Ligand-cytotoxic drug conjugates and pharmaceutical uses thereof

Abstract

The invention discloses an antibody and a conjugate of the antibody and a small molecule drug. The antibody has the capability of high affinity binding with human antigen, and has better internalization characteristic. Also disclosed is the use of the ligand-cytotoxic drug conjugate and a pharmaceutical composition comprising the same in the preparation of a medicament for the treatment of cancer.

Description

Technical Field

[0001] The present invention relates to a novel HER3 antibody or a functional fragment thereof, which comprises an engineered heavy chain and a light chain. The present invention further relates to a conjugate of an improved HER3 antibody and a small molecule drug. The present invention further relates to the use of the antibody and the conjugate in the manufacture of a medicament for treating cancer. Background Art

[0002] Human epidermal growth factor receptor 3 (ErbB3, also known as HER3) is a tyrosine kinase receptor protein and belongs to the epidermal growth factor receptor (EGFR) subfamily of tyrosine kinase receptor proteins, which subfamily also includes EGFR (HER1, ErbB1), HER2 (ErbB2, Neu) and HER4 (ErbB4). In addition, HER3 is a unique member of the HER family, which has no or almost no intracellular tyrosine kinase activity but still plays a role in tumor progression and drug resistance.

[0003] Targeted therapies against HER family members such as EGFR and HER2 are widely and commonly used in cancer therapy by using monoclonal antibodies. However, due to the adaptive nature of cancer treatment, some cancer patients develop drug resistance after long-term treatment. For example, about 70% of patients are resistant to trastuzumab, an anti-HER2 antibody, and some patients even show primary drug resistance. Several studies have reported that strong expression of HER3 is observed after tumors develop resistance to trastuzumab treatment, and thus HER3 has become a promising target for overcoming existing obstacles. Previous studies have shown that HER3 expression is not only associated with metastatic events but also involved in the occurrence of drug resistance to other EGFR-targeted therapies (such as cetuximab, or kinase inhibitors such as lapatinib), IGFR-targeted therapies or chemotherapeutic agents.

[0004] Because HER3 has only minimal kinase activity, antibodies against HER3 are by far the most pursued strategy for targeting HER3. Many monoclonal antibodies against HER3 are undergoing preclinical and clinical development. Currently, the active antibodies are HMBD-001 (NCT05057013) from Hummingbird Bioscience; ISU104 (NCT03552406) from ISU Abxis Co., Ltd.; and SIBP-03 (NCT05203601) from Shanghai Institute of Biological Products. However, the fully human IgG2 mAb Seribantumab (from Merrimack, MM-121) in combination with paclitaxel or exemestane (an aromatase inhibitor) did not reach the phase 2 clinical endpoint of progression-free survival (PFS) in patients with HER3+ ovarian and breast cancers (NCT03241810). Additionally, in a phase 3 clinical study evaluating its efficacy against NSCLC, Patritumab (U3-1287 / AMG888) from Daiichi-Sankyo was tested together with erlotinib, and Patritumab also failed to meet the efficacy criteria (NCT02134015). Many HER3-targeted therapeutic antibodies have been tried in clinical trials to treat patients, but their efficacy can only be regarded as modest (J Exp Clin Cancer Res. October 21, 2022; 41(1):310). Therefore, there is an urgent need to incorporate new strategies to improve HER3-targeted antibody therapies.

[0005] Despite the promising results of the first-in-class ADC patritumab deruxtecan, the complex mechanisms regulating HER3 function in cancer patients make it necessary to further investigate novel and optimized therapeutic strategies against HER3. Therefore, there is a need to develop novel, effective, and safe products that modulate HER3 activity to treat HER3-related diseases; there is a need to incorporate more diverse components and combinations to develop more advanced anti-HER3 ADCs. The present invention provides a technical solution to meet this unmet need. Summary of the Invention

[0006] The anti-cancer efficacy of antibody-drug conjugates (ADCs) is thought to rely on the uptake of them by cancer cells expressing surface antigens, so insufficient internalization of monoclonal antibodies targeting HER3 is an urgent problem to be solved. All previous anti-HER3 antibodies were generated based on binding rather than internalization, which is crucial for ADCs. Additionally, all anti-HER3 antibodies were isolated by phage display technology or traditional murine hybridoma technology. We screened for fully human antibodies against HER3 using fully humanized mice, which is completely different from all previous anti-HER3 antibodies.

[0007] The technical problem to be solved by the present invention is to develop an advanced anti-HER3 ADC that exhibits a very strong anti-tumor effect in cancer. The anti-tumor effect can be enhanced by the following: improved binding affinity of the antibody, increased internalization for robust endocytosis, a higher DAR, and some potential effects of the ADC that are not inhibited by NRG1.

[0008] Specifically, the present invention encompasses the following aspects:

[0009] The present disclosure provides an antibody-drug conjugate of general formula (A) or a pharmaceutically acceptable salt or solvate thereof,

[0010] Ab-(L2-L1-D) y

[0011] (A)

[0012] Wherein:

[0013] D is a cytotoxic drug;

[0014] L1 and L2 are linking units;

[0015] y is a number from 1 to 20, preferably 2 to 10, more preferably 2 to 8, more preferably 2 to 6 or 4 to 8, and most preferably 2, 4, 6, 7, 8;

[0016] Ab is an anti-HER3 antibody or an antigen-binding fragment thereof, which comprises: a heavy-chain variable region of the antibody comprising HCDR1, HCDR2 and HCDR3 regions, and a light-chain variable region of the antibody comprising LCDR1, LCDR2 and LCDR3 regions, wherein: a) HCDR1 is as shown in SEQ ID NO: 01, SEQ ID NO: 02, SEQ ID NO: 03, SEQ ID NO: 04, SEQ ID NO: 05, SEQ ID NO: 06, SEQ ID NO: 07, SEQ ID NO: 08, SEQ ID NO: 09, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16 or SEQ ID NO: 17; b) HCDR2 is as shown in SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21, SEQ ID NO: 22, SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO: 32, SEQ ID NO: 33, SEQ ID NO: 34, SEQ ID NO: 35 or SEQ ID NO: 36; c) HCDR3 is as shown in SEQ ID NO: 37, SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 40, SEQ ID NO: 41, SEQ ID NO: 42, SEQ ID NO: 43, SEQ ID NO: 44, SEQ ID NO: 45, SEQ ID NO: 46, SEQ ID NO: 47, SEQ ID NO: 48, SEQ ID NO: 49, SEQ ID NO: 50, SEQ ID NO: 51, SEQ ID NO: 52, SEQ ID NO: 53, SEQ ID NO: 54, SEQ ID NO: 55, SEQ ID NO: 56, SEQ ID NO: 57 or SEQ ID NO: 58;d) LCDR1 is as shown in SEQ ID NO: 59, SEQ ID NO: 60, SEQ ID NO: 61, SEQ ID NO: 62, SEQ ID NO: 63, SEQ ID NO: 64, SEQ ID NO: 65, SEQ ID NO: 66, SEQ ID NO: 67, SEQ ID NO: 68, SEQ ID NO: 69, SEQ ID NO: 70, SEQ ID NO: 71, SEQ ID NO: 72, SEQ ID NO: 73, SEQ ID NO: 74, SEQ ID NO: 75 or SEQ ID NO: 76; e) LCDR2 is as shown in SEQ ID NO: 77, SEQ ID NO: 78, SEQ ID NO: 79, SEQ ID NO: 80, SEQ ID NO: 81, SEQ ID NO: 82, SEQ ID NO: 83, SEQ ID NO: 84, SEQ ID NO: 85, SEQ ID NO: 86 or SEQ ID NO: 87; f) LCDR3 is as shown in SEQ ID NO: 88, SEQ ID NO: 89, SEQ ID NO: 90, SEQ ID NO: 91, SEQ ID NO: 92, SEQ ID NO: 93, SEQ ID NO: 94, SEQ ID NO: 95, SEQ ID NO: 96, SEQ ID NO: 97, SEQ ID NO: 98, SEQ ID NO: 99, SEQ ID NO: 100, SEQ ID NO: 101, SEQ ID NO: 102, SEQ ID NO: 103 or SEQ ID NO: 104.

