Anti-HER3 antibodies and anti-MET antibodies and their use

Abstract

This disclosure relates to anti-HER3 (human epidermal growth factor receptor 3) and anti-MET antibodies, as well as their associated antigen-binding fragments, antibody-drug conjugates (ADCs) derived therefrom, and their uses.

Description

[Technical Field]

[0001] Claim of priority This application claims priority to PCT / CN2023 / 082295 filed on 17 March 2023, PCT / CN2023 / 083790 filed on 24 March 2023, PCT / CN2023 / 125481 filed on 19 October 2023, and PCT / CN2024 / 075481 filed on 2 February 2024. The entirety of the aforementioned applications is incorporated herein by reference.

[0002] Technical field This disclosure relates to antibodies, their antigen-binding fragments, antibody-drug conjugates (ADCs) derived therefrom, and their uses. [Background technology]

[0003] ERBB family members are abnormally activated in multiple cancers, making them useful drug targets and biomarkers in modern precision medicine. HER3 has recently attracted attention as an important heterodimer partner for other EGFR family members and for its potential to control EGFR / HER2-mediated resistance. HER3 upregulation is associated with several malignancies and promotes tumor progression through interactions with various receptor tyrosine kinases (RTKs).

[0004] MET, also known as tyrosine protein kinase MET or hepatocyte growth factor receptor (HGFR), is a protein encoded by the MET gene in humans. The MET pathway plays a crucial role in cancer development through the activation of major tumorigenic pathways (RAS, PI3K, STAT3, β-catenin), angiogenesis (the growth of new blood vessels from existing blood vessels to supply nutrients to the tumor), and scatter (cell dissociation due to the production of metalloproteinases).

[0005] Given the important roles of HER3 and MET in tumors, there is a need for the development of therapeutic agents that target HER3 and / or MET. [Overview of the Initiative]

[0006] This disclosure relates to an anti-HER3 antibody, its antigen-binding fragment, and its use.

[0007] In one embodiment, the present disclosure relates to an antibody or antigen-binding fragment thereof that binds to HER3 (human epidermal growth factor receptor 3), A heavy chain variable region (VH) comprising complementarity-determining regions (CDRs) 1, 2, and 3, wherein the VH CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH CDR1, the VH CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH CDR2, and the VH CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH CDR3, and A light chain variable region (VL) comprising CDR1, 2, and 3, wherein the VL CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL CDR1, the VL CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL CDR2, and the VL CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL CDR3. The amino acid sequences of the above-selected VH CDR1, 2, and 3, and the amino acid sequences of the above-selected VL CDR1, 2, and 3, relate to an antibody or its antigen-binding fragment, which is one of the following. (1) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs. 4 to 6, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (2) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs. 7 to 9, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (3) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs. 10 to 12, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (4) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs. 13 to 15, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (5) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs. 16-18, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs. 1-3, respectively. (6) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs. 22-24, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (7) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs. 25-27, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (8) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs. 28-30, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (9) The amino acid sequences of the above-selected VH CDR1, 2, and 3 are shown in SEQ ID NOs. 31-33, respectively, and the amino acid sequences of the above-selected VL CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively, and (10) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs. 34-36, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively.

[0008] In some embodiments, based on Kabat's definition, the VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 4 to 6, respectively, and the VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 1 to 3, respectively.

[0009] In some embodiments, based on Kabat's definition, the VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 7 to 9, respectively, and the VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 1 to 3, respectively.

[0010] In some embodiments, based on Kabat's definition, the VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 10 to 12, respectively, and the VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 1 to 3, respectively.

[0011] In some embodiments, based on Kabat's definition, the VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 13 to 15, respectively, and the VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 1 to 3, respectively.

[0012] In some embodiments, based on Kabat's definition, the VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 16-18, respectively, and the VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 1-3, respectively.

[0013] In some embodiments, based on Chothia's definition, the VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 22 to 24, respectively, and the VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 19 to 21, respectively.

[0014] In some embodiments, based on Chothia's definition, VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 25 to 27, respectively, and VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 19 to 21, respectively.

[0015] In some embodiments, based on the definition of Chothia, the above VH includes CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 28 to 30, respectively, and the above VL includes CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 19 to 21, respectively.

[0016] In some embodiments, based on Chothia's definition, the above VH includes CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 31 to 33, respectively, and the above VL includes CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 19 to 21, respectively.

[0017] In some embodiments, based on the definition of Chothia, the above VH includes CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 34 to 36, respectively, and the above VL includes CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 19 to 21, respectively.

[0018] In some embodiments, the antibody or its antigen-binding fragment specifically binds to human HER3, mouse HER3, monkey HER3, or canine HER3.

[0019] In some embodiments, the antibody or its antigen-binding fragment is a human antibody or its antigen-binding fragment, a single-chain variable fragment (scFv), a single-arm antibody, and / or a multispecific antibody (e.g., a bispecific antibody).

[0020] In some embodiments, the antibody or its antigen-binding fragment is a human IgG1 antibody or its antigen-binding fragment, a human IgG2 antibody or its antigen-binding fragment, or a human IgG4 antibody or its antigen-binding fragment.

[0021] In one embodiment, the present disclosure relates to an antibody or antigen-binding fragment thereof that binds to HER3, comprising a heavy chain variable region (VH) comprising an amino acid sequence that is at least 90% identical to a selected VH sequence, and a light chain variable region (VL) comprising an amino acid sequence that is at least 90% identical to a selected VL sequence, wherein the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, and the selected VL sequence is sequence number 37, (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

[0022] In some embodiments, VH includes the sequence of sequence number 38, and VL includes the sequence of sequence number 37.

[0023] In some embodiments, VH includes the sequence of sequence number 39, and VL includes the sequence of sequence number 37.

[0024] In some embodiments, VH includes the sequence of sequence number 40, and VL includes the sequence of sequence number 37.

[0025] In some embodiments, VH includes the sequence of sequence number 41, and VL includes the sequence of sequence number 37.

[0026] In some embodiments, VH includes the sequence of sequence number 42, and VL includes the sequence of sequence number 37.

[0027] In one embodiment, the present disclosure relates to an antibody or antigen-binding fragment thereof that binds to HER3, comprising a heavy chain variable region (VH) containing VH CDR1, VH CDR2, and VH CDR3 which are identical to VH CDR1, VH CDR2, and VH CDR3 of a selected VH sequence, and a light chain variable region (VL) containing VL CDR1, VL CDR2, and VL CDR3 which are identical to VL CDR1, VL CDR2, and VL CDR3 of a selected VL sequence, wherein the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, and the selected VL sequence is sequence number 37, (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

[0028] In some embodiments, the antibody or its antigen-binding fragment specifically binds to human HER3, mouse HER3, monkey HER3, or canine HER3.

[0029] In some embodiments, the antibody or its antigen-binding fragment is a human antibody or its antigen-binding fragment, a single-chain variable fragment (scFv), a single-arm antibody, and / or a multispecific antibody (e.g., a bispecific antibody).

[0030] In some embodiments, the antibody or antigen-binding fragment is a human IgG1 antibody or its antigen-binding fragment, a human IgG2 antibody or its antigen-binding fragment, or a human IgG4 antibody or its antigen-binding fragment.

[0031] In one embodiment, the present disclosure relates to an antibody or antigen-binding fragment thereof, comprising a first antigen-binding domain that specifically binds to a first epitope of HER3, and a second antigen-binding domain that specifically binds to a second epitope of HER3.

[0032] In some embodiments, the first antigen-binding domain comprises a first heavy chain variable region (VH1) and a first light chain variable region (VL1), and the second antigen-binding domain comprises a second heavy chain variable region (VH2) and a second light chain variable region (VL2).

[0033] In some embodiments, the first heavy chain variable region (VH1) includes complementarity-determining regions (CDRs) 1, 2, and 3, wherein the VH1 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR1, the VH1 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR2, and the VH1 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR3, and the first light chain variable region (VL1) includes CDRs 1, 2, and 3, wherein the VL1 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR1, the VL1 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR2, and the VL1 CDR3 region includes a selected VL1 It contains an amino acid sequence that is at least 80% identical to the amino acid sequence of CDR3, The amino acid sequences of the selected VH1 CDR1, 2, and 3, and the amino acid sequences of the selected VL1 CDR1, 2, and 3, are one of the following: (1) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 4 to 6, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (2) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 7 to 9, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (3) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 10 to 12, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (4) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 13 to 15, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (5) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 16-18, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1-3, respectively. (6) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 22-24, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (7) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 25-27, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (8) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 28-30, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (9) The amino acid sequences of the above-selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 31-33, respectively, and the amino acid sequences of the above-selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively, and (10) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 34 to 36, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0034] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0035] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0036] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 10 to 12, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0037] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 13 to 15, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively.

[0038] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 16-18, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1-3, respectively.

[0039] In some embodiments, the second heavy chain variable region (VH2) comprises CDR1, 2, and 3, wherein the VH2 CDR1 region comprises an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR1, the VH2 CDR2 region comprises an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR2, and the VH2 CDR3 region comprises an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR3, and The second light chain variable region (VL2) described above includes CDR1, 2, and 3, wherein the VL2 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR1, the VL2 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR2, and the VL2 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR3. The amino acid sequences of the selected VH2 CDR1, 2, and 3, and the amino acid sequences of the selected VL2 CDR1, 2, and 3, are one of the following: (1) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 4 to 6, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (2) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 7 to 9, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (3) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 10 to 12, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (4) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 13 to 15, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (5) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 16-18, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1-3, respectively. (6) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 22-24, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (7) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 25-27, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (8) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 28-30, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (9) The amino acid sequences of the above-selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 31-33, respectively, and the amino acid sequences of the above-selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively, and (10) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 34 to 36, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0040] In some embodiments, the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0041] In some embodiments, the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0042] In some embodiments, the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 10 to 12, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively.

[0043] In some embodiments, the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0044] In some embodiments, the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 16-18, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1-3, respectively.

[0045] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0046] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 31-33, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 19-21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 25-27, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 19-21, respectively.

[0047] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 16-18, the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1-3, the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 7-9, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1-3.

[0048] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 34 to 36, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 25 to 27, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0049] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0050] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 22 to 24, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 25 to 27, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0051] In some embodiments, VH1 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VH sequence, and VL1 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, and the selected VL sequence is sequence number 37, (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

[0052] In some embodiments, the VH2 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VH sequence, and the VL2 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, and the selected VL sequence is sequence number 37, (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

[0053] In some embodiments, VH1 includes VH1 CDR1, VH1 CDR2, and VH1 CDR3 which are identical to VH CDR1, VH CDR2, and VH CDR3 of the selected VH sequence, and VL1 includes VL1 CDR1, VL1 CDR2, and VL1 CDR3 which are identical to VL CDR1, VL CDR2, and VL CDR3 of the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, and the selected VL sequence is sequence number 37, (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

[0054] In some embodiments, VH2 includes VH2 CDR1, VH2 CDR2, and VH2 CDR3 which are identical to VH CDR1, VH CDR2, and VH CDR3 of the selected VH sequence, and VL2 includes VL2 CDR1, VL2 CDR2, and VL2 CDR3 which are identical to VL CDR1, VL CDR2, and VL CDR3 of the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, and the selected VL sequence is sequence number 37, (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

[0055] In one embodiment, the disclosure relates to an antibody or antigen-binding fragment thereof, comprising a first antigen-binding domain that specifically binds to HER3 and a second antigen-binding domain that specifically binds to MET.

[0056] In some embodiments, the first antigen-binding domain comprises a first heavy chain variable region (VH1) and a first light chain variable region (VL1), and the second antigen-binding domain comprises a second heavy chain variable region (VH2) and a second light chain variable region (VL2).

[0057] In some embodiments, the first heavy chain variable region (VH1) includes complementarity-determining regions (CDRs) 1, 2, and 3, wherein the VH1 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR1, the VH1 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR2, and the VH1 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR3, and The first light chain variable region (VL1) described above includes CDR1, 2, and 3, wherein the VL1 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR1, the VL1 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR2, and the VL1 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR3. The amino acid sequences of the selected VH1 CDR1, 2, and 3, and the amino acid sequences of the selected VL1 CDR1, 2, and 3, are one of the following: (1) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 4 to 6, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (2) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 7 to 9, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (3) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 10 to 12, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (4) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 13 to 15, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (5) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 16-18, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1-3, respectively. (6) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 22-24, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (7) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 25-27, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (8) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 28-30, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (9) The amino acid sequences of the above-selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 31-33, respectively, and the amino acid sequences of the above-selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively, and (10) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 34 to 36, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0058] In some embodiments, the second heavy chain variable region (VH2) comprises CDR1, 2, and 3, wherein the VH2 CDR1 region comprises an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR1, the VH2 CDR2 region comprises an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR2, and the VH2 CDR3 region comprises an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR3, and The second light chain variable region (VL2) described above includes CDR1, 2, and 3, wherein the VL2 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR1, the VL2 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR2, and the VL2 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR3. The amino acid sequences of the selected VH2 CDR1, 2, and 3, and the amino acid sequences of the selected VL2 CDR1, 2, and 3, are one of the following: (1) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 51 to 53, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (2) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 54 to 56, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (3) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 57 to 59, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively. (4) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 60-62, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (5) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 69 to 71, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (6) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 72-74, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1-3, respectively. (7) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 75-77, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively, and (8) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 78 to 80, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0059] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51 to 53, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0060] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51 to 53, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0061] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 10 to 12, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51 to 53, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0062] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51 to 53, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0063] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 16-18, the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1-3, the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51-53, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1-3.

[0064] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54 to 56, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0065] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54 to 56, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0066] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54 to 56, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0067] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 10 to 12, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54 to 56, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0068] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 16-18, the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1-3, the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54-56, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1-3.

[0069] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 69 to 71, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0070] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 69 to 71, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0071] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 69 to 71, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0072] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 72 to 74, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0073] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 72 to 74, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0074] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 72 to 74, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0075] In some embodiments, VH1 comprises an amino acid sequence that is at least 90% identical to the selected VH sequence, and VL1 comprises an amino acid sequence that is at least 90% identical to the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, and the selected VL sequence is sequence number 37, (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

[0076] In some embodiments, the VH2 comprises an amino acid sequence that is at least 90% identical to the selected VH sequence, and the VL2 comprises an amino acid sequence that is at least 90% identical to the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 63, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 64, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 81, and the selected VL sequence is sequence number 37, (4) The selected VH sequence is sequence number 82, and the selected VL sequence is sequence number 37.

[0077] In one embodiment, this disclosure relates to an antibody or an antigen-binding fragment that cross-competes with an antibody or an antigen-binding fragment described herein.

[0078] In some embodiments, the antibody or its antigen-binding fragment includes a fragment crystallizable region (Fc region).

[0079] In some embodiments, the Fc region exhibits increased complement-dependent cell-mediated cytotoxicity (CDC) or antibody-dependent cell-mediated cytotoxicity (ADCC).

[0080] In one embodiment, the disclosure relates to nucleic acids comprising polynucleotides that encode a polypeptide including the following: (1) An immunoglobulin heavy chain or fragment thereof comprising a heavy chain variable region (VH) containing complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 4 to 6, wherein the VH binds to HER3 when paired with a light chain variable region (VL) containing the amino acid sequence shown in SEQ ID NO. 37. (2) An immunoglobulin light chain or fragment thereof comprising a VL containing complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 1 to 3, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO. 38. (3) An immunoglobulin heavy chain or fragment thereof comprising a heavy chain variable region (VH) comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 7 to 9, wherein the VH binds to HER3 when paired with a light chain variable region (VL) containing the amino acid sequence shown in SEQ ID NO. 37. (4) An immunoglobulin light chain or fragment thereof comprising a VL containing complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which, when paired with a VH containing the amino acid sequence shown in SEQ ID NO: 39, binds to HER3. (5) An immunoglobulin heavy chain or fragment thereof comprising a VH comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 10 to 12, wherein the VH binds to HER3 when paired with a light chain variable region (VL) containing the amino acid sequence shown in SEQ ID NO. 37. (6) An immunoglobulin light chain or fragment thereof comprising a VL containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 1 to 3, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO. 40. (7) An immunoglobulin heavy chain or fragment thereof comprising a VH comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 13 to 15, wherein the VH binds to HER3 when paired with a light chain variable region (VL) containing the amino acid sequence shown in SEQ ID NO. 37. (8) An immunoglobulin light chain or fragment thereof comprising a VL containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs: 1 to 3, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO: 41. (9) An immunoglobulin heavy chain or fragment thereof comprising a VH comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 16 to 18, wherein the VH binds to HER3 when paired with a light chain variable region (VL) containing the amino acid sequence shown in SEQ ID NO. 37. (10) An immunoglobulin light chain or fragment thereof comprising a VL containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs: 1 to 3, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO: 42. (11) An immunoglobulin heavy chain or fragment thereof comprising a heavy chain variable region (VH) comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 22 to 24, wherein the VH binds to HER3 when paired with a light chain variable region (VL) containing the amino acid sequence shown in SEQ ID NO. 37. (12) An immunoglobulin light chain or fragment thereof comprising a VL containing complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 19 to 21, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO. 38. (13) An immunoglobulin heavy chain or fragment thereof comprising a heavy chain variable region (VH) comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 25 to 27, wherein the VH binds to HER3 when paired with a light chain variable region (VL) containing the amino acid sequence shown in SEQ ID NO. 37. (14) An immunoglobulin light chain or fragment thereof comprising a VL containing complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 19 to 21, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO. 39. (15) An immunoglobulin heavy chain or fragment thereof comprising a VH comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 28 to 30, wherein the VH binds to HER3 when paired with a light chain variable region (VL) containing the amino acid sequence shown in SEQ ID NO. 37. (16) An immunoglobulin light chain or fragment thereof comprising a VL containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 19 to 21, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO. 40. (17) An immunoglobulin heavy chain or fragment thereof comprising a VH comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which include the amino acid sequences shown in SEQ ID NOs. 31 to 33, wherein the VH binds to HER3 when paired with a light chain variable region (VL) comprising the amino acid sequence shown in SEQ ID NO. 37. (18) An immunoglobulin light chain or fragment thereof comprising a VL containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 19 to 21, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO. 41. (19) An immunoglobulin heavy chain or fragment thereof comprising a VH comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 34 to 36, wherein the VH binds to HER3 when paired with a light chain variable region (VL) containing the amino acid sequence shown in SEQ ID NO. 37, or (20) An immunoglobulin light chain or fragment thereof comprising a VL comprising CDR1, 2, and 3, each comprising the amino acid sequences shown in SEQ ID NOs. 19 to 21, wherein the VL binds to HER3 when paired with a VH comprising the amino acid sequence shown in SEQ ID NO. 42.

[0081] In some embodiments, the nucleic acid comprises a polynucleotide encoding a polypeptide, which comprises a VL containing an immunoglobulin light chain or fragment thereof, which comprises CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs: 1 to 3, respectively.

[0082] In some embodiments, the nucleic acid comprises a polynucleotide encoding a polypeptide, which includes a VL comprising an immunoglobulin light chain or fragment thereof, which comprises CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 19 to 21.

[0083] In some embodiments, the nucleic acid comprises a polynucleotide encoding a polypeptide, which comprises an immunoglobulin heavy chain or fragment thereof, and includes a VH comprising CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs: 4-6, respectively.

[0084] In some embodiments, the nucleic acid comprises a polynucleotide encoding a polypeptide, comprising an immunoglobulin heavy chain or fragment thereof, comprising a VH containing CDR1, 2, and 3, which include the amino acid sequences shown in SEQ ID NOs. 7-9.

[0085] In some embodiments, the nucleic acid comprises a polynucleotide encoding a polypeptide, comprising an immunoglobulin heavy chain or fragment thereof, comprising a VH containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 10 to 12, respectively.

[0086] In some embodiments, the nucleic acid comprises a polynucleotide encoding a polypeptide, comprising an immunoglobulin heavy chain or fragment thereof, comprising a VH containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 13-15, respectively.

[0087] In some embodiments, the nucleic acid comprises a polynucleotide encoding a polypeptide, which comprises a VH containing an immunoglobulin heavy chain or fragment thereof, which comprises CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 16-18, respectively.

[0088] In some embodiments, the nucleic acid comprises a polynucleotide encoding a polypeptide, which comprises a VH comprising an immunoglobulin heavy chain or fragment thereof, which comprises CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 22-24, respectively.

[0089] In some embodiments, the nucleic acid comprises a polynucleotide encoding a polypeptide, comprising an immunoglobulin heavy chain or fragment thereof, comprising a VH containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 25-27.

[0090] In some embodiments, the nucleic acid comprises a polynucleotide encoding a polypeptide, comprising an immunoglobulin heavy chain or fragment thereof, comprising a VH containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 28-30, respectively.

[0091] In some embodiments, the nucleic acid comprises a polynucleotide encoding a polypeptide, comprising an immunoglobulin heavy chain or fragment thereof, comprising a VH containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 31-33, respectively.

[0092] In some embodiments, the nucleic acid comprises a polynucleotide encoding a polypeptide, comprising an immunoglobulin heavy chain or fragment thereof, comprising a VH containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 34-36, respectively.

[0093] In some embodiments, when VH pairs with VL, it specifically binds to human HER3, mouse HER3, monkey HER3, or canine HER3, or when VL pairs with VH, it specifically binds to human HER3, mouse HER3, monkey HER3, or canine HER3.

[0094] In some embodiments, the immunoglobulin heavy chain or fragment thereof is a human immunoglobulin heavy chain or fragment thereof (for example, a human IgG1 heavy chain or fragment thereof, a human IgG2 antibody or its antigen-binding fragment, or a human IgG4 heavy chain or fragment thereof), and the immunoglobulin light chain or fragment thereof is a human immunoglobulin light chain or fragment thereof.

[0095] In some embodiments, the nucleic acid encodes a single-stranded variable fragment (scFv), a single-arm antibody, a multispecific antibody (e.g., a bispecific antibody), or a chimeric antigen receptor (CAR).

[0096] In some embodiments, the nucleic acid is cDNA.

[0097] In one embodiment, this disclosure relates to nucleic acids encoding antibodies or antigen-binding fragments thereof as described herein.

[0098] In one embodiment, this disclosure relates to a vector comprising one or more nucleic acids described herein.

[0099] In one embodiment, the present disclosure relates to a vector comprising two of the nucleic acids described herein, wherein the vector encodes the VL region and the VH region that bind together to HER3.

[0100] In one embodiment, the disclosure relates to a pair of vectors, each comprising one of the nucleic acids described herein, wherein the pair of vectors encode a pair of VL and VH regions that bind together to HER3.

[0101] In one embodiment, this disclosure relates to a cell comprising a vector described herein, or a pair of vectors described herein.

[0102] In some embodiments, the above cells are CHO cells.

[0103] In one embodiment, this disclosure relates to a cell comprising one or more nucleic acids described herein.

[0104] In one embodiment, the present disclosure relates to a method for producing an antibody or an antigen-binding fragment thereof, wherein the method is (a) Culturing the cells described herein under conditions sufficient to produce the antibodies or antigen-binding fragments thereof, (b) The method includes recovering the antibody or antigen-binding fragment produced by the cells.

[0105] In one embodiment, this disclosure relates to a chimeric antigen receptor (CAR) comprising an antibody or an antigen-binding fragment thereof as described herein.

[0106] In one embodiment, the present disclosure relates to an antibody-drug conjugate comprising an antibody or antigen-binding fragment thereof, covalently bound to a therapeutic agent, as described herein.

[0107] In some embodiments, the therapeutic agent is a cytotoxic agent or a cell proliferation inhibitor.

[0108] In some embodiments, the therapeutic agent is MMAE or MMAF.

[0109] In some embodiments, the therapeutic agent is selected from the following: [ka]

[0110] In some embodiments, the therapeutic agent is linked to the antibody or its antigen-binding fragment via a linker. In some embodiments, the linker has the following structure. [ka]

[0111] In some embodiments, the antibody-drug conjugate has the following structure. [ka]

[0112] In some embodiments, n=1, 2, 3, 4, 5, 6, 7, or 8, and in some embodiments, "Ab" represents an antibody or its antigen-binding fragment as described herein.

[0113] In one embodiment, the present disclosure relates to a method for treating a subject having cancer, the method comprising administering to the subject a therapeutically effective amount of a composition comprising an antibody or antigen-binding fragment thereof as described herein, a CAR as described herein, or an antibody-drug conjugate as described herein.

[0114] In some embodiments, the subject has a solid tumor.

[0115] In some embodiments, the cancer is colorectal cancer, gastric cancer, breast cancer, lung cancer, melanoma, ovarian cancer, head and neck cancer, pancreatic cancer, or cervical cancer.

[0116] In some embodiments, the subjects are further treated with an effective amount of anti-4-1BB antibody, anti-OX40 antibody, anti-PD-1 antibody, anti-CTLA4 antibody, anti-CD40 antibody, or anti-PD-L1 antibody.

[0117] In one embodiment, the present disclosure relates to a method for reducing the rate of tumor growth, the method comprising contacting tumor cells with a composition comprising an effective amount of an antibody or antigen-binding fragment thereof as described herein, a CAR as described herein, or an antibody-drug conjugate as described herein.

[0118] In one embodiment, the present disclosure relates to a method for killing tumor cells, the method comprising contacting the tumor cells with an effective amount of a composition comprising an antibody or antigen-binding fragment thereof as described herein, a CAR as described herein, or an antibody-drug conjugate as described herein.

[0119] In one embodiment, the present disclosure relates to a method for increasing an immune response in a subject, the method comprising administering to the subject an effective amount of a composition comprising an antibody or antigen-binding fragment thereof as described herein, a CAR as described herein, or an antibody-drug conjugate as described herein.

[0120] In one embodiment, the present disclosure relates to a pharmaceutical composition comprising an antibody or antigen-binding fragment thereof as described herein and a pharmaceutically acceptable carrier.

[0121] In one embodiment, the present disclosure relates to a pharmaceutical composition comprising an antibody-drug conjugate described herein and a pharmaceutically acceptable carrier.

[0122] In some embodiments, the drug-antibody ratio (DAR) is approximately 4 or 8.

[0123] As used herein, the term “cancer” means cells capable of autonomous proliferation. Examples of such cells include cells in an abnormal state or condition characterized by rapid proliferation. The term means cancerous growth, e.g., tumors, oncogenic processes, metastatic tissues, and malignant transformed cells, tissues, or organs, regardless of the type of tissue change or stage of invasiveness. Malignancies of various organ systems, e.g., respiratory, cardiovascular, renal, reproductive, hematologic, nervous, liver, gastrointestinal, and endocrine systems, as well as most colon cancers, renal cell carcinoma, prostate cancer and / or testicular tumors, non-small cell lung cancer, and small intestine cancer. “Spontaneously occurring” cancers include any cancer that is not experimentally induced by transplanting cancer cells into a subject, e.g., spontaneously occurring cancers, cancers caused by exposure of a patient to a carcinogen, cancers resulting from transgenic oncogene insertions or tumor suppressor gene knockouts, and cancers caused by infections, e.g., viral infections. The term "carcinoma" is recognized in the art and refers to a malignant tumor of epithelial or endocrine glandular tissue. This term also includes carcinosarcoma, which is a malignant tumor composed of cancerous and sarcomatous tissue. "Adenocarcinoma" refers to a carcinoma of glandular origin, or a carcinoma in which tumor cells form recognizable glandular structures. The term "sarcoma" is recognized in the art and refers to a malignant tumor of mesenchymal origin. The term "hematopoietic neoplastic disease" includes diseases involving hematopoietic hyperplasia / neoplastic cells. Hematopoietic neoplastic diseases may originate from the bone marrow, lymphoid system, or erythrocyte lineage, or their progenitor cells.

[0124] As used herein, the term “antibody” means any antigen-binding molecule that contains at least one (e.g., 1, 2, 3, 4, 5, or 6) complementarity-determining regions (CDRs) (e.g., any of three CDRs derived from an immunoglobulin light chain or any of three CDRs derived from an immunoglobulin heavy chain) and is capable of specifically binding to an epitope. Non-limiting examples of antibodies include monoclonal antibodies, polyclonal antibodies, multispecific antibodies (e.g., bispecific antibodies), single-chain antibodies, chimeric antibodies, human antibodies, and humanized antibodies. In some embodiments, antibodies may contain the Fc region of a human antibody. The term antibody also includes derivatives, such as bispecific antibodies, single-chain antibodies, diabodies, linear antibodies, and multispecific antibodies formed from antibody fragments.

[0125] As used herein, the term “antigen-binding fragment” means a portion of a full-length antibody, the portion of which is specifically capable of binding to an antigen. In some embodiments, the antigen-binding fragment contains at least one variable domain (e.g., a variable domain in the heavy chain or a variable domain in the light chain). Non-limiting examples of antibody fragments include, for example, Fab, Fab', F(ab')2, and Fv fragments.

[0126] As used herein, the term “human antibody” means an antibody encoded by endogenous nucleic acids present in humans (e.g., rearranged human immunoglobulin heavy or light chain loci). In some embodiments, human antibodies are recovered from humans or produced in human cell culture media (e.g., in human hybridoma cells). In some embodiments, human antibodies are produced in non-human cells (e.g., mouse or hamster cell lines). In some embodiments, human antibodies are produced in bacterial or yeast cells. In some embodiments, human antibodies are produced in transgenic non-human animals (e.g., cattle) containing unarranged or rearranged human immunoglobulin loci (e.g., heavy or light chain human immunoglobulin loci).

