Patent Publication Number: US-2020276307-A1

Title: Anti-ErbB3 Antibodies and Uses Thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/793,756, filed Oct. 25, 2017, now U.S. Pat. No. 10,632,194, which is a continuation of U.S. application Ser. No. 15/011,978, filed Feb. 1, 2016, now U.S. Pat. No. 9,827,310, which is a continuation of U.S. application Ser. No. 14/308,527, filed Jun. 18, 2014, now U.S. Pat. No. 9,284,380, which is a division of U.S. application Ser. No. 13/623,885, filed Sep. 21, 2012, now U.S. Pat. No. 8,791,244, which claims the benefit under 35 USC § 119(e) of U.S. Provisional Application No. 61/541,312, filed on Sep. 30, 2011; 61/557,460, filed on Nov. 9, 2011; and 61/614,565, filed on Mar. 23, 2012, the disclosures of which are herein incorporated by reference in their entireties. 
    
    
     REFERENCE TO A SEQUENCE LISTING 
     This application includes an electronic sequence listing in a file named “6550CON3-US_Sequence.txt”, created on Apr. 14, 2020 and containing 184,102 bytes, which is hereby incorporated by reference in its entirety for all purposes. 
     FIELD OF THE INVENTION 
     The present invention relates to antibodies, and antigen-binding fragments thereof, which are specific for human ErbB3. 
     BACKGROUND 
     ErbB3 (also known as HER3) is a member of the ErbB/HER family of receptor tyrosine kinases (RTKs). Other members of this family include EGFR (also known as ErbB1 or HER1), ErbB2 (also known as HER2 or Neu), and HER4. ErbB receptors regulate cell proliferation, survival and differentiation by activating intracellular signaling cascades that lead to alterations in gene expression. 
     ErbB receptors are activated by the formation of either homo- or heterodimers. For example, when ErbB3 is co-expressed with ErbB2, an active heterodimeric signaling complex is formed. ErbB3 dimer formation is promoted by its ligand binding. Neuregulin 1 (NRG1) is the primary ligand for ErbB3 that promotes homo- or heterodimerization of the receptor. 
     ErbB3 has been found to be overexpressed in various cancer types, including breast, gastrointestinal, and pancreatic cancers. Anti-ErbB3 antibodies have been shown to inhibit the growth of several human tumor cell lines in mouse xenografts models. Anti-ErbB3 antibodies are mentioned in, e.g., U.S. Pat. Nos. 5,480,968; 5,968,511; US 2004/0197332; U.S. Pat. Nos. 7,332,580; 7,705,130; and 7,846,440. Nonetheless, there is a need in the art for novel ErbB3 antagonists, such as anti-ErbB3 antibodies, for the treatment of cancer and other related disorders. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides antibodies that bind human ErbB3. The antibodies of the invention are useful, inter alia, for inhibiting ErbB3-mediated signaling and for treating diseases and disorders caused by or related to ErbB3 activity and/or signaling. 
     The antibodies of the present invention, according to certain embodiments, block the interaction between ErbB3 and an ErbB3 ligand (e.g., NRG1 and/or NRG2). The antibodies may also possess one or more additional biological properties such as, e.g., inducing cell surface ErbB3 internalization, inhibiting NRG1-stimulated tumor growth in vitro, and/or inhibiting tumor growth in vivo. 
     The antibodies of the invention can be full-length (for example, an IgG1 or IgG4 antibody) or may comprise only an antigen-binding portion (for example, a Fab, F(ab′) 2  or scFv fragment), and may be modified to affect functionality, e.g., to eliminate residual effector functions (Reddy et al., 2000, J. Immunol. 164:1925-1933). 
     The present invention provides an antibody or antigen-binding fragment of an antibody comprising a heavy chain variable region (HCVR) having an amino acid sequence selected from the group consisting of SEQ ID NO: 2, 18, 34, 50, 66, 82, 98, 114, 130, 146, 162, 178, 194, 210, 226, 242, 258, 274, 290, 306, 322, 338, 354, 370, 386, 402, 418, 434, 450, 466 and 482, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity. 
     The present invention also provides an antibody or antigen-binding fragment of an antibody comprising a light chain variable region (LCVR) having an amino acid sequence selected from the group consisting of SEQ ID NO: 10, 26, 42, 58, 74, 90, 106, 122, 138, 154, 170, 186, 202, 218, 234, 250, 266, 282, 298, 314, 330, 346, 362, 378, 394, 410, 426, 442, 458, 474 and 490, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity. 
     The present invention also provides an antibody or antigen-binding fragment thereof comprising a HCVR and LCVR (HCVR/LCVR) sequence pair selected from the group consisting of SEQ ID NO: 2/10, 18/26, 34/42, 50/58, 66/74, 82/90, 98/106, 114/122, 130/138, 146/154, 162/170, 178/186, 194/202, 210/218, 226/234, 242/250, 258/266, 274/282, 290/298, 306/314, 322/330, 338/346, 354/362, 370/378, 386/394, 402/410, 418/426, 434/442, 450/458, 466/474 and 482/490. 
     The present invention also provides an antibody or antigen-binding fragment of an antibody comprising a heavy chain CDR3 (HCDR3) domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 8, 24, 40, 56, 72, 88, 104, 120, 136, 152, 168, 184, 200, 216, 232, 248, 264, 280, 296, 312, 328, 344, 360, 376, 392, 408, 424, 440, 456, 472 and 488 or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; and a light chain CDR3 (LCDR3) domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, 240, 256, 272, 288, 304, 320, 336, 352, 368, 384, 400, 416, 432, 448, 464, 480 and 496, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity. 
     In certain embodiments, the antibody or antigen-binding portion of an antibody comprises a HCDR3/LCDR3 amino acid sequence pair selected from the group consisting of SEQ ID NO: 8/16, 24/32, 40/48, 56/64, 72/80, 88/96, 104/112, 120/128, 136/144, 152/160, 168/176, 184/192, 200/208, 216/224, 232/240, 248/256, 264/272, 280/288, 296/304, 312/320, 328/336, 344/352, 360/368, 376/384, 392/400, 408/416, 424/432, 440/448, 456/464, 472/480 and 488/496. 
     The present invention also provides an antibody or fragment thereof further comprising a heavy chain CDR1 (HCDR1) domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 4, 20, 36, 52, 68, 84, 100, 116, 132, 148, 164, 180, 196, 212, 228, 244, 260, 276, 292, 308, 324, 340, 356, 372, 388, 404, 420, 436, 452, 468 and 484, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; a heavy chain CDR2 (HCDR2) domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 6, 22, 38, 54, 70, 86, 102, 118, 134, 150, 166, 182, 198, 214, 230, 246, 262, 278, 294, 310, 326, 342, 358, 374, 390, 406, 422, 438, 454, 470 and 486, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; a light chain CDR1 (LCDR1) domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 12, 28, 44, 60, 76, 92, 108, 124, 140, 156, 172, 188, 204, 220, 236, 252, 268, 284, 300, 316, 332, 348, 364, 380, 396, 412, 428, 444, 460, 476 and 492, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; and a light chain CDR2 (LCDR2) domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 14, 30, 46, 62, 78, 94, 110, 126, 142, 158, 174, 190, 206, 222, 238, 254, 270, 286, 302, 318, 334, 350, 366, 382, 398, 414, 430, 446, 462, 478 and 494, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity. 
     Certain non-limiting, exemplary antibodies and antigen-binding fragments of the invention comprise HCDR1-HCDR2-HCDR3-LCDR1-LCDR2-LCDR3 domains, respectively, having the amino acid sequences selected from the group consisting of: SEQ ID NOs: 4-6-8-12-14-16 (e.g. H4H2084P); 20-22-24-28-30-32 (e.g. H4H2092P); 36-38-40-44-46-48 (e.g. H4H2094P); 52-54-56-60-62-64 (e.g. H4H2098P); 68-70-72-76-78-80 (e.g. H4H2102P); 84-86-88-92-94-96 (e.g. H4H2108P); 100-102-104-108-110-112 (e.g. H4H2111P); 116-118-120-124-126-128 (e.g. H4H2114P); 132-134-136-140-142-144 (e.g. H4H2132P); 148-150-152-156-158-160 (e.g., H4H2138P); 164-166-168-172-174-176 (e.g. H4H2140P); 180-182-184-188-190-192 (e.g., H4H2143P); 196-198-200-204-206-208 (e.g. H4H2146P); 212-214-216-220-222-224 (e.g. H4H2147P); 228-230-232-236-238-240 (e.g. H4H2148P); 244-246-248-252-254-256 (e.g. H4H2151P); 260-262-264-268-270-272 (e.g. H4H2153P); 276-278-280-284-286-288 (e.g. H4H2154P); 292-294-296-300-302-304 (e.g. H4H2290P); 308-310-312-316-318-320 (e.g. H1M1819N); 324-326-328-332-334-336 (e.g. H2M1821N); 340-342-344-348-350-352 (e.g. H2M1824N); 356-358-360-364-366-368 (e.g. H2M1827N); 372-374-376-380-382-384 (e.g. H1M1828N); 388-390-392-396-398-400 (e.g. H2M1829N); 404-406-408-412-414-416 (e.g. H2M1930N); 420-422-424-428-430-432 (e.g. H2M1943N); 436-438-440-444-446-448 (e.g. H2M1936N); 452-454-456-460-462-464 (e.g. H2M1937N); 468-470-472-476-478-480 (e.g. H2M1938N); and 484-486-488-492-494-496 (e.g. H1M1940N). 
     In a related embodiment, the invention includes an antibody or antigen-binding fragment of an antibody which specifically binds ErbB3, wherein the antibody or fragment comprises the heavy and light chain CDR domains contained within heavy and light chain sequences selected from the group consisting of SEQ ID NO: 2/10, 18/26, 34/42, 50/58, 66/74, 82/90, 98/106, 114/122, 130/138, 146/154, 162/170, 178/186, 194/202, 210/218, 226/234, 242/250, 258/266, 274/282, 290/298, 306/314, 322/330, 338/346, 354/362, 370/378, 386/394, 402/410, 418/426, 434/442, 450/458, 466/474 and 482/490. Methods and techniques for identifying CDRs within HCVR and LCVR amino acid sequences are well known in the art and can be used to identify CDRs within the specified HCVR and/or LCVR amino acid sequences disclosed herein. Exemplary conventions that can be used to identify the boundaries of CDRs include, e.g., the Kabat definition, the Chothia definition, and the AbM definition. In general terms, the Kabat definition is based on sequence variability, the Chothia definition is based on the location of the structural loop regions, and the AbM definition is a compromise between the Kabat and Chothia approaches. See, e.g., Kabat, “Sequences of Proteins of Immunological Interest,” National Institutes of Health, Bethesda, Md. (1991); Al-Lazikani et al.,  J. Mol. Biol.  273:927-948 (1997); and Martin et al.,  Proc. Natl. Acad. Sci. USA  86:9268-9272 (1989). Public databases are also available for identifying CDR sequences within an antibody. 
     In another aspect, the invention provides nucleic acid molecules encoding anti-ErbB3 antibodies or fragments thereof. Recombinant expression vectors carrying the nucleic acids of the invention, and host cells into which such vectors have been introduced, are also encompassed by the invention, as are methods of producing the antibodies by culturing the host cells under conditions permitting production of the antibodies, and recovering the antibodies produced. 
     In one embodiment, the invention provides an antibody or fragment thereof comprising a HCVR encoded by a nucleic acid sequence selected from the group consisting of SEQ ID NO: 1, 17, 33, 49, 65, 81, 97, 113, 129, 145, 161, 177, 193, 209, 225, 241, 257, 273, 289, 305, 321, 337, 353, 369, 385, 401, 417, 433, 449, 465 and 481, or a substantially identical sequence having at least 90%, at least 95%, at least 98%, or at least 99% homology thereof. 
     The present invention also provides an antibody or fragment thereof comprising a LCVR encoded by a nucleic acid sequence selected from the group consisting of SEQ ID NO: 9, 25, 41, 57, 73, 89, 105, 121, 137, 153, 169, 185, 201, 217, 233, 249, 265, 281, 297, 313, 329, 345, 361, 377, 393, 409, 425, 441, 457, 473 and 489, or a substantially identical sequence having at least 90%, at least 95%, at least 98%, or at least 99% homology thereof. 
     The present invention also provides an antibody or antigen-binding fragment of an antibody comprising a HCDR3 domain encoded by a nucleotide sequence selected from the group consisting of SEQ ID NO: 7, 23, 39, 55, 71, 87, 103, 119, 135, 151, 167, 183, 199, 215, 231, 247, 263, 279, 295, 311, 327, 343, 359, 375, 391, 407, 423, 439, 455, 471 and 478, or a substantially identical sequence having at least 90%, at least 95%, at least 98%, or at least 99% homology thereof; and a LCDR3 domain encoded by a nucleotide sequence selected from the group consisting of SEQ ID NO: 15, 31, 47, 63, 79, 95, 111, 127, 143, 159, 175, 191, 207, 223, 239, 255, 271, 287, 303, 319, 335, 351, 367, 383, 399, 415, 431, 447, 463, 479 and 495, or a substantially identical sequence having at least 90%, at least 95%, at least 98%, or at least 99% homology thereof. 
     The present invention also provides an antibody or fragment thereof which further comprises a HCDR1 domain encoded by a nucleotide sequence selected from the group consisting of SEQ ID NO: 3, 19, 35, 51, 67, 83, 99, 115, 131, 147, 163, 179, 195, 211, 227, 243, 259, 275, 291, 307, 323, 339, 355, 371, 387, 403, 419, 435, 451, 467 and 483 or a substantially identical sequence having at least 90%, at least 95%, at least 98%, or at least 99% homology thereof; a HCDR2 domain encoded by a nucleotide sequence selected from the group consisting of SEQ ID NO: 5, 21, 37, 53, 69, 85, 101, 117, 133, 149, 165, 181, 197, 213, 229, 245, 261, 277, 293, 309, 325, 341, 357, 373, 389, 405, 421, 437, 453, 469 and 485, or a substantially identical sequence having at least 90%, at least 95%, at least 98%, or at least 99% homology thereof; a LCDR1 domain encoded by a nucleotide sequence selected from the group consisting of SEQ ID NO: 11, 27, 43, 59, 75, 91, 107, 123, 139, 155, 171, 187, 203, 219, 235, 251, 267, 283, 299, 315, 331, 347, 363, 379, 395, 411, 427, 443, 459, 475 and 491, or a substantially identical sequence having at least 90%, at least 95%, at least 98%, or at least 99% homology thereof; and a LCDR2 domain encoded by a nucleotide sequence selected from the group consisting of SEQ ID NO: 13, 29, 45, 61, 77, 93, 109, 125, 141, 157, 173, 189, 205, 221, 237, 253, 269, 285, 301, 317, 333, 349, 365, 381, 397, 413, 429, 445, 461, 477 and 493, or a substantially identical sequence having at least 90%, at least 95%, at least 98%, or at least 99% homology thereof. 
     According to certain embodiments, the antibody or fragment thereof comprises the heavy and light chain CDR sequences encoded by the nucleic acid sequences of SEQ ID NOs: SEQ ID NOs: 1 and 9 (e.g. H4H2084P), 17 and 25 (e.g. H4H2092P), 33 and 41 (e.g. H4H2094P), 49 and 57 (e.g. H4H2098P), 65 and 73 (e.g. H4H2102P), 81 and 89 (e.g. H4H2108P), 97 and 105 (e.g. H4H2111P), 113 and 121 (e.g. H4H2114P), 129 and 137 (e.g. H4H2132P), 145 and 153 (e.g. H4H2138P), 161 and 169 (e.g. H4H2140P), 177 and 185 (e.g. H4H2143P), 193 and 201 (e.g. H4H2146P), 209 and 217 (e.g. H4H2147P), 225 and 233 (e.g. H4H2148P), 241 and 249 (e.g. H4H2151P), 257 and 265 (e.g. H4H2153P), 273 and 281 (e.g. H4H2154P), 289 and 297 (e.g. H4H2290P), 305 and 313 (e.g. H1M1819N), 321 and 329 (e.g. H2M1821N), 337 and 345 (e.g. H2M1824N), 353 and 361 (e.g. H2M1827N), 369 and 377 (e.g. H1M1828N), 385 and 393 (e.g. H2M1829N), 401 and 409 (e.g. H2M1930N), 417 and 425 (e.g. H2M1934N), 433 and 441 (e.g. H2M1936N), 449 and 457 (e.g. H2M1937N), 465 and 473 (e.g. H2M1938N), or 481 and 489 (e.g. H1M1940N). 
     The present invention includes anti-ErbB3 antibodies having a modified glycosylation pattern. In some applications, modification to remove undesirable glycosylation sites may be useful, or an antibody lacking a fucose moiety present on the oligosaccharide chain, for example, to increase antibody dependent cellular cytotoxicity (ADCC) function (see Shield et al. (2002) JBC 277:26733). In other applications, modification of galactosylation can be made in order to modify complement dependent cytotoxicity (CDC). 
     In another aspect, the invention provides a pharmaceutical composition comprising a recombinant human antibody or fragment thereof which specifically binds ErbB3 and a pharmaceutically acceptable carrier. In a related aspect, the invention features a composition which is a combination of an ErbB3 inhibitor and a second therapeutic agent. In one embodiment, the ErbB3 inhibitor is an antibody or fragment thereof. In one embodiment, the second therapeutic agent is any agent that is advantageously combined with an ErbB3 inhibitor. Exemplary agents that may be advantageously combined with an ErbB3 inhibitor include, without limitation, other agents that inhibit ErbB3 activity (including other antibodies or antigen-binding fragments thereof, peptide inhibitors, small molecule antagonists, etc) and/or agents which interfere with ErbB3 upstream or downstream signaling. 
     In yet another aspect, the invention provides methods for inhibiting ErbB3 activity using an anti-ErbB3 antibody or antigen-binding portion of an antibody of the invention, wherein the therapeutic methods comprise administering a therapeutically effective amount of a pharmaceutical composition comprising an antibody or antigen-binding fragment of an antibody of the invention. The disorder treated is any disease or condition which is improved, ameliorated, inhibited or prevented by removal, inhibition or reduction of ErbB3 activity. The anti-ErbB3 antibody or antibody fragment of the invention may function to block the interaction between ErbB3 and an ErbB3 binding partner (e.g., neuregulin-1), or otherwise inhibit the signaling activity of ErbB3. 
     The present invention also includes the use of an anti-ErbB3 antibody or antigen binding portion of an antibody of the invention in the manufacture of a medicament for the treatment of a disease or disorder related to or caused by ErbB3 activity in a patient. 
     Other embodiments will become apparent from a review of the ensuing detailed description. 
    
