, C-Ret, CRG-2, CT-1, CTACK, CTGF, CTLA-4, CX3CL1, CX3CR1, CXCL, CXCL1, CXCL2, CXCL3, CXCL4, CXCL5, CXCL6, CXCL7, CXCL8, CXCL9, CXCL10, CXCL11, CXCL12, CXCL13, CXCL14, CXCL15, CXCL16, CXCR, CXCR1, CXCR2, CXCR3, CXCR4, CXCR5, CXCR6, cytokeratin tumor-associated antigen, DAN, DCC, DcR3, DC-SIGN, Decay accelerating factor, des(1-3)-IGF-1 (brain IGF-1), Dhh, digoxin, DNAM-1, Dnase, Dpp, DPPIV/CD26, Dtk, ECAD, EDA, EDA-A1, EDA-A2, EDAR, EGF, EGFR (ErbB-1), EMA, EMMPRIN, ENA, endothelin receptor, Enkephalinase, eNOS, Eot, eotaxin1, EpCAM, Ephrin B2/EphB4, EPO, ERCC, E-selectin, ET-1, Factor 10a, Factor VII, Factor VIIIc, Factor IX, fibroblast activation protein (FAP), Fas, FcR1, FEN-1, Ferritin, FGF, FGF-19, FGF-2, FGF3, FGF-8, FGFR, FGFR-3, Fibrin, FL, FLIP, Flt-3, Flt-4, Follicle stimulating hormone, Fractalkine, FZD1, FZD2, FZD3, FZD4, FZD5, FZD6, FZD7, FZD8, FZD9, FZD10, G250, Gas 6, GCP-2, GCSF, GD2, GD3, GDF, GDF-1, GDF-3 (Vgr-2), GDF-5 (BMP-14, CDMP-1), GDF-6 (BMP-13, CDMP-2), GDF-7 (BMP-12, CDMP-3), GDF-8 (Myostatin), GDF-9, GDF-15 (MIC-1), GDNF, GDNF, GFAP, GFRa-1, GFR-alpha1, GFR-alpha2, GFR-alpha3, GITR, Glucagon, Glut 4, glycoprotein 10b/IIIa (GP 10b/IIIa), GM-CSF, gp130, gp72, GRO, Growth hormone releasing factor, Hapten (NP-cap or NIP-cap), HB-EGF, HCC, HCMV gB envelope glycoprotein, HCMV) gH envelope glycoprotein, HCMV UL, Hemopoietic growth factor (HGF), Hep B gp120, heparanase, Her2, Her2/neu (ErbB-2), Her3 (ErbB-3), Her4 (ErbB-4), herpes simplex virus (HSV) gB glycoprotein, HSV gD glycoprotein, HGFA, High molecular weight melanoma-associated antigen (HMW-MAA), HIV gp120, HIV IIIB gp120 V3 loop, HLA, HLA-DR, HM1.24, HMFG PEM, HRG, Hrk, human cardiac myosin, human cytomegalovirus (HCMV), human growth hormone (HGH), HVEM, 1-309, IAP, ICAM, ICAM-1, ICAM-3, ICE, ICOS, IFNg, Ig, IgA receptor, IgE, IGF, IGF binding proteins, IGF-1R, IGFBP, IGF-I, IGF-II, IL, IL-1, IL-1R, IL-2, IL-2R, IL-4, IL-4R, IL-5, IL-5R, IL-6, IL-6R, IL-8, IL-9, IL-10, IL-12, IL-13, IL-15, IL-18, IL-18R, IL-23, interferon (INF)-alpha, INF-beta, INF-gamma, Inhibin, iNOS, Insulin A-chain, Insulin B-chain, Insulin-like growth factor 1, integrin alpha2, integrin alpha3, integrin alpha4, integrin alpha4/beta1, integrin alpha4/beta7, integrin alpha5 (alphaV), integrin alpha5/beta1, integrin alpha5/beta3, integrin alpha6, integrin beta1, integrin beta2, interferon gamma, IP-10, I-TAC, JE, Kallikrein 2, Kallikrein 5, Kallikrein 6, Kallikrein 11, Kallikrein 12, Kallikrein 14, Kallikrein 15, Kallikrein L1, Kallikrein L2, Kallikrein L3, Kallikrein L4, KC, KDR, Keratinocyte Growth Factor (KGF), laminin 5, LAMP, LAP, LAP (TGF-1), Latent TGF-1, Latent TGF-1 bpi, LBP, LDGF, LECT2, Lefty, Lewis-Y antigen, Lewis-Y related antigen, LFA-1, LFA-3, Lfo, LIF, LIGHT, lipoproteins, LIX, LKN, Lptn, L-Selectin, LT-a, LT-b, LTB4, LTBP-1, Lung surfactant, Luteinizing hormone, Lymphotoxin Beta Receptor, Mac-1, MAdCAM, MAG, MAP2, MARC, MCAM, MCAM, MCK-2, MCP, M-CSF, MDC, Mer, METALLOPROTEASES, MGDF receptor, MGMT, MHC (HLA-DR), MIF, MIG, MIP, MIP-1-alpha, MK, MMAC1, MMP, MMP-1, MMP-10, MMP-11, MMP-12, MMP-13, MMP-14, MMP-15, MMP-2, MMP-24, MMP-3, MMP-7, MMP-8, MMP-9, MPIF, Mpo, MSK, MSP, mucin (Mud), MUC18, Muellerian-inhibitin substance, Mug, MuSK, NAIP, NAP, NCAD, N-Cadherin, NCA 90, NCAM, NCAM, Neprilysin, Neurotrophin-3, -4, or -6, Neurturin, Neuronal growth factor (NGF), NGFR, NGF-beta, nNOS, NO, NOS, Npn, NRG-3, NT, NTN, OB, OGG1, OPG, OPN, OSM, OX40L, OX40R, p150, p95, PADPr, Parathyroid hormone, PARC, PARP, PBR, PBSF, PCAD, P-Cadherin, PCNA, PDGF, PDGF, PDK-1, PECAM, PEM, PF4, PGE, PGF, PGI2, PGJ2, PIN, PLA2, placental alkaline phosphatase (PLAP), P1 GF, PLP, PP14, Proinsulin, Prorelaxin, Protein C, PS, PSA, PSCA, prostate specific membrane antigen (PSMA), PTEN, PTHrp, Ptk, PTN, R51, RANK, RANKL, RANTES, RANTES, Relaxin A-chain, Relaxin B-chain, renin, respiratory syncytial virus (RSV) F, RSV Fgp, Ret, Rheumatoid factors, RLIP76, RPA2, RSK, S100, SCF/KL, SDF-1, SERINE, Serum albumin, sFRP-3, Shh, SIGIRR, SK-1, SLAM, SLPI, SMAC, SMDF, SMOH, SOD, SPARC, Stat, STEAP, STEAP-II, TACE, TACI, TAG-72 (tumor-associated glycoprotein-72), TARC, TCA-3, T-cell receptors (e.g., T-cell receptor alpha/beta), TdT, TECK, TEM1, TEM5, TEM7, TEM8, TERT, testicular PLAP-like alkaline phosphatase, TfR, TGF, TGF-alpha, TGF-beta, TGF-beta Pan Specific, TGF-beta RI (ALK-5), TGF-beta RII, TGF-beta RIIb, TGF-beta RIII, TGF-beta1, TGF-beta2, TGF-beta3, TGF-beta4, TGF-beta5, Thrombin, Thymus Ck-1, Thyroid stimulating hormone, Tie, TIMP, TIQ, Tissue Factor, TMEFF2, Tmpo, TMPRSS2, TNF, TNF-alpha, TNF-alpha beta, TNF-beta2, TNFc, TNF-RI, TNF-RII, TNFRSF10A (TRAIL R1 Apo-2, DR4), TNFRSF10B (TRAIL R2 DRS, KILLER, TRICK-2A, TRICK-B), TNFRSF10C (TRAIL R3 DcR1, LIT, TRID), TNFRSF10D (TRAIL R4 DcR2, TRUNDD), TNFRSF11A (RANK ODF R, TRANCE R), TNFRSF11B (OPG OCIF, TR1), TNFRSF12 (TWEAK R FN14), TNFRSF13B (TACI), TNFRSF13C (BAFF R), TNFRSF14 (HVEM ATAR, HveA, LIGHT R, TR2), TNFRSF16 (NGFR p75NTR), TNFRSF17 (BCMA), TNFRSF18 (GITR AITR), TNFRSF19 (TROY TAJ, TRADE), TNFRSF19L (RELT), TNFRSF1A (TNF RI CD120a, p55-60), TNFRSF1B (TNF RII CD120b, p75-80), TNFRSF26 (TNFRH3), TNFRSF3 (LTbR TNF RIII, TNFC R), TNFRSF4 (OX40 ACT35, TXGP1 R), TNFRSF5 (CD40 p50), TNFRSF6 (Fas Apo-1, APT1, CD95), TNFRSF6B (DcR3M68, TR6), TNFRSF7 (CD27), TNFRSF8 (CD30), TNFRSF9 (4-1 BB CD137, ILA), TNFRSF21 (DR6), TNFRSF22 (DcTRAIL R2 TNFRH2), TNFRST23 (DcTRAIL R1 TNFRH1), TNFRSF25 (DR3 Apo-3, LARD, TR-3, TRAMP, WSL-1), TNFSF10 (TRAIL Apo-2 Ligand, TL2), TNFSF11 (TRANCE/RANK Ligand ODF, OPG Ligand), TNFSF12 (TWEAK Apo-3 Ligand, DR3 Ligand), TNFSF13 (APRIL TALL2), TNFSF13B (BAFF BLYS, TALL1, THANK, TNFSF20), TNFSF14 (LIGHT HVEM Ligand, LTg), TNFSF15 (TL1A/VEGI), TNFSF18 (GITR Ligand AITR Ligand, TL6), TNFSF1A (TNF-a Conectin, DIF, TNFSF2), TNFSF1B (TNF-b LTa, TNFSF1), TNFSF3 (LTb TNFC, p33), TNFSF4 (OX40 Ligand gp34, TXGP1), TNFSF5 (CD40 Ligand CD154, gp39, HIGM1, IMD3, TRAP), TNFSF6 (Fas Ligand Apo-1 Ligand, APT1 Ligand), TNFSF7 (CD27 Ligand CD70), TNFSF8 (CD30 Ligand CD153), TNFSF9 (4-1BB Ligand CD137 Ligand), TP-1, t-PA, Tpo, TRAIL, TRAIL R, TRAIL-R1, TRAIL-R2, TRANCE, transferring receptor, TRF, Trk, TROP-2, TSG, TSLP, tumor-associated antigen CA 125, tumor-associated antigen expressing Lewis Y related carbohydrate, TWEAK, TXB2, Ung, uPAR, uPAR-1, Urokinase, VCAM, VCAM-1, VECAD, VE-Cadherin, VE-cadherin-2, VEFGR-1 (flt-1), VEGF, VEGFR, VEGFR-3 (flt-4), VEGI, VIM, Viral antigens, VLA, VLA-1, VLA-4, VNR integrin, von Willebrands factor, WI F-1, WNT1, WNT2, WNT2B/13, WNT3, WNT3A, WNT4, WNTSA, WNTSB, WNT6, WNT7A, WNT7B, WNT8A, WNT8B, WNT9A, WNT9A, WNT9B, WNT10A, WNT10B, WNT11, WNT16, XCL1, XCL2, XCR1, XCR1, XEDAR, XIAP, XPD, and receptors for hormones and growth factors.

[0138] As discussed below, target antigens that find use in the particular use of rapid clearance of antibody-antigen complexes are listed below, and include cancer antigens, autoantigens, pathogen antigens, allergy antigens, etc.

[0139] By “target cell” as used herein is meant a cell that expresses a target antigen.

[0140] By “variable region” as used herein is meant the region of an immunoglobulin that comprises one or more Ig domains substantially encoded by any of the Vκ, Vλ, and/or VH genes that make up the kappa, lambda, and heavy chain immunoglobulin genetic loci respectively.

[0141] By “variant polypeptide”, “polypeptide variant”, or “variant” as used herein is meant a polypeptide sequence that differs from that of a parent polypeptide sequence by virtue of at least one amino acid modification. The parent polypeptide may be a naturally occurring or wild-type (WT) polypeptide, or may be a modified version of a WT polypeptide. Variant polypeptide may refer to the polypeptide itself, a composition comprising the polypeptide, or the amino sequence that encodes it. In some embodiments, variant polypeptides disclosed herein (e.g., variant immunoglobulins) may have at least one amino acid modification compared to the parent polypeptide, e.g. from about one to about ten amino acid modifications, from about one to about five amino acid modifications, etc. compared to the parent. The variant polypeptide sequence herein may possess at least about 80% homology with a parent polypeptide sequence, e.g., at least about 90% homology, 95% homology, etc. Accordingly, by “Fc variant” or “variant Fc” as used herein is meant an Fc sequence that differs from that of a parent Fc sequence by virtue of at least one amino acid modification. An Fc variant may only encompass an Fc region, or may exist in the context of an antibody, Fc fusion, isolated Fc, Fc fragment, or other polypeptide that is substantially encoded by Fc. Fc variant may refer to the Fc polypeptide itself, compositions comprising the Fc variant polypeptide, or the amino acid sequence that encodes it. By “Fc polypeptide variant” or “variant Fc polypeptide” as used herein is meant an Fc polypeptide that differs from a parent Fc polypeptide by virtue of at least one amino acid modification. By “protein variant” or “variant protein” as used herein is meant a protein that differs from a parent protein by virtue of at least one amino acid modification. By “antibody variant” or “variant antibody” as used herein is meant an antibody that differs from a parent antibody by virtue of at least one amino acid modification. By “IgG variant” or “variant IgG” as used herein is meant an antibody that differs from a parent IgG by virtue of at least one amino acid modification. By “immunoglobulin variant” or “variant immunoglobulin” as used herein is meant an immunoglobulin sequence that differs from that of a parent immunoglobulin sequence by virtue of at least one amino acid modification.

[0142] By “wild type” or “WT” herein is meant an amino acid sequence or a nucleotide sequence that is found in nature, including allelic variations. A WT protein, polypeptide, antibody, immunoglobulin, IgG, etc. has an amino acid sequence or a nucleotide sequence that has not been intentionally modified.

[0143] The present invention is directed to the use of rapid clearance molecules (also referred to herein as “Ilb variants”) with high affinity to the FcγRIIb receptor that result in the rapid clearance from serum of the antibody-antigen complex, while retaining significant if not all the serum half-life of the unbound antigen or unbound rapid clearance molecules. In certain embodiments, the rapid clearance molecules of the invention include antibodies or Fc fusion proteins. Although much of the discussion herein is in terms of antibodies for ease of discussion, it will be appreciated that this discussion applies equally to any of the rapid clearance molecules described herein.

[0144] In general, rapid clearance molecules of the invention generally comprise a variable region that binds to an antigen and a variant Fc domain comprising one or more amino acid substitutions as compared to a parent Fc domain such that the variant Fc domain binds FcγRIIb with increased affinity as compared to the parent Fc domain.

[0145] In certain aspects, the rapid clearance (“RC”) antibodies incorporate FcγRIIb receptor variants that can range from very tight differential binding to FcγRIIb to variants that display increased (as compared to wild type Fc domains) binding affinity but at a lower level. For example, very tight (or heavy) binding to FcγRIIb receptor may include FcγRIIb variants that show at least 50, 75, 100, 125, 150, 175, 200, 225, 250-fold greater affinity to FcγRIIb receptor as compared to the parent Fc domain. In contrast, a lower level (or light, also referred to herein as “lite”) increase in binding may include FcγRIIb variants that show no more than 50, 40, 30, 20, 10, 5-fold greater affinity to FcγRIIb receptor as compared to the parent Fc domain. In further embodiments, tighter/heavier binding FcγRIIb variants show 50-300, 60-275, 70-250, 80-225, 90-200, 100-175, 110-150-fold greater affinity to FcγRIIb receptor as compared to the parent Fc domain, whereas lower/lighter binding FcγRIIb variants show 2-40, 4-35, 6-30, 8-25, 9-20, 10-15-fold greater affinity to FcγRIIb receptor as compared to the parent Fc domain. In certain embodiments, affinity is measured using Biacore, for example as described in Example 2. As discussed herein, the functional properties of rapid clearance molecules, including rapid clearance antibodies, can be tuned using modifications (such as amino acid substitutions, deletions or additions) that increase binding to FcγRIIb receptor by a tighter/heavier or a lower/lighter degree.

[0146] As shown herein, the binding affinity of the Ilb variants can be manipulated to result in different clearance/half life ratios. That is, the IIb variant S267E/L328F shows very high affinity binding to FcγRIIb of the variants discussed herein, and also has a faster clearance rate for antigen-antibody complexes among the variants discussed herein. The binding affinity, antibody half lives and clearance rates can be adjusted using high affinity binding variants or lower affinity binding variants, e.g. S267E, G236N/S267E, etc.). For example, the binding affinity of S267E is about 10× lower than the S267E/L328F variant, with a corresponding increase in half-life of roughly 2×-4× higher. In certain aspects, higher/heavier binding results in decreases in half-life. Thus, clearance rate and half-life can be adjusted by utilizing FcγRIIb-enhancing Fc amino acid substitutions that possess intermediate or lower increases in binding affinity (e.g., these substitutions still result in variants with higher affinity for FcγRIIb receptor than the parent molecules, but the affinities for these variants is not as increased, i.e., is lower/lighter than the heavy binding variants). Correlations between half-life and binding affinity can be measured as known in the art and discussed herein—see for example FIG. 25 and Example 6.

[0147] Application of different FcγRIIb-enhancing Fc amino acid substitutions with varying affinities to the FcγRIIb receptor (e.g. S267E/L328F, G236D/S267E, G236N/S267E, and S267E alone, as further described herein) can allow some “tuning” of how fast the complex antigen is cleared while maintaining significant half life of the rapid clearance composition of the invention (including antibodies). That is, different amino acid substitutions that alter FcγRIIb binding affinity may lead to different balances between the complex clearance rate and the antibody clearance rate, allowing for tailoring toward optimal therapeutic profile and dosing. This tuning may be accomplished by using amino acid substitutions in the Fc domain that increase binding to FcγRIIb as compared to the parent Fc domain. This increase in binding may be tuned by using Fc variants with 1-100, 5-90, 10-80, 15-70, 20-60, 30-50, 10-20, 5-15, fold greater affinity as compared to the parent Fc domain. This increase in binding may also be tuned by using Fc variants with 20-500, 30-400, 40-300, 50-200, 60-190, 70-180, 80-170, 90-160, 100-150, 110-140, 120-130, 50-100, 25-75 fold greater affinity to FcγRIIb receptor as compared to the parent Fc domain.

[0148] The effects of molecules of the invention may be further tuned by combining amino acid substitutions that alter FcγRIIb binding affinity with amino acid substitutions that affect binding to FcRn. Proteins with amino acid substitutions that affect binding to FcRn (also referred to herein as “FcRn variants”) may in certain situations also increase serum half-life in vivo as compared to the parent protein. As will be appreciated, any combination of Fc and FcRn variants may be used to tune clearance of the antigen-antibody complex. Suitable FcRn variants that may be combined with any of the Fc variants described herein that alter binding to FcγRIIb include without limitation 434A, 434S, 428L, 308F, 259I, 428L/434S, 259I/308F, 436I/428L, 436I/434S, 436V/434S, 436V/428L, 252Y, 252Y/254T/256E, and 259I/308F/428L.

[0149] In further embodiments, combinations of variants that alter binding to the FcγRIIb are combined with a variety of scaffolds, target antigens and/or FcRn variants to further tune clearance properties or other functional properties (such as binding to FcγRIIa) of the antibodies. Exemplary (non-limiting) combinations are provided in FIG. 48, which provides a matrix of possible combinations, with each variants being independently and optionally combined from the appropriate source Legend: Legend A are suitable FcRn variants: 434A, 434S, 428L, 308F, 259I, 428L/434S, 259I/308F, 436I/428L, 436I or V/434S, 436V/428L, 252Y, 252Y/254T/256E, 259I/308F/428L. Legend B are suitable scaffolds and include IgG1, IgG2, IgG3, IgG4, and IgG1/2. Legend C are suitable exemplary target antigens: IgE (soluble or membrane-bound), IL-4, IL-6, IL-13, TNFα, MCP-1, RANTES, TARC, MDC, VEGF, HGF, and NGF, immune complexes, FVIII inhibitors, LDL, oxidized LDL (OxLDL), Lp(a), SOST, and DKK1. Legend D reflects the following possible combinations, again, with each variant being independently and optionally combined from the appropriate source Legend: 1) FcγRIIb variants plus FcRn variants; 2) FcγRIIb variants plus FcRn variants plus Scaffold; 3) FcγRIIb variants plus FcRn variants plus Scaffold plus Fv; 4) FcγRIIb variants plus Scaffold 5) FcγRIIb variants plus Fv; 6) FcRn variants plus Scaffold; 7) FcRn variants plus Fv; 8) Scaffold plus Fv; 9) FcγRIIb variants plus Scaffold plus Fv; and 10) FcγRIIb variants plus FcRn variants plus Fv. Note that any of these combinations may also include any of the FcγRIIb variants described herein, including those listed in FIGS. 30, 36, 48 as well as those listed in the first column of FIG. 48. Any of these combinations may also include any Fc variants known in the art, including for example variants described in WO 2012/115241; WO2013/125667; U.S. Pat. No. 6,737,056; U.S. Pat. No. 8,435,517; and Mimoto et al., Protein Engineering Design and Selection, vol. 26, No. 10, pp. 589-598 (2013), each of which is hereby incorporated by reference in its entirety for all purposes, and in particular any figures, legends, or discussion related to variants that affect binding to Fcγ receptors, including the FcγRIIb receptor. The combinations described in FIG. 48 may further include selections from additional target antigens known in the art or described herein.

[0150] In still further embodiments and in accordance with any of the above, the rapid clearance molecules of the invention reduce the total concentration of free antigen in a patient as compared to the concentration prior to treatment with the rapid clearance molecule. In exemplary embodiments, methods and compositions of the invention reduce the total concentration of antigen by at least 2, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90-fold as compared to the concentration prior to treatment with the rapid clearance molecule.

[0151] In yet further embodiments and in accordance with any of the above, rapid clearance molecules include amino acid substitutions (including those described herein) that lead to Fc variants with increased FcγRIIb as compared to the parent Fc domain and further also alates binding to FcγRIIa. Such Fc variants may include the Fc variants described herein as well as Fc variants described herein combined with further substitutions that ablate binding to other FcγR, including without limitationFcγRIIa. As discussed above, “ablation” herein is meant a decrease or removal of activity. Thus for example, “ablating FcγR binding” means the Fc region amino acid variant has less than 50% starting binding as compared to an Fc region not containing the specific variant, with less than 70-80-90-95-98% loss of activity being preferred, and in general, with the activity being below the level of detectable binding in a Biacore assay.

[0152] In certain aspects and in accordance with any of the above, accelerated clearance of the antigen containing complexes seen with rapid clearance molecules containing amino acid substitutions that confer high affinity (as compared to the parent Fc domain) to the inhibitory receptor FcγRIIb is likely mediated by interaction with FcγRIIb-expressing cells, possibly liver sinusoidal endothelial cells. In certain embodiments, the accelerated clearance of the antigen containing molecules is not mediated by changes in pH or ionic conditions, such as those encountered within lysosomes.

[0153] In general, antibodies of the invention that have engineered Fc domains that result in higher affinity than wild-type antibodies to the FcγRIIb receptor can be directed to a variety of antigens as discussed herein, including cancer antigens, pathogen antigens, allergy antigens, etc.

[0154] In further embodiments, rapid clearance antibodies of the invention show functional properties as described in U.S. Provisional Application Ser. No. 61/752,955, filed Jan. 15, 2013; 61/794,164, filed Mar. 15, 2013, 61/794,386, filed Mar. 15, 2013, and 61/833,696, filed Jun. 11, 2013, each of which is expressly incorporated by reference in the entirety and in particular the figures describing such variants, their functional properties, or models of their functional properties (as shown for example in FIGS. 23-26 of U.S. Ser. No. 61/752,955).

[0155] The present invention relates to the generation of heterodimeric antibodies, generally therapeutic antibodies, through the use of “heterodimerization amino acid variants”. As is discussed below, the term “antibody” is used generally. Antibodies that find use in the present invention can take on a number of formats as described herein, including traditional antibodies as well as antibody derivatives, fragments and mimetics, described below. In general, the term “antibody” includes any polypeptide that includes at least one constant domain, including, but not limited to, CH1, CH2, CH3 and CL.