[0127] As used herein, the term “chimeric antibody” means an antibody containing sequences present in at least two different antibodies (e.g., antibodies derived from two different mammalian species, such as human and mouse antibodies). Non-limiting examples of chimeric antibodies include antibodies containing variable domain sequences (e.g., all or part of the light chain and / or heavy chain variable domain sequences) of a non-human (e.g., mouse) antibody, as well as constant domains of a human antibody. Further examples of chimeric antibodies are described herein and are well known in the art.

[0128] As used herein, the term “humanized antibody” means a non-human antibody that contains minimal sequences derived from non-human (e.g., mouse) immunoglobulin and sequences derived from human immunoglobulin. In non-limiting examples, a humanized antibody is a human antibody (recipient antibody) in which residues in the hypervariable (e.g., CDR) region of the recipient antibody are replaced by residues in the hypervariable (e.g., CDR) region of a non-human antibody (e.g., donor antibody), such as a mouse, rat, or rabbit antibody having desired specificity, affinity, and capability. In some embodiments, Fv framework residues of human immunoglobulin are replaced by corresponding non-human (e.g., mouse) immunoglobulin residues. In some embodiments, the humanized antibody may contain residues not found in the recipient antibody or donor antibody. These modifications can further refine the performance of the antibody. In some embodiments, the humanized antibody contains substantially all, at least one, and typically two, variable domains, with all or substantially all of the hypervariable loop (CDR) corresponding to the hypervariable loop of a non-human (e.g., mouse) immunoglobulin, and all or substantially all of the framework region being a human immunoglobulin sequence. The humanized antibody may also contain an immunoglobulin constant region (Fc), typically at least a portion of the constant region of a human immunoglobulin. The humanized antibody can be produced using molecular biological methods well known in the art. Non-limiting examples of methods for producing the humanized antibody are described herein.

[0129] As used herein, the term “single-chain antibody” means a single polypeptide containing at least two immunoglobulin variable domains (e.g., variable domains of mammalian immunoglobulin heavy or light chains) that are specifically capable of binding to an antigen. Non-limiting examples of single-chain antibodies are described herein.

[0130] As used herein, the term “multispecific antibody” refers to an antibody comprising two or more different antigen-binding domains that collectively and specifically bind to two or more different epitopes. The two or more different epitopes may be epitopes on the same antigen (e.g., a single polypeptide present on the surface of a cell) or epitopes on different antigens (e.g., different proteins present on the surface of the same cell or on the surfaces of different cells). In some embodiments, a multispecific antibody binds to two different epitopes (e.g., a “bispecific antibody”). In some embodiments, a multispecific antibody binds to three different epitopes (e.g., a “triplespecific antibody”). In some embodiments, a multispecific antibody binds to four different epitopes (e.g., a “quadrispecific antibody”). In some embodiments, a multispecific antibody binds to five different epitopes (e.g., a “quintuplespecific antibody”). Each binding specificity can exist at any appropriate valency. Non-limiting examples of multispecific antibodies are described herein.

[0131] As used herein, the term “bispecific antibody” means an antibody that binds to two different epitopes. Epitopes may be present on the same antigen or on different antigens.

[0132] As used herein, the term “common light chain” means a single light chain that can interact with two or more different heavy chains forming different antigen-binding sites, and these different antigen-binding sites can specifically bind to different antigens or epitopes. Similarly, the term “common light chain variable region” means a single light chain variable region that can interact with two or more different heavy chain variable regions forming different antigen-binding sites, and these different antigen-binding sites can specifically bind to different antigens or epitopes. In some embodiments, an antibody or its antigen-binding fragment may have a common light chain. In some embodiments, the antibody or its antigen-binding fragment described herein may have a common light chain variable region.

[0133] As used herein, the term “anti-HER3 / MET antibody or its antigen-binding fragment” refers to an antibody or antigen-binding fragment that binds to both MET and HER3.

[0134] As used herein, the terms “subject” and “patient” are used interchangeably throughout the specification and refer to animals, humans, or non-humans to which treatment according to the methods of the present invention is provided. Veterinary and non-veterinary uses are conceived by the present invention. Human patients may be adult humans or young humans (e.g., humans under 18 years of age). In addition to humans, patients include, but are not limited to, mice, rats, hamsters, guinea pigs, rabbits, ferrets, cats, dogs, and primates. Examples include non-human primates (e.g., monkeys, chimpanzees, gorillas, etc.), rodents (e.g., rats, mice, gerbils, hamsters, ferrets, rabbits), rabbits, pigs (e.g., pigs, miniature pigs), equids, canids, felines, bovines, and other domestic, livestock, and zoo animals.

[0135] As used herein, when referring to an antibody, the terms "specifically binding" and "specifically binds" mean that the antibody preferably interacts with its target molecule (e.g., HER3) more than with other molecules, because the interaction depends on the presence of a specific structure (i.e., an antigenic determinant or epitope) on the target molecule; in other words, the reagent recognizes and binds to a molecule containing a specific structure, rather than to all general molecules. An antibody that specifically binds to a target molecule may also be called a target-specific antibody. For example, an antibody that specifically binds to the HER3 molecule may also be called a HER3-specific antibody or an anti-HER3 antibody.

[0136] As used herein, the terms “polypeptide,” “peptide,” and “protein” are used interchangeably and mean polymers of at least two amino acids of any length.

[0137] As used herein, the terms “polynucleotide,” “nucleic acid molecule,” and “nucleic acid sequence” are used interchangeably and mean, but are not limited to, polymers of nucleotides of any length, of at least two nucleotides, including, but not limited to, DNA, RNA, DNA / RNA hybrids, and modifications thereof.

[0138] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art. Methods and materials for use in the present invention are described herein, but other suitable methods and materials well known in the art may also be used. Materials, methods, and examples are illustrative and not intended to be limiting. All publications, patent applications, patents, sequences, database entries, and other references referenced herein are incorporated by reference in their entirety. In case of any conflict, this specification, including definitions, shall prevail.

[0139] Other features and advantages of the present invention will become apparent from the following detailed description and drawings, as well as from the claims. [Brief explanation of the drawing]

[0140] [Figure 1] Figures 1A-G show the cross-binding activity of anti-HER3 antibodies to HER family proteins, as determined by surface plasmon resonance (SPR). [Figure 2] This shows the mean tumor volume in different groups of B-NDG mice treated with PBS or ADC after subcutaneous injection of gastric cancer NUGC-4 cells. [Figure 3A] This lists the CDR sequences of the heavy chain variable region and light chain variable region of anti-HER3 antibodies as defined by Kabat numbering. [Figure 3B] This lists the CDR sequences of the heavy chain variable region and light chain variable region of anti-MET antibodies as defined by Kabat numbering. [Figure 4A] This lists the CDR sequences of the heavy chain variable region and light chain variable region of anti-HER3 antibodies as defined by Chothia numbering. [Figure 4B] This lists the CDR sequences of the heavy chain variable region and light chain variable region of anti-MET antibodies as defined by Chothia numbering. [Figure 5] The heavy chain variable regions and light chain variable regions of anti-HER3 antibodies and anti-MET antibodies are listed below. [Figure 6] This shows the mean tumor volume in different groups of B-NDG mice treated with PBS, ISO-ADC, or ADC after subcutaneous injection of gastric cancer NUGC-4 cells. [Figure 7] This shows the mean tumor volume in different groups of B-NDG mice treated with subcutaneous injection of gastric cancer NUGC-4 cells and either PBS or bispecific ADC. [Figure 8] This shows the mean tumor volume in different groups of B-NDG mice treated with PBS or ADC after subcutaneous injection of pancreatic cancer fragments. [Figure 9] This shows an exemplary bispecific antibody having antigen-binding arms derived from different antibodies. [Figure 10-1]The selected amino acid sequences discussed in this disclosure are listed below. [Figure 10-2] Same as above [Figure 10-3] Same as above [Figure 10-4] Same as above [Figure 11] This shows the mean tumor volume in different groups of B-NDG mice treated with PBS or ADC after subcutaneous injection of pancreatic cancer fragments. [Figure 12] Figures 12A-C show the in vitro killing activity of ADCs in NUGC-4 cells, SNU-5 cells, and PLC-PRF-5 cells. [Figure 13] This shows the mean tumor volume in different groups of B-NDG mice treated with PBS or ADC after subcutaneous injection of gastric cancer fragments. [Figure 14] This shows the mean tumor volume in different groups of B-NDG mice treated with PBS or ADC after subcutaneous injection of pancreatic cancer fragments. [Figure 15] This shows the mean tumor volume in different groups of B-NDG mice treated with subcutaneous injection of colorectal cancer cells and either PBS or ADC. [Figure 16] This shows the mean tumor volume in different groups of B-NDG mice treated with PBS or ADC after subcutaneous injection of gastric cancer fragments. [Figure 17] This shows the mean tumor volume in different groups of B-NDG mice treated with subcutaneous injection of colorectal cancer fragments and either PBS or ADC. [Figure 18] This shows the mean tumor volume in different groups of B-NDG mice treated with subcutaneous injection of colorectal cancer fragments and either PBS or ADC. [Modes for carrying out the invention]

[0141] This disclosure provides examples of antibodies that bind to HER3 and / or MET, and their antigen-binding fragments.

[0142] HER3 is a pseudokinase member of the EGFR family that plays a role in both tumor progression and drug resistance. While HER3 is not oncogenic on its own, it is an exceptional EGFR family member that, in cooperation with other receptors, can induce tumorigenesis, metastatic events, and drug resistance. HER3 is a potent cancer therapeutic target. In contrast to EGFR and HER2, which have been widely targeted by TKIs, HER3 has been targeted primarily by monoclonal or bispecific antibodies with minimal kinase activity, either by blocking ligand binding or heterodimerization with other receptors.

[0143] HER proteins are a family of receptor tyrosine kinases that play a role in the biology of both normal and tumor cells. This family consists of four highly homologous members: EGFR (ERBB1 / HER1), HER2 (ERBB2), HER3 (ERBB3), and HER4 (ERBB4), each comprising a ligand-binding extracellular domain, a transmembrane domain, an intracellular kinase domain, and a C-terminal tail. Family members (except HER2) are generally activated by the binding of extracellular ligands, inducing structural changes, followed by homodimerization or heterodimerization among family members, ultimately leading to activation of the intracellular signaling cascade. Cellular responses include increased cell survival and proliferation, explaining why abnormal EGFR family signaling is strongly associated with tumorigenetic events.

[0144] HER3 is a unique member of the EGFR family with little to no intracellular tyrosine kinase activity. Compared to other EGFR family members, HER3 is branched at key residues in its kinase domain and is fixed in an inactive-like structure. While some kinase activity of HER3 has been reported, it is suggested to be 1,000 times weaker than the kinase activity of fully activated EGFR. Because HER3 cannot form homodimers, its activation depends on heterodimerization with another receptor, inducing downstream C-terminal phosphorylation events.

[0145] The HER3 gene is located on the long arm of chromosome 12 (12q13.2) and encodes a 180kDa protein. The extracellular domain of HER3 is divided into four subdomains (I-IV). Subdomains I and III are leucine-rich β-helical regions responsible for ligand binding, while subdomains II and IV are cysteine-rich regions. Subdomain II also contains a dimerization arm necessary for interaction with other receptors. Following the transmembrane domain are a flexible near-membrane region, a kinase domain, and an intracellular domain surrounding the C-terminal tail. In the absence of a ligand, HER3 remains inactive due to binding between subdomains II and IV. Upon ligand binding, the kinase domain of the dimerization partner transphosphates the tyrosine residues in the C-terminal tail of HER3.

[0146] HER3's preferred dimerization partners are EGFR and HER2, followed by its lower affinity for HER4. HER3 also dimerizes with several non-EGFR family receptors, including the mesenchymal transition factor (MET) receptor and FGFR2. Six of HER3's 11 tyrosine phosphorylation sites are direct recruiters of PI3K, making HER3 a potent activator of the PI3K / protein kinase B (AKT) signaling pathway, which is crucial for cancer cell survival. HER3 also activates MAPK signaling, stimulating cell proliferation. Other proposed effectors of HER3 include JAK and transcription activators, as well as the proto-oncogene tyrosine protein kinase SRC signaling pathway, which is involved in signaling and increased cell proliferation.

[0147] In contrast to other EGFR family members, HER3 is not oncogenic when overexpressed alone. However, ubiquitous HER3 expression has been detected in various cancers, including breast, ovarian, colon, gastric, lung, skin, and pancreatic cancers. High HER3 expression is also associated with disease progression and / or poor prognosis in many cancer types.

[0148] While HER3 itself does not induce tumorigenesis, the HER2:HER3 heterodimer possesses the highest transformative potential among all possible EGFR family dimers. Due to the superior tumorigenetic ability of the dimer pair, HER3 is important for HER2-mediated tumorigenesis in multiple tumor types. HER3 overexpression is a frequent occurrence, particularly in HER2-positive breast cancer, and elevated HER3 expression has been shown in mice expressing the neu(rodent HER2) transgene. In breast cancer cell lines, EGFR is not required, while HER3 is shown to be important for maintaining cell viability. Furthermore, inhibition of HER3 abolishes HER2-dependent tumorigenesis in transgenic mammary tumor models. HER3 is also involved in the development of non-small cell lung cancer (NSCLC), many of which have EGFR mutations.

[0149] HER3 expression functions as a bypass mechanism for various targeted therapies, and elevated HER3 signaling confers resistance to multiple therapeutic agents. Because HER3 dimerizes with non-EGFR receptors, including the HER2 receptor and the MET receptor, HER3 can confer resistance to EGFR-targeted therapies through dimerization with non-EGFR partners. Early on, HER2:HER3-mediated signaling was shown to be associated with resistance to EGFR tyrosine kinase inhibitors (TKIs), gefitinib, in head and neck cancer and breast cancer. Subsequently, increased HER3 ligand NRG1 and subsequent HER2:HER3 dimerization were shown to confer resistance to cetuximab, an EGFR-targeted antibody, in colorectal cancer. Similarly, increased EGFR:HER3 dimerization was found in the majority of residual tumor burden in patients with cetuximab / panitumumab-resistant breast cancer. Other anti-HER TKIs, such as osimertinib, may also induce HER3 upregulation as part of the resistance mechanism. Resistance to this NRG1-driven EGFR inhibitor was reversed by the use of patritumab, a HER3-selective antibody.

[0150] HER3 expression is also associated with resistance to hormone therapy. HER3 plays a crucial role in HER2 phosphorylation in breast cancer cells, and HER3 downregulation reversed tamoxifen resistance to the anti-estrogen receptor (ER) in breast cancer cell lines. Furthermore, breast cancer patients with tumors co-expressing HER2 and HER3 are more likely to develop tamoxifen resistance, as measured by disease-free survival. Increased activity of EGFR, HER2, and HER3 was also associated with resistance to fulvestrant, an ER agonist. Fulvestrant treatment enhanced HER3 expression and phosphorylation in breast cancer cells in an NRG1-dependent manner, suggesting this is the mechanism of fulvestrant resistance in breast cancer. In patients with triple-negative breast cancer (TNBC), high HER3 / EGFR protein expression (not HER3 or EGFR alone) was associated with poorer 10-year survival after chemotherapy. Interestingly, compared to patients who did not receive adjuvant chemotherapy, high HER3 / EGFR was associated with poorer survival after adjuvant chemotherapy.

[0151] Detailed reviews of HER3 and its function can be found in Haikala, Heidi M., and Pasi A. Janne. "Thirty Years of HER3: From Basic Biology to Therapeutic Interventions." Clinical Cancer Research 27.13(2021):3528-3539, and Mishra, Rosalin, et al. "HER3 signaling and targeted therapy in cancer." Oncology reviews 12.1(2018), and Liu, Xiaolong, et al. "Development of effective therapeutics targeting HER3 for cancer treatment." Biological procedures online 21.1(2019):1-10, with the entirety of each of these references incorporated here.

[0152] MET, also known as c-MET, tyrosine protein kinase MET, or hepatocyte growth factor receptor (HGFR), is a protein encoded by the MET gene in humans. This protein possesses tyrosine kinase activity. The major single-chain precursor protein is cleaved post-translation to produce α and β subunits, which disulfide-bond to form the mature receptor. Activation of MET by its ligand, hepatocyte growth factor (HGF), stimulates numerous cellular processes, including proliferation, motility, invasion, metastasis, epithelial-mesenchymal transition, angiogenesis / wound healing, and tissue regeneration. The exact stoichiometry of HGF:MET binding is unknown, but it is generally believed that two HGF molecules bind to two MET molecules, causing receptor dimerization and autophosphorylation at tyrosines 1230, 1234, and 1235. Ligand-independent MET autophosphorylation can also occur through gene amplification, mutation, or receptor overexpression.

[0153] MET is frequently amplified, mutated, or overexpressed in many types of cancer, including gastric, lung, colon, breast, bladder, head and neck, ovarian, prostate, thyroid, pancreatic, and CNS cancers. Missense mutations, typically localized to the kinase domain, are commonly found in hereditary papillary renal cell carcinoma (PRCC) and 13% of sporadic PRCC cases, while MET mutations localized to the semaphorin or near-membrane domains are frequently found in gastric, head and neck, liver, ovarian, NSCLC, and thyroid cancers. MET amplification has been detected in brain tumors, colorectal, gastric, and lung cancers and is often correlated with disease progression. Up to 4% and 20% of non-small cell lung cancers (NSCLC) and gastric cancers, respectively, show MET amplification. MET overexpression is also frequently observed in lung cancer. Furthermore, in clinical samples, nearly half of lung adenocarcinomas showed high levels of MET and HGF, both of which were correlated with increased tumor growth rate, metastasis, and poor prognosis.

[0154] Approximately 60% of tumors that become resistant to EGF tyrosine kinase inhibitors increase MET expression, amplify MET, or increase HGF, the only known ligand for MET, suggesting the existence of a MET-mediated compensatory pathway for EGFR. MET amplification was first identified in cultured cells that became resistant to the EGFR kinase inhibitor gefitinib and showed improved survival via the HER3 pathway. This was further validated in clinical samples, where 9 out of 43 patients who became resistant to either erlotinib or gefitinib showed MET amplification.

[0155] Abnormal MET signaling is thought to be involved in the development / progression of many human cancers. This is due to MET overexpression, activating mutations in MET, transactivation, autocrine or paracrine signaling, or amplification of the MET gene. When HGF binds to MET, it stimulates receptor dimerization, autophosphorylation, activation of the cytoplasmic tyrosine kinase domain within the receptor, and the initiation of multiple signaling and transactivation pathways involved in DNA synthesis (gene activation) and the regulation of cell cycle progression or division. Therefore, inhibition of MET signaling can lead to inhibition of one or more downstream MET signaling pathways, and neutralizing MET can have a variety of effects, including inhibition of cell proliferation and differentiation, angiogenesis, cell motility, and metastasis.

[0156] Detailed reviews of MET and its function can be found in Huang, X., et al. “Targeting the HGF / MET axis in cancer therapy: challenges in resistance and opportunities for improvement.” Frontiers in Cell and Developmental Biology 8(2020):152, and Santarpia, M., et al. “A narrative review of MET inhibitors in non-small cell lung cancer with MET exon 14 skipping mutations.” Translational Lung Cancer Research 10.3(2021):1536, the entirety of each of these works is incorporated by reference.

[0157] This disclosure provides several anti-HER3 antibodies, their antigen-binding fragments, and methods for inhibiting tumor growth, treating cancer, and treating autoimmune diseases using these anti-HER3 antibodies and antigen-binding fragments. This disclosure also provides several anti-MET antibodies, their antigen-binding fragments, and methods for inhibiting tumor growth, treating cancer, and treating autoimmune diseases using these anti-MET antibodies and antigen-binding fragments.

[0158] Anti-HER3 antibody and antigen-binding fragment This disclosure provides antibodies and antigen-binding fragments that specifically bind to HER3 (e.g., human HER3). The antibodies and antigen-binding fragments described herein are capable of binding to HER3. These antibodies may be agonists or antagonists. In some embodiments, these antibodies can enhance the immune response. In some embodiments, these antibodies can block the activity of HER3, such as the activity of HER3 heterodimers, such as HER2:HER3 heterodimers.

[0159] This disclosure provides, for example, anti-HER3 antibodies 1B2, 1C5, 1D6, 3E1, 3G6, chimeric antibodies thereof, and human antibodies or humanized antibodies thereof.

[0160] CDR sequences for 1B2 and antibodies derived from 1B2 (e.g., human antibodies or humanized antibodies) include the CDRs of the heavy chain variable domain, sequence numbers 4-6, and the CDRs of the light chain variable domain, sequence numbers 1-3, as defined by Kabat numbering. CDRs can also be defined by the Chothia system. Under Chothia numbering, the CDR sequences of the heavy chain variable domain are shown in sequence numbers 22-24, and the CDR sequences of the light chain variable domain are shown in sequence numbers 19-21.

[0161] Similarly, CDR sequences for 1C5 and antibodies derived from 1C5 include the heavy chain variable domain CDRs, SEQ ID NOs. 7-9, and the light chain variable domain CDRs, SEQ ID NOs. 1-3, as defined by Kabat numbering. Under Chothia numbering, the heavy chain variable domain CDR sequences are shown in SEQ ID NOs. 25-27, and the light chain variable domain CDR sequences are shown in SEQ ID NOs. 19-21.

[0162] The CDR sequences of 1D6 and antibodies derived from 1D6 include the heavy chain variable domain CDRs, sequence numbers 10-12, and the light chain variable domain CDRs, sequence numbers 1-3, as defined by Kabat numbering. Under Chothia numbering, the heavy chain variable domain CDR sequences are shown in sequence numbers 28-30, and the light chain variable domain CDR sequences are shown in sequence numbers 19-21.

[0163] The CDR sequences of 3E1 and antibodies derived from 3E1 include the heavy chain variable domain CDRs, sequence numbers 13-15, and the light chain variable domain CDRs, sequence numbers 1-3, as defined by Kabat numbering. Under Chothia numbering, the heavy chain variable domain CDR sequences are shown as sequence numbers 31-33, and the light chain variable domain CDRs are shown as sequence numbers 19-21.

[0164] The CDR sequences of 3G6 and antibodies derived from 3G6 include the heavy chain variable domain CDRs, sequence numbers 16-18, and the light chain variable domain CDRs, sequence numbers 1-3, as defined by Kabat numbering. Under Chothia numbering, the heavy chain variable domain CDR sequences are shown in sequence numbers 34-36, and the light chain variable domain CDRs are shown in sequence numbers 19-21.

[0165] The amino acid sequence of the heavy chain variable region of the 1B2 antibody is shown in SEQ ID NO: 38. The amino acid sequence of the light chain variable region of the 1B2 antibody is shown in SEQ ID NO: 37.

[0166] The amino acid sequence of the heavy chain variable region of the 1C5 antibody is shown in SEQ ID NO: 39. The amino acid sequence of the light chain variable region of the 1C5 antibody is shown in SEQ ID NO: 37.

[0167] The amino acid sequence of the heavy chain variable region of the 1D6 antibody is shown in SEQ ID NO: 40. The amino acid sequence of the light chain variable region of the 1D6 antibody is shown in SEQ ID NO: 37.

[0168] The amino acid sequence of the heavy chain variable region of the 3E1 antibody is shown in SEQ ID NO: 41. The amino acid sequence of the light chain variable region of the 3E1 antibody is shown in SEQ ID NO: 37.

[0169] The amino acid sequence of the heavy chain variable region of the 3G6 antibody is shown in SEQ ID NO: 42. The amino acid sequence of the light chain variable region of the 3G6 antibody is shown in SEQ ID NO: 37.

[0170] In some embodiments, the heavy chain variable region is at least 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to any one of sequence numbers 38-42. In some embodiments, the light chain variable region is at least 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to sequence number 37. The heavy chain variable region sequence can form a pair with a corresponding light chain variable region sequence, which together bind to HER3.

[0171] Humanization percentage refers to the percentage of identity of a heavy chain or light chain variable region sequence compared to a human antibody sequence in the International Immunogenetic Information System (IMGT) database. In some embodiments, the humanization percentage exceeds 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or 95%. Detailed descriptions of methods for determining the humanization percentage and methods for determining top hits are well known in the art, for example, in Jones, et al. “The INNs and outs of antibody nonproprietary names.” MAbs. Vol.8. No.1. Taylor & Francis, 2016, which is incorporated herein by reference in its entirety. Higher humanization percentages often have various advantages, such as being safer and more effective in humans, more likely to be accepted by human subjects, and / or less likely to have side effects. In some embodiments, the variable region is entirely human, derived from, for example, human heavy chain immunoglobulin loci (e.g., a combination of human IGHV, human IGHD, and human IGHJ genes) and / or human kappa chain immunoglobulin loci (e.g., a combination of human IGKV and human IGKJ genes).

[0172] Furthermore, in some embodiments, the antibodies or antigen-binding fragments described herein may also contain one, two, or three heavy chain variable region CDRs selected from the group consisting of SEQ ID NOs: 4-6, 7-9, 10-12, 13-15, 16-18, 22-24, 25-27, 28-30, 31-33, and 34-36, and / or one, two, or three light chain variable region CDRs selected from the group consisting of SEQ ID NOs: 1-3 and 19-21.

[0173] In some embodiments, the antibody may have a heavy chain variable region (VH) comprising complementarity-determining regions (CDRs) 1, 2, and 3, wherein the CDR1 region contains or comprises an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of the selected VH CDR1; the CDR2 region contains or comprises an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of the selected VH CDR2; and the CDR3 region contains or comprises an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of the selected VH CDR3. In some embodiments, the antibody may have a light chain variable region (VL) comprising CDR1, 2, and 3, wherein the CDR1 region comprises or consists of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of the selected VL CDR1; the CDR2 region comprises or consists of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of the selected VL CDR2; and the CDR3 region comprises or consists of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of the selected VL CDR3. The amino acid sequences of the selected VH CDR1, 2, and 3, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in Figure 3A (Kabat's CDR) and Figure 4A (Chothia's CDR).

[0174] In some embodiments, the antibody or antigen-binding fragments described herein may contain heavy chain variable domains containing one, two, or three CDRs of SEQ ID NO: 4, SEQ ID NO: 5, or SEQ ID NO: 6, which have 0, 1, or 2 amino acid insertions, deletions, or substitutions.

[0175] In some embodiments, the antibody or antigen-binding fragments described herein may contain heavy chain variable domains containing one, two, or three CDRs of SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9

[0176] In some embodiments, the antibody or antigen-binding fragments described herein may contain one, two, or three heavy chain variable domains of the CDRs of SEQ ID NO: 10 having 0, 1, or 2 amino acid insertions, deletions, or substitutions, SEQ ID NO: 11 having 0, 1, or 2 amino acid insertions, deletions, or substitutions, or SEQ ID NO: 12 having 0, 1, or 2 amino acid insertions, deletions, or substitutions.

[0177] In some embodiments, the antibody or antigen-binding fragments described herein may contain heavy chain variable domains containing one, two, or three CDRs of SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15

[0178] In some embodiments, the antibody or antigen-binding fragments described herein may contain heavy chain variable domains containing one, two, or three CDRs of SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18

[0179] In some embodiments, the antibody or antigen-binding fragments described herein may contain heavy chain variable domains containing one, two, or three CDRs of SEQ ID NO: 22, SEQ ID NO: 23, and SEQ ID NO: 24, which have 0, 1, or 2 amino acid insertions, deletions, or substitutions.

[0180] In some embodiments, the antibody or antigen-binding fragments described herein may contain heavy chain variable domains containing one, two, or three CDRs of SEQ ID NO: 25, SEQ ID NO: 26, and SEQ ID NO: 27, which have 0, 1, or 2 amino acid insertions, deletions, or substitutions.

[0181] In some embodiments, the antibody or antigen-binding fragments described herein may contain heavy chain variable domains containing one, two, or three CDRs of SEQ ID NO: 28, SEQ ID NO: 29, or SEQ ID NO: 30, all of which have 0, 1, or 2 amino acid insertions, deletions, or substitutions.

[0182] In some embodiments, the antibody or antigen-binding fragments described herein may contain heavy chain variable domains containing one, two, or three CDRs of SEQ ID NO: 31, SEQ ID NO: 32, SEQ ID NO: 33, or SEQ ID NO: 33, which have 0, 1, or 2 amino acid insertions, deletions, or substitutions.

[0183] In some embodiments, the antibody or antigen-binding fragments described herein may contain heavy chain variable domains containing one, two, or three CDRs of SEQ ID NO: 34, SEQ ID NO: 35, and SEQ ID NO: 36, which have 0, 1, or 2 amino acid insertions, deletions, or substitutions.

[0184] In some embodiments, the antibody or antigen-binding fragments described herein may contain one, two, or three light chain variable domains of the CDRs of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3

[0185] In some embodiments, the antibody or antigen-binding fragments described herein may contain one, two, or three light chain variable domains of the CDRs of SEQ ID NO: 19, SEQ ID NO: 20, and SEQ ID NO: 21, which have 0, 1, or 2 amino acid insertions, deletions, or substitutions.

[0186] Insertions, deletions, and substitutions can be located within the CDR sequence or at one or both ends of the CDR sequence. In some embodiments, the CDR is determined based on the Kabat numbering scheme. In some embodiments, the CDR is determined based on the Chothia numbering scheme. In some embodiments, the CDR is determined based on a combination of the Kabat and Chothia numbering schemes.