    
     DETAILED DESCRIPTION 
     Before the present invention is described, it is to be understood that this invention is not limited to particular methods and experimental conditions described, as such methods and conditions may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. As used herein, the term “about,” when used in reference to a particular recited numerical value, means that the value may vary from the recited value by no more than 1%. For example, as used herein, the expression “about 100” includes 99 and 101 and all values in between (e.g., 99.1, 99.2, 99.3, 99.4, etc.). 
     Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are now described. All patents, applications and non-patent publications mentioned in this specification are incorporated herein by reference in their entireties. 
     Definitions 
     The expressions “ErbB3” and “ErbB3 fragment,” as used herein refer to the human ErbB3 protein or fragment unless specified as being from a non-human species (e.g., “mouse ErbB3,” “mouse ErbB3 fragment,” “monkey ErbB3,” “monkey ErbB3 fragment,” etc.). The extracellular domain of human ErbB3 has the amino acid sequence shown in, e.g., amino acids 1-613 of SEQ ID NOs:497-499. 
     The term “ErbB3 ligand,” as used herein, means a protein capable of binding to the extracellular domain of human ErbB3 protein to transmit a biological signal in vivo. The term “ErbB3 ligand” includes neuregulin-1 (NRG1) and neuregulin-2 (NRG2). 
     The term “antibody”, as used herein, is intended to refer to immunoglobulin molecules comprising four polypeptide chains, two heavy (H) chains and two light (L) chains inter-connected by disulfide bonds, as well as multimers thereof (e.g., IgM). Each heavy chain comprises a heavy chain variable region (abbreviated herein as HCVR or V H ) and a heavy chain constant region. The heavy chain constant region comprises three domains, C H 1, C H 2 and C H 3. Each light chain comprises a light chain variable region (abbreviated herein as LCVR or V L ) and a light chain constant region. The light chain constant region comprises one domain (C L 1). The V H  and V L  regions can be further subdivided into regions of hypervariability, termed complementarity determining regions (CDRs), interspersed with regions that are more conserved, termed framework regions (FR). Each V H  and V L  is composed of three CDRs and four FRs, arranged from amino-terminus to carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. In different embodiments of the invention, the FRs of the anti-ErbB3 antibody (or antigen-binding portion thereof) may be identical to the human germline sequences, or may be naturally or artificially modified. An amino acid consensus sequence may be defined based on a side-by-side analysis of two or more CDRs. 
     The term “antibody,” as used herein, also includes antigen-binding fragments of full antibody molecules. The terms “antigen-binding portion” of an antibody, “antigen-binding fragment” of an antibody, and the like, as used herein, include any naturally occurring, enzymatically obtainable, synthetic, or genetically engineered polypeptide or glycoprotein that specifically binds an antigen to form a complex. Antigen-binding fragments of an antibody may be derived, e.g., from full antibody molecules using any suitable standard techniques such as proteolytic digestion or recombinant genetic engineering techniques involving the manipulation and expression of DNA encoding antibody variable and optionally constant domains. Such DNA is known and/or is readily available from, e.g., commercial sources, DNA libraries (including, e.g., phage-antibody libraries), or can be synthesized. The DNA may be sequenced and manipulated chemically or by using molecular biology techniques, for example, to arrange one or more variable and/or constant domains into a suitable configuration, or to introduce codons, create cysteine residues, modify, add or delete amino acids, etc. 
     Non-limiting examples of antigen-binding fragments include: (i) Fab fragments; (ii) F(ab′)2 fragments; (iii) Fd fragments; (iv) Fv fragments; (v) single-chain Fv (scFv) molecules; (vi) dAb fragments; and (vii) minimal recognition units consisting of the amino acid residues that mimic the hypervariable region of an antibody (e.g., an isolated complementarity determining region (CDR) such as a CDR3 peptide), or a constrained FR3-CDR3-FR4 peptide. Other engineered molecules, such as domain-specific antibodies, single domain antibodies, domain-deleted antibodies, chimeric antibodies, CDR-grafted antibodies, diabodies, triabodies, tetrabodies, minibodies, nanobodies (e.g. monovalent nanobodies, bivalent nanobodies, etc.), small modular immunopharmaceuticals (SMIPs), and shark variable IgNAR domains, are also encompassed within the expression “antigen-binding fragment,” as used herein. 
     An antigen-binding fragment of an antibody will typically comprise at least one variable domain. The variable domain may be of any size or amino acid composition and will generally comprise at least one CDR which is adjacent to or in frame with one or more framework sequences. In antigen-binding fragments having a V H  domain associated with a V L  domain, the V H  and V L  domains may be situated relative to one another in any suitable arrangement. For example, the variable region may be dimeric and contain V H —V H , V H —V L  or V L —V L  dimers. Alternatively, the antigen-binding fragment of an antibody may contain a monomeric V H  or V L  domain. 
     In certain embodiments, an antigen-binding fragment of an antibody may contain at least one variable domain covalently linked to at least one constant domain. Non-limiting, exemplary configurations of variable and constant domains that may be found within an antigen-binding fragment of an antibody of the present invention include: (i) V H -C H 1; (ii) V H -C H 2; (iii) V H -C H 3; (iv) V H -C H 1-C H 2; (v) V H -C H 1-C H 2-C H 3; (vi) V H -C H 2-C H 3; (vii) V H -C L ; (viii) V L -C H 1; (ix) V L -C H 2; (x) V L -C H 3; (xi) V L -C H -C H 2; (xii) V L -C H 1-C H 2-C H 3; (xiii) V L -C H 2-C H 3; and (xiv) V L -C L . In any configuration of variable and constant domains, including any of the exemplary configurations listed above, the variable and constant domains may be either directly linked to one another or may be linked by a full or partial hinge or linker region. A hinge region may consist of at least 2 (e.g., 5, 10, 15, 20, 40, 60 or more) amino acids which result in a flexible or semi-flexible linkage between adjacent variable and/or constant domains in a single polypeptide molecule. Moreover, an antigen-binding fragment of an antibody of the present invention may comprise a homo-dimer or hetero-dimer (or other multimer) of any of the variable and constant domain configurations listed above in non-covalent association with one another and/or with one or more monomeric V H  or V L  domain (e.g., by disulfide bond(s)). 
     As with full antibody molecules, antigen-binding fragments may be monospecific or multispecific (e.g., bispecific). A multispecific antigen-binding fragment of an antibody will typically comprise at least two different variable domains, wherein each variable domain is capable of specifically binding to a separate antigen or to a different epitope on the same antigen. Any multispecific antibody format, including the exemplary bispecific antibody formats disclosed herein, may be adapted for use in the context of an antigen-binding fragment of an antibody of the present invention using routine techniques available in the art. 
     The antibodies of the present invention may function through complement-dependent cytotoxicity (CDC) or antibody-dependent cell-mediated cytotoxicity (ADCC). “Complement-dependent cytotoxicity” (CDC) refers to lysis of antigen-expressing cells by an antibody of the invention in the presence of complement. “Antibody-dependent cell-mediated cytotoxicity” (ADCC) refers to a cell-mediated reaction in which nonspecific cytotoxic cells that express Fc receptors (FcRs) (e.g., Natural Killer (NK) cells, neutrophils, and macrophages) recognize bound antibody on a target cell and thereby lead to lysis of the target cell. CDC and ADCC can be measured using assays that are well known and available in the art. (See, e.g., U.S. Pat. Nos. 5,500,362 and 5,821,337, and Clynes et al. (1998) Proc. Natl. Acad. Sci. (USA) 95:652-656). The constant region of an antibody is important in the ability of an antibody to fix complement and mediate cell-dependent cytotoxicity. Thus, the isotype of an antibody may be selected on the basis of whether it is desirable for the antibody to mediate cytotoxicity. 
     The term “human antibody”, as used herein, is intended to include antibodies having variable and constant regions derived from human germline immunoglobulin sequences. The human antibodies of the invention may include amino acid residues not encoded by human germline immunoglobulin sequences (e.g., mutations introduced by random or site-specific mutagenesis in vitro or by somatic mutation in vivo), for example in the CDRs and in particular CDR3. However, the term “human antibody”, as used herein, is not intended to include antibodies in which CDR sequences derived from the germline of another mammalian species, such as a mouse, have been grafted onto human framework sequences. 
     The term “recombinant human antibody”, as used herein, is intended to include all human antibodies that are prepared, expressed, created or isolated by recombinant means, such as antibodies expressed using a recombinant expression vector transfected into a host cell (described further below), antibodies isolated from a recombinant, combinatorial human antibody library (described further below), antibodies isolated from an animal (e.g., a mouse) that is transgenic for human immunoglobulin genes (see e.g., Taylor et al. (1992) Nucl. Acids Res. 20:6287-6295) or antibodies prepared, expressed, created or isolated by any other means that involves splicing of human immunoglobulin gene sequences to other DNA sequences. Such recombinant human antibodies have variable and constant regions derived from human germline immunoglobulin sequences. In certain embodiments, however, such recombinant human antibodies are subjected to in vitro mutagenesis (or, when an animal transgenic for human Ig sequences is used, in vivo somatic mutagenesis) and thus the amino acid sequences of the V H  and V L  regions of the recombinant antibodies are sequences that, while derived from and related to human germline V H  and V L  sequences, may not naturally exist within the human antibody germline repertoire in vivo. 
     Human antibodies can exist in two forms that are associated with hinge heterogeneity. In one form, an immunoglobulin molecule comprises a stable four chain construct of approximately 150-160 kDa in which the dimers are held together by an interchain heavy chain disulfide bond. In a second form, the dimers are not linked via inter-chain disulfide bonds and a molecule of about 75-80 kDa is formed composed of a covalently coupled light and heavy chain (half-antibody). These forms have been extremely difficult to separate, even after affinity purification. 
     The frequency of appearance of the second form in various intact IgG isotypes is due to, but not limited to, structural differences associated with the hinge region isotype of the antibody. A single amino acid substitution in the hinge region of the human IgG4 hinge can significantly reduce the appearance of the second form (Angal et al. (1993) Molecular Immunology 30:105) to levels typically observed using a human IgG1 hinge. The instant invention encompasses antibodies having one or more mutations in the hinge, C H 2 or C H 3 region which may be desirable, for example, in production, to improve the yield of the desired antibody form. 
     An “isolated antibody,” as used herein, means an antibody that has been identified and separated and/or recovered from at least one component of its natural environment. For example, an antibody that has been separated or removed from at least one component of an organism, or from a tissue or cell in which the antibody naturally exists or is naturally produced, is an “isolated antibody” for purposes of the present invention. An isolated antibody also includes an antibody in situ within a recombinant cell. Isolated antibodies are antibodies that have been subjected to at least one purification or isolation step. According to certain embodiments, an isolated antibody may be substantially free of other cellular material and/or chemicals. 
     The term “specifically binds,” or the like, means that an antibody or antigen-binding fragment thereof forms a complex with an antigen that is relatively stable under physiologic conditions. Methods for determining whether an antibody specifically binds to an antigen are well known in the art and include, for example, equilibrium dialysis, surface plasmon resonance, and the like. For example, an antibody that “specifically binds” human ErbB3, as used in the context of the present invention, includes antibodies that bind human ErbB3 or portion thereof with a K D  of less than about 1000 nM, less than about 500 nM, less than about 300 nM, less than about 200 nM, less than about 100 nM, less than about 90 nM, less than about 80 nM, less than about 70 nM, less than about 60 nM, less than about 50 nM, less than about 40 nM, less than about 30 nM, less than about 20 nM, less than about 10 nM, less than about 5 nM, less than about 4 nM, less than about 3 nM, less than about 2 nM, less than about 1 nM or less than about 0.5 nM, as measured in a surface plasmon resonance assay. (See, e.g., Example 3, herein). An isolated antibody that specifically binds human ErbB3 may, however, have cross-reactivity to other antigens, such as ErbB3 molecules from other (non-human) species. 
     A “neutralizing” or “blocking” antibody, as used herein, is intended to refer to an antibody whose binding to ErbB3: (i) interferes with the interaction between ErbB3 or an ErbB3 fragment and an ErbB3 ligand (e.g., neuregulin 1), and/or (ii) results in inhibition of at least one biological function of ErbB3. The inhibition caused by an ErbB3 neutralizing or blocking antibody need not be complete so long as it is detectable using an appropriate assay. Exemplary assays for detecting ErbB3 inhibition are described herein. 
     The anti-ErbB3 antibodies disclosed herein may comprise one or more amino acid substitutions, insertions and/or deletions in the framework and/or CDR regions of the heavy and light chain variable domains as compared to the corresponding germline sequences from which the antibodies were derived. Such mutations can be readily ascertained by comparing the amino acid sequences disclosed herein to germline sequences available from, for example, public antibody sequence databases. The present invention includes antibodies, and antigen-binding fragments thereof, which are derived from any of the amino acid sequences disclosed herein, wherein one or more amino acids within one or more framework and/or CDR regions are mutated to the corresponding residue(s) of the germline sequence from which the antibody was derived, or to the corresponding residue(s) of another human germline sequence, or to a conservative amino acid substitution of the corresponding germline residue(s) (such sequence changes are referred to herein collectively as “germline mutations”). A person of ordinary skill in the art, starting with the heavy and light chain variable region sequences disclosed herein, can easily produce numerous antibodies and antigen-binding fragments which comprise one or more individual germline mutations or combinations thereof. In certain embodiments, all of the framework and/or CDR residues within the V H  and/or V L  domains are mutated back to the residues found in the original germline sequence from which the antibody was derived. In other embodiments, only certain residues are mutated back to the original germline sequence, e.g., only the mutated residues found within the first 8 amino acids of FR1 or within the last 8 amino acids of FR4, or only the mutated residues found within CDR1, CDR2 or CDR3. In other embodiments, one or more of the framework and/or CDR residue(s) are mutated to the corresponding residue(s) of a different germline sequence (i.e., a germline sequence that is different from the germline sequence from which the antibody was originally derived). Furthermore, the antibodies of the present invention may contain any combination of two or more germline mutations within the framework and/or CDR regions, e.g., wherein certain individual residues are mutated to the corresponding residue of a particular germline sequence while certain other residues that differ from the original germline sequence are maintained or are mutated to the corresponding residue of a different germline sequence. Once obtained, antibodies and antigen-binding fragments that contain one or more germline mutations can be easily tested for one or more desired property such as, improved binding specificity, increased binding affinity, improved or enhanced antagonistic or agonistic biological properties (as the case may be), reduced immunogenicity, etc. Antibodies and antigen-binding fragments obtained in this general manner are encompassed within the present invention. 
     The present invention also includes anti-ErbB3 antibodies comprising variants of any of the HCVR, LCVR, and/or CDR amino acid sequences disclosed herein having one or more conservative substitutions. For example, the present invention includes anti-ErbB3 antibodies having HCVR, LCVR, and/or CDR amino acid sequences with, e.g., 10 or fewer, 8 or fewer, 6 or fewer, 4 or fewer, etc. conservative amino acid substitutions relative to any of the HCVR, LCVR, and/or CDR amino acid sequences disclosed herein. 
     The term “surface plasmon resonance”, as used herein, refers to an optical phenomenon that allows for the analysis of real-time interactions by detection of alterations in protein concentrations within a biosensor matrix, for example using the BIAcore™ system (Biacore Life Sciences division of GE Healthcare, Piscataway, N.J.). 
     The term “K D ”, as used herein, is intended to refer to the equilibrium dissociation constant of a particular antibody-antigen interaction. 
     The term “epitope” refers to an antigenic determinant that interacts with a specific antigen binding site in the variable region of an antibody molecule known as a paratope. A single antigen may have more than one epitope. Thus, different antibodies may bind to different areas on an antigen and may have different biological effects. 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. In certain circumstance, an epitope may include moieties of saccharides, phosphoryl groups, or sulfonyl groups on the antigen. 
     The term “substantial identity” or “substantially identical,” when referring to a nucleic acid or fragment thereof, indicates that, when optimally aligned with appropriate nucleotide insertions or deletions with another nucleic acid (or its complementary strand), there is nucleotide sequence identity in at least about 95%, and more preferably at least about 96%, 97%, 98% or 99% of the nucleotide bases, as measured by any well-known algorithm of sequence identity, such as FASTA, BLAST or Gap, as discussed below. A nucleic acid molecule having substantial identity to a reference nucleic acid molecule may, in certain instances, encode a polypeptide having the same or substantially similar amino acid sequence as the polypeptide encoded by the reference nucleic acid molecule. 
     As applied to polypeptides, the term “substantial similarity” or “substantially similar” means that two peptide sequences, when optimally aligned, such as by the programs GAP or BESTFIT using default gap weights, share at least 95% sequence identity, even more preferably at least 98% or 99% sequence identity. Preferably, residue positions which are not identical differ by conservative amino acid substitutions. A “conservative amino acid substitution” is one in which an amino acid residue is substituted by another amino acid residue having a side chain (R group) with similar chemical properties (e.g., charge or hydrophobicity). In general, a conservative amino acid substitution will not substantially change the functional properties of a protein. In cases where two or more amino acid sequences differ from each other by conservative substitutions, the percent sequence identity or degree of similarity may be adjusted upwards to correct for the conservative nature of the substitution. Means for making this adjustment are well-known to those of skill in the art. See, e.g., Pearson (1994) Methods Mol. Biol. 24: 307-331, herein incorporated by reference. Examples of groups of amino acids that have side chains with similar chemical properties include (1) aliphatic side chains: glycine, alanine, valine, leucine and isoleucine; (2) aliphatic-hydroxyl side chains: serine and threonine; (3) amide-containing side chains: asparagine and glutamine; (4) aromatic side chains: phenylalanine, tyrosine, and tryptophan; (5) basic side chains: lysine, arginine, and histidine; (6) acidic side chains: aspartate and glutamate, and (7) sulfur-containing side chains are cysteine and methionine. Preferred conservative amino acids substitution groups are: valine-leucine-isoleucine, phenylalanine-tyrosine, lysine-arginine, alanine-valine, glutamate-aspartate, and asparagine-glutamine. Alternatively, a conservative replacement is any change having a positive value in the PAM250 log-likelihood matrix disclosed in Gonnet et al. (1992) Science 256: 1443-1445, herein incorporated by reference. A “moderately conservative” replacement is any change having a nonnegative value in the PAM250 log-likelihood matrix. 