[0017] In some embodiments, the heavy chain variable region of Ab in formula (A) comprises: HCDR1 as shown in SEQ ID NO: 01, HCDR2 as shown in SEQ ID NO: 18, and HCDR3 as shown in SEQ ID NO: 37, respectively; or HCDR1 as shown in SEQ ID NO: 02, HCDR2 as shown in SEQ ID NO: 19, and HCDR3 as shown in SEQ ID NO: 38, respectively; or HCDR1 as shown in SEQ ID NO: 03, HCDR2 as shown in SEQ ID NO: 20, and HCDR3 as shown in SEQ ID NO: 39, respectively; or HCDR1 as shown in SEQ ID NO: 04, HCDR2 as shown in SEQ ID NO: 21, and HCDR3 as shown in SEQ ID NO: 40, respectively; or HCDR1 as shown in SEQ ID NO: 05, HCDR2 as shown in SEQ ID NO: 22, and HCDR3 as shown in SEQ ID NO: 41, respectively; or HCDR1 as shown in SEQ ID NO: 06, HCDR2 as shown in SEQ ID NO: 23, and HCDR3 as shown in SEQ ID NO: 42, respectively; or HCDR1 as shown in SEQ ID NO: 07, HCDR2 as shown in SEQ ID NO: 24, and HCDR3 as shown in SEQ ID NO: 43, respectively; or HCDR1 as shown in SEQ ID NO: 06, HCDR2 as shown in SEQ ID NO: 25, and HCDR3 as shown in SEQ ID NO: 44, respectively; or HCDR1 as shown in SEQ ID NO: 06, HCDR2 as shown in SEQ ID NO: 26, and HCDR3 as shown in SEQ ID NO: 45, respectively; or HCDR1 as shown in SEQ ID NO: 08, HCDR2 as shown in SEQ ID NO: 27, and HCDR3 as shown in SEQ ID NO: 46, respectively; or HCDR1 as shown in SEQ ID NO: 09, HCDR2 as shown in SEQ ID NO: 28, and HCDR3 as shown in SEQ ID NO: 47, respectively; or HCDR1 as shown in SEQ ID NO: 10, HCDR2 as shown in SEQ ID NO: 29, and HCDR3 as shown in SEQ ID NO: 48, respectively; or HCDR1 as shown in SEQ ID NO: 11, HCDR2 as shown in SEQ ID NO: 30, and HCDR3 as shown in SEQ ID NO: 49, respectively; or HCDR1 as shown in SEQ ID NO: 12, HCDR2 as shown in SEQ ID NO: 31, and HCDR3 as shown in SEQ ID NO: 50, respectively;or HCDR1 as shown in SEQ ID NO: 01, HCDR2 as shown in SEQ ID NO: 21, and HCDR3 as shown in SEQ ID NO: 51, respectively; or HCDR1 as shown in SEQ ID NO: 06, HCDR2 as shown in SEQ ID NO: 32, and HCDR3 as shown in SEQ ID NO: 52, respectively; or HCDR1 as shown in SEQ ID NO: 13, HCDR2 as shown in SEQ ID NO: 33, and HCDR3 as shown in SEQ ID NO: 53, respectively; or HCDR1 as shown in SEQ ID NO: 14, HCDR2 as shown in SEQ ID NO: 33, and HCDR3 as shown in SEQ ID NO: 54, respectively; or HCDR1 as shown in SEQ ID NO: 15, HCDR2 as shown in SEQ ID NO: 34, and HCDR3 as shown in SEQ ID NO: 55, respectively; or HCDR1 as shown in SEQ ID NO: 16, HCDR2 as shown in SEQ ID NO: 35, and HCDR3 as shown in SEQ ID NO: 56, respectively; or HCDR1 as shown in SEQ ID NO: 17, HCDR2 as shown in SEQ ID NO: 36, and HCDR3 as shown in SEQ ID NO: 57, respectively; or HCDR1 as shown in SEQ ID NO: 06, HCDR2 as shown in SEQ ID NO: 32, and HCDR3 as shown in SEQ ID NO: 58, respectively.;

[0018] In some embodiments, the light chain variable region of Ab in formula (A) comprises: LCDR1 as shown in SEQ ID NO: 59, LCDR2 as shown in SEQ ID NO: 77, and LCDR3 as shown in SEQ ID NO: 58, respectively; or LCDR1 as shown in SEQ ID NO: 60, LCDR2 as shown in SEQ ID NO: 78, and LCDR3 as shown in SEQ ID NO: 89, respectively; or LCDR1 as shown in SEQ ID NO: 61, LCDR2 as shown in SEQ ID NO: 77, and LCDR3 as shown in SEQ ID NO: 90, respectively; or LCDR1 as shown in SEQ ID NO: 59, LCDR2 as shown in SEQ ID NO: 77, and LCDR3 as shown in SEQ ID NO: 90, respectively; or LCDR1 as shown in SEQ ID NO: 62, LCDR2 as shown in SEQ ID NO: 77, and LCDR3 as shown in SEQ ID NO: 91, respectively; or LCDR1 as shown in SEQ ID NO: 63, LCDR2 as shown in SEQ ID NO: 79, and LCDR3 as shown in SEQ ID NO: 92, respectively; or LCDR1 as shown in SEQ ID NO: 60, LCDR2 as shown in SEQ ID NO: 80, and LCDR3 as shown in SEQ ID NO: 93, respectively; or LCDR1 as shown in SEQ ID NO: 64, LCDR2 as shown in SEQ ID NO: 81, and LCDR3 as shown in SEQ ID NO: 94, respectively; or LCDR1 as shown in SEQ ID NO: 65, LCDR2 as shown in SEQ ID NO: 82, and LCDR3 as shown in SEQ ID NO: 95, respectively; or LCDR1 as shown in SEQ ID NO: 60, LCDR2 as shown in SEQ ID NO: 80, and LCDR3 as shown in SEQ ID NO: 89, respectively; or LCDR1 as shown in SEQ ID NO: 66, LCDR2 as shown in SEQ ID NO: 83, and LCDR3 as shown in SEQ ID NO: 96, respectively; or LCDR1 as shown in SEQ ID NO: 67, LCDR2 as shown in SEQ ID NO: 79, and LCDR3 as shown in SEQ ID NO: 97, respectively; or LCDR1 as shown in SEQ ID NO: 68, LCDR2 as shown in SEQ ID NO: 77, and LCDR3 as shown in SEQ ID NO: 98, respectively; or LCDR1 as shown in SEQ ID NO: 69, LCDR2 as shown in SEQ ID NO: 84, and LCDR3 as shown in SEQ ID NO: 99, respectively;or LCDR1 as shown in SEQ ID NO: 70, LCDR2 as shown in SEQ ID NO: 85, and LCDR3 as shown in SEQ ID NO: 100, respectively; or LCDR1 as shown in SEQ ID NO: 71, LCDR2 as shown in SEQ ID NO: 85, and LCDR3 as shown in SEQ ID NO: 100, respectively; or LCDR1 as shown in SEQ ID NO: 61, LCDR2 as shown in SEQ ID NO: 77, and LCDR3 as shown in SEQ ID NO: 90, respectively; or LCDR1 as shown in SEQ ID NO: 72, LCDR2 as shown in SEQ ID NO: 86, and LCDR3 as shown in SEQ ID NO: 101, respectively; or LCDR1 as shown in SEQ ID NO: 73, LCDR2 as shown in SEQ ID NO: 82, and LCDR3 as shown in SEQ ID NO: 103, respectively; or LCDR1 as shown in SEQ ID NO: 64, LCDR2 as shown in SEQ ID NO: 82, and LCDR3 as shown in SEQ ID NO: 103, respectively; or LCDR1 as shown in SEQ ID NO: 74, LCDR2 as shown in SEQ ID NO: 79, and LCDR3 as shown in SEQ ID NO: 92, respectively; or LCDR1 as shown in SEQ ID NO: 75, LCDR2 as shown in SEQ ID NO: 82, and LCDR3 as shown in SEQ ID NO: 104, respectively; or LCDR1 as shown in SEQ ID NO: 65, LCDR2 as shown in SEQ ID NO: 82, and LCDR3 as shown in SEQ ID NO: 95, respectively; or LCDR1 as shown in SEQ ID NO: 76, LCDR2 as shown in SEQ ID NO: 85, and LCDR3 as shown in SEQ ID NO: 100, respectively; or LCDR1 as shown in SEQ ID NO: 66, LCDR2 as shown in SEQ ID NO: 83, and LCDR3 as shown in SEQ ID NO: 96, respectively.;