[0156] Traditional antibody structural units typically comprise a tetramer. Each tetramer is typically composed of two identical pairs of polypeptide chains, each pair having one “light” (typically having a molecular weight of about 25 kDa) and one “heavy” chain (typically having a molecular weight of about 50-70 kDa). Human light chains are classified as kappa and lambda light chains. The present invention is directed to the IgG class, which has several subclasses, including, but not limited to IgG1, IgG2, IgG3, and IgG4. Thus, “isotype” as used herein is meant any of the subclasses of immunoglobulins defined by the chemical and antigenic characteristics of their constant regions. It should be understood that therapeutic antibodies can also comprise hybrids of isotypes and/or subclasses. For example, as shown herein, the present invention covers heterodimers that can contain one or both chains that are IgG1/G2 hybrids (see SEQ ID NO:6, for example).

[0157] The amino-terminal portion of each chain includes a variable region of about 100 to 110 or more amino acids primarily responsible for antigen recognition, generally referred to in the art and herein as the “Fv domain” or “Fv region”. In the variable region, three loops are gathered for each of the V domains of the heavy chain and light chain to form an antigen-binding site. Each of the loops is referred to as a complementarity-determining region (hereinafter referred to as a “CDR”), in which the variation in the amino acid sequence is most significant. “Variable” refers to the fact that certain segments of the variable region differ extensively in sequence among antibodies. Variability within the variable region is not evenly distributed. Instead, the V regions consist of relatively invariant stretches called framework regions (FRs) of 15-30 amino acids separated by shorter regions of extreme variability called “hypervariable regions” that are each 9-15 amino acids long or longer.

[0158] Each VH and VL is composed of three hypervariable regions (“complementary determining regions,” “CDRs”) and four FRs, arranged from amino-terminus to carboxy-terminus in the following order: FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4.

[0159] The hypervariable region generally encompasses amino acid residues from about amino acid residues 24-34 (LCDR1; “L” denotes light chain), 50-56 (LCDR2) and 89-97 (LCDR3) in the light chain variable region and around about 31-35B (HCDR1; “H” denotes heavy chain), 50-65 (HCDR2), and 95-102 (HCDR3) in the heavy chain variable region; Kabat et al., SEQUENCES OF PROTEINS OF IMMUNOLOGICAL INTEREST, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991) and/or those residues forming a hypervariable loop (e.g. residues 26-32 (LCDR1), 50-52 (LCDR2) and 91-96 (LCDR3) in the light chain variable region and 26-32 (HCDR1), 53-55 (HCDR2) and 96-101 (HCDR3) in the heavy chain variable region; Chothia and Lesk (1987) J. Mol. Biol. 196:901-917. Specific CDRs of the invention are described below.

[0160] Throughout the present specification, the Kabat numbering system is generally used when referring to a residue in the variable domain (approximately, residues 1-107 of the light chain variable region and residues 1-113 of the heavy chain variable region) (e.g, Kabat et al., supra (1991)).

[0161] The CDRs contribute to the formation of the antigen-binding, or more specifically, epitope binding site of antibodies. “Epitope” refers to a determinant that interacts with a specific antigen binding site in the variable region of an antibody molecule known as a paratope. Epitopes are groupings of molecules such as amino acids or sugar side chains and usually have specific structural characteristics, as well as specific charge characteristics. A single antigen may have more than one epitope.

[0162] The epitope may comprise amino acid residues directly involved in the binding (also called immunodominant component of the epitope) and other amino acid residues, which are not directly involved in the binding, such as amino acid residues which are effectively blocked by the specifically antigen binding peptide; in other words, the amino acid residue is within the footprint of the specifically antigen binding peptide.

[0163] Epitopes may be either conformational or linear. A conformational epitope is produced by spatially juxtaposed amino acids from different segments of the linear polypeptide chain. A linear epitope is one produced by adjacent amino acid residues in a polypeptide chain. Conformational and nonconformational epitopes may be distinguished in that the binding to the former but not the latter is lost in the presence of denaturing solvents.

[0164] An epitope typically includes at least 3, and more usually, at least 5 or 8-10 amino acids in a unique spatial conformation. Antibodies that recognize the same epitope can be verified in a simple immunoassay showing the ability of one antibody to block the binding of another antibody to a target antigen, for example “binning.”

[0165] In some embodiments, the antibodies are full length. By “full length antibody” herein is meant the structure that constitutes the natural biological form of an antibody, including variable and constant regions, including one or more modifications as outlined herein.

[0166] Alternatively, the antibodies can be a variety of structures, including, but not limited to, antibody fragments, monoclonal antibodies, bispecific antibodies, minibodies, domain antibodies, synthetic antibodies (sometimes referred to herein as “antibody mimetics”), chimeric antibodies, humanized antibodies, antibody fusions (sometimes referred to as “antibody conjugates”), and fragments of each, respectively.

[0167] In one embodiment, the antibody is an antibody fragment. Of particular interest are antibodies that comprise Fc regions, Fc fusions, and the constant region of the heavy chain (CH1-hinge-CH2-CH3), again also including constant heavy region fusions.

[0168] Specific antibody fragments include, but are not limited to, (i) the Fab fragment consisting of VL, VH, CL and CH1 domains, (ii) the Fd fragment consisting of the VH and CH1 domains, (iii) the Fv fragment consisting of the VL and VH domains of a single antibody; (iv) the dAb fragment (Ward et al., 1989, Nature 341:544-546, entirely incorporated by reference) which consists of a single variable, (v) isolated CDR regions, (vi) F(ab′)2 fragments, a bivalent fragment comprising two linked Fab fragments (vii) single chain Fv molecules (scFv), wherein a VH domain and a VL domain are linked by a peptide linker which allows the two domains to associate to form an antigen binding site (Bird et al., 1988, Science 242:423-426, Huston et al., 1988, Proc. Natl. Acad. Sci. U.S.A. 85:5879-5883, entirely incorporated by reference), (viii) bispecific single chain Fv (WO 03/11161, hereby incorporated by reference) and (ix) “diabodies” or “triabodies”, multivalent or multispecific fragments constructed by gene fusion (Tomlinson et. al., 2000, Methods Enzymol. 326:461-479; WO94/13804; Holliger et al., 1993, Proc. Natl. Acad. Sci. U.S.A. 90:6444-6448, all entirely incorporated by reference). The antibody fragments may be modified. For example, the molecules may be stabilized by the incorporation of disulphide bridges linking the VH and VL domains (Reiter et al., 1996, Nature Biotech. 14:1239-1245, entirely incorporated by reference).

[0169] In some embodiments, the scaffold components can be a mixture from different species. As such, if the protein is an antibody, such antibody may be a chimeric antibody and/or a humanized antibody. In general, both “chimeric antibodies” and “humanized antibodies” refer to antibodies that combine regions from more than one species. For example, “chimeric antibodies” traditionally comprise variable region(s) from a mouse (or rat, in some cases) and the constant region(s) from a human. “Humanized antibodies” generally refer to non-human antibodies that have had the variable-domain framework regions swapped for sequences found in human antibodies. Generally, in a humanized antibody, the entire antibody, except the CDRs, is encoded by a polynucleotide of human origin or is identical to such an antibody except within its CDRs. The CDRs, some or all of which are encoded by nucleic acids originating in a non-human organism, are grafted into the beta-sheet framework of a human antibody variable region to create an antibody, the specificity of which is determined by the engrafted CDRs. The creation of such antibodies is described in, e.g., WO 92/11018, Jones, 1986, Nature 321:522-525, Verhoeyen et al., 1988, Science 239:1534-1536, all entirely incorporated by reference. “Backmutation” of selected acceptor framework residues to the corresponding donor residues is often required to regain affinity that is lost in the initial grafted construct (U.S. Pat. No. 5,530,101; U.S. Pat. No. 5,585,089; U.S. Pat. No. 5,693,761; U.S. Pat. No. 5,693,762; U.S. Pat. No. 6,180,370; U.S. Pat. No. 5,859,205; U.S. Pat. No. 5,821,337; U.S. Pat. No. 6,054,297; U.S. Pat. No. 6,407,213, all entirely incorporated by reference). The humanized antibody optimally also will comprise at least a portion of an immunoglobulin constant region, typically that of a human immunoglobulin, and thus will typically comprise a human Fc region. Humanized antibodies can also be generated using mice with a genetically engineered immune system. Roque et al., 2004, Biotechnol. Prog. 20:639-654, entirely incorporated by reference. A variety of techniques and methods for humanizing and reshaping non-human antibodies are well known in the art (See Tsurushita & Vasquez, 2004, Humanization of Monoclonal Antibodies, Molecular Biology of B Cells, 533-545, Elsevier Science (USA), and references cited therein, all entirely incorporated by reference). Humanization methods include but are not limited to methods described in Jones et al., 1986, Nature 321:522-525; Riechmann et al., 1988; Nature 332:323-329; Verhoeyen et al., 1988, Science, 239:1534-1536; Queen et al., 1989, Proc Natl Acad Sci, USA 86:10029-33; He et al., 1998, J. Immunol. 160: 1029-1035; Carter et al., 1992, Proc Natl Acad Sci USA 89:4285-9, Presta et al., 1997, Cancer Res. 57(20):4593-9; Gorman et al., 1991, Proc. Natl. Acad. Sci. USA 88:4181-4185; O'Connor et al., 1998, Protein Eng 11:321-8, all entirely incorporated by reference. Humanization or other methods of reducing the immunogenicity of nonhuman antibody variable regions may include resurfacing methods, as described for example in Roguska et al., 1994, Proc. Natl. Acad. Sci. USA 91:969-973, entirely incorporated by reference. In one embodiment, the parent antibody has been affinity matured, as is known in the art. Structure-based methods may be employed for humanization and affinity maturation, for example as described in U.S. Ser. No. 11/004,590. Selection based methods may be employed to humanize and/or affinity mature antibody variable regions, including but not limited to methods described in Wu et al., 1999, J. Mol. Biol. 294:151-162; Baca et al., 1997, J. Biol. Chem. 272(16):10678-10684; Rosok et al., 1996, J. Biol. Chem. 271(37): 22611-22618; Rader et al., 1998, Proc. Natl. Acad. Sci. USA 95: 8910-8915; Krauss et al., 2003, Protein Engineering 16(10):753-759, all entirely incorporated by reference. Other humanization methods may involve the grafting of only parts of the CDRs, including but not limited to methods described in U.S. Ser. No. 09/810,510; Tan et al., 2002, J. Immunol. 169:1119-1125; De Pascalis et al., 2002, J. Immunol. 169:3076-3084, all entirely incorporated by reference.

[0170] In one embodiment, the antibody is a minibody. Minibodies are minimized antibody-like proteins comprising a scFv joined to a CH3 domain. Hu et al., 1996, Cancer Res. 56:3055-3061, entirely incorporated by reference. In some cases, the scFv can be joined to the Fc region, and may include some or the entire hinge region.

[0171] In addition to antibody constructs discussed herein, the invention further provides Fc fusion proteins where the Fc region has IIb variants. That is, rather than have the Fc domain of an antibody joined to an antibody variable region, the Fc domain can be joined to other moieties, particularly binding moieties such as ligands. By “Fc fusion” as used herein is meant a protein wherein one or more polypeptides is operably linked to an Fc region. Fc fusion is herein meant to be synonymous with the terms “immunoadhesin”, “Ig fusion”, “Ig chimera”, and “receptor globulin” (sometimes with dashes) as used in the prior art (Chamow et al., 1996, Trends Biotechnol 14:52-60; Ashkenazi et al., 1997, Curr Opin Immunol 9:195-200, both entirely incorporated by reference). An Fc fusion combines the Fc region of an immunoglobulin with a fusion partner, which in general can be any protein or small molecule. Virtually any protein or small molecule may be linked to Fc to generate an Fc fusion. Protein fusion partners may include, but are not limited to, the variable region of any antibody, the target-binding region of a receptor, an adhesion molecule, a ligand, an enzyme, a cytokine, a chemokine, or some other protein or protein domain. Small molecule fusion partners may include any therapeutic agent that directs the Fc fusion to a therapeutic target. Such targets may be any molecule, preferably an extracellular receptor, which is implicated in disease. Thus, the IgG variants can be linked to one or more fusion partners.

[0172] The compositions and methods of the invention rely on FcγRIIb variants that increase binding to the FcγRIIb receptor. Related applications discuss the FcγRIIb variants in detail. See for example U.S. Ser. Nos. 11/124,620 and 13/294,103, both of which are incorporated by reference in their entirety, and in particular for the amino acid variant positions, accompanying specification description, figures and accompanying legends, and data relating to the variants. Fc variants that find particular use herein include, but are not limited to, those listed in FIG. 30.

[0173] FcγRIIb receptor variants that are considered “tight” binding and display the fastest rapid clearance times, include S267E/L328F.

[0174] FcγRIIb receptor variants increased binding as compared to wild type Fc domains, e.g. IgG1 domains, but are considered lower affinity and thus can result in longer half lives include, but are not limited to, S267E and G236N/267E and G236D/267E (sometimes referred to as “Ilb-lite” variants).

[0175] In addition to FcγRIIb receptor variants, there are a number of useful Fc substitutions that can be made to alter binding to one or more of the FcγR receptors. Substitutions that result in increased binding as well as decreased binding can be useful. For example, it is known that increased binding to FcγRIIIa generally results in increased ADCC (antibody dependent cell-mediated cytotoxicity; the cell-mediated reaction wherein nonspecific cytotoxic cells that express FcγRs recognize bound antibody on a target cell and subsequently cause lysis of the target cell. Amino acid substitutions that find use in the present invention include those listed in U.S. Ser. Nos. 11/124,620 (particularly FIG. 41), 11/174,287, 11/396,495, 11/538,406, all of which are expressly incorporated herein by reference in their entirety and specifically for the variants disclosed therein. Particular variants that find use include, but are not limited to, 236A, 239D, 239E, 332E, 332D, 239D/332E, 267D, S267E, L328F, S267E/L328F, 236A/332E, 239D/332E/330Y, 239D, 332E/330L, 243L, 298A and 299T. In some cases ablation variants such as 236R, 328R, and 236R/328R can be made, although this is not preferred in some embodiments. Additional suitable Fc variants are found in FIG. 41 of US 2006/0024298, the figure and legend of which are hereby incorporated by reference in their entirety.

[0176] In addition, there are additional Fc substitutions that find use in increased binding to the FcRn receptor and optionally increased serum half life, as specifically disclosed in U.S. Ser. No. 12/341,769, hereby incorporated by reference in its entirety, including, but not limited to, 434S, 434A, 428L, 308F, 259I, 428L/434S, 259I/308F, 436I/428L, 436I or V/434S, 436V/428L and 259I/308F/428L.

[0177] One example of rapid clearance applications are antibodies that contain an antigen binding site to IgE and FcγRIIb variants, resulting in “co-engagement”. For example, described herein are variant anti-IgE antibodies engineered such that the Fc domain binds to FcγRIIb with up to ˜430-fold greater affinity relative to native IgG1. These FcγRIIb binding-enhanced (IIbE) variants strongly inhibit BCR-induced calcium mobilization and viability in primary human IgE+ B cells. The use of a single molecule, such as an antibody to suppress B cell functions of cognate IgE BCR and FcγRIIb represents a novel approach in the treatment of IgE-mediated diseases. Non-limiting examples of IgE-mediated diseases include allergic responses and asthma and are described in U.S. Ser. No. 12/156,183, hereby incorporated by reference in its entirety, and particularly for the discussion associated with coengagement, and described below.

[0178] In one embodiment, the rapid clearance mechanisms of the present invention are used to treat hemophilia. One issue with hemophiliacs is the effect that Factor VIII (FVIII (not to be confused with “Fv”)) inhibitors play in disease. The most significant complication of treatment of hemophilia A is the development of alloantibodies to the therapeutic Factor VIII, that then inhibit the activity of the Factor VIII. Approximately 30% of patients with severe hemophilia A develop these alloantibodies, recognizing the exogenous correct FVIII as “foreign”, generally resulting in bleeding episodes that are more difficult to manage.

[0179] FIG. 28 shows the structure of the FVIIIa protein, consisting of heterodimeric protein comprising a heavy chain (A1-A2-B, not to be confused with the heavy chain of an antibody) and a light chain (A3-C1-C2) that are associated through a noncovalent divalent metal ion linkage between the A1 and A3 domains. The alloantibodies generally develop to the A2 and C2 domains, which are the dominant epitopes for the alloantibodies, generally accounting for roughly 68% of the alloantibody antigens.

[0180] Due to the rapid clearance of antibodies and Fc fusions engineered to bind with high affinity to FcγRIIb, the present invention provides “scrubber” or “drug” Fc fusions, comprising some or all of the domains of FVIIIa, that bind to the FVIIIa inhibitors thereby clearing out the alloantibodies. That is, the FcγRIIb fusions, directed against these inhibitor antibodies will sequester the inhibitor antibodies, rapidly clear the inhibitor antibodies, and will also inhibit FVIII-reactive B cells (to prohibit the further production of the inhibitors).

[0181] In one embodiment, the rapid clearance mechanisms of the present invention are used with complement receptor 2 (CR2)-Fc fusions for immune system modulation and accelerated clearance of C3d-tagged immune complexes. These fusion proteins in this context are sometimes referred to herein as “CR2-IIbE”. In this embodiment, increased affinity for the inhibitory Fc receptor FcRIIb (CD32b) is utilized to facilitate rapid in vivo clearance of C3-tagged immune complexes via their interaction with CR-IIbE fusions. Incorporation of the IIb-enhancing affinity substitutions into various fusions leads to a novel phenomenon whereby the fusion-target complex is cleared extremely rapidly while the CR-IIbE alone retains a reasonably long half-life. Application of different Ilb-enhancing substitutions (e.g. S267E/L328F, G236D/S267E, 236N/267E, or S267E alone, as are useful for all the rapid clearance molecules herein) may lead to different balances between the complex clearance rate and the fusion protein clearance rate, allowing for tailoring toward optimal therapeutic profile and dosing.

[0182] In another aspect of the invention, rapid clearance-mediating Ilb technology can additionally be applied to other complement system receptors or inhibitors, including but not limited to, CR1, Factor H (fH), CR3, and CRIg. Typically, only the SCR domains required for recognition of the appropriate complement factor will be required, although additional repeats may be included for stability.

[0183] In yet another aspect of the invention, rapid clearance-mediating Ilb technology can be applied to antibodies that recognize C3 fragments, thereby mimicking the above-described CR-Fc fusions, similar to the IgE and Factor VIII antibody examples. Examples include, but are not limited to, anti-C3d antibodies with engineered Fc regions. See also U.S. Ser. No. 61/752,955, filed Jan. 15, 2013, which is hereby incorporated by reference in its entirety for all purposes and in particular for all teachings, figures and legends related to schemes of complement and antibodies directed to same.

[0184] In some embodiments, the immunoglobulins described herein bind IgE. The anti-IgE antibodies of the invention may comprise any variable region, known or not yet known, that has specificity for IgE. Known anti-IgE antibodies include but are not limited to murine antibodies MaE11, MaE13, and MaE15, humanized and/or engineered versions of these antibodies including E25, E26, and E27, particularly E25, also known as rhuMab-E25, also known as Omalizumab, such as those described in U.S. Pat. No. 6,761,889, U.S. Pat. No. 6,329,509, US20080003218A1, and Presta, L G et al., 1993, J Immunol 151:2623-2632, all herein expressly incorporated by reference. A preferred engineered version of MaE11 is H1 L1 MaE11, described in the Examples herein. Other anti-IgE that may be useful for the invention include murine antibody TES-C21, chimeric TES-C21, also known as CGP51901 (Corne, J et al., 1997, J Clin Invest 99:879-887; Racine-Poon, A et al., 1997, Clin Pharmcol Ther 62:675-690), and humanized and/or engineered versions of this antibody including but not limited to CGP56901, also known as TNX-901, such as those antibodies described in Kolbinger, F et al., 1993, Protein Eng 6:971-980. Other anti-IgE antibodies that may find use for the invention are described in U.S. Pat. No. 6,066,718, U.S. Pat. No. 6,072,035, PCT/US04/02894, U.S. Pat. No. 5,342,924, U.S. Pat. No. 5,091,313, U.S. Pat. No. 5,449,760, U.S. Pat. No. 5,543,144, U.S. Pat. No. 5,342,924, and U.S. Pat. No. 5,614,611, all of which are incorporated herein by reference. Other useful anti-IgE antibodies include the murine antibody BSW17. Amino acid sequences of the variable region VH and VL domains and CDRs of some of these antibodies are provided in FIG. 5.

[0185] Immunoglobulins disclosed herein may comprise an Fc variant. An Fc variant comprises one or more amino acid modifications relative to a parent Fc polypeptide, wherein the amino acid modification(s) provide one or more optimized properties. An Fc variant disclosed herein differs in amino acid sequence from its parent by virtue of at least one amino acid modification. Thus Fc variants disclosed herein have at least one amino acid modification compared to the parent. Alternatively, the Fc variants disclosed herein may have more than one amino acid modification as compared to the parent, for example from about one to fifty amino acid modifications, e.g., from about one to ten amino acid modifications, from about one to about five amino acid modifications, etc. compared to the parent. Thus the sequences of the Fc variants and those of the parent Fc polypeptide are substantially homologous. For example, the variant Fc variant sequences herein will possess about 80% homology with the parent Fc variant sequence, e.g., at least about 90% homology, at least about 95% homology, at least about 98% homology, at least about 99% homology, etc. Modifications disclosed herein include amino acid modifications, including insertions, deletions, and substitutions. Modifications disclosed herein also include glycoform modifications. Modifications may be made genetically using molecular biology, or may be made enzymatically or chemically.

[0186] Fc variants disclosed herein are defined according to the amino acid modifications that compose them. Thus, for example, S267E is an Fc variant with the substitution S267E relative to the parent Fc polypeptide. Likewise, S267E/L328F defines an Fc variant with the substitutions S267E and L328F relative to the parent Fc polypeptide. The identity of the WT amino acid may be unspecified, in which case the aforementioned variant is referred to as S267E/L328F. It is noted that the order in which substitutions are provided is arbitrary, that is to say that, for example, S267E/L328F is the same Fc variant as L328F/267E, and so on. Unless otherwise noted, positions discussed herein are numbered according to the EU index or EU numbering scheme (Kabat et al., 1991, Sequences of Proteins of Immunological Interest, 5th Ed., United States Public Health Service, National Institutes of Health, Bethesda, hereby entirely incorporated by reference). The EU index or EU index as in Kabat or EU numbering scheme refers to the numbering of the EU antibody (Edelman et al., 1969, Proc Natl Acad Sci USA 63:78-85, hereby entirely incorporated by reference).

[0187] In certain embodiments, the Fc variants disclosed herein are based on human IgG sequences, and thus human IgG sequences are used as the “base” sequences against which other sequences are compared, including but not limited to sequences from other organisms, for example rodent and primate sequences. Immunoglobulins may also comprise sequences from other immunoglobulin classes such as IgA, IgE, IgGD, IgGM, and the like. It is contemplated that, although the Fc variants disclosed herein are engineered in the context of one parent IgG, the variants may be engineered in or “transferred” to the context of another, second parent IgG. This is done by determining the “equivalent” or “corresponding” residues and substitutions between the first and second IgG, typically based on sequence or structural homology between the sequences of the first and second IgGs. In order to establish homology, the amino acid sequence of a first IgG outlined herein is directly compared to the sequence of a second IgG. After aligning the sequences, using one or more of the homology alignment programs known in the art (for example using conserved residues as between species), allowing for necessary insertions and deletions in order to maintain alignment (i.e., avoiding the elimination of conserved residues through arbitrary deletion and insertion), the residues equivalent to particular amino acids in the primary sequence of the first immunoglobulin are defined. Alignment of conserved residues may conserve 100% of such residues. However, alignment of greater than 75% or as little as 50% of conserved residues is also adequate to define equivalent residues. Equivalent residues may also be defined by determining structural homology between a first and second IgG that is at the level of tertiary structure for IgGs whose structures have been determined. In this case, equivalent residues are defined as those for which the atomic coordinates of two or more of the main chain atoms of a particular amino acid residue of the parent or precursor (N on N, CA on CA, C on C and 0 on 0) are within about 0.13 nm, after alignment. In another embodiment, equivalent residues are within about 0.1 nm after alignment. Alignment is achieved after the best model has been oriented and positioned to give the maximum overlap of atomic coordinates of non-hydrogen protein atoms of the proteins. Regardless of how equivalent or corresponding residues are determined, and regardless of the identity of the parent IgG in which the IgGs are made, what is meant to be conveyed is that the Fc variants discovered as disclosed herein may be engineered into any second parent IgG that has significant sequence or structural homology with the Fc variant. Thus for example, if a variant antibody is generated wherein the parent antibody is human IgG1, by using the methods described above or other methods for determining equivalent residues, the variant antibody may be engineered in another IgG1 parent antibody that binds a different antigen, a human IgG2 parent antibody, a human IgA parent antibody, a mouse IgG2a or IgG2b parent antibody, and the like. Again, as described above, the context of the parent Fc variant does not affect the ability to transfer the Fc variants disclosed herein to other parent IgGs.