[0187] This disclosure also provides antibodies or antigen-binding fragments thereof that bind to HER3. The antibodies or antigen-binding fragments thereof contain a heavy chain variable region (VH) comprising or consisting of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to a selected VH sequence, and a light chain variable region (VL) comprising or consisting of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to a selected VL sequence. In some embodiments, the selected VH sequence is SEQ ID NO: 38, and the selected VL sequence is SEQ ID NO: 37. In some embodiments, the selected VH sequence is SEQ ID NO: 39, and the selected VL sequence is SEQ ID NO: 37. In some embodiments, the selected VH sequence is SEQ ID NO: 40, and the selected VL sequence is SEQ ID NO: 37. In some embodiments, the selected VH sequence is SEQ ID NO: 41, and the selected VL sequence is SEQ ID NO: 37. In some embodiments, the selected VH sequence is SEQ ID NO: 42, and the selected VL sequence is SEQ ID NO: 37.

[0188] This disclosure also provides antibodies or antigen-binding fragments thereof that are competitive with the antibodies described herein. In some embodiments, the antibodies or antigen-binding fragments may bind to the same epitopes as the antibodies described herein.

[0189] This disclosure also provides an antibody or an antigen-binding fragment thereof that cross-competes with any antibody or antigen-binding fragment described herein. Cross-competition assays are well known in the art and are described, for example, in Moore et al., “Antibody cross-competition analysis of the human immunodeficiency virus type 1 gp120 exterior envelope glycoprotein.” Journal of virology 70.3(1996):1863-1872, which is incorporated herein by reference in its entirety. In one embodiment, this disclosure also provides an antibody or an antigen-binding fragment thereof that binds to the same epitope or region as any antibody or antigen-binding fragment described herein. Epitope-binding assays are well known in the art and are described, for example, in Estep et al., “High throughput solution-based measurement of antibody-antigen affinity and epitope binning.” MAbs. Vol.5. No.2. Taylor & Francis, 2013, which is incorporated herein by reference in its entirety.

[0190] To measure the percentage of identity between two amino acid sequences or two nucleic acid sequences, the sequences are aligned for optimal comparison (for example, gaps may be introduced in one or both of the first and second amino acid or nucleic acid sequences to ensure optimal alignment for comparison, and non-homologous sequences may be ignored). Subsequently, amino acid residues or nucleotides at the corresponding amino acid or nucleotide positions are compared. If a position in the first sequence is occupied by the same amino acid residue or nucleotide at the corresponding position in the second sequence, the molecules are identical at that position. The percentage of identity between the two sequences is a function of the number of identical positions shared by the sequences, taking into account the number of gaps that need to be introduced to optimally align the two sequences and the length of each gap. For example, sequence comparison and measurement of the percentage of identity between two sequences can be performed using a Blossum62 scoring matrix with a gap penalty of 12, a gap extension penalty of 4, and a frameshift gap penalty of 5.

[0191] This disclosure also provides nucleic acids comprising polynucleotides encoding polypeptides containing an immunoglobulin heavy chain or an immunoglobulin light chain. The immunoglobulin heavy chain or immunoglobulin light chain comprises a CDR shown in Figure 3A or Figure 4A, or a sequence shown in Figure 5. When a polypeptide pairs with a corresponding polypeptide (e.g., a corresponding heavy chain variable region or a corresponding light chain variable region), the paired polypeptide binds to HER3 (e.g., human HER3).

[0192] Anti-HER3 antibodies and antigen-binding fragments may also be antibody variants (including derivatives and conjugates) of antibodies or antibody fragments, as well as multispecific (e.g., bispecific) antibodies or antibody fragments. Additional antibodies provided herein include polyclonal, monoclonal, multispecific (multimer, e.g., bispecific), human antibodies, chimeric antibodies (e.g., human-mouse chimeric), single-chain antibodies, intracellularly produced antibodies (i.e., intrabodies), and their antigen-binding fragments. Antibodies or their antigen-binding fragments may be of any type (e.g., IgG, IgE, IgM, IgD, IgA, and IgY), class (e.g., IgG1, IgG2, IgG3, IgG4, IgA1, and IgA2), or subclass. In some embodiments, the antibody or its antigen-binding fragment is an IgG antibody or its antigen-binding fragment.

[0193] Antibody fragments are suitable for use in the provided manner, insofar as they retain the desired affinity and specificity of the full-length antibody. Therefore, an antibody fragment that binds to HER3 retains its ability to bind to HER3. An Fv fragment is an antibody fragment containing a complete antigen recognition and binding site. This region consists of a dimer in which one heavy chain variable domain and one light chain variable domain are closely associated, which can essentially be covalent, for example, in scFv. In this configuration, the three CDRs of each variable domain interact to define the antigen-binding site on the surface of the VH-VL dimer. Together, the six CDRs, or subsets thereof, confer antigen-binding specificity to the antibody. However, even a single variable domain (or half of an Fv containing only three antigen-specific CDRs) can have the ability to recognize and bind to an antigen, though usually with lower affinity than the entire binding site.

[0194] In some embodiments, the antibodies or antigen-binding fragments described herein recognize endogenous HER3 or recombinant HER3. In some embodiments, the antibodies or antigen-binding fragments described herein recognize human HER3.

[0195] In some embodiments, the half-life of the antibodies or antigen-binding fragments thereof described herein in wild-type mice (e.g., C57BL / 6 mice) is at least 4 days, at least 5 days, at least 6 days, at least 7 days, at least 8 days, at least 9 days, at least 10 days, at least 11 days, at least 12 days, at least 13 days, at least 14 days, at least 15 days, at least 16 days, at least 17 days, or at least 18 days. In some embodiments, the half-life of the antibodies or antigen-binding fragments thereof described herein in HER3 gene humanized mice (e.g., hHER3 mice) is at least 1 day, at least 2 days, at least 3 days, at least 4 days, or at least 5 days, at least 6 days, at least 7 days, at least 8 days, at least 9 days, at least 10 days, at least 11 days, at least 12 days, at least 13 days, at least 14 days, at least 15 days, at least 16 days, at least 17 days, or at least 18 days. In some embodiments, the maximum concentration (Cmax) of the antibodies or antigen-binding fragments thereof described herein in HER3 gene humanized mice (e.g., hHER3 mice) is at least 50 μg / mL, at least 75 μg / mL, at least 100 μg / mL, at least 125 μg / mL, at least 150 μg / mL, at least 175 μg / mL, or at least 200 μg / mL. In some embodiments, the serum clearance rate (CL) of the antibodies or antigen-binding fragments thereof described herein in HER3 gene humanized mice (e.g., hHER3 mice) is at least 7.5 mL / day / kg, at least 10 mL / day / kg, at least 12.5 mL / day / kg, at least 15 mL / day / kg, at least 17.5 mL / day / kg, at least 20 mL / day / kg, at least 25 mL / day / kg, at least 30 mL / day / kg, at least 35 mL / day / kg, or at least 40 mL / day / kg.

[0196] In some embodiments, the clearance rate (CL) of the antibodies or antigen-binding fragments thereof described herein in wild-type mice (e.g., C57BL / 6 mice) is less than 7 mL / day / kg, less than 6 mL / day / kg, less than 5 mL / day / kg, or less than 4 mL / day / kg. In some embodiments, the clearance rate (CL) of the antibodies or antigen-binding fragments thereof described herein in HER3 gene humanized mice (e.g., hHER3 mice) is less than 15 mL / day / kg, less than 14 mL / day / kg, less than 13 mL / day / kg, or less than 12 mL / day / kg.

[0197] In some embodiments, the half-life of the antibodies or antigen-binding fragments thereof described herein (e.g., in FcRn gene humanized mice) is at least 6 days, at least 7 days, at least 8 days, at least 9 days, at least 10 days, at least 11 days, at least 12 days, at least 13 days, or at least 14 days. In some embodiments, the clearance rate (CL) of the antibodies or antigen-binding fragments thereof described herein (e.g., in FcRn gene humanized mice) is less than 16 mL / day / kg, less than 15 mL / day / kg, less than 14 mL / day / kg, less than 13 mL / day / kg, less than 12 mL / day / kg, less than 11 mL / day / kg, less than 10 mL / day / kg, less than 9 mL / day / kg, less than 8 mL / day / kg, or less than 7 mL / day / kg.

[0198] Anti-MET antibodies and antigen-binding fragments The present disclosure also provides antibodies and antigen-binding fragments thereof that specifically bind to MET (e.g., human MET). The antibodies and antigen-binding fragments described herein are capable of binding to MET. These antibodies can be agonists or antagonists. In some embodiments, these antibodies can block MET activity.

[0199] The present disclosure provides, for example, anti-MET antibodies 2F11 and 8E2, chimeric antibodies thereof, and human antibodies or humanized antibodies thereof.

[0200] CDR sequences for 2F11 and antibodies derived from 2F11 (e.g., human antibodies or humanized antibodies) include the heavy chain variable domain CDRs, sequence numbers 51-53, and the light chain variable domain CDRs, sequence numbers 1-3, as defined by Kabat numbering. CDRs can also be defined by the Chothia system. Under Chothia numbering, the heavy chain variable domain CDR sequences are shown in sequence numbers 57-59, and the light chain variable domain CDR sequences are shown in sequence numbers 19-21.

[0201] The CDR sequences of 8E2 and antibodies derived from 8E2 include the heavy chain variable domain CDRs, sequence numbers 54-56, and the light chain variable domain CDRs, sequence numbers 1-3, as defined by Kabat numbering. Under Chothia numbering, the heavy chain variable domain CDR sequences are shown in sequence numbers 60-62, and the light chain variable domain CDRs are shown in sequence numbers 19-21.

[0202] The CDR sequences of 8D9 and antibodies derived from 8D9 include the heavy chain variable domain CDRs, sequence numbers 69-71, and the light chain variable domain CDRs, sequence numbers 1-3, as defined by Kabat numbering. Under Chothia numbering, the heavy chain variable domain CDR sequences are shown in sequence numbers 75-77, and the light chain variable domain CDRs are shown in sequence numbers 19-21.

[0203] The CDR sequences of 8H10 and antibodies derived from 8H10 include the heavy chain variable domain CDRs, sequence numbers 72-74, and the light chain variable domain CDRs, sequence numbers 1-3, as defined by Kabat numbering. Under Chothia numbering, the heavy chain variable domain CDR sequences are shown in sequence numbers 78-80, and the light chain variable domain CDRs are shown in sequence numbers 19-21.

[0204] The amino acid sequence of the heavy chain variable region of the 2F11 antibody is shown in SEQ ID NO: 63. The amino acid sequence of the light chain variable region of the 2F11 antibody is shown in SEQ ID NO: 37.

[0205] The amino acid sequence of the heavy chain variable region of the 8E2 antibody is shown in SEQ ID NO: 64. The amino acid sequence of the light chain variable region of the 8E2 antibody is shown in SEQ ID NO: 37.

[0206] The amino acid sequence of the heavy chain variable region of the 8D9 antibody is shown in SEQ ID NO: 81. The amino acid sequence of the light chain variable region of the 8D9 antibody is shown in SEQ ID NO: 37.

[0207] The amino acid sequence of the heavy chain variable region of the 8H10 antibody is shown in SEQ ID NO: 82. The amino acid sequence of the light chain variable region of the 8H10 antibody is shown in SEQ ID NO: 37.

[0208] In some embodiments, the heavy chain variable region is at least 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to any one of sequence numbers 63, 64, 81, or 82. In some embodiments, the light chain variable region is at least 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to sequence number 37. The heavy chain variable region sequence can form a pair with a corresponding light chain variable region sequence, which together bind to MET.

[0209] In some embodiments, the variable region has a humanization percentage greater than 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or 95%. In some embodiments, the variable region is entirely human, derived from, for example, human heavy chain immunoglobulin loci (e.g., a combination of human IGHV, human IGHD, and human IGHJ genes) and / or human kappa chain immunoglobulin loci (e.g., a combination of human IGKV and human IGKJ genes).

[0210] Furthermore, in some embodiments, the antibodies or antigen-binding fragments described herein may also contain one, two, or three heavy chain variable region CDRs selected from the group consisting of SEQ ID NOs. 51-53, SEQ ID NOs. 54-56, SEQ ID NOs. 57-59, SEQ ID NOs. 60-62, SEQ ID NOs. 69-71, SEQ ID NOs. 72-74, SEQ ID NOs. 75-77, and SEQ ID NOs. 79-80, and / or one, two, or three light chain variable region CDRs selected from the group consisting of SEQ ID NOs. 1-3 and SEQ ID NOs. 19-21.

[0211] In some embodiments, the antibody may have a heavy chain variable region (VH) comprising complementarity-determining regions (CDRs) 1, 2, and 3, wherein the CDR1 region contains or comprises an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of the selected VH CDR1; the CDR2 region contains or comprises an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of the selected VH CDR2; and the CDR3 region contains or comprises an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of the selected VH CDR3. In some embodiments, the antibody may have a light chain variable region (VL) comprising CDR1, 2, and 3, wherein the CDR1 region comprises or consists of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of the selected VL CDR1; the CDR2 region comprises or consists of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of the selected VL CDR2; and the CDR3 region comprises or consists of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of the selected VL CDR3. The amino acid sequences of the selected VH CDR1, 2, and 3, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in Figure 3B (Kabat's CDR) and Figure 4B (Chothia's CDR).

[0212] In some embodiments, the antibody or antigen-binding fragments described herein may contain heavy chain variable domains containing one, two, or three CDRs of SEQ ID NO: 51, SEQ ID NO: 52, and SEQ ID NO: 53, which have 0, 1, or 2 amino acid insertions, deletions, or substitutions.

[0213] In some embodiments, the antibody or antigen-binding fragments described herein may contain heavy chain variable domains containing one, two, or three CDRs of SEQ ID NO: 54, SEQ ID NO: 55, and SEQ ID NO: 56, which have 0, 1, or 2 amino acid insertions, deletions, or substitutions.

[0214] In some embodiments, the antibody or antigen-binding fragments described herein may contain heavy chain variable domains containing one, two, or three CDRs of SEQ ID NO: 57, SEQ ID NO: 58, and SEQ ID NO: 59, which have 0, 1, or 2 amino acid insertions, deletions, or substitutions.

[0215] In some embodiments, the antibody or antigen-binding fragments described herein may contain heavy chain variable domains containing one, two, or three CDRs of SEQ ID NO: 60 having 0, 1, or 2 amino acid insertions, deletions, or substitutions, SEQ ID NO: 61 having 0, 1, or 2 amino acid insertions, deletions, or substitutions, or SEQ ID NO: 62 having 0, 1, or 2 amino acid insertions, deletions, or substitutions.

[0216] In some embodiments, the antibodies or antigen-binding fragments described herein can contain a light chain variable domain containing one, two, or three of the CDRs of SEQ ID NO: 1 having 0, 1, or 2 amino acid insertions, deletions, or substitutions, SEQ ID NO: 2 having 0, 1, or 2 amino acid insertions, deletions, or substitutions, and SEQ ID NO: 3 having 0, 1, or 2 amino acid insertions, deletions, or substitutions.

[0217] In some embodiments, the antibodies or antigen-binding fragments described herein can contain a light chain variable domain containing one, two, or three of the CDRs of SEQ ID NO: 19 having 0, 1, or 2 amino acid insertions, deletions, or substitutions, SEQ ID NO: 20 having 0, 1, or 2 amino acid insertions, deletions, or substitutions, and SEQ ID NO: 21 having 0, 1, or 2 amino acid insertions, deletions, or substitutions.

[0218] Insertions, deletions, and substitutions can be present within the CDR sequence or at one or both ends of the CDR sequence. In some embodiments, the CDRs are determined based on the Kabat numbering scheme. In some embodiments, the CDRs are determined based on the Chothia numbering scheme. In some embodiments, the CDRs are determined based on a combination of the Kabat and Chothia numbering schemes.

[0219] This disclosure also provides antibodies or antigen-binding fragments thereof that bind to MET. The antibodies or antigen-binding fragments thereof contain a heavy chain variable region (VH) comprising or consisting of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to a selected VH sequence, and a light chain variable region (VL) comprising or consisting of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to a selected VL sequence. In some embodiments, the selected VH sequence is SEQ ID NO: 63, and the selected VL sequence is SEQ ID NO: 37. In some embodiments, the selected VH sequence is SEQ ID NO: 64, and the selected VL sequence is SEQ ID NO: 37. In some embodiments, the selected VH sequence is SEQ ID NO: 81, and the selected VL sequence is SEQ ID NO: 37. In some embodiments, the selected VH sequence is SEQ ID NO: 82, and the selected VL sequence is SEQ ID NO: 37.

[0220] This disclosure also provides antibodies or antigen-binding fragments thereof that are competitive with the antibodies described herein. In some embodiments, the antibodies or antigen-binding fragments may bind to the same epitopes as the antibodies described herein.

[0221] This disclosure also provides an antibody or an antigen-binding fragment thereof that cross-competes with any antibody or antigen-binding fragment described herein. Cross-competition assays are well known in the art and are described, for example, in Moore et al., “Antibody cross-competition analysis of the human immunodeficiency virus type 1 gp120 exterior envelope glycoprotein.” Journal of virology 70.3(1996):1863-1872, which is incorporated herein by reference in its entirety. In one embodiment, this disclosure also provides an antibody or an antigen-binding fragment thereof that binds to the same epitope or region as any antibody or antigen-binding fragment described herein. Epitope-binding assays are well known in the art and are described, for example, in Estep et al., “High throughput solution-based measurement of antibody-antigen affinity and epitope binning.” MAbs. Vol.5. No.2. Taylor & Francis, 2013, which is incorporated herein by reference in its entirety.

[0222] This disclosure also provides nucleic acids comprising polynucleotides encoding polypeptides containing immunoglobulin heavy chains or immunoglobulin light chains. The immunoglobulin heavy chain or immunoglobulin light chain comprises a CDR shown in Figure 3B or Figure 4B, or a sequence shown in Figure 5. When a polypeptide forms a pair with a corresponding polypeptide (e.g., a corresponding heavy chain variable region or a corresponding light chain variable region), the paired polypeptide binds to MET (e.g., human MET).

[0223] Anti-MET antibodies and antigen-binding fragments may also be antibody variants (including derivatives and conjugates) of antibodies or antibody fragments, as well as multispecific (e.g., bispecific) antibodies or antibody fragments. Additional antibodies provided herein include polyclonal, monoclonal, multispecific (multimer, e.g., bispecific), human antibodies, chimeric antibodies (e.g., human-mouse chimeric), single-chain antibodies, intracellularly produced antibodies (i.e., intrabodies), and their antigen-binding fragments. Antibodies or their antigen-binding fragments may be of any type (e.g., IgG, IgE, IgM, IgD, IgA, and IgY), class (e.g., IgG1, IgG2, IgG3, IgG4, IgA1, and IgA2), or subclass. In some embodiments, the antibody or its antigen-binding fragment is an IgG antibody or its antigen-binding fragment.

[0224] Antibody fragments are suitable for use in the provided manner, insofar as they retain the desired affinity and specificity of the full-length antibody. Therefore, an antibody fragment that binds to MET retains its ability to bind to MET. An Fv fragment is an antibody fragment containing a complete antigen recognition and binding site. This region consists of a dimer in which one heavy chain variable domain and one light chain variable domain are closely associated, which can essentially be covalent, for example, in scFv. In this configuration, the three CDRs of each variable domain interact to define the antigen-binding site on the surface of the VH-VL dimer. Together, the six CDRs, or subsets thereof, confer antigen-binding specificity to the antibody. However, even a single variable domain (or half of an Fv containing only three antigen-specific CDRs) can have the ability to recognize and bind to an antigen, though usually with lower affinity than the entire binding site.

[0225] In some embodiments, the antibodies or antigen-binding fragments described herein recognize endogenous MET or recombinant MET. In some embodiments, the antibodies or antigen-binding fragments described herein recognize human MET.

[0226] Antibody and antigen-binding fragments This disclosure provides anti-HER3 antibodies and their antigen-binding fragments (including anti-HER3 multispecific antibodies and their antigen-binding fragments, e.g., anti-HER3 / MET bispecific antibodies and their antigen-binding fragments). This disclosure also provides anti-MET antibodies and their antigen-binding fragments (including anti-MET multispecific antibodies and their antigen-binding fragments, e.g., anti-HER3 / MET bispecific antibodies and their antigen-binding fragments).

[0227] Generally, antibodies (also called immunoglobulins) consist of two classes of polypeptide chains: a light chain and a heavy chain. Antibodies in this disclosure, in principle, can be intact four-immunoglobulin chain antibodies containing two heavy chains and two light chains. The heavy chains of an antibody can be any isotype, including IgM, IgG, IgE, IgA, or IgD, or a subisotype, including IgG1, IgG2, IgG2a, IgG2b, IgG3, IgG4, IgE1, IgE2, etc. The light chains can be κ-light chains or λ-light chains. An antibody may contain two identical copies of light chains and two identical copies of heavy chains. Each heavy chain, containing one variable domain (or variable region, VH) and multiple constant domains (or constant regions), binds to each other via disulfide bonds within its constant domains, forming the "stem" of the antibody. Each light chain, containing one variable domain (or variable region, VL) and one constant domain (or constant region), is bonded to a heavy chain via a disulfide bond. The variable region of each light chain is aligned with the variable region of the heavy chain to which it is bonded. The variable regions of both the light and heavy chains contain three hypervariable regions sandwiched between more conserved framework regions (FRs).

[0228] The hypervariable region, known as the complementarity-determining region (CDR), forms a loop containing the antibody's antigen-binding surface. The four framework regions are largely adapted to the β-sheet structure, and the CDRs form linked loops, sometimes even forming part of the β-sheet structure. The CDRs of each chain are held in close proximity to the framework regions and, together with the CDRs of other chains, contribute to the formation of the antigen-binding region.

[0229] Methods for identifying the CDR region of an antibody by analyzing its amino acid sequence are well-known, and several definitions of CDRs are commonly used. Kabat's definition is based on sequence variability, while Chothia's definition is based on the location of the structural loop region. These methods and definitions are, for example, found in Martin, “Protein sequence and structure analysis of antibody variable domains,” Antibody Engineering, Springer Berlin Heidelberg, 2001. 422-439, Abhinandan, et al. “Analysis and improvements to Kabat and structurally correct numbering of antibody variable domains,” Molecular Immunology 45.14(2008):3832-3839, Wu, T. and Kabat, EA(1970) J. Exp. Med. 132:211-250, Martin et al., Methods Enzymol. 203:121-53(1991), Morea et al., Biophys Chem. 68(1-3):9-16(Oct. 1997), Morea et al., J Mol Biol. 275(2):269-94(Jan. 1998), Chothia This is described in et al., Nature 342(6252):877-83 (Dec. 1989), and Ponomarenko and Bourne, BMC Structural Biology 7:64 (2007), the entirety of each of these works is incorporated herein by reference.

[0230] CDRs are important for recognizing the epitopes of antigens. As used herein, an “epitope” is the smallest portion of a target molecule that can be specifically bound by the antigen-binding domain of an antibody. The minimum size of an epitope can be about 3, 4, 5, 6, or 7 amino acids, but these amino acids do not need to be in a continuous linear sequence of the primary structure of the antigen, as epitopes can depend on the three-dimensional structure of the antigen based on the secondary and tertiary structures of the antigen.

[0231] In some embodiments, the antibody is an intact immunoglobulin molecule (e.g., IgG1, IgG2a, IgG2b, IgG3, IgM, IgD, IgE, IgA). The IgG subclasses (IgG1, IgG2, IgG3, and IgG4) are highly conserved, differing in their constant regions, particularly the hinge and upper CH2 domain. The sequences and differences of IgG subclasses are well known in the art, for example, in Vidarsson, et al., “IgG subclasses and allotypes: from structure to effector functions.” Frontiers in immunology 5 (2014); Irani, et al., “Molecular properties of human IgG subclasses and their implications for designing therapeutic monoclonal antibodies against infectious diseases.” Molecular immunology 67.2 (2015):171-182; and Shakib, Farouk, ed. The human IgG subclasses: molecular analysis of structure, function and regulation. Elsevier, 2016, each of which is incorporated herein by reference.

[0232] Antibodies can also be immunoglobulin molecules derived from any species (e.g., humans, rodents, mice, camelids). Antibodies disclosed herein include, but are not limited to, polyclonal, monoclonal, monospecific, multispecific antibodies, and chimeric antibodies containing an immunoglobulin-binding domain fused to another polypeptide. The terms “antigen-binding domain” or “antigen-binding fragment” refer to any portion of an antibody that retains the specific binding activity of an intact antibody, i.e., any portion of an antibody that is specifically capable of binding to an epitope on the target molecule of an intact antibody. This includes, for example, Fab, Fab', F(ab')2, and variants of these fragments. Thus, in some embodiments, an antibody or its antigen-binding fragment may be any polypeptide containing, for example, scFv, Fv, Fd, dAb, bispecific antibodies, bispecific scFv, diabodies, linear antibodies, single-chain antibody molecules, multispecific antibodies formed from antibody fragments, and a binding domain that is an antibody-binding domain, or a binding domain homologous thereto. Non-limiting examples of antigen-binding domains include, for example, the heavy and / or light chain CDRs of an intact antibody, the heavy and / or light chain variable regions of an intact antibody, the full-length heavy or light chain of an intact antibody, or individual CDRs derived from either the heavy or light chain of an intact antibody.

[0233] In some embodiments, antigen-binding fragments can form part of a chimeric antigen receptor (CAR). In some embodiments, the chimeric antigen receptor is a fusion of single-stranded variable fragments (scFv) described herein, fused to the CD3ζ transmembrane and endodomains. In some embodiments, the chimeric antigen receptor also includes intracellular signaling domains derived from various costimulatory protein receptors (e.g., CD28, 41BB, ICOS). In some embodiments, the chimeric antigen receptor includes multiple signaling domains, e.g., CD3z-CD28-41BB, or CD3z-CD28-OX40, for increased potency. Thus, in one aspect, the disclosure further provides cells (e.g., T cells) expressing the chimeric antigen receptor described herein.

[0234] In some embodiments, the scFv has one heavy chain variable domain and one light chain variable domain. In some embodiments, the scFv has two heavy chain variable domains and two light chain variable domains.

[0235] In some embodiments, a bispecific antibody targeting HER3 and an additional antigen (e.g., EGFR) can be generated using the antibody or antigen-binding fragment sequence described herein (e.g., CDR or VH / VL sequence).

[0236] A single-stranded Fv (scFv) or antibody fragment contains the VH and VL domains (or regions) of the antibody, and these domains are located within a single polypeptide chain. Generally, scFv polypeptides further contain a polypeptide linker between the VH and VL domains, which allows the scFv to form a desirable structure for antigen binding.

[0237] The Fab fragment contains variable and constant domains of the light chain, as well as a variable domain and a first constant domain (CH1) of the heavy chain. The F(ab')2 antibody fragment contains a pair of Fab fragments, generally commonally linked near the carboxyl terminus by a hinge cysteine ​​between them. Other chemical linkages of antibody fragments are well known in the art.

[0238] A diabody is a small antibody fragment containing two antigen-binding sites, and this fragment contains VH (VH and VL) attached to VL within the same polypeptide chain. By using a linker that is too short to allow pairing between two domains on the same chain, the domains can be paired with complementary domains on another chain, thereby generating two antigen-binding sites.

[0239] Linear antibodies contain a pair of tandem Fd segments (VH-CH1-VH-CH1) that, together with a complementary light chain polypeptide, form a pair of antigen-binding regions. Linear antibodies may be bispecific or monospecific.

[0240] A single-arm antibody may have a heavy chain and a light chain, as well as a heavy chain fragment containing the CH2 and CH3 domains of IgG. In some embodiments, a single-arm antibody is an antibody having only one of the two antigen-binding arms in a typical antibody. In some embodiments, a single-arm antibody includes an antigen-binding arm (e.g., VH+CH1 and VL+CL) and Fc.

[0241] The antibodies and antibody fragments of this disclosure can be modified within the Fc region to provide a desired effector function or serum half-life. In some embodiments, the Fc region can be modified to silence or reduce complement-dependent cell injury (CDC) or antibody-dependent cell injury (ADCC). In some embodiments, the Fc region can be modified to increase complement-dependent cell injury (CDC) or antibody-dependent cell injury (ADCC).

[0242] Antibody multimerization can be achieved by spontaneous aggregation of antibodies or by chemical or recombinant conjugation techniques known in the art. For example, a certain percentage of purified antibody preparations (e.g., one purified IgG molecule) spontaneously form protein aggregates containing antibody homodimers and other higher-order antibody multimers.

[0243] Alternatively, antibody homodimers can be formed by chemical bonding techniques well known in the art. For example, antibody polymers can be formed using heterobifunctional crosslinking agents, including but not limited to SMCC (4-(maleimidomethyl)cyclohexane-1-carboxylic acid succinimidyl) and SATA (S-acetylthioacetate N-succinimidyl). Exemplary procedures for forming antibody homodimers are described in Ghetie et al. (Proc. Natl. Acad. Sci. USA 94:7509-7514, 1997). Antibody homodimers can be converted to Fab'2 homodimers by pepsin digestion. Another method for forming antibody homodimers is to use the autophilic T15 peptide, as described in Zhao et al. (J. Immunol. 25:396-404, 2002).

[0244] In some embodiments, multispecific antibodies are bispecific antibodies. Bispecific antibodies can be produced by recombining the interface between a pair of antibody molecules to maximize the proportion of heterodimers recovered from recombinant cell culture. For example, the interface may contain at least a portion of the CH3 domain of the antibody's constant domain. In this method, one or more smaller amino acid side chains from the interface of the first antibody molecule are replaced with larger side chains (e.g., tyrosine or tryptophan). By replacing the larger amino acid side chains with smaller ones (e.g., alanine or threonine), a compensatory "cavity" of the same or similar size as the larger side chain is created at the interface of the second antibody molecule. This provides a mechanism to increase the yield of heterodimers compared to other unwanted end products such as homodimers. This method is described, for example, in WO 96 / 27011, which is incorporated in its entirety by reference.