[0019] In a preferred embodiment, Ab in formula (A) comprises: a) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 08, SEQ ID NO: 27, and SEQ ID NO: 46, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 66, SEQ ID NO: 83, and SEQ ID NO: 96, respectively; or b) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 09, SEQ ID NO: 28, and SEQ ID NO: 47, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 67, SEQ ID NO: 79, and SEQ ID NO: 97, respectively; or c) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 10, SEQ ID NO: 29, and SEQ ID NO: 48, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 68, SEQ ID NO: 77, and SEQ ID NO: 98, respectively; or d) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 11, SEQ ID NO: 30, and SEQ ID NO: 49, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 69, SEQ ID NO: 84, and SEQ ID NO: 99, respectively; or e) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 12, SEQ ID NO: 31, and SEQ ID NO: 50, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 70, SEQ ID NO: 85, and SEQ ID NO: 100, respectively; or f) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 12, SEQ ID NO: 31, and SEQ ID NO: 50, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 71, SEQ ID NO: 85, and SEQ ID NO: 100, respectively; or g) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 01, SEQ ID NO: 21, and SEQ ID NO: 51, respectively;and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 61, SEQ ID NO: 77, and SEQ ID NO: 90, respectively; or h) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 06, SEQ ID NO: 32, and SEQ ID NO: 52, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 72, SEQ ID NO: 86, and SEQ ID NO: 101, respectively; or i) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 06, SEQ ID NO: 32, and SEQ ID NO: 52, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 73, SEQ ID NO: 87, and SEQ ID NO: 102, respectively; or j) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 13, SEQ ID NO: 33, and SEQ ID NO: 53, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 73, SEQ ID NO: 82, and SEQ ID NO: 103, respectively; or k) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 14, SEQ ID NO: 33, and SEQ ID NO: 54, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 64, SEQ ID NO: 82, and SEQ ID NO: 103, respectively; or l) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 15, SEQ ID NO: 34, and SEQ ID NO: 55, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 74, SEQ ID NO: 79, and SEQ ID NO: 92, respectively; or m) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 16, SEQ ID NO: 35, and SEQ ID NO: 56, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 75, SEQ ID NO: 82, and SEQ ID NO: 104, respectively;or n) a heavy chain variable region sequence comprising HCDR1, HCDR2 and HCDR3 as shown in SEQ ID NO: 16, SEQ ID NO: 35 and SEQ ID NO: 56 respectively; and a light chain variable region sequence comprising LCDR1, LCDR2 and LCDR3 as shown in SEQ ID NO: 65, SEQ ID NO: 82 and SEQ ID NO: 95 respectively; or o) a heavy chain variable region sequence comprising HCDR1, HCDR2 and HCDR3 as shown in SEQ ID NO: 17, SEQ ID NO: 36 and SEQ ID NO: 57 respectively; and a light chain variable region sequence comprising LCDR1, LCDR2 and LCDR3 as shown in SEQ ID NO: 76, SEQ ID NO: 85 and SEQ ID NO: 100 respectively; or p) a heavy chain variable region sequence comprising HCDR1, HCDR2 and HCDR3 as shown in SEQ ID NO: 06, SEQ ID NO: 32 and SEQ ID NO: 58 respectively; and a light chain variable region sequence comprising LCDR1, LCDR2 and LCDR3 as shown in SEQ ID NO: 66, SEQ ID NO: 83 and SEQ ID NO: 96 respectively; or q) a heavy chain variable region sequence comprising HCDR1, HCDR2 and HCDR3 as shown in SEQ ID NO: 01, SEQ ID NO: 18 and SEQ ID NO: 37 respectively; and a light chain variable region sequence comprising LCDR1, LCDR2 and LCDR3 as shown in SEQ ID NO: 59, SEQ ID NO: 77 and SEQ ID NO: 88 respectively; or r) a heavy chain variable region sequence comprising HCDR1, HCDR2 and HCDR3 as shown in SEQ ID NO: 02, SEQ ID NO: 19 and SEQ ID NO: 38 respectively; and a light chain variable region sequence comprising LCDR1, LCDR2 and LCDR3 as shown in SEQ ID NO: 60, SEQ ID NO: 78 and SEQ ID NO: 89 respectively; or s) a heavy chain variable region sequence comprising HCDR1, HCDR2 and HCDR3 as shown in SEQ ID NO: 03, SEQ ID NO: 20 and SEQ ID NO: 39 respectively; and a light chain variable region sequence comprising LCDR1, LCDR2 and LCDR3 as shown in SEQ ID NO: 61, SEQ ID NO: 77 and SEQ ID NO: 90 respectively; or t) a heavy chain variable region sequence comprising HCDR1, HCDR2 and HCDR3 as shown in SEQ ID NO: 04, SEQ ID NO: 21 and SEQ ID NO: 40 respectively;and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 59, SEQ ID NO: 77, and SEQ ID NO: 90, respectively; or u) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 05, SEQ ID NO: 22, and SEQ ID NO: 41, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 62, SEQ ID NO: 77, and SEQ ID NO: 91, respectively; or v) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 06, SEQ ID NO: 23, and SEQ ID NO: 42, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 63, SEQ ID NO: 79, and SEQ ID NO: 92, respectively; or w) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 07, SEQ ID NO: 24, and SEQ ID NO: 43, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 60, SEQ ID NO: 80, and SEQ ID NO: 93, respectively; or x) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 06, SEQ ID NO: 25, and SEQ ID NO: 44, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 64, SEQ ID NO: 81, and SEQ ID NO: 94, respectively; or y) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 06, SEQ ID NO: 26, and SEQ ID NO: 45, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 65, SEQ ID NO: 82, and SEQ ID NO: 95, respectively; or z) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 08, SEQ ID NO: 27, and SEQ ID NO: 46, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 60, SEQ ID NO: 80, and SEQ ID NO: 89, respectively;;

[0020] In a preferred embodiment, Ab in formula (A) is selected from murine antibodies, chimeric antibodies, humanized antibodies, human antibodies, or antigen-binding fragments thereof.

[0021] In some embodiments, Ab in formula (A) comprises a heavy chain variable region of the following sequences: SEQ ID NO: 127, 129, 131, 133, 135, 137, 139, 141, 144, 145, 147, 149, 151, 153, 155, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, and 125, or has at least 80%, 85%, 90%, 95%, or 99% sequence identity therewith.

[0022] In some embodiments, Ab in formula (A) comprises a light chain variable region of the following sequences: SEQ ID NO: 128, 130, 132, 134, 136, 138, 140, 142, 143, 146, 148, 150, 152, 154, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, and 126, or has at least 80%, 85%, 90%, 95%, or 99% sequence identity therewith.

[0023] In some embodiments, Ab in formula (A) comprises: a-1) a heavy chain variable region as shown in SEQ ID NO: 127 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; and / or a light chain variable region as shown in SEQ ID NO: 128 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; or a-2) a heavy chain variable region as shown in SEQ ID NO: 127 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; and / or a light chain variable region as shown in SEQ ID NO: 126 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; or b) a heavy chain variable region as shown in SEQ ID NO: 129 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; and / or a light chain variable region as shown in SEQ ID NO: 130 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; or c) a heavy chain variable region as shown in SEQ ID NO: 131 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; and / or a light chain variable region as shown in SEQ ID NO: 132 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; or d) a heavy chain variable region as shown in SEQ ID NO: 133 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; and / or a light chain variable region as shown in SEQ ID NO: 134 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; or e-1) a heavy chain variable region as shown in SEQ ID NO: 135 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; and / or a light chain variable region as shown in SEQ ID NO: 136 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; or e-2) a heavy chain variable region as shown in SEQ ID NO: 137 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; and / or a light chain variable region as shown in SEQ ID NO: 138 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; or f) a heavy chain variable region as shown in SEQ ID NO: 139 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; and / or a light chain variable region as shown in SEQ ID NO: 140 or having at least 80%, 85%, 90%, 95% or 99% sequence identity therewith;or g-1) a heavy chain variable region as shown in SEQ ID NO: 141 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 142 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or g-2) a heavy chain variable region as shown in SEQ ID NO: 141 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 143 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or g-3) a heavy chain variable region as shown in SEQ ID NO: 144 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 142 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or h) a heavy chain variable region as shown in SEQ ID NO: 145 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 146 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or i) a heavy chain variable region as shown in SEQ ID NO: 147 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 148 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or j) a heavy chain variable region as shown in SEQ ID NO: 149 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 150 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or k-1) a heavy chain variable region as shown in SEQ ID NO: 151 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 152 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or k-2) a heavy chain variable region as shown in SEQ ID NO: 151 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 122 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or l) a heavy chain variable region as shown in SEQ ID NO: 153 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto;and / or a light chain variable region as shown in SEQ ID NO: 154 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or m) a heavy chain variable region as shown in SEQ ID NO: 155 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 126 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or n) a heavy chain variable region as shown in SEQ ID NO: 105 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 106 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or o) a heavy chain variable region as shown in SEQ ID NO: 107 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 108 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or p) a heavy chain variable region as shown in SEQ ID NO: 109 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 110 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or q) a heavy chain variable region as shown in SEQ ID NO: 111 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 112 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or r) a heavy chain variable region as shown in SEQ ID NO: 113 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 114 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or s) a heavy chain variable region as shown in SEQ ID NO: 115 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 116 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or t) a heavy chain variable region as shown in SEQ ID NO: 117 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 118 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto;or u) a heavy chain variable region as set forth in SEQ ID NO: 119 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as set forth in SEQ ID NO: 120 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or v) a heavy chain variable region as set forth in SEQ ID NO: 121 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as set forth in SEQ ID NO: 122 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or w-1) a heavy chain variable region as set forth in SEQ ID NO: 123 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as set forth in SEQ ID NO: 124 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or w-2) a heavy chain variable region as set forth in SEQ ID NO: 125 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as set forth in SEQ ID NO: 126 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or x) a heavy chain variable region as set forth in SEQ ID NO: 123 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as set forth in SEQ ID NO: 126 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto.;