     Sequence similarity for polypeptides, which is also referred to as sequence identity, is typically measured using sequence analysis software. Protein analysis software matches similar sequences using measures of similarity assigned to various substitutions, deletions and other modifications, including conservative amino acid substitutions. For instance, GCG software contains programs such as Gap and Bestfit which can be used with default parameters to determine sequence homology or sequence identity between closely related polypeptides, such as homologous polypeptides from different species of organisms or between a wild type protein and a mutein thereof. See, e.g., GCG Version 6.1. Polypeptide sequences also can be compared using FASTA using default or recommended parameters, a program in GCG Version 6.1. FASTA (e.g., FASTA2 and FASTA3) provides alignments and percent sequence identity of the regions of the best overlap between the query and search sequences (Pearson (2000) supra). Another preferred algorithm when comparing a sequence of the invention to a database containing a large number of sequences from different organisms is the computer program BLAST, especially BLASTP or TBLASTN, using default parameters. See, e.g., Altschul et al. (1990) J. Mol. Biol. 215:403-410 and Altschul et al. (1997) Nucleic Acids Res. 25:3389-402, each herein incorporated by reference. 
     Biological Characteristics of the Antibodies 
     The antibodies of the present invention block the interaction between ErbB3 and its ligand neuregulin-1 (NRG1). As used herein, the expression “blocks the interaction between ErbB3 and NRG1” means that, in an assay in which the physical interaction between ErbB3 and NRG1 can be detected and/or quantified, the addition of an antibody of the invention reduces the interaction between ErbB3 and NRG1 by at least 50%. A non-limiting, exemplary assay that can be used to determine if an antibody blocks the interaction between human ErbB3 and NRG1 is illustrated in Example 4, herein. In this Example, antibodies are mixed with ErbB3 protein, and then the antibody/ErbB3 mixture is applied to a surface coated with NRG1 protein. After washing away unbound molecules, the amount of ErbB3 bound to the NRG1-coated surface is measured. By using varying amounts of antibody in this assay format, the amount of antibody required to block 50% of ErbB3 binding to NRG1 can be calculated and expressed as an IC 50  value. The present invention includes anti-ErbB3 antibodies that exhibit an IC 50  of less than about 600 pM when tested in an ErbB3/NRG1 binding assay as described above, or a substantially similar assay. For example, the invention includes anti-ErbB3 antibodies that exhibit an IC 50  of less than about 600, 500, 400, 300, 290, 280, 270, 260, 250, 240, 230, 220, 210, 200, 190, 180, 170, 160, 150, 140, 130, 120, 110, 100, 90, 80, 70, 60, 50, 40, 30, 20, 10, 18, 16, 14, 12, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 pM when tested in an ErbB3/NRG1 binding assay as described above, or a substantially similar assay. 
     Alternatively, one can determine whether an antibody blocks the interaction between ErbB3 and NRG1 by using a cell-based assay format that detects changes in NRG1-induced cellular signaling. Exemplary assay formats of this type are illustrated in Examples 6 and 8, herein. In these Examples, the extent of phosphorylation of the kinase Akt and/or ErbB3 in cells following treatment with NRG1 in the presence of varying amounts of anti-ErbB3 antibody is measured. In these assay formats, the percent inhibition of Akt and/or ErbB3 phosphorylation caused by the presence of an anti-ErbB3 antibody serves as an indicator of the extent to which the antibody blocks the interaction between ErbB3 and NRG1. The present invention includes antibodies that inhibit Akt or ErbB3 phosphorylation by at least 60% when tested in an Akt or ErbB3 phosphorylation assay as described above, or a substantially similar assay. For example, the invention includes anti-ErbB3 antibodies that inhibit Akt or ErbB3 phosphorylation by at least about 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100% when tested in an Akt or ErbB3 phosphorylation assay as described above, or a substantially similar assay. 
     The anti-ErbB3 antibodies of the present invention also exhibit one or more of the following properties: (1) the ability to induce internalization of cell surface expressed ErbB3 (see, e.g., Example 5, herein); (2) the ability to inhibit NRG1-stimulated tumor cell growth in vitro, either alone or in combination with EGFR inhibition (see, e.g., Example 7, herein); and (3) the ability to inhibit tumor growth in animals (see, e.g., Example 9, herein). 
     Epitope Mapping and Related Technologies 
     The ErbB3 protein, like all ErbB/HER family members, contains four extracellular domains, referred to as “Domain I,” “Domain II,” “Domain III,” and “Domain IV.” Domain I is the sequence of amino acids represented by amino acids 1 through 190 of SEQ ID NO:498; Domain II is the sequence of amino acids represented by amino acids 191 through 308 of SEQ ID NO:498; Domain III is the sequence of amino acids represented by amino acids 309 through 499 of SEQ ID NO:498; and Domain IV is the sequence of amino acids represented by amino acids 500 through 624 of SEQ ID NO:498. 
     The present invention includes anti-ErbB3 antibodies which interact with one or more epitopes found within Domain III of the extracellular domain of ErbB3. The epitope(s) may consist of one or more contiguous sequences of 3 or more (e.g., 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more) amino acids located within Domain III of ErbB3. Alternatively, the epitope may consist of a plurality of non-contiguous amino acids (or amino acid sequences) located within Domain III of ErbB3. According to certain embodiments of the present invention, anti-ErbB3 antibodies are provided which interact with one or more amino acids located within one or more Domain III amino acid segments selected from the group consisting of amino acids 345-367 of SEQ ID NO:498, amino acids 423-439 of SEQ ID NO:498; and amino acids 451-463 of SEQ ID NO:498. For example, the present invention includes anti-ErbB3 antibodies which interact with at least one amino acid within each of the aforementioned Domain III amino acid segments (i.e., within each of amino acids 345-367, 423-439, and 451-463 of SEQ ID NO:498). 
     Various techniques known to persons of ordinary skill in the art can be used to determine whether an antibody “interacts with one or more amino acids” within a polypeptide or protein. Exemplary techniques include, e.g., routine cross-blocking assay such as that described  Antibodies , Harlow and Lane (Cold Spring Harbor Press, Cold Spring Harb., N.Y.), alanine scanning mutational analysis, peptide blots analysis (Reineke, 2004, Methods Mol Biol 248:443-463), and peptide cleavage analysis. In addition, methods such as epitope excision, epitope extraction and chemical modification of antigens can be employed (Tomer, 2000, Protein Science 9:487-496). Another method that can be used to identify the amino acids within a polypeptide with which an antibody interacts is hydrogen/deuterium exchange detected by mass spectrometry. (See, e.g., Example 11 herein). In general terms, the hydrogen/deuterium exchange method involves deuterium-labeling the protein of interest, followed by binding the antibody to the deuterium-labeled protein. Next, the protein/antibody complex is transferred to water to allow hydrogen-deuterium exchange to occur at all residues except for the residues protected by the antibody (which remain deuterium-labeled). After dissociation of the antibody, the target protein is subjected to protease cleavage and mass spectrometry analysis, thereby revealing the deuterium-labeled residues which correspond to the specific amino acids with which the antibody interacts. See, e.g., Ehring (1999)  Analytical Biochemistry  267(2):252-259; Engen and Smith (2001)  Anal. Chem.  73:256A-265A. 
     The present invention further includes anti-ErbB3 antibodies that bind to the same epitope as any of the specific exemplary antibodies described herein (e.g., H1M1819N, H2M1821N, H2M1824N, H2M1827N, H1M1828N, H2M1829N, H2M1930N, H2M1934N, H2M1938N, H1M1940N, etc.). Likewise, the present invention also includes anti-ErbB3 antibodies that compete for binding to ErbB3 or an ErbB3 fragment with any of the specific exemplary antibodies described herein (e.g., H1M1819N, H2M1821N, H2M1824N, H2M1827N, H1M1828N, H2M1829N, H2M1930N, H2M1934N, H2M1938N, H1M1940N, etc.). 
     One can easily determine whether an antibody binds to the same epitope as, or competes for binding with, a reference anti-ErbB3 antibody by using routine methods known in the art. For example, to determine if a test antibody binds to the same epitope as a reference anti-ErbB3 antibody of the invention, the reference antibody is allowed to bind to an ErbB3 protein or peptide under saturating conditions. Next, the ability of a test antibody to bind to the ErbB3 molecule is assessed. If the test antibody is able to bind to ErbB3 following saturation binding with the reference anti-ErbB3 antibody, it can be concluded that the test antibody binds to a different epitope than the reference anti-ErbB3 antibody. On the other hand, if the test antibody is not able to bind to the ErbB3 molecule following saturation binding with the reference anti-ErbB3 antibody, then the test antibody may bind to the same epitope as the epitope bound by the reference anti-ErbB3 antibody of the invention. Additional routine experimentation (e.g., peptide mutation and binding analyses) can then be carried out to confirm whether the observed lack of binding of the test antibody is in fact due to binding to the same epitope as the reference antibody or if steric blocking (or another phenomenon) is responsible for the lack of observed binding. Experiments of this sort can be performed using ELISA, RIA, Biacore, flow cytometry or any other quantitative or qualitative antibody-binding assay available in the art. In accordance with certain embodiments of the present invention, two antibodies bind to the same (or overlapping) epitope if, e.g., a 1-, 5-, 10-, 20- or 100-fold excess of one antibody inhibits binding of the other by at least 50% but preferably 75%, 90% or even 99% as measured in a competitive binding assay (see, e.g., Junghans et al., Cancer Res. 1990:50:1495-1502). Alternatively, two antibodies are deemed to bind to the same epitope if essentially all amino acid mutations in the antigen that reduce or eliminate binding of one antibody reduce or eliminate binding of the other. Two antibodies are deemed to have “overlapping epitopes” if only a subset of the amino acid mutations that reduce or eliminate binding of one antibody reduce or eliminate binding of the other. 
     To determine if an antibody competes for binding with a reference anti-ErbB3 antibody, the above-described binding methodology is performed in two orientations: In a first orientation, the reference antibody is allowed to bind to an ErbB3 molecule under saturating conditions followed by assessment of binding of the test antibody to the ErbB3 molecule. In a second orientation, the test antibody is allowed to bind to an ErbB3 molecule under saturating conditions followed by assessment of binding of the reference antibody to the ErbB3 molecule. If, in both orientations, only the first (saturating) antibody is capable of binding to the ErbB3 molecule, then it is concluded that the test antibody and the reference antibody compete for binding to ErbB3. As will be appreciated by a person of ordinary skill in the art, an antibody that competes for binding with a reference antibody may not necessarily bind to the same epitope as the reference antibody, but may sterically block binding of the reference antibody by binding an overlapping or adjacent epitope. 
     Preparation of Human Antibodies 
     Methods for generating monoclonal antibodies, including fully human monoclonal antibodies are known in the art. Any such known methods can be used in the context of the present invention to make human antibodies that specifically bind to human ErbB3. 
     Using VELOCIMMUNE™ technology or any other known method for generating monoclonal antibodies, high affinity chimeric antibodies to ErbB3 are initially isolated having a human variable region and a mouse constant region. As in the experimental section below, the antibodies are characterized and selected for desirable characteristics, including affinity, selectivity, epitope, etc. The mouse constant regions are replaced with a desired human constant region to generate the fully human antibody of the invention, for example wild-type or modified IgG1 or IgG4. While the constant region selected may vary according to specific use, high affinity antigen-binding and target specificity characteristics reside in the variable region. 
     Bioequivalents 
     The anti-ErbB3 antibodies and antibody fragments of the present invention encompass proteins having amino acid sequences that vary from those of the described antibodies but that retain the ability to bind human ErbB3. Such variant antibodies and antibody fragments comprise one or more additions, deletions, or substitutions of amino acids when compared to parent sequence, but exhibit biological activity that is essentially equivalent to that of the described antibodies. Likewise, the anti-ErbB3 antibody-encoding DNA sequences of the present invention encompass sequences that comprise one or more additions, deletions, or substitutions of nucleotides when compared to the disclosed sequence, but that encode an anti-ErbB3 antibody or antibody fragment that is essentially bioequivalent to an anti-ErbB3 antibody or antibody fragment of the invention. Examples of such variant amino acid and DNA sequences are discussed above. 
     Two antigen-binding proteins, or antibodies, are considered bioequivalent if, for example, they are pharmaceutical equivalents or pharmaceutical alternatives whose rate and extent of absorption do not show a significant difference when administered at the same molar dose under similar experimental conditions, either single does or multiple dose. Some antibodies will be considered equivalents or pharmaceutical alternatives if they are equivalent in the extent of their absorption but not in their rate of absorption and yet may be considered bioequivalent because such differences in the rate of absorption are intentional and are reflected in the labeling, are not essential to the attainment of effective body drug concentrations on, e.g., chronic use, and are considered medically insignificant for the particular drug product studied. 
     In one embodiment, two antigen-binding proteins are bioequivalent if there are no clinically meaningful differences in their safety, purity, and potency. 
     In one embodiment, two antigen-binding proteins are bioequivalent if a patient can be switched one or more times between the reference product and the biological product without an expected increase in the risk of adverse effects, including a clinically significant change in immunogenicity, or diminished effectiveness, as compared to continued therapy without such switching. 
     In one embodiment, two antigen-binding proteins are bioequivalent if they both act by a common mechanism or mechanisms of action for the condition or conditions of use, to the extent that such mechanisms are known. 
     Bioequivalence may be demonstrated by in vivo and in vitro methods. Bioequivalence measures include, e.g., (a) an in vivo test in humans or other mammals, in which the concentration of the antibody or its metabolites is measured in blood, plasma, serum, or other biological fluid as a function of time; (b) an in vitro test that has been correlated with and is reasonably predictive of human in vivo bioavailability data; (c) an in vivo test in humans or other mammals in which the appropriate acute pharmacological effect of the antibody (or its target) is measured as a function of time; and (d) in a well-controlled clinical trial that establishes safety, efficacy, or bioavailability or bioequivalence of an antibody. 
     Bioequivalent variants of anti-ErbB3 antibodies of the invention may be constructed by, for example, making various substitutions of residues or sequences or deleting terminal or internal residues or sequences not needed for biological activity. For example, cysteine residues not essential for biological activity can be deleted or replaced with other amino acids to prevent formation of unnecessary or incorrect intramolecular disulfide bridges upon renaturation. In other contexts, bioequivalent antibodies may include anti-ErbB3 antibody variants comprising amino acid changes which modify the glycosylation characteristics of the antibodies, e.g., mutations which eliminate or remove glycosylation. 
     Species Selectivity and Species Cross-Reactivity 
     According to certain embodiments of the invention, the anti-ErbB3 antibodies bind to human ErbB3 but not to ErbB3 from other species. The present invention also includes anti-ErbB3 antibodies that bind to human ErbB3 and to ErbB3 from one or more non-human species. For example, the anti-ErbB3 antibodies of the invention may bind to human ErbB3 and may bind or not bind, as the case may be, to one or more of mouse, rat, guinea pig, hamster, gerbil, pig, cat, dog, rabbit, goat, sheep, cow, horse, camel, cynomologous, marmoset, rhesus or chimpanzee ErbB3. 
     Immunoconjugates 
     The invention encompasses anti-ErbB3 monoclonal antibodies conjugated to a therapeutic moiety (“immunoconjugate”), such as a cytotoxin, a chemotherapeutic drug, an immunosuppressant or a radioisotope. Cytotoxic agents include any agent that is detrimental to cells. Examples of suitable cytotoxic agents and chemotherapeutic agents for forming immunoconjugates are known in the art, (see for example, WO 05/103081). 
     Multispecific Antibodies 
     The antibodies of the present invention may be monospecific, bi-specific, or multispecific. Multispecific antibodies may be specific for different epitopes of one target polypeptide or may contain antigen-binding domains specific for more than one target polypeptide. See, e.g., Tutt et al., 1991, J. Immunol. 147:60-69; Kufer et al., 2004, Trends Biotechnol. 22:238-244. The anti-ErbB3 antibodies of the present invention can be linked to or co-expressed with another functional molecule, e.g., another peptide or protein. For example, an antibody or fragment thereof can be functionally linked (e.g., by chemical coupling, genetic fusion, noncovalent association or otherwise) to one or more other molecular entities, such as another antibody or antibody fragment to produce a bi-specific or a multispecific antibody with a second binding specificity. For example, the present invention includes bi-specific antibodies wherein one arm of an immunoglobulin is specific for human ErbB3 or a fragment thereof, and the other arm of the immunoglobulin is specific for a second therapeutic target (e.g., EGFR, EGFRvIII, ErbB2/HER2, ErbB4, VEGF or Ang2) or is conjugated to a therapeutic moiety. 
     An exemplary bi-specific antibody format that can be used in the context of the present invention involves the use of a first immunoglobulin (Ig) C H 3 domain and a second Ig C H 3 domain, wherein the first and second Ig C H 3 domains differ from one another by at least one amino acid, and wherein at least one amino acid difference reduces binding of the bispecific antibody to Protein A as compared to a bi-specific antibody lacking the amino acid difference. In one embodiment, the first Ig C H 3 domain binds Protein A and the second Ig C H 3 domain contains a mutation that reduces or abolishes Protein A binding such as an H95R modification (by IMGT exon numbering; H435R by EU numbering). The second C H 3 may further comprise a Y96F modification (by IMGT; Y436F by EU). Further modifications that may be found within the second C H 3 include: D16E, L18M, N44S, K52N, V57M, and V82I (by IMGT; D356E, L358M, N384S, K392N, V397M, and V422I by EU) in the case of IgG1 antibodies; N44S, K52N, and V82I (IMGT; N384S, K392N, and V422I by EU) in the case of IgG2 antibodies; and Q15R, N44S, K52N, V57M, R69K, E79Q, and V82I (by IMGT; Q355R, N384S, K392N, V397M, R409K, E419Q, and V422I by EU) in the case of IgG4 antibodies. Variations on the bi-specific antibody format described above are contemplated within the scope of the present invention. 
     Therapeutic Formulation and Administration 
     The invention provides pharmaceutical compositions comprising the anti-ErbB3 antibodies or antigen-binding fragments thereof of the present invention. The pharmaceutical compositions of the invention are formulated with suitable carriers, excipients, and other agents that provide improved transfer, delivery, tolerance, and the like. A multitude of appropriate formulations can be found in the formulary known to all pharmaceutical chemists: Remington&#39;s Pharmaceutical Sciences, Mack Publishing Company, Easton, Pa. These formulations include, for example, powders, pastes, ointments, jellies, waxes, oils, lipids, lipid (cationic or anionic) containing vesicles (such as LIPOFECTIN™), DNA conjugates, anhydrous absorption pastes, oil-in-water and water-in-oil emulsions, emulsions carbowax (polyethylene glycols of various molecular weights), semi-solid gels, and semi-solid mixtures containing carbowax. See also Powell et al. “Compendium of excipients for parenteral formulations” PDA (1998) J Pharm Sci Technol 52:238-311. 