[0188] The Fc variants disclosed herein may be optimized for a variety of Fc receptor binding properties. An Fc variant that is engineered or predicted to display one or more optimized properties is herein referred to as an “optimized Fc variant”. Properties that may be optimized include but are not limited to enhanced or reduced affinity for an FcγR. In one embodiment, the Fc variants disclosed herein are optimized to possess enhanced affinity for an inhibitory receptor FcγRIIb. In other embodiments, immunoglobulins disclosed herein provide enhanced affinity for FcγRIIb, yet reduced affinity for one or more activating FcγRs, including for example FcγRI, FcγRIIa, FcγRIIIa, and/or FcγRIIIb. The FcγR receptors may be expressed on cells from any organism, including but not limited to human, cynomolgus monkeys, and mice. The Fc variants disclosed herein may be optimized to possess enhanced affinity for human FcγRIIb.

[0189] By “greater affinity” or “improved affinity” or “enhanced affinity” or “better affinity” than a parent Fc polypeptide, as used herein is meant that an Fc variant binds to an Fc receptor with a significantly higher equilibrium constant of association (KA or Ka) or lower equilibrium constant of dissociation (KD or Kd) than the parent Fc polypeptide when the amounts of variant and parent polypeptide in the binding assay are essentially the same. For example, the Fc variant with improved Fc receptor binding affinity may display from about 5 fold to about 1000 fold, e.g. from about 10 fold to about 500 fold improvement in Fc receptor binding affinity compared to the parent Fc polypeptide, where Fc receptor binding affinity is determined, for example, by the binding methods disclosed herein, including but not limited to Biacore, by one skilled in the art. Accordingly, by “reduced affinity” as compared to a parent Fc polypeptide as used herein is meant that an Fc variant binds an Fc receptor with significantly lower KA or higher KD than the parent Fc polypeptide. Greater or reduced affinity can also be defined relative to an absolute level of affinity. For example, according to the data herein, WT (native) IgG1 binds FcγRIIb with an affinity of about 2 μM, or about 2000 nM. Furthermore, some Fc variants described herein bind FcγRIIb with an affinity about 10-fold greater to WT IgG1. As disclosed herein, greater or enhanced affinity means having a KD lower than about 100 nM, for example between about 10 nM-about 100 nM, between about 1-about 100 nM, or less than about 1 nM.

[0190] Anti-IgE antibodies of the invention preferably have high affinity for FcγRIIb. By high affinity herein is meant that the affinity of the interaction between the antibody and FcγRIIb is stronger than 100 nM. That is to say that the equilibrium dissociation constant Kd for binding of the antibody to FcγRIIb is lower than 100 nM.

[0191] In one embodiment, the Fc variants provide selectively enhanced affinity to FcγRIIb relative to one or more activating receptors. Selectively enhanced affinity means either that the Fc variant has improved affinity for FcγRIIb relative to the activating receptor(s) as compared to the parent Fc polypeptide but has reduced affinity for the activating receptor(s) as compared to the parent Fc polypeptide, or it means that the Fc variant has improved affinity for both FcγRIIb and activating receptor(s) as compared to the parent Fc polypeptide, however the improvement in affinity is greater for FcγRIIb than it is for the activating receptor(s). In alternate embodiments, the Fc variants reduce or ablate binding to one or more activating FcγRs, reduce or ablate binding to one or more complement proteins, reduce or ablate one or more FcγR-mediated effector functions, and/or reduce or ablate one or more complement-mediated effector functions.

[0192] The presence of different polymorphic forms of FcγRs provides yet another parameter that impacts the therapeutic utility of the Fc variants disclosed herein. Whereas the specificity and selectivity of a given Fc variant for the different classes of FcγRs significantly affects the capacity of an Fc variant to target a given antigen for treatment of a given disease, the specificity or selectivity of an Fc variant for different polymorphic forms of these receptors may in part determine which research or pre-clinical experiments may be appropriate for testing, and ultimately which patient populations may or may not respond to treatment. Thus the specificity or selectivity of Fc variants disclosed herein to Fc receptor polymorphisms, including but not limited to FcγRIIa, FcγRIIIa, and the like, may be used to guide the selection of valid research and pre-clinical experiments, clinical trial design, patient selection, dosing dependence, and/or other aspects concerning clinical trials.

[0193] Fc variants disclosed herein may comprise modifications that modulate interaction with Fc receptors other than FcγRs, including but not limited to complement proteins, FcRn, and Fc receptor homologs (FcRHs). FcRHs include but are not limited to FcRH1, FcRH2, FcRH3, FcRH4, FcRH5, and FcRH6 (Davis et al., 2002, Immunol. Reviews 190:123-136).

[0194] An important parameter that determines the most beneficial selectivity of a given Fc variant to treat a given disease is the context of the Fc variant. Thus the Fc receptor selectivity or specificity of a given Fc variant will provide different properties depending on whether it composes an antibody, Fc fusion, or Fc variants with a coupled fusion partner. In one embodiment, an Fc receptor specificity of the Fc variant disclosed herein will determine its therapeutic utility. The utility of a given Fc variant for therapeutic purposes will depend on the epitope or form of the target antigen and the disease or indication being treated. For some targets and indications, greater FcγRIIb affinity and reduced activating FcγR-mediated effector functions may be beneficial. For other target antigens and therapeutic applications, it may be beneficial to increase affinity for FcγRIIb, or increase affinity for both FcγRIIb and activating receptors.

[0195] Many polypeptides, including antibodies, are subjected to a variety of posttranslational modifications involving carbohydrate moieties, such as glycosylation with oligosaccharides. There are several factors that can influence glycosylation. The species, tissue and cell type have all been shown to be important in the way that glycosylation occurs. In addition, the extracellular environment, through altered culture conditions such as serum concentration, may have a direct effect on glycosylation (Lifely et al., 1995, Glycobiology 5(8): 813-822).

[0196] All antibodies contain carbohydrate at conserved positions in the constant regions of the heavy chain. Each antibody isotype has a distinct variety of N-linked carbohydrate structures. Aside from the carbohydrate attached to the heavy chain, up to 30% of human IgGs have a glycosylated Fab region. IgG has a single N-linked biantennary carbohydrate at Asn297 of the CH2 domain. For IgG from either serum or produced ex vivo in hybridomas or engineered cells, the IgG are heterogeneous with respect to the Asn297 linked carbohydrate (Jefferis et al., 1998, Immunol. Rev. 163:59-76; Wright et al., 1997, Trends Biotech 15:26-32). For human IgG, the core oligosaccharide normally consists of GlcNAc2Man3GlcNAc, with differing numbers of outer residues.

[0197] The carbohydrate moieties of immunoglobulins disclosed herein will be described with reference to commonly used nomenclature for the description of oligosaccharides. A review of carbohydrate chemistry which uses this nomenclature is found in Hubbard et al. 1981, Ann. Rev. Biochem. 50:555-583. This nomenclature includes, for instance, Man, which represents mannose; GlcNAc, which represents 2-N-acetylglucosamine; Gal which represents galactose; Fuc for fucose; and Glc, which represents glucose. Sialic acids are described by the shorthand notation NeuNAc, for 5-N-acetylneuraminic acid, and NeuNGc for 5-glycolylneuraminic.

[0198] The term “glycosylation” means the attachment of oligosaccharides (carbohydrates containing two or more simple sugars linked together e.g. from two to about twelve simple sugars linked together) to a glycoprotein. The oligosaccharide side chains are typically linked to the backbone of the glycoprotein through either N- or O-linkages. The oligosaccharides of immunoglobulins disclosed herein occur generally are attached to a CH2 domain of an Fc region as N-linked oligosaccharides. “N-linked glycosylation” refers to the attachment of the carbohydrate moiety to an asparagine residue in a glycoprotein chain. The skilled artisan will recognize that, for example, each of murine IgG1, IgG2a, IgG2b and IgG3 as well as human IgG1, IgG2, IgG3, IgG4, IgA and IgD CH2 domains have a single site for N-linked glycosylation at amino acid residue 297 (Kabat et al. Sequences of Proteins of Immunological Interest, 1991).

[0199] For the purposes herein, a “mature core carbohydrate structure” refers to a processed core carbohydrate structure attached to an Fc region which generally consists of the following carbohydrate structure GlcNAc(Fucose)-GlcNAc-Man-(Man-GlcNAc)2 typical of biantennary oligosaccharides. The mature core carbohydrate structure is attached to the Fc region of the glycoprotein, generally via N-linkage to Asn297 of a CH2 domain of the Fc region. A “bisecting GlcNAc” is a GlcNAc residue attached to the β1,4 mannose of the mature core carbohydrate structure. The bisecting GlcNAc can be enzymatically attached to the mature core carbohydrate structure by a β(1,4)-N-acetylglucosaminyltransferase III enzyme (GnTIII). CHO cells do not normally express GnTIII (Stanley et al., 1984, J. Biol. Chem. 261:13370-13378), but may be engineered to do so (Umana et al., 1999, Nature Biotech. 17:176-180).

[0200] Described herein are Fc variants that comprise modified glycoforms or engineered glycoforms. By “modified glycoform” or “engineered glycoform” as used herein is meant a carbohydrate composition that is covalently attached to a protein, for example an antibody, wherein said carbohydrate composition differs chemically from that of a parent protein. Engineered glycoforms may be useful for a variety of purposes, including but not limited to enhancing or reducing FcγR-mediated effector function. In one embodiment, the immunoglobulins disclosed herein are modified to control the level of fucosylated and/or bisecting oligosaccharides that are covalently attached to the Fc region.

[0201] A variety of methods are well known in the art for generating modified glycoforms (Umana et al., 1999, Nat Biotechnol 17:176-180; Davies et al., 2001, Biotechnol Bioeng 74:288-294; Shields et al., 2002, J Biol Chem 277:26733-26740; Shinkawa et al., 2003, J Biol Chem 278:3466-3473); (U.S. Pat. No. 6,602,684; U.S. Ser. No. 10/277,370; U.S. Ser. No. 10/113,929; PCT WO 00/61739A1; PCT WO 01/29246A1; PCT WO 02/31140A1; PCT WO 02/30954A1); (Potelligent™ technology [Biowa, Inc., Princeton, N.J.]; GlycoMAb™ glycosylation engineering technology [GLYCART biotechnology AG, Zurich, Switzerland]; all of which are expressly incorporated by reference). These techniques control the level of fucosylated and/or bisecting oligosaccharides that are covalently attached to the Fc region, for example by expressing an IgG in various organisms or cell lines, engineered or otherwise (for example Lec-13 CHO cells or rat hybridoma YB2/0 cells), by regulating enzymes involved in the glycosylation pathway (for example FUT8 [α1,6-fucosyltranserase]and/or β1-4-N-acetylglucosaminyltransferase III [GnTIII]), or by modifying carbohydrate(s) after the IgG has been expressed. Other methods for modifying glycoforms of the immunoglobulins disclosed herein include using glycoengineered strains of yeast (Li et al., 2006, Nature Biotechnology 24(2):210-215), moss (Nechansky et al., 2007, Mol Immunjol 44(7):1826-8), and plants (Cox et al., 2006, Nat Biotechnol 24(12):1591-7). The use of a particular method to generate a modified glycoform is not meant to constrain embodiments to that method. Rather, embodiments disclosed herein encompass Fc variants with modified glycoforms irrespective of how they are produced.

[0202] In one embodiment, immunoglobulins disclosed herein are glycoengineered to alter the level of sialylation. Higher levels of sialylated Fc glycans in immunoglobulin G molecules can adversely impact functionality (Scallon et al., 2007, Mol Immunol. 44(7):1524-34), and differences in levels of Fc sialylation can result in modified anti-inflammatory activity (Kaneko et al., 2006, Science 313:670-673). Because antibodies may acquire anti-inflammatory properties upon sialylation of Fc core polysaccharide, it may be advantageous to glycoengineer the immunoglobulins disclosed herein for greater or reduced Fc sialic acid content.

[0203] Engineered glycoform typically refers to the different carbohydrate or oligosaccharide; thus for example an immunoglobulin may comprise an engineered glycoform. Alternatively, engineered glycoform may refer to the immunoglobulin that comprises the different carbohydrate or oligosaccharide. In one embodiment, a composition disclosed herein comprises a glycosylated Fc variant having an Fc region, wherein about 51-100% of the glycosylated antibody, e.g., 80-100%, 90-100%, 95-100%, etc. of the antibody in the composition comprises a mature core carbohydrate structure which lacks fucose. In another embodiment, the antibody in the composition both comprises a mature core carbohydrate structure that lacks fucose and additionally comprises at least one amino acid modification in the Fc region. In an alternative embodiment, a composition comprises a glycosylated Fc variant having an Fc region, wherein about 51-100% of the glycosylated antibody, 80-100%, or 90-100%, of the antibody in the composition comprises a mature core carbohydrate structure which lacks sialic acid. In another embodiment, the antibody in the composition both comprises a mature core carbohydrate structure that lacks sialic acid and additionally comprises at least one amino acid modification in the Fc region. In yet another embodiment, a composition comprises a glycosylated Fc variant having an Fc region, wherein about 51-100% of the glycosylated antibody, 80-100%, or 90-100%, of the antibody in the composition comprises a mature core carbohydrate structure which contains sialic acid. In another embodiment, the antibody in the composition both comprises a mature core carbohydrate structure that contains sialic acid and additionally comprises at least one amino acid modification in the Fc region. In another embodiment, the combination of engineered glycoform and amino acid modification provides optimal Fc receptor binding properties to the antibody.

[0204] Immunoglobulins disclosed herein may comprise one or more modifications that provide optimized properties that are not specifically related to FcγR- or complement-mediated effector functions per se. Said modifications may be amino acid modifications, or may be modifications that are made enzymatically or chemically. Such modification(s) likely provide some improvement in the immunoglobulin, for example an enhancement in its stability, solubility, function, or clinical use. Disclosed herein are a variety of improvements that may be made by coupling the immunoglobulins disclosed herein with additional modifications.

[0205] In one embodiment, the variable region of an antibody disclosed herein may be affinity matured, that is to say that amino acid modifications have been made in the VH and/or VL domains of the antibody to enhance binding of the antibody to its target antigen. Such types of modifications may improve the association and/or the dissociation kinetics for binding to the target antigen. Other modifications include those that improve selectivity for target antigen vs. alternative targets. These include modifications that improve selectivity for antigen expressed on target vs. non-target cells. Other improvements to the target recognition properties may be provided by additional modifications. Such properties may include, but are not limited to, specific kinetic properties (i.e. association and dissociation kinetics), selectivity for the particular target versus alternative targets, and selectivity for a specific form of target versus alternative forms. Examples include full-length versus splice variants, cell-surface vs. soluble forms, selectivity for various polymorphic variants, or selectivity for specific conformational forms of the target antigen. Immunoglobulins disclosed herein may comprise one or more modifications that provide reduced or enhanced internalization of an immunoglobulin.

[0206] In one embodiment, modifications are made to improve biophysical properties of the immunoglobulins disclosed herein, including but not limited to stability, solubility, and oligomeric state. Modifications can include, for example, substitutions that provide more favorable intramolecular interactions in the immunoglobulin such as to provide greater stability, or substitution of exposed nonpolar amino acids with polar amino acids for higher solubility. Other modifications to the immunoglobulins disclosed herein include those that enable the specific formation or homodimeric or homomultimeric molecules. Such modifications include but are not limited to engineered disulfides, as well as chemical modifications or aggregation methods which may provide a mechanism for generating covalent homodimeric or homomultimers. Additional modifications to the variants disclosed herein include those that enable the specific formation or heterodimeric, heteromultimeric, bifunctional, and/or multifunctional molecules. Such modifications include, but are not limited to, one or more amino acid substitutions in the CH3 domain, in which the substitutions reduce homodimer formation and increase heterodimer formation. Additional modifications include modifications in the hinge and CH3 domains, in which the modifications reduce the propensity to form dimers.

[0207] In further embodiments, the immunoglobulins disclosed herein comprise modifications that remove proteolytic degradation sites. These may include, for example, protease sites that reduce production yields, as well as protease sites that degrade the administered protein in vivo. In one embodiment, additional modifications are made to remove covalent degradation sites such as deamidation (i.e. deamidation of glutaminyl and asparaginyl residues to the corresponding glutamyl and aspartyl residues), oxidation, and proteolytic degradation sites. Deamidation sites that are particular useful to remove are those that have enhance propensity for deamidation, including, but not limited to asparaginyl and glutamyl residues followed by glycines (NG and QG motifs, respectively). In such cases, substitution of either residue can significantly reduce the tendency for deamidation. Common oxidation sites include methionine and cysteine residues. Other covalent modifications, that can either be introduced or removed, include hydroxylation of proline and lysine, phosphorylation of hydroxyl groups of seryl or threonyl residues, methylation of the “-amino groups of lysine, arginine, and histidine side chains (T. E. Creighton, Proteins: Structure and Molecular Properties, W.H. Freeman & Co., San Francisco, pp. 79-86 (1983), incorporated entirely by reference), acetylation of the N-terminal amine, and amidation of any C-terminal carboxyl group. Additional modifications also may include but are not limited to posttranslational modifications such as N-linked or O-linked glycosylation and phosphorylation.

[0208] Modifications may include those that improve expression and/or purification yields from hosts or host cells commonly used for production of biologics. These include, but are not limited to various mammalian cell lines (e.g. CHO), yeast cell lines, bacterial cell lines, and plants. Additional modifications include modifications that remove or reduce the ability of heavy chains to form inter-chain disulfide linkages. Additional modifications include modifications that remove or reduce the ability of heavy chains to form intra-chain disulfide linkages.

[0209] The immunoglobulins disclosed herein may comprise modifications that include the use of unnatural amino acids incorporated using, for example, the technologies developed by Schultz and colleagues, including but not limited to methods described by Cropp & Shultz, 2004, Trends Genet. 20(12):625-30, Anderson et al., 2004, Proc. Natl. Acad. Sci. U.S.A. 101(2):7566-71, Zhang et al., 2003, 303(5656):371-3, and Chin et al., 2003, Science 301(5635):964-7, all incorporated entirely by reference. In some embodiments, these modifications enable manipulation of various functional, biophysical, immunological, or manufacturing properties discussed above. In additional embodiments, these modifications enable additional chemical modification for other purposes. Other modifications are contemplated herein. For example, the immunoglobulin may be linked to one of a variety of nonproteinaceous polymers, e.g., polyethylene glycol (PEG), polypropylene glycol, polyoxyalkylenes, or copolymers of polyethylene glycol and polypropylene glycol. Additional amino acid modifications may be made to enable specific or non-specific chemical or posttranslational modification of the immunoglobulins. Such modifications, include, but are not limited to PEGylation and glycosylation. Specific substitutions that can be utilized to enable PEGylation include, but are not limited to, introduction of novel cysteine residues or unnatural amino acids such that efficient and specific coupling chemistries can be used to attach a PEG or otherwise polymeric moiety. Introduction of specific glycosylation sites can be achieved by introducing novel N-X-T/S sequences into the immunoglobulins disclosed herein.

[0210] Modifications to reduce immunogenicity may include modifications that reduce binding of processed peptides derived from the parent sequence to MHC proteins. For example, amino acid modifications would be engineered such that there are no or a minimal number of immune epitopes that are predicted to bind, with high affinity, to any prevalent MHC alleles. Several methods of identifying MHC-binding epitopes in protein sequences are known in the art and may be used to score epitopes in an antibody disclosed herein. See for example U.S. Ser. No. 09/903,378, U.S. Ser. No. 10/754,296, U.S. Ser. No. 11/249,692, and references cited therein, all expressly incorporated by reference.

[0211] In some embodiments, immunoglobulins disclosed herein may be combined with immunoglobulins that alter FcRn binding. Such variants may provide improved pharmacokinetic properties to the immunoglobulins. Preferred variants that increase binding to FcRn and/or improve pharmacokinetic properties include but are not limited to substitutions at positions 259, 308, 428, and 434, including but not limited to for example 259I, 308F, 428L, 428M, 434S, 434H, 434F, 434Y, and 434M (PCT/US2008/088053, filed Dec. 22, 2008, entitled “Fc Variants with Altered Binding to FcRn”, entirely incorporated by reference). Other variants that increase Fc binding to FcRn include but are not limited to: 250E, 250Q, 428L, 428F, 250Q/428L (Hinton et al., 2004, J. Biol. Chem. 279(8): 6213-6216, Hinton et al. 2006 Journal of Immunology 176:346-356), 256A, 272A, 286A, 305A, 307A, 311A, 312A, 376A, 378Q, 380A, 382A, 434A (Shields et al, Journal of Biological Chemistry, 2001, 276(9):6591-6604, entirely incorporated by reference), 252F, 252T, 252Y, 252W, 254T, 256S, 256R, 256Q, 256E, 256D, 256T, 309P, 311S, 433R, 433S, 433I, 433P, 433Q, 434H, 434F, 434Y, 252Y/254T/256E, 433K/434F/436H, 308T/309P/311 S (Dall Acqua et al. Journal of Immunology, 2002, 169:5171-5180, Dall'Acqua et al., 2006, The Journal of biological chemistry 281:23514-23524, entirely incorporated by reference).

[0212] Covalent modifications of antibodies are included within the scope of immunoglobulins disclosed herein, and are generally, but not always, done post-translationally. For example, several types of covalent modifications of the antibody are introduced into the molecule by reacting specific amino acid residues of the antibody with an organic derivatizing agent that is capable of reacting with selected side chains or the N- or C-terminal residues.

[0213] In some embodiments, the covalent modification of the antibodies disclosed herein comprises the addition of one or more labels. The term “labeling group” means any detectable label. In some embodiments, the labeling group is coupled to the antibody via spacer arms of various lengths to reduce potential steric hindrance. Various methods for labeling proteins are known in the art and may be used in generating immunoglobulins disclosed herein.

[0214] In some embodiments, the multispecific antibodies of the invention are conjugated with drugs to form antibody-drug conjugates (ADCs). In general, ADCs are used in oncology applications, where the use of antibody-drug conjugates for the local delivery of cytotoxic or cytostatic agents allows for the targeted delivery of the drug moiety to tumors, which can allow higher efficacy, lower toxicity, etc. An overview of this technology is provided in Ducry et al., Bioconjugate Chem., 21:5-13 (2010), Carter et al., Cancer J. 14(3):154 (2008) and Senter, Current Opin. Chem. Biol. 13:235-244 (2009), all of which are hereby incorporated by reference in their entirety.

[0215] Thus the invention provides multispecific antibodies conjugated to drugs. Generally, conjugation is done by covalent attachment to the antibody, as further described below, and generally relies on a linker, often a peptide linkage (which, as described below, may be designed to be sensitive to cleavage by proteases at the target site or not). In addition, as described above, linkage of the linker-drug unit (LU-D) can be done by attachment to cysteines within the antibody. As will be appreciated by those in the art, the number of drug moieties per antibody can change, depending on the conditions of the reaction, and can vary from 1:1 to 10:1 drug:antibody. As will be appreciated by those in the art, the actual number is an average.

[0216] Thus the invention provides multispecific antibodies conjugated to drugs. As described below, the drug of the ADC can be any number of agents, including but not limited to cytotoxic agents such as chemotherapeutic agents, growth inhibitory agents, toxins (for example, an enzymatically active toxin of bacterial, fungal, plant, or animal origin, or fragments thereof), or a radioactive isotope (that is, a radioconjugate) are provided. In other embodiments, the invention further provides methods of using the ADCs.

[0217] Drugs for use in the present invention include cytotoxic drugs, particularly those which are used for cancer therapy. Such drugs include, in general, DNA damaging agents, anti-metabolites, natural products and their analogs. Exemplary classes of cytotoxic agents include the enzyme inhibitors such as dihydrofolate reductase inhibitors, and thymidylate synthase inhibitors, DNA intercalators, DNA cleavers, topoisomerase inhibitors, the anthracycline family of drugs, the vinca drugs, the mitomycins, the bleomycins, the cytotoxic nucleosides, the pteridine family of drugs, diynenes, the podophyllotoxins, dolastatins, maytansinoids, differentiation inducers, and taxols.

[0218] Members of these classes include, for example, methotrexate, methopterin, dichloromethotrexate, 5-fluorouracil, 6-mercaptopurine, cytosine arabinoside, melphalan, leurosine, leurosideine, actinomycin, daunorubicin, doxorubicin, mitomycin C, mitomycin A, caminomycin, aminopterin, tallysomycin, podophyllotoxin and podophyllotoxin derivatives such as etoposide or etoposide phosphate, vinblastine, vincristine, vindesine, taxanes including taxol, taxotere retinoic acid, butyric acid, N8-acetyl spermidine, camptothecin, calicheamicin, esperamicin, ene-diynes, duocarmycin A, duocarmycin SA, calicheamicin, camptothecin, maytansinoids (including DM1), monomethylauristatin E (MMAE), monomethylauristatin F (MMAF), and maytansinoids (DM4) and their analogues.