[0024] In a preferred embodiment, Ab in general formula (A) comprises: a-1) a heavy chain variable region as shown in SEQ ID NO: 127 and a light chain variable region as shown in SEQ ID NO: 128; a-2) a heavy chain variable region as shown in SEQ ID NO: 127 and a light chain variable region as shown in SEQ ID NO: 126; b) a heavy chain variable region as shown in SEQ ID NO: 129 and a light chain variable region as shown in SEQ ID NO: 130; c) a heavy chain variable region as shown in SEQ ID NO: 131 and a light chain variable region as shown in SEQ ID NO: 132; d) a heavy chain variable region as shown in SEQ ID NO: 133 and a light chain variable region as shown in SEQ ID NO: 134; e-1) a heavy chain variable region as shown in SEQ ID NO: 135 and a light chain variable region as shown in SEQ ID NO: 136; e-2) a heavy chain variable region as shown in SEQ ID NO: 137 and a light chain variable region as shown in SEQ ID NO: 138; f) a heavy chain variable region as shown in SEQ ID NO: 139 and a light chain variable region as shown in SEQ ID NO: 140; g-1) a heavy chain variable region as shown in SEQ ID NO: 141 and a light chain variable region as shown in SEQ ID NO: 142; g-2) a heavy chain variable region as shown in SEQ ID NO: 141 and a light chain variable region as shown in SEQ ID NO: 143; g-3) a heavy chain variable region as shown in SEQ ID NO: 144 and a light chain variable region as shown in SEQ ID NO: 142; h) a heavy chain variable region as shown in SEQ ID NO: 145 and a light chain variable region as shown in SEQ ID NO: 146; i) a heavy chain variable region as shown in SEQ ID NO: 147 and a light chain variable region as shown in SEQ ID NO: 148; j) a heavy chain variable region as shown in SEQ ID NO: 149 and a light chain variable region as shown in SEQ ID NO: 150; k-1) a heavy chain variable region as shown in SEQ ID NO: 151 and a light chain variable region as shown in SEQ ID NO: 152; k-2) a heavy chain variable region as shown in SEQ ID NO: 151 and a light chain variable region as shown in SEQ ID NO: 122; l) a heavy chain variable region as shown in SEQ ID NO: 153 and a light chain variable region as shown in SEQ ID NO: 154; m) a heavy chain variable region as shown in SEQ ID NO: 155 and a light chain variable region as shown in SEQ ID NO: 126; n) a heavy chain variable region as shown in SEQ ID NO: 105 and a light chain variable region as shown in SEQ ID NO: 106; o) a heavy chain variable region as shown in SEQ ID NO: 107 and a light chain variable region as shown in SEQ ID NO: 108;p) A heavy chain variable region as shown in SEQ ID NO: 109 and a light chain variable region as shown in SEQ ID NO: 110; q) A heavy chain variable region as shown in SEQ ID NO: 111 and a light chain variable region as shown in SEQ ID NO: 112; r) A heavy chain variable region as shown in SEQ ID NO: 113 and a light chain variable region as shown in SEQ ID NO: 114; s) A heavy chain variable region as shown in SEQ ID NO: 115 and a light chain variable region as shown in SEQ ID NO: 116; t) A heavy chain variable region as shown in SEQ ID NO: 117 and a light chain variable region as shown in SEQ ID NO: 118; u) A heavy chain variable region as shown in SEQ ID NO: 119 and a light chain variable region as shown in SEQ ID NO: 120; v) A heavy chain variable region as shown in SEQ ID NO: 121 and a light chain variable region as shown in SEQ ID NO: 122; w-1) A heavy chain variable region as shown in SEQ ID NO: 123 and a light chain variable region as shown in SEQ ID NO: 124; w-2) A heavy chain variable region as shown in SEQ ID NO: 125 and a light chain variable region as shown in SEQ ID NO: 126; x) A heavy chain variable region as shown in SEQ ID NO: 123 and a light chain variable region as shown in SEQ ID NO: 126.;

[0025] In some embodiments, the Ab in formula (A) is a full-length antibody, which further comprises a human antibody constant region; preferably, the heavy chain constant region of the human antibody constant region is selected from the constant regions of human IgG1, IgG2, IgG3, and IgG4 and their conservative variants, and the light chain constant region of the human antibody constant region is selected from the κ-chain constant region and λ-chain constant region of human antibodies and their conservative variants; more preferably, the full-length antibody comprises the human anti-body heavy chain constant region of SEQ ID NO: 156 and the human light chain constant region of SEQ ID NO: 157.

[0026] In a preferred embodiment, Ab in formula (A) comprises: a-1) a heavy chain as shown in SEQ ID NO: 180 and a light chain as shown in SEQ ID NO: 181; a-2) a heavy chain as shown in SEQ ID NO: 180 and a light chain as shown in SEQ ID NO: 179; b) a heavy chain as shown in SEQ ID NO: 182 and a light chain as shown in SEQ ID NO: 183; c) a heavy chain as shown in SEQ ID NO: 184 and a light chain as shown in SEQ ID NO: 185; g) a heavy chain as shown in SEQ ID NO: 186 and a light chain as shown in SEQ ID NO: 187; e-1) a heavy chain as shown in SEQ ID NO: 188 and a light chain as shown in SEQ ID NO: 189; e-2) a heavy chain as shown in SEQ ID NO: 190 and a light chain as shown in SEQ ID NO: 191; f) a heavy chain as shown in SEQ ID NO: 192 and a light chain as shown in SEQ ID NO: 193; g-1) a heavy chain as shown in SEQ ID NO: 194 and a light chain as shown in SEQ ID NO: 195; g-2) a heavy chain as shown in SEQ ID NO: 194 and a light chain as shown in SEQ ID NO: 196; g-3) a heavy chain as shown in SEQ ID NO: 197 and a light chain as shown in SEQ ID NO: 195; h) a heavy chain as shown in SEQ ID NO: 198 and a light chain as shown in SEQ ID NO: 199; i) a heavy chain as shown in SEQ ID NO: 200 and a light chain as shown in SEQ ID NO: 201; j) a heavy chain as shown in SEQ ID NO: 202 and a light chain as shown in SEQ ID NO: 203; k-1) a heavy chain as shown in SEQ ID NO: 204 and a light chain as shown in SEQ ID NO: 205; k-2) a heavy chain as shown in SEQ ID NO: 204 and a light chain as shown in SEQ ID NO: 175; l) a heavy chain as shown in SEQ ID NO: 206 and a light chain as shown in SEQ ID NO: 207; m) a heavy chain as shown in SEQ ID NO: 208 and a light chain as shown in SEQ ID NO: 179; n) a heavy chain as shown in SEQ ID NO: 158 and a light chain as shown in SEQ ID NO: 159; o) a heavy chain as shown in SEQ ID NO: 160 and a light chain as shown in SEQ ID NO: 161; p) a heavy chain as shown in SEQ ID NO: 162 and a light chain as shown in SEQ ID NO: 163; q) a heavy chain as shown in SEQ ID NO: 164 and a light chain as shown in SEQ ID NO: 165;r) a heavy chain as shown in SEQ ID NO: 166 and a light chain as shown in SEQ ID NO: 167; s) a heavy chain as shown in SEQ ID NO: 168 and a light chain as shown in SEQ ID NO: 169; t) a heavy chain as shown in SEQ ID NO: 170 and a light chain as shown in SEQ ID NO: 171; u) a heavy chain as shown in SEQ ID NO: 172 and a light chain as shown in SEQ ID NO: 173; v) a heavy chain as shown in SEQ ID NO: 174 and a light chain as shown in SEQ ID NO: 175; w-1) a heavy chain as shown in SEQ ID NO: 176 and a light chain as shown in SEQ ID NO: 177; w-2) a heavy chain as shown in SEQ ID NO: 178 and a light chain as shown in SEQ ID NO: 179; x) a heavy chain as shown in SEQ ID NO: 176 and a light chain as shown in SEQ ID NO: 179.