     The dose of antibody administered to a patient may vary depending upon the age and the size of the patient, target disease, conditions, route of administration, and the like. The preferred dose is typically calculated according to body weight or body surface area. When an antibody of the present invention is used for treating a condition or disease associated with ErbB3 activity in an adult patient, it may be advantageous to intravenously administer the antibody of the present invention normally at a single dose of about 0.01 to about 20 mg/kg body weight, more preferably about 0.02 to about 7, about 0.03 to about 5, or about 0.05 to about 3 mg/kg body weight. Depending on the severity of the condition, the frequency and the duration of the treatment can be adjusted. Effective dosages and schedules for administering anti-ErbB3 antibodies may be determined empirically; for example, patient progress can be monitored by periodic assessment, and the dose adjusted accordingly. Moreover, interspecies scaling of dosages can be performed using well-known methods in the art (e.g., Mordenti et al., 1991 , Pharmaceut. Res.  8:1351). 
     Various delivery systems are known and can be used to administer the pharmaceutical composition of the invention, e.g., encapsulation in liposomes, microparticles, microcapsules, recombinant cells capable of expressing the mutant viruses, receptor mediated endocytosis (see, e.g., Wu et al., 1987, J. Biol. Chem. 262:4429-4432). Methods of introduction include, but are not limited to, intradermal, intramuscular, intraperitoneal, intravenous, subcutaneous, intranasal, epidural, and oral routes. The composition may be administered by any convenient route, for example by infusion or bolus injection, by absorption through epithelial or mucocutaneous linings (e.g., oral mucosa, rectal and intestinal mucosa, etc.) and may be administered together with other biologically active agents. Administration can be systemic or local. 
     A pharmaceutical composition of the present invention can be delivered subcutaneously or intravenously with a standard needle and syringe. In addition, with respect to subcutaneous delivery, a pen delivery device readily has applications in delivering a pharmaceutical composition of the present invention. Such a pen delivery device can be reusable or disposable. A reusable pen delivery device generally utilizes a replaceable cartridge that contains a pharmaceutical composition. Once all of the pharmaceutical composition within the cartridge has been administered and the cartridge is empty, the empty cartridge can readily be discarded and replaced with a new cartridge that contains the pharmaceutical composition. The pen delivery device can then be reused. In a disposable pen delivery device, there is no replaceable cartridge. Rather, the disposable pen delivery device comes prefilled with the pharmaceutical composition held in a reservoir within the device. Once the reservoir is emptied of the pharmaceutical composition, the entire device is discarded. 
     Numerous reusable pen and autoinjector delivery devices have applications in the subcutaneous delivery of a pharmaceutical composition of the present invention. Examples include, but are not limited to AUTOPEN™ (Owen Mumford, Inc., Woodstock, UK), DISETRONIC™ pen (Disetronic Medical Systems, Bergdorf, Switzerland), HUMALOG MIX 75/25™ pen, HUMALOG™ pen, HUMALIN 70/30™ pen (Eli Lilly and Co., Indianapolis, Ind.), NOVOPEN™ I, II and III (Novo Nordisk, Copenhagen, Denmark), NOVOPEN JUNIOR™ (Novo Nordisk, Copenhagen, Denmark), BD™ pen (Becton Dickinson, Franklin Lakes, N.J.), OPTIPEN™, OPTIPEN PRO™, OPTIPEN STARLET™, and OPTICLIK™ (sanofi-aventis, Frankfurt, Germany), to name only a few. Examples of disposable pen delivery devices having applications in subcutaneous delivery of a pharmaceutical composition of the present invention include, but are not limited to the SOLOSTAR™ pen (sanofi-aventis), the FLEXPEN™ (Novo Nordisk), and the KWIKPEN™ (Eli Lilly), the SURECLICK™ Autoinjector (Amgen, Thousand Oaks, Calif.), the PENLET™ (Haselmeier, Stuttgart, Germany), the EPIPEN (Dey, L.P.), and the HUMIRA™ Pen (Abbott Labs, Abbott Park Ill.), to name only a few. 
     In certain situations, the pharmaceutical composition can be delivered in a controlled release system. In one embodiment, a pump may be used (see Langer, supra; Sefton, 1987, CRC Crit. Ref. Biomed. Eng. 14:201). In another embodiment, polymeric materials can be used; see, Medical Applications of Controlled Release, Langer and Wise (eds.), 1974, CRC Pres., Boca Raton, Fla. In yet another embodiment, a controlled release system can be placed in proximity of the composition&#39;s target, thus requiring only a fraction of the systemic dose (see, e.g., Goodson, 1984, in Medical Applications of Controlled Release, supra, vol. 2, pp. 115-138). Other controlled release systems are discussed in the review by Langer, 1990, Science 249:1527-1533. 
     The injectable preparations may include dosage forms for intravenous, subcutaneous, intracutaneous and intramuscular injections, drip infusions, etc. These injectable preparations may be prepared by methods publicly known. For example, the injectable preparations may be prepared, e.g., by dissolving, suspending or emulsifying the antibody or its salt described above in a sterile aqueous medium or an oily medium conventionally used for injections. As the aqueous medium for injections, there are, for example, physiological saline, an isotonic solution containing glucose and other auxiliary agents, etc., which may be used in combination with an appropriate solubilizing agent such as an alcohol (e.g., ethanol), a polyalcohol (e.g., propylene glycol, polyethylene glycol), a nonionic surfactant [e.g., polysorbate 80, HCO-50 (polyoxyethylene (50 mol) adduct of hydrogenated castor oil)], etc. As the oily medium, there are employed, e.g., sesame oil, soybean oil, etc., which may be used in combination with a solubilizing agent such as benzyl benzoate, benzyl alcohol, etc. The injection thus prepared is preferably filled in an appropriate ampoule. 
     Advantageously, the pharmaceutical compositions for oral or parenteral use described above are prepared into dosage forms in a unit dose suited to fit a dose of the active ingredients. Such dosage forms in a unit dose include, for example, tablets, pills, capsules, injections (ampoules), suppositories, etc. The amount of the aforesaid antibody contained is generally about 5 to about 500 mg per dosage form in a unit dose; especially in the form of injection, it is preferred that the aforesaid antibody is contained in about 5 to about 100 mg and in about 10 to about 250 mg for the other dosage forms. 
     Therapeutic Uses of the Antibodies 
     The antibodies of the invention are useful, inter alia, for the treatment, prevention and/or amelioration of any disease or disorder associated with or mediated by ErbB3 activity or treatable by blocking the interaction between ErbB3 and an ErbB3 ligand (e.g., NRG1). The antibodies and antigen-binding fragments of the present invention may be used to treat, e.g., primary and/or metastatic tumors arising in the brain and meninges, oropharynx, lung and bronchial tree, gastrointestinal tract, male and female reproductive tract, muscle, bone, skin and appendages, connective tissue, spleen, immune system, blood forming cells and bone marrow, liver and urinary tract, and special sensory organs such as the eye. In certain embodiments, the antibodies and antigen-binding fragments of the invention are used to treat one or more of the following cancers: renal cell carcinoma, pancreatic carcinoma, breast cancer, head and neck cancer, prostate cancer, malignant gliomas, osteosarcoma, colorectal cancer, gastric cancer (e.g., gastric cancer with MET amplification), malignant mesothelioma, multiple myeloma, ovarian cancer, small cell lung cancer, non-small cell lung cancer (e.g., EGFR-dependent non-small cell lung cancer), synovial sarcoma, thyroid cancer, or melanoma. 
     The present invention also provides methods for treating a tumor which is resistant to, or has become resistant to anti-EGFR or anti-HER2 therapy. For example, the present invention includes methods which comprise (a) identifying a patient having a tumor which is resistant, or has become resistant, to one or more of an anti-EGFR antibody (e.g., cetuximab), a small molecule inhibitor of EGFR (e.g., erlotinib), an anti-HER2 antibody (e.g. trastuzumab), and/or a small molecule inhibitor of HER2; and (b) administering to the patient an anti-ErbB3 antibody of the present invention, either alone, or in combination with an anti-EGFR antibody (e.g., cetuximab), a small molecule inhibitor of EGFR (e.g., erlotinib), an anti-HER2 antibody (e.g. trastuzumab), and/or a small molecule inhibitor of HER2. Combination therapies are discussed in more detail below. 
     Combination Therapies 
     The present invention includes therapeutic administration regimens which comprise administering an anti-ErbB3 antibody of the present invention in combination with at least one additional therapeutically active component. Non-limiting examples of such additional therapeutically active components include other ErbB3 antagonists (e.g., a second anti-ErbB3 antibody or small molecule inhibitor of ErbB3), an antagonist of ErbB2/HER2 (e.g., anti-HER2 antibody [e.g., trastuzumab] or small molecule inhibitor of HER2 activity), an antagonist of ErbB4 (e.g., anti-ErbB4 antibody or small molecule inhibitor of ErbB4 activity), an antagonist of epidermal growth factor receptor (EGFR) (e.g., anti-EGFR antibody [e.g., cetuximab or panitumumab] or small molecule inhibitor of EGFR activity [e.g., erlotinib or gefitinib]), an antagonist of EGFRvIII (e.g., an antibody that specifically binds EGFRvIII), a VEGF antagonist (e.g., a VEGF-Trap, see, e.g., U.S. Pat. No. 7,087,411 (also referred to herein as a “VEGF-inhibiting fusion protein”), anti-VEGF antibody (e.g., bevacizumab), a small molecule kinase inhibitor of VEGF receptor (e.g., sunitinib, sorafenib or pazopanib), or an anti-DLL4 antibody (e.g., an anti-DLL4 antibody disclosed in US 2009/0142354 such as REGN421), etc.). Other agents that may be beneficially administered in combination with the anti-ErbB3 antibodies of the invention include cytokine inhibitors, including small-molecule cytokine inhibitors and antibodies that bind to cytokines such as IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, IL-8, IL-9, IL-11, IL-12, IL-13, IL-17, IL-18, or to their respective receptors. The present invention also includes therapeutic combinations comprising any of the anti-ErbB3 antibodies mentioned herein and an inhibitor of one or more of VEGF, DLL4, EGFR, or any of the aforementioned cytokines, wherein the inhibitor is an aptamer, an antisense molecule, a ribozyme, an siRNA, a peptibody, a nanobody or an antibody fragment (e.g., Fab fragment; F(ab′) 2  fragment; Fd fragment; Fv fragment; scFv; dAb fragment; or other engineered molecules, such as diabodies, triabodies, tetrabodies, minibodies and minimal recognition units). The anti-ErbB3 antibodies of the invention may also be administered in combination with antivirals, antibiotics, analgesics, corticosteroids and/or NSAIDs. The anti-ErbB3 antibodies of the invention may also be administered as part of a treatment regimen that also includes radiation treatment and/or conventional chemotherapy. The additional therapeutically active component(s) may be administered prior to, concurrent with, or after the administration of an anti-ErbB3 antibody of the present invention; (for purposes of the present disclosure, such administration regimens are considered the administration of an anti-ErbB3 antibody “in combination with” a therapeutically active component of the invention). 
     Administration Regimens 
     According to certain embodiments of the present invention, multiple doses of an anti-ErbB3 antibody may be administered to a subject over a defined time course. The methods according to this aspect of the invention comprise sequentially administering to a subject multiple doses of an anti-ErbB3 antibody. As used herein, “sequentially administering” means that each dose of anti-ErbB3 antibody is administered to the subject at a different point in time, e.g., on different days separated by a predetermined interval (e.g., hours, days, weeks or months). The present invention includes methods which comprise sequentially administering to the patient a single initial dose of an anti-ErbB3 antibody, followed by one or more secondary doses of the anti-ErbB3 antibody, and optionally followed by one or more tertiary doses of the anti-ErbB3 antibody. 
     The terms “initial dose,” “secondary doses,” and “tertiary doses,” refer to the temporal sequence of administration of the anti-ErbB3 antibody. Thus, the “initial dose” is the dose which is administered at the beginning of the treatment regimen (also referred to as the “baseline dose”); the “secondary doses” are the doses which are administered after the initial dose; and the “tertiary doses” are the doses which are administered after the secondary doses. The initial, secondary, and tertiary doses may all contain the same amount of anti-ErbB3 antibody, but generally may differ from one another in terms of frequency of administration. In certain embodiments, however, the amount of anti-ErbB3 antibody contained in the initial, secondary and/or tertiary doses varies from one another (e.g., adjusted up or down as appropriate) during the course of treatment. In certain embodiments, two or more (e.g., 2, 3, 4, or 5) doses are administered at the beginning of the treatment regimen as “loading doses” followed by subsequent doses that are administered on a less frequent basis (e.g., “maintenance doses”). 
     In one exemplary embodiment of the present invention, each secondary and/or tertiary dose is administered 1 to 26 (e.g., 1, 1%, 2, 2%, 3, 3%, 4, 4%, 5, 5%, 6, 6%, 7, 7%, 8, 8%, 9, 9%, 10, 10%, 11, 11%, 12, 12%, 13, 13%, 14, 14%, 15, 15%, 16, 16%, 17, 17%, 18, 18%, 19, 19%, 20, 20%, 21, 21%, 22, 22%, 23, 23%, 24, 24%, 25, 25%, 26, 26%, or more) weeks after the immediately preceding dose. The phrase “the immediately preceding dose,” as used herein, means, in a sequence of multiple administrations, the dose of anti-ErbB3 antibody which is administered to a patient prior to the administration of the very next dose in the sequence with no intervening doses. 
     The methods according to this aspect of the invention may comprise administering to a patient any number of secondary and/or tertiary doses of an anti-ErbB3 antibody. For example, in certain embodiments, only a single secondary dose is administered to the patient. In other embodiments, two or more (e.g., 2, 3, 4, 5, 6, 7, 8, or more) secondary doses are administered to the patient. Likewise, in certain embodiments, only a single tertiary dose is administered to the patient. In other embodiments, two or more (e.g., 2, 3, 4, 5, 6, 7, 8, or more) tertiary doses are administered to the patient. 
     In embodiments involving multiple secondary doses, each secondary dose may be administered at the same frequency as the other secondary doses. For example, each secondary dose may be administered to the patient 1 to 2 weeks after the immediately preceding dose. Similarly, in embodiments involving multiple tertiary doses, each tertiary dose may be administered at the same frequency as the other tertiary doses. For example, each tertiary dose may be administered to the patient 2 to 4 weeks after the immediately preceding dose. Alternatively, the frequency at which the secondary and/or tertiary doses are administered to a patient can vary over the course of the treatment regimen. The frequency of administration may also be adjusted during the course of treatment by a physician depending on the needs of the individual patient following clinical examination. 
     Any of the exemplary anti-ErbB3 antibodies disclosed herein may be used in the context of the foregoing administration regimens. 
     Diagnostic Uses of the Antibodies 
     The anti-ErbB3 antibodies of the present invention may also be used to detect and/or measure ErbB3 in a sample, e.g., for diagnostic purposes. For example, an anti-ErbB3 antibody, or fragment thereof, may be used to diagnose a condition or disease characterized by aberrant expression (e.g., over-expression, under-expression, lack of expression, etc.) of ErbB3. Exemplary diagnostic assays for ErbB3 may comprise, e.g., contacting a sample, obtained from a patient, with an anti-ErbB3 antibody of the invention, wherein the anti-ErbB3 antibody is labeled with a detectable label or reporter molecule. Alternatively, an unlabeled anti-ErbB3 antibody can be used in diagnostic applications in combination with a secondary antibody which is itself detectably labeled. The detectable label or reporter molecule can be a radioisotope, such as  3 H,  14 C,  32 P,  35 S, or  125 I; a fluorescent or chemiluminescent moiety such as fluorescein isothiocyanate, or rhodamine; or an enzyme such as alkaline phosphatase, beta-galactosidase, horseradish peroxidase, or luciferase. Specific exemplary assays that can be used to detect or measure ErbB3 in a sample include enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA), and fluorescence-activated cell sorting (FACS). 
     Samples that can be used in ErbB3 diagnostic assays according to the present invention include any tissue or fluid sample obtainable from a patient which contains detectable quantities of ErbB3 protein, or fragments thereof, under normal or pathological conditions. Generally, levels of ErbB3 in a particular sample obtained from a healthy patient (e.g., a patient not afflicted with a disease or condition associated with abnormal ErbB3 levels or activity) will be measured to initially establish a baseline, or standard, level of ErbB3. This baseline level of ErbB3 can then be compared against the levels of ErbB3 measured in samples obtained from individuals suspected of having a ErbB3 related disease or condition. 
     EXAMPLES 
     The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the methods and compositions of the invention, and are not intended to limit the scope of what the inventors regard as their invention. Efforts have been made to ensure accuracy with respect to numbers used (e.g., amounts, temperature, etc.) but some experimental errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, molecular weight is average molecular weight, temperature is in degrees Centigrade, and pressure is at or near atmospheric. 
     Example 1. Generation of Human Antibodies to Human ErbB3 
     An immunogen comprising the ecto-domain of human ErbB3 was administered directly, with an adjuvant to stimulate the immune response, to a VELOCIMMUNE® mouse comprising DNA encoding human Immunoglobulin heavy and kappa light chain variable regions. The antibody immune response was monitored by a ErbB3-specific immunoassay. When a desired immune response was achieved splenocytes were harvested and fused with mouse myeloma cells to preserve their viability and form hybridoma cell lines. The hybridoma cell lines were screened and selected to identify cell lines that produce ErbB3-specific antibodies. Using this technique several anti-ErbB3 chimeric antibodies (i.e., antibodies possessing human variable domains and mouse constant domains) were obtained; exemplary antibodies generated in this manner were designated as follows: H1M1819N, H2M1821N, H2M1824N, H2M1827N, H1M1828N, H2M1829N, H2M1930N, H2M1934N, H2M1936N, H2M1937N, H2M1938N, and H1M1940N. 
     Anti-ErbB3 antibodies were also isolated directly from antigen-positive B cells without fusion to myeloma cells, as described in US 2007/0280945A1. Using this method, several fully human anti-ErbB3 antibodies (i.e., antibodies possessing human variable domains and human constant domains) were obtained; exemplary antibodies generated in this manner were designated as follows: H4H2084P, H4H2092P, H4H2094P, H4H2098P, H4H2102P, H4H2108P, H4H2111P, H4H2114P, H4H2132P, H4H2138P, H4H2140P, H4H2143P, H4H2146P, H4H2147P, H4H2148P, H4H2151P, H4H2153P, H4H2154P, and H4H2290P. 
     Certain biological properties of the exemplary anti-ErbB3 antibodies generated in accordance with the methods of this Example are described in detail in the Examples set forth below. 
     Example 2. Heavy and Light Chain Variable Region Amino Acid Sequences 
     Table 1 sets forth the heavy and light chain variable region amino acid sequence pairs of selected anti-ErbB3 antibodies and their corresponding antibody identifiers. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Antibody 
                 SEQ ID NOs: 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Designation 
                 HCVR 
                 HCDR1 
                 HCDR2 
                 HCDR3 
                 LCVR 
                 LCDR1 
                 LCDR2 
                 LCDR3 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 2084P 
                 2 
                 4 
                 6 
                 8 
                 10 
                 12 
                 14 
                 16 
               