[0219] Toxins may be used as antibody-toxin conjugates and include bacterial toxins such as diphtheria toxin, plant toxins such as ricin, small molecule toxins such as geldanamycin (Mandler et al (2000) J. Nat. Cancer Inst. 92(19):1573-1581; Mandler et al (2000) Bioorganic & Med. Chem. Letters 10:1025-1028; Mandler et al (2002) Bioconjugate Chem. 13:786-791), maytansinoids (EP 1391213; Liu et al., (1996) Proc. Natl. Acad. Sci. USA 93:8618-8623), and calicheamicin (Lode et al (1998) Cancer Res. 58:2928; Hinman et al (1993) Cancer Res. 53:3336-3342). Toxins may exert their cytotoxic and cytostatic effects by mechanisms including tubulin binding, DNA binding, or topoisomerase inhibition.

[0220] Conjugates of a multispecific antibody and one or more small molecule toxins, such as a maytansinoids, dolastatins, auristatins, a trichothecene, calicheamicin, and CC1065, and the derivatives of these toxins that have toxin activity, are contemplated.

[0221] Maytansine compounds suitable for use as maytansinoid drug moieties are well known in the art, and can be isolated from natural sources according to known methods, produced using genetic engineering techniques (see Yu et al (2002) PNAS 99:7968-7973), or maytansinol and maytansinol analogues prepared synthetically according to known methods. As described below, drugs may be modified by the incorporation of a functionally active group such as a thiol or amine group for conjugation to the antibody.

[0222] Exemplary maytansinoid drug moieties include those having a modified aromatic ring, such as: C-19-dechloro (U.S. Pat. No. 4,256,746) (prepared by lithium aluminum hydride reduction of ansamytocin P2); C-20-hydroxy (or C-20-demethyl) +/−C-19-dechloro (U.S. Pat. Nos. 4,361,650 and 4,307,016) (prepared by demethylation using Streptomyces or Actinomyces or dechlorination using LAH); and C-20-demethoxy, C-20-acyloxy (—OCOR), +/−dechloro (U.S. Pat. No. 4,294,757) (prepared by acylation using acyl chlorides) and those having modifications at other positions

[0223] Exemplary maytansinoid drug moieties also include those having modifications such as: C-9-SH (U.S. Pat. No. 4,424,219) (prepared by the reaction of maytansinol with H2S or P2S5); C-14-alkoxymethyl(demethoxy/CH2OR) (U.S. Pat. No. 4,331,598); C-14-hydroxymethyl or acyloxymethyl (CH2OH or CH2OAc) (U.S. Pat. No. 4,450,254) (prepared from Nocardia); C-15-hydroxy/acyloxy (U.S. Pat. No. 4,364,866) (prepared by the conversion of maytansinol by Streptomyces); C-15-methoxy (U.S. Pat. Nos. 4,313,946 and 4,315,929) (isolated from Trewia nudlflora); C-18-N-demethyl (U.S. Pat. Nos. 4,362,663 and 4,322,348) (prepared by the demethylation of maytansinol by Streptomyces); and 4,5-deoxy (U.S. Pat. No. 4,371,533) (prepared by the titanium trichloride/LAH reduction of maytansinol).

[0224] Of particular use are DM1 (disclosed in U.S. Pat. No. 5,208,020, incorporated by reference) and DM4 (disclosed in U.S. Pat. No. 7,276,497, incorporated by reference). See also a number of additional maytansinoid derivatives and methods in 5,416,064, WO/01/24763, 7,303,749, 7,601,354, U.S. Ser. No. 12/631,508, WO02/098883, 6,441,163, 7,368,565, WO02/16368 and WO04/1033272, all of which are expressly incorporated by reference in their entirety.

[0225] ADCs containing maytansinoids, methods of making same, and their therapeutic use are disclosed, for example, in U.S. Pat. Nos. 5,208,020; 5,416,064; 6,441,163 and European Patent EP 0 425 235 B1, the disclosures of which are hereby expressly incorporated by reference. Liu et al., Proc. Natl. Acad. Sci. USA 93:8618-8623 (1996) described ADCs comprising a maytansinoid designated DM1 linked to the monoclonal antibody C242 directed against human colorectal cancer. The conjugate was found to be highly cytotoxic towards cultured colon cancer cells, and showed antitumor activity in an in vivo tumor growth assay.

[0226] Chari et al., Cancer Research 52:127-131 (1992) describe ADCs in which a maytansinoid was conjugated via a disulfide linker to the murine antibody A7 binding to an antigen on human colon cancer cell lines, or to another murine monoclonal antibody TA.1 that binds the HER-2/neu oncogene. The cytotoxicity of the TA.1-maytansonoid conjugate was tested in vitro on the human breast cancer cell line SK-BR-3, which expresses 3×105 HER-2 surface antigens per cell. The drug conjugate achieved a degree of cytotoxicity similar to the free maytansinoid drug, which could be increased by increasing the number of maytansinoid molecules per antibody molecule. The A7-maytansinoid conjugate showed low systemic cytotoxicity in mice.

[0227] In some embodiments, the ADC comprises a multispecific antibody conjugated to dolastatins or dolostatin peptidic analogs and derivatives, the auristatins (U.S. Pat. Nos. 5,635,483; 5,780,588). Dolastatins and auristatins have been shown to interfere with microtubule dynamics, GTP hydrolysis, and nuclear and cellular division (Woyke et al (2001) Antimicrob. Agents and Chemother. 45(12):3580-3584) and have anticancer (U.S. Pat. No. 5,663,149) and antifungal activity (Pettit et al (1998) Antimicrob. Agents Chemother. 42:2961-2965). The dolastatin or auristatin drug moiety may be attached to the antibody through the N (amino) terminus or the C (carboxyl) terminus of the peptidic drug moiety (WO 02/088172).

[0228] Exemplary auristatin embodiments include the N-terminus linked monomethylauristatin drug moieties DE and DF, disclosed in “Senter et al, Proceedings of the American Association for Cancer Research, Volume 45, Abstract Number 623, presented Mar. 28, 2004 and described in United States Patent Publication No. 2005/0238648, the disclosure of which is expressly incorporated by reference in its entirety.

[0229] An exemplary auristatin embodiment is MMAE (see U.S. Pat. No. 6,884,869 expressly incorporated by reference in its entirety).

[0230] Another exemplary auristatin embodiment is MMAF (see US 2005/0238649, 5,767,237 and 6,124,431, expressly incorporated by reference in their entirety).

[0231] Additional exemplary embodiments comprising MMAE or MMAF and various linker components (described further herein) have the following structures and abbreviations (wherein Ab means antibody and p is 1 to about 8):

[0232] Typically, peptide-based drug moieties can be prepared by forming a peptide bond between two or more amino acids and/or peptide fragments. Such peptide bonds can be prepared, for example, according to the liquid phase synthesis method (see E. Schroder and K. Lubke, “The Peptides”, volume 1, pp 76-136, 1965, Academic Press) that is well known in the field of peptide chemistry. The auristatin/dolastatin drug moieties may be prepared according to the methods of: U.S. Pat. No. 5,635,483; U.S. Pat. No. 5,780,588; Pettit et al (1989) J. Am. Chem. Soc. 111:5463-5465; Pettit et al (1998) Anti-Cancer Drug Design 13:243-277; Pettit, G. R., et al. Synthesis, 1996, 719-725; Pettit et al (1996) J. Chem. Soc. Perkin Trans. 1 5:859-863; and Doronina (2003) Nat Biotechnol 21(7):778-784.

[0233] In other embodiments, the ADC comprises an antibody of the invention conjugated to one or more calicheamicin molecules. For example, Mylotarg is the first commercial ADC drug and utilizes calicheamicin γ1 as the payload (see U.S. Pat. No. 4,970,198, incorporated by reference in its entirety). Additional calicheamicin derivatives are described in U.S. Pat. Nos. 5,264,586, 5,384,412, 5,550,246, 5,739,116, 5,773,001, 5,767,285 and 5,877,296, all expressly incorporated by reference. The calicheamicin family of antibiotics are capable of producing double-stranded DNA breaks at sub-picomolar concentrations. For the preparation of conjugates of the calicheamicin family, see U.S. Pat. Nos. 5,712,374, 5,714,586, 5,739,116, 5,767,285, 5,770,701, 5,770,710, 5,773,001, 5,877,296 (all to American Cyanamid Company). Structural analogues of calicheamicin which may be used include, but are not limited to, γ1I, α2I, α2I, N-acetyl-γ1I, PSAG and θI1 (Hinman et al., Cancer Research 53:3336-3342 (1993), Lode et al., Cancer Research 58:2925-2928 (1998) and the aforementioned U.S. patents to American Cyanamid). Another anti-tumor drug that the antibody can be conjugated is QFA which is an antifolate. Both calicheamicin and QFA have intracellular sites of action and do not readily cross the plasma membrane. Therefore, cellular uptake of these agents through antibody mediated internalization greatly enhances their cytotoxic effects.

[0234] CC-1065 (see U.S. Pat. No. 4,169,888, incorporated by reference) and duocarmycins are members of a family of antitumor antibiotics utilized in ADCs. These antibiotics appear to work through sequence-selectively alkylating DNA at the N3 of adenine in the minor groove, which initiates a cascade of events that result in apoptosis.

[0235] Important members of the duocarmycins include duocarmycin A (U.S. Pat. No. 4,923,990, incorporated by reference) and duocarmycin SA (U.S. Pat. No. 5,101,038, incorporated by reference), and a large number of analogues as described in U.S. Pat. Nos. 7,517,903, 7,691,962, 5,101,038; 5,641,780; 5,187,186; 5,070,092; 5,070,092; 5,641,780; 5,101,038; 5,084,468, 5,475,092, 5,585,499, 5,846,545, WO2007/089149, WO2009/017394A1, 5,703,080, 6,989,452, 7,087,600, 7,129,261, 7,498,302, and 7,507,420, all of which are expressly incorporated by reference.

[0236] Other antitumor agents that can be conjugated to the antibodies of the invention include BCNU, streptozoicin, vincristine and 5-fluorouracil, the family of agents known collectively LL-E33288 complex described in U.S. Pat. Nos. 5,053,394, 5,770,710, as well as esperamicins (U.S. Pat. No. 5,877,296).

[0237] Enzymatically active toxins and fragments thereof which can be used include diphtheria A chain, nonbinding active fragments of diphtheria toxin, exotoxin A chain (from Pseudomonas aeruginosa), ricin A chain, abrin A chain, modeccin A chain, alpha-sarcin, Aleurites fordii proteins, dianthin proteins, Phytolaca americana proteins (PAPI, PAPII, and PAP-S), momordica charantia inhibitor, curcin, crotin, sapaonaria officinalis inhibitor, gelonin, mitogellin, restrictocin, phenomycin, enomycin and the tricothecenes. See, for example, WO 93/21232 published Oct. 28, 1993.

[0238] The present invention further contemplates an ADC formed between an antibody and a compound with nucleolytic activity (e.g., a ribonuclease or a DNA endonuclease such as a deoxyribonuclease; DNase).

[0239] For selective destruction of the tumor, the antibody may comprise a highly radioactive atom. A variety of radioactive isotopes are available for the production of radioconjugated antibodies. Examples include At211, I131, I125, Y90, Re186, Re188, Sm153, Bi212, P32, Pb212 and radioactive isotopes of Lu.

[0240] The radio- or other labels may be incorporated in the conjugate in known ways. For example, the peptide may be biosynthesized or may be synthesized by chemical amino acid synthesis using suitable amino acid precursors involving, for example, fluorine-19 in place of hydrogen. Labels such as Tc99m or I123, Re186, Re188 and In111 can be attached via a cysteine residue in the peptide. Yttrium-90 can be attached via a lysine residue. The IODOGEN method (Fraker et al (1978) Biochem. Biophys. Res. Commun. 80: 49-57 can be used to incorporate Iodine-123. “Monoclonal Antibodies in Immunoscintigraphy” (Chatal, CRC Press 1989) describes other methods in detail.

[0241] For compositions comprising a plurality of antibodies, the drug loading is represented by p, the average number of drug molecules per Antibody. Drug loading may range from 1 to 20 drugs (D) per Antibody. The average number of drugs per antibody in preparation of conjugation reactions may be characterized by conventional means such as mass spectroscopy, ELISA assay, and HPLC. The quantitative distribution of Antibody-Drug-Conjugates in terms of p may also be determined.

[0242] In some instances, separation, purification, and characterization of homogeneous Antibody-Drug-conjugates where p is a certain value from Antibody-Drug-Conjugates with other drug loadings may be achieved by means such as reverse phase HPLC or electrophoresis. In exemplary embodiments, p is 2, 3, 4, 5, 6, 7, or 8 or a fraction thereof.

[0243] The generation of Antibody-drug conjugate compounds can be accomplished by any technique known to the skilled artisan. Briefly, the Antibody-drug conjugate compounds can include a multispecific antibody as the Antibody unit, a drug, and optionally a linker that joins the drug and the binding agent.

[0244] A number of different reactions are available for covalent attachment of drugs and/or linkers to binding agents. This is can be accomplished by reaction of the amino acid residues of the binding agent, for example, antibody molecule, including the amine groups of lysine, the free carboxylic acid groups of glutamic and aspartic acid, the sulfhydryl groups of cysteine and the various moieties of the aromatic amino acids. A commonly used non-specific methods of covalent attachment is the carbodiimide reaction to link a carboxy (or amino) group of a compound to amino (or carboxy) groups of the antibody. Additionally, bifunctional agents such as dialdehydes or imidoesters have been used to link the amino group of a compound to amino groups of an antibody molecule.

[0245] Also available for attachment of drugs to binding agents is the Schiff base reaction. This method involves the periodate oxidation of a drug that contains glycol or hydroxy groups, thus forming an aldehyde which is then reacted with the binding agent. Attachment occurs via formation of a Schiff base with amino groups of the binding agent. Isothiocyanates can also be used as coupling agents for covalently attaching drugs to binding agents. Other techniques are known to the skilled artisan and within the scope of the present invention.

[0246] In some embodiments, an intermediate, which is the precursor of the linker, is reacted with the drug under appropriate conditions. In other embodiments, reactive groups are used on the drug and/or the intermediate. The product of the reaction between the drug and the intermediate, or the derivatized drug, is subsequently reacted with a multispecific antibody of the invention under appropriate conditions.

[0247] It will be understood that chemical modifications may also be made to the desired compound in order to make reactions of that compound more convenient for purposes of preparing conjugates of the invention. For example a functional group e.g. amine, hydroxyl, or sulfhydryl, may be appended to the drug at a position which has minimal or an acceptable effect on the activity or other properties of the drug

[0248] Typically, the antibody-drug conjugate compounds comprise a Linker unit between the drug unit and the antibody unit. In some embodiments, the linker is cleavable under intracellular or extracellular conditions, such that cleavage of the linker releases the drug unit from the antibody in the appropriate environment. For example, solid tumors that secrete certain proteases may serve as the target of the cleavable linker; in other embodiments, it is the intracellular proteases that are utilized. In yet other embodiments, the linker unit is not cleavable and the drug is released, for example, by antibody degradation in lysosomes.

[0249] In some embodiments, the linker is cleavable by a cleaving agent that is present in the intracellular environment (for example, within a lysosome or endosome or caveolea). The linker can be, for example, a peptidyl linker that is cleaved by an intracellular peptidase or protease enzyme, including, but not limited to, a lysosomal or endosomal protease. In some embodiments, the peptidyl linker is at least two amino acids long or at least three amino acids long or more.

[0250] Cleaving agents can include, without limitation, cathepsins B and D and plasmin, all of which are known to hydrolyze dipeptide drug derivatives resulting in the release of active drug inside target cells (see, e.g., Dubowchik and Walker, 1999, Pharm. Therapeutics 83:67-123). Peptidyl linkers that are cleavable by enzymes that are present in CD38-expressing cells. For example, a peptidyl linker that is cleavable by the thiol-dependent protease cathepsin-B, which is highly expressed in cancerous tissue, can be used (e.g., a Phe-Leu or a Gly-Phe-Leu-Gly linker (SEQ ID NO: X)). Other examples of such linkers are described, e.g., in U.S. Pat. No. 6,214,345, incorporated herein by reference in its entirety and for all purposes.

[0251] In some embodiments, the peptidyl linker cleavable by an intracellular protease is a Val-Cit linker or a Phe-Lys linker (see, e.g., U.S. Pat. No. 6,214,345, which describes the synthesis of doxorubicin with the val-cit linker).

[0252] In other embodiments, the cleavable linker is pH-sensitive, that is, sensitive to hydrolysis at certain pH values. Typically, the pH-sensitive linker hydrolyzable under acidic conditions. For example, an acid-labile linker that is hydrolyzable in the lysosome (for example, a hydrazone, semicarbazone, thiosemicarbazone, cis-aconitic amide, orthoester, acetal, ketal, or the like) may be used. (See, e.g., U.S. Pat. Nos. 5,122,368; 5,824,805; 5,622,929; Dubowchik and Walker, 1999, Pharm. Therapeutics 83:67-123; Neville et al., 1989, Biol. Chem. 264:14653-14661.) Such linkers are relatively stable under neutral pH conditions, such as those in the blood, but are unstable at below pH 5.5 or 5.0, the approximate pH of the lysosome. In certain embodiments, the hydrolyzable linker is a thioether linker (such as, e.g., a thioether attached to the therapeutic agent via an acylhydrazone bond (see, e.g., U.S. Pat. No. 5,622,929).

[0253] In yet other embodiments, the linker is cleavable under reducing conditions (for example, a disulfide linker). A variety of disulfide linkers are known in the art, including, for example, those that can be formed using SATA (N-succinimidyl-5-acetylthioacetate), SPDP (N-succinimidyl-3-(2-pyridyldithio)propionate), SPDB (N-succinimidyl-3-(2-pyridyldithio)butyrate) and SMPT (N-succinimidyl-oxycarbonyl-alpha-methyl-alpha-(2-pyridyl-dithio)toluene)-, SPDB and SMPT. (See, e.g., Thorpe et al., 1987, Cancer Res. 47:5924-5931; Wawrzynczak et al., In Immunoconjugates: Antibody Conjugates in Radioimagery and Therapy of Cancer (C. W. Vogel ed., Oxford U. Press, 1987. See also U.S. Pat. No. 4,880,935.)

[0254] In other embodiments, the linker is a malonate linker (Johnson et al., 1995, Anticancer Res. 15:1387-93), a maleimidobenzoyl linker (Lau et al., 1995, Bioorg-Med-Chem. 3(10):1299-1304), or a 3′-N-amide analog (Lau et al., 1995, Bioorg-Med-Chem. 3(10):1305-12).

[0255] In yet other embodiments, the linker unit is not cleavable and the drug is released by antibody degradation. (See U.S. Publication No. 2005/0238649 incorporated by reference herein in its entirety and for all purposes).

[0256] In many embodiments, the linker is self-immolative. As used herein, the term “self-immolative Spacer” refers to a bifunctional chemical moiety that is capable of covalently linking together two spaced chemical moieties into a stable tripartite molecule. It will spontaneously separate from the second chemical moiety if its bond to the first moiety is cleaved. See for example, WO 2007059404A2, WO06110476A2, WO05112919A2, WO2010/062171, WO09/017394, WO07/089149, WO 07/018431, WO04/043493 and WO02/083180, which are directed to drug-cleavable substrate conjugates where the drug and cleavable substrate are optionally linked through a self-immolative linker and which are all expressly incorporated by reference.

[0257] Often the linker is not substantially sensitive to the extracellular environment. As used herein, “not substantially sensitive to the extracellular environment,” in the context of a linker, means that no more than about 20%, 15%, 10%, 5%, 3%, or no more than about 1% of the linkers, in a sample of antibody-drug conjugate compound, are cleaved when the antibody-drug conjugate compound presents in an extracellular environment (for example, in plasma).

[0258] Whether a linker is not substantially sensitive to the extracellular environment can be determined, for example, by incubating with plasma the antibody-drug conjugate compound for a predetermined time period (for example, 2, 4, 8, 16, or 24 hours) and then quantitating the amount of free drug present in the plasma.

[0259] In other, non-mutually exclusive embodiments, the linker promotes cellular internalization. In certain embodiments, the linker promotes cellular internalization when conjugated to the therapeutic agent (that is, in the milieu of the linker-therapeutic agent moiety of the antibody-drug conjugate compound as described herein). In yet other embodiments, the linker promotes cellular internalization when conjugated to both the auristatin compound and the multispecific antibodies of the invention.

[0260] A variety of exemplary linkers that can be used with the present compositions and methods are described in WO 2004-010957, U.S. Publication No. 2006/0074008, U.S. Publication No. 20050238649, and U.S. Publication No. 2006/0024317 (each of which is incorporated by reference herein in its entirety and for all purposes).

[0261] Drug loading is represented by p and is the average number of Drug moieties per antibody in a molecule. Drug loading (“p”) may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more moieties (D) per antibody, although frequently the average number is a fraction or a decimal. Generally, drug loading of from 1 to 4 is frequently useful, and from 1 to 2 is also useful. ADCs of the invention include collections of antibodies conjugated with a range of drug moieties, from 1 to 20. The average number of drug moieties per antibody in preparations of ADC from conjugation reactions may be characterized by conventional means such as mass spectroscopy and, ELISA assay.

[0262] The quantitative distribution of ADC in terms of p may also be determined. In some instances, separation, purification, and characterization of homogeneous ADC where p is a certain value from ADC with other drug loadings may be achieved by means such as electrophoresis.

[0263] For some antibody-drug conjugates, p may be limited by the number of attachment sites on the antibody. For example, where the attachment is a cysteine thiol, as in the exemplary embodiments above, an antibody may have only one or several cysteine thiol groups, or may have only one or several sufficiently reactive thiol groups through which a linker may be attached. In certain embodiments, higher drug loading, e.g. p>5, may cause aggregation, insolubility, toxicity, or loss of cellular permeability of certain antibody-drug conjugates. In certain embodiments, the drug loading for an ADC of the invention ranges from 1 to about 8; from about 2 to about 6; from about 3 to about 5; from about 3 to about 4; from about 3.1 to about 3.9; from about 3.2 to about 3.8; from about 3.2 to about 3.7; from about 3.2 to about 3.6; from about 3.3 to about 3.8; or from about 3.3 to about 3.7. Indeed, it has been shown that for certain ADCs, the optimal ratio of drug moieties per antibody may be less than 8, and may be about 2 to about 5. See US 2005-0238649 A1 (herein incorporated by reference in its entirety).

[0264] In certain embodiments, fewer than the theoretical maximum of drug moieties are conjugated to an antibody during a conjugation reaction. An antibody may contain, for example, lysine residues that do not react with the drug-linker intermediate or linker reagent, as discussed below. Generally, antibodies do not contain many free and reactive cysteine thiol groups which may be linked to a drug moiety; indeed most cysteine thiol residues in antibodies exist as disulfide bridges. In certain embodiments, an antibody may be reduced with a reducing agent such as dithiothreitol (DTT) or tricarbonylethylphosphine (TCEP), under partial or total reducing conditions, to generate reactive cysteine thiol groups. In certain embodiments, an antibody is subjected to denaturing conditions to reveal reactive nucleophilic groups such as lysine or cysteine.

[0265] The loading (drug/antibody ratio) of an ADC may be controlled in different ways, e.g., by: (i) limiting the molar excess of drug-linker intermediate or linker reagent relative to antibody, (ii) limiting the conjugation reaction time or temperature, (iii) partial or limiting reductive conditions for cysteine thiol modification, (iv) engineering by recombinant techniques the amino acid sequence of the antibody such that the number and position of cysteine residues is modified for control of the number and/or position of linker-drug attachments (such as thioMab or thioFab prepared as disclosed herein and in WO2006/034488 (herein incorporated by reference in its entirety)).

[0266] It is to be understood that where more than one nucleophilic group reacts with a drug-linker intermediate or linker reagent followed by drug moiety reagent, then the resulting product is a mixture of ADC compounds with a distribution of one or more drug moieties attached to an antibody. The average number of drugs per antibody may be calculated from the mixture by a dual EL ISA antibody assay, which is specific for antibody and specific for the drug. Individual ADC molecules may be identified in the mixture by mass spectroscopy and separated by HPLC, e.g. hydrophobic interaction chromatography.

[0267] In some embodiments, a homogeneous ADC with a single loading value may be isolated from the conjugation mixture by electrophoresis or chromatography.