[0245] Examples of bispecific antibodies include crosslinked or "heterocomplex" antibodies. For example, one antibody in a heterocomplex can be coupled to avidin and the other to biotin. Heterocomplex antibodies can also be produced using any convenient crosslinking method. Suitable crosslinking agents and techniques are well known in the art and are disclosed in U.S. Patent No. 4,676,980, which is incorporated herein by reference in its entirety.

[0246] Methods for generating bispecific antibodies from antibody fragments are also well known in the art. For example, bispecific antibodies can be prepared using chemical bonding. Brennan et al. (Science 229:81, 1985) describe a procedure in which an intact antibody is cleaved by proteolysis to generate F(ab')2 fragments. These fragments are reduced in the presence of sodium arsenite, a dithiol complexing agent, to stabilize adjacent dithiols and prevent intermolecular disulfide formation. The resulting Fab' fragments are then converted to thionitrobenzoate (TNB) derivatives. One of the Fab'TNB derivatives is then reconverted to a Fab'thiol by reduction with mercaptoethylamine and mixed with an equimolar amount of another Fab'TNB derivative to form a bispecific antibody.

[0247] Any antibody or antigen-binding fragment described herein can be conjugated with a stabilizing molecule (e.g., a molecule that increases the half-life of the antibody or its antigen-binding fragment in a subject or in solution). Non-limiting examples of stabilizing molecules include polymers (e.g., polyethylene glycol) or proteins (e.g., serum albumin such as human serum albumin). Conjugation with a stabilizing molecule can increase the half-life of the antibody or antigen-binding fragment or extend its biological activity, either in vitro (e.g., in tissue culture medium or when stored as a pharmaceutical composition) or in vivo (e.g., in humans).

[0248] In some embodiments, the antibodies or antigen-binding fragments described herein can be conjugated with a therapeutic agent. The antibody-drug conjugate, comprising an antibody or its antigen-binding fragment, can be covalently or noncovalently bound to the therapeutic agent. In some embodiments, the therapeutic agent is a cytotoxic or cell proliferation inhibitor (e.g., cytochalasin B, gramicidin D, ethidium bromide, emetine, mitomycin, etoposide, teniposide, vincristine, vinblastine, colchicine, doxorubicin, daunorubicin, dihydroxyanthracene, maytansinoids (such as DM-1 and DM-4), zione, mitoxantrone, mitramycin, actinomycin D, 1-dehydrotestosterone, glucocorticoids, procaine, tetracaine, lidocaine, propranolol, puromycin, epirubicin, and cyclophosphamide, as well as analogues).

[0249] Multispecific antibodies and antigen-binding fragments This disclosure provides multispecific (e.g., bispecific) antibodies and antigen-binding fragments thereof that specifically bind to HER3 (e.g., human HER3). In one embodiment, this disclosure provides an anti-HER3 multispecific (e.g., bispecific) antibody or antigen-binding fragment thereof, comprising a first antigen-binding domain that specifically binds to HER3 and a second antigen-binding domain that specifically binds to a different antigen.

[0250] In one embodiment, the disclosure provides an anti-HER3 multispecific (e.g., bispecific) antibody or antigen-binding fragment thereof, comprising a first antigen-binding domain that specifically binds to a first epitope of HER3 and a second antigen-binding domain that specifically binds to a second epitope of HER3. In some embodiments, the first epitope is different from the second epitope.

[0251] In some embodiments, the first antigen-binding domain specifically binds to HER3, and the second antigen-binding domain specifically binds to MET.

[0252] In some embodiments, the first antigen-binding domain comprises a first heavy chain variable region (VH1) and a first light chain variable region (VL1), and the second antigen-binding domain comprises a second heavy chain variable region (VH2) and a second light chain variable region (VL2).

[0253] In some embodiments, the first heavy chain variable region (VH1) includes complementarity-determining regions (CDRs) 1, 2, and 3, wherein the VH1 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR1, the VH1 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR2, and the VH1 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR3, and The first light chain variable region (VL1) described above includes CDR1, 2, and 3, wherein the VL1 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR1, the VL1 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR2, and the VL1 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR3. The amino acid sequences of the selected VH1 CDR1, 2, and 3, and the amino acid sequences of the selected VL1 CDR1, 2, and 3, are one of the following: (1) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 4 to 6, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (2) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 7 to 9, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (3) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 10 to 12, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (4) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 13 to 15, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (5) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 16-18, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1-3, respectively. (6) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 22-24, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (7) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 25-27, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (8) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 28-30, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (9) The amino acid sequences of the above-selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 31-33, respectively, and the amino acid sequences of the above-selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively, and (10) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 34 to 36, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0254] In some embodiments, the second heavy chain variable region (VH2) comprises CDR1, 2, and 3, wherein the VH2 CDR1 region comprises an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR1, the VH2 CDR2 region comprises an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR2, and the VH2 CDR3 region comprises an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR3, and The second light chain variable region (VL2) described above includes CDR1, 2, and 3, wherein the VL2 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR1, the VL2 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR2, and the VL2 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR3. The amino acid sequences of the selected VH2 CDR1, 2, and 3, and the amino acid sequences of the selected VL2 CDR1, 2, and 3, are one of the following: (1) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 4 to 6, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (2) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 7 to 9, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (3) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 10 to 12, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (4) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 13 to 15, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (5) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 16-18, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1-3, respectively. (6) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 22-24, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (7) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 25-27, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (8) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 28-30, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (9) The amino acid sequences of the above-selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 31-33, respectively, and the amino acid sequences of the above-selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively, and (10) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 34 to 36, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0255] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0256] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 31-33, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 19-21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 25-27, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 19-21, respectively.

[0257] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 16-18, the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1-3, the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 7-9, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1-3.

[0258] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 34 to 36, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 25 to 27, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0259] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0260] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 22 to 24, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 25 to 27, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0261] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 41, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 39, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37.

[0262] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 42, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 39, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37.

[0263] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 38, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 39, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 37.

[0264] In some embodiments, VH1 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VH sequence, and VL1 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, and the selected VL sequence is sequence number 37, (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

[0265] In some embodiments, the VH2 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VH sequence, and the VL2 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, and the selected VL sequence is sequence number 37, (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

[0266] In some embodiments, VH1 includes VH1 CDR1, VH1 CDR2, and VH1 CDR3 which are identical to VH CDR1, VH CDR2, and VH CDR3 of the selected VH sequence, and VL1 includes VL1 CDR1, VL1 CDR2, and VL1 CDR3 which are identical to VL CDR1, VL CDR2, and VL CDR3 of the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, and the selected VL sequence is sequence number 37, (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

[0267] In some embodiments, VH2 includes VH2 CDR1, VH2 CDR2, and VH2 CDR3 which are identical to VH CDR1, VH CDR2, and VH CDR3 of the selected VH sequence, and VL2 includes VL2 CDR1, VL2 CDR2, and VL2 CDR3 which are identical to VL CDR1, VL CDR2, and VL CDR3 of the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, and the selected VL sequence is sequence number 37, (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

[0268] In some embodiments, the first antigen-binding domain specifically binds to human HER3, mouse HER3, monkey HER3, or canine HER3, and / or the second antigen-binding domain specifically binds to human HER3, mouse HER3, monkey HER3, or canine HER3.

[0269] In some embodiments, the first antigen-binding domain is a human antigen-binding domain or a humanized antigen-binding domain, and / or the second antigen-binding domain is a human antigen-binding domain or a humanized antigen-binding domain.

[0270] In some embodiments, the first antigen-binding domain is a single-stranded variable fragment (scFV), and / or the second antigen-binding domain is an scFv.

[0271] In some embodiments, the first light chain variable region and the second light chain variable region are the same.

[0272] In some embodiments, knobs-into-holes mutations were introduced into the Fc region of bispecific antibodies to reduce the possibility of mispairing between the two heavy chains. Exemplary bispecific antibodies obtained include 1C5-1B2, 1D6-1B2, 3E1-1B2, 3G6-1B2, 1D6-1C5, 3E1-1C5, 3G6-1C5, 3E1-1D6, 3G6-1D6, 3G6-3E1, 2F11-3E1, 2F11-3G6, 2F11-1B2, 2F11-1B2, and 2F11-1C5 (Figure 9). The sequence of the human IgG1 constant region with the knob mutation is shown in SEQ ID NO: 49, and the sequence of the human IgG1 constant region with the hole mutation is shown in SEQ ID NO: 50.

[0273] In some embodiments, an anti-HER3 antibody, a bispecific antibody, or an antibody fragment thereof includes a combination of anti-HER3 antigen-binding domains as shown in Figure 9. In some embodiments, the first anti-HER3 antigen-binding domain includes a CDR of the anti-HER3 antibody, as shown in the first row of Figure 9. In some embodiments, the second anti-HER3 antigen-binding domain includes a CDR of the anti-HER3 antibody, as shown in the first column of Figure 9. In some embodiments, the first anti-HER3 antigen-binding domain includes the VH and VL of the anti-HER3 antibody, as shown in the first row of Figure 9. In some embodiments, the second anti-HER3 antigen-binding domain includes the VH and VL of the anti-HER3 antibody, as shown in the first column of Figure 9. For example, 3E1-1C5 refers to a bispecific anti-HER3 antibody containing a first anti-HER3 antigen-binding domain derived from 3E1 and a second anti-HER3 antigen-binding domain derived from 1C5. In some embodiments, the first anti-HER3 antigen-binding domain includes a CDR of 3E1. In some embodiments, the second anti-HER3 antigen-binding domain includes a 1C5 CDR. In some embodiments, the first anti-HER3 antigen-binding domain includes 3E1 VH and VL. In some embodiments, the second anti-HER3 antigen-binding domain includes 1C5 VH and VL.

[0274] In some embodiments, 3E1-1C5 includes a knob mutation in the heavy chain constant region of 3E1 and a hole mutation in the heavy chain constant region of 1C5. In some embodiments, 3G6-1C5 includes a knob mutation in the heavy chain constant region of 3G6 and a hole mutation in the heavy chain constant region of 1C5. In some embodiments, 1B2-1C5 includes a knob mutation in the heavy chain constant region of 1B2 and a hole mutation in the heavy chain constant region of 1C5.

[0275] Anti-HER3 / MET bispecific antibody and antigen-binding fragment In some embodiments, as examples of anti-HER3 multispecific antibodies and antigen-binding fragments, this disclosure provides anti-HER3 / MET bispecific antibodies and antigen-binding fragments.

[0276] In some embodiments, the anti-HER3 / MET bispecific antibody or antigen-binding domain described herein has a common light chain. In some embodiments, the anti-HER3 / MET bispecific antibody or antigen-binding domain has an anti-HER3 antigen-binding domain (e.g., 1B2, 1C5, 1D6, 3E1, or 3G6) and an anti-MET antigen-binding domain (e.g., 2F11, 8E2, 8D9, or 8H10). In some embodiments, the anti-HER3 / MET bispecific antibody or antigen-binding domain has a heavy chain variable region targeting HER3 (e.g., any of the HER3-targeting VHs described herein), a heavy chain variable region targeting MET (e.g., any of the MET-targeting VHs described herein), and two identical common light chain variable regions.

[0277] In some embodiments, an anti-HER3 / MET bispecific antibody or its antigen-binding fragment comprises a heavy chain variable region (VH) including complementarity-determining regions (CDRs) 1, 2, and 3, wherein the CDR1 region contains or consists of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of a selected VH CDR1; the CDR2 region contains or consists of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of a selected VH CDR2; and the CDR3 region contains or consists of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of a selected VH CDR3; and a light chain variable region (VL) including CDRs 1, 2, and 3, wherein the CDR1 region is a selected VL The CDR2 region may contain or consist of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of CDR1, the CDR3 region may contain or consist of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of the selected VL CDR2, and the CDR3 region may contain or consist of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the amino acid sequence of the selected VL CDR3. The amino acid sequences of the selected VH CDR1, 2, and 3, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in Figures 3A-3B (Kabat's CDR) and Figures 4A-4B (Chothia's CDR).

[0278] In some embodiments, the anti-HER3 / MET bispecific antibody or its antigen-binding fragment contains a heavy chain variable region (VH) comprising or consisting of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the selected VH sequence, and a light chain variable region (VL) comprising or consisting of an amino acid sequence that is at least 80%, 85%, 90%, or 95% identical to the selected VL sequence. In some embodiments, the selected VH sequence and the selected VL sequence are shown in Figure 5.

[0279] In some embodiments, the anti-HER3 / MET bispecific antibody or antigen-binding domain has one of the following combinations: (1) a heavy chain variable region targeting HER3, and (2) a heavy chain variable region targeting MET, as shown in Figure 9. In some embodiments, the anti-HER3 / MET bispecific antibody or antigen-binding domain has one of the following combinations: (1) a heavy chain variable region targeting HER3, and (2) a heavy chain variable region targeting MET: 2F11-3E1, 2F11-3G6, 2F11-1B2, 2F11-1C5, 8E2-1B2, 8E2-1C5, 8E2-3E1, 8E2-3G6, 3E1-8D9, 1B2-8D9, 1C5-8D9, 3E1-8H10, 1B2-8H10, or 1C5-8H10.

[0280] In some embodiments, the first antigen-binding domain comprises a first heavy chain variable region (VH1) and a first light chain variable region (VL1), and the second antigen-binding domain comprises a second heavy chain variable region (VH2) and a second light chain variable region (VL2).

[0281] In some embodiments, the first heavy chain variable region (VH1) includes complementarity-determining regions (CDRs) 1, 2, and 3, wherein the VH1 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR1, the VH1 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR2, and the VH1 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR3, and The first light chain variable region (VL1) described above includes CDR1, 2, and 3, wherein the VL1 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR1, the VL1 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR2, and the VL1 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR3. The amino acid sequences of the selected VH1 CDR1, 2, and 3, and the amino acid sequences of the selected VL1 CDR1, 2, and 3, are one of the following: (1) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 4 to 6, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (2) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 7 to 9, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (3) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 10 to 12, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (4) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 13 to 15, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (5) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 16-18, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 1-3, respectively. (6) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 22-24, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (7) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 25-27, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (8) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 28-30, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (9) The amino acid sequences of the above-selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 31-33, respectively, and the amino acid sequences of the above-selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively, and (10) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 34 to 36, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0282] In some embodiments, the second heavy chain variable region (VH2) comprises CDR1, 2, and 3, wherein the VH2 CDR1 region comprises an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR1, the VH2 CDR2 region comprises an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR2, and the VH2 CDR3 region comprises an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR3, and The second light chain variable region (VL2) described above includes CDR1, 2, and 3, wherein the VL2 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR1, the VL2 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR2, and the VL2 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR3. The amino acid sequences of the selected VH2 CDR1, 2, and 3, and the amino acid sequences of the selected VL2 CDR1, 2, and 3, are one of the following: (1) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 51 to 53, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (2) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 54 to 56, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (3) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 57 to 59, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively. (4) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 60-62, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively. (5) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 69 to 71, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (6) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 72-74, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1-3, respectively. (7) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 75-77, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19-21, respectively, and (8) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 78 to 80, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0283] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51 to 53, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0284] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 22 to 24, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 57 to 59, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0285] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51 to 53, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0286] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 25 to 27, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 57 to 59, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0287] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 10 to 12, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51 to 53, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0288] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 28 to 30, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 57 to 59, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0289] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51 to 53, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0290] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 31 to 33, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 57 to 59, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0291] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 16-18, the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1-3, the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51-53, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1-3.

[0292] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 34 to 36, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 57 to 59, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0293] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54 to 56, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0294] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 22 to 24, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 60 to 62, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0295] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54 to 56, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0296] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 25 to 27, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 60 to 62, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0297] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 10 to 12, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54 to 56, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0298] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 28 to 30, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 60 to 62, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0299] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54 to 56, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0300] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 31-33, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 19-21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 60-62, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 19-21, respectively.

[0301] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 16-18, the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1-3, the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54-56, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1-3.

[0302] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 34 to 36, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 60 to 62, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

[0303] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 69 to 71, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0304] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 69 to 71, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0305] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 69 to 71, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0306] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 72 to 74, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0307] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 72 to 74, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0308] In some embodiments, the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 72 to 74, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

[0309] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 38, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 63, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 37.

[0310] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 39, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 63, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37.

[0311] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 40, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 63, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37.

[0312] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 41, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 63, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37.

[0313] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 42, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 63, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37.

[0314] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 38, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 64, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 37.

[0315] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 39, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 64, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37.

[0316] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 40, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 64, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37.

[0317] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 41, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 64, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37.

[0318] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 42, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 64, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37.

[0319] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 38, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 81, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 37.

[0320] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 39, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 81, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37.

[0321] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 41, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 81, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37.

[0322] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 38, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 82, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to SEQ ID NO: 37.

[0323] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 39, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 82, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37.

[0324] In some embodiments, the first heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 41, the first light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37, the second heavy chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 82, and the second light chain variable region includes a sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to sequence number 37.

[0325] In some embodiments, VH1 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VH sequence, and VL1 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, and the selected VL sequence is sequence number 37, (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

[0326] In some embodiments, the VH2 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VH sequence, and the VL2 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 63, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 64, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 81, and the selected VL sequence is sequence number 37, (4) The selected VH sequence is sequence number 82, and the selected VL sequence is sequence number 37.

[0327] In some embodiments, VH1 includes VH1 CDR1, VH1 CDR2, and VH1 CDR3 which are identical to VH CDR1, VH CDR2, and VH CDR3 of the selected VH sequence, and VL1 includes VL1 CDR1, VL1 CDR2, and VL1 CDR3 which are identical to VL CDR1, VL CDR2, and VL CDR3 of the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, and the selected VL sequence is sequence number 37, (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

[0328] In some embodiments, VH2 includes VH2 CDR1, VH2 CDR2, and VH2 CDR3 which are identical to VH CDR1, VH CDR2, and VH CDR3 of the selected VH sequence, and VL2 includes VL2 CDR1, VL2 CDR2, and VL2 CDR3 which are identical to VL CDR1, VL CDR2, and VL CDR3 of the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 63, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 64, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 81, and the selected VL sequence is sequence number 37, (4) The selected VH sequence is sequence number 82, and the selected VL sequence is sequence number 37.

[0329] In some embodiments, the first antigen-binding domain specifically binds to human HER3, mouse HER3, monkey HER3, or canine HER3, and / or the second antigen-binding domain specifically binds to human MET, mouse MET, monkey MET, or canine MET.

[0330] In some embodiments, the first antigen-binding domain is a human antigen-binding domain or a humanized antigen-binding domain, and / or the second antigen-binding domain is a human antigen-binding domain or a humanized antigen-binding domain.

[0331] In some embodiments, the first antigen-binding domain is a single-stranded variable fragment (scFV), and / or the second antigen-binding domain is an scFv.

[0332] In some embodiments, the first light chain variable region and the second light chain variable region are the same.

[0333] Antibody-drug conjugates (ADCs) In some embodiments, the antibodies, antigen-binding fragments thereof, or bispecific antibodies described herein can be optionally conjugated with a therapeutic agent using a linker to form an antibody-drug conjugate. The antibody-drug conjugate, comprising the antibody or antigen-binding fragment thereof, can be covalently or noncovalently bound to the therapeutic agent. In some embodiments, the therapeutic agent is a cytotoxic or cell proliferation inhibitor (e.g., monomethyl auristatin E, monomethyl auristatin F, camptothecin, cytochalasin B, gramicidin D, ethidium bromide, emetine, mitomycin, etoposide, teniposide, vincristine, vinblastine, colchicine, doxorubicin, daunorubicin, dihydroxyanthracene, meitansinoids (such as DM-1 and DM-4), zione, mitoxantrone, mitramycin, actinomycin D, 1-dehydrotestosterone, glucocorticoids, procaine, tetracaine, lidocaine, propranolol, puromycin, epirubicin, and cyclophosphamide, as well as its analogues). In some embodiments, the therapeutic agent is MMAE or MMAF.

[0334] The definitions of specific functional groups and chemical terms are described in detail below. For the purposes of this invention, chemical elements are identified based on the Periodic Table, CAS edition, Handbook of Chemistry and Physics, 75th edition, inside cover, and specific functional groups are defined as generally described herein. Furthermore, general principles of organic chemistry, as well as specific functional groups and reactivity, are described in Organic Chemistry, Thomas Sorrell, University Science Books, Sausalito, 1999; Smith and March, March's Advanced Organic Chemistry, 5th Edition, John Wiley & Sons, Inc., New York, 2001; Larock, Comprehensive Organic Transformations, VCH Publishers, Inc., New York, 1989; and Carruthers, Some Modern Methods of Organic Synthesis, 3rd Edition, Cambridge University Press, Cambridge, 1987.

[0335] All ranges cited herein are inclusive unless explicitly stated otherwise. When a range of values ​​is listed, it is intended to include each value and subrange within that range. For example, "C1-6" is intended to include C1, C2, C3, C4, C5, C6, C1-6, C1-5, C1-4, C1-3, C1-2, C2-6, C2-5, C2-4, C2-3, C3-6, C3-5, C3-4, C4-6, C4-5, and C5-6.

[0336] Any compound or any formula describing and explaining the compounds of this disclosure may have one or more chiral centers. The present invention encompasses all stereoisomers of the compounds herein or any formula describing and explaining the compounds of the present invention. All chiral centers present in any compound or any formula describing and explaining the compounds of the present invention may independently have (R) or (S) configurations. When the bond to the chiral carbon is depicted as a straight line in the structural formula, or when the compound name is written without a (R) or (S) chiral designation for the chiral carbon, it is understood that both the (R) and (S) configurations of each chiral carbon, and therefore each enantiomer or diastereomer and mixtures thereof, are encompassed in the formula or name.

[0337] This disclosure includes all possible enantiomers and diastereomers, as well as mixtures of two or more stereoisomers, e.g., mixtures of enantiomers and / or diastereomers in any proportion. Thus, enantiomers are subject to this disclosure in the form of enantiomerically pure forms, both levorotatory and dextrorotatory anticellar forms, in racemic forms, and in mixtures of two enantiomers in any proportion. In the case of cis / trans isomerism, this disclosure includes both cis and trans forms, as well as mixtures of these forms in any proportion. Preparation of individual stereoisomers can be carried out, as necessary, by separation of mixtures by conventional methods such as chromatography or crystallization, by the use of stereochemically homogeneous starting materials for synthesis, or by stereoselective synthesis. Optionally, derivatization can also be performed before separation of stereoisomers. Separation of mixtures of stereoisomers can be carried out as an intermediate step in the synthesis of the compound, or on the final racemic product. Absolute stereochemistry can be determined, if necessary, by X-ray crystallography of crystalline products or intermediates derivatized with reagents containing stereocenters of known configurations. Alternatively, absolute stereochemistry can be determined by vibrational circular dichroism (VCD) spectroscopy.

[0338] Unless otherwise specified, the structures described herein include compounds that differ only in the presence of one or more isotopically enriched atoms, in other words, compounds in which one or more atoms are replaced by atoms having the same atomic number but with an atomic mass or mass number different from the atomic mass or mass number that is dominant in nature. These compounds are referred to as “isotope variants.” This disclosure is intended to encompass all pharmaceutically acceptable isotopic variants of the compounds of the present invention, or any formulations that describe and explain the compounds of the present invention. Examples of isotopes suitable for inclusion in the compounds of the present invention include, but are not limited to, isotopes of hydrogen (e.g., 2H (i.e., D) and 3H), isotopes of carbon (e.g., 11C, 13C, and 14C), isotopes of chlorine (e.g., 36Cl), isotopes of fluorine (e.g., 18F), isotopes of iodine (e.g., 123I, 125I), isotopes of nitrogen (e.g., 13N, 15N), isotopes of oxygen (e.g., 15O, 17O, and 18O), isotopes of phosphorus (e.g., 32P), and isotopes of sulfur (e.g., 35S). Specific isotopic variants of the compounds, or any formulas that describe and explain the compounds of this disclosure, such as those incorporating radioisotopes, may be useful in tissue distribution studies of drugs and / or substrates. In particular, compounds having the described structures that differ only in that hydrogen is replaced with a heavier isotope, such as deuterium (2H, or D), may be useful in several situations because they may offer certain therapeutic advantages, such as improved metabolic stability, extended half-life in the body, or reduced dose requirements. The compounds of this disclosure, or any isotopic variants of the compounds of this disclosure, can generally be prepared by art known to those skilled in the art, or by processes similar to those described in the accompanying examples and synthesis, using appropriate isotope-labeled reagents instead of previously used unlabeled reagents.

[0339] The compounds provided herein are described by reference to both general formulas and specific compounds. Furthermore, all compounds of this disclosure may exist in numerous different forms or derivatives within the scope of this disclosure. These include, for example, pharmaceutically acceptable salts, tautomers, stereoisomers, racemic mixtures, positional isomers, prodrugs, solvated forms, different crystalline forms or polymorphs, and active metabolites.

[0340] As used herein, the term “pharmaceutically acceptable salt” includes, unless otherwise specified, salts that retain the biological efficacy of the free acid / base form of a particular compound and are not biologically or otherwise undesirable. Pharmaceutically acceptable salts may include salts formed with inorganic bases or acids and organic bases or acids. Where a compound of the Disclosure contains one or more acidic or basic groups, the Disclosure also includes the corresponding pharmaceutically acceptable salts thereof. Thus, compounds of the Invention containing acidic groups such as carboxyl groups can exist in the form of salts and can be used in accordance with the Invention, for example, as alkali metal salts, alkaline earth metal salts, aluminum salts, or ammonium salts. More non-limiting examples of these salts include lithium salts, sodium salts, potassium salts, calcium salts, magnesium salts, barium salts, or salts with ammonia or organic amines such as ethylamine, ethanolamine, diethanolamine, triethanolamine, piperidine, N-methylglutamine, or amino acids. These salts can be readily obtained, for example, by reacting a compound having an acidic group with a suitable base, such as lithium hydroxide, sodium hydroxide, sodium propoxide, potassium hydroxide, potassium ethoxide, magnesium hydroxide, calcium hydroxide, or barium hydroxide. Other base salts of the compounds of this disclosure include, but are not limited to, copper(I), copper(II), iron(II), iron(III), manganese(II), and zinc salts. Compounds of this disclosure containing one or more basic groups, such as protonable groups, can exist in the form of salts and can be used according to the present invention in the form of addition salts with inorganic or organic acids.Examples of suitable acids include hydrogen chloride, hydrogen bromide, hydrogen iodide, phosphoric acid, sulfuric acid, nitric acid, methanesulfonic acid, p-toluenesulfonic acid, naphthalenedisulfonic acid, sulfoacetic acid, trifluoroacetic acid, oxalic acid, acetic acid, tartaric acid, lactic acid, salicylic acid, benzoic acid, carbonic acid, formic acid, propionic acid, pivalic acid, diethylacetic acid, malonic acid, succinic acid, pimelic acid, fumaric acid, maleic acid, malic acid, embonic acid, mandelic acid, sulfamic acid, phenylpropionic acid, gluconic acid, ascorbic acid, isonicotinic acid, citric acid, adipic acid, taurocholic acid, glutaric acid, stearic acid, glutamic acid, or aspartic acid, and other acids known to those skilled in the art. The salts formed include, among others, hydrochlorides, chlorides, hydrobroms, bromides, iodides, sulfates, phosphates, methanesulfons (mesylates), tosylates, carbonates, bicarbonates, formates, acetates, sulfoacetates, triflates, oxalates, malons, maleates, succinates, tartrates, malates, emponates, mandelates, fumarates, lactates, citrates, glutarates, stearates, aspartates, and glutamates. The stoichiometry of the salts formed from the compounds of this disclosure may further be an integer multiple of 1 or a non-integer multiple.

[0341] Compounds of the present disclosure containing a basic nitrogen-containing group can be quaternized using reagents such as methyl, ethyl, isopropyl, and C1-4 alkyl halides such as tert-butyl chloride, bromide, and iodide; diC1-4 alkyl sulfates such as dimethyl, diethyl, and diamyl sulfate; C10-18 alkyl halides such as decyl, dodecyl, lauryl, myristyl, and stearyl chloride, bromide, and iodide; and aryl C1-4 alkyl halides such as benzyl chloride and phenethyl bromide.

[0342] Where the compounds of this disclosure contain both acidic and basic groups in their molecules, this disclosure also includes internal salts or betaines (amphoteric ions) in addition to the salt forms described above. Each salt can be obtained by conventional methods known to those skilled in the art, for example, by contacting them with organic or inorganic acids or bases in a solvent or dispersant, or by anion exchange or cation exchange with other salts. This disclosure also includes all salts of the compounds of this disclosure that are not suitable for direct use in pharmaceuticals due to their poor physiological compatibility, but can be used, for example, as intermediates in chemical reactions or in the preparation of pharmaceutically acceptable salts. For a more appropriate review of salts, see Stahl and Wermuth, Handbook of Pharmaceutical Salts: Properties, Selection, and Use (Wiley-VCH, 2002).

[0343] Any formula describing and explaining a compound or a compound of the disclosure and its pharmaceutically acceptable salts may exist in both non-solvated and solvated forms. As used herein, the term “solvate” refers to a molecular complex comprising the compound of formula (I) or a pharmaceutically acceptable salt thereof and one or more pharmaceutically acceptable solvent molecules. For example, the term “hydrate” is used when the solvent is water.