               
                 2092P 
                 18 
                 20 
                 22 
                 24 
                 26 
                 28 
                 30 
                 32 
               
               
                 2094P 
                 34 
                 36 
                 38 
                 40 
                 42 
                 44 
                 46 
                 48 
               
               
                 2098P 
                 50 
                 52 
                 54 
                 56 
                 58 
                 60 
                 62 
                 64 
               
               
                 2102P 
                 66 
                 68 
                 70 
                 72 
                 74 
                 76 
                 78 
                 80 
               
               
                 2108P 
                 82 
                 84 
                 86 
                 88 
                 90 
                 92 
                 94 
                 96 
               
               
                 2111P 
                 98 
                 100 
                 102 
                 104 
                 106 
                 108 
                 110 
                 112 
               
               
                 2114P 
                 114 
                 116 
                 118 
                 120 
                 122 
                 124 
                 126 
                 128 
               
               
                 2132P 
                 130 
                 132 
                 134 
                 136 
                 138 
                 140 
                 142 
                 144 
               
               
                 2138P 
                 146 
                 148 
                 150 
                 152 
                 154 
                 156 
                 158 
                 160 
               
               
                 2140P 
                 162 
                 164 
                 166 
                 168 
                 170 
                 172 
                 174 
                 176 
               
               
                 2143P 
                 178 
                 180 
                 182 
                 184 
                 186 
                 188 
                 190 
                 192 
               
               
                 2146P 
                 194 
                 196 
                 198 
                 200 
                 202 
                 204 
                 206 
                 208 
               
               
                 2147P 
                 210 
                 212 
                 214 
                 216 
                 218 
                 220 
                 222 
                 224 
               
               
                 2148P 
                 226 
                 228 
                 230 
                 232 
                 234 
                 236 
                 238 
                 240 
               
               
                 2151P 
                 242 
                 244 
                 246 
                 248 
                 250 
                 252 
                 254 
                 256 
               
               
                 2153P 
                 258 
                 260 
                 262 
                 264 
                 266 
                 268 
                 270 
                 272 
               
               
                 2154P 
                 274 
                 276 
                 278 
                 280 
                 282 
                 284 
                 286 
                 288 
               
               
                 2290P 
                 290 
                 292 
                 294 
                 296 
                 298 
                 300 
                 302 
                 304 
               
               
                 1819N 
                 306 
                 308 
                 310 
                 312 
                 314 
                 316 
                 318 
                 320 
               
               
                 1821N 
                 322 
                 324 
                 326 
                 328 
                 330 
                 332 
                 334 
                 336 
               
               
                 1824N 
                 338 
                 340 
                 342 
                 344 
                 346 
                 348 
                 350 
                 352 
               
               
                 1827N 
                 354 
                 356 
                 358 
                 360 
                 362 
                 364 
                 366 
                 368 
               
               
                 1828N 
                 370 
                 372 
                 374 
                 376 
                 378 
                 380 
                 382 
                 384 
               
               
                 1829N 
                 386 
                 388 
                 390 
                 392 
                 394 
                 396 
                 398 
                 400 
               
               
                 1930N 
                 402 
                 404 
                 406 
                 408 
                 410 
                 412 
                 414 
                 416 
               
               
                 1934N 
                 418 
                 420 
                 422 
                 424 
                 426 
                 428 
                 430 
                 432 
               
               
                 1936N 
                 434 
                 436 
                 438 
                 440 
                 442 
                 444 
                 446 
                 448 
               
               
                 1937N 
                 450 
                 452 
                 454 
                 456 
                 458 
                 460 
                 462 
                 464 
               
               
                 1938N 
                 466 
                 468 
                 470 
                 472 
                 474 
                 476 
                 478 
                 480 
               
               
                 1940N 
                 482 
                 484 
                 486 
                 488 
                 490 
                 492 
                 494 
                 496 
               
               
                   
               
            
           
         
       
     
     Antibodies are typically referred to herein according to the following nomenclature: Fc prefix (e.g. “H4H”, “H1M”, “H2M”), followed by a numerical identifier (e.g. “2084” as shown in Table 1), followed by a “P” or “N” suffix. Thus, according to this nomenclature, an antibody may be referred to herein as, e.g., “H4H2084P”. The H4H, H1M, and H2M prefixes on the antibody designations used herein indicate the particular Fc region of the antibody. For example, an “H2M” antibody has a mouse IgG2 Fc, whereas an “H4H” antibody has a human IgG4 Fc. As will be appreciated by a person of ordinary skill in the art, an H1M or H2M antibody can be converted to an H4H antibody, and vice versa, but in any event, the variable domains (including the CDRs)—which are indicated by the numerical identifiers shown in Table 1—will remain the same. The P and N suffixes on the antibody designations used herein refer to antibodies having heavy and light chains with identical CDR sequences but with sequence variations in regions that fall outside of the CDR sequences (i.e., in the framework regions). Thus, P and N variants of a particular antibody have identical CDR sequences within their heavy and light chain variable regions but differ from one another within their framework regions. 
     Control Constructs Used in the Following Examples 
     Various control constructs (anti-ErbB3 antibodies) were included in the following experiments for comparative purposes. The control constructs are designated as follows: Control I: a human anti-ErbB3 antibody with heavy and light chain variable domains having the amino acid sequences of the corresponding domains of “Mab #6,” as set forth in U.S. Pat. No. 7,846,440; Control II: a human anti-ErbB3 antibody with heavy and light chain variable domains having the amino acid sequences of the corresponding domains of “U1-59,” as set forth in U.S. Pat. No. 7,705,130; and Control III: a human anti-ErbB3 antibody with heavy and light chain variable domains having the amino acid sequences of the corresponding domains of “U1-53,” as set forth in U.S. Pat. No. 7,705,130. 
     Example 3. Surface Plasmon Resonance Derived Binding Affinities and Kinetic Constants of Human Monoclonal Anti-ErbB3 Antibodies 
     Binding affinities and kinetic constants of human monoclonal anti-ErbB3 antibodies were determined by surface plasmon resonance at 25° C. and 37° C. (Tables 2-4). Measurements were conducted on a Biacore 2000 or T100 instrument. Antibodies, expressed with either mouse Fc (prefix H1M; H2M) or human IgG4 Fc (prefix H4H), were captured on an anti-mouse or anti human-Fc sensor surface (Mab capture format), and soluble monomeric (ErbB3.mmh; SEQ ID NO:497) or dimeric (ErbB3-hFc; SEQ ID NO:498 or ErbB3-mFc; SEQ ID NO:499) protein was injected over the surface. Kinetic association (k a ) and dissociation (k d ) rate constants were determined by processing and fitting the data to a 1:1 binding model using Scrubber 2.0 curve fitting software. Binding dissociation equilibrium constants (K D ) and dissociative half-lives (t 1/2 ) were calculated from the kinetic rate constants as: K D  (M)=k d /k a ; and t 1/2  (min)=(ln 2/(60*k d ). Several clones showed sub-nanomolar affinity to monomeric (hErbB3.mmh) ErbB3 protein. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Biacore Binding Affinities of Hybridoma mAbs (H1M and H2M) at 25° C. 
               
               
                 Binding at 25° C./Mab Capture Format 
               
            
           
           
               
               
               
               
               
               
            
               
                 Antibody 
                 Analyte 
                 ka (Ms −1 ) 
                 kd (s −1 ) 
                 K D  (Molar) 
                 T½ 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 H1M1819N 
                 hErbB3.mmh 
                 3.19E+05 
                 3.22E−04 
                 1.01E−09 
                 36 
               
               
                   
                 hErbB3.hFc 
                 4.80E+05 
                 5.88E−05 
                 1.22E−10 
                 196 
               
               
                 H2M1821N 
                 hErbB3.mmh 
                 2.29E+05 
                 1.99E−04 
                 8.67E−10 
                 58 
               
               
                   
                 hErbB3.hFc 
                 4.61E+05 
                 1.90E−05 
                 4.13E−11 
                 608 
               
               
                 H2M1824N 
                 hErbB3.mmh 
                 2.23E+05 
                 4.56E−05 
                 2.05E−10 
                 254 
               
               
                   
                 hErbB3.hFc 
                 4.31E+05 
                 1.44E−06 
                 3.34E−12 
                 8026 
               
               
                 H2M1827N 
                 hErbB3.mmh 
                 2.19E+05 
                 8.96E−05 
                 4.09E−10 
                 129 
               
               
                   
                 hErbB3.hFc 
                 4.39E+05 
                 7.58E−06 
                 1.73E−11 
                 1524 
               
               
                 H1M1828N 
                 hErbB3.mmh 
                 5.13E+05 
                 2.65E−04 
                 5.15E−10 
                 44 
               
               
                   
                 hErbB3.hFc 
                 1.56E+06 
                 4.34E−05 
                 2.79E−11 
                 266 
               
               
                 H2M1829N 
                 hErbB3.mmh 
                 2.30E+05 
                 6.46E−05 
                 2.81E−10 
                 179 
               
               
                   
                 hErbB3.hFc 
                 4.36E+05 
                 8.61E−06 
                 1.98E−11 
                 1341 
               
               
                 H2M1930N 
                 hErbB3.mmh 
                 1.96E+05 
                 1.09E−04 
                 5.59E−10 
                 106 
               
               
                   
                 hErbB3.hFc 
                 4.04E+05 
                 8.27E−06 
                 2.05E−11 
                 1396 
               
               
                 H2M1934N 
                 hErbB3.mmh 
                 1.68E+05 
                 7.35E−05 
                 4.38E−10 
                 157 
               
               
                   
                 hErbB3.hFc 
                 3.59E+05 
                 7.97E−06 
                 2.22E−11 
                 1450 
               
               
                 H2M1936N 
                 hErbB3.mmh 
                 4.32E+04 
                 2.85E−04 
                 6.59E−09 
                 41 
               
               
                   
                 hErbB3.hFc 
                 6.41E+04 
                 6.97E−05 
                 1.09E−09 
                 166 
               
               
                 H2M1937N 
                 hErbB3.mmh 
                 8.26E+04 
                 5.63E−05 
                 6.82E−10 
                 205 
               
               
                   
                 hErbB3.hFc 
                 1.10E+05 
                 1.27E−05 
                 1.16E−10 
                 908 
               
               
                 H2M1938N 
                 hErbB3.mmh 
                 2.41E+05 
                 1.44E−04 
                 5.99E−10 
                 80 
               
               
                   
                 hErbB3.hFc 
                 4.51E+05 
                 1.36E−05 
                 3.01E−11 
                 851 
               
               
                 H1M1940N 
                 hErbB3.mmh 
                 2.89E+05 
                 1.38E−04 
                 4.77E−10 
                 84 
               
               
                   
                 hErbB3.hFc 
                 4.60E+05 
                 2.43E−05 
                 5.29E−11 
                 475 
               
               
                 Control I 
                 hErbB3.mmh 
                 5.14E+04 
                 2.15E−04 
                 4.18E−09 
                 54 
               
               
                   
                 hErbB3.hFc 
                 4.63E+04 
                 1.63E−05 
                 3.51E−10 
                 711 
               
               
                 Control II 
                 hErbB3.mmh 
                 1.41E+05 
                 3.24E−04 
                 2.30E−09 
                 36 
               
               
                   
                 hErbB3.hFc 
                 1.53E+05 
                 4.28E−05 
                 2.80E−10 
                 270 
               
               
                 Control III 
                 hErbB3.mmh 
                 1.54E+06 
                 3.15E−02 
                 2.05E−08 
                 0.4 
               
               
                   
                 hErbB3.hFc 
                 3.78E+06 
                 8.84E−05 
                 2.34E−11 
                 131 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Biacore Binding Affinities of Human Fc mAbs (H4H) at 25° C. 
               