[0268] Methods of determining whether a Drug or Antibody-Drug conjugate exerts a cytostatic and/or cytotoxic effect on a cell are known. Generally, the cytotoxic or cytostatic activity of an Antibody Drug conjugate can be measured by: exposing mammalian cells expressing a target protein of the Antibody Drug conjugate in a cell culture medium; culturing the cells for a period from about 6 hours to about 5 days; and measuring cell viability. Cell-based in vitro assays can be used to measure viability (proliferation), cytotoxicity, and induction of apoptosis (caspase activation) of the Antibody Drug conjugate.

[0269] For determining whether an Antibody Drug conjugate exerts a cytostatic effect, a thymidine incorporation assay may be used. For example, cancer cells expressing a target antigen at a density of 5,000 cells/well of a 96-well plated can be cultured for a 72-hour period and exposed to 0.5 ρCi of 3H-thymidine during the final 8 hours of the 72-hour period. The incorporation of 3H-thymidine into cells of the culture is measured in the presence and absence of the Antibody Drug conjugate.

[0270] For determining cytotoxicity, necrosis or apoptosis (programmed cell death) can be measured. Necrosis is typically accompanied by increased permeability of the plasma membrane; swelling of the cell, and rupture of the plasma membrane. Apoptosis is typically characterized by membrane blebbing, condensation of cytoplasm, and the activation of endogenous endonucleases. Determination of any of these effects on cancer cells indicates that an Antibody Drug conjugate is useful in the treatment of cancers.

[0271] Cell viability can be measured by determining in a cell the uptake of a dye such as neutral red, trypan blue, or ALAMAR™ blue (see, e.g., Page et al., 1993, Intl. J. Oncology 3:473-476). In such an assay, the cells are incubated in media containing the dye, the cells are washed, and the remaining dye, reflecting cellular uptake of the dye, is measured spectrophotometrically. The protein-binding dye sulforhodamine B (SRB) can also be used to measure cytoxicity (Skehan et al., 1990, J. Natl. Cancer Inst. 82:1107-12).

[0272] Alternatively, a tetrazolium salt, such as MTT, is used in a quantitative colorimetric assay for mammalian cell survival and proliferation by detecting living, but not dead, cells (see, e.g., Mosmann, 1983, J. Immunol. Methods 65:55-63).

[0273] Apoptosis can be quantitated by measuring, for example, DNA fragmentation. Commercial photometric methods for the quantitative in vitro determination of DNA fragmentation are available. Examples of such assays, including TUNEL (which detects incorporation of labeled nucleotides in fragmented DNA) and ELISA-based assays, are described in Biochemica, 1999, no. 2, pp. 34-37 (Roche Molecular Biochemicals).

[0274] Apoptosis can also be determined by measuring morphological changes in a cell. For example, as with necrosis, loss of plasma membrane integrity can be determined by measuring uptake of certain dyes (e.g., a fluorescent dye such as, for example, acridine orange or ethidium bromide). A method for measuring apoptotic cell number has been described by Duke and Cohen, Current Protocols in Immunology (Coligan et al. eds., 1992, pp. 3.17.1-3.17.16). Cells also can be labeled with a DNA dye (e.g., acridine orange, ethidium bromide, or propidium iodide) and the cells observed for chromatin condensation and margination along the inner nuclear membrane. Other morphological changes that can be measured to determine apoptosis include, e.g., cytoplasmic condensation, increased membrane blebbing, and cellular shrinkage.

[0275] The presence of apoptotic cells can be measured in both the attached and “floating” compartments of the cultures. For example, both compartments can be collected by removing the supernatant, trypsinizing the attached cells, combining the preparations following a centrifugation wash step (e.g., 10 minutes at 2000 rpm), and detecting apoptosis (e.g., by measuring DNA fragmentation). (See, e.g., Piazza et al., 1995, Cancer Research 55:3110-16).

[0276] In vivo, the effect of a therapeutic composition of the multispecific antibody of the invention can be evaluated in a suitable animal model. For example, xenogenic cancer models can be used, wherein cancer explants or passaged xenograft tissues are introduced into immune compromised animals, such as nude or SCID mice (Klein et al., 1997, Nature Medicine 3: 402-408). Efficacy can be measured using assays that measure inhibition of tumor formation, tumor regression or metastasis, and the like.

[0277] The therapeutic compositions used in the practice of the foregoing methods can be formulated into pharmaceutical compositions comprising a carrier suitable for the desired delivery method. Suitable carriers include any material that when combined with the therapeutic composition retains the anti-tumor function of the therapeutic composition and is generally non-reactive with the patient's immune system. Examples include, but are not limited to, any of a number of standard pharmaceutical carriers such as sterile phosphate buffered saline solutions, bacteriostatic water, and the like (see, generally, Remington's Pharmaceutical Sciences 16th Edition, A. Osal., Ed., 1980).

[0278] In one embodiment, the molecules disclosed herein are antibody “fusion proteins”, sometimes referred to herein as “antibody conjugates”. The fusion partner or conjugate partner can be proteinaceous or non-proteinaceous; the latter generally being generated using functional groups on the antibody and on the conjugate partner. Conjugate and fusion partners may be any molecule, including small molecule chemical compounds and polypeptides. For example, a variety of antibody conjugates and methods are described in Trail et al., 1999, Curr. Opin. Immunol. 11:584-588, incorporated entirely by reference. Possible conjugate partners include but are not limited to cytokines, cytotoxic agents, toxins, radioisotopes, chemotherapeutic agent, anti-angiogenic agents, a tyrosine kinase inhibitors, and other therapeutically active agents. In some embodiments, conjugate partners may be thought of more as payloads, that is to say that the goal of a conjugate is targeted delivery of the conjugate partner to a targeted cell, for example a cancer cell or immune cell, by the immunoglobulin. Thus, for example, the conjugation of a toxin to an immunoglobulin targets the delivery of said toxin to cells expressing the target antigen. As will be appreciated by one skilled in the art, in reality the concepts and definitions of fusion and conjugate are overlapping. The designation of a fusion or conjugate is not meant to constrain it to any particular embodiment disclosed herein. Rather, these terms are used loosely to convey the broad concept that any immunoglobulin disclosed herein may be linked genetically, chemically, or otherwise, to one or more polypeptides or molecules to provide some desirable property.

[0279] Suitable conjugates include, but are not limited to, labels as described below, drugs and cytotoxic agents including, but not limited to, cytotoxic drugs (e.g., chemotherapeutic agents) or toxins or active fragments of such toxins. Suitable toxins and their corresponding fragments include diptheria A chain, exotoxin A chain, ricin A chain, abrin A chain, curcin, crotin, phenomycin, enomycin and the like. Cytotoxic agents also include radiochemicals made by conjugating radioisotopes to antibodies, or binding of a radionuclide to a chelating agent that has been covalently attached to the antibody. Additional embodiments utilize calicheamicin, auristatins, geldanamycin, maytansine, and duocarmycins and analogs.

[0280] In one embodiment, the molecules disclosed herein are fused or conjugated to a cytokine. By “cytokine” as used herein is meant a generic term for proteins released by one cell population that act on another cell as intercellular mediators. For example, as described in Penichet et al., 2001, J. Immunol. Methods 248:91-101, incorporated entirely by reference, cytokines may be fused to antibody to provide an array of desirable properties. Examples of such cytokines are lymphokines, monokines, and traditional polypeptide hormones. Included among the cytokines are growth hormone such as human growth hormone, N-methionyl human growth hormone, and bovine growth hormone; parathyroid hormone; thyroxine; insulin; proinsulin; relaxin; prorelaxin; glycoprotein hormones such as follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), and luteinizing hormone (LH); hepatic growth factor; fibroblast growth factor; prolactin; placental lactogen; tumor necrosis factor-alpha and -beta; mullerian-inhibiting substance; mouse gonadotropin-associated peptide; inhibin; activin; vascular endothelial growth factor; integrin; thrombopoietin (TPO); nerve growth factors such as NGF-beta; platelet-growth factor; transforming growth factors (TGFs) such as TGF-alpha and TGF-beta; insulin-like growth factor-I and -II; erythropoietin (EPO); osteoinductive factors; interferons such as interferon-alpha, beta, and -gamma; colony stimulating factors (CSFs) such as macrophage-CSF (M-CSF); granulocyte-macrophage-CSF (GM-CSF); and granulocyte-CSF (G-CSF); interleukins (ILs) such as IL-1, IL-1alpha, IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-11, IL-12; IL-15, a tumor necrosis factor such as TNF-alpha or TNF-beta; C5a; and other polypeptide factors including LIF and kit ligand (KL). As used herein, the term cytokine includes proteins from natural sources or from recombinant cell culture, and biologically active equivalents of the native sequence cytokines.

[0281] In yet another embodiment, an molecules disclosed herein may be conjugated to a “receptor” (such streptavidin) for utilization in tumor pretargeting wherein the immunoglobulin-receptor conjugate is administered to the patient, followed by removal of unbound conjugate from the circulation using a clearing agent and then administration of a “ligand” (e.g. avidin) which is conjugated to a cytotoxic agent (e.g. a radionucleotide). In an alternate embodiment, the immunoglobulin is conjugated or operably linked to an enzyme in order to employ Antibody Dependent Enzyme Mediated Prodrug Therapy (ADEPT). ADEPT may be used by conjugating or operably linking the immunoglobulin to a prodrug-activating enzyme that converts a prodrug (e.g. a peptidyl chemotherapeutic agent.

[0282] When immunoglobulin partners are used as conjugates, conjugate partners may be linked to any region of an immunoglobulin disclosed herein, including at the N- or C-termini, or at some residue in-between the termini. A variety of linkers may find use in immunoglobulins disclosed herein to covalently link conjugate partners to an immunoglobulin. By “linker”, “linker sequence”, “spacer”, “tethering sequence” or grammatical equivalents thereof, herein is meant a molecule or group of molecules (such as a monomer or polymer) that connects two molecules and often serves to place the two molecules in one configuration. Linkers are known in the art; for example, homo- or hetero-bifunctional linkers as are well known (see, 1994 Pierce Chemical Company catalog, technical section on cross-linkers, pages 155-200, incorporated entirely by reference). A number of strategies may be used to covalently link molecules together. These include, but are not limited to polypeptide linkages between N- and C-termini of proteins or protein domains, linkage via disulfide bonds, and linkage via chemical cross-linking reagents. In one aspect of this embodiment, the linker is a peptide bond, generated by recombinant techniques or peptide synthesis. The linker peptide may predominantly include the following amino acid residues: Gly, Ser, Ala, or Thr. The linker peptide should have a length that is adequate to link two molecules in such a way that they assume the correct conformation relative to one another so that they retain the desired activity. Suitable lengths for this purpose include at least one and not more than 50 amino acid residues. In one embodiment, the linker is from about 1 to 30 amino acids in length, e.g., a linker may be 1 to 20 amino acids in length. Useful linkers include glycine-serine polymers (including, for example, (GS)n, (GSGGS)n (Set forth as SEQ ID NO:1), (GGGGS)n (Set forth as SEQ ID NO:2) and (GGGS)n (Set forth as SEQ ID NO:3), where n is an integer of at least one), glycine-alanine polymers, alanine-serine polymers, and other flexible linkers, as will be appreciated by those in the art. Alternatively, a variety of nonproteinaceous polymers, including but not limited to polyethylene glycol (PEG), polypropylene glycol, polyoxyalkylenes, or copolymers of polyethylene glycol and polypropylene glycol, may find use as linkers.

[0283] Also disclosed herein are methods for producing and experimentally testing the antibodies used in the methods described herein. The disclosed methods are not meant to constrain embodiments to any particular application or theory of operation. Rather, the provided methods are meant to illustrate generally that one or more immunoglobulins may be produced and experimentally tested to obtain immunoglobulins. General methods for antibody molecular biology, expression, purification, and screening are described in Antibody Engineering, edited by Duebel & Kontermann, Springer-Verlag, Heidelberg, 2001; and Hayhurst & Georgiou, 2001, Curr Opin Chem Biol 5:683-689; Maynard & Georgiou, 2000, Annu Rev Biomed Eng 2:339-76; Antibodies: A Laboratory Manual by Harlow & Lane, New York: Cold Spring Harbor Laboratory Press, 1988, all incorporated entirely by reference.

[0284] In one embodiment disclosed herein, nucleic acids are created that encode the molecules, and that may then be cloned into host cells, expressed and assayed, if desired. Thus, nucleic acids, and particularly DNA, may be made that encode each protein sequence. These practices are carried out using well-known procedures. For example, a variety of methods that may find use in generating immunoglobulins disclosed herein are described in Molecular Cloning—A Laboratory Manual, 3rd Ed. (Maniatis, Cold Spring Harbor Laboratory Press, New York, 2001), and Current Protocols in Molecular Biology (John Wiley & Sons), both incorporated entirely by reference. As will be appreciated by those skilled in the art, the generation of exact sequences for a library comprising a large number of sequences is potentially expensive and time consuming. By “library” herein is meant a set of variants in any form, including but not limited to a list of nucleic acid or amino acid sequences, a list of nucleic acid or amino acid substitutions at variable positions, a physical library comprising nucleic acids that encode the library sequences, or a physical library comprising the variant proteins, either in purified or unpurified form. Accordingly, there are a variety of techniques that may be used to efficiently generate libraries disclosed herein. Such methods include but are not limited to gene assembly methods, PCR-based method and methods which use variations of PCR, ligase chain reaction-based methods, pooled oligo methods such as those used in synthetic shuffling, error-prone amplification methods and methods which use oligos with random mutations, classical site-directed mutagenesis methods, cassette mutagenesis, and other amplification and gene synthesis methods. As is known in the art, there are a variety of commercially available kits and methods for gene assembly, mutagenesis, vector subcloning, and the like, and such commercial products find use in for generating nucleic acids that encode immunoglobulins.

[0285] The molecules disclosed herein may be produced by culturing a host cell transformed with nucleic acid, e.g., an expression vector, containing nucleic acid encoding the molecules, under the appropriate conditions to induce or cause expression of the protein. The conditions appropriate for expression will vary with the choice of the expression vector and the host cell, and will be easily ascertained by one skilled in the art through routine experimentation. A wide variety of appropriate host cells may be used, including but not limited to mammalian cells, bacteria, insect cells, and yeast. For example, a variety of cell lines that may find use in generating immunoglobulins disclosed herein are described in the ATCC® cell line catalog, available from the American Type Culture Collection.

[0286] In one embodiment, the molecules are expressed in mammalian expression systems, including systems in which the expression constructs are introduced into the mammalian cells using virus such as retrovirus or adenovirus. Any mammalian cells may be used, e.g., human, mouse, rat, hamster, and primate cells. Suitable cells also include known research cells, including but not limited to Jurkat T cells, NIH3T3, CHO, BHK, COS, HEK293, PER C.6, HeLa, Sp2/0, NS0 cells and variants thereof. In an alternate embodiment, library proteins are expressed in bacterial cells. Bacterial expression systems are well known in the art, and include Escherichia coli (E. coli), Bacillus subtilis, Streptococcus cremoris, and Streptococcus lividans. In alternate embodiments, immunoglobulins are produced in insect cells (e.g. Sf21/Sf9, Trichoplusia ni Bti-Tn5b1-4) or yeast cells (e.g. S. cerevisiae, Pichia, etc). In an alternate embodiment, molecules are expressed in vitro using cell free translation systems. In vitro translation systems derived from both prokaryotic (e.g. E. coli) and eukaryotic (e.g. wheat germ, rabbit reticulocytes) cells are available and may be chosen based on the expression levels and functional properties of the protein of interest. For example, as appreciated by those skilled in the art, in vitro translation is required for some display technologies, for example ribosome display. In addition, the immunoglobulins may be produced by chemical synthesis methods. Also transgenic expression systems both animal (e.g. cow, sheep or goat milk, embryonated hen's eggs, whole insect larvae, etc.) and plant (e.g. corn, tobacco, duckweed, etc.)

[0287] The nucleic acids that encode the molecules disclosed herein may be incorporated into an expression vector in order to express the protein. A variety of expression vectors may be utilized for protein expression. Expression vectors may comprise self-replicating extra-chromosomal vectors or vectors which integrate into a host genome. Expression vectors are constructed to be compatible with the host cell type. Thus expression vectors which find use in generating immunoglobulins disclosed herein include but are not limited to those which enable protein expression in mammalian cells, bacteria, insect cells, yeast, and in in vitro systems. As is known in the art, a variety of expression vectors are available, commercially or otherwise, that may find use for expressing molecules disclosed herein.

[0288] Expression vectors typically comprise a protein operably linked with control or regulatory sequences, selectable markers, any fusion partners, and/or additional elements. By “operably linked” herein is meant that the nucleic acid is placed into a functional relationship with another nucleic acid sequence. Generally, these expression vectors include transcriptional and translational regulatory nucleic acid operably linked to the nucleic acid encoding the molecule, and are typically appropriate to the host cell used to express the protein. In general, the transcriptional and translational regulatory sequences may include promoter sequences, ribosomal binding sites, transcriptional start and stop sequences, translational start and stop sequences, and enhancer or activator sequences. As is also known in the art, expression vectors typically contain a selection gene or marker to allow the selection of transformed host cells containing the expression vector. Selection genes are well known in the art and will vary with the host cell used.

[0289] molecules may be operably linked to a fusion partner to enable targeting of the expressed protein, purification, screening, display, and the like. Fusion partners may be linked to the immunoglobulin sequence via a linker sequences. The linker sequence will generally comprise a small number of amino acids, typically less than ten, although longer linkers may also be used. Typically, linker sequences are selected to be flexible and resistant to degradation. As will be appreciated by those skilled in the art, any of a wide variety of sequences may be used as linkers. For example, a common linker sequence comprises the amino acid sequence GGGGS. A fusion partner may be a targeting or signal sequence that directs immunoglobulin and any associated fusion partners to a desired cellular location or to the extracellular media. As is known in the art, certain signaling sequences may target a protein to be either secreted into the growth media, or into the periplasmic space, located between the inner and outer membrane of the cell. A fusion partner may also be a sequence that encodes a peptide or protein that enables purification and/or screening. Such fusion partners include but are not limited to polyhistidine tags (His-tags) (for example H6 and H10 or other tags for use with Immobilized Metal Affinity Chromatography (IMAC) systems (e.g. Ni+2 affinity columns)), GST fusions, MBP fusions, Strep-tag, the BSP biotinylation target sequence of the bacterial enzyme BirA, and epitope tags which are targeted by antibodies (for example c-myc tags, flag-tags, and the like). As will be appreciated by those skilled in the art, such tags may be useful for purification, for screening, or both. For example, an immunoglobulin may be purified using a His-tag by immobilizing it to a Ni+2 affinity column, and then after purification the same His-tag may be used to immobilize the antibody to a Ni+2 coated plate to perform an ELISA or other binding assay (as described below). A fusion partner may enable the use of a selection method to screen immunoglobulins (see below). Fusion partners that enable a variety of selection methods are well-known in the art. For example, by fusing the members of an immunoglobulin library to the gene III protein, phage display can be employed (Kay et al., Phage display of peptides and proteins: a laboratory manual, Academic Press, San Diego, Calif., 1996; Lowman et al., 1991, Biochemistry 30:10832-10838; Smith, 1985, Science 228:1315-1317, incorporated entirely by reference). Fusion partners may enable immunoglobulins to be labeled. Alternatively, a fusion partner may bind to a specific sequence on the expression vector, enabling the fusion partner and associated immunoglobulin to be linked covalently or noncovalently with the nucleic acid that encodes them. The methods of introducing exogenous nucleic acid into host cells are well known in the art, and will vary with the host cell used. Techniques include but are not limited to dextran-mediated transfection, calcium phosphate precipitation, calcium chloride treatment, polybrene mediated transfection, protoplast fusion, electroporation, viral or phage infection, encapsulation of the polynucleotide(s) in liposomes, and direct microinjection of the DNA into nuclei. In the case of mammalian cells, transfection may be either transient or stable.

[0290] In one embodiment, molecules are purified or isolated after expression. Proteins may be isolated or purified in a variety of ways known to those skilled in the art. Standard purification methods include chromatographic techniques, including ion exchange, hydrophobic interaction, affinity, sizing or gel filtration, and reversed-phase, carried out at atmospheric pressure or at high pressure using systems such as FPLC and HPLC. Purification methods also include electrophoretic, immunological, precipitation, dialysis, and chromatofocusing techniques. Ultrafiltration and diafiltration techniques, in conjunction with protein concentration, are also useful. As is well known in the art, a variety of natural proteins bind Fc and antibodies, and these proteins can find use for purification of immunoglobulins disclosed herein. For example, the bacterial proteins A and G bind to the Fc region. Likewise, the bacterial protein L binds to the Fab region of some antibodies, as of course does the antibody's target antigen. Purification can often be enabled by a particular fusion partner. For example, immunoglobulins may be purified using glutathione resin if a GST fusion is employed, Ni+2 affinity chromatography if a His-tag is employed, or immobilized anti-flag antibody if a flag-tag is used. For general guidance in suitable purification techniques, see, e.g. incorporated entirely by reference Protein Purification: Principles and Practice, 3rd Ed., Scopes, Springer-Verlag, N Y, 1994, incorporated entirely by reference. The degree of purification necessary will vary depending on the screen or use of the immunoglobulins. In some instances no purification is necessary. For example in one embodiment, if the immunoglobulins are secreted, screening may take place directly from the media. As is well known in the art, some methods of selection do not involve purification of proteins. Thus, for example, if a library of immunoglobulins is made into a phage display library, protein purification may not be performed.

[0291] molecules may be screened using a variety of methods, including but not limited to those that use in vitro assays, in vivo and cell-based assays, and selection technologies. Automation and high-throughput screening technologies may be utilized in the screening procedures. Screening may employ the use of a fusion partner or label. The use of fusion partners has been discussed above. By “labeled” herein is meant that the immunoglobulins disclosed herein have one or more elements, isotopes, or chemical compounds attached to enable the detection in a screen. In general, labels fall into three classes: a) immune labels, which may be an epitope incorporated as a fusion partner that is recognized by an antibody, b) isotopic labels, which may be radioactive or heavy isotopes, and c) small molecule labels, which may include fluorescent and colorimetric dyes, or molecules such as biotin that enable other labeling methods. Labels may be incorporated into the compound at any position and may be incorporated in vitro or in vivo during protein expression.

[0292] In one embodiment, the functional and/or biophysical properties of molecules are screened in an in vitro assay. In vitro assays may allow a broad dynamic range for screening properties of interest. Properties that may be screened include but are not limited to stability, solubility, and affinity for Fc ligands, for example FcγRs. Multiple properties may be screened simultaneously or individually. Proteins may be purified or unpurified, depending on the requirements of the assay. In one embodiment, the screen is a qualitative or quantitative binding assay for binding of molecules to a protein or nonprotein molecule that is known or thought to bind the molecule. In one embodiment, the screen is a binding assay for measuring binding to the target antigen. In an alternate embodiment, the screen is an assay for binding of molecules to an Fc ligand, including but are not limited to the family of FcγRs, the neonatal receptor FcRn, the complement protein C1q, and the bacterial proteins A and G. Said Fc ligands may be from any organism. In one embodiment, Fc ligands are from humans, mice, rats, rabbits, and/or monkeys. Binding assays can be carried out using a variety of methods known in the art, including but not limited to FRET (Fluorescence Resonance Energy Transfer) and BRET (Bioluminescence Resonance Energy Transfer)-based assays, AlphaScreen™ (Amplified Luminescent Proximity Homogeneous Assay), Scintillation Proximity Assay, ELISA (Enzyme-Linked Immunosorbent Assay), SPR (Surface Plasmon Resonance, also known as BIACORE®), isothermal titration calorimetry, differential scanning calorimetry, gel electrophoresis, and chromatography including gel filtration. These and other methods may take advantage of some fusion partner or label of the immunoglobulin. Assays may employ a variety of detection methods including but not limited to chromogenic, fluorescent, luminescent, or isotopic labels.