[0344] The pharmaceutically acceptable solvates provided in this disclosure may include those in which the crystallization solvent is isotope-substituted, such as D2O, d6-acetone, and d6-DMSO.

[0345] Linker (binding compound) In some embodiments, the therapeutic agent is conjugated via a linker (or binding compound). As used herein, the terms “linker” or “binding compound” refer to a compound that can form a ligand-drug conjugate by conjugating a ligand (e.g., an antibody, its antigen-binding fragment, or an antigen-binding protein construct (e.g., a bispecific antibody)) and a therapeutic agent (e.g., any of the therapeutic agents described herein) with the groups of the ligand compound and the therapeutic agent compound, respectively, for example, by a coupling reaction.

[0346] In some embodiments, the linkers described herein are compounds having the following formula or pharmaceutically acceptable salts, solvates, stereoisomers, or isotopic variants thereof. [ka] In the formula, Q represents a junction that can be coupled to a ligand via a bond selected from the group consisting of carbonyl, thioether, amide, disulfide, and hydrazone bonds, and L represents a linker that can bind Q to a therapeutic agent.

[0347] In some embodiments, the joint portion (Q in formula (I)) has the following structure. [ka]

[0348] In some embodiments, the linker portion (L in formula (I)) has the following formula. [ka] In the formula, L1 is a polypeptide residue consisting of 3 to 8 amino acid residues, including at least one amino acid residue having a side-chain carboxyl group, such as a glutamic acid residue or an aspartic acid residue, where "-COOH" indicates the carboxyl group of the C-terminal amino acid residue of the polypeptide residue. L2 is either absent or a monodentate, bidentate, or tridentate hydrophilic group attached to the side chain carboxyl group on the amino acid residue of polypeptide residue L1, and L2 has the structure -NHC(RL2a)(RL2b)(RL2c), where RL2a, RL2b, and RL2c are independently selected from the group consisting of H, -(CH2O)(CH2CH2O)m(CH2)pC(O)OH, and -(CH2O)(CH2CH2O)m(CH2)pC(O)NHRL2d, respectively, RL2d is H or a C1-6 alkyl group optionally substituted with 1 to 6 hydroxyl groups, each m is independently 0 to 10, preferably 0 to 4, for example 0, 1, 2, 3, or 4, and particularly preferably m is 0, each p is independently 1 to 4, for example 1, 2, 3, or 4, and [ka] This indicates the N-terminal side of the polypeptide residue covalently bonded to the junction Q.

[0349] In some embodiments, polypeptide residue L1 is NH-Glu-Val-Ala-COOH. In some embodiments, the hydrophilic group L2 has the following structure. [ka] In the formula, "*" indicates a site covalently bonded to polypeptide residue L1, such as the side chain of the Glu residue in NH-Glu-Val-Ala-COOH.

[0350] In some embodiments, the linker described herein is a compound having the following structure. [ka]

[0351] In some embodiments, the linker is a VC linker. Details of the linker used in ADCs can be found, for example, in Su, Z. et al. “Antibody-drug conjugates: Recent advances in linker chemistry.” Acta Pharmaceutica Sinica B (2021), which is incorporated in its entirety by reference.

[0352] Therapeutic drugs In some embodiments, therapeutic agents conjugated to antibodies, antigen-binding fragments thereof, or antigen-binding protein constructs (e.g., bispecific antibodies) described herein are described below.

[0353] In some embodiments, the therapeutic agents described herein are cytotoxic agents. In some embodiments, the cytotoxic agent is a camptothecin compound, its analogue, or derivative. In some preferred embodiments, the camptothecin compound is a compound having the following structure. [ka] In the formula, X is selected from the group consisting of -CH2-, O, and S, and Y is selected from the group consisting of H, D, and F.

[0354] In some embodiments, the therapeutic agent is (S)-4-amino-9-ethyl-9-hydroxy-1,9,12,15-tetrahydro-13H-pyrano[3',4':6,7]indolidino[1,2-b]thiopyrano[4,3,2-de]quinoline-10,13(2H)-dione) (CPT-1). The structure of CPT-1 is shown below. [ka]

[0355] In some embodiments, the therapeutic agent is (S)-4-amino-9-ethyl-9-hydroxy-1,9,12,15-tetrahydro-13H-pyrano[4,3,2-de]pyrano[3',4':6,7]indolidino[1,2-b]quinoline-10,13(2H)-dione (CPT-2). The structure of CPT-2 is shown below. [ka]

[0356] In some embodiments, the therapeutic agent is CPT3. The structure of CPT-3 is shown below. [ka]

[0357] In some embodiments, the therapeutic agent is (S)-4-amino-9-ethyl-5-fluoro-9-hydroxy-1,9,12,15-tetrahydro-13H-pyrano[4,3,2-de]pyrano[3',4':6,7]indolidino[1,2-b]quinoline-10,13(2H)-dione (CPT-4). The structure of CPT-4 is shown below. [ka]

[0358] In some embodiments, the therapeutic agent is an auristatin, such as auristatin E (also known in the art as a derivative of drastatin-10), or a derivative thereof. Auristatin can be, for example, an ester formed of auristatin E with a keto acid. For example, auristatin E can react with paraacetylbenzoic acid or benzoylvaleric acid to produce AEB and AEVB, respectively. Other typical auristatins include AFP, MMAF, and MMAE. The synthesis and structure of exemplary auristatins are described in U.S. Patent Publication No. 2003-0083263, International Patent Publication No. WO 04 / 010957, and International Patent Publication No. WO U.S. Patent Nos. 02 / 088172, and U.S. Patent Nos. 7,498,298, 6,884,869, 6,323,315, 6,239,104, 6,034,065, 5,780,588, 5,665,860, 5,663,149, 5,635,483, 5,599,902, 5,554,725, 5,530,097, 5, These are described in Patent Nos. 521,284, 5,504,191, 5,410,024, 5,138,036, 5,076,973, 4,986,988, 4,978,744, 4,879,278, 4,816,444, and 4,486,414, each of which is incorporated herein by reference for all purposes.

[0359] Auristatin has been shown to interfere with microtubule dynamics, as well as nuclear and cell division, and has been shown to possess anticancer activity. Auristatin can bind to tubulin and exert cytotoxic or cell proliferation inhibitory effects in cancer cells. Numerous well-known assays exist in the art that can be used to measure whether auristatin or the resulting antibody-drug conjugate exerts cell proliferation inhibitory or cytotoxic effects in desired cells.

[0360] In some embodiments, the therapeutic agent is a chemotherapeutic agent. Examples of chemotherapeutic agents include thiotepa and cyclosphosphamide (CYTOXAN). TMAlkylating agents such as busulfan, improsulfan, and biposulfan, alkyl sulfonates, aziridines such as benzodopa, carbocone, metsuredopa, and uredopa, ethyleneimines and methylamelamamines such as altretamine, triethylenemelamine, triethylenephosphoramide, triethylenethiophosphoramide, and trimethylolomelamamine, chlorambucil, chlornafadin, colophosphamide, estramustine, ifosfamide, mechloretamine, mechloretamine oxide hydrochloride, melphalan, nobenbitin, f Nitrogen mustards such as enesterine, prednimastine, trophosphamide, uracil mustard, carmastine, chlorozotocin, fotemustine, lomustine, nimustine, ranimustine, nitrosoureas, acrasinomycin, actinomycin, anthramycin, azaserine, bleomycin, kactinomycin, calicheamicin, carabicin, carminomycin, cardinophiline, chromomycin, dactinomycin, daunorubicin, detrubicin, 6-diazo-5-oxo-L-norleucine, doxorubicin, epi Antibiotics such as rubicin, esorubicin, idarubicin, marcelomycin, mitomycin, mycophenolic acid, nogaramycin, olibomycin, peplomycin, potophyllomycin, puromycin, keramycin, rhodorubicin, streptonigrin, streptozocin, tubercidine, ubenimex, dinostatin, and zorubicin; antimetabolites such as methotrexate and 5-fluorouracil (5-FU); folic acid analogs such as denopterin, methotrexate, pteropterin, and trimethrexate; fludarabine, 6-mercaptopri Purine analogs such as thiamiprine and thioguanine, pyrimidine analogs such as ancitabine, azacitidine, 6-azauridine, carmofur, cytarabine, dideoxyuridine, doxifluridine, enocitabine, floxuridine, and 5-FU, androgens such as carsterone, dromostanolone propionate, epithiostanol, mepitiostane, and testolactone, anti-adrenal agents such as aminoglutethimide, mitotane, and trilostane, folic acid supplements such as folinic acid, acegraton, aldofamide glycoside, aminolevulinic acid, amsacrine,Best Love Sil, Bisanthren, Edatrexate, Defofamine, Demecoltin, Diadiquan, Elfomitin, Elptinium Acetate, Etoglucid, Gallium Nitrate, Hydroxyurea, Lentinan, Ronidamin, Mitoguazone, Mytoxantrone, Mopidamol, Nitracrine, Pentostatin, Fenamet, Pirarubicin, Podophyllic Acid, 2-Ethylhydrazide, Procarbazine, PSK 7. Lazoxane, schizophyllan, spirogermanium, tenuazonic acid, triadiquan, 2,2',2''-trichlorotriethylamine, urethane, vindesine, dacarbazine, mannomustine, mitobronitol, mitractol, pipobromane, gasitosine, arabinoside ("Ara-C"), cyclophosphamide, taxane, e.g., paclitaxel (TAXOL®, Bristol-Myers Examples include Squibb Oncology (Princeton, New Jersey), doxetaxel (TAXOTERE®, Rhone-Poulenc Rorer, Antony, France), chlorambucil, gemcitabine, 6-thioguanine, platinum analogs such as cisplatin or carboplatin, vinblastine, platinum, etoposide (VP-16), ifosfamide, mitomycin C, mitoxantrone, vincristine, vinorelbine, navelbine, novantrone, teniposide, daunomycin, aminopterin, xeloda, ibandronate, CPT-11, the topoisomerase inhibitor RFS 2000, difluoromethylornithine (DMFO), retinoic acid, esperamicin, capecitabine, and any pharmaceutically acceptable salts, acids, or derivatives of the above. This definition also includes antihormone agents that modulate or inhibit hormonal activity in tumors, such as tamoxifen, raloxifene, aromatase inhibitor 4(5)imidazole, 4-hydroxytamoxifen, trioxyfen, keoxyfen, LY117018, onapristone, and toremifene (Fareston), as well as antiandrogens such as flutamide, nilutamide, bicalutamide, leuprolide, and goserelin, and antiestrogens including any pharmaceutically acceptable salts, acids, or derivatives of the above. A detailed description of chemotherapeutic agents is available at:For example, it can be found in US20180193477A1, and the entire thing is incorporated by reference.

[0361] Linker therapeutic compound In some embodiments, a linker (e.g., any of the linkers described herein) and a therapeutic agent (e.g., any of the therapeutic agents described herein) can be linked to form a "linker-therapeutic agent" compound.

[0362] In some embodiments, the linker therapeutic compound has the following structure. [ka]

[0363] In some embodiments, the linker therapeutic compound has the following structure. [ka]

[0364] In some embodiments, an antibody ("Ab"), for example, an antibody described herein, its antigen-binding fragment, or an antigen-binding protein construct (e.g., a bispecific antibody), can be linked to a linker therapeutic compound (e.g., any of the linker therapeutic compounds described herein) to generate an antibody-drug conjugate. In some embodiments, the antibody-drug conjugate has the following structure. [ka] In the formula, n = 1, 2, 3, 4, 5, 6, 7, or 8.

[0365] Antibody and ADC characteristics In some embodiments, the antibodies or antigen-binding fragments thereof described herein, or ADCs derived therefrom, can inhibit the binding between HER3 and a HER3 ligand (e.g., heregulin).

[0366] The antibodies or antigen-binding fragments thereof, or ADCs derived therefrom, described in this specification can be agonists or antagonists. In some embodiments, the antibody or antigen-binding fragment thereof can inhibit the HER3 signaling pathway by binding to HER3. In some embodiments, the antibody or antigen-binding fragment thereof can upregulate or downregulate the immune response.

[0367] In some embodiments, the antibody (or antigen-binding fragment thereof), or ADC derived therefrom, specifically binds to HER3 (e.g., human HER3, monkey HER3 (e.g., rhesus monkey, cynomolgus monkey), canine HER3, mouse HER3) with a dissociation rate (koff) of less than 0.1 s -1 less than, less than 0.01 s -1 less than, less than 0.001 s -1 less than, less than 0.0001 s -1 less than, less than 0.00001 s -1 less than, less than 0.000001 s -1 less than, or less than 0.0000001 s -1 In some embodiments, the dissociation rate (koff) is greater than 0.01 s -1 greater than, greater than 0.001 s -1 greater than, greater than 0.0001 s -1 greater than, greater than 0.00001 s -1 greater than, greater than 0.000001 s -1 greater than, greater than 0.0000001 s -1 greater than, or greater than 0.00000001 s -1 greater than.

[0368] In some embodiments, the association rate (kon) is greater than 1×10 2 / Ms, greater than 1×10 3 / Ms, greater than 1×10 4 / Ms, greater than 1×10 5 / Ms, or greater than 1×10 6 / Ms. In some embodiments, the association rate (kon) is less than 1×10 5 / Ms, less than 1×10 6 / Ms, or less than 1×10 7 / Ms.

[0369] The affinity can be estimated from the quotient of the velocity constant (KD = koff / kon). In some embodiments, KD is 1 × 10⁻⁶ -6 Less than M, 1 x 10 -7 Less than M, 1 x 10 -8 Less than M, 1 x 10 -9 Less than M, 1 x 10 -10 Less than M, 1 x 10 -11 Less than M, 1 x 10 -12 Less than M, 1 x 10 -13 Less than M, or 1 × 10 -14 It is less than M. In some embodiments, KD is 50nM, 30nM, 20nM, 15nM, 10nM, 9nM, 8nM, 7nM, 6nM, 5nM, 4nM, 3nM, 2nM, or less than 1nM. In some embodiments, KD is 1 × 10⁻¹⁶ -7 Super M, 1×10 -8 Super M, 1×10 -9 Super M, 1×10 -10 Super M, 1×10 -11 Super M, 1×10 -12 Super M, 1×10 -13 Super M, 1×10 -14 It is greater than M.

[0370] Common techniques for measuring the affinity of an antibody to an antigen include, for example, ELISA, RIA, and surface plasmon resonance (SPR). In some embodiments, the antibody binds to human HER3 (SEQ ID NO: 43), monkey HER3 (SEQ ID NO: 44), canine HER3 (SEQ ID NO: 45), and / or mouse HER3 (SEQ ID NO: 46). In some embodiments, the antibody does not bind to human HER3, monkey HER3, canine HER3, and / or mouse HER3. In some embodiments, interspecies binding of the antibody (or its antigen-binding fragment), or ADC derived therefrom, can be measured by cell binding assays. In some embodiments, the antibodies or antigen-binding fragments thereof described herein, or ADCs derived therefrom, have a percentage of positive cells greater than 5%, greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 35%, greater than 40%, greater than 45%, greater than 50%, greater than 55%, greater than 60%, greater than 65%, greater than 70%, greater than 75%, greater than 80%, greater than 85%, greater than 90%, greater than 91%, greater than 92%, greater than 93%, greater than 94%, greater than 95%, greater than 96%, greater than 97%, or greater than 98%.

[0371] In some embodiments, an antibody (or its antigen-binding fragment), or an ADC derived therefrom, is used with MET (e.g., human MET, monkey MET (e.g., rhesus macaque, cynomolgus macaque), dog MET, mouse MET) for 0.1 seconds. -1 Less than 0.01s -1 Less than 0.001s -1 Less than 0.0001s -1 Less than 0.00001s -1 Less than 0.000001s -1 Less than, or 0.0000001s -1 It binds specifically at a dissociation rate (koff) of less than 0.01s. In some embodiments, the dissociation rate (koff) is 0.01s. -1 Super, 0.001s -1 Super, 0.0001s -1 Super, 0.00001s -1 Super, 0.000001s-1 Super, 0.0000001s -1 Greater than, or 0.00000001s -1 It's incredible.

[0372] In some embodiments, the kinetic velocity (kon) is 1 × 10⁻⁶ 2 / Ms super, 1×10 3 / Ms super, 1×10 4 / Ms super, 1×10 5 / Ms greater than, or 1 × 10⁻⁶ 6 It is greater than / Ms. In some embodiments, the motor velocity (kon) is 1 × 10⁻⁶. 5 / Ms less than 1 × 10 6 Less than / Ms, or 1 × 10⁻⁶ 7 It is less than / Ms.

[0373] The affinity can be estimated from the quotient of the velocity constant (KD = koff / kon). In some embodiments, KD is 1 × 10⁻⁶ -6 Less than M, 1 x 10 -7 Less than M, 1 x 10 -8 Less than M, 1 x 10 -9 Less than M, 1 x 10 -10 Less than M, 1 x 10 -11 Less than M, 1 x 10 -12 Less than M, 1 x 10 -13 Less than M, or 1 × 10 -14 It is less than M. In some embodiments, KD is 50nM, 30nM, 20nM, 15nM, 10nM, 9nM, 8nM, 7nM, 6nM, 5nM, 4nM, 3nM, 2nM, or less than 1nM. In some embodiments, KD is 1 × 10⁻¹⁶ -7 Super M, 1×10 -8 Super M, 1×10 -9 Super M, 1×10 -10 Super M, 1×10 -11 Super M, 1×10 -12 Super M, 1×10 -13 Super M, 1×10 -14 It is greater than M.

[0374] Common techniques for measuring the affinity of an antibody to an antigen include, for example, ELISA, RIA, and surface plasmon resonance (SPR). In some embodiments, the antibody binds to human MET (SEQ ID NO: 65), monkey MET (SEQ ID NO: 66), canine MET, and / or mouse MET. In some embodiments, the antibody does not bind to human MET, monkey MET, canine MET, and / or mouse MET. In some embodiments, interspecies binding of the antibody (or its antigen-binding fragment), or ADC derived therefrom, can be measured by cell binding assays. In some embodiments, the antibodies or antigen-binding fragments thereof described herein, or ADCs derived therefrom, have a percentage of positive cells greater than 5%, greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 35%, greater than 40%, greater than 45%, greater than 50%, greater than 55%, greater than 60%, greater than 65%, greater than 70%, greater than 75%, greater than 80%, greater than 85%, greater than 90%, greater than 91%, greater than 92%, greater than 93%, greater than 94%, greater than 95%, greater than 96%, greater than 97%, or greater than 98%.

[0375] In some embodiments, antibodies or their antigen-binding fragments described herein, or ADCs derived therefrom, are added to various cells such as NUGC-4 cells (e.g., Cobioer, catalog number: CBP60493), LN229 cells (e.g., ATCC, catalog number: CRL-2611), MCF-7 cells, SNU-5 cells (e.g., ATCC, catalog number: CRL-5973), Hep3B cells (e.g., ATCC, catalog number: HB-8064), HepG2 cells (e.g., ATCC, catalog number: HB-8065), or PLC-PRF-5 cells (e.g., ATCC, catalog number: CRL-8024), and the endocytosis ratio is tested. In some embodiments, after incubation for a certain period (e.g., 6 hours), the cells were centrifuged and washed with FACS buffer. MFI was detected using a flow cytometer, and the endocytosis ratio of the antibody was calculated. In some embodiments, the antibodies or antigen-binding fragments thereof described herein, or ADCs derived therefrom, have an endocytosis ratio greater than 5%, greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 35%, greater than 40%, greater than 45%, greater than 50%, greater than 55%, greater than 60%, greater than 65%, greater than 70%, greater than 75%, greater than 80%, greater than 85%, greater than 90%, greater than 91%, greater than 92%, greater than 93%, greater than 94%, greater than 95%, greater than 96%, greater than 97%, or greater than 98%.

[0376] In some embodiments, thermal stability is measured. Antibodies or antigen-binding fragments described herein, or ADCs derived therefrom, may have a Tm of 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, or greater than 95°C. In some embodiments, Tm is 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, or less than 95°C.

[0377] In some embodiments, the antibodies or antigen-binding fragments thereof described herein, or ADCs derived therefrom, can bind to the same epitope of HER3. In some embodiments, the antibodies or antigen-binding fragments thereof described herein, or ADCs derived therefrom, can bind to different epitopes of HER3.

[0378] In some embodiments, the antibodies or antigen-binding fragments described herein have a purity greater than 90%, greater than 91%, greater than 92%, greater than 93%, greater than 94%, greater than 95%, greater than 96%, greater than 97%, or greater than 98%, as determined by size exclusion chromatography (SEC). In some embodiments, the antibodies or antigen-binding fragments described herein have a hydrophobic interaction chromatography (HIC) retention time greater than 2 minutes, greater than 3 minutes, greater than 4 minutes, greater than 5 minutes, greater than 6 minutes, greater than 7 minutes, greater than 8 minutes, greater than 9 minutes, greater than 10 minutes, greater than 11 minutes, greater than 12 minutes, greater than 13 minutes, greater than 14 minutes, greater than 15 minutes, greater than 16 minutes, greater than 17 minutes, greater than 18 minutes, greater than 19 minutes, greater than 20 minutes, greater than 21 minutes, or greater than 22 minutes.

[0379] In some embodiments, the antibodies or antigen-binding fragments described herein have a purity of over 90%, over 91%, over 92%, over 93%, over 94%, over 95%, over 96%, over 97%, over 98%, or over 99%, as determined by capillary electrophoresis-sodium dodecyl sulfate (CE-SDS).

[0380] In some embodiments, the antibodies or antigen-binding fragments described herein have a main peak comprising more than 40%, more than 50%, more than 55%, more than 60%, more than 65%, more than 70%, more than 75%, more than 80%, more than 85%, or more than 90% when determined by capillary isoelectric focusing (cIEF). In some embodiments, the antibodies or antigen-binding fragments described herein have an acidic peak comprising more than 10%, more than 15%, more than 20%, more than 25%, more than 30%, more than 35%, more than 40%, more than 45%, more than 50%, more than 55%, more than 60%, more than 65%, more than 70%, more than 75%, more than 80%, more than 85%, or more than 90% when determined by capillary isoelectric focusing (cIEF).

[0381] In some embodiments, the ADCs described herein have a mean drug-antibody ratio (DAR) greater than 3, greater than 3.2, greater than 3.4, greater than 3.6, greater than 3.8, greater than 4, greater than 4.2, greater than 4.4, or greater than 4.6, as determined by HPLC. In some embodiments, the ADCs described herein have a mean DAR less than 3, less than 3.2, less than 3.4, less than 3.6, less than 3.8, less than 4, less than 4.2, less than 4.4, or less than 4.6, as determined by HPLC.

[0382] In some embodiments, the antibodies or antigen-binding fragments thereof described herein, or ADCs derived therefrom, have a tumor growth inhibition percentage (TGI%) greater than 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, or 200%. In some embodiments, the antibodies or antigen-binding fragments thereof described herein, or ADCs derived therefrom, have a tumor growth inhibition percentage less than 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, or 200%. TGI% can be measured, for example, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 days after the start of treatment, or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 months after the start of treatment. As used herein, the tumor growth inhibition rate (TGI%) is calculated using the following formula. TGI(%)=[1-(Ti-T0) / (Vi-V0)]×100 Ti is the mean tumor volume in the treatment group on day i. T0 is the mean tumor volume in the treatment group on day 0. Vi is the mean tumor volume in the control group on day i. V0 is the mean tumor volume in the control group on day 0.

[0383] In some embodiments, the antibodies or antigen-binding fragments thereof described herein, or ADCs derived therefrom, are HER3 antagonists. In some embodiments, the antibodies or antigen-binding fragments thereof described herein, or ADCs derived therefrom, reduce HER3 signaling in target cells expressing HER3.

[0384] In some embodiments, the antibodies or antigen-binding fragments described herein, or ADCs derived therefrom, can enhance the function of APCs (e.g., DC cells), for example, by inducing the surface expression of costimulatory molecules and MHC molecules, inducing the production of pro-inflammatory cytokines, and / or enhancing T cell triggering function.

[0385] In some embodiments, the antibodies or antigen-binding fragments described herein, or ADCs derived therefrom, can bind to HER3-expressing tumor cells. In some embodiments, the antibodies or antigen-binding fragments described herein, or ADCs derived therefrom, can induce complement-dependent cell-mediated cytotoxicity (CDC) and / or antibody-dependent cell-mediated cytotoxicity (ADCC) and kill tumor cells.

[0386] In some embodiments, the antibodies or antigen-binding fragments described herein, or ADCs derived therefrom, have a functional Fc region. In some embodiments, the effector function of the functional Fc region is antibody-dependent cell-mediated cytotoxicity (ADCC). In some embodiments, the effector function of the functional Fc region is phagocytosis. In some embodiments, the effector functions of the functional Fc region are ADCC and phagocytosis.

[0387] In some embodiments, the antibodies or antigen-binding fragments described herein, or ADCs derived therefrom, can induce complement-dependent cell-mediated cytotoxicity (CDC).

[0388] In some embodiments, the Fc region is human IgG1, human IgG2, human IgG3, or human IgG4. In some embodiments, the antibody is a human IgG1 antibody optionally having the SI mutation, LALA mutation, N297A mutation, YTE mutation, and / or FLAA mutation. In some embodiments, the antibody is a human IgG4 antibody optionally having the SI mutation, LALA mutation, N297A mutation, YTE mutation, and / or FLAA mutation.

[0389] In some embodiments, the antibodies or antigen-binding fragments described herein, or ADCs derived therefrom, do not have a functional Fc region. For example, the antibodies or antigen-binding fragments are Fab, Fab', F(ab')2, and Fv fragments. In some embodiments, the Fc region has LALA mutations (L234A and L235A mutations according to EU numbering) or LALA-PG mutations (L234A, L235A, and P329G mutations according to EU numbering). In some embodiments, the Fc region has FLAA mutations (F234A and L235A according to EU numbering). In some embodiments, Fc has SI mutations (S239D and I332E mutations according to EU numbering). In some embodiments, Fc has the N297A mutation according to EU numbering. In some embodiments, Fc has YTE mutations (M252Y, S254T, and T256E according to EU numbering).

[0390] Method for producing antibodies Isolated fragments of human proteins (e.g., HER3 or MET3) can be used as immunogens to generate antibodies using standard techniques for polyclonal and monoclonal antibody preparation. Polyclonal antibodies can be produced in animals by multiple injections (e.g., subcutaneous or intraperitoneal injection) of the antigen peptide or protein. In some embodiments, the antigen peptide or protein is injected with at least one adjuvant. In some embodiments, the antigen peptide or protein can be conjugated with a drug that is immunogenic in the immunized species. Animals may be injected with the antigen peptide or protein two or more times (e.g., two, three, or four times).

[0391] Full-length polypeptides or proteins can be used, or their antigen peptide fragments can be used as immunogens. The protein antigen peptide contains at least 8 (e.g., at least 10, 15, 20, or 30) amino acid residues of the HER3 or MET amino acid sequence and includes an epitope of the protein such that the antibody produced against the peptide forms a specific immune complex with the protein. As described above, the full-length sequence of human HER3 (SEQ ID NO: 43) is well known in the art. In some embodiments, Fc-tagged or His-tagged human HER3 protein is used as an immunogen. Similarly, the full-length sequence of human MET is also well known in the art. In some embodiments, Fc-tagged or His-tagged human MET protein is used as an immunogen.

[0392] Immunogens are typically used for antibody preparation by immunizing a suitable target (e.g., a human or transgenic animal expressing at least one human immunoglobulin locus). A suitable immunogenic preparation may contain, for example, recombinantly expressed or chemically synthesized polypeptides (e.g., fragments of human HER3 or human MET). The preparation may further contain an adjuvant, such as a Freund complete or incomplete adjuvant, or a similar immunostimulant.

[0393] Polyclonal antibodies can be prepared as described above by immunizing a suitable target with a polypeptide or its antigenic peptide (e.g., a part of HER3 or MET) as an immunogen. The antibody titer in the immunized target can be monitored over time using standard techniques such as enzyme-linked immunosorbent assay (ELISA) with immobilized polypeptides or peptides. If desired, the antibody molecule can be isolated from a mammal (e.g., from blood) and further purified by well-known techniques such as protein A chromatography or protein G chromatography to obtain the IgG fraction. At an appropriate time after immunization, for example, when the titer of specific antibodies is at its maximum, antibody-producing cells can be obtained from the target organism and used to prepare monoclonal antibodies using standard techniques such as the hybridoma technique originally described by Kohler et al. (Nature 256:495-497, 1975), the human B-cell hybridoma technique (Kozbor et al., Immunol. Today 4:72, 1983), the EBV-hybridoma technique (Cole et al., Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, Inc., pp.77-96, 1985), or the trioma technique. Techniques for producing hybridomas are well known (generally, see Current Protocols in Immunology, 1994, Coligan et al. (Eds.), John Wiley & Sons, Inc., New York, NY). For example, hybridoma cells that produce monoclonal antibodies can be detected by screening hybridoma culture supernatants for antibodies that bind to a target polypeptide or epitope using a standard ELISA assay.

[0394] Variants of antibodies or antigen-binding fragments described herein can be prepared by introducing appropriate nucleotide changes into the DNA encoding a human antibody, a humanized antibody, or a chimeric antibody, or an antibody or antigen-binding fragment described herein, or by peptide synthesis. Such variants include, for example, deletions, insertions, or substitutions of residues within the amino acid sequence that produces the antigen-binding site or antigen-binding domain of the antibody. In a population of such variants, some antibodies or antigen-binding fragments exhibit increased affinity for target proteins, such as HER3 or MET. Any combination of deletions, insertions, and / or combinations can be realized in an antibody or antigen-binding fragment with increased binding affinity to the target. Antibodies or antigen-binding fragments can be modified, or novel post-translational modifications can be introduced, by changing the amino acids introduced into the antibody or antigen-binding fragment, such as changing the number of glycosylation sites (e.g., increasing or decreasing them), changing the type of glycosylation sites (e.g., altering the amino acid sequence so that different sugars are bound by enzymes present in the cell), or introducing novel glycosylation sites.