[0027] In some embodiments, the Ab in formula (A) is selected from: Fab, Fab', F(ab')2, variable fragment (Fv), single-chain variable fragment (scFv), dimeric domain V (diabody), disulfide-stabilized Fv (dsFv), and CDR-containing peptides.

[0028] In some embodiments, the cytotoxic drug is selected from toxins, chemotherapeutic agents, antibiotics, radioisotopes, and nucleases.

[0029] In additional embodiments, the cytotoxic drug is selected from tubulin inhibitors or topoisomerase inhibitors; preferably auristatin analogs or camptothecin derivatives; more preferably SN-38, MMAE, MMAF, or Exatecan.

[0030] In some embodiments, the antibody-drug conjugate is as shown in formula (B):

[0031]

[0032] Wherein:

[0033] L1 and L2 are linking units;

[0034] y is a number selected from 1 to 10, preferably a number selected from 2 to 8, more preferably a number from 2 to 6 or 4 to 8, further preferably a number from 6 to 8, and most preferably 4, 6, 7, 8;

[0035] Ab is the anti-HER3 antibody or antigen-binding fragment mentioned above.

[0036] In a preferred embodiment, the antibody-drug conjugate is as shown in general formula (C):

[0037]

[0038] Wherein:

[0039] L2 is a linking unit;

[0040] y is a number selected from 1 to 10, preferably a number selected from 2 to 8, more preferably a number from 2 to 6 or 4 to 8, further preferably a number from 6 to 8, and most preferably 4, 6, 7, 8;

[0041] R1 is selected from hydrogen, C 1-6 haloalkyl or C 3-8 cycloalkyl;

[0042] R2 is selected from hydrogen, C 1-6 haloalkyl or C 3-8 cycloalkyl;

[0043] Or, R1 and R2 together with the carbon atom to which they are attached form C 3-8 cycloalkyl.

[0044] Ab is the anti-HER3 antibody or antigen-binding fragment mentioned above.

[0045] In a preferred embodiment, the antibody-drug conjugate is as shown in general formula (C):

[0046]

[0047] Wherein:

[0048] L2 is a linking unit;

[0049] y is a number selected from 1 to 10, preferably a number selected from 2 to 8, more preferably a number from 2 to 6 or 4 to 8, further preferably a number from 6 to 8, and most preferably 4, 6, 7, 8;

[0050] R1 is selected from hydrogen, C 1-3 haloalkyl or C 3-6 cycloalkyl;

[0051] R2 is selected from hydrogen, C 1-3 haloalkyl or C 3-6 cycloalkyl;

[0052] Or, R1 and R2 together with the carbon atom to which they are attached form C 3-6 cycloalkyl.

[0053] Ab is the anti-HER3 antibody or antigen-binding fragment mentioned above.

[0054] In some embodiments, the linking unit L2 is as shown in general formula (I):

[0055]

[0056] Wherein:

[0057] s 1 and s 2 are each independently an integer selected from 0 - 8. Preferably, s 1 and s 2 are independently selected from 1, 2, 3, 4, 5 or 6;

[0058] Or, s 1 is an integer from 1 - 8 and s 2 is 0. Preferably, s 1 is selected from 4, 5, 6, 7 or 8 and s 2 is 0;

[0059] Or, s 2 is an integer selected from 2 to 8, s 1 is 2. Preferably, s 2 is selected from 2, 3, 4, 5 or 6 and s 1 is 2.

[0060] In a preferred embodiment, the antibody - drug conjugate has the following structure:

[0061]

[0062]

[0063]

[0064]

[0065] Wherein:

[0066] y is a number selected from 1 to 10, preferably a number selected from 2 to 8, more preferably a number from 2 to 6 or 4 to 8, further preferably a number from 6 to 8, and most preferably 4, 6, 7, 8;

[0067] Ab is the anti - HER3 antibody or antigen - binding fragment mentioned above.

[0068] In one aspect, the antibody - drug conjugate is selected from the following compounds:

[0069]

[0070]

[0071]

[0072]

[0073]

[0074] Wherein:

[0075] y is a number selected from 1 to 10, preferably a number selected from 2 to 8, more preferably a number from 2 to 6 or from 4 to 8, still more preferably a number from 6 to 8, and most preferably 4, 6, 7, 8.

[0076] The present disclosure further provides a method for preparing an antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof, the method comprising the following steps:

[0077]

[0078] coupling Ab with a compound after reduction to obtain an antibody-drug conjugate; wherein: Ab is the anti-HER3 antibody or antigen-binding fragment mentioned above;

[0079] R1 is selected from hydrogen, C 1-3 haloalkyl or C 3-6 cycloalkyl;

[0080] R2 is selected from hydrogen, C 1-3 haloalkyl or C 3-6 cycloalkyl;

[0081] or, R1 and R2 together with the carbon atom to which they are attached form a C 3-6 cycloalkyl;

[0082] L2 is the linker mentioned above;

[0083] y is a number selected from 1 to 10, preferably a number selected from 2 to 8, more preferably a number from 2 to 6 or from 4 to 8, still more preferably a number from 6 to 8, and most preferably 4, 6, 7, 8.

[0084] In some embodiments, the present disclosure provides a pharmaceutical composition comprising a ligand-drug conjugate or a pharmaceutically acceptable salt or solvate thereof according to the present disclosure, and one or more pharmaceutically acceptable excipients, diluents or carriers.

[0085] In some embodiments, the present disclosure also provides a method for treating or preventing a HER3-related disease, which comprises administering a therapeutically effective amount of an antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof according to the present disclosure, or a pharmaceutical composition, to a subject in need of treatment or prevention of said disease.

[0086] In some embodiments, the disease is a cancer having HER3 expression. Preferably, the cancer is breast cancer, colorectal cancer, lung cancer, multiple myeloma, ovarian cancer, liver cancer, gastric cancer, pancreatic cancer, prostate cancer, acute myeloid leukemia, chronic myeloid leukemia, osteosarcoma, squamous cell carcinoma, peripheral nerve sheath tumor, schwannoma, head and neck cancer, bladder cancer, esophageal cancer, glioblastoma, soft tissue clear cell sarcoma, malignant mesothelioma, neurofibromatosis, renal cancer, and melanoma.

[0087] In some embodiments, the present disclosure also provides the use of the antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof and the pharmaceutical composition in the manufacture of a medicament for treating or preventing a disease associated with HER3.

[0088] In some embodiments, the present disclosure also provides the use of the antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof and the pharmaceutical composition in the manufacture of a medicament for treating or preventing a cancer having HER3 expression; preferably, the cancer is breast cancer, colorectal cancer, lung cancer, multiple myeloma, ovarian cancer, liver cancer, gastric cancer, pancreatic cancer, prostate cancer, acute myeloid leukemia, chronic myeloid leukemia, osteosarcoma, squamous cell carcinoma, peripheral nerve sheath tumor, schwannoma, head and neck cancer, bladder cancer, esophageal cancer, glioblastoma, soft tissue clear cell sarcoma, malignant mesothelioma, neurofibromatosis, renal cancer, and melanoma.

[0089] The obtained antibody or ADC has a series of excellent characteristics:

[0090] i) The variable region sequence is different from existing antibodies; all of our antibodies are fully human antibodies, which have a lower tendency to cause immunogenicity in humans.

[0091] ii) The obtained antibody has the ability to bind to humans with high affinity, which has been confirmed by flow cytometry and ELISA.