               
                 Binding at 25° C./Mab Capture Format 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Analyte 
                 ka (Ms −1 ) 
                 kd (s −1 ) 
                 K D  (Molar) 
                 T½ 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 H4H1819N 
                 hErbB3.mmh 
                 8.10E+06 
                 3.51E−04 
                 4.35E−11 
                 33 
               
               
                   
                 hErbB3.mFc 
                 1.64E+07 
                 1.54E−05 
                 9.43E−13 
                 748 
               
               
                 H4H1821N 
                 hErbB3.mmh 
                 3.80E+06 
                 1.92E−04 
                 5.10E−11 
                 60 
               
               
                   
                 hErbB3.mFc 
                 1.22E+07 
                 4.33E−06 
                 3.55E−13 
                 2665 
               
               
                 H4H2084P 
                 hErbB3.mmh 
                 2.49E+06 
                 5.96E−05 
                 2.39E−11 
                 179 
               
               
                   
                 hErbB3.mFc 
                 3.83E+06 
                 3.95E−06 
                 1.03E−12 
                 2695 
               
               
                 H4H2092P 
                 hErbB3.mmh 
                 3.72E+06 
                 1.03E−04 
                 2.78E−11 
                 103 
               
               
                   
                 hErbB3.mFc 
                 5.16E+06 
                 7.46E−06 
                 1.45E−12 
                 1429 
               
               
                 H4H2094P 
                 hErbB3.mmh 
                 1.89E+06 
                 1.37E−05 
                 7.22E−12 
                 780 
               
               
                   
                 hErbB3.mFc 
                 3.03E+06 
                 1.37E−06 
                 4.52E−13 
                 7779 
               
               
                 H4H2098P 
                 hErbB3.mmh 
                 1.14E+06 
                 7.89E−05 
                 6.90E−11 
                 135 
               
               
                   
                 hErbB3.mFc 
                 2.21E+06 
                 8.97E−06 
                 4.06E−12 
                 1188 
               
               
                 H4H2102P 
                 hErbB3.mmh 
                 8.86E+05 
                 4.88E−05 
                 5.51E−11 
                 218 
               
               
                   
                 hErbB3.mFc 
                 1.58E+06 
                 2.26E−06 
                 1.43E−12 
                 4721 
               
               
                 H4H2108P 
                 hErbB3.mmh 
                 1.95E+06 
                 8.13E−05 
                 4.18E−11 
                 131 
               
               
                   
                 hErbB3.mFc 
                 2.96E+06 
                 4.33E−06 
                 1.46E−12 
                 2458 
               
               
                 H4H2111P 
                 hErbB3.mmh 
                 2.21E+06 
                 1.18E−04 
                 5.31E−11 
                 91 
               
               
                   
                 hErbB3.mFc 
                 3.50E+06 
                 8.69E−06 
                 2.49E−12 
                 1225 
               
               
                 H4H2114P 
                 hErbB3.mmh 
                 9.29E+05 
                 9.88E−05 
                 1.06E−10 
                 108 
               
               
                   
                 hErbB3.mFc 
                 1.48E+06 
                 7.98E−06 
                 5.41E−12 
                 1335 
               
               
                 H4H2132P 
                 hErbB3.mmh 
                 2.16E+06 
                 3.81E−05 
                 1.77E−11 
                 279 
               
               
                   
                 hErbB3.mFc 
                 3.49E+06 
                 3.35E−06 
                 9.58E−13 
                 3183 
               
               
                 H4H2138P 
                 hErbB3.mmh 
                 2.39E+06 
                 5.01E−05 
                 2.09E−11 
                 213 
               
               
                   
                 hErbB3.mFc 
                 3.71E+06 
                 5.46E−06 
                 1.47E−12 
                 1952 
               
               
                 H4H2140P 
                 hErbB3.mmh 
                 1.66E+06 
                 3.27E−05 
                 1.98E−11 
                 326 
               
               
                   
                 hErbB3.mFc 
                 2.51E+06 
                 9.86E−07 
                 3.93E−13 
                 10797 
               
               
                 H4H2143P 
                 hErbB3.mmh 
                 1.83E+06 
                 9.73E−05 
                 5.31E−11 
                 109 
               
               
                   
                 hErbB3.mFc 
                 2.86E+06 
                 4.63E−06 
                 1.75E−12 
                 2302 
               
               
                 H4H2146P 
                 hErbB3.mmh 
                 2.79E+06 
                 3.46E−05 
                 1.24E−11 
                 308 
               
               
                   
                 hErbB3.mFc 
                 4.54E+06 
                 1.98E−06 
                 4.35E−13 
                 5392 
               
               
                 H4H2147P 
                 hErbB3.mmh 
                 2.47E+06 
                 1.08E−04 
                 4.38E−11 
                 98 
               
               
                   
                 hErbB3.mFc 
                 3.33E+06 
                 4.58E−06 
                 1.50E−12 
                 2325 
               
               
                 H4H2148P 
                 hErbB3.mmh 
                 3.98E+06 
                 3.47E−05 
                 8.71E−12 
                 307 
               
               
                   
                 hErbB3.mFc 
                 5.91E+06 
                 1.74E−06 
                 2.95E−13 
                 6110 
               
               
                 H4H2151P 
                 hErbB3.mmh 
                 3.04E+06 
                 2.86E−05 
                 9.42E−12 
                 372 
               
               
                   
                 hErbB3.mFc 
                 4.48E+06 
                 9.52E−07 
                 2.13E−13 
                 11186 
               
               
                 H4H2153P 
                 hErbB3.mmh 
                 2.94E+06 
                 3.43E−05 
                 1.17E−11 
                 311 
               
               
                   
                 hErbB3.mFc 
                 3.67E+06 
                 1.24E−06 
                 3.37E−13 
                 8603 
               
               
                 H4H2154P 
                 hErbB3.mmh 
                 2.13E+06 
                 3.73E−05 
                 1.76E−11 
                 285 
               
               
                   
                 hErbB3.mFc 
                 3.25E+06 
                 9.77E−07 
                 3.00E−13 
                 10901 
               
               
                 H4H2290P 
                 hErbB3.mmh 
                 5.82E+05 
                 6.72E−05 
                 1.15E−10 
                 159 
               
               
                   
                 hErbB3.mFc 
                 8.00E+05 
                 1.13E−05 
                 1.40E−11 
                 945 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Biacore Binding Affinities of Select mAbs at 37° C. 
               
               
                 Binding at 37° C./Mab Capture Format 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                 ka 
                 kd 
                 K D   
                   
               
               
                   
                 Analyte 
                 (Ms −1 ) 
                 (s −1 ) 
                 (Molar) 
                 T½ 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 H4H1819N 
                 hErbB3.mmh 
                 1.21E+07 
                 1.56E−03 
                 1.29E−10 
                 7 
               
               
                   
                 hErbB3.mFc 
                 3.68E+07 
                 5.62E−05 
                 1.53E−12 
                 206 
               
               
                 H4H1821N 
                 hErbB3.mmh 
                 6.49E+06 
                 1.08E−03 
                 1.67E−10 
                 11 
               
               
                   
                 hErbB3.mFc 
                 1.87E+07 
                 3.55E−05 
                 1.89E−12 
                 326 
               
               
                 Control I 
                 hErbB3.mmh 
                 1.58E+05 
                 5.48E−04 
                 3.47E−09 
                 21 
               
               
                   
                 hErbB3.mFc 
                 2.60E+05 
                 1.01E−04 
                 3.90E−10 
                 114 
               
               
                 Control II 
                 hErbB3.mmh 
                 3.23E+05 
                 1.34E−03 
                 4.13E−09 
                 9 
               
               
                   
                 hErbB3.mFc 
                 1.44E+06 
                 1.37E−04 
                 9.50E−11 
                 84 
               
               
                 Control III 
                 hErbB3.mmh 
                 3.40E+06 
                 7.90E−02 
                 2.40E−08 
                 0.1 
               
               
                   
                 hErbB3.mFc 
                 1.05E+07 
                 1.77E−04 
                 1.68E−11 
                 65 
               
               
                   
               
            
           
         
       
     
     As shown in Tables 2-4, many of the exemplary antibodies tested in this Example exhibited high affinity binding to ErbB3 that was superior or equivalent to the binding affinities of the control antibodies tested. Of note, several of the anti-ErbB3 antibodies of the present invention exhibited sub-nanomolar affinity to monomeric (hErbB3.mmh) ErbB3 protein. 
     Example 4. Anti-ErbB3 Antibodies Block Neuregulin 1b Binding to Human ErbB3 
     To further characterize anti-hErbB3 mAbs of the present invention, their ability to block ligand binding was examined via ELISA. Plates were coated with neuregulinlb (1 μg/ml) overnight and then antibodies (0-50 nM) were incubated (1 hr, 25° C.) with either 50 pM ErbB3-hFc (SEQ ID NO:498; for hybridomas) or 50 pM ErbB3-mFc (SEQ ID NO:499; for hIgG4 antibodies) and then added to coated plates and allowed to incubate for an additional 1 hr at 25° C. Plates were washed and non-sequestered (plate bound) ErbB3 was detected with an anti-Fc poly conjugated with horseradish peroxidase (HRP). Plates were developed with TMB (3,3′,5,5′-tetramethylbenzidine) and neutralized with sulfuric acid before reading absorbance at 450 nm on a Victor X5 plate reader. Data analysis used a sigmoidal dose-response model within Prism™ software. The calculated IC 50  value, defined as 50% of the antibody concentration required to achieve maximum blocking, was used as an indicator of blocking potency. Maximal blocking for each antibody was calculated by taking the difference in absorbance from zero to 50 nM antibody on the inhibition curve, divided by the difference in absorbance from 50 pM to zero ErbB3 on the dose curve. Results are shown in Tables 5 and 6. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 IC 50  Values for Anti-ErbB3 Hybridoma mAbs (H1M and H2M) 
               
            
           
           
               
               
               
               
            
               
                   
                 Antibody 
                 IC50(M) 
                 Maximal Blocking (%) 
               
               
                   
                   
               
               
                   
                 H1M1819N 
                 3.15E−11 
                 92 
               
               
                   
                 H2M1821N 
                 2.85E−11 
                 96 
               
               
                   
                 H2M1824N 
                 2.51E−11 
                 99 
               
               
                   
                 H2M1827N 
                 2.29E−11 
                 98 
               
               
                   
                 H1M1828N 
                 3.00E−11 
                 95 
               
               
                   
                 H2M1829N 
                 2.38E−11 
                 98 
               
               
                   
                 H2M1930N 
                 2.22E−11 
                 87 
               
               
                   
                 H2M1934N 
                 2.61E−11 
                 80 
               
               
                   
                 H2M1936N 
                 5.27E−10 
                 91 
               
               
                   
                 H2M1937N 
                 4.40E−11 
                 95 
               
               
                   
                 H2M1938N 
                 2.49E−11 
                 85 
               
               
                   
                 H1M1940N 
                 5.30E−10 
                 80 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 IC 50  Values for Anti-ErbB3 Human Fc mAbs (H4H) 
               
            
           
           
               
               
               
               
            
               
                   
                 Antibody 
                 IC50(M) 
                 Maximal Blocking (%) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 H4H1819N 
                 2.00E−11 
                 99 
               
               
                   
                 H4H1821N 
                 1.80E−11 
                 99 
               
               
                   
                 H4H2084P 
                 8.73E−11 
                 95 
               
               
                   
                 H4H2092P 
                 5.94E−11 
                 100 
               
               
                   
                 H4H2094P 
                 9.00E−11 
                 92 
               
               
                   
                 H4H2098P 
                 1.35E−10 
                 95 
               
               
                   
                 H4H2102P 
                 1.86E−10 
                 90 
               
               
                   
                 H4H2108P 
                 1.16E−10 
                 91 
               
               
                   
                 H4H2111P 
                 4.97E−11 
                 92 
               
               
                   
                 H4H2114P 
                 1.63E−10 
                 91 
               
               
                   
                 H4H2132P 
                 9.57E−11 
                 94 
               
               
                   
                 H4H2138P 
                 1.06E−10 
                 96 
               
               
                   
                 H4H2140P 
                 9.46E−11 
                 83 
               
               
                   
                 H4H2143P 
                 8.35E−11 
                 92 
               
               
                   
                 H4H2146P 
                 1.77E−10 
                 83 
               
               
                   
                 H4H2147P 
                 5.06E−11 
                 99 
               
               
                   
                 H4H2148P 
                 5.08E−11 
                 100 
               
               
                   
                 H4H2151P 
                 7.51E−11 
                 85 
               
               
                   
                 H4H2153P 
                 7.40E−11 
                 82 
               
               
                   
                 H4H2154P 
                 9.01E−11 
                 91 
               
               
                   
                 H4H2290P 
                 6.64E−11 
                 99 
               
               
                   
                 Control I 
                 5.74E−10 
                 98 
               
               
                   
                 Control III 
                 8.32E−11 
                 96 
               
               
                   
                   
               
            
           
         
       
     
     As shown in Tables 5 and 6, several anti-ErbB3 antibodies of the present invention showed potent blocking and had IC 50  values that were at the theoretical bottom (25 pM) of the assay. 
     Example 5. Anti-ErbB3 mAbs Effectively Internalize Cell Surface ErbB3 
     To determine if anti-ErbB3 mAbs effectively internalize cell surface bound ErbB3, MCF-7 cells were incubated with select anti-ErbB3 antibody (10 μg/ml) for 30 minutes on ice, washed and then stained with a Dylight 488 conjugated anti-human Fab (10 μg/ml) for 30 minutes on ice. Tubes were then washed and split between an on ice and 37° C. incubation for 1 hour. After incubation all tubes were placed on ice and a Dylight 488 quenching antibody (50 μg/ml) was added. Solutions were incubated an additional 1 hour on ice. Fluorescent signals were measured using an Accuri flow cytometer. 
     As a relative measure of the amount of ErbB3 that was internalized upon antibody binding and subsequent incubation at 37° C., the internalized mean fluorescent intensity (MFI) was calculated as follows: 
       Internalized MFI=Total MFI−Surface MFI
 
       where: 
       Surface MFI=(Total MFI−MFI of Quenched Sample)/QE
 
       and 
       QE=1−[MFI of quenched sample at 4° C./MFI of unquenched sample at 4° C.]
 
     The calculation of QE (quenching efficiency) assumes that no internalization occurs at 4° C. Table 7 shows that all antibodies tested induce HER3 internalization. 
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 Antibody-Induced HER3 Internalization at 37° C. 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Total MFI 
                 Surface MFI 
                 Internalized MFI 
                 % Internalized 
               
               
                 Antibody 
                 mean ± S.D. 
                 mean ± S.D. 
                 mean ± S.D. 
                 mean ± S.D. 
               