[0395] The antibodies disclosed herein may be derived from any species of animal, including mammals. Non-limiting examples of natural antibodies include antibodies derived from humans, primates (e.g., monkeys and apes), cattle, pigs, horses, sheep, camelids (e.g., camels and llamas), chickens, goats, and rodents (e.g., rats, mice, hamsters, and rabbits), including transgenic rodents genetically modified to produce human antibodies.

[0396] Examples of human antibodies and humanized antibodies include antibodies having variable and constant regions derived from (or having the same amino acid sequence as) human germline immunoglobulin sequences. Examples of human antibodies include amino acid residues within the CDR that are not encoded by human germline immunoglobulin sequences (e.g., mutations introduced by random or site-directed mutagenesis in vitro, or somatic mutations in vivo).

[0397] Humanized antibodies typically have a human framework (FR) into which a non-human CDR has been transplanted. Therefore, a humanized antibody has one or more amino acid sequences introduced into human from a non-human source. These non-human amino acid residues are often called “import” residues, and are typically obtained from the “import” variable domain. Humanization can essentially be carried out by substituting, for example, a rodent CDR or CDR sequence with the corresponding sequence of a human antibody. These methods are described, for example, in Jones et al., Nature, 321:522-525 (1986), Riechmann et al., Nature, 332:323-327 (1988), and Verhoeyen et al., Science, 239:1534-1536 (1988), each of which is incorporated herein by reference in its entirety. Thus, a “humanized” antibody is a chimeric antibody in which a portion considerably smaller than the intact human V domain is substituted with the corresponding sequence derived from a non-human species. In practice, humanized antibodies are typically mouse antibodies in which several CDR residues and several FR residues are substituted with residues derived from similar sites within the human antibody.

[0398] The selection of human VH and VL domains used in the production of humanized antibodies is crucial for reducing immunogenicity. Following the so-called "best-fit" method, the V domain sequence of a mouse antibody is screened against an entire library of known human domain sequences. The human sequence that most closely matches the mouse sequence is then recognized as the human FR for humanized antibodies (Sims et al., J.Immunol., 151:2296 (1993), Chothia et al., J.Mol.Biol., 196:901 (1987)).

[0399] Furthermore, it is important to humanize antibodies while maintaining high specificity and affinity for antigens, as well as other desirable biological properties. To achieve this goal, humanized antibodies can be prepared by analytical processes of parental sequences and various conceptual humanization products using three-dimensional models of parental and humanized sequences. Three-dimensional immunoglobulin models are generally available and well known to those skilled in the art. Computer programs are available that can illustrate and display the possible three-dimensional structures of selected candidate immunoglobulin sequences. By observing these displays, it is possible to analyze the roles that residues can play in the functionalization of candidate immunoglobulin sequences, i.e., the residues that affect the candidate immunoglobulin's ability to bind to its antigen. In this way, FR residues can be selected and combined from recipient and import sequences to achieve desired antibody properties, such as increased affinity for the target antigen.

[0400] Typically, amino acid sequence variants of human antibodies, humanized antibodies, or chimeric antibodies contain amino acid sequences that have at least 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% identity with the sequences present in the light or heavy chain of the original antibody.

[0401] In some embodiments, mice having humanized heavy chain immunoglobulin loci and humanized κ chain immunoglobulin loci (e.g., RenMab TMAntibodies are generated using mice. A heavy chain immunoglobulin locus is a chromosomal region containing the gene for the heavy chain of an antibody. Examples of loci include the human IGHV (variable) gene, the human IGHD (variability) gene, the human IGHJ (binding) gene, and the mouse heavy chain constant domain gene. A κ chain immunoglobulin locus is a chromosomal region containing the gene encoding the light chain (κ chain) of an antibody. Examples of κ chain immunoglobulin loci include the human IGKV (variable) gene, the human IGKJ (binding) gene, and the mouse light chain constant domain gene. RenMab TM A detailed description of the mouse can be found in PCT / CN2020 / 075698 or US20200390073A1, which are incorporated herein by reference in their entirety.

[0402] In some embodiments, mice having humanized heavy chain immunoglobulin loci and humanized κ chain immunoglobulin loci (e.g., RenLite TM Antibodies are generated using mice. A heavy chain immunoglobulin locus is a chromosomal region containing the gene for the heavy chain of an antibody. Examples of loci include the human IGHV (variable) gene, the human IGHD (diversity) gene, the human IGHJ (binding) gene, and the mouse heavy chain constant domain gene. A κ chain immunoglobulin locus is a chromosomal region containing the gene encoding a common light chain. Examples of κ chain immunoglobulin loci include the human IGKV (variable) gene, the human IGKJ (binding) gene, and the mouse light chain constant domain gene. RenLite TM A detailed description of the mouse can be found in PCT / CN2021 / 097652, which is incorporated herein by reference in its entirety.

[0403] The antibodies produced by mice have a fully human VH, a fully human VL, and a mouse constant region. In some embodiments, the human VH and human VL are linked to a human IgG constant region (e.g., IgG1, IgG2, IgG3, and IgG4).

[0404] Identity or homology to the original sequence is typically the percentage of amino acid residues present in a candidate sequence that is identical to a sequence present in a human, humanized, or chimeric antibody or fragment, after aligning the sequences, introducing gaps where necessary, and achieving the maximum percentage of sequence identity, without considering conservative substitutions as part of the sequence identity.

[0405] Further modifications can be made to the antibody or antigen-binding fragment. For example, a cysteine ​​residue can be introduced into the Fc region to enable the formation of interchain disulfide bonds within this region. The homodimer antibody thus produced may have some kind of extended in vitro and / or in vivo half-life. For example, homodimer antibodies with extended in vitro and / or in vivo half-lives can also be prepared using heterobifunctional crosslinking agents, as described by Wolff et al. (Cancer Res. 53:2560-2565, 1993). Alternatively, antibodies with a double Fc region can be recombinant (see, for example, Stevenson et al., Anti-Cancer Drug Design 3:219-230, 1989).

[0406] In some embodiments, covalent modifications can be introduced into an antibody or its antigen-binding fragment. These covalent modifications can be introduced by chemical or enzymatic synthesis, or by enzymatic or chemical cleavage. Other types of covalent modifications of an antibody or antibody fragment are introduced into the molecule by reacting a targeted amino acid residue of the antibody or fragment with an organic derivatizing agent that can react with a selected side chain or an N or C-terminal residue.

[0407] In some embodiments, antibody variants are provided having carbohydrate structures lacking fucose (directly or indirectly) bound to the Fc region. For example, the amount of fucose in such antibodies may be 1% to 80%, 1% to 65%, 5% to 65%, or 20% to 40%. The amount of fucose is determined by calculating the average amount of fucose in the glycans located at Asn297 relative to the total of all sugar structures (e.g., complexes, hybrids, and high-mannose structures) bound to Asn297, measured, for example, by MALDI-TOF mass spectrometry as described in WO 2008 / 077546. Asn297 refers to the asparagine residue located at position 297 in the Fc region (Eu numbering of Fc region residues, or position 314 in Kabat numbering), however, Asn297 may also be located approximately ±3 amino acids upstream or downstream of position 297, i.e., between positions 294 and 300, due to minor sequence variations in the antibody. Such fucosylated mutants may have improved ADCC function. In some embodiments, to reduce glycan heterogeneity, the Fc region of the antibody can be further recombined, and asparagine at position 297 can be replaced with alanine (N297A).

[0408] In some embodiments, to enhance production efficiency by avoiding Fab-arm exchange, the Fc region of the antibody is further recombined, replacing serine at position 228 (EU numbering) of IgG4 with proline (S228P). A detailed description of the S228 mutation is, for example, found in Silva et al. "The S228P mutation prevents in vivo and in vitro IgG4 Fab-arm exchange as demonstrated using a combination of novel quantitative immunoassays and physiological matrix preparation." Journal of Biological Chemistry 290.9(2015):5462-5469, which is incorporated in its entirety by reference.

[0409] Recombination vectors This disclosure also provides recombinant vectors (e.g., expression vectors) containing isolated polynucleotides disclosed herein (e.g., polynucleotides encoding polypeptides disclosed herein), host cells into which the recombinant vectors have been introduced (i.e., such host cells contain polynucleotides and / or the polynucleotide-containing vectors), and the production of recombinant antibody polypeptides or fragments thereof by recombinant technology.

[0410] As used herein, “vector” is any construct that, when introduced into a host cell, can deliver one or more polynucleotides of interest to the host cell. An “expression vector” can deliver and express one or more polynucleotides of interest as encoded polypeptides within the host cell into which the expression vector has been introduced. Thus, within the expression vector, the polynucleotides of interest are positioned for expression within the vector by being operably bound to regulatory elements such as promoters, enhancers, and / or poly-A tails, either within the vector or in the host cell genome, at, near, or adjacent to the integration site of the polynucleotides of interest, so that the polynucleotides of interest are translated within the host cell into which the expression vector has been introduced.

[0411] Vectors can be introduced into host cells by methods well known in the art, such as electroporation, chemical transfection (e.g., DEAE-dextran), transformation, transfection, and infection and / or transduction (e.g., by recombinant viruses). Therefore, non-limiting examples of vectors include viral vectors (that can be used to generate recombinant viruses), naked DNA or RNA, plasmids, cosmids, phage vectors, and DNA or RNA expression vectors associated with cationic condensers.

[0412] In some embodiments, polynucleotides disclosed herein (e.g., polynucleotides encoding polypeptides disclosed herein) are introduced using a viral expression system (e.g., a smallpox or other poxvirus, retrovirus, or adenovirus), which may involve the use of a non-pathogenic (deficient) replicable virus or a non-replicable virus. In the latter case, viral replication generally occurs only in complementary viral packaging cells. Suitable systems include, for example, Fisher-Hoch et al., 1989, Proc. Natl. Acad. Sci. USA 86:317-321, Flexner et al., 1989, Ann. NYAcad Sci. 569:86-103, Flexner et al., 1990, Vaccine, 8:17-21, U.S. Patent Nos. 4,603,112, 4,769,330, and 5,017,487, WO 89 / 01973, U.S. Patent No. 4,777,127, GB 2,200,651, EP 0,345,242, WO 91 / 02805, Berkner-Biotechniques, 6:616-627, 1988, Rosenfeld et al. This is disclosed in al., 1991, Science, 252:431-434; Kolls et al., 1994, Proc. Natl. Acad. Sci. USA, 91:215-219; Kass-Eisler et al., 1993, Proc. Natl. Acad. Sci. USA, 90:11498-11502; Guzman et al., 1993, Circulation, 88:2838-2848; and Guzman et al., 1993, Cir. Res., 73:1202-1207. Techniques for incorporating DNA into such expression systems are well known to those skilled in the art. DNA may also be “naked,” as described, for example, in Ulmer et al., 1993, Science, 259:1745-1749 and Cohen, 1993, Science, 259:1691-1692. The uptake of naked DNA can be increased by coating the DNA with biodegradable beads that are efficiently transported into cells.

[0413] For expression, a DNA insert containing a polynucleotide encoding an antibody or polypeptide, as disclosed herein, can be operably ligated to a suitable promoter (e.g., a heterologous promoter), such as, to name a few, the phage λPL promoter, the E. coli lac, trp, and tac promoters, the SV40 early and late promoters, and the promoter of retroviral LTRs. Other suitable promoters are known to those skilled in the art. The expression construct may further contain sites for transcription start and end, and within the transcription region, a ribosome-binding site for translation. The coding portion of the mature transcript expressed by the construct may include a translation start at the beginning and a stop codon (UAA, UGA, or UAG) located approximately at the end of the polypeptide being translated.

[0414] As shown, the expression vector may contain at least one selectable marker. Such markers include dihydrofolate reductase or neomycin resistance for eukaryotic cell cultures, and tetracycline or ampicillin resistance genes for Escherichia coli and other bacterial cultures. Representative examples of suitable hosts include, but are not limited to, bacterial cells such as Escherichia coli, Streptomyces, and Salmonella typhimurium cells, fungal cells such as yeast cells, insect cells such as Drosophila S2 and Spodoptera litura Sf9 cells, animal cells such as CHO, COS, Bowes melanoma, and HK 293 cells, and plant cells. Suitable culture media and conditions for the host cells described herein are well known in the art.

[0415] Non-restrictive vectors for bacterial use include pQE70, pQE60, and pQE-9 from Qiagen, pBS vector, Phagescript vector, Bluescript vector, pNH8A, pNH16a, pNH18A, and pNH46A from Stratagene, and ptrc99a, pKK223-3, pKK233-3, pDR540, and pRIT5 from Pharmacia. Non-restrictive eukaryotic cell vectors include pWLNEO, pSV2CAT, pOG44, pXT1, and pSG from Stratagene, and pSVK3, pBPV, pMSG, and pSVL from Pharmacia. Other suitable vectors will be readily apparent to those skilled in the art.

[0416] Appropriate secretory signals can be incorporated into expressed polypeptides to induce the secretion of translated proteins into the endoplasmic reticulum lumen, periplasmic space, or extracellular environment. These signals can be endogenous to the polypeptide, or they can be heterologous signals.

[0417] Polypeptides (e.g., antibodies) can be expressed in modified forms such as fusion proteins (e.g., GST fusions) or by histidine tagging, and may include not only secretory signals but also additional heterologous functional regions. For example, additional amino acids, particularly charged amino acid regions, can be added to the N-terminus of a polypeptide to improve stability and endurance in host cells during purification or subsequent handling and storage. Peptide moieties can also be added to polypeptides to facilitate purification. Such regions can be removed before the final preparation of the polypeptide. Adding peptide moieties to polypeptides to induce secretion or excretion, improve stability, and facilitate purification is a well-known and common technique, particularly in the art.

[0418] Treatment method The antibodies or antigen-binding fragments thereof (e.g., anti-HER3 antibodies, anti-MET antibodies, or anti-HER3 / MET antibodies) of this disclosure can be used for a variety of therapeutic purposes.

[0419] In one embodiment, the disclosure provides a method for treating cancer in a subject, a method for slowing the rate of increase of tumor volume in a subject over time, a method for reducing the risk of metastasis, or a method for reducing the risk of further metastasis in a subject. In some embodiments, the treatment can interrupt, slow, stop, or inhibit the progression of cancer. In some embodiments, the treatment can result in a reduction of the number, severity, and / or duration of one or more symptoms of cancer in a subject.

[0420] In one embodiment, the Disclosure relates to a method comprising administering a therapeutically effective dose of an antibody or antigen-binding fragment thereof disclosed herein to a subject in need (for example, a subject having, or being identified or diagnosed with, cancer, such as breast cancer (e.g., triple-negative breast cancer), carcinoid cancer, cervical cancer, endometrial cancer, glioma, head and neck cancer, liver cancer, lung cancer, small cell lung cancer, lymphoma, melanoma, ovarian cancer, pancreatic cancer, prostate cancer, kidney cancer, colorectal cancer, gastric cancer, testicular cancer, thyroid cancer, bladder cancer, esophageal cancer, urethral cancer, or hematological malignancy). In some embodiments, the cancer is unresectable or metastatic melanoma, non-small cell lung cancer (NSCLC), small cell lung cancer (SCLC), bladder cancer, or metastatic hormone-refractory prostate cancer. In some embodiments, the cancer is NSCLC, ovarian cancer, melanoma, colorectal cancer, breast cancer, hematological malignancies, head and neck cancer, gastrointestinal cancer, bladder cancer, or bone cancer. In some embodiments, the subject has solid tumors. In some embodiments, the cancer is squamous cell carcinoma of the head and neck (SCCHN), renal cell carcinoma (RCC), triple-negative breast cancer (TNBC), or colorectal cancer. In some embodiments, the subject has Hodgkin lymphoma. In some embodiments, the subject has triple-negative breast cancer (TNBC), gastric cancer, urothelial carcinoma, Merkel cell carcinoma, or head and neck cancer. In some embodiments, the cancer is melanoma, pancreatic cancer, mesothelioma, hematological malignancies, in particular non-Hodgkin lymphoma, lymphoma, chronic lymphocytic leukemia, or progressive solid tumors. In some embodiments, the cancer is colorectal cancer, gastric cancer, breast cancer, lung cancer, melanoma, ovarian cancer, head and neck cancer, pancreatic cancer, liver cancer, or cervical cancer.

[0421] In some embodiments, the compositions and methods disclosed herein can be used to treat patients at risk of cancer. Patients at risk of cancer can be identified by various methods well known in the art.

[0422] In one embodiment, the present disclosure provides methods for treating, preventing, or reducing the risk of developing diseases associated with abnormal or undesirable immune responses, such as autoimmune diseases. These autoimmune diseases include alopecia areata, lupus, ankylosing spondylitis, Meniere's disease, antiphospholipid syndrome, mixed connective tissue disease, autoimmune Addison's disease, multiple sclerosis, autoimmune hemolytic anemia, myasthenia gravis, autoimmune hepatitis, pemphigus vulgaris, Behçet's disease, pernicious anemia, bullous pemphigoid, polyarteritis nodosa, cardiomyopathy, polychondritis, sprue dermatitis, polyglandular syndrome, chronic fatigue syndrome (CFIDS), polymyalgia rheumatica, chronic inflammatory demyelination, polymyositis and dermatomyositis, chronic inflammatory polyneuropathy, primary agammaglobulinemia, Churg-Strauss syndrome, and primary biliary tract disease. Examples of conditions that may be included, but are not limited to, sap cirrhosis, pemphigoid scarring, psoriasis, Crest syndrome, Raynaud's phenomenon, cold agglutinin disease, Reiter's syndrome, Crohn's disease, rheumatic fever, lupus discoid, rheumatoid arthritis, cold globulinemia sarcoidosis, fibromyalgia, scleroderma, Graves' disease, Sjögren's syndrome, Guillain-Barré syndrome, Stiffman syndrome, Hashimoto's thyroiditis, Takayasu's arteritis, idiopathic alveolar fibrosis, temporal arteritis / giant cell arteritis, idiopathic thrombocytopenic purpura (ITP), ulcerative colitis, IgA nephropathy, uveitis, diabetes mellitus (e.g., type 1), vasculitis, lichen planus, and vitiligo. Antibodies or their antigen-binding fragments can also be administered to subjects to treat, prevent, or reduce the risk of progression of abnormal or undesirable immune responses associated with cell, tissue, or organ transplantation, such as kidney, liver, and heart transplants, or to prevent allograft rejection. In some embodiments, subjects have skin diseases, liver diseases (e.g., cirrhosis), hidradenitis, or experimental autoimmune encephalomyelitis. In some embodiments, subjects have kidney diseases, lupus, Sjögren's syndrome, ulcerative colitis, psoriasis, hidradenitis suppurativa, immune thrombocytopenia (ITP), or other inflammatory arthritis. In some embodiments, subjects have multiple sclerosis or myasthenia gravis. In some embodiments, subjects have Crohn's disease, ulcerative colitis, or type 1 diabetes.In some embodiments, the subject has an autoimmune thyroid disease, Graves' disease, multiple sclerosis, psoriasis, inflammatory bowel disease (e.g., Crohn's disease (CD) and ulcerative colitis), rheumatoid arthritis, Sjögren's syndrome, autoimmune nephritis, or systemic lupus erythematosus. In some embodiments, the method comprises administering to the subject an effective amount of a composition comprising an antibody or antigen-binding fragment thereof as described herein.

[0423] As used herein, “effective dose” means an amount or dosage sufficient to produce a beneficial or desired outcome, including interrupting, slowing, blocking, or inhibiting the progression of a disease, such as an autoimmune disease or cancer. The effective dose varies depending on the age and weight of the person to whom the antibody, antigen-binding fragment, polynucleotide encoding the antibody, vector containing the polynucleotide, and / or composition thereof is administered, the severity of the symptoms, and the route of administration, and therefore the administration can be determined on an individual basis.

[0424] An effective dose can be administered in one or more doses. For example, an effective dose of antibody or antigen-binding fragment is an amount sufficient to mitigate, halt, stabilize, reverse, inhibit, slow, and / or delay the progression of an autoimmune disease or cancer in a patient, or an amount sufficient to mitigate, halt, stabilize, reverse, slow, and / or delay the proliferation of cells (e.g., biopsy cells, any of the cancer cells described herein, or cell lines (e.g., cancer cell lines)) in vitro. As is understood in the art, an effective dose of antibody or antigen-binding fragment may vary depending on other factors, in particular, the patient's medical history, as well as the type (and / or dose) of antibody used.

[0425] The effective doses and schedules for administering the antibodies, polynucleotides encoding the antibodies, and / or compositions disclosed herein can be determined experimentally, and making such determinations is within the capabilities of those skilled in the art. Those skilled in the art will understand that the dose to be administered will vary depending, for example, on the mammal receiving the antibodies, polynucleotides encoding the antibodies, and / or compositions disclosed herein, the route of administration, the specific type of antibody, the polynucleotide encoding the antibody, the antigen-binding fragment, and / or the compositions disclosed herein used, and other agents administered to the mammal. Guidelines for selecting an appropriate dose for an antibody or antigen-binding fragment can be found in literature on the therapeutic use of antibodies and antigen-binding fragments, such as Handbook of Monoclonal Antibodies, Ferrone et al., eds., Noges Publications, Park Ridge, NJ, 1985, ch.22 and pp.303-357, and Smith et al., Antibodies in Human Diagnosis and Therapy, Haber et al., eds., Raven Press, New York, 1977, pp.365-389.

[0426] The typical daily dose of an effective amount of antibody is 0.01 mg / kg to 100 mg / kg. In some embodiments, the dose may be 100 mg / kg, 10 mg / kg, 9 mg / kg, 8 mg / kg, 7 mg / kg, 6 mg / kg, 5 mg / kg, 4 mg / kg, 3 mg / kg, 2 mg / kg, 1 mg / kg, 0.5 mg / kg, or less than 0.1 mg / kg. In some embodiments, the dose may be 10 mg / kg, 9 mg / kg, 8 mg / kg, 7 mg / kg, 6 mg / kg, 5 mg / kg, 4 mg / kg, 3 mg / kg, 2 mg / kg, 1 mg / kg, 0.5 mg / kg, 0.1 mg / kg, 0.05 mg / kg, or greater than 0.01 mg / kg. In some embodiments, the dose is approximately 10 mg / kg, 9 mg / kg, 8 mg / kg, 7 mg / kg, 6 mg / kg, 5 mg / kg, 4 mg / kg, 3 mg / kg, 2 mg / kg, 1 mg / kg, 0.9 mg / kg, 0.8 mg / kg, 0.7 mg / kg, 0.6 mg / kg, 0.5 mg / kg, 0.4 mg / kg, 0.3 mg / kg, 0.2 mg / kg, or 0.1 mg / kg.

[0427] In any of the methods described herein, at least one antibody, its antigen-binding fragment, or pharmaceutical composition (e.g., any of the antibodies, antigen-binding fragments, or pharmaceutical compositions described herein), and optionally at least one additional therapeutic agent, can be administered to a target at least once a week (e.g., once a week, twice a week, three times a week, four times a week, once a day, twice a day, or three times a day). In some embodiments, at least two different antibodies and / or antigen-binding fragments are administered in the same composition (e.g., a liquid composition). In some embodiments, at least one antibody or antigen-binding fragment and at least one additional therapeutic agent are administered in the same composition (e.g., a liquid composition). In some embodiments, at least one antibody or antigen-binding fragment and at least one additional therapeutic agent are administered in two different compositions (e.g., a liquid composition containing at least one antibody or antigen-binding fragment and a solid oral composition containing at least one additional therapeutic agent). In some embodiments, at least one additional therapeutic agent is administered as a pill, tablet, or capsule. In some embodiments, at least one additional therapeutic agent is administered in a sustained-release oral formulation.

[0428] In some embodiments, one or more additional therapeutic agents can be administered to a subject before or after administration of at least one antibody, antigen-binding antibody fragment, or pharmaceutical composition (e.g., any of the antibodies, antigen-binding antibody fragments, or pharmaceutical compositions described herein). In some embodiments, one or more additional therapeutic agents and at least one antibody, antigen-binding antibody fragment, or pharmaceutical composition (e.g., any of the antibodies, antigen-binding antibody fragments, or pharmaceutical compositions described herein) are administered to a subject such that the biological activity periods of the one or more additional therapeutic agents and the biological activity periods of at least one antibody or antigen-binding fragment (e.g., any of the antibodies or antigen-binding fragments described herein) overlap within the subject.

[0429] In some embodiments, at least one antibody, antigen-binding antibody fragment, or pharmaceutical composition (e.g., any of the antibodies, antigen-binding antibody fragments, or pharmaceutical compositions described herein) can be administered to a subject over a long period of time (e.g., over a period of at least one week, two weeks, three weeks, one month, two months, three months, four months, twelve months, one year, two years, three years, four years, or five years). A skilled medical professional may determine the length of the treatment period using any of the methods described herein to diagnose or follow up on the effectiveness of the treatment (e.g., to observe at least one symptom of cancer). As described herein, skilled medical professionals may also change (e.g., increase or decrease) the identity and number of antibodies or antigen-binding antibody fragments (and / or one or more additional therapeutic agents) administered to a subject, and may adjust (e.g., increase or decrease) the dose or frequency of at least one antibody or antigen-binding antibody fragment (and / or one or more additional therapeutic agents) administered to a subject based on an assessment of the effectiveness of the treatment (e.g., using any of the methods described herein and known in the art).

[0430] In some embodiments, one or more additional therapeutic agents may be administered to the subject. The additional therapeutic agents may include one or more inhibitors selected from the group consisting of B-Raf inhibitors, EGFR inhibitors, MEK inhibitors, ERK inhibitors, K-Ras inhibitors, c-MET inhibitors, anaplastic lymphoma kinase (ALK) inhibitors, phosphatidylinositol 3-kinase (PI3K) inhibitors, Akt inhibitors, mTOR inhibitors, dual PI3K / mTOR inhibitors, Bruton's tyrosine kinase (BTK) inhibitors, and isocitrate dehydrogenase 1 (IDH1) and / or isocitrate dehydrogenase 2 (IDH2) inhibitors. In some embodiments, the additional therapeutic agent is an indoleamine 2,3-dioxygenase-1 (IDO1) inhibitor (e.g., epacadostat).

[0431] In some embodiments, additional therapeutic agents may include one or more inhibitors selected from the group consisting of HER3 inhibitors, MET inhibitors, helegrin inhibitors, LSD1 inhibitors, MDM2 inhibitors, BCL2 inhibitors, CHK1 inhibitors, inhibitors of the activated Hedgehog signaling pathway, and agents that selectively degrade estrogen receptors.

[0432] In some embodiments, additional therapeutic agents may include one or more agents selected from the group consisting of trabectedin, nab-paclitaxel, trevananib, sediranib, palbociclib, everolimus, fluoropyrimidine, IFL, regorafenib, reolisin, alimta, jikaida, sutent, temsirolimus, axitinib, everolimus, sorafenib, votrient, pazopanib, IMA-901, AGS-003, cabozantinib, vinflunin, Hsp90 inhibitors, Ad-GM-CSF, temozolomide, IL-2, IFNa, vinblastine, salomib, dacarbazine, cyclophosphamide, lenalidomide, azacitidine, bortezomib, amrubicin, carfilzomib, pralatrexate, and enzastaurin.

[0433] In some embodiments, additional therapeutic agents may include one or more agents selected from the group consisting of adjuvants, TLR agonists, tumor necrosis factor (TNF)α, IL-1, HMGB1, IL-10 antagonists, IL-4 antagonists, IL-13 antagonists, IL-17 antagonists, HVEM antagonists, ICOS agonists, CX3CL1-targeted therapies, CXCL9-targeted therapies, CXCL10-targeted therapies, CCL5-targeted therapies, LFA-1 agonists, ICAM1 agonists, HER2 agonists, and heregulin agonists.

[0434] In some embodiments, carboplatin, nab-paclitaxel, paclitaxel, cisplatin, pemetrexed, gemcitabine, FOLFOX, or FOLFIRI are administered to the subject.

[0435] In some embodiments, additional therapeutic agents include anti-OX40 antibody, anti-PD-1 antibody, anti-PD-L1 antibody, anti-PD-L2 antibody, anti-LAG-3 antibody, anti-TIGIT antibody, anti-BTLA antibody, anti-CTLA-4 antibody, anti-ICOS antibody, anti-CD27 antibody, anti-OX40 antibody, anti-4-1BB antibody, anti-CD40 antibody, anti-VEGFR2 antibody, anti-EGFR antibody, anti-HER2 antibody, and / or anti-GITR antibody.

[0436] In one embodiment, the present disclosure provides a combination therapy. In some embodiments, an anti-HER3 antibody or its antigen-binding fragment (e.g., any antibody described herein) may be administered together with an anti-PD1 antibody.

[0437] Pharmaceutical composition and route of administration Pharmaceutical compositions containing at least one (e.g., 1, 2, 3, or 4) of the antibodies or antigen-binding fragments described herein are also provided herein. Two or more (e.g., 2, 3, or 4) of any of the antibodies or antigen-binding fragments described herein may be present in any combination in the pharmaceutical composition. The pharmaceutical composition may be formulated in any form well known in the art.