[0092] iii) The obtained antibody has better internalization characteristics for constructing ADCs.

[0093] iv) Compared with pertuzumab-DXd, the payload of this ADC has better IC 50 .

[0094] v) When HER3 heterodimerizes with HER2 in the presence of NRG1, the cytotoxicity of this ADC can be unimpeded. BRIEF DESCRIPTION OF THE DRAWINGS

[0095] Figure 1 . In vitro binding characterization of HER3 hybridoma clones with HER3+(T47D) and HER3-(Jurkat E6.1) cell lines was performed using flow cytometry analysis.

[0096] Figure 2 . The cellular internalization activity of the selected hybridoma clones was characterized using an indirect killing assay.

[0097] Figure 3 . Internalization assay of anti-HER3 recombinant antibody in HER3+CHO-K1-huHER3 cells.

[0098] Figure 4 . The in vitro cytotoxic activity of the ADC against different tumor cell lines (A and B, HCC1569 cells; C, MX-1 cells), as determined by CellTiter-Glo luminescent viability assay.

[0099] Figure 5 . Cell binding of HER3 recombinant antibody and HER3 ADC killing assay in NRG competition.

[0100] Figure 6 . In vivo efficacy of ADC (3 mg / kg, QW) in HCC1569 / MX-1 tumor xenograft mouse model.

[0101] Figure 7 . In vivo efficacy of ADC (2 mg / kg or 6 mg / kg, QW) in MX-1 tumor xenograft mouse model.

[0102] Figure 8 . In vivo efficacy of ADC (3 mg / kg, QW) in MX-1 tumor xenograft mouse model. Detailed Description

[0103] The present invention is based on the development of an antibody that can specifically bind to HER3. The antibody of the present invention can optionally be conjugated with a growth inhibitor or a cytotoxic agent (such as a toxin, including for example irinotecan or irinotecan derivatives).

[0104] The headings used in this section are for convenience of description only and do not limit the present invention. Unless otherwise defined herein, scientific and technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, unless the context specifically requires otherwise, the singular forms include the plural forms, and the plural forms include the singular forms. Abbreviations of amino acid residues are the standard three-letter and / or one-letter codes used in the art, which represent one of the 20 common L-amino acids.

[0105] Definitions

[0106] The term "antibody" refers to a glycoprotein comprising at least two heavy (H) chains and two light (L) chains that are inter-connected by disulfide bonds, or an antigen-binding portion thereof. Each heavy chain is composed of a heavy chain variable region (abbreviated herein as VH) and a heavy chain constant region. Each light chain is composed of a light chain variable region (abbreviated herein as VL) and a light chain constant region. The VH and VL regions can be further subdivided into hypervariable regions called complementarity determining regions (CDRs), interspersed with more conserved regions called framework regions (FRs). Each VH and VL is composed of three CDRs and four FRs, which are arranged in the following order from the amino-terminus to the carboxy-terminus: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. The variable regions of the heavy and light chains contain binding domains that interact with an antigen. The constant region of the antibody can mediate the binding of the immunoglobulin to host tissues or factors, including various cells of the immune system (e.g., effector cells) and the first component of the classical complement system (C1q).

[0107] As used herein, the term "antigen-binding fragment" of an antibody refers to one or more fragments of an antibody that retain the ability to specifically bind to an antigen (e.g., HER3). It has been shown that the antigen-binding function of an antibody can be achieved by fragments of a full-length antibody. Examples of binding fragments encompassed by the term "antigen-binding fragment" of an antibody include: (i) Fab fragment, a monovalent fragment consisting of the VL, VH, CL, and CH1 domains; (ii) F(ab')2 fragment, a divalent fragment containing two Fab fragments linked by a disulfide bond in the hinge region; (iii) Fd fragment, which consists of the VH and CH1 domains; (iv) Fv fragment, which consists of the VL and VH domains of a single arm of an antibody; (v) dAb fragment (Ward et al., (1989) Nature 341:544-546), which consists of the VH domain; (vi) isolated complementarity determining regions (CDRs); and (vii) combinations of two or more isolated CDRs, which may optionally be linked by a synthetic linker. In addition, although the two domains VL and VH of an Fv fragment are encoded by separate genes, they can be joined together by recombinant methods using a synthetic linker such that they can be made into a single protein chain, wherein the VL and VH regions pair to form a monovalent molecule (called single-chain Fv (scFv); see, e.g., Bird et al. (1988) Science 242:423-426; and Huston et al. (1988) Proc. Natl. Acad. Sci. 85:5879-5883). Such single-chain antibodies are also intended to be encompassed by the term "antigen-binding portion" of an antibody.

[0108] As used herein, the term "human antibody" is intended to include antibodies having variable and constant regions derived from human germline immunoglobulin sequences. The human antibodies of the invention may contain amino acid residues not encoded by human germline immunoglobulin sequences (e.g., mutations introduced by in vitro random or site-specific mutagenesis or by in vivo somatic mutation). However, as used herein, the term "human antibody" is not intended to include antibodies in which CDR sequences derived from the germline of another mammalian species, such as a mouse, have been grafted onto human framework sequences.

[0109] As used herein, the term "recombinant human antibody" includes all human antibodies prepared, expressed, produced, or isolated by recombinant means, such as (a) antibodies isolated from transgenic or transchromosomal animals (e.g., mice) that have human immunoglobulin genes or from hybridomas prepared therefrom (further described in Section I below), (b) antibodies isolated from a host cell transformed to express an antibody (e.g., isolated from a transfectoma), (c) antibodies isolated from a recombinant combinatorial human antibody library, and (d) antibodies prepared, expressed, produced, or isolated by any other means that involve splicing human immunoglobulin gene sequences to other DNA sequences. Such recombinant human antibodies have variable and constant regions derived from human germline immunoglobulin sequences. However, in certain embodiments, such recombinant human antibodies may be mutagenized in vitro (or, when using animals transgenic for human Ig sequences, by in vivo somatic mutagenesis), and thus the amino acid sequences of the VH and VL regions of the recombinant antibody are sequences that, although derived from and related to human germline VH and VL sequences, may not be those present in the human antibody germline repertoire in vivo.

[0110] The term "CDR" refers to one of the six hypervariable regions within an antibody variable domain that contribute primarily to antigen binding. One of the most commonly used definitions of the six CDRs is provided by Kabat E.A. et al. (1991) Sequences of proteins of immunological interest. NIH Publication 91-3242. As used herein, the Kabat definition of CDR applies only to CDR1, CDR2, and CDR3 of the light chain variable domain (LCDR1, LCDR2, LCDR3 or L1, L2, L3), and CDR1, CDR2, and CDR3 of the heavy chain variable domain (HCDR1, HCDR2, HCDR3 or H1, H2, H3).

[0111] Methods and techniques for identifying CDRs within HCVR and LCVR amino acid sequences are well known in the art and can be used to identify CDRs within the specified HCVR and / or LCVR amino acid sequences disclosed herein. Exemplary conventions that can be used to identify CDR boundaries include, for example, Chothia (Chothia et al. (1989) Nature 342:877-883), which is based on the three-dimensional structure of the antibody and the topology of the CDR loops, Kabat (Kabat et al., Sequences of Proteins of Immunological Interest, 4th ed., US Department of Health and Human Services, National Institutes of Health (1987)), AbM (University of Bath), Contact (University College London), the international ImMunoGeneTics database (IMGT) (imgt.cines.fr / on the World Wide Web), and the North CDR definition based on affinity propagation clustering using a large number of crystal structures. A person skilled in the art can readily identify the CDRs defined by each numbering system.

[0112] A useful comparison of CDR numbering is as follows:

[0113] CDR IMGT Kabat AbM <![CDATA[Chothia 1 > <![CDATA[Contact 2 > LCDR1 27-32 24-34 24-34 24-34 30-36 LCDR2 50-51 50-56 50-56 50-56 46-55 LCDR3 89-97 89-97 89-97 89-97 89-96 HCDR1 26-35B <![CDATA[31 - 35B (Kabat number) 3 > 26-35B 26-32..34 30-35B HCDR2 51-56 50-65 50-58 52-56 47-58 HCDR3 93-102 95-102 95-102 95-102 93-101 HCDR1 26-33 31 - 35 (Chothia numbering) 26-35 26-32 30-35

[0114] Note 1 : Some of these definitions (especially for Chothia loops) vary depending on the individual publications examined; Note 2 : Any numbering scheme can be used for these CDR definitions, except for the contact definition, which uses the Chothia or Martin (enhanced Chothia) definition; Note 3 : When numbering using the Kabat numbering convention, the end of the Chothia HCDR1 loop varies between H32 and H34, depending on the length of the loop. This is because the Kabat numbering scheme places insertions at H35A and H35B.