[0293] The biophysical properties of molecules, for example stability and solubility, may be tested using a variety of methods known in the art. Protein stability may be determined by measuring the thermodynamic equilibrium between folded and unfolded states. For example, molecules disclosed herein may be unfolded using chemical denaturant, heat, or pH, and this transition may be monitored using methods including but not limited to circular dichroism spectroscopy, fluorescence spectroscopy, absorbance spectroscopy, NMR spectroscopy, calorimetry, and proteolysis. As will be appreciated by those skilled in the art, the kinetic parameters of the folding and unfolding transitions may also be monitored using these and other techniques. The solubility and overall structural integrity of an molecule may be quantitatively or qualitatively determined using a wide range of methods that are known in the art. Methods which may find use for characterizing the biophysical properties of molecules disclosed herein include gel electrophoresis, isoelectric focusing, capillary electrophoresis, chromatography such as size exclusion chromatography, ion-exchange chromatography, and reversed-phase high performance liquid chromatography, peptide mapping, oligosaccharide mapping, mass spectrometry, ultraviolet absorbance spectroscopy, fluorescence spectroscopy, circular dichroism spectroscopy, isothermal titration calorimetry, differential scanning calorimetry, analytical ultra-centrifugation, dynamic light scattering, proteolysis, and cross-linking, turbidity measurement, filter retardation assays, immunological assays, fluorescent dye binding assays, protein-staining assays, microscopy, and detection of aggregates via ELISA or other binding assay. Structural analysis employing X-ray crystallographic techniques and NMR spectroscopy may also find use. In one embodiment, stability and/or solubility may be measured by determining the amount of protein solution after some defined period of time. In this assay, the protein may or may not be exposed to some extreme condition, for example elevated temperature, low pH, or the presence of denaturant. Because function typically requires a stable, soluble, and/or well-folded/structured protein, the aforementioned functional and binding assays also provide ways to perform such a measurement. For example, a solution comprising an immunoglobulin could be assayed for its ability to bind target antigen, then exposed to elevated temperature for one or more defined periods of time, then assayed for antigen binding again. Because unfolded and aggregated protein is not expected to be capable of binding antigen, the amount of activity remaining provides a measure of the molecule's stability and solubility.

[0294] In one embodiment, molecules may be tested using one or more cell-based or in vitro assays. For such assays, immunoglobulins, purified or unpurified, are typically added exogenously such that cells are exposed to individual variants or groups of variants belonging to a library. These assays are typically, but not always, based on the biology of the ability of the immunoglobulin to bind to the target antigen and mediate some biochemical event, for example effector functions like cellular lysis, phagocytosis, ligand/receptor binding inhibition, inhibition of growth and/or proliferation, apoptosisand the like. Such assays often involve monitoring the response of cells to immunoglobulin, for example cell survival, cell death, cellular phagocytosis, cell lysis, change in cellular morphology, or transcriptional activation such as cellular expression of a natural gene or reporter gene. For example, such assays may measure the ability of molecules to elicit ADCC, ADCP, or CDC. For some assays additional cells or components, that is in addition to the target cells, may need to be added, for example serum complement, or effector cells such as peripheral blood monocytes (PBMCs), NK cells, macrophages, and the like. Such additional cells may be from any organism, e.g., humans, mice, rat, rabbit, and monkey. Crosslinked or monomeric antibodies may cause apoptosis of certain cell lines expressing the antibody's target antigen, or they may mediate attack on target cells by immune cells which have been added to the assay. Methods for monitoring cell death or viability are known in the art, and include the use of dyes, fluorophores, immunochemical, cytochemical, and radioactive reagents. For example, caspase assays or annexin-flourconjugates may enable apoptosis to be measured, and uptake or release of radioactive substrates (e.g. Chromium-51 release assays) or the metabolic reduction of fluorescent dyes such as alamar blue may enable cell growth, proliferation or activation to be monitored. In one embodiment, the DELFIA® EuTDA-based cytotoxicity assay (Perkin Elmer, Mass.) is used. Alternatively, dead or damaged target cells may be monitored by measuring the release of one or more natural intracellular proteins, for example lactate dehydrogenase. Transcriptional activation may also serve as a method for assaying function in cell-based assays. In this case, response may be monitored by assaying for natural genes or proteins which may be upregulated or down-regulated, for example the release of certain interleukins may be measured, or alternatively readout may be via a luciferase or GFP-reporter construct. Cell-based assays may also involve the measure of morphological changes of cells as a response to the presence of an immunoglobulin. Cell types for such assays may be prokaryotic or eukaryotic, and a variety of cell lines that are known in the art may be employed. Alternatively, cell-based screens are performed using cells that have been transformed or transfected with nucleic acids encoding the molecules.

[0295] In vitro assays include but are not limited to binding assays, ADCC, CDC, cytotoxicity, proliferation, peroxide/ozone release, chemotaxis of effector cells, inhibition of such assays by reduced effector function antibodies; ranges of activities such as >100× improvement or >100× reduction, blends of receptor activation and the assay outcomes that are expected from such receptor profiles.

[0296] The biological properties of the molecules disclosed herein may be characterized in cell, tissue, and whole organism experiments. As is known in the art, drugs are often tested in animals, including but not limited to mice, rats, rabbits, dogs, cats, pigs, and monkeys, in order to measure a drug's efficacy for treatment against a disease or disease model, or to measure a drug's pharmacokinetics, toxicity, and other properties. Said animals may be referred to as disease models. With respect to the molecules disclosed herein, a particular challenge arises when using animal models to evaluate the potential for in-human efficacy of candidate polypeptides—this is due, at least in part, to the fact that molecules that have a specific effect on the affinity for a human Fc receptor may not have a similar affinity effect with the orthologous animal receptor. These problems can be further exacerbated by the inevitable ambiguities associated with correct assignment of true orthologues (Mechetina et al., Immunogenetics, 2002 54:463-468, incorporated entirely by reference), and the fact that some orthologues simply do not exist in the animal (e.g. humans possess an FcγRIIa whereas mice do not). Therapeutics are often tested in mice, including but not limited to mouse strains NZB, NOD, BXSB, MRL/Ipr, K/BxN and transgenics (including knockins and knockouts). Such mice can develop various autoimmune conditions that resemble human organ specific, systemic autoimmune or inflammatory disease pathologies such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). For example, an immunoglobulin disclosed herein intended for autoimmune diseases may be tested in such mouse models by treating the mice to determine the ability of the immunoglobulin to reduce or inhibit the development of the disease pathology. Because of the incompatibility between the mouse and human Fcγ receptor system, an alternative approach is to use a murine SCID model in which immune deficient mice are engrafted with human PBLs or PBMCs (huPBL-SCID, huPBMC-SCID) providing a semi-functional human immune system with human effector cells and Fc receptors. In such a model, an antigen challenge (such as tetanus toxoid) activates the B cells to differentiate into plasma cells and secrete immunoglobulins, thus reconstituting antigen specific humoral immunity. Therefore, a dual targeting immunoglobulin disclosed herein that specifically binds to IgE and FcγRIIb on B cells may be tested to examine the ability to specifically inhibit B cell differentiation. Such experimentation may provide meaningful data for determination of the potential of said immunoglobulin to be used as a therapeutic. Other organisms, e.g., mammals, may also be used for testing. For example, because of their genetic similarity to humans, monkeys can be suitable therapeutic models, and thus may be used to test the efficacy, toxicity, pharmacokinetics, or other property of the immunoglobulins disclosed herein. Tests of the immunoglobulins disclosed herein in humans are ultimately required for approval as drugs, and thus of course these experiments are contemplated. Thus the immunoglobulins disclosed herein may be tested in humans to determine their therapeutic efficacy, toxicity, pharmacokinetics, and/or other clinical properties.

[0297] The molecules disclosed herein may confer superior performance on Fc-containing therapeutics in animal models or in humans. The receptor binding profiles of such immunoglobulins, as described in this specification, may, for example, be selected to increase the potency of cytotoxic drugs or to target specific effector functions or effector cells to improve the selectivity of the drug's action. Further, receptor binding profiles can be selected that may reduce some or all effector functions thereby reducing the side-effects or toxicity of such Fc-containing drug. For example, an immunoglobulin with reduced binding to FcγRIIIa, FcγRI and FcγRIIa can be selected to eliminate most cell-mediated effector function, or an immunoglobulin with reduced binding to C1q may be selected to limit complement-mediated effector functions. In some contexts, such effector functions are known to have potential toxic effects. Therefore eliminating them may increase the safety of the Fc-bearing drug and such improved safety may be characterized in animal models. In some contexts, such effector functions are known to mediate the desirable therapeutic activity. Therefore enhancing them may increase the activity or potency of the Fc-bearing drug and such improved activity or potency may be characterized in animal models.

[0298] In some embodiments, molecules disclosed herein may be assessed for efficacy in clinically relevant animal models of various human diseases. In many cases, relevant models include various transgenic animals for specific antigens and receptors.

[0299] Relevant transgenic models such as those that express human Fc receptors (e.g., CD32b) could be used to evaluate and test immunoglobulins and Fc-fusions in their efficacy. The evaluation of molecules by the introduction of human genes that directly or indirectly mediate effector function in mice or other rodents may enable physiological studies of efficacy in autoimmune disorders (including SLE, RA and MS). Human Fc receptors such as FcγRIIb may possess polymorphisms such as that in gene promoter (−343 from G to C) or transmembrane domain of the receptor 187 I or T which would further enable the introduction of specific and combinations of human polymorphisms into rodents. The various studies involving polymorphism-specific FcRs is not limited to this section, however encompasses all discussions and applications of FcRs in general as specified in throughout this application. Immunoglobulins disclosed herein may confer superior activity on Fc-containing drugs in such transgenic models, in particular variants with binding profiles optimized for human FcγRIIb mediated activity may show superior activity in transgenic CD32b mice. Similar improvements in efficacy in mice transgenic for the other human Fc receptors, e.g. FcγRIIa, FcγRI, etc., may be observed for molecules with binding profiles optimized for the respective receptors. Mice transgenic for multiple human receptors would show improved activity for immunoglobulins with binding profiles optimized for the corresponding multiple receptors.

[0300] Because of the difficulties and ambiguities associated with using animal models to characterize the potential efficacy of candidate therapeutic antibodies in a human patient, some variant polypeptides disclosed herein may find utility as proxies for assessing potential in-human efficacy. Such proxy molecules may mimic—in the animal system—the FcR and/or complement biology of a corresponding candidate human immunoglobulin. This mimicry is most likely to be manifested by relative association affinities between specific immunoglobulins and animal vs. human receptors. For example, if one were using a mouse model to assess the potential in-human efficacy of an Fc variant that has reduced affinity for the inhibitory human FcγRIIb, an appropriate proxy variant would have reduced affinity for mouse FcγRII. It should also be noted that the proxy Fc variants could be created in the context of a human Fc variant, an animal Fc variant, or both.

[0301] In one embodiment, the testing of molecules may include study of efficacy in primates (e.g. cynomolgus monkey model) to facilitate the evaluation of depletion of specific target cells harboring the target antigen. Additional primate models include but are not limited to use of the rhesus monkey to assess Fc polypeptides in therapeutic studies of autoimmune, transplantation and cancer.

[0302] Toxicity studies are performed to determine antibody or Fc-fusion related-effects that cannot be evaluated in standard pharmacology profiles, or occur only after repeated administration of the agent. Most toxicity tests are performed in two species—a rodent and a non-rodent—to ensure that any unexpected adverse effects are not overlooked before new therapeutic entities are introduced into man. In general, these models may measure a variety of toxicities including genotoxicity, chronic toxicity, immunogenicity, reproductive/developmental toxicity and carcinogenicity. Included within the aforementioned parameters are standard measurement of food consumption, bodyweight, antibody formation, clinical chemistry, and macro- and microscopic examination of standard organs/tissues (e.g. cardiotoxicity). Additional parameters of measurement are injection site trauma and the measurement of neutralizing antibodies, if any. Traditionally, monoclonal antibody therapeutics, naked or conjugated, are evaluated for cross-reactivity with normal tissues, immunogenicity/antibody production, conjugate or linker toxicity and “bystander” toxicity of radiolabelled species. Nonetheless, such studies may have to be individualized to address specific concerns and following the guidance set by ICH S6 (Safety studies for biotechnological products, also noted above). As such, the general principles are that the products are sufficiently well characterized, impurities/contaminants have been removed, that the test material is comparable throughout development, that GLP compliance is maintained.

[0303] The pharmacokinetics (PK) of the molecules disclosed herein may be studied in a variety of animal systems, with the most relevant being non-human primates such as the cynomolgus and rhesus monkeys. Single or repeated i.v./s.c. administrations over a dose range of 6000-fold (0.05-300 mg/kg) can be evaluated for half-life (days to weeks) using plasma concentration and clearance. Volume of distribution at a steady state and level of systemic absorbance can also be measured. Examples of such parameters of measurement generally include maximum observed plasma concentration (Cmax), the time to reach Cmax (Tmax), the area under the plasma concentration-time curve from time 0 to infinity [AUC(0-inf] and apparent elimination half-life (T1/2). Additional measured parameters could include compartmental analysis of concentration-time data obtained following i.v. administration and bioavailability.

[0304] The molecules disclosed herein may confer superior pharmacokinetics on Fc-containing therapeutics in animal systems or in humans. For example, increased binding to FcRn may increase the half-life and exposure of the Fc-containing drug. Alternatively, decreased binding to FcRn may decrease the half-life and exposure of the Fc-containing drug in cases where reduced exposure is favorable such as when such drug has side-effects.

[0305] It is known in the art that the array of Fc receptors is differentially expressed on various immune cell types, as well as in different tissues. Differential tissue distribution of Fc receptors may ultimately have an impact on the pharmacodynamic (PD) and pharmacokinetic (PK) properties of molecules disclosed herein. Because molecules of the present invention have varying affinities for the array of Fc receptors, further screening of the polypeptides for PD and/or PK properties may be extremely useful for defining the optimal balance of PD, PK, and therapeutic efficacy conferred by each candidate polypeptide.

[0306] Pharmacodynamic studies may include, but are not limited to, targeting specific cells or blocking signaling mechanisms, measuring inhibition of antigen-specific antibodies etc. The molecules disclosed herein may target particular effector cell populations and thereby direct Fc-containing drugs to induce certain activities to improve potency or to increase penetration into a particularly favorable physiological compartment. For example, neutrophil activity and localization can be targeted by an molecule that targets FcγRIIIb. Such pharmacodynamic effects may be demonstrated in animal models or in humans.

[0307] Once made the molecules as described herein find use in a variety of methods. In a preferred embodiment the method includes contacting a cell that coexpresses IgE and FcγRIIb with a molecule such that both IgE and FcγRIIb are bound by the molecule and the cell is inhibited. By “inhibited” in this context is meant that the molecule is preventing or reducing activation and/or proliferation of IgE+ B cells.

[0308] The molecules disclosed herein may find use in a wide range of products. In one embodiment a molecule disclosed herein is a therapeutic, a diagnostic, or a research reagent. The molecules may find use in a composition that is monoclonal or polyclonal. The molecules disclosed herein may be used for therapeutic purposes. As will be appreciated by those in the art, the molecules disclosed herein may be used for any therapeutic purpose that antibodies, and the like may be used for. The molecules may be administered to a patient to treat disorders including but not limited to autoimmune and inflammatory diseases, infectious diseases, and cancer.

[0309] A “patient” for the purposes disclosed herein includes both humans and other animals, e.g., other mammals. Thus the molecules disclosed herein have both human therapy and veterinary applications. The term “treatment” or “treating” as disclosed herein is meant to include therapeutic treatment, as well as prophylactic, or suppressive measures for a disease or disorder. Thus, for example, successful administration of an molecule prior to onset of the disease results in treatment of the disease. As another example, successful administration of an optimized molecule after clinical manifestation of the disease to combat the symptoms of the disease comprises treatment of the disease. “Treatment” and “treating” also encompasses administration of an optimized immunoglobulin after the appearance of the disease in order to eradicate the disease. Successful administration of an agent after onset and after clinical symptoms have developed, with possible abatement of clinical symptoms and perhaps amelioration of the disease, comprises treatment of the disease. Those “in need of treatment” include mammals already having the disease or disorder, as well as those prone to having the disease or disorder, including those in which the disease or disorder is to be prevented.

[0310] In one embodiment, a molecule disclosed herein is administered to a patient having a disease involving inappropriate expression of a protein or other molecule. Within the scope disclosed herein this is meant to include diseases and disorders characterized by aberrant proteins, due for example to alterations in the amount of a protein present, protein localization, posttranslational modification, conformational state, the presence of a mutant or pathogen protein, etc. Similarly, the disease or disorder may be characterized by alterations molecules including but not limited to polysaccharides and gangliosides. An overabundance may be due to any cause, including but not limited to overexpression at the molecular level, prolonged or accumulated appearance at the site of action, or increased activity of a protein relative to normal. Included within this definition are diseases and disorders characterized by a reduction of a protein. This reduction may be due to any cause, including but not limited to reduced expression at the molecular level, shortened or reduced appearance at the site of action, mutant forms of a protein, or decreased activity of a protein relative to normal. Such an overabundance or reduction of a protein can be measured relative to normal expression, appearance, or activity of a protein, and said measurement may play an important role in the development and/or clinical testing of the immunoglobulins disclosed herein.

[0311] Disclosed herein are novel methods of treating IgE-mediated disorders, e.g., food and environmental allergies and allergic asthma. In preferred embodiments, allergic diseases that may be treated by the products and methods of the invention include allergic and atopic asthma, atopic dermatitis and eczema, allergic rhinitis, allergic conjunctivitis and rhinoconjunctivitis, allergic encephalomyelitis, allergic rhinitis, allergic vasculitis, and anaphylactic shock. Environmental and food allergies that may be treated include allergies to dustmite, cockroach, cat and other animals, pollen (including ragweed, Bermuda grass, Russian thistle, oak, rye, and others), molds and fungi (e.g., Alternaria alternata, Aspergillus and others), latex, insect stings (bee, wasp, and others), penicillin and other drugs, strawberries and other fruits and vegetables, peanuts, soy, and other legumes, walnuts and other treenuts, shellfish and other seafood, milk and other dairy products, wheat and other grains, and eggs. Indeed, any food allergen, aeroallergen, occupational allergen, or other IgE-mediated environmental allergen may be treated by a therapeutic amount of the products disclosed in this invention. For examples of common allergens, see Arbes et al., Prevalences of positive skin test responses to 10 common allergens in the US population: Results from the Third National Health and Nutrition Examination Survey, Clinical Gastroenterology 116(2), 377-383 (2005).

[0312] Also disclosed are diagnostic tests to identify patients who are likely to show a favorable clinical response to a molecule disclosed herein, or who are likely to exhibit a significantly better response when treated with an molecule disclosed herein versus one or more currently used therapeutics. Any of a number of methods for determining FcγR polymorphisms in humans known in the art may be used. Furthermore, also disclosed are prognostic tests performed on clinical samples such as blood and tissue samples. Such tests may assay for activity, regardless of mechanism. Such information may be used to identify patients for inclusion or exclusion in clinical trials, or to inform decisions regarding appropriate dosages and treatment regemins. Such information may also be used to select a drug that contains a particular molecule that shows superior activity in such assay.

[0313] Pharmaceutical compositions are contemplated wherein an molecule disclosed herein and one or more therapeutically active agents are formulated. Formulations of the molecules disclosed herein are prepared for storage by mixing said immunoglobulin having the desired degree of purity with optional pharmaceutically acceptable carriers, excipients or stabilizers (Remington's Pharmaceutical Sciences 16th edition, Osol, A. Ed., 1980, incorporated entirely by reference), in the form of lyophilized formulations or aqueous solutions. Acceptable carriers, excipients, or stabilizers are nontoxic to recipients at the dosages and concentrations employed, and include buffers such as phosphate, citrate, acetate, and other organic acids; antioxidants including ascorbic acid and methionine; preservatives (such as octadecyldimethylbenzyl ammonium chloride; hexamethonium chloride; benzalkonium chloride, benzethonium chloride; phenol, butyl orbenzyl alcohol; alkyl parabens such as methyl or propyl paraben; catechol; resorcinol; cyclohexanol; 3-pentanol; and m-cresol); low molecular weight (less than about 10 residues) polypeptides; proteins, such as serum albumin, gelatin, or immunoglobulins; hydrophilic polymers such as polyvinylpyrrolidone; amino acids such as glycine, glutamine, asparagine, histidine, arginine, or lysine; monosaccharides, disaccharides, and other carbohydrates including glucose, mannose, or dextrins; chelating agents such as EDTA; sugars such as sucrose, mannitol, trehalose or sorbitol; sweeteners and other flavoring agents; fillers such as microcrystalline cellulose, lactose, corn and other starches; binding agents; additives; coloring agents; salt-forming counter-ions such as sodium; metal complexes (e.g. Zn-protein complexes); and/or non-ionic surfactants such as TWEEN™, PLURONICS™ or polyethylene glycol (PEG). In one embodiment, the pharmaceutical composition that comprises the immunoglobulin disclosed herein may be in a water-soluble form, such as being present as pharmaceutically acceptable salts, which is meant to include both acid and base addition salts. “Pharmaceutically acceptable acid addition salt” refers to those salts that retain the biological effectiveness of the free bases and that are not biologically or otherwise undesirable, formed with inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid and the like, and organic acids such as acetic acid, propionic acid, glycolic acid, pyruvic acid, oxalic acid, maleic acid, malonic acid, succinic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, salicylic acid and the like. “Pharmaceutically acceptable base addition salts” include those derived from inorganic bases such as sodium, potassium, lithium, ammonium, calcium, magnesium, iron, zinc, copper, manganese, aluminum salts and the like. Some embodiments include at least one of the ammonium, potassium, sodium, calcium, and magnesium salts. Salts derived from pharmaceutically acceptable organic non-toxic bases include salts of primary, secondary, and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines and basic ion exchange resins, such as isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, and ethanolamine. The formulations to be used for in vivo administration may be sterile. This is readily accomplished by filtration through sterile filtration membranes or other methods.

[0314] The molecules disclosed herein may also be formulated as immunoliposomes. A liposome is a small vesicle comprising various types of lipids, phospholipids and/or surfactant that is useful for delivery of a therapeutic agent to a mammal. Liposomes containing the immunoglobulin are prepared by methods known in the art. The components of the liposome are commonly arranged in a bilayer formation, similar to the lipid arrangement of biological membranes. Particularly useful liposomes can be generated by the reverse phase evaporation method with a lipid composition comprising phosphatidylcholine, cholesterol and PEG-derivatized phosphatidylethanolamine (PEG-PE). Liposomes are extruded through filters of defined pore size to yield liposomes with the desired diameter.

[0315] The molecule and other therapeutically active agents may also be entrapped in microcapsules prepared by methods including but not limited to coacervation techniques, interfacial polymerization (for example using hydroxymethylcellulose or gelatin-microcapsules, or poly-(methylmethacylate) microcapsules), colloidal drug delivery systems (for example, liposomes, albumin microspheres, microemulsions, nano-particles and nanocapsules), and macroemulsions. Such techniques are disclosed in Remington's Pharmaceutical Sciences 16th edition, Osol, A. Ed., 1980, incorporated entirely by reference. Sustained-release preparations may be prepared. Suitable examples of sustained-release preparations include semipermeable matrices of solid hydrophobic polymer, which matrices are in the form of shaped articles, e.g. films, or microcapsules. Examples of sustained-release matrices include polyesters, hydrogels (for example poly(2-hydroxyethyl-methacrylate), or poly(vinylalcohol)), polylactides, copolymers of L-glutamic acid and gamma ethyl-L-glutamate, non-degradable ethylene-vinyl acetate, degradable lactic acid-glycolic acid copolymers such as the Lupron Depot® (which are injectable microspheres composed of lactic acid-glycolic acid copolymer and leuprolide acetate), poly-D-(−)-3-hydroxybutyric acid, and ProLease® (commercially available from Alkermes), which is a microsphere-based delivery system composed of the desired bioactive molecule incorporated into a matrix of poly-DL-lactide-co-glycolide (PLG).

[0316] Administration of the pharmaceutical composition comprising an molecule disclosed herein, e.g., in the form of a sterile aqueous solution, may be done in a variety of ways, including, but not limited to orally, subcutaneously, intravenously, intranasally, intraotically, transdermally, topically (e.g., gels, salves, lotions, creams, etc.), intraperitoneally, intramuscularly, intrapulmonary, vaginally, parenterally, rectally, or intraocularly. In some instances, for example for the treatment of wounds, inflammation, etc., the immunoglobulin may be directly applied as a solution or spray. As is known in the art, the pharmaceutical composition may be formulated accordingly depending upon the manner of introduction.

[0317] Subcutaneous administration may be used in circumstances where the patient may self-administer the pharmaceutical composition. Many protein therapeutics are not sufficiently potent to allow for formulation of a therapeutically effective dose in the maximum acceptable volume for subcutaneous administration. This problem may be addressed in part by the use of protein formulations comprising arginine-HCl, histidine, and polysorbate. Antibodies disclosed herein may be more amenable to subcutaneous administration due to, for example, increased potency, improved serum half-life, or enhanced solubility.

[0318] As is known in the art, protein therapeutics are often delivered by IV infusion or bolus. The antibodies disclosed herein may also be delivered using such methods. For example, administration may be by intravenous infusion with 0.9% sodium chloride as an infusion vehicle.