[0438] Pharmaceutical compositions are formulated to be compatible with their intended route of administration (e.g., intravenous, intra-arterial, intramuscular, intradermal, subcutaneous, or intraperitoneal). Compositions may include sterile diluents (e.g., sterile water or saline), non-volatile oils, polyethylene glycol, glycerin, propylene glycol, or other synthetic solvents, antimicrobial or antifungal agents (e.g., benzyl alcohol or methylparaben, chlorobutanol, phenol, ascorbic acid, thimerosal, etc.), antioxidants (e.g., ascorbic acid or sodium bisulfite), chelating agents (e.g., ethylenediaminetetraacetic acid), buffers (e.g., acetate, citrate, or phosphate), and isotonic agents (e.g., sugars (e.g., dextrose), polyalcohols (e.g., mannitol or sorbitol), or salts (e.g., sodium chloride)), or any combination thereof. Liposome suspensions can also be used as pharmaceutically acceptable carriers (see, for example, U.S. Patent No. 4,522,811). The composition preparations can be formulated and encapsulated in ampoules, disposable syringes, or multi-dose vials. Where necessary (e.g., in injectable formulations), adequate fluidity can be maintained by coatings such as lecithin or by the use of surfactants. The absorption of antibodies or their antigen-binding fragments can be prolonged by including absorption-delaying agents (e.g., aluminum monostearate and gelatin). Alternatively, sustained release can be achieved by implants and microencapsulation delivery systems, including biodegradable and biocompatible polymers (e.g., ethylene vinyl acetate, polyanhydride, polyglycolic acid, collagen, polyorthoesters, and polylactic acid, Alza Corporation and Nova Pharmaceutical, Inc.).

[0439] Compositions containing one or more antibodies or antigen-binding fragments described herein can be formulated in unit dosage forms (i.e., physically distinct units containing a predetermined amount of the active compound to facilitate administration and ensure uniformity of dose) for parenteral administration (e.g., intravenous, intra-arterial, intramuscular, intradermal, subcutaneous, or intraperitoneal).

[0440] Pharmaceutical compositions for parenteral administration are preferably sterile, substantially isotonic, and manufactured under Good Manufacturing Practice (GMP) conditions. Pharmaceutical compositions may be supplied in unit dosage forms (i.e., doses for single administration). Pharmaceutical compositions can be formulated using one or more physiologically acceptable carriers, diluents, excipients, or adjuvants. Formulation depends on the chosen route of administration. For injection, antibodies can be formulated in aqueous solution, preferably in a physiologically compatible buffer, to reduce discomfort at the injection site. The solution may contain compounding agents such as suspending agents, stabilizers, and / or dispersants. Alternatively, antibodies may be in lyophilized form for preparation with a suitable vehicle, e.g., sterile pyrogen-free water, before use.

[0441] The toxicity and therapeutic effect of a composition can be determined by standard pharmaceutical procedures in cell culture media or experimental animals (e.g., monkeys). For example, the LD50 (lethal dose for 50% of the population) and ED50 (effective dose for 50% of the population) can be determined, and the therapeutic index is the ratio of LD50:ED50. Drugs exhibiting a high therapeutic index are preferred. If a drug exhibits undesirable side effects, care must be taken to minimize the potential harm (i.e., mitigate the undesirable side effects). Toxicity and therapeutic effect can be determined by other standard pharmaceutical procedures.

[0442] Data obtained from cell culture assays and animal studies can be used in the formulation of appropriate doses of any given agent for use in subjects (e.g., humans). A therapeutically effective dose of one or more antibodies (e.g., 1, 2, 3, or 4) or their antigen-binding fragments (e.g., any of the antibodies or antibody fragments described herein) is the amount that treats the disease (e.g., kills cancer cells) or reduces the severity, frequency, and / or duration of one or more symptoms of the disease in a subject (e.g., a human subject identified as having cancer) or a subject identified as being at risk of developing the disease (e.g., a subject who has previously had cancer but is now cured), or the amount that reduces the severity, frequency, and / or duration of one or more symptoms of the disease in a subject (e.g., a human). The efficacy and administration of any of the antibodies or antigen-binding fragments described herein can be determined by a healthcare professional or veterinary professional using methods well known in the art, in addition to observing one or more symptoms of the disease in a subject (e.g., a human). Certain factors may influence the dose and timing required to effectively treat the subject (e.g., severity of the disease or disability, previous treatments, the subject's overall health and / or age, and the presence of other diseases).

[0443] Exemplary doses include the amount (milligrams or micrograms) of either the antibody or antigen-binding fragment described herein per kilogram of body weight of the subject (e.g., approximately 1 μg / kg to 500 mg / kg, approximately 100 μg / kg to 500 mg / kg, approximately 100 μg / kg to 50 mg / kg, approximately 10 μg / kg to 5 mg / kg, approximately 10 μg / kg to 0.5 mg / kg, or approximately 1 μg / kg to 50 μg / kg). Although these doses cover a wide range, those skilled in the art will understand that the efficacy and effective dose of therapeutic agents containing antibodies and their antigen-binding fragments can be determined by methods well known in the art. Typically, a relatively low dose is administered first, and the dose can be subsequently and gradually increased by the healthcare professional or veterinary professional (in the case of therapeutic use), or the researcher (if still working in the development stage), until an appropriate response is obtained. In addition, it is understood that the specific dose level for any particular subject depends on various factors, including the activity of the specific compound used, the subject's age, weight, overall health, sex, and diet, administration time, route of administration, excretion rate, and the half-life of the antibody or antibody fragment in the body.

[0444] The pharmaceutical composition may be included in a container, pack, or dispenser, along with instructions for administration. This disclosure also provides methods for producing antibodies or their antigen-binding fragments for various applications described herein. [Examples]

[0445] The present invention will be further illustrated by the following embodiments, which are not intended to limit the scope of the invention as described in the claims.

[0446] Example 1. Generation of human anti-HER3 antibody Human HER3 protein (hHER3-His, ACRO Biosystems Inc., catalog number: ER3-H5223), or the DNA encoding this protein, is emulsified with an adjuvant and used with RenLite TMMice were immunized with Biocytogen, a fully human heavy chain variable domain combined with a common light chain substitution in situ. RenLite TM The mice are described, for example, in PCT / CN2021 / 097652, which is incorporated herein by reference in its entirety. Postorbital blood was collected as a negative control prior to immunization.

[0447] For the initial immunization, Freund's complete adjuvant (CFA) was used, and for the second, third, and fourth immunizations, Freund's incomplete adjuvant (IFA) was used. A total of four immunizations were performed. The first and second immunizations were spaced two weeks apart, and the remaining immunizations were spaced one week apart. One week after the fourth immunization, post-orbital blood was collected, and serum antibody titers were detected by fluorescence-activated cell sorting (FACS). One week later, mice with high titers were further injected with hHER3-His protein by intraperitoneal injection for impulse immunization.

[0448] Antigen-specific immune cells were isolated from immunized mice, and anti-HER3 antibodies were obtained, or the light and heavy chain variable region sequences of anti-HER3 antibodies were obtained. For example, plasma cells secreting antigen-specific monoclonal antibodies were screened and discovered using single-cell techniques (e.g., Beacon® Optofluidic System, Berkeley Lights Inc.), and then the antibody variable region sequences were obtained using reverse transcription and PCR sequencing. The obtained variable region sequences were cloned into vectors containing sequences encoding the human IgG1 constant region for antibody expression. Binding of the expressed antibodies to HER3 was confirmed by FACS. Exemplary antibodies obtained by this method include 1B2, 1C5, 1D6, 3E1, and 3G6.

[0449] These antibodies contain substantially the same light chain, and the sequences of their VH CDR1-3 and VL CDR1-3 are shown in Figure 3A or Figure 4A. The VH and VL regions of 1B2, 1C5, 1D6, 3E1, and 3G6 are shown in Figure 5.

[0450] The anti-HER3 antibodies described above can form pairs to create various bispecific antibodies. Vectors encoding the light and heavy chains of the antibodies were constructed. CHO-S cells were co-transfected with three vectors: a first vector encoding the heavy chain of an anti-HER3 antibody, a second vector encoding the heavy chain of another anti-HER3 antibody, and a third vector encoding a common light chain. After 14 days of culture, the cell supernatant was collected and purified by protein A affinity chromatography.

[0451] Similarly, the anti-HER3 antibodies described above can also be used to form bispecific antibodies targeting HER3 and another target protein (e.g., MET). 2F11, 8E2, 8D9, and 8H10 are anti-MET monoclonal antibodies developed by Biocytogen Pharmaceuticals (Beijing) Company Limited. These antibodies have the same light chain, and their sequences are consistent with the common light chain sequence of anti-HER3 antibodies. The sequences of their VH CDR1-3 are shown in Figures 3B and 4B. The VL and VH regions of 2F11 and 8E2 are shown in Figure 5. Further details regarding 2F11, 8E2, 8D9, and 8H10 are described in PCT / CN2022 / 141416 or PCT / CN2023 / 103811, which are incorporated herein by reference in their entirety.

[0452] To reduce the possibility of mispairing between the two heavy chains, knobs-into-holes were introduced into the Fc region of the antibody. Examples of bispecific antibodies obtained include 3E1-1C5, 3G6-1C5, 1B2-1C5, 3E1-2F11, 3G6-2F11, 1B2-2F11, 1C5-2F11, 2F11-3E1, 2F11-3G6, 2F11-1B2, 2F11-1C5, 3E1-8E2, 3G6-8E2, 1B2-8E2, 1C5-8E2, 8E2-3E1, 8E2-3G6, 8E2-1B2, 8E2-1C5, 3E1-8D9, 1B2-8D9, 1C5-8D9, 3E1-8H10, 1B2-8H10, and 1C5-8H10. In 3E1-1C5, a knob mutation is present in the heavy chain constant region of 3E1, and a hole mutation is present in the heavy chain constant region of 1C5. In 3G6-1C5, a knob mutation is present in the heavy chain constant region of 3G6, and a hole mutation is present in the heavy chain constant region of 1C5. The sequence of the human IgG1 constant region with the knob mutation is shown in SEQ ID NO: 49, and the sequence of the human IgG1 constant region with the hole mutation is shown in SEQ ID NO: 50.

[0453] Example 2. Interspecies binding of anti-HER3 antibodies CHO-hHER3 cells, CHO-mHER3 cells, CHO-fasHER3 cells, or CHO-dHER3 cells, 5 × 10 4 Cells were seeded at a density of 1 cell / well into 96-well plates. Anti-HER3 antibody was added to the 96-well plates and incubated at 4°C for 30 minutes. Next, the cells were incubated with the secondary antibody anti-hIgG-Fc-Alex Flour 647(RL1-H) (Jackson ImmunoResearch Laboratories, Inc., catalog number: 109-606-170) at 4°C in the dark for 15 minutes, followed by flow cytometry analysis.

[0454] CHO-hHER3 cells, CHO-mHER3 cells, CHO-fasHER3 cells, and CHO-dHER3 cells were obtained by transfecting CHO-S cells with human HER3 (hHER3, SEQ ID NO: 43), monkey (cynomolgus monkey) HER3 (fasHER3, SEQ ID NO: 44), canine HER3 (dHER3, SEQ ID NO: 45), and mouse HER3 (mHER3, SEQ ID NO: 46), respectively.

[0455] The test results are shown in the table below. All anti-HER3 antibodies, 1B2, 1C5, 1D6, 3E1, and 3G6, can bind to human HER3, monkey HER3, and canine HER3. Of these antibodies, 1B2, 1D6, 3E1, and 3G6 can bind to mouse HER3.

[0456] [Table 1]

[0457] In a similar experiment, the interspecific binding activity of anti-HER3 / MET bispecific antibodies was tested. Specifically, CHO-hHER3 cells, CHO-fasHER3 cells, NIH3T3-hMET cells, or NIH3T3-fasMET cells were subjected to 5 × 10⁻¹⁴ binding. 4 The cells were transferred to 96-well plates at a density of 1 cell / well. Antibodies were added to the 96-well plates and incubated at 4°C for 30 minutes. Next, the cells were incubated with the secondary antibody, anti-hIgG-Fc-Alex Flour 647(RL1-H), in the dark at 4°C for 15 minutes, followed by flow cytometry analysis.

[0458] NIH3T3-hMET cells and NIH3T3-fasMET cells were obtained by transfecting NIH3T3 cells with plasmids expressing human MET (hMET, SEQ ID NO: 65) and monkey MET (fasMET, SEQ ID NO: 66), respectively.

[0459] The test results are shown in the table below. All anti-HER3 / MET bispecific antibodies can bind to human HER3, monkey HER3, human MET, and monkey MET.

[0460] [Table 2]

[0461] Example 3. Cross-binding activity of anti-HER3 antibody to HER family proteins The cross-binding activity of anti-HER3 antibodies to HER family proteins was determined by surface plasmon resonance (SPR) using a Biacore (Biacore, Inc., Piscataway, New Jersey) 8K biosensor equipped with a pre-immobilized protein A sensor chip.

[0462] Examples of HER family proteins include human EGFR (hEGFR, ACRO Biosystems Inc., catalog number: EGR-H5222), human HER2 (hHER2, ACRO Biosystems Inc., catalog number: HE2-H5225), human HER3 (hHER3, ACRO Biosystems Inc., catalog number: ER3-H5223), and human HER4 (hHER4, ACRO Biosystems Inc., catalog number: ER4-H5221).

[0463] Purified anti-HER3 antibodies were diluted to 2 μg / mL and then injected into a Biacore 8K biosensor at 10 μL / min for approximately 50 seconds to achieve the desired protein density (e.g., approximately 200 response units (RU)). Patrizumab analogs of the anti-HER3 antibody were used as positive controls. Kinetic measurements were performed with recombinant His-tagged HER family proteins at concentrations of 0 nM, 3.125 nM, 6.25 nM, 12.5 nM, 25 nM, 50 nM, 100 nM, 200 nM, and 400 nM. The association phase lasted 180 seconds, the dissociation phase lasted 400 seconds, followed by a regeneration step with glycine (pH 2.0, 30 μL / min for 30 seconds). For isotype controls (ISOs), antibodies targeting unrelated target proteins were used.

[0464] The results are shown in Figures 1A-G. Anti-HER3 antibodies 1B2, 1C5, 3E1, and 3G6 do not bind to other human HER family proteins other than HER3.

[0465] Patritumab is an anti-HER3 fully human monoclonal antibody developed by Daiichi Sankyo, and its heavy chain variable region and light chain variable region are shown in SEQ ID NO: 47 and SEQ ID NO: 48, respectively.

[0466] Example 4. Internalization of anti-HER3 antibody Anti-HER3 antibody (2.5 μg / mL) and pHAb-AffiniPure Fab goat anti-human IgG secondary antibody were added to NUGC-4 cells (Cobioer, catalog number: CBP60493), MCF-7 cells (ATCC, catalog number: CRL-3435), or LN229 cells (ATCC, catalog number: CRL-2611), and incubated for 4-6 hours. RNA sequencing revealed HER3 expression levels of 155, 76, and 53 in NUGC-4, MCF-7, and LN229 cells, respectively. After incubation, cells were centrifuged and washed with FACS buffer. MFI was detected by flow cytometry, and the endocytosis ratio of the anti-HER3 antibody was calculated. Human IgG1 was used as the ISO control. The results are summarized in the table below.

[0467] [Table 3]

[0468] The data showed that 1B2, 1C5, 1D6, 3E1, and 3G6 exhibited favorable endocytosis rates in LN229, NUGC-4, and MCF-7 cells. In addition, the endocytotic activity of the bispecific antibodies 3E1-1C5, 1B2-1C5, and 3G6-1C5 was significantly enhanced compared to the monoclonal antibodies 3E1, 1B2, 3G6, and 1C5 in NUGC-4 and MCF-7 cells.

[0469] In a similar experiment, anti-HER3 antibody (2.5 μg / mL) and pHAb-AffiniPure Fab goat anti-human IgG secondary antibody were added to canine mammary cancer CMT-U27 cells (ATCC, catalog number: CRL-3456). After incubation for 6 hours, the cells were centrifuged and washed with FACS buffer. MFI was detected by flow cytometry, and the endocytosis ratio of the anti-HER3 antibody was calculated. The percentage of 3E1-positive cells and MFI were 15.7% and 9796, respectively, while the percentage of 3E1-positive cells and MFI for the positive control, the patrizumab analog, were 3.0% and 8403, respectively, indicating that 3E1 showed a favorable endocytosis ratio in CMT-U27 cells.

[0470] In another similar experiment, anti-HER3 / MET bispecific antibodies (2.5–10 μg / mL) and pHAb-AffiniPure Fab goat anti-human IgG secondary antibodies were added to SNU-5 cells (ATCC, catalog number: CRL-5973), Hep3B cells (ATCC, catalog number: HB-8064), HepG2 cells (ATCC, catalog number: HB-8065), PLC-PRF-5 cells (ATCC, catalog number: CRL-8024), or NUGC-4 cells. After incubation for 6 hours, the cells were centrifuged and washed with FACS buffer. MFI was detected by flow cytometry, and the antibody endocytosis ratio was calculated. The results are summarized in the table below.

[0471] Terisotuzumab is a humanized IgG1 monoclonal antibody targeting MET, currently in early clinical development at AbbVie for the treatment of advanced solid tumors with MET gene amplification. The sequences of its heavy chain variable region and light chain variable region are shown in SEQ ID NO: 67 and SEQ ID NO: 68, respectively.

[0472] [Table 4]

[0473] The anti-HER3 / MET bispecific antibody demonstrated better or equivalent endocytosis efficiency than the positive control patritumab analog and terisotuzumab analog. Furthermore, the endocytosis efficiency of the anti-HER3 / MET bispecific antibody was maintained or improved compared to the parental monoclonal antibody.

[0474] Example 5. Binding affinity of anti-HER3 antibody The binding affinity of anti-HER3 antibodies to human His-tagged HER3 protein (hHER3, ACRO Biosystems Inc., catalog number: ER3-H5223), monkey (fasHER3, Sino Biological, Inc., catalog number: 90043-K08H), or dog (dHER3, SEQ ID NO: 45) was measured using a Biacore equipped with a pre-immobilized protein A sensor chip. TM (Biacore, Inc., Piscataway, New Jersey) Validated using an 8K biosensor.

[0475] Purified anti-HER3 antibody was captured on a Protein A tip (Series S Sensor Tip Protein A) for detection. 1 μg / mL of anti-HER3 antibody was loaded at 10 μL / min and conjugated to gradient concentrations of hHER3, fasHER3, and dHER3 (400, 200, 100, 50, 25, 12.5, 6.25, 3.125, 1.5626, and 0 nM). For the ISO control, an antibody targeting an unrelated target protein was used. The flow rate was 30 μL / min, and the conjugation and dissociation times were set to 180 seconds and 400 seconds, respectively. After the final injection of each titration, the tip was refilled with glycine solution (pH 2.0) at 30 μL / min for 30 seconds.

[0476] Biacore TM Using 8K Evaluation software 3.0, the entire dataset was fitted to a 1:1 Langmuir coupled model (Karlsson, R. Roos, H. Fagerstam, L. Petersson, B., 1994. Methods Enzymology 6.99-110) to simultaneously obtain the motor association velocity (kon) and dissociation velocity (koff). Affinity was estimated from the quotient of the motor velocity constant (KD = koff / kon).

[0477] The same method, with appropriately adjusted parameters (e.g., antibody concentration) as those skilled in the art would understand, was performed for each test antibody. The results for each test antibody are summarized in the table below.

[0478] [Table 5]

[0479] The binding affinity of anti-HER3 / MET bispecific antibodies to His-tagged human HER3 (hHER3), His-tagged monkey HER3 (fasHER3), His-tagged human MET (hMET, Sino Biological, Inc., catalog number: 10692-H08H), or His-tagged monkey MET (fasMET, Sino Biological, Inc., catalog number: 90304-C08H) was tested using the same experimental procedure.

[0480] The purified antibody was captured on a Protein A chip (Series S Sensor Chip Protein A) for detection. 2 μg / mL of antibody was loaded at 10 μL / min and bound to hHER3, fasHER3, hMET, or fasMET (400 and 0 nM). The flow rate was 30 μL / min, and the binding and dissociation times were set to 180 seconds and 400 seconds, respectively. After the final injection of each titration, the chip was regenerated with glycine solution (pH 2.0) at 30 μL / min for 30 seconds. The results are summarized in the table below.

[0481] [Table 6]

[0482] The results demonstrate that anti-HER3 antibodies can bind to human, monkey, and canine HER3 with high affinity. Furthermore, all anti-HER3 / MET bispecific antibodies can bind to human HER3, monkey HER3, human MET, and monkey MET.

[0483] Example 6. Stability analysis of anti-HER3 antibody The biophysical properties and stability of anti-HER3 antibodies were evaluated. The antibody sample processing procedure was as follows: 1) The antibody was placed in a buffer solution containing 3 mg / mL histidine, 80 mg / mL sucrose, and 0.2 mg / mL Tween 80 at pH 6.0 until the final concentration reached 2 mg / mL. The solution was then stored in a sealed Eppendorf tube at 40±2°C and 60%±5% RH (hereinafter referred to as 40°C) for 7 days, and its thermal stability was evaluated.

[0484] 2) The antibody was loaded onto a Protein A column and eluted with a pH 3.5 buffer (0.1 mol / L HAc). Half of the antibody was added to 2 M Tris buffer and the pH was immediately adjusted to 7.5. The remaining half was stored at pH 3.5 for 6 hours, and then the pH was adjusted to 7.5. The diluted antibody was kept in a sealed Eppendorf tube at pH 3.5 ± 0.1, 25 ± 2°C (hereinafter referred to as pH 3.5) for 6 hours to test its stability at low pH.

[0485] 3) The antibody was placed in a buffer solution (3 mg / mL histidine, 80 mg / mL sucrose, and 0.2 mg / mL Tween 80), and H2O2 stock was added to achieve final concentrations of 0.05% and 0.5% H2O2 (hereinafter referred to as H2O20.05% and H2O20.5%). The samples were held in sealed Eppendorf tubes at 40±3°C and 60%±5% RH for 30 minutes to test their stability under strong oxidation conditions.

[0486] 4) The antibody was placed in a buffer solution (3 mg / mL histidine, 80 mg / mL sucrose, and 0.2 mg / mL Tween 80), and NH4HCO3 stock was added to achieve a final concentration of 0.94% NH4HCO3. The sample was held in a sealed Eppendorf tube at 40±2°C and 60%±5% RH for 6 hours (hereinafter referred to as NH4HCO3 6 hours) and then for 24 hours (hereinafter referred to as NH4HCO3 24 hours) to test its stability under strong deamidation conditions.

[0487] The following tests were performed: (1) Detection of antibody purity by size exclusion high-performance liquid chromatography (SEC-HPLC) (expressed as the ratio of main peak area to the sum of all peak areas (purity, %)), (2) Detection of apparent hydrophobicity of antibody using hydrophobic interaction chromatography - high-performance liquid chromatography (HIC-HPLC) (expressed as the retention time of the main peak (HIC, mins)), (3) Capillary electrophoresis under non-reducing (CE-SDS(NR)) conditions - Detection of changes in antibody purity by sodium dodecyl sulfate (CE-SDS) (expressed as the ratio of main peak area to the sum of all peak areas (purity, %)), (4) Detection of antibody pI (isoelectric point) and charge variants by capillary isoelectric focusing (cIEF) (expressed as the ratio of major component, acidic component, and alkaline component).

[0488] In the SEC-HPLC experiment, the antibody sample was diluted to 1 mg / mL with purified water and used with an Agilent 1290 chromatograph system (connected to an XBridge Protein BEH SEC column (200 Å, Waters Corporation)). The parameters used were as follows: mobile phase: 0.1 M phosphate buffer (PB) + 10% ACN, pH 7.4, flow rate: 1.8 mL / min, column temperature: 25°C, detection wavelengths: 280 nm, 220 nm, injection volume: 10 μL, sample tray temperature: approximately 4°C, and run time: 7 minutes.

[0489] In the HIC-HPLC experiment, an Agilent 1260 chromatograph system (connected to a ProPac HIC-10 column (4.6 × 250 mm, Thermo Scientific)) was used, and the sample was diluted 10-fold using mobile phase A. The parameters used were as follows: Mobile phase A: 0.9 M ammonium sulfate, 0.1 M phosphate buffer (PB), 10% acetonitrile pH 6.5; Mobile phase B: 0.1 M phosphate buffer (PB), 10% acetonitrile pH 6.5; Flow rate: 0.8 mL / min; Gradient: 0 min 100% A, 2 min 100% A, 32 min 100% B, 34 min 100% B, 35 min 100% A, 45 min 100% A; Column temperature: 30°C; Detection wavelengths: 280 nm, 220 nm; Injection volume: 10 μg; Sample tray temperature: approximately 10°C; Run time: 50 minutes.

[0490] For the CE-SDS(NR) experiment, the Maurice CE-SDS Size Application Kit (Protein simple, catalog number: PS-MAK03-S) was used. 60 μL of antibody sample (0.5 mg / mL), 2.4 μL of 25× internal standard, and 3 μL of 250 mM iodoacetamide (SIGMA, catalog number: 16125) were added to a microcentrifuge tube and subsequently centrifuged at 3000 rpm for 1 minute, followed by heating in a 70°C water bath for 10 minutes. Next, the sample was cooled to room temperature and subsequently centrifuged at 10000 rpm for 3 minutes. The supernatant sample preparation was then transferred to a 96-well plate and tested with the Maurice. The following parameters were used: injection voltage 4.6 kV, injection time 20 seconds, separation voltage 5.75 kV, and separation time 45 minutes.

[0491] For the cIEF experiment, the Maurice cIEF method development kit (Protein Simple, catalog number: PS-MDK01-C) was used for sample preparation. Specifically, 8 μL, 30 μg of protein sample was mixed in the kit with the following reagents: 1 μL of Maurice cIEF pI Marker-7.05, 1 μL of Maurice cIEF pI Marker-10.10, 35 μL of 1% methylcellulose solution, 2 μL of Maurice cIEF 500 mM arginine, 1.33 μL of Ampholytes (Pharmalyte pH range 3-10), and 6.66 μL of Ampholytes (Pharmalyte pH range 8-10.5), and water (added to a final volume of 100 μL). Imaging capillary isoelectric focusing spectra were generated using a Maurice analyzer (Protein Simple, Santa Clara, CA) with a Maurice cIEF cartridge (PS-MC02-C). The sample was focused for a total of 10 minutes.

[0492] The detailed results are shown in the table below. The results demonstrated that these anti-HER3 antibodies possessed excellent stability and physical and chemical properties.

[0493] [Table 7] TIFF2026510963000026.tif143166

[0494] Example 7. Generation of anti-HER3 antibody drug conjugates (ADCs) Each purified antibody (3E1, 3G6, 1B2, 1C5, 3E1-1C5, 3G6-1C5, 1B2-1C5, 1B2-8E2, 2F11-1B2, 2F11-1C5, 2F11-3E1, or 2F11-3G6) was coupled with MMAE (monomethyl auristatin E) or MMAF (monomethyl auristatin F) via a maleimidocaproyl-valine-citrulline-p-aminobenzyloxycarbonyl (VC) linker.

[0495] For the name of the antibody-drug conjugate, add "ADC" immediately after the antibody name. For example, when 3E1 is conjugated to MMAE, it is named 3E1-ADC. When 3E1-1C5 is conjugated to MMAE, it is named 3E1-1C5-ADC.

[0496] The patritumab analog and the terisotumab analog were also conjugated with MMAE, respectively, for positive controls. The conjugation of human IgG1 with MMAE was used for the ISO control (refer to ISO-ADC) in the following experiments.

[0497] HIC-HPLC was performed to detect the conjugation of the antibody and the drug molecule. The results showed that the drug-antibody ratio (DAR) of the ADC was approximately 4.

[0498] Example 8. Antitumor Activity of Anti-HER3 ADC in the NUGC-4 Model The antitumor activity of anti-HER3 ADC was determined using B-NDG mice (Biocytogen Pharmaceuticals (Beijing) Co., Ltd., catalog number: B-CM-002). Approximately 5×10 6 gastric cancer NUGC-4 cells were subcutaneously injected into B-NDG mice, and when the tumor volume grew to approximately 200 mm 3 , based on the tumor size, the mice were divided into different treatment groups from the control group (5 mice per group). The treatment groups were randomly injected with patritumab-ADC, 3E1-ADC, 3G6-ADC, or 1B2-ADC. The mice in the control group were injected with phosphate-buffered saline (PBS). The patritumab analog was conjugated with MMAE as a positive control (named patritumab-ADC). The dosing frequency was once a week (a total of 2 doses).

[0499] The tumor volume was measured twice a week, and the body weight of the mice was also measured. When the tumor volume of the mice reached 3000 mm 3 , euthanasia was performed. The details of the dosing scheme are shown in the following table.

[0500] [Table 8]

[0501] Measure the length of the long axis and short axis of the tumor, and calculate the tumor volume as 0.5 × (long axis) × (short axis). 2 The following formula was used for calculation. The tumor growth inhibition rate (TGI%) is calculated using the following formula: (TGI%) = [1 - (Ti - T0) / (Vi - V0)] × 100. Ti is the mean tumor volume in the treatment group on day i. T0 is the mean tumor volume in the treatment group on day 0. Vi is the mean tumor volume in the control group on day i. V0 is the mean tumor volume in the control group on day 0. A t-test was performed for statistical analysis. A TGI% greater than 60% indicates a clear suppression of tumor growth. P < 0.05 is the threshold for showing a statistically significant difference.