[0115] As used herein, the term "nucleic acid molecule" refers to DNA molecules and RNA molecules. Nucleic acid molecules can be single-stranded or double-stranded, but are preferably double-stranded DNA. A nucleic acid is "operably linked" when placed into a functional relationship with another nucleic acid sequence. For example, a promoter or enhancer is operably linked to a coding sequence if it affects the transcription of the coding sequence.

[0116] The method for preparing nucleic acids is a conventional preparation method in the art. Preferably, it includes the following steps: obtaining a nucleic acid molecule encoding the above-mentioned protein through gene cloning technology, or obtaining a nucleic acid molecule encoding the above-mentioned protein through the method of artificial full-length sequence synthesis.

[0117] Those skilled in the art know that the base sequence encoding the amino acid sequence of a protein can be appropriately substituted, deleted, altered, inserted or added to provide polynucleotide homologues. Homologues of the polynucleotides of the present invention can be prepared by substituting, deleting or adding one or more bases of the gene encoding the protein sequence within the range of maintaining antibody activity.

[0118] The term "ligand" is a macromolecular compound that can recognize and bind to a target cell-related antigen or receptor. The role of the ligand is to deliver a drug to the population of target cells that bind to the ligand. Ligands include, but are not limited to, protein hormones, lectins, growth factors, antibodies, and other molecules capable of binding to cells. In an embodiment of the present invention, the ligand is designated as Ab. A linking bond can be formed between the heteroatoms and the linking unit in the ligand.

[0119] As used herein, the term "linking unit" refers to the part that links an antibody to a drug in an antibody-drug conjugate (i.e., ADC), which can be cleavable or non-cleavable. A cleavable linker (i.e., a cleavable or biodegradable linker) can be disrupted in or on the target cell, and thereby release the drug. In some embodiments, the linking unit or linker of the present invention has very good stability and greatly reduces drug release during delivery to the target (e.g., in the blood), thereby reducing side effects and toxicity. In some specific embodiments, the linking unit or linker of the present invention is selected from cleavable linkers, such as disulfide-based linkers (which are selectively disrupted in tumor cells at a higher thiol concentration), peptide linkers (which are cleaved by enzymes in tumor cells), and hydrazone linkers.

[0120] The term "cytotoxic drug" refers to a chemical molecule that can strongly disrupt the normal growth of tumor cells. In principle, a cytotoxic drug can kill tumor cells at a sufficiently high concentration, but due to lack of specificity, when killing tumor cells, it also causes apoptosis of normal cells, resulting in serious side effects. In an embodiment of the present invention, the cytotoxic drug is designated as D, and non-limiting examples include tubulin inhibitors, DNA alkylating agents, tyrosine kinase inhibitors, topoisomerase inhibitors, and DNA synthesis inhibitors, preferably topoisomerase inhibitors.

[0121] The term "ligand-cytotoxic drug conjugate" refers to a ligand linked to a bioactive drug via a linker unit. In some specific embodiments, the "ligand-cytotoxic drug conjugate" is preferably an antibody-drug conjugate (ADC), which refers to a monoclonal antibody or antibody fragment linked to a bioactive cytotoxic drug via a linker unit.

[0122] The term "drug-to-antibody ratio (DAR)" refers to the average number of cytotoxic drugs loaded on each ligand and can also be expressed as the ratio of the amount of drug to the amount of antibody. It can be an integer or a non-integer. The drug loading range for each ligand (Ab) can be from 1 to 20 cytotoxic drugs (D). In the embodiments of the present invention, the drug-to-antibody ratio is denoted as y, where y is a number selected from 1 to 10, preferably a number selected from 2 to 8, more preferably a number from 2 to 4, 2 to 6, 4 to 6, 4 to 8, 6 to 8, further preferably a number from 4 to 8 or 6 to 8, and most preferably 4, 5, 6, 7 or 8. The average number of drugs in each ADC molecule after the conjugation reaction can be identified by conventional methods, such as ultraviolet / visible spectroscopy, mass spectrometry, ELISA testing, and HPLC characterization.

[0123] The term "alkyl" refers to a saturated aliphatic hydrocarbon group, which is a straight-chain or branched-chain group containing 1 to 20 carbon atoms, preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, and most preferably an alkyl group having 1 to 6 carbon atoms (having 1, 2, 3, 4, 5, or 6 carbon atoms). Non-limiting examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, 2-methylbutyl, 3-methylbutyl, n-hexyl, 1-ethyl-2-methylpropyl, 1,1,2-trimethylpropyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 2,2-dimethylbutyl, 1,3-dimethylbutyl, 2-ethylbutyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 2,3-dimethylbutyl, n-heptyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, 5-methylhexyl, 2,3-dimethylpentyl, 2,4-dimethylpentyl, 2,2-dimethylpentyl, 3,3-dimethylpentyl, 2-ethylpentyl, 3-ethylpentyl, n-octyl, 2,3-dimethylhexyl, 2,4-dimethylhexyl, 2,5-dimethylhexyl, 2,2-dimethylhexyl, 3,3-dimethylhexyl, 4,4-dimethylhexyl, 2-ethylhexyl, 3-ethylhexyl, 4-ethylhexyl, 2-methyl-2-ethylpentyl, 2-methyl-3-ethylpentyl, N-nonyl, 2-methyl-2-ethylhexyl, 2-methyl-3-ethylhexyl, 2,2-diethylpentyl, n-decyl, 3,3-diethylhexyl, 2,2-diethylhexyl, and their various branched isomers. More preferably, the alkyl is a lower alkyl having 1 to 6 carbon atoms, and non-limiting examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, 2-methylbutyl, 3-methylbutyl, n-hexyl, 1-ethyl-2-methylpropyl, 1,1,2-trimethylpropyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 2,2-dimethylbutyl, 1,3-dimethylbutyl, 2-ethylbutyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 2,3-dimethylbutyl, etc. The alkyl can be substituted or unsubstituted. When substituted, the substituents can be substituted at any available attachment point. The substituents are preferably independently selected from one or more of the following groups: alkyl, alkenyl, alkynyl, alkoxy, alkylthio, alkylamino, halogen, thiol, hydroxy, nitro, cyano, cycloalkyl, heterocyclic, aryl, heteroaryl, cycloalkoxy, heterocycloalkoxy, cycloalkylthio, heterocyclothio, and oxo.

[0124] The term "haloalkyl" refers to an alkyl group substituted with one or more halogens, wherein the alkyl is as defined above.

[0125] The term "cycloalkyl" refers to a saturated or partially unsaturated monocyclic or polycyclic hydrocarbon substituent having from 3 to 20 carbon atoms, preferably from 3 to 12 carbon atoms, more preferably from 3 to 10 carbon atoms, and most preferably from 3 to 8 carbon atoms (having 3, 4, 5, 6, 7, or 8 carbon atoms). Non-limiting examples of monocyclic cycloalkyls include cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cyclohexadienyl, cycloheptyl, cycloheptatrienyl, cyclooctyl, etc. Polycyclic cycloalkyls include cycloalkyls having spiro, fused, or bridged rings.

[0126] As used herein, the term "transfectoma" includes recombinant eukaryotic host cells that express an antibody, such as CHO cells, NS / 0 cells, HEK293 cells, plant cells, or fungi (including yeast cells).

[0127] The DNA molecule sequence of an antibody or its fragment according to the present invention can be obtained by conventional techniques (e.g., methods such as PCR amplification or genomic library screening). In addition, the sequences encoding the light chain and the heavy chain can be fused together to form a single-chain antibody.

[0128] Once the relevant sequence is obtained, the relevant sequence can be obtained in batches using recombinant methods. This is generally carried out by: by conventional methods, cloning the sequence into a vector, transforming cells with the vector, and then separating the relevant sequence from the proliferating host cells.

[0129] In addition, the relevant sequence can be synthesized artificially, especially when the fragment length is short. Generally, several small fragments are first synthesized and then ligated together to obtain a long sequence fragment.

[0130] Currently, the DNA sequence encoding the antibody (or its fragment or its derivative) of the present invention can be obtained entirely by chemical synthesis. Then the DNA sequence can be introduced into various existing DNA molecules (or e.g., vectors) and cells known in the art. In addition, mutations can be introduced into the protein sequence of the present invention by chemical synthesis.