[0319] Pulmonary delivery may be accomplished using an inhaler or nebulizer and a formulation comprising an aerosolizing agent. For example, AERx® inhalable technology commercially available from Aradigm, or Inhance™ pulmonary delivery system commercially available from Nektar Therapeutics may be used. Antibodies disclosed herein may be more amenable to intrapulmonary delivery. FcRn is present in the lung, and may promote transport from the lung to the bloodstream (e.g. Syntonix WO 04004798, Bitonti et al. (2004) Proc. Nat. Acad. Sci. 101:9763-8, both incorporated entirely by reference). Accordingly, antibodies that bind FcRn more effectively in the lung or that are released more efficiently in the bloodstream may have improved bioavailability following intrapulmonary administration. Antibodies disclosed herein may also be more amenable to intrapulmonary administration due to, for example, improved solubility or altered isoelectric point.

[0320] Furthermore, molecules disclosed herein may be more amenable to oral delivery due to, for example, improved stability at gastric pH and increased resistance to proteolysis. Furthermore, FcRn appears to be expressed in the intestinal epithelia of adults, so antibodies disclosed herein with improved FcRn interaction profiles may show enhanced bioavailability following oral administration. FcRn mediated transport of antibodies may also occur at other mucus membranes such as those in the gastrointestinal, respiratory, and genital tracts.

[0321] In addition, any of a number of delivery systems are known in the art and may be used to administer the antibodies disclosed herein. Examples include, but are not limited to, encapsulation in liposomes, microparticles, microspheres (e.g., PLA/PGA microspheres), and the like. Alternatively, an implant of a porous, non-porous, or gelatinous material, including membranes or fibers, may be used. Sustained release systems may comprise a polymeric material or matrix such as polyesters, hydrogels, poly(vinylalcohol), polylactides, copolymers of L-glutamic acid and ethyl-L-gutamate, ethylene-vinyl acetate, lactic acid-glycolic acid copolymers such as the Lupron Depot®, and poly-D-(−)-3-hydroxyburyric acid. It is also possible to administer a nucleic acid encoding an immunoglobulin disclosed herein, for example by retroviral infection, direct injection, or coating with lipids, cell surface receptors, or other transfection agents. In all cases, controlled release systems may be used to release the immunoglobulin at or close to the desired location of action.

[0322] The dosing amounts and frequencies of administration are, in one embodiment, selected to be therapeutically or prophylactically effective. As is known in the art, adjustments for protein degradation, systemic versus localized delivery, and rate of new protease synthesis, as well as the age, body weight, general health, sex, diet, time of administration, drug interaction and the severity of the condition may be necessary, and will be ascertainable with routine experimentation by those skilled in the art.

[0323] The concentration of the therapeutically active molecule in the formulation may vary from about 0.1 to 100 weight %. In one embodiment, the concentration of the molecule is in the range of 0.003 to 1.0 molar. In order to treat a patient, a therapeutically effective dose of the immunoglobulin disclosed herein may be administered. By “therapeutically effective dose” herein is meant a dose that produces the effects for which it is administered. The exact dose will depend on the purpose of the treatment, and will be ascertainable by one skilled in the art using known techniques. Dosages may range from 0.0001 to 100 mg/kg of body weight or greater, for example 0.1, 1, 10, or 50 mg/kg of body weight. In one embodiment, dosages range from 1 to 10 mg/kg.

[0324] In some embodiments, only a single dose of the molecule is used. In other embodiments, multiple doses of the molecule are administered. The elapsed time between administrations may be less than 1 hour, about 1 hour, about 1-2 hours, about 2-3 hours, about 3-4 hours, about 6 hours, about 12 hours, about 24 hours, about 48 hours, about 2-4 days, about 4-6 days, about 1 week, about 2 weeks, or more than 2 weeks.

[0325] In other embodiments the molecules disclosed herein are administered in metronomic dosing regimes, either by continuous infusion or frequent administration without extended rest periods. Such metronomic administration may involve dosing at constant intervals without rest periods. Typically such regimens encompass chronic low-dose or continuous infusion for an extended period of time, for example 1-2 days, 1-2 weeks, 1-2 months, or up to 6 months or more. The use of lower doses may minimize side effects and the need for rest periods.

[0326] In certain embodiments the molecules disclosed herein and one or more other prophylactic or therapeutic agents are cyclically administered to the patient. Cycling therapy involves administration of a first agent at one time, a second agent at a second time, optionally additional agents at additional times, optionally a rest period, and then repeating this sequence of administration one or more times. The number of cycles is typically from 2-10. Cycling therapy may reduce the development of resistance to one or more agents, may minimize side effects, or may improve treatment efficacy.

[0327] The molecules disclosed herein may be administered concomitantly with one or more other therapeutic regimens or agents. Additional therapeutic regimes or agents may be used to treat the same disease, to treat an accompanying complication, or may be used to improve the efficacy or safety of the immunoglobulin

[0328] Particularly preferred co-therapies include those that are approved or are being clinically evaluated for the treatment of IgE-mediated disorders such as allergies and asthma. In particular, the therapeutic compositions of the invention may be used in combination with anti-inflammatories such as corticosteroids, and/or brochodilators such as inhaled β2-agonists, the two major groups of medications. Inhaled corticosteroids include fluticasone, budesonide, flunisolide, mometasone, triamcinolone, and beclomethasone, whereas oral corticosteroids include prednisone, methylprednisolone, and prednisolone. Other steroids include glucocorticoids, dexamethasone, cortisone, hydroxycortisone, azulfidineicosanoids such as prostaglandins, thromboxanes, and leukotrienes, as well as topical steroids such as anthralin, calcipotriene, clobetasol, and tazarotene. Bronchodilators increase the diameter of the air passages and ease the flow to and from the lungs. Brochodilators that may be combined with the therapies of the invention include short-acting bronchodilators such as metaproterenol, ephedrine, terbutaline, and albuterol, and long-acting bronchodilators such as salmeterol, metaproterenol, and theophylline.

[0329] The therapies of the invention may be combined with non-steroidal anti-inflammatory drugs (NSAIDs) such as asprin, ibuprofen, celecoxib, diclofenac, etodolac, fenoprofen, indomethacin, ketoralac, oxaprozin, nabumentone, sulindac, tolmentin, rofecoxib, naproxen, ketoprofen, and nabumetone. Co-therapies may include antihistamines such as loratadine, fexofenadine, cetirizine, diphenhydramine, chlorpheniramine maleate, clemastine, and azelastine. Co-therapy may include cromoglycate, cromolyn sodium, and nedrocromil, as well as decongestants, spray or oral, such as oxymetazoline, phenylephrine, and pseudoephedrine. The therapies of the invention may be combined with a class of anti-inflammatories called leukotriene-receptor antagonists such as pranlukast, zafirlukast, and montelukast, and leukotriene-receptor synthesis-inhibitors such as zileuton.

[0330] The therapies of the invention may be combined with other immunotherapies, including allergy shots, as well as other antagonists of IgE or FcεRs. The therapies of the invention may be combined with antagonists of chemokines or cytokines, including but not limited to antibodies and Fc fusions, including but not limited to inhibitors of chemokines CCR3, CCR4, CCR8, and CRTH2, and CCR5, and inhibitors of cytokines IL-13, IL-4, IL-5, IL-6, IL-9, IL-10, IL-12, IL-15, IL-18, IL-19, IL-21, Class II family of cytokine receptors, IL-22, IL-23, IL-25, IL-27, IL-31, and IL-33. The therapies of the invention may be combined with modulators of adhesion, transcription factors, and/or intracellular signaling. For example, the immunoglobulins of the invention may be combined with modulators of NF-Kb, AP-1, GATA-3, Stat1, Stat-6, c-maf, NFATs, suppressors of cytokine signaling (SOCS), peroxisome proliferator-activated receptors (PPARs), MAP kinase, p38 MAPK, JNK, and sphingosine I-phosphate receptors. The therapies of the invention may be administered with suplatast tolilate, inhibitors of phosphodiesterase 4 (PDE4), calcium channel blockers, and heparin-like molecules. Possible co-therapies for the invention are described further in detail in Caramori et al., 2008, Journal of Occupational Medicine and Toxicology 3-S1-S6.

[0331] The therapies of the invention may also be used in conjunction with one or more antibiotics, anti-fungal agents, or antiviral agents. The antibodies disclosed herein may also be combined with other therapeutic regimens such as surgery.

[0332] Examples are provided below are for illustrative purposes only. These examples are not meant to constrain any embodiment disclosed herein to any particular application or theory of operation.

[0333] Immunoglobulin IgE is a central initiator and propagator of allergic response in affected tissue. IgE binds the high affinity receptor for IgE (FcεRI), a key receptor involved in immediate allergic manifestations that is expressed on a variety of effector cells, including mast cells, basophils, eosinophils, as well as other cell types. Cross-linking of FcεRI by immune-complexed IgE-allergen activates these cells, releasing chemical mediators such as histamine, prostaglandins, and leukotrienes, which may lead to the development of a type I hypersensitivity reaction. The approved monoclonal antibody Omalizumab (Xolair) neutralizes IgE by binding to it and blocking engagement with FcεR's. Omalizumab reduces bioactive IgE through sequestration, attenuating the amount of antigen-specific IgE that can bind to and sensitize tissue mast cells and basophils. This neutralization of free circulating IgE, in turn, leads to a decrease in symptoms of allergic diseases. Interestingly, serum IgE levels increase after start of therapy because of omalizumab-IgE complex formation and may remain high up to a year after stopping therapy. Consequently, this issue may lead to false-negatives on diagnostic tests and therefore IgE levels must be routinely checked.

[0334] A novel approach to targeting the IgE pathway involves not only blocking free circulating IgE from engaging FcεRs on effector cells, but targeting the source of IgE production. IgE is secreted by IgE-producing plasma cells located in lymph nodes draining the site of antigen entry or locally at the sites of allergic reactions. IgE-producing plasma cells are differentiated from IgE+ B cells. Class switching of B cells to IgE production is induced by two separate signals, both of which can be provided by TH2 cells.

[0335] There are two forms of immunoglobulins: the secreted and the membrane-anchored form. The membrane-anchored form differs from the secreted form in that the former has a membrane-anchoring peptide extending from the C terminus of the heavy-chain. Membrane-anchored immunoglobulin on B-cells, also referred to as the B cell receptor (BCR) complex, is critical for B-cell functions. It can transduce signals for resting B cells to differentiate into activated lymphoblasts and Ig-secreting plasma cells.

[0336] Differentiated B cells expressing membrane-anchored IgE, referred to here as mIgE+ B cells, possess a natural negatively regulating feedback mechanism—the inhibitory Fc receptor FcγRIIb. FcγRIIb is expressed on a variety of immune cells, including B cells, dendritic cells, monocytes, and macrophages, where it plays a critical role in immune regulation. In its normal role on B cells, FcγRIIb serves as a feedback mechanism to modulate B cell activation through the B cell receptor (BCR). Engagement of BCR by immune complexed antigen on mature B cells activates an intracellular signaling cascade, including calcium mobilization, which leads to cell proliferation and differentiation. However, as IgG antibodies with specificity to the antigen are produced, the associated immune complexes (ICs) can crosslink the BCR with FcγRIIb, whereupon the activation of BCR is inhibited by engagement of FcγRIIb and associated intracellular signaling pathways that interfere with the downstream pathways of BCR activation. The expression of FcγRIIb on the surface of mIgE+ B cells, which use mIgE as their BCR, serves as a negative regulator of these cell types.

[0337] A novel strategy for inhibiting IgE-mediated disease, illustrated in FIG. 1, is to inhibit IgE+ B cells (i.e. B cells expressing membrane anchored IgE) by coengaging membrane anchored IgE and the inhibitory receptor FcγRIIb. In B cells that have class-switched to express IgE, mIgE serves as the BCR (referred to herein as mIgE BCR). This approach would potentially mimic the natural biological mechanism of immune complex-mediated suppression of B cell activation, thereby preventing differentiation into IgE-producing plasma cells. IgE-producing plasma cells reside in the bone marrow and probably have a life span of several weeks to several months. Since new IgE-secreting plasma cells go through mIgE-expressing B-cell stages during differentiation, if their generation is abrogated by inhibiting their mIgE+ B cell precursors with this anti-IgE treatment, the existing plasma cells will die off within weeks to months, and thus the production of IgE will also gradually abate. Importantly, inhibition of IgE+ memory B cells, which bear mIgE, would also be inhibited by anti-IgE immunoglobulins that coengage FcγRIIb with high affinity. If this occurs, therapy may have long-term impact on the fundamental disease.

[0338] Under physiological conditions, bridging of the BCR with FcγRIIb and subsequent B cell suppression occurs via immune complexes of IgGs and cognate antigen. The design strategy was to reproduce this effect using a single crosslinking antibody. Human IgG binds human FcγRIIb with weak affinity (greater than 100 nM for IgG1), and FcγRIIb-mediated inhibition occurs in response to immune-complexed but not monomeric IgG. It was reasoned that high affinity to this receptor (less than 100 nM) would be required for maximal inhibition of B cell activation. In order to enhance the inhibitory activity of the anti-IgE antibodies of the invention, the Fc region was engineered with variants that improve binding to FcγRIIb. Engineered Fc variants have been described that bind to FcγRIIb with improved affinity relative to native IgG1 (U.S. Ser. No. 12/156,183, filed May 30, 2008, entitled “Methods and Compositions for Inhibiting CD32b Expressing cells”, herein incorporated expressly by reference).

[0339] Variants were originally generated in the context of an antibody targeting the antigen CD19, a regulatory component of the BCR coreceptor complex. The Fv region of this antibody is a humanized and affinity matured version of antibody 4G7, and is referred to herein as HuAM4G7. The Fv genes for this antibody were subcloned into the mammalian expression vector pTT5 (National Research Council Canada). Mutations in the Fc domain were introduced using site-directed mutagenesis (QuikChange, Stratagene, Cedar Creek, Tex.). In addition, control knock out variants with ablated affinity for Fc receptors were generated that comprise the substitutions G236R and L328R (G236R/L328R). This variant is referred to as Fc-KO or Fc knockout. Heavy and light chain constructs were cotransfected into HEK293E cells for expression, and antibodies were purified using protein A affinity chromatography (Pierce Biotechnology, Rockford, Ill.).

[0340] Recombinant human FcγRIIb protein for binding studies was obtained from R&D Systems (Minneapolis, Minn.). Genes encoding FcγRIIa and FcγRIIIa receptor proteins were obtained from the Mammalian Gene Collection (ATCC), and subcloned into pTT5 vector (National Research Council Canada) containing 6×His tags. Allelic forms of the receptors (H131 and R131 for FcγRIIa and V158 and F158 for FcγRIIIa) were generated using QuikChange mutagenesis. Vectors encoding the receptors were transfected into HEK293T cells, and proteins were purified using nickel affinity chromatography.

[0341] Variants were tested for receptor affinity using Biacore technology, also referred to as Biacore herein, a surface plasmon resonance (SPR) based technology for studying biomolecular interactions in real time. SPR measurements were performed using a Biacore 3000 instrument (Biacore, Piscataway, N.J.). A protein NG (Pierce Biotechnology) CM5 biosensor chip (Biacore) was generated using a standard primary amine coupling protocol. All measurements were performed using HBS-EP buffer (10 mM HEPES pH 7.4, 0.15 M NaCl, 3 mM EDTA, 0.005% vol/vol surfactant P20, Biacore). Antibodies at 20 nM or 50 nM in HBS-EP buffer were immobilized on the protein A/G surface and FcγRs were injected. After each cycle, the surface was regenerated by injecting glycine buffer (10 mM, pH 1.5). Data were processed by zeroing time and response before the injection of FcγR and by subtracting appropriate nonspecific signals (response of reference channel and injection of running buffer). Kinetic analyses were performed by global fitting of binding data with a 1:1 Langmuir binding model using BIAevaluation software (Biacore).

[0342] A representative set of sensorgrams for binding of select variant anti-CD19 antibodies to FcγRIIb is shown in FIG. 2. The affinities of all variants and WT (native) IgG1 to all of the FcγRs, obtained from fits of the Biacore binding data, are plotted in FIG. 3 and provided numerically in FIG. 4. Whereas WT IgG1 Fc binds with FcγRIIb with μM affinity (KD=1.8 μM in FIG. 4), a number of variants, for example G236D/S267E, S239D/S267E, and S267E/L328F, have been engineered that bind the inhibitory receptor more tightly. The S239D/I332E variant, as described in U.S. Ser. No. 11/124,620, also has improved affinity for the activating receptors FcγRIIa and FcγRIIIa, and therefore is capable of mediated enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) and phagocytosis (ADCP). The G236R/L328R variant, also referred to Fc-knockout or Fc-KO, lacks binding to the Fc receptors, and is used as a control in the experiments described herein.

[0343] Select variants were constructed in antibodies that target IgE. The heavy and light chain variable regions (VH and VL) of anti-IgE antibodies are provided in FIG. 5. Omalizumab is a humanized antibody that is currently approved for the treatment of allergic asthma, and is marketed under the name Xolair. MaE11 is the murine precursor of Omalizumab. H1L1_MaE11 is a novel humanized version of MaE11. Genes encoding the heavy and light VH and VL domains of these anti-IgE antibodies were synthesized commercially (Blue Heron Biotechnologies). Also synthesized were the variable region VH and VL genes of the anti-respiratory syncytial virus (RSV) antibody motavizumab, used in the experiments described herein as a negative control. VL genes were subcloned into the mammalian expression vector pTT5 (NRC-BRI, Canada) encoding the Ckappa constant chain. VH genes were subcloned into the pTT5 vector encoding native IgG1 and variant constant chains. Amino acid sequences of select constant chains are provided in FIG. 6. All DNA was sequenced to confirm the fidelity of the sequences. The amino acid sequences of the full length heavy and light chains of select antibodies are provided in FIG. 7. As shown in FIG. 9 and discussed in further detail herein, H1L1_MaE11 shows higher affinity to IgE than Omalizumab.

[0344] Plasmids containing heavy and light chain genes were co-transfected into HEK293E cells using lipofectamine (Invitrogen) and grown in FreeStyle 293 media (Invitrogen). After 5 days of growth, the antibodies were purified from the culture supernatant by protein A affinity using MabSelect resin (GE Healthcare).

[0345] Variant and native IgG1 anti-IgE antibodies were tested for binding to IgE and to FcγRIIb using Biacore. DNA encoding the Fc region of IgE, which contains the binding site for the anti-IgE antibodies used, was sythesized (Blue Heron Biotechnologies) and subcloned into the pTT5 vector. IgE Fc was expressed in 293E cells and purified using protein A as described above. SPR measurements were performed using the protein A/antibody capture method described above, except that analyte was either FcγRIIb or the Fc region of IgE. Data acquisition and fitting are as described above. FIG. 8 provides the resulting equilibrium binding constants (KDs) obtained from these binding experiments, as well as the fold affinity relative to native IgG1 for binding to FcγRIIb. FIG. 9 shows plots of these data. The results confirm the high of affinity of the antibodies for IgE, and that the S267E/L328F variant improves binding to FcγRIIb over two orders of magnitude, consistent with previous results.

[0346] The use of particular variants, for example S267E/L328F and S239D/I332E, are meant here as proof of concept for the mechanism as described herein, and are not meant to constrain the invention to their particular use. The data provided in U.S. Ser. No. 12/156,183 and U.S. Ser. No. 11/124,620 indicate that a number of engineered variants, at specific Fc positions, provide the targeted properties. Substitutions to enhance FcγR affinity, in particular to FcγRIIb, include: 234, 235, 236, 237, 239, 266, 267, 268, 325, 326, 327, 328, and 332. In some embodiments, substitutions are made to at least one or more of the nonlimiting following positions to enhance affinity to FcγRIIb: 235, 236, 239, 266, 267, 268, and 328.

[0347] Nonlimiting combinations of positions for making substitutions to enhance affinity to FcγRIIb include: 234/239, 234/267, 234/328, 235/236, 235/239, 235/267, 235/268, 235/328, 236/239, 236/267, 236/268, 236/328, 237/267, 239/267, 239/268, 239/327, 239/328, 239/332, 266/267, 267/268, 267/325, 267/327, 267/328, 267/332, 268/327, 268/328, 268/332, 326/328, 327/328, and 328/332. In some embodiments, combinations of positions for making substitutions to enhance affinity to FcγRIIb include, but are not limited to: 235/267, 236/267, 239/268, 239/267, 267/268, and 267/328.

[0348] Substitutions for enhancing affinity to FcγRIIb include: 234D, 234E, 234W, 235D, 235F, 235R, 235Y, 236D, 236N, 237D, 237N, 239D, 239E, 266M, 267D, S267E, 268D, 268E, 327D, 327E, L328F, 328W, 328Y, and 332E. In some embodiments, combination of positions for making substitutions for enhancing affinity to FcγRIIb include, but are not limited to: 235Y, 236D, 239D, 266M, S267E, 268D, 268E, L328F, 328W, and 328Y.

[0349] Combinations of substitutions for enhancing affinity to FcγRIIb include: L234D/S267E, L234E/S267E, L234F/S267E, L234E/L328F, L234W/S239D, L234W/S239E, L234W/S267E, L234W/L328Y, L235D/S267E, L235D/L328F, L235F/S239D, L235F/S267E, L235F/L328Y, L235Y/G236D, L235Y/S239D, L235Y/S267D, L235Y/S267E, L235Y/H268E, L235Y/L328F, G236D/S239D, G236D/S267E, G236D/H268E, G236D/L328F, G236N/S267E, G237D/S267E, G237N/S267E, S239D/S267D, S239D/S267E, S239D/H268D, S239D/H268E, S239D/A327D, S239D/L328F, S239D/L328W, S239D/L328Y, S239D/I332E, S239E/S267E, V266M/S267E, S267D/H268E, S267E/H268D, S267E/H268E, S267E/N325L, S267E/A327D, S267E/A327E, S267E/L328F, S267E/L3281, S267E/L328Y, S267E/I332E, H268D/A327D, H268D/L328F, H268D/L328W, H268D/L328Y, H268D/I332E, H268E/L328F, H268E/L328Y, A327D/L328Y, L328F/I332E, L328W/I332E, and L328Y/I332E. In some embodiments, combinations of substitutions for enhancing affinity to FcγRIIb include, but are not limited to: L235Y/S267E, G236D/S267E, S239D/H268D, S239D/S267E, S267E/H268D, S267E/H268E, and S267E/L328F.

[0350] An enzyme-linked immunosorbent assay (ELISA) was established to detect IgE. Flat bottom plates were prepared by coating with pH 9.4 Na Bicarbonate buffer, followed by adherence with anti-IgE capture antibodies at 10 ug/ml overnight in pH 9.4 (0.1 M NaBicarbonate buffer). After overnight, the plate was blocked with 3% BSA/PBS, and serial dilutions of IgE (from a human IgE ELISA kit, Bethyl Laboratories) was added 3× to 1 ug/ml. After 3 hours, plates were washed 3× (200 μl) with TTBS, and bound IgE was measured. HRP-conjugated goat polyclonal anti-human IgE antibody (Bethyl Laboratories) was added at (1:5000) for 1 hour in 1% BSA/PBS. Samples were washed 3× and IgE was detected with TMB peroxidase substrate (KPL, Inc 50-76-00). Reactions were stopped with 50 μl 2N H2SO₄ and read at 450 nm.

[0351] FIG. 10 shows capture of IgE with various anti-human IgE antibodies, including a pool of three monoclonal anti-IgE antibodies (MabTech; 107/182/101), MaE11_IgG1_G236R/L328R, and Omalizumab_IgG1_G236R/L328R. The data show that the commercial anti-IgE antibody reagent (MabTech), Omalizumab, and its parent chimeric antibody MaE11 are able to capture IgE. In order to use this assay to detect IgE, it was necessary to determine whether MaE11 and omalizumab antibodies would interfere with IgE capture by the MabTech anti-IgE reagent. The assay was repeated as described above, and concentration of IgE from absorbance was calculated using a standard curve. FIG. 11 shows that anti-IgE antibody omalizumab_G236R/L328R does not compete with the MabTech anti-IgE antibody in the current ELISA protocol.

[0352] Fc variant anti-IgE antibodies were tested for their capacity to inhibit IgE+ B cells. Human PBMCs were induced to class switch to IgE producing B cells by adding 5 ng/ml interleukin-4 (IL-4) and 100 ng/ml anti-CD40 antibody (clone G28.5 IgG1). The anti-CD40 antibody is an agonist of CD40, and thus mimics the activity of the co-activator CD40L. Varying concentration of anti-IgE antibodies were added, and the samples were incubated for 12 days. ELISA plates were prepared and blocked as described above, using 5 ug/ml Mabtech anti-IgE as the capture antibody. 100 μl of the PBMC samples were added and incubated >3 hours, and then washed with TTBS 3× (200 μl). Antibody-HRP conjugated antibody was added and detected as described above. Absorbance at 450 nm was converted to IgE concentration using a standard curve. The results are shown in FIG. 12. Antibodies lacking FcγR binding (G236R/L328R variants) or having no specificity for IgE (Motavizumab anti-RSV antibody) had no effect on IgE production from differentiated B cells. In contrast, variant antibodies with greater affinity for FcγRIIb inhibited IgE production. These data suggest that co-engagement of surface IgE and the inhibitory FcγR receptor FcγRIIb inhibits class-switched B cells of that immunoglobulin type. Inhibition of IgE+ B cells reduces the number of IgE expressing plasma cells, which in turn reduces the amount of IgE detected. To evaluate the selectivity of this activity for IgE producing B cells, human IgG2 was measured from the same samples using an IgG2 ELISA (Bethyl Laboratories). FIG. 13 shows that IgG2 secretion was not inhibited, indicating that the inhibitory activity of anti-IgE antibodies with high FcγRIIb affinity is selective for IgE+ class-switched cells. Repeat of this experiment using variant versions of the approved anti-IgE antibody Omalizumab showed similar inhibitory results by the variant with high FcγRIIb affinity (FIG. 14).