               
                   
               
               
                 H4H1819N 
                 39233 ± 9261 
                 22663 ± 5026 
                 16570 ± 5329 
                 42 ± 7  
               
               
                 H4H1821N 
                 32351 ± 5658 
                 11607 ± 4781 
                 20744 ± 4993 
                 64 ± 14 
               
               
                 Control I 
                 19004 ± 5903 
                 11598 ± 6602 
                  7406 ± 1776 
                 42 ± 20 
               
               
                 Control II 
                 41517 ± 5696 
                  23540 ± 11994 
                 17977 ± 6299 
                 45 ± 21 
               
               
                 Control III 
                 27349 ± 5310 
                 8010 ± 729 
                 19338 ± 5934 
                 69 ± 8  
               
               
                   
               
            
           
         
       
     
     Example 6. Inhibition of NRG1-Dependent Akt Phosphorylation by Anti-ErbB3 Antibodies 
     Anti-ErbB3 antibodies were tested for their ability to inhibit phosphorylation of Akt in DU145 prostate cancer cells. Binding of NRG1 to ErbB3 results in ErbB3 phosphorylation, which leads to recruitment and activation of phosphatidylinositol 3-kinase (PI3-K). Activated PI3-K phosphorylates and activates the kinase Akt. Thus, Akt phosphorylation is a downstream marker of ErbB3 receptor activation. DU145 cells were seeded in 96-well plates and then serum-starved in medium containing 1% FBS overnight. Cells were then stimulated with 0.5 nM NRG1 (R&amp;D Systems) for 30 min in the presence of 0.5 μg/ml human Fc control protein or various anti-ErbB3 antibodies at concentrations of 0.01, 0.1 or 0.5 μg/ml. Each concentration of antibody was tested in triplicate. Cells were lysed and the relative levels of phosphorylated Akt were determined using a phospho-Akt cell-based ELISA kit (R&amp;D Systems), according to the manufacturer&#39;s instructions. The average percent inhibition of Akt phosphorylation for each anti-ErbB3 antibody versus the Fc control group is shown in Table 8. 
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 Inhibition of Akt phosphorylation by Anti-ErbB3 Antibodies 
               
            
           
           
               
               
            
               
                   
                 Percent inhibition of Akt phosphorylation 
               
            
           
           
               
               
               
               
            
               
                   
                 0.01 μg/ml ErbB3 
                 0.1 μg/ml ErbB3 
                 0.5 μg/ml ErbB3 
               
               
                 Antibody 
                 antibody 
                 antibody 
                 antibody 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 H1M1819N 
                 29 
                 72 
                 75 
               
               
                 H2M1821N 
                 11 
                 68 
                 73 
               
               
                 H2M1824N 
                 25 
                 63 
                 74 
               
               
                 H2M1827N 
                 16 
                 73 
                 75 
               
               
                 H1M1828N 
                 22 
                 66 
                 75 
               
               
                 H2M1829N 
                 22 
                 74 
                 74 
               
               
                 H2M1930N 
                 39 
                 64 
                 66 
               
               
                 H2M1934N 
                 20 
                 56 
                 67 
               
               
                 H2M1936N 
                 6 
                 30 
                 67 
               
               
                 H2M1937N 
                 −13 
                 41 
                 71 
               
               
                 H2M1938N 
                 40 
                 63 
                 74 
               
               
                 H1M1940N 
                 13 
                 50 
                 68 
               
               
                 Control I 
                 −1 
                 46 
                 60 
               
               
                 Control II 
                 4 
                 7 
                 51 
               
               
                 Control III 
                 3 
                 45 
                 55 
               
               
                   
               
            
           
         
       
     
     This example illustrates that several of the anti-ErbB3 antibodies of the present invention exhibited more potent blockade of Akt phosphorylation than the control anti-ErbB3 antibodies. For example, antibodies H1M1819N, H2M1821N, H2M1824N, H2M1827N, H1M1828N, H2M1829N, H2M1930N and H2M1938N inhibited Akt phosphorylation by at least 60% at the 0.1 μg/ml dose, while none of the control ErbB3 antibodies achieved an inhibition greater than 46% at that dose. 
     Example 7. Inhibition of Tumor Cell Growth by Anti-ErbB3 Antibodies 
     Select anti-ErbB3 antibodies were tested for their ability to inhibit the growth of A431 epidermoid carcinoma cells when used in combination with EGFR blockade. A431 cells in 96-well plates were incubated in medium containing 0.5% FBS and stimulated with 1 nM neuregulin-1 (NRG1) in the presence of an anti-EGFR antibody (1 μg/ml), an anti-ErbB3 antibody (1 μg/ml) or anti-EGFR (1 μg/ml) plus anti-ErbB3 antibody at 0.05, 0.25 or 1.0 μg/ml. The ligand (NRG1) and blocking antibodies (EGFR &amp; ErbB3) were added at 0, 24 and 48 hrs during the 72-hour experiment. The relative change in the number of viable cells from the start of treatment until the 72-hour time point was reached was determined using standard methods (Cell Proliferation Assay Kit; Promega). The average percent decrease in cell growth for each anti-ErbB3 antibody versus an isotype control group is shown in Table 9. 
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 Inhibition of A431 Cell Growth by Anti-ErbB3 Antibodies 
               
            
           
           
               
               
            
               
                   
                 Percent decrease in the growth of A431 cells 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 anti-EGFR 
                 anti-EGFR 
                 anti-EGFR 
               
               
                   
                   
                 antibody + 
                 antibody + 
                 antibody + 
               
               
                   
                 1.0 μg/ml 
                 0.05 μg/ml 
                 0.25 μg/ml 
                 1.0 μg/ml 
               
               
                   
                 ErbB3 
                 ErbB3 
                 ErbB3 
                 ErbB3 
               
               
                 Antibody 
                 antibody 
                 antibody 
                 antibody 
                 antibody 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 H1M1819N 
                 34 
                 61 
                 78 
                 91 
               
               
                 H2M1821N 
                 16 
                 35 
                 62 
                 85 
               
               
                 H2M1824N 
                 33 
                 45 
                 68 
                 85 
               
               
                 H2M1827N 
                 15 
                 53 
                 75 
                 84 
               
               
                 H1M1828N 
                 30 
                 55 
                 73 
                 85 
               
               
                 H2M1829N 
                 31 
                 53 
                 76 
                 89 
               
               
                 H2M1930N 
                 3 
                 23 
                 36 
                 39 
               
               
                 H2M1934N 
                 −3 
                 24 
                 30 
                 28 
               
               
                 H2M1938N 
                 5 
                 37 
                 56 
                 60 
               
               
                 H1M1940N 
                 −4 
                 19 
                 20 
                 19 
               
               
                 Control I 
                 19 
                 31 
                 37 
                 56 
               
               
                 Control III 
                 7 
                 22 
                 21 
                 32 
               
               
                   
               
            
           
         
       
     
     This example illustrates that several of the anti-ErbB3 antibodies of the present invention exhibited more potent inhibition of A431 cell growth than the control anti-ErbB3 antibodies. For example, antibodies H1M1819N, H2M1821N, H2M1824N, H2M1827N, H1M1828N and H2M1829N inhibited cell growth by at least 60% at the 0.25 μg/ml dose when combined with anti-EGFR antibody, while control antibodies I and III inhibited cell growth by only 37% and 21%, respectively, under these experimental conditions. 
     Example 8. Inhibition of ErbB3 and Akt Phosphorylation by Anti-ErbB3 Antibodies 
     Select anti-ErbB3 antibodies were tested for their ability to inhibit NRG1-stimulated phosphorylation of ErbB3 and Akt in A431 epidermoid carcinoma and MCF7 breast cancer cells. In the first experiment, A431 cells were seeded in 6-well plates and incubated in complete medium overnight. Cells were then serum-starved (0.5% FBS) for 1 hr and stimulated with 1 nM NRG1 (R&amp;D Systems) for 30 min in the presence of 5.0 μg/ml of isotype control or anti-ErbB3 antibody at 0.05, 0.25 or 5.0 μg/ml. Cells were lysed and Western blots were performed using antibodies against ErbB3 and Akt as well as their phosphorylated forms using standard methods. The ratios of phosphorylated ErbB3 or Akt to total ErbB3 or Akt were calculated and used to determine the percent inhibition of Akt or ErbB3 phosphorylation for each of the anti-ErbB3 antibodies relative to isotype control. Results for the inhibition of ErbB3 or AKT phosphorylation in A431 cells are shown in Tables 10 and 11, respectively. 
     
       
         
           
               
             
               
                 TABLE 10 
               
             
            
               
                   
               
               
                 Percent Inhibition of ErbB3 Phosphorylation in A431 Cells 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Antibody 
                 0.05 μg/ml 
                 0.25 μg/ml 
                 5.0 μg/ml 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 H4H1819N 
                 98 
                 105 
                 107 
               
               
                   
                 H4H1821N 
                 63 
                 113 
                 120 
               
               
                   
                 Control I 
                 −11 
                 14 
                 72 
               
               
                   
                 Control III 
                 −30 
                 −9 
                 −57 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 11 
               
             
            
               
                   
               
               
                 Percent Inhibition of Akt Phosphorylation in A431 Cells 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Antibody 
                 0.05 μg/ml 
                 0.25 μg/ml 
                 5.0 μg/ml 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 H4H1819N 
                 84 
                 104 
                 113 
               
               
                   
                 H4H1821N 
                 67 
                 106 
                 117 
               
               
                   
                 Control I 
                 32 
                 47 
                 75 
               
               
                   
                 Control III 
                 43 
                 51 
                 58 
               
               
                   
                   
               
            
           
         
       
     
     In a similar experiment, MCF7 cells were seeded in 6-well plates and incubated in complete medium for 2 days. Cells were then serum-starved (0.5% FBS) for 1 hr and then stimulated with 1 nM NRG1 (R&amp;D Systems) for 30 min in the presence of 5.0 μg/ml of isotype control or anti-ErbB3 antibody at of 0.05, 0.25, 1.0 or 5.0 μg/ml. Western blots and data analysis were carried out in a similar manner for those experiments conducted with A431 cells. Results for the inhibition of ErbB3 or AKT phosphorylation in MCF7 cells are shown in Tables 12 and 13, respectively. 
     
       
         
           
               
             
               
                 TABLE 12 
               
             
            
               
                   
               
               
                 Percent Inhibition of ErbB3 Phosphorylation in MCF7 Cells 
               
            
           
           
               
               
               
               
               
            
               
                 Antibody 
                 0.05 μg/ml 
                 0.25 μg/ml 
                 1.0 μg/ml 
                 5.0 μg/ml 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 H4H1819N 
                 37 
                 79 
                 92 
                 96 
               
               
                 H4H1821N 
                 57 
                 92 
                 96 
                 97 
               
               
                 Control I 
                 0 
                 17 
                 44 
                 81 
               
               
                 Control III 
                 4 
                 12 
                 60 
                 61 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 13 
               
             
            
               
                   
               
               
                 Percent Inhibition of Akt Phosphorylation in MCF7 Cells 
               
            
           
           
               
               
               
               
               
            
               
                 Antibody 
                 0.05 μg/ml 
                 0.25 μg/ml 
                 1.0 μg/ml 
                 5.0 μg/ml 
               
               
                   
               
               
                 H4H1819N 
                 13 
                 36 
                 80 
                 90 
               
               
                 H4H1821N 
                 17 
                 69 
                 82 
                 89 
               
               
                 Control I 
                 21 
                 29 
                 34 
                 46 
               
               
                 Control III 
                 35 
                 28 
                 29 
                 35 
               
               
                   
               
            
           
         
       
     
     This Example illustrates that representative anti-ErbB3 antibodies of the invention exhibited superior ability to inhibit phosphorylation of ErbB3 and Akt compared to control antibodies under most of the experimental conditions tested. In A431 cells, for example, H4H1819N and H4H1821N completely inhibited both ErbB3 and Akt phosphorylation at 0.25 μg/ml while the control antibodies never achieved complete inhibition, even at 5.0 μg/ml. Similarly, in MCF7 cells, H4H1819N and H4H1821N at 1.0 μg/ml inhibited ErbB3 and Akt phosphorylation to a greater extent than either of the control anti-ErbB3 antibodies even at 5.0 μg/ml. 
     Example 9. Inhibition of Tumor Growth by Anti-ErbB3 Antibodies 
     Select anti-ErbB3 antibodies were tested for their ability to inhibit the growth of human tumor xenografts in immunocompromised mice. Briefly, 1-5×10 6  A431 human epidermoid carcinoma cells or A549 human non-small cell lung cancer cells (ATCC) were implanted subcutaneously into the flank of 6-8 week old SCID mice (Taconic, Hudson, N.Y.). After tumors reached an average volume of 100-150 mm 3 , mice were randomized into groups for treatment (n=6 mice per group). In the first experiment, mice bearing A431 tumors were administered human Fc (SEQ ID NO:500, 12.5 mg/kg), or anti-ErbB3 antibody (0.5 or 12.5 mg/kg). All antibodies were administered via subcutaneous injection twice per week for approximately 3 weeks. Tumor volumes were measured twice per week over the course of the experiment and tumor weights were determined upon excision of tumors at the conclusion of the experiment. Average tumor size relative to the Fc treated group as well as final tumor weights were calculated for each group. Results are summarized in Table 14. 
     
       
         
           
               
             
               
                 TABLE 14 
               
             
            
               
                   
               
               
                 Inhibition of A431 Tumor Growth in SCID 
               
               
                 Mice (Hybridoma mAbs - H1M and H2M) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Tumor Growth in 
                   
                   
                   
               
               
                   
                 mm 3  from 
                 Average % 
                 Avg 
                 Average % 
               
               
                   
                 Start of Treatment 
                 Decrease in 
                 Tumor Weight 
                 Decrease in 
               
               
                 Antibody (mg/kg) 
                 (mean ± S.D.) 
                 Tumor Growth 
                 (g) 
                 Tumor Weight 
               
               
                   
               
               
                 hFc Ctrl (12.5) 
                 860 ± 358 
                 — 
                 0.778 ± 0.268 
                 — 
               
               
                 H1M1819N (0.5) 
                 355 ± 178 
                 59 
                 0.520 ± 0.155 
                 33 
               
               
                 H2M1821N (0.5) 
                 280 ± 131 
                 67 
                 0.428 ± 0.209 
                 45 
               
               
                 H2M1827N (0.5) 
                 246 ± 71  
                 71 
                 0.432 ± 0.152 
                 45 
               
               
                 H2M1829N (0.5) 
                 392 ± 265 
                 54 
                 0.480 ± 0.283 
                 38 
               
               
                 Control I (0.5) 
                 862 ± 199 
                 0 
                 0.815 ± 0.190 
                 −5 
               
               
                 Control I (12.5) 
                 299 ± 139 
                 65 
                 0.438 ± 0.217 
                 44 
               
               
                   
               
            
           
         
       
     
     In a similar experiment, using selected antibodies in the human IgG4 format yield similar results, as summarized in Table 15. 
     
       
         
           
               
             
               
                 TABLE 15 
               
             
            
               
                   
               
               
                 Inhibition of A431 Tumor Growth in SCID Mice (Human Fc mAbs - H4H) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Tumor Growth in 
                   
                   
                   
               
               
                   
                 mm 3  from 
                 Average % 
                 Avg 
                 Average % 
               
               
                   
                 Start of Treatment 
                 Decrease in 
                 Tumor Weight 
                 Decrease in 
               
               
                 Antibody (mg/kg) 
                 (mean ± S.D.) 
                 Tumor Growth 
                 (g) 
                 Tumor Weight 
               
               
                   
               
               
                 hFc ctrl (12.5) 
                 797 ± 65  
                 — 
                  1.31 ± 0.142 
                 — 
               
               
                 H4H1819N (0.5) 
                 161 ± 69  
                 80 
                 0.453 ± 0.010 
                 65 
               
               
                 H4H1819N (12.5) 
                 110 ± 47  
                 86 
                 0.458 ± 0.108 
                 65 
               
               
                 H4H1821N (0.5) 
                 148 ± 73  
                 81 
                 0.482 ± 0.058 
                 63 
               
               
                 H4H1821N (12.5) 
                  74 ± 100 
                 91 
                 0.392 ± 0.117 
                 70 
               
               
                 Control I (0.5) 
                 675 ± 228 
                 15 
                 0.928 ± 0.215 
                 29 
               
               
                 Control I (12.5) 
                 95 ± 51 
                 88 
                 0.361 ± 0.063 
                 72 
               
               
                 Control III (0.5) 
                 409 ± 254 
                 49 
                 0.687 ± 0.269 
                 48 
               
               
                 Control III (12.5) 
                 219 ± 129 
                 73 
                 0.545 ± 0.096 
                 58 
               
               
                   
               
            
           
         
       
     
     In similar experiments, the effect of various anti-ErbB3 antibodies on the growth of A549 tumor xenografts was determined, as summarized in Table 16. 
     
       
         
           
               
             
               
                 TABLE 16 
               
             
            
               
                   
               
               
                 Inhibition of A549 Tumor Growth in SCID Mice 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Tumor Growth in 
                   
                   
                   
               
               
                   
                 mm 3  from 
                 Average % 
                 Avg 
                 Average % 
               
               
                   
                 Start of Treatment 
                 Decrease in 
                 Tumor Weight 
                 Decrease in 
               
               
                 Antibody (mg/kg) 
                 (mean ± S.D.) 
                 Tumor Growth 
                 (g) 
                 Tumor Weight 
               
               
                   
               
               
                 hFc ctrl (12.5) 
                 727 ± 184 
                 — 
                  1.27 ± 0.332 
                 — 
               
               
                 H4H1821N (0.2) 
                 366 ± 90  
                 50 
                 0.811 ± 0.145 
                 37 
               
               
                 H4H1821N (0.5) 
                 347 ± 52  
                 52 
                 0.820 ± 0.245 
                 36 
               
               
                 H4H1821N (2.5) 
                 346 ± 106 
                 52 
                 0.783 ± 0.175 
                 39 
               
               
                 Control I (0.5) 
                 719 ± 230 
                 1 
                 1.328 ± 0.363 
                 −3.78 
               
               
                 Control I (2.5) 
                 614 ± 177 
                 15 
                 0.985 ± 0.198 
                 23 
               
               
                   
               
            
           
         
       
     
     As shown in this Example, antibodies H4H1819N and H4H1821N each significantly inhibited tumor growth in vivo to an extent that was superior, or equivalent to the extent of tumor growth inhibition observed with administration of the control anti-ErbB3 antibodies tested. 
     Example 10. Inhibition of Tumor Growth by Anti-ErbB3 Antibodies in Combination with Agents that Block Other ErbB Family Members 
     The effect of a combination treatment with H4H1821N plus an inhibitory anti-EGFR antibody (“anti-EGFR mAb”) on human tumor xenograft growth was tested. Briefly, 2×10 6  FaDu human hypopharyngeal carcinoma cells (ATCC) were implanted subcutaneously into the flank of 6-8 week old SCID mice (Taconic, Hudson, N.Y.). After tumors reached an average volume of 150-200 mm 3 , mice were randomized into groups for treatment (n=6 mice per group). Mice were administered human Fc control protein (12.5 mg/kg), H4H1821N (2.5 mg/kg), anti-EGFR mAb (10 mg/kg) or the combination of H4H1821N plus anti-EGFR mAb (2.5+10 mg/kg). All antibodies were administered via subcutaneous injection twice per week. Tumor volumes were measured twice per week over the course of the experiment and tumor weights were determined upon excision of tumors at the conclusion of the experiment. Averages (mean+/−standard deviation) of the tumor growth from the start of treatment and the tumor weights were calculated for each treatment group. The percent decrease of tumor growth and tumor weight was calculated from comparison to the Fc control group. The results are shown in Table 17. 
     