[0131] Generally, host cells are cultured under conditions suitable for expressing the antibody according to the present invention. Then, the antibody of the present invention is purified by using conventional immunoglobulin purification steps, such as conventional separation and purification means well known to those skilled in the art, such as protein A-agarose, hydroxyapatite chromatography, gel electrophoresis, dialysis, ion exchange chromatography, hydrophobic chromatography, molecular sieve chromatography, or affinity chromatography.

[0132] Monoclonal antibodies that can be obtained by conventional means of identification. For example, the binding specificity of monoclonal antibodies can be determined by immunoprecipitation or in vitro binding assays (such as radioimmunoassay (RIA) or enzyme-linked immunosorbent assay (ELISA)). The binding affinity of monoclonal antibodies can be determined by, for example, Scatchard analysis (Munson et al., Anal. Biochem., 107:220 (1980)).

[0133] The antibodies according to the present invention can be expressed in cells or on cell membranes, or secreted extracellularly. If necessary, the recombinant protein can be isolated and purified by various separation methods according to the physical, chemical and other properties of the recombinant protein. These methods are well known to those skilled in the art. Examples of these methods include, but are not limited to: conventional renaturation treatment, treatment with protein precipitants (such as salt precipitation), centrifugation, cell lysis by osmosis, sonication, ultracentrifugation, molecular sieve chromatography (gel chromatography), adsorption chromatography, ion exchange chromatography, high performance liquid chromatography (HPLC) and any other liquid chromatography, and combinations thereof.

[0134] A "variant" of a polypeptide (such as an antigen-binding fragment, protein or antibody) is a polypeptide in which one or more amino acid residues are inserted, deleted, added and / or substituted compared to another polypeptide sequence, and includes fusion polypeptides. In addition, protein variants include such protein variants that are modified by proteolytic cleavage, phosphorylation or other post-translational modifications, but retain the biological activity of the antibodies disclosed herein, such as binding to and specificity for HER3. The variant can be about 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 89%, 88%, 87%, 86%, 85%, 84%, 83%, 82%, 81% or 80% identical to the sequence of the antibody or its antigen-binding fragment disclosed herein. The percentage of identity or homology can be calculated with reference to the following description.

[0135] In one embodiment, the percentage of homology or identity can be calculated as 100×[(number of identical positions) / min(TGA,TGB)], and in this formula, TGA and TGB are the sum of the number of residues of the compared sequences A and B and the number of internal gap positions (Russell et al., J. Mol Biol., 244:332-350 (1994)).

[0136] In the present invention, the antibodies of the present invention also include their conservative variants, which means that compared to the amino acid sequence of the antibodies of the present invention, up to 10, preferably up to 8, more preferably up to 5, and most preferably up to 3 amino acids are replaced by amino acids with similar or similar properties to form a polypeptide. These conservative variant polypeptides are preferably produced by amino acid substitution according to Table A.

[0137] Table A

[0138] Original residue Representative substitution Preferred substitution Ala Val; Leu; Ile Val Arg Lys; Gln; Asn Lys Asn Gln; His; Lys; Arg Gln Asp Glu Glu Cys Ser Ser Gln Asn Asn Glu Asp Asp Gly Pro; Ala Ala His Asn; Gln; Lys; Arg Arg Ile Leu; Val; Met; Ala; Phe Leu Leu Ile; Val; Met; Ala; Phe Ile Lys Arg; Gln; Asn Arg Met Leu; Phe; Ile Leu Phe Leu; Val; Ile; Ala; Tyr Leu Pro Ala Ala Ser Thr Thr Thr Ser Ser Trp Tyr; Phe Tyr Tyr Trp; Phe; Thr; Ser Phe Val Ile; Leu; Met; Phe; Ala Leu

[0139] As used herein, the term "K D "(M) is intended to refer to the dissociation equilibrium constant of a specific antibody-antigen interaction. "K D " refers to the dissociation constant, which is obtained from the ratio of K d to K a (i.e., K d / K a ) and is expressed as a molar concentration (M). Given the present disclosure, methods in the art can be used to determine the K D value of an antibody. For example, the K D of an antibody can be determined by using surface plasmon resonance, such as by using a biosensor system (e.g., the system) or by using biolayer interferometry (such as the Octet RED96 system).

[0140] The term "affinity" is the strength of the interaction between an antibody or its antigen-binding fragment and an antigen, which is determined by the characteristics of the antigen, such as the size, shape, and / or charge of the antigen, and the CDR sequences of the antibody or antigen-binding fragment. Methods for determining affinity are known in the art, and the following can be referred to.

[0141] When the dissociation constant (K D ) < 10 6 M, an antibody or its antigen-binding fragment is said to "specifically bind" to its target (such as an antigen). When K D < 10 9 M, the antibody specifically binds to its target with "high affinity".

[0142] As used herein, the term "pharmaceutical composition" is intended to refer to a mixture containing one or more of the compounds described herein or their physiologically / pharmaceutically acceptable salts or their prodrugs and other chemical components (such as physiologically / pharmaceutically acceptable carriers and excipients). The purpose of the pharmaceutical composition is to facilitate administration to an organism, which is beneficial for the absorption of the active ingredient and the exertion of biological activity.

[0143] When applied to animals, humans, experimental subjects, cells, tissues, organs, or biological fluids, "administering" and "treating" mean bringing the animal, human, subject, cell, tissue, organ, or biological fluid into contact with an exogenous pharmaceutical agent, therapeutic agent, diagnostic agent, or composition. "Administering" and "treating" can refer, for example, to therapeutic methods, pharmacokinetic methods, diagnostic methods, research methods, and experimental methods. Treatment of cells encompasses bringing cells into contact with a reagent, as well as bringing a liquid into contact with a reagent, where the liquid contacts the cells. "Administering" and "treating" also refer to ex vivo and in vitro treatment, such as ex vivo and in vitro treatment of cells by a reagent, diagnostic agent, binding composition, or by another cell. When applied to human, veterinary, or research subjects, "treatment" refers to therapeutic treatment, prophylactic or preventive measures, research, and diagnostic applications.

[0144] In addition, the present disclosure includes a medicament for treating a disease associated with HER3, which comprises an antibody, an antigen-binding fragment thereof, or an antibody-drug conjugate of the present disclosure as an active ingredient.

[0145] There is no limitation on the disease associated with HER3, as long as it is a disease associated with HER3. For example, the therapeutic response induced by the molecules disclosed in the present disclosure can be reduced by binding to human HER3. Therefore, when in formulations and formulations suitable for therapeutic applications, the molecules of the present disclosure are very useful for those suffering from tumors, cancers, or infectious diseases.

[0146] In addition, the present disclosure relates to a method for immuno-detecting or measuring HER3, a reagent for immuno-detecting or measuring HER3, a method for immuno-detecting or measuring cells expressing HER3, and a diagnostic reagent for diagnosing a disease associated with HER3-positive cells, which comprises an antibody or antigen-binding fragment specifically recognizing human HER3 of the present disclosure as an active ingredient.

[0147] In the present disclosure, the method for detecting or determining the amount of HER3 can be any known method. For example, it includes immuno-detection or assay.

[0148] Immuno-detection or assay is a method for detecting or determining the amount of an antibody or antigen by using a labeled antigen or antibody. Examples of immuno-detection or assay include radioactively labeled immuno-antibody method (RIA), enzyme immunoassay (EIA or ELISA), fluorescence immunoassay (FIA), luminescence immunoassay, Western blotting method, physicochemical method, and the like.

[0149] The above-mentioned diseases associated with HER3-positive cells can be diagnosed by detecting or measuring cells expressing HER3 by using the antibody or antibody fragment of the present invention.

[0150] To detect cells expressing a polypeptide, known immunoassays can be used, and preferably immunoprecipitation, fluorescence cell staining, or immunohistochemical staining, etc. can be used. In addition, the FMAT8100HTS system (Applied Biosystem) can be used to perform fluorescence antibody staining methods, etc.

[0151] Examples

[0152] The present invention is further illustrated by the following specific examples. It will be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental methods without detailed conditions in the following examples generally follow the conditions described in the conventional conditions, such as "Molecular Cloning: A Laboratory Manual" by Sambrook.J et al. (translated by Huang Peitang et al., Beijing: Science Press, 2002), or follow the conditions recommended by the manufacturer (such as the product manual). Unless otherwise specified