[0353] The capacity of anti-IgE antibodies with high FcγRIIb affinity to inhibit IgE production was evaluated in the presence of mIgE BCR stimulation. The above assay was repeated, with class-switching to IgE promoted by IL-4 and a-CD40 agonist antibody, and in addition the B cells were activated using either anti-mu or anti-CD79b antibody. These antibodies cross-link the BCR, thereby providing a signal similar to immune-complexed antigen. Anti-mu antibody cross-links membrane-anchored IgM, and anti-CD79b cross-links CD79b, which is a signaling component of the BCR complex. PBMCs were incubated for 14 days with IL-4, a-CD40, and either anti-CD79b or anti-mu, and IgE was detected as described above. The results for anti-CD79b (FIG. 15) and anti-mu (FIG. 16) show that the anti-IgE antibodies with high affinity for FcγRIIb are capable of inhibiting IgE production when B cells are stimulated via BCR cross-linking.

[0354] An additional strategy for inhibiting IgE+ B cells is to deplete them. This may be carried out using an anti-IgE antibody that is enhanced for effector function. The variant S239D/I332E increases binding to activating receptor FcγRIIa and FcγRIIIa (FIG. 3 and FIG. 4), and thus improves ADCC and ADCP effector functions. The above B cell assay was carried out using a S239D/I332E variant of the anti-IgE antibody Omalizumab. PBMCs were incubated for 14 days with IL-4, a-CD40, and either anti-CD79b (FIG. 17) or anti-mu (FIG. 18), and IgE was detected as described above. The results (FIGS. 17 and 18) show that anti-IgE antibodies with optimized effector function are able to inhibit IgE production from class-switched IgE+ B cells.

[0355] The immunoglobulins disclosed herein were assessed using a huPBL-SCID mouse model as a proxy for therapeutic activity in humans. This study examined the capacity of the anti-IgE antibodies described here to inhibit B cell activity and plasma cell development in response to a common human allergen—dust mite protein Der p 1. In this method, human peripheral blood leukocytes (PBLs) from a blood donor with allergic response to Der p 1 were engrafted to immune-deficient SCID mice and treated with the native or variant anti-IgE antibodies. The mice were challenged with an antigen to stimulate an immune response, and production of immunoglobulins was measured to examine the course of B cell development into plasma cells.

[0356] Blood donors were screened for allergy to dust mite antigen based on the presence of anti-IgE antibodies against Der p 1. A donor with positive reactivity was leukapheresed to obtained peripheral blood mononuclear cells (PBMCs). The protocol for the study is provided in FIG. 20. One day prior to PBMC injection, mice were given intraperitoneal (i.p.) injections with 100 μl of anti-asialo GM antibody (Wako, Richmond, Va.) to deplete murine natural killer (NK) cells. The next day, mice were injected i.p. with 3×10⁷ PBLs in a 0.5 ml volume. After PBMC injection, mice were assigned to 5 different groups of mice with 7 mice in each group. On day 7 post PBMC injection, blood was collected from all mice via retro-orbital sinus/plexus (OSP) puncture for determination of human IgG and IgE levels by ELISA (ZeptoMetrix, Buffalo, N.Y.). Two days later (day 9), mice were injected i.p. with 10 mg/kg antibody or PBS. On day 11, mice were injected i.p. with 15 ug dustmite antigen Der p 1 (LoTox Natural Der p 1, Indoor Biotechnologies, Charlottesville, Va.). On day 23 (12 days post antigen vaccination), blood was collected from all mice for determination of human IgG and IgE antibodies. On the same day, mice received a second injection i.p. with 10 mg/kg antibody or PBS. Two days later (day 25), mice received a boost vaccination i.p. of 10 ug dustmite antigen Der p 1. On day 37 (12 days post antigen boost), blood was collected by OSP for human immunoglobulin determination. Human IgG and IgE concentrations were measured using ELISA methods similar to those described above.

[0357] The results are shown in FIGS. 20 and 21 for serum IgG and IgE levels respectively. Before the allergen challenge, the levels of human IgG and IgE antibodies were low in all the groups. After Der p 1 immunization, all groups showed high levels of human IgG, indicating a robust immune response by engrafted human B cells to either the vaccinated Der p 1 antigen or endogenous mouse antigens. In contrast to IgG response, the treatment groups differed significantly in their production of IgE antibodies. Omalizumab and the IgG1 version of H1 L1 MaE11 were equivalent to vehicle in their capacity to inhibit production of human IgE. However the FcγRIIb-enhanced (IIbE, S267E/L328F) version of H1 L1 MaE11 showed no detectable levels of human IgE. The Fc-KO (variant G236R/L328R) version of H1 L1 MaE11, which lacks binding to all FcγRs, showed an enhancement in human IgE production. This is possibly due to its ability to cross-link human mIgE and thus activate IgE+ B cells, yet its complete lack of FcγRIIb inhibitory or FcγRIIa/IIIa cytotoxic activities such as those possessed by the IgG1 and IIbE versions of the antibody. These in vivo data show that anti-IgE antibodies with high affinity for FcγRIIb are capable of inhibiting human IgE+ B cell activation and immunoglobulin secreting plasma cell differentiation, and thus support the potential of the immunoglobulins disclosed herein for treating IgE-mediated disorders.

[0358] XmAb7195 (anti-human IgE, S267E/L328F) was evaluated for its pharmacokinetics and pharmacodynamics (free and total IgE) in chimpanzees following a single intravenous dose of 5 mg/kg. Chimpanzees and humans have similar FcγRIIb structure at the critical binding region (Arginine at position 131, or 131-R), in contrast to macaques which do not have the relevant contact amino acid. The comparator antibody in this study was commercially available omalizumab (Xolair®. Genentech, USA), an anti-human IgE antibody with a wild type human IgG1 Fc domain.

[0359] The purpose of this study was two-fold. The first objective was to evaluate the pharmacokinetic behavior of XmAb7195 in chimpanzees. Sequence differences among primate species lead to significant differences in receptor affinities for XmAb7195. The receptor-mediated clearance of XmAb7195 may involve Fc-gamma receptors type II (a and b). PK experiments in other non-human primates have been performed, but may not be predictive since macaques do not have arginine at position 131 of the Fc gamma type II receptors. PK in chimpanzees, which have the appropriate genotype, may be more predictive of the PK/PD profile expected in human clinical studies. The second purpose of the study was to evaluate the pharmacodynamic effect of a single dose of XmAb7195 on the sequestration, production, and clearance of IgE. In each of these objectives, we used omalizumab as a comparator molecule in order to evaluate the effect that the engineered Fc had on PK/PD parameters.

[0360] The results of free drug concentrations as a function of time are presented in FIG. 22A. Notably, XmAb7195 has a shorter half-life of approximately 2 days compared to the approximately 11 days observed for omalizumab. Analysis of free and total IgE was undertaken on serum samples at each of the PK time points. Free IgE levels exhibited a rapid drop immediately after dosing. The nadir of free IgE concentrations for the omalizumab-treated chimps averaged approximately 50 ng/ml at one hour post dosing. XmAb7195 caused a more significant reduction of free IgE, reaching levels below the lower limit of quantitation (LLOQ) of 4 ng/ml almost immediately after dosing and remaining below the LLOQ up to day 10. (FIG. 22B) Omalizumab increased total IgE for a period of weeks, similar to its observed effects in humans. XmAb7195 caused a rapid disappearance of total IgE—reaching the LLOQ within 1 hour post-dosing and lasting for 10 days—followed by a gradual return to baseline levels over a period of weeks. FIG. 22C shows group mean total IgE levels versus time for chimpanzees treated with omalizumab or XmAb7195 (anti-IgE, S267E/L328F). The lower limit of quantification was 0.2 μg/ml.

[0361] Several anti-mouse IgE antibodies with different FcγRIIb-enhancing Fc substitutions were produced for comparison of their ability to modulate total IgE concentrations in vivo. The first, XENP8253, comprises the R1E4 Fv domain (anti-mouse IgE) and an Fc domain containing the S267E/L328F substitutions. The second, XENP8252, is a surrogate for omalizumab, comprising the R1E4 Fv domain with a native human IgG1 backbone. Additional Fc variants—S267E, G236D/S267E, and G236N/S267E were also characterized to examine the relationship between human FcγRIIb affinity and pharmacokinetics and pharmacodynamics.

[0362] A single 2 mg/kg dose of all anti-IgE antibodies sequestered serum IgE and reduced free IgE serum levels by several orders of magnitude within hours of the treatment. Their effect on total IgE, however, was very different. The omalizumab surrogate (XENP8252), which contains an unmodified IgG1 Fc domain, had no discernible effect on total IgE relative to the PBS control. In contrast, the high FcγRIIb affinity variant S267E/L328F reduced total IgE within hours, and caused sustained reduction of total IgE relative to both the PBS group and the XENP8252-treated mice. The extremely rapid onset of the total IgE reduction in this model system indicates (without being bound by theory) that anti-IgE antibodies with enhanced affinity for FcγRIIb increase the rate of drug:IgE complex clearance. This hypothesis is consistent with the observation that the S267E/L328F (IIbE) variant has reduced half-life (approximately 2.5 days) relative to the IgG1 antibody (XENP8252) (approximately 11 days). (FIG. 23). FIG. 24 shows serum total IgE concentration as a function of time in the human FcγRIIb transgenic mice treated with anti-mouse IgE antibodies. The lower limit of quantification of this IgE assay was 13 ng/ml.

[0363] The additional variant antibodies—S267E, G236D/S267E, and G236N/S267E, with FcγRIIb affinities intermediate between IgG1 and S267E/L328, have intermediate half-lives and intermediate effects on total IgE, revealing a direct relationship between FcγRIIb affinity and clearance rates of either antibody alone or antibody complexed with antigen. (See FIG. 25).

[0364] A hypothesis tested was that much of the in vivo accelerated clearance of antibody and antibody:IgE complexes is mediated by liver sinusoidal endothelial cells (LSEC). Anderson and colleagues (Ganesan et al., J Immunol 2012) published a study demonstrating that three quarters of mouse FcγRIIb is expressed in the liver, with 90% of it being expressed in LSEC. Moreover, the authors demonstrated that clearance of radiolabeled small immune complexes (SIC) is significantly impaired in an FcγRIIb knockout strain compared to wild-type mice.

[0365] An LSEC enrichment protocol was adopted from Katz et al, (Katz et al., (2004) J Immunol “Liver sinusoidal endothelial cells are insufficient to activate T cells,” 173(1): 230-235) for non-parenchymal cell isolation. Briefly, mouse liver was infused with 1 ml of 1% (w/v) collagenase D in 1×HBSS using syringe and needle. Then, the liver was quickly minced in 20 ml of 1% collagenase D and incubated at 37° C. for 20 minutes with stirring to keep the cells in suspension. The cell suspension was passed through a 100 μm cell strainer filter mesh and spun 3× at low speed (30×g, 10 minutes) to remove the bulk of parenchymal hepatocytes. The final enriched non-parenchymal liver cell pellet (300×g, 10 minutes) was washed twice with PBS (300×g, 10 minutes) and used in internalization assays.

[0366] FITC conjugated anti-IgE antibodies plus human IgE pre-formed IC were incubated with enriched LSEC's for 60 minutes at 37° C., washed with low pH “Acid” wash buffer (glycine, NaCl, pH=2.7) and stained with anti-CD146 and anti-CD45 antibodies. The internalized signal (FITC MFI) was quantified from CD146+CD45low LSEC's and MESF normalized values are plotted. As shown in FIG. 26, IgE complexes formed with the anti-IgE antibody containing the high Ilb affinity variant S267E/L328 internalize into LSEC more substantially than either anti-IgE IgG1 or anti-IgE with Fc knockout substitutions (G236R/L328R). Variants with intermediate Ilb affinity—S267E, G236D/S267E, and G236N/5267E—displayed intermediate internalization corresponding with their relative affinities.

[0367] A study was designed to evaluate the biodistribution and specific hepatic uptake of XmAb7195 (anti-IgE-S267E/L328F) as compared to saline controls and control antibody XENP6728 (anti-IgE-IgG1), when administered intravenously together with ⁸⁹Zr-IgE to female FcγRIIb transgenic mice.

[0368] Treatment began on Day 0. Animals were first injected intravenously with ⁸⁹Zr-labeled IgE in the range of 0.10 to 0.13 mCi. This was immediately followed by an intravenous injection of saline, 10 mg/kg XmAb7195, or 10 mg/kg XENP6728.

[0369] Animals were induced with 3.0% isoflurane in air (2.0 L/min) and were maintained during imaging procedures at 1.0-2.0% isoflurane in air (2.0 L/min). Animals were positioned inside the Siemens Inveon PET ring, and the PET acquisition was initiated and data was acquired continuously for 2 hours for the first acquisition.

[0370] Administration of XmAb7195 was associated with significantly greater, more rapid and more sustained accumulation of ⁸⁹Zr-IgE in the liver, compared with saline and compared with the IgG1 analog XENP6728. Correspondingly, administration of XmAb7195 was associated with significantly reduced accumulation of ⁸⁹Zr-IgE in the heart, which is representative of the amount of labeled IgE in bulk circulation. (FIG. 27).

[0371] Soluble CRs and CR-Fc fusions have been described for therapeutic purposes. These include CR1, CR2-Fc (U.S. Pat. No. 6,458,360), CR2-fH (CR2-factor H), and others. However, while these approaches generally block interaction of C3-tagged ICs with their associated receptors, they do not necessarily remove the immune complexes from circulation. Most of the complement receptors and regulatory proteins are composed of one or more so-called short complement repeat (SCR) domains, also called complement control protein (CCP) modules or Sushi domains. Typically, only a subset of the domains is involved in direct recognition of the associated complement fragment ligand. For example, it has been demonstrated that only the first two SCRs of CR2 are essential for C3d binding. The SCR domains are stable and well-behaved, making them suitable for use in the development of therapeutic proteins.

[0372] Genes encoding the first two (SCR1-2) or first four (SCR1-4) SCR domains from human and mouse were synthesized commercially (Blue Heron Biotechnologies). Genes were subcloned into the mammalian expression vector pTT5 (NRC-BRI, Canada) encoding the human IgG1 Fc (hinge-CH2-CH3 domains). The SCR domains were also subcloned into pTT5 vectors encoding variant IgG1 Fc domains containing S267E, G236D/L328F, G236N/L328F, S267E/L328F (high FcRIIb binding), or G236R/L328R (ablated FcR binding or Fc knockout; also shown as FcKO) substitutions. All DNA was sequenced to confirm the fidelity of the sequences. Amino acid sequences of select CR2-Fc variants are provided in FIG. 40. Plasmids containing heavy and light chain genes were co-transfected into HEK293E cells using lipofectamine (Invitrogen) and grown in FreeStyle 293 media (Invitrogen). After 5 days of growth, the antibodies were purified from the culture supernatant by protein A affinity using MabSelect resin (GE Healthcare).

[0373] SPR measurements were performed using a Biacore 3000 instrument (Biacore, Piscataway, N.J.). A protein A (Pierce Biotechnology) CM5 biosensor chip (Biacore) was generated using a standard primary amine coupling protocol. All measurements were performed using HBS-EP buffer (10 mM HEPES pH 7.4, 0.15 M NaCl, 3 mM EDTA, 0.005% vol/vol surfactant P20, Biacore). CR2-Fc variants at 25 nM in HBS-EP buffer were immobilized on the protein A surface and then 100 nM purified human C3d (Alpha Diagnostic cat# C3D18-N-25) was injected. After each cycle, the surface was regenerated by injecting glycine buffer (10 mM, pH 1.5). Data were processed by zeroing time and response before the injection of C3d and by subtracting appropriate nonspecific signals (response of reference channel and injection of running buffer). Kinetic analyses were performed by global fitting of binding data with a 1:1 Langmuir binding model using BIAevaluation software (Biacore). Example binding curves are shown in FIG. 39A.

[0374] Binding of CR2-Fc constructs to recombinant C3d-Fc was evaluated using ELISA. XENP12561 or XENP12562 (hSCR1-2 or hSCR1-4 Fc fusion) were coated to plates followed by adding varying concentrations of XENP12704, which is an anti-IgE antibody containing human C3d fused to the C-terminus of Ckappa. Anti-C1q antibody and no plate coating were used as controls. Plates were incubated overnight at 4° C. and an anti-IgG-F(ab′)2-specific-HRP antibody was used for ELISA detection. Results are shown in FIG. 39B. XENP12561 and XENP12562 showed clear binding to recombinant C3d, with XENP12562 (containing hSCR1-4 domains) showing slightly stronger binding. A similar ELISA format was also used to evaluate the binding of CR2-Fc constructs to C3d-tagged immune complexes (IC) present in normal and rheumatoid arthritis (RA) patient sera. RA patients have autoimmune antibodies present and their sera are expected to contain a higher amount of C3d-tagged IC of these antibodies compared to normal subjects. XENP12561 or XENP12562 (hSCR1-2 or hSCR1-4 Fc fusion) were coated to plates followed by adding varying concentrations of normal or RA patient sera. Plates were incubated overnight at 4° C. and an anti-IgG-F(ab′)2-specific-HRP antibody was used for ELISA detection. Results are shown in FIG. 39C. XENP12561 and XENP12562 showed strong binding to c3d-tagged IC present in both normal and RA patient sera. These results show that there is approximately 100-fold higher amount of IC in RA patient sera compared to normal sera.

[0375] OxLDL is bound naturally by scavenger receptors such as LOX-1 (also known as OLR1) and CD36. Amino acid sequences for human and mouse versions of these receptors are listed in FIG. 43. LOX-1 and CD36 Fc fusions can be designed (XENP13516, XENP13517, XENP13518, sequences are listed in FIG. 44A-B). An Fc region is desirable to increase serum half-life, stability, and expression yields, while also serving as a scaffold for the inclusion of Fc variants for enhancing FcγRIIbb affinity. Also, monoclonal antibodies that bind oxLDL are known in the art (XENP13514 and XENP13515, sequences are listed in FIG. 44A-B).

[0376] Plasmids containing appropriate genes were transfected or co-transfected into HEK293E cells using lipofectamine (Invitrogen) and grown in FreeStyle 293 media (Invitrogen). After 5 days of growth, the proteins were purified from the culture supernatant by protein A affinity using MabSelect resin (GE Healthcare). The resulting proteins were examined by size-exclusion chromatography (see FIG. 45).

[0377] Based on these results, amino acid sequences were designed for Fc-containing oxLDL-binding proteins containing the S267E/L328F Fc variant that confers enhanced FcγRIIb affinity (FIG. 46). Alternative Fc variants with various levels of FcγRIIb affinity can also be used as mentioned above, e.g., G236N/S236E, G236D/S267E, and S267E. These variants allow for the rapid clearance of oxLDL from the blood.

[0378] The E06 antibody can be humanized to reduce its immunogenicity as a therapeutic in humans. Sequences of humanized variable regions derived from the E06 parental sequence can be found in FIG. 47.

[0379] Anti-C3d antibodies with an Fc enhanced for FcRIIb binding (containing Fc substitutions S267E, S267E/L328F, or G236N/S267E) or ablated effector function (FcKO or Fc knockout; containing substitutions G236N/S267E) were produced using the anti-C3d variable regions 3d8b and 3d29 (Thurman et al., 2013; US20130129728A1). Desired gene segments were synthesized by Blue Heron Biotechnologies (Bothell, Wash.) from synthetic oligonucleotides and PCR products by automated gene synthesis. Antibody constructs in the pTT5 vector were expressed in 293E cells and purified by standard protein A chromatography. Antibodies were characterized by SDS-PAGE and SEC. Sequences of these antibodies are shown in FIG. 3. The 3d8b antibody can be humanized to reduce its immunogenicity as a therapeutic in humans. Sequences of humanized variable regions derived from the 3d8b parental sequence can be found in FIGS. 51E and F.

[0380] This study utilizes 2BKIX transgenic mice. The 2BKIX mouse strain (XCR-Horto-2BKIX) is characterized as having human FcγRIIb sequences knocked into the murine FcγRIIb locus, resulting in the expression of a chimeric FcγRIIb molecule comprised of the extracellular portion of hFcγRIIb and the intracellular signaling domain of mFcγRIIb. Treatment of animals was in accordance with the Xencor SOP, which adheres to the regulations outlined in the USDA Animal Welfare Act (9 CFR, Parts 1, 2, and 3) and the conditions specified in The Guide for Care and Use of Laboratory Animals (ILAR publication, 1996, National Academy Press). The study protocol and all associated procedures were approved by the Institutional Animal Care and Use Committee (IACUC) of Xencor. Prior to the start of the study, animals were randomly assigned to six groups. On Day 0, mice were anesthetized using isoflurane and baseline hindlimb and forelimb caliper measurements were taken. Each mouse then received a single 100 μL IV retro-orbital sinus/plexus (OSP) injection of 50% K/BxN arthritic serum. Mice then received treatment with their respective test articles via intraperitoneal injections 30-60 minutes following administration of arthritic serum (Table 1). Daily hindlimb and forelimb caliper measurements were recorded and animals given an overall clinical arthritic score based on the extent of ankle/wrist inflammation. Results (FIG. 1 and FIG. 2) show that mice injected with anti-C3d-Ilb (XENP13905 and XENP13910) had improved clinical scores compared to mice injected with anti-C3d-FcKO. This indicates that anti-C3d-Ilb antibodies bind to c3d tagged immune complexes, which are then cleared through IIb-Fc binding to LSEC cells. A reduction in immune complexes results in decreased clinical scores in these mice.

	TABLE 1
	Arthritic Serum
	Test Article	50% K/BxN
	No. of		TA Dose	Arthritic	Rt. Of	Dose
Group	mice	XENP #	Variant	(mg/kg)	Serum Volume	Admin.	frequency
A	8	PBS	PBS	N/A -	100 μL PBS	IV-OSP	SID, Day 0
				Days 0, 2, 4, 6
B	8	PBS	PBS	N/A -	100 μL serum	IV-OSP	SID, Day 0
				Days 0, 2, 4, 6
C	8	13905	3d8b_H0L0_IgG1	10 mg/kg	100 μL serum	IV-OSP	SID, Day 0
			S267E/L328F (IIbE)	Days 0, 2, 4, 6
D	8	13906	3d8b_H0L0_IgG1	10 mg/kg	100 μL serum	IV-OSP	SID, Day 0
			G236R/L328R (FcKO)	Days 0, 2, 4, 6
E	8	13910	3d29_H0L0_IgG1	10 mg/kg	100 μL serum	IV-OSP	SID, Day 0
			S267E/L328F (IIbE)	Days 0, 2, 4, 6
F	8	13911	3d29_H0L0_IgG1	10 mg/kg	100 μL serum	IV-OSP	SID, Day 0
			G236R/L328R (FcKO)	Days 0, 2, 4, 6

• [0381] Benoist, C., USE OF GLUCOSE-6-PHOSPHATE ISOMERASE AND ANTIBODIES THERETO FOR THE DIAGNOSIS AND THERAPY OF ARTHRITIS, AND TEST OF ANTI-ARTHRITIC COMPOUNDS. U.S. Pat. No. 7,662,375, Feb. 16, 2010.
• [0382] Fearon, D. T., Soluble complement regulatory molecules. U.S. Pat. No. 6,458,360, Oct. 1, 2002.
• [0383] Holers, M., ANTIBODIES TO THE C3D FRAGMENT OF COMPLEMENT COMPONENT 3. U.S. patent application Ser. No. 13/589,079, filed Aug. 17, 2012.
• [0384] Monach et al., The K/BxN Arthritis Model. Current Protocols in Immunology. 2008; 15.22.1-15.22.12.
• [0385] Thurman et al., Detection of complement activation using monoclonal antibodies against C3d. J. Clin. Invest. 2013; 123(5): 2218-2230.

[0386] All cited references are herein expressly incorporated by reference in their entirety.

[0387] Whereas particular embodiments have been described above for purposes of illustration, it will be appreciated by those skilled in the art that numerous variations of the details may be made without departing from the invention as described in the appended claims.