       
         
           
               
             
               
                 TABLE 17 
               
             
            
               
                   
               
               
                 Inhibition of FaDu tumor xenograft growth in SCID mice 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Tumor Growth in 
                   
                   
                   
               
               
                   
                 mm 3  from 
                 Average % 
                 Average 
                 Average % 
               
               
                   
                 Start of Treatment 
                 Decrease in 
                 Tumor Weight 
                 Decrease in 
               
               
                 Antibody (mg/kg) 
                 (mean ± S.D.) 
                 Tumor Growth 
                 (g) 
                 Tumor Weight 
               
               
                   
               
               
                 hFc control (12.5) 
                 1099 ± 186 
                 — 
                 0.993 ± 0.176 
                 — 
               
               
                 H4H1821N (2.5) 
                  284 ± 175 
                 74 
                 0.522 ± 0.177 
                 47 
               
               
                 anti-EGFR mAb (10) 
                  55 ± 115 
                 95 
                 0.215 ± 0.120 
                 78 
               
               
                 H4H1821N + anti-EGFR 
                 −199 ± 38  
                 118 
                 0.024 ± 0.020 
                 98 
               
               
                 mAb (2.5 + 10) 
               
               
                   
               
            
           
         
       
     
     In a similar experiment, the effect of a combination treatment with H4H1821N plus the inhibitory anti-HER2 antibody clone 4D5v8 as described in Carter el al.,  Proc. Natl. Acad. Sci. USA  89:4285-4289 (1992) on human tumor xenograft growth was tested. Briefly, 1×10 7  BT474 human breast cancer cells (ATCC) were implanted subcutaneously into the flank of 6-8 week old NCR nude mice (Taconic, Hudson, N.Y.). After tumors reached an average volume of 150-200 mm 3 , mice were randomized into groups for treatment (n=5 mice per group). Mice were administered human Fc control protein (25 mg/kg), H4H1821N (12.5 mg/kg), 4D5v8 (12.5 mg/kg) or the combination of H4H1821N plus 4D5v8 (12.5+12.5 mg/kg). All antibodies were administered via subcutaneous injection twice per week. Tumor volumes were measured twice per week over the course of the experiment. The average (mean+/−standard deviation) tumor growth from the start of treatment was calculated for each treatment group. The percent decrease of tumor growth was calculated from comparison to the Fc control group. The results are shown in Table 18. 
     
       
         
           
               
             
               
                 TABLE 18 
               
             
            
               
                   
               
               
                 Inhibition of BT474 tumor xenograft growth in nude mice 
               
            
           
           
               
               
               
            
               
                   
                 Tumor growth in mm3 
                   
               
               
                   
                 from start of treatment 
                 Average % Decrease 
               
               
                 Antibody (mg/kg) 
                 (mean ± SD) 
                 in Tumor Growth 
               
               
                   
               
               
                 hFc control (25) 
                 194 ± 39 
                 — 
               
               
                 H4H1821N (12.5) 
                 137 ± 65 
                 29 
               
               
                 4D5v8 (12.5) 
                  34 ± 121 
                 82 
               
               
                 H4H1821N + 4D5v8 
                 −79 ± 39 
                 141 
               
               
                 (12.5 + 12.5) 
               
               
                   
               
            
           
         
       
     
     This example illustrates that combined treatment with H4H1821N plus anti-EGFR or anti-HER2 antibodies provides more potent inhibition of tumor growth than the single agent treatments. In both FaDu and BT474 tumor xenografts, the combination treatments, but not the single agents, caused the average tumor size to decrease (tumor regression). 
     Example 11. Epitope Mapping of H4H1821N Binding to ErbB3 by H/D Exchange 
     Experiments were conducted to determine the amino acid residues of ErbB3 with which H4H1821N interacts. For this purpose H/D exchange epitope mapping was carried out. A general description of the H/D exchange method is set forth in e.g., Ehring (1999)  Analytical Biochemistry  267(2):252-259; and Engen and Smith (2001)  Anal. Chem.  73:256A-265A. 
     To map the binding epitope(s) of antibody H4H1821N on ErbB3 via H/D exchange, a recombinant construct consisting of the extracellular domain of hErbB3 (amino acids 1-613 of SEQ ID NO:498) with a C-terminal myc-myc-hexahistidine tag (“hErbB3-mmH”) was used. hErbB3-mmH was first deglycosylated with PNGase F (New England BioLabs) under native conditions. Antibody H4H1821N was covalently attached to N-hydroxysuccinimide (NHS) agarose beads (GE Lifescience). 
     In the ‘on-solution/off-beads’ experiment (on-exchange in solution followed by off-exchange on beads), the ligand (deglycosyated hErbB3-mmH) was deuterated for 5 min or 10 min in PBS buffer prepared with D 2 O, and then bound to H4H1821N beads through a 2 min incubation. The ErbB3-bound beads were washed with PBS aqueous buffer (prepared with H 2 O) and incubated for half of the on-exchange time in PBS buffer. After the off-exchange, the bound ErbB3 was eluted from beads with an ice-cold low pH TFA solution. The eluted ErbB3 was then digested with immobilized pepsin (Thermo Scientific) for 5 min. The resulting peptides were desalted using ZipTip® chromatographic pipette tips and immediately analyzed by UltrafleXtreme matrix assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry (MS). 
     In the ‘on-beads/off-beads’ experiment (on-exchange on beads followed by off-exchange on beads), ErbB3 was first bound to H4H1821N beads and then incubated for 5 min or 10 min in D 2 O for on-exchange. The following steps (off-exchange, pepsin digestion, and MS analysis) were carried out as described for the ‘on-solution/off-beads’ procedure. The centroid values or average mass-to-charge ratios (m/z) of all the detected peptides were calculated and compared between these two sets of experiments. 
     The results are summarized in Table 19 which provides a comparison of the centroid m/z values for all the detected peptides identified by liquid chromatography-matrix assisted laser desorption ionization (LC-MALDI) MS following the H/D exchange and peptic digest procedure. While the majority of the observed peptic peptides gave similar centroid values for both the on-solution/off-beads and on-beads/off-beads experiments, three segments corresponding to residues 345-367, 423-439, and 451-463 of the extracellular domain of ErbB3 (SEQ ID NO:498) had delta centroid values (Δ) greater than or equal to 0.20 m/z in both the ‘5 min on-/2.5 min off-exchange’ experiment (Experiment I) and the ‘10 min on-/5 min off-exchange’ experiment (Experiment II). For purposes of the present Example, a positive difference (Δ) of at least 0.20 m/z in both experiments indicates amino acids protected by antibody binding. Segments meeting this criterion are indicated by bold text and an asterisk (*) in Table 19. 
     
       
         
           
               
             
               
                 TABLE 19 
               
             
            
               
                   
               
               
                 H4H1821N Binding to hErbB3-mmH 
               
            
           
           
               
               
               
            
               
                   
                 Experiment I 
                 Experiment II 
               
               
                 Residues 
                 5 min on-/2.5 min off-exchange 
                 10 min on-/5 min off-exchange 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 (of SEQ ID 
                 On-solution/ 
                 On-Beads/ 
                   
                 On-solution/ 
                 On-Beads/ 
                   
               
               
                 NO:498) 
                 Off Beads 
                 Off-Beads 
                 Δ 
                 Off Beads 
                 Off-Beads 
                 Δ 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 46-57 
                 1287.52 
                 1287.41 
                 0.11 
                 1287.58 
                 1287.64 
                 −0.06 
               
               
                 58-63 
                 844.97 
                 844.97 
                 0.00 
                 845.04 
                 844.99 
                 0.06 
               
               
                 58-66 
                 1102.34 
                 1102.25 
                 0.09 
                 1102.25 
                 1102.30 
                 −0.05 
               
               
                 58-67 
                 1265.65 
                 1265.60 
                 0.05 
                 1265.57 
                 1265.50 
                 0.07 
               
               
                 58-69 
                 1477.84 
                 1477.77 
                 0.07 
                 1477.79 
                 1477.79 
                 0.01 
               
               
                 59-69 
                 1364.46 
                 1364.48 
                 −0.02 
                 1364.39 
                 1364.42 
                 −0.03 
               
               
                 61-69 
                 1050.70 
                 1050.67 
                 0.03 
                 1050.75 
                 1050.68 
                 0.07 
               
               
                 75-96 
                 2509.35 
                 2509.27 
                 0.08 
                 2509.21 
                 2509.21 
                 0.01 
               
               
                 76-96 
                 2362.11 
                 2362.09 
                 0.01 
                 2362.11 
                 2361.97 
                 0.14 
               
               
                 84-96 
                 1526.22 
                 1526.05 
                 0.16 
                 1526.09 
                 1526.08 
                 0.01 
               
               
                 84-98 
                 1710.14 
                 1710.11 
                 0.03 
                 1710.17 
                 1710.07 
                 0.11 
               
               
                 84-99 
                 1857.37 
                 1857.34 
                 0.03 
                 1857.39 
                 1857.33 
                 0.06 
               
               
                 86-96 
                 1270.52 
                 1270.50 
                 0.02 
                 1270.50 
                 1270.45 
                 0.05 
               
               
                 100-114 
                 1750.75 
                 1750.60 
                 0.15 
                 1750.85 
                 1750.75 
                 0.11 
               
               
                 100-114 
                 1766.52 
                 1766.55 
                 −0.03 
                 1766.63 
                 1766.47 
                 0.16 
               
               
                 100-120 
                 2476.03 
                 2475.80 
                 0.23 
                 2476.04 
                 2475.96 
                 0.08 
               
               
                 103-117 
                 1789.63 
                 1789.48 
                 0.14 
                 1789.69 
                 1789.44 
                 0.24 
               
               
                 112-120 
                 1142.00 
                 1141.95 
                 0.05 
                 1142.01 
                 1142.06 
                 −0.05 
               
               
                 144-154 
                 1431.72 
                 1431.72 
                 0.00 
                 1431.76 
                 1431.67 
                 0.08 
               
               
                 345-365 
                 2328.64 
                 2328.64 
                 0.00 
                 2328.57 
                 2328.64 
                 −0.07 
               
               
                   345-367*   
                 2542.60 
                 2542.34 
                 
                   0.26 
                 
                 2542.67 
                 2542.47 
                 
                   0.20 
                 
               
               
                 366-378 
                 1568.81 
                 1568.70 
                 0.11 
                 1568.88 
                 1568.78 
                 0.10 
               
               
                 368-373 
                 807.97 
                 807.95 
                 0.02 
                 807.94 
                 807.88 
                 0.06 
               
               
                 368-376 
                 1079.25 
                 1079.30 
                 −0.04 
                 1079.38 
                 1079.30 
                 0.08 
               
               
                 368-377 
                 1242.49 
                 1242.40 
                 0.09 
                 1242.48 
                 1242.43 
                 0.05 
               
               
                 368-378 
                 1355.82 
                 1355.68 
                 0.14 
                 1355.70 
                 1355.73 
                 −0.03 
               
               
                 368-379 
                 1469.55 
                 1469.56 
                 −0.01 
                 1469.63 
                 1469.57 
                 0.06 
               
               
                 368-380 
                 1583.09 
                 1583.10 
                 −0.01 
                 1583.04 
                 1583.03 
                 0.01 
               
               
                 369-378 
                 1208.29 
                 1208.25 
                 0.03 
                 1208.33 
                 1208.30 
                 0.03 
               
               
                 397-408 
                 1295.45 
                 1295.47 
                 −0.01 
                 1295.41 
                 1295.36 
                 0.05 
               
               
                 397-411 
                 1643.12 
                 1643.04 
                 0.08 
                 1643.03 
                 1642.98 
                 0.05 
               
               
                 397-412 
                 1756.26 
                 1756.08 
                 0.18 
                 1756.18 
                 1756.04 
                 0.14 
               
               
                 405-411 
                 857.06 
                 856.97 
                 0.09 
                 857.09 
                 857.02 
                 0.07 
               
               
                 423-435 
                 1434.94 
                 1434.82 
                 0.11 
                 1434.96 
                 1434.78 
                 0.18 
               
               
                 
                    423-436* 
                 
                 1598.08 
                 1597.89 
                 
                   0.20 
                 
                 1598.27 
                 1598.06 
                 
                   0.21 
                 
               
               
                 
                    424-439* 
                 
                 1812.55 
                 1812.27 
                 
                   0.28 
                 
                 1812.76 
                 1812.37 
                 
                   0.39 
                 
               
               
                 
                    423-439* 
                 
                 1869.57 
                 1869.29 
                 
                   0.28 
                 
                 1869.79 
                 1869.41 
                 
                   0.38 
                 
               
               
                 424-435 
                 1377.85 
                 1377.69 
                 0.16 
                 1378.16 
                 1377.93 
                 0.22 
               
               
                 
                    424-436* 
                 
                 1541.12 
                 1540.90 
                 
                   0.21 
                 
                 1541.20 
                 1541.00 
                 
                   0.20 
                 
               
               
                 
                    425-439* 
                 
                 1665.29 
                 1665.04 
                 
                   0.26 
                 
                 1665.55 
                 1665.22 
                 
                   0.33 
                 
               
               
                 
                    451-463* 
                 
                 1585.74 
                 1585.51 
                 
                   0.23 
                 
                 1585.77 
                 1585.53 
                 
                   0.24 
                 
               
               
                 618-641 
                 2828.04 
                 2827.98 
                 0.06 
                 2827.98 
                 2827.89 
                 0.10 
               
               
                 621-629 
                 989.16 
                 989.14 
                 0.02 
                 989.27 
                 989.28 
                 −0.01 
               
               
                 621-641 
                 2498.60 
                 2498.59 
                 0.01 
                 2498.65 
                 2498.53 
                 0.12 
               
               
                   
               
            
           
         
       
     
     The H/D exchange results summarized in Table 19 indicate that the three regions corresponding to amino acids 345-367, 423-439, and 451-463 of SEQ ID NO:498 are protected from full off-exchange by H4H1821N binding to ErbB3 after on-exchange. Significantly, all three regions are located within domain III of the ErbB3 extracellular domain. Therefore, this Example suggests that antibody H4H1821N binds a discontinuous epitope within domain III of the human ErbB3 extracellular domain consisting of these three amino acid segments or otherwise results in protection of these residues from H/D exchange (e.g., via conformational change or allosteric effects upon antibody binding). 
     Example 12. Clinical Trial of an Anti-ErbB3 Antibody in Combination with Erlotinib or Cetuximab in Patients with Advanced Colorectal Cancer (CRC), Non-Small Cell Lung Cancer (NSCLC) or Head and Neck Cancer (SCCHN) 
     A clinical trial is conducted with the exemplary anti-ErbB3 antibody H4H1821N in patients with advanced colorectal cancer (CRC), non-small cell lung cancer (NSCLC) or head and neck cancer (SCCHN). The trial is divided into two phases: a dose escalation phase and a safety expansion phase. In the dose escalation phase, all patients are initially administered H4H1821N intravenously (IV) at a dose of 3, 10 or 20 mg/kg. Following the initial dose of H4H1821N, the treatment regimen is modified based on cancer type: NSCLC patients begin a regimen of 150 mg Erlotinib once daily in combination with H4H1821N at 3, 10 or 20 mg/kg IV, once every 14 days; CRC and SCCHN patients begin a regimen of Cetuximab 250 mg/m 2  IV once a week in combination with H4H1821N at 3, 10 or 20 mg/kg IV, once every 14 days. In the safety expansion phase, NSCLC patients receive H4H1821N (at the recommended Phase 2 dose) IV once every 14 days in combination with 150 mg Erlotinib once daily; CRC and SCCHN patients receive H4H1821N (at the recommended Phase 2 dose) IV once every 14 days in combination with Cetuximab 250 mg/m 2  IV once a week. 
     It is expected that combination therapy comprising the anti-ErbB3 antibody H4H1821N and Erlotinib or Cetuximab will provide observable clinical improvements in patients with NSCLC, CRC and/or SCCHN to a greater extent than monotreatment with Erlotinib or Cetuximab alone. 
     The present invention is not to be limited in scope by the specific embodiments describe herein. Indeed, various modifications of the invention in addition to those described herein will become apparent to those skilled in the art from the foregoing description and the accompanying figures. Such modifications are intended to fall within the scope of the appended claims.