[0502] At the end of the experiment, there were no significant differences between the groups, and all mice survived, indicating that the tested ADC was well-tolerated and clearly non-toxic to mice.

[0503] The tumor size data for the antibody-treated group is shown in Figure 2. The table below summarizes the results of this experiment and includes tumor volume, mouse survival rate, tumor growth inhibition (TGI) values, and statistical differences (P-values) in tumor volume and body weight between the treatment group and the control group at the day of group assignment (day 0), 11 days after group assignment (day 11), and 18 days after group assignment (day 18).

[0504] [Table 9]

[0505] As shown in Figure 2 and the above table, compared with the control group (G1), tumor growth in the treatment groups (G2 - G5) was suppressed to varying degrees. Among the treatment groups, the 3E1 - ADC treatment group (G3), 3G6 ADC treatment group (G4), and 1B2 - ADC treatment group (G5) obtained better tumor inhibition effects compared with the positive control group (G2). After the 18th day, the tumor volume and survival rate of the mice were continuously monitored. When the tumor volume of the...

Claims

1. An antibody or antigen-binding fragment thereof that binds to HER3 (human epidermal growth factor receptor 3), A heavy chain variable region (VH) comprising complementarity-determining regions (CDRs) 1, 2, and 3, wherein the VH CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH CDR1, the VH CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH CDR2, and the VH CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH CDR3, and A light chain variable region (VL) comprising CDR1, 2, and 3, wherein the VL CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL CDR1, the VL CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL CDR2, and the VL CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL CDR3, and An antibody or antigen-binding fragment thereof, wherein the amino acid sequences of the selected VH CDR1, 2, and 3, and the amino acid sequences of the selected VL CDR1, 2, and 3, are one of the following: (1) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (2) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (3) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs: 10 to 12, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (4) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (5) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs: 16 to 18, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (6) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs: 22 to 24, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively. (7) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs. 25 to 27, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively. (8) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs. 28 to 30, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively. (9) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs: 31 to 33, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively, and (10) The amino acid sequences of the selected VH CDR1, 2, and 3 are shown in SEQ ID NOs: 34 to 36, respectively, and the amino acid sequences of the selected VL CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively.

2. Based on the definition of Kabat, the antibody or antigen-binding fragment thereof according to claim 1, wherein VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 4 to 6, and VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 1 to 3, respectively.

3. Based on the definition of Kabat, the antibody or antigen-binding fragment thereof according to claim 1, wherein VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 7 to 9, and VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 1 to 3, respectively.

4. Based on the definition of Kabat, the antibody or antigen-binding fragment thereof according to claim 1, wherein the VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 10 to 12, and the VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs: 1 to 3, respectively.

5. Based on the definition of Kabat, the antibody or antigen-binding fragment thereof according to claim 1, wherein VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 13 to 15, and VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 1 to 3, respectively.

6. Based on the definition of Kabat, the antibody or antigen-binding fragment thereof according to claim 1, wherein VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 16 to 18, and VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 1 to 3, respectively.

7. Based on the definition of Chothia, the antibody or antigen-binding fragment thereof according to claim 1, wherein VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 22 to 24, and VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 19 to 21, respectively.

8. Based on the definition of Chothia, the antibody or antigen-binding fragment thereof according to claim 1, wherein VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 25 to 27, and VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 19 to 21, respectively.

9. Based on the definition of Chothia, the antibody or antigen-binding fragment thereof according to claim 1, wherein VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 28 to 30, and VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 19 to 21, respectively.

10. Based on the definition of Chothia, the antibody or antigen-binding fragment thereof according to claim 1, wherein VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 31 to 33, and VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 19 to 21, respectively.

11. Based on the definition of Chothia, the antibody or antigen-binding fragment thereof according to claim 1, wherein VH comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 34 to 36, and VL comprises CDR1, 2, and 3 having the amino acid sequences shown in SEQ ID NOs. 19 to 21, respectively.

12. The antibody or antigen-binding fragment thereof according to any one of claims 1 to 11, wherein the antibody or antigen-binding fragment thereof specifically binds to human HER3, mouse HER3, monkey HER3, or canine HER3.

13. The antibody or antigen-binding fragment according to any one of claims 1 to 12, wherein the antibody or antigen-binding fragment thereof is a human antibody or antigen-binding fragment thereof, a single-chain variable fragment (scFv), a single-arm antibody, and / or a multispecific antibody (e.g., a bispecific antibody).

14. The antibody or antigen-binding fragment according to any one of claims 1 to 13, wherein the antibody or antigen-binding fragment is a human IgG1 antibody or its antigen-binding fragment, a human IgG2 antibody or its antigen-binding fragment, or a human IgG4 antibody or its antigen-binding fragment.

15. An antibody that binds to HER3 or an antigen-binding fragment thereof, An antibody or antigen-binding fragment comprising a heavy chain variable region (VH) containing an amino acid sequence that is at least 90% identical to a selected VH sequence, and a light chain variable region (VL) containing an amino acid sequence that is at least 90% identical to a selected VL sequence, wherein the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, the selected VL sequence is sequence number 37, and (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

16. The antibody or antigen-binding fragment thereof according to claim 15, wherein VH comprises the sequence of SEQ ID NO: 38 and VL comprises the sequence of SEQ ID NO:

37.

17. The antibody or antigen-binding fragment thereof according to claim 15, wherein VH comprises the sequence of SEQ ID NO: 39 and VL comprises the sequence of SEQ ID NO:

37.

18. The antibody or antigen-binding fragment thereof according to claim 15, wherein VH comprises the sequence of SEQ ID NO: 40 and VL comprises the sequence of SEQ ID NO:

37.

19. The antibody or antigen-binding fragment thereof according to claim 15, wherein VH comprises the sequence of SEQ ID NO: 41 and VL comprises the sequence of SEQ ID NO:

37.

20. The antibody or antigen-binding fragment thereof according to claim 15, wherein VH comprises the sequence of SEQ ID NO: 42 and VL comprises the sequence of SEQ ID NO:

37.

21. An antibody that binds to HER3 or an antigen-binding fragment thereof, An antibody or its antigen-binding fragment comprising a heavy chain variable region (VH) containing VH CDR1, VH CDR2, and VH CDR3 which are identical to VH CDR1, VH CDR2, and VH CDR3 of a selected VH sequence, and a light chain variable region (VL) containing VL CDR1, VL CDR2, and VL CDR3 which are identical to VL CDR1, VL CDR2, and VL CDR3 of a selected VL sequence, wherein the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, the selected VL sequence is sequence number 37, and (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

22. The antibody or antigen-binding fragment thereof according to any one of claims 1 to 21, wherein the antibody or antigen-binding fragment thereof specifically binds to human HER3, mouse HER3, monkey HER3, or canine HER3.

23. The antibody or antigen-binding fragment according to any one of claims 1 to 22, wherein the antibody or antigen-binding fragment thereof is a human antibody or antigen-binding fragment thereof, a single-chain variable fragment (scFv), a single-arm antibody, and / or a multispecific antibody (e.g., a bispecific antibody).

24. The antibody or antigen-binding fragment according to any one of claims 1 to 23, wherein the antibody or antigen-binding fragment is a human IgG1 antibody or its antigen-binding fragment, a human IgG2 antibody or its antigen-binding fragment, or a human IgG4 antibody or its antigen-binding fragment.

25. An antibody or antigen-binding fragment thereof, comprising a first antigen-binding domain that specifically binds to a first epitope of HER3, and a second antigen-binding domain that specifically binds to a second epitope of HER3.

26. The antibody or antigen-binding fragment thereof according to claim 25, wherein the first antigen-binding domain comprises a first heavy chain variable region (VH1) and a first light chain variable region (VL1), and the second antigen-binding domain comprises a second heavy chain variable region (VH2) and a second light chain variable region (VL2).

27. The first heavy chain variable region (VH1) includes complementarity-determining regions (CDRs) 1, 2, and 3, wherein the VH1 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR1, the VH1 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR2, and the VH1 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR3, and The first light chain variable region (VL1) includes CDR1, 2, and 3, wherein the VL1 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR1, the VL1 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR2, and the VL1 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR3. The antibody or antigen-binding fragment according to claim 26, wherein the amino acid sequences of the selected VH1 CDR1, 2, and 3, and the amino acid sequences of the selected VL1 CDR1, 2, and 3, are one of the following. (1) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (2) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (3) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 10 to 12, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (4) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (5) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 16 to 18, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (6) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 22 to 24, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively. (7) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 25 to 27, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively. (8) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 28 to 30, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively. (9) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 31 to 33, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively, and (10) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 34 to 36, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively.

28. The antibody or antigen-binding fragment thereof according to claim 27, wherein the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

29. The antibody or antigen-binding fragment thereof according to claim 27, wherein the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

30. The antibody or antigen-binding fragment thereof according to claim 2, wherein the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 10 to 12, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

31. The antibody or antigen-binding fragment thereof according to claim 27, wherein the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

32. The antibody or antigen-binding fragment thereof according to claim 27, wherein the amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 16 to 18, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively.

33. The second heavy chain variable region (VH2) includes CDR1, 2, and 3, wherein the VH2 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR1, the VH2 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR2, and the VH2 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR3, and The second light chain variable region (VL2) includes CDR1, 2, and 3, wherein the VL2 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR1, the VL2 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR2, and the VL2 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR3. The antibody or antigen-binding fragment according to any one of claims 26 to 32, wherein the amino acid sequences of the selected VH2 CDR1, 2, and 3, and the amino acid sequences of the selected VL2 CDR1, 2, and 3, are one of the following. (1) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (2) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (3) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 10 to 12, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (4) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (5) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 16 to 18, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (6) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 22 to 24, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively. (7) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 25 to 27, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively. (8) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 28 to 30, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively. (9) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 31 to 33, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively, and (10) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 34 to 36, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively.

34. The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively, the antibody or antigen-binding fragment according to any one of claims 26 to 33.

35. The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively, the antibody or antigen-binding fragment according to any one of claims 26 to 33.

36. The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 10 to 12, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively, the antibody or antigen-binding fragment according to any one of claims 26 to 33.

37. The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively, the antibody or antigen-binding fragment according to any one of claims 26 to 33.

38. The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 16 to 18, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively, the antibody or antigen-binding fragment according to any one of claims 26 to 33.

39. The antibody or antigen-binding fragment thereof according to claim 26 or claim 27, which is any of the following: (1) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (2) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 31 to 33, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 25 to 27, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively. (3) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 16 to 18, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (4) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 34 to 36, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 25 to 27, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively. (5) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; (6) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 22 to 24, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 25 to 27, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively.

40. The antibody or antigen-binding fragment thereof according to any one of claims 26 to 39, wherein the VH1 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VH sequence, and the VL1 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, the selected VL sequence is sequence number 37, and (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

41. The antibody or antigen-binding fragment thereof according to any one of claims 26 to 40, wherein the VH2 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VH sequence, and the VL2 comprises an amino acid sequence that is at least 80%, 85%, 90%, 95%, 99%, or 100% identical to the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, the selected VL sequence is sequence number 37, and (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

42. The antibody or antigen-binding fragment thereof according to claim 26 or claim 27, wherein the VH1 comprises VH1 CDR1, VH1 CDR2, and VH1 CDR3 which are identical to VH CDR1, VH CDR2, and VH CDR3 of the selected VH sequence, and the VL1 comprises VL1 CDR1, VL1 CDR2, and VL1 CDR3 which are identical to VL CDR1, VL CDR2, and VL CDR3 of the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, the selected VL sequence is sequence number 37, and (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

43. The antibody or antigen-binding fragment thereof according to claim 26 or claim 27, wherein the VH2 comprises VH2 CDR1, VH2 CDR2, and VH2 CDR3 which are identical to VH CDR1, VH CDR2, and VH CDR3 of the selected VH sequence, and the VL2 comprises VL2 CDR1, VL2 CDR2, and VL2 CDR3 which are identical to VL CDR1, VL CDR2, and VL CDR3 of the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, the selected VL sequence is sequence number 37, and (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

44. An antibody or an antigen-binding fragment thereof, comprising a first antigen-binding domain that specifically binds to HER3 and a second antigen-binding domain that specifically binds to MET.

45. The antibody or antigen-binding fragment thereof according to claim 44, wherein the first antigen-binding domain comprises a first heavy chain variable region (VH1) and a first light chain variable region (VL1), and the second antigen-binding domain comprises a second heavy chain variable region (VH2) and a second light chain variable region (VL2).

46. The first heavy chain variable region (VH1) includes complementarity-determining regions (CDRs) 1, 2, and 3, wherein the VH1 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR1, the VH1 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR2, and the VH1 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH1 CDR3, and The first light chain variable region (VL1) includes CDR1, 2, and 3, wherein the VL1 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR1, the VL1 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR2, and the VL1 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL1 CDR3. The antibody or antigen-binding fragment according to claim 45, wherein the amino acid sequences of the selected VH1 CDR1, 2, and 3, and the amino acid sequences of the selected VL1 CDR1, 2, and 3, are one of the following. (1) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (2) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (3) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 10 to 12, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (4) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (5) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 16 to 18, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (6) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 22 to 24, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively. (7) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 25 to 27, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively. (8) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs. 28 to 30, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively. (9) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 31 to 33, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively, and (10) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 34 to 36, respectively, and the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 19 to 21, respectively.

47. The second heavy chain variable region (VH2) includes CDR1, 2, and 3, wherein the VH2 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR1, the VH2 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR2, and the VH2 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VH2 CDR3, and The second light chain variable region (VL2) includes CDR1, 2, and 3, wherein the VL2 CDR1 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR1, the VL2 CDR2 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR2, and the VL2 CDR3 region includes an amino acid sequence that is at least 80% identical to the amino acid sequence of the selected VL2 CDR3. The antibody or antigen-binding fragment thereof according to claim 45 or claim 46, wherein the amino acid sequences of the selected VH2 CDR1, 2, and 3, and the amino acid sequences of the selected VL2 CDR1, 2, and 3, are one of the following. (1) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 51 to 53, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (2) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 54 to 56, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 1 to 3, respectively. (3) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 57 to 59, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively. (4) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 60 to 62, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively. (5) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 69 to 71, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (6) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 72 to 74, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (7) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 75 to 77, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively, and (8) The amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs. 78 to 80, respectively, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs. 19 to 21, respectively.

48. The antibody or antigen-binding fragment thereof according to any one of claims 45 to 47, which is one of the following: (1) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51 to 53, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (2) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51 to 53, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (3) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 10 to 12, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51 to 53, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (4) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51 to 53, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (5) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 16 to 18, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 51 to 53, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (6) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54 to 56, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (7) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54 to 56, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (8) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54 to 56, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (9) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 10 to 12, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54 to 56, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (10) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 16 to 18, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 54 to 56, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (11) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 69 to 71, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (12) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 69 to 71, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (13) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 69 to 71, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (14) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 4 to 6, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 72 to 74, respectively; and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively. (15) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 7 to 9, respectively; the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 72 to 74, respectively; the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, respectively; (16) The amino acid sequences of the selected VH1 CDR1, 2, and 3 are shown in SEQ ID NOs: 13 to 15, the amino acid sequences of the selected VL1 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3, the amino acid sequences of the selected VH2 CDR1, 2, and 3 are shown in SEQ ID NOs: 72 to 74, and the amino acid sequences of the selected VL2 CDR1, 2, and 3 are shown in SEQ ID NOs: 1 to 3.

49. The antibody or antigen-binding fragment thereof according to any one of claims 45 to 48, wherein the VH1 comprises an amino acid sequence that is at least 90% identical to the selected VH sequence, and the VL1 comprises an amino acid sequence that is at least 90% identical to the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 38, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 39, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 40, and the selected VL sequence is sequence number 37. (4) The selected VH sequence is sequence number 41, the selected VL sequence is sequence number 37, and (5) The selected VH sequence is sequence number 42, and the selected VL sequence is sequence number 37.

50. The antibody or antigen-binding fragment thereof according to any one of claims 45 to 49, wherein the VH2 comprises an amino acid sequence that is at least 90% identical to the selected VH sequence, the VL2 comprises an amino acid sequence that is at least 90% identical to the selected VL sequence, and the selected VH sequence and the selected VL sequence are one of the following. (1) The selected VH sequence is sequence number 63, and the selected VL sequence is sequence number 37. (2) The selected VH sequence is sequence number 64, and the selected VL sequence is sequence number 37. (3) The selected VH sequence is sequence number 81, and the selected VL sequence is sequence number 37, (4) The selected VH sequence is sequence number 82, and the selected VL sequence is sequence number 37.

51. An antibody or an antigen-binding fragment that cross-competes with the antibody or antigen-binding fragment described in any one of claims 1 to 50.

52. The antibody or antigen-binding fragment thereof according to any one of claims 1 to 51, wherein the antibody or antigen-binding fragment thereof includes a fragment crystallizable region (Fc region).

53. The antibody or antigen-binding fragment thereof according to claim 52, wherein the Fc region exhibits increased complement-dependent cell-mediated cytotoxicity (CDC) or antibody-dependent cell-mediated cytotoxicity (ADCC).

54. A nucleic acid containing a polynucleotide that codes for a polypeptide including the following: (1) An immunoglobulin heavy chain or fragment thereof comprising a heavy chain variable region (VH) comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs: 4 to 6, wherein the VH binds to HER3 when paired with a light chain variable region (VL) containing the amino acid sequence shown in SEQ ID NO: 37, (2) An immunoglobulin light chain or fragment thereof comprising a VL containing complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs: 1 to 3, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO: 38, (3) An immunoglobulin heavy chain or fragment thereof comprising a heavy chain variable region (VH) comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs: 7 to 9, wherein the VH binds to HER3 when paired with a light chain variable region (VL) containing the amino acid sequence shown in SEQ ID NO: 37, (4) An immunoglobulin light chain or fragment thereof comprising a VL containing complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which each contain the amino acid sequences shown in SEQ ID NOs: 1 to 3, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO: 39, (5) An immunoglobulin heavy chain or fragment thereof comprising a VH comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which include the amino acid sequences shown in SEQ ID NOs. 10 to 12, wherein the VH binds to HER3 when pairing with a light chain variable region (VL) comprising the amino acid sequence shown in SEQ ID NO.

37. (6) An immunoglobulin light chain or fragment thereof comprising a VL containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs: 1 to 3, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO:

40. (7) An immunoglobulin heavy chain or fragment thereof comprising a VH comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which include the amino acid sequences shown in SEQ ID NOs. 13 to 15, wherein the VH binds to HER3 when pairing with a light chain variable region (VL) comprising the amino acid sequence shown in SEQ ID NO.

37. (8) An immunoglobulin light chain or fragment thereof comprising a VL containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs: 1 to 3, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO: 41, (9) An immunoglobulin heavy chain or fragment thereof comprising a VH comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which include the amino acid sequences shown in SEQ ID NOs. 16 to 18, wherein the VH binds to HER3 when pairing with a light chain variable region (VL) comprising the amino acid sequence shown in SEQ ID NO.

37. (10) An immunoglobulin light chain or fragment thereof comprising a VL containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs: 1 to 3, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO: 42, (11) An immunoglobulin heavy chain or fragment thereof comprising a heavy chain variable region (VH) comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 22 to 24, wherein the VH binds to HER3 when paired with a light chain variable region (VL) containing the amino acid sequence shown in SEQ ID NO.

37. (12) An immunoglobulin light chain or fragment thereof comprising a VL containing complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 19 to 21, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO.

38. (13) An immunoglobulin heavy chain or fragment thereof comprising a heavy chain variable region (VH) comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 25 to 27, wherein the VH binds to HER3 when paired with a light chain variable region (VL) containing the amino acid sequence shown in SEQ ID NO.

37. (14) An immunoglobulin light chain or fragment thereof comprising a VL containing complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which contain the amino acid sequences shown in SEQ ID NOs. 19 to 21, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO.

39. (15) An immunoglobulin heavy chain or fragment thereof comprising a VH comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which include the amino acid sequences shown in SEQ ID NOs. 28 to 30, wherein the VH binds to HER3 when pairing with a light chain variable region (VL) comprising the amino acid sequence shown in SEQ ID NO.

37. (16) An immunoglobulin light chain or fragment thereof comprising a VL containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 19 to 21, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO.

40. (17) An immunoglobulin heavy chain or fragment thereof comprising a VH comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which comprises the amino acid sequences shown in SEQ ID NOs. 31 to 33, wherein the VH binds to HER3 when pairing with a light chain variable region (VL) comprising the amino acid sequence shown in SEQ ID NO.

37. (18) An immunoglobulin light chain or fragment thereof comprising a VL containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs: 19 to 21, wherein the VL binds to HER3 when paired with a VH containing the amino acid sequence shown in SEQ ID NO: 41, (19) An immunoglobulin heavy chain or fragment thereof comprising a VH comprising complementarity-determining regions (CDRs) 1, 2, and 3, respectively, which include the amino acid sequences shown in SEQ ID NOs. 34 to 36, wherein the VH binds to HER3 when pairing with a light chain variable region (VL) comprising the amino acid sequence shown in SEQ ID NO. 37, or (20) An immunoglobulin light chain or fragment thereof comprising a VL comprising CDR1, 2, and 3, each comprising the amino acid sequences shown in SEQ ID NOs: 19 to 21, wherein the VL binds to HER3 when pairing with a VH comprising the amino acid sequence shown in SEQ ID NO:

42.

55. The nucleic acid according to claim 54, wherein the nucleic acid comprises a polynucleotide encoding a polypeptide, and the polypeptide comprises an immunoglobulin light chain or fragment thereof, comprising a VL containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs: 1 to 3.

56. The nucleic acid according to claim 54, wherein the nucleic acid comprises a polynucleotide encoding a polypeptide, and the polypeptide comprises an immunoglobulin light chain or fragment thereof, comprising a VL containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 19 to 21.

57. The nucleic acid according to claim 54, wherein the nucleic acid comprises a polynucleotide encoding a polypeptide, and the polypeptide comprises an immunoglobulin heavy chain or a fragment thereof, comprising a VH containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs: 4 to 6.

58. The nucleic acid according to claim 54, wherein the nucleic acid comprises a polynucleotide encoding a polypeptide, and the polypeptide comprises an immunoglobulin heavy chain or a fragment thereof, comprising a VH containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 7 to 9.

59. The nucleic acid according to claim 54, wherein the nucleic acid comprises a polynucleotide encoding a polypeptide, and the polypeptide comprises an immunoglobulin heavy chain or a fragment thereof, comprising a VH including CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 10 to 12.

60. The nucleic acid according to claim 54, wherein the nucleic acid comprises a polynucleotide encoding a polypeptide, and the polypeptide comprises an immunoglobulin heavy chain or a fragment thereof, comprising a VH including CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 13 to 15.

61. The nucleic acid according to claim 54, wherein the nucleic acid comprises a polynucleotide encoding a polypeptide, and the polypeptide comprises an immunoglobulin heavy chain or a fragment thereof, comprising a VH including CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 16 to 18.

62. The nucleic acid according to claim 54, wherein the nucleic acid comprises a polynucleotide encoding a polypeptide, and the polypeptide comprises an immunoglobulin heavy chain or a fragment thereof, comprising a VH including CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 22 to 24.

63. The nucleic acid according to claim 54, wherein the nucleic acid comprises a polynucleotide encoding a polypeptide, and the polypeptide comprises an immunoglobulin heavy chain or a fragment thereof, comprising a VH containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 25 to 27.

64. The nucleic acid according to claim 54, wherein the nucleic acid comprises a polynucleotide encoding a polypeptide, and the polypeptide comprises an immunoglobulin heavy chain or a fragment thereof, comprising a VH including CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 28 to 30.

65. The nucleic acid according to claim 54, wherein the nucleic acid comprises a polynucleotide encoding a polypeptide, and the polypeptide comprises an immunoglobulin heavy chain or a fragment thereof, comprising a VH containing CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 31 to 33.

66. The nucleic acid according to claim 54, wherein the nucleic acid comprises a polynucleotide encoding a polypeptide, and the polypeptide comprises an immunoglobulin heavy chain or a fragment thereof, comprising a VH including CDR1, 2, and 3, each containing the amino acid sequences shown in SEQ ID NOs. 34 to 36.

67. The nucleic acid according to any one of claims 54 to 66, wherein the VH specifically binds to human HER3, mouse HER3, monkey HER3, or canine HER3 when pairing with VL, or the VL specifically binds to human HER3, mouse HER3, monkey HER3, or canine HER3 when pairing with VH.

68. The nucleic acid according to any one of claims 54 to 67, wherein the immunoglobulin heavy chain or fragment thereof is a human immunoglobulin heavy chain or fragment thereof (for example, a human IgG1 heavy chain or fragment thereof, a human IgG2 antibody or its antigen-binding fragment, or a human IgG4 heavy chain or fragment thereof), and the immunoglobulin light chain or fragment thereof is a human immunoglobulin light chain or fragment thereof.

69. The nucleic acid according to any one of claims 54 to 68, wherein the nucleic acid encodes a single-stranded variable fragment (scFv), a multispecific antibody (e.g., a bispecific antibody), or a chimeric antigen receptor (CAR).

70. The nucleic acid according to any one of claims 54 to 69, wherein the nucleic acid is cDNA.

71. A nucleic acid encoding an antibody or an antigen-binding fragment thereof according to any one of claims 1 to 53.

72. A vector comprising one or more nucleic acids as described in any one of claims 54 to 71.

73. A vector comprising two nucleic acids according to any one of claims 54 to 71, wherein the vector encodes the VL region and the VH region that bind together to HER3.

74. A pair of vectors, each vector comprising one of the nucleic acids described in any one of claims 54 to 71, wherein the pair of vectors encode the VL region and the VH region together which bind to HER3.

75. A cell comprising the vector according to claim 72 or 73, or the pair of vectors according to claim 74.

76. The cell according to claim 75, wherein the cell is a CHO cell.

77. A cell comprising one or more nucleic acids as described in any one of claims 54 to 71.

78. A method for producing an antibody or an antigen-binding fragment thereof, wherein the method is: (a) Culturing the cells according to any one of claims 75 to 77 under conditions sufficient for the cells to produce the antibody or the antigen-binding fragment, (b) recovering the antibody or antigen-binding fragment produced by the cells, method.

79. A chimeric antigen receptor (CAR) comprising an antibody or an antigen-binding fragment thereof as described in any one of claims 1 to 53.

80. An antibody-drug conjugate comprising an antibody or antigen-binding fragment thereof according to any one of claims 1 to 53, covalently bound to a therapeutic agent.

81. The antibody-drug conjugate according to claim 80, wherein the therapeutic agent is a cytotoxic agent or a cell proliferation inhibitor.

82. The antibody-drug conjugate according to claim 80 or 81, wherein the therapeutic agent is MMAE or MMAF.

83. The therapeutic agent is selected from the following, and is an antibody-drug conjugate according to claim 80. 【Chemistry 1】

84. The antibody-drug conjugate according to claim 80 or 83, wherein the therapeutic agent is linked to the antibody or its antigen-binding fragment via a linker.

85. The linker has the following structure, the antibody-drug conjugate according to any one of claims 80, 83, and 84. 【Chemistry 2】

86. The antibody-drug conjugate according to any one of claims 80 and 83 to 85, wherein the antibody-drug conjugate has the following structure. 【Transformation 3】 In the formula, n = 1, 2, 3, 4, 5, 6, 7, or 8, and "Ab" represents an antibody or its antigen-binding fragment.

87. A method for treating a subject having cancer, the method comprising administering to the subject a therapeutically effective amount of a composition comprising an antibody or antigen-binding fragment thereof according to any one of claims 1 to 53, a CAR according to claim 79, or an antibody-drug conjugate according to any one of claims 80 to 86.

88. The method according to claim 87, wherein the subject has a solid tumor.

89. The method according to claim 87, wherein the cancer is colorectal cancer, gastric cancer, breast cancer, lung cancer, melanoma, ovarian cancer, head and neck cancer, pancreatic cancer, liver cancer, or cervical cancer.

90. The method according to claim 87, wherein the subject is further treated with an effective amount of anti-4-1BB antibody, anti-OX40 antibody, anti-PD-1 antibody, anti-CTLA4 antibody, anti-CD40 antibody, or anti-PD-L1 antibody.

91. A method for reducing the rate of tumor growth, wherein the method is A method comprising contacting tumor cells with a composition comprising an effective amount of an antibody or antigen-binding fragment thereof according to any one of claims 1 to 53, a CAR according to claim 79, or an antibody-drug conjugate according to any one of claims 80 to 86.

92. A method for killing tumor cells, wherein the method is A method comprising contacting tumor cells with a composition comprising an effective amount of an antibody or antigen-binding fragment thereof according to any one of claims 1 to 53, a CAR according to claim 79, or an antibody-drug conjugate according to any one of claims 80 to 86.

93. A method for increasing the immune response in a target, wherein the method is A method comprising administering to the subject an effective amount of a composition comprising an antibody or antigen-binding fragment thereof according to any one of claims 1 to 53, a CAR according to claim 79, or an antibody-drug conjugate according to any one of claims 80 to 86.

94. A pharmaceutical composition comprising an antibody or antigen-binding fragment thereof according to any one of claims 1 to 53, and a pharmaceutically acceptable carrier.

95. A pharmaceutical composition comprising an antibody-drug conjugate according to any one of claims 80 to 86 and a pharmaceutically acceptable carrier.

96. The antibody-drug conjugate according to any one of claims 80 to 86, wherein the drug-antibody ratio (DAR) is approximately 4 or 8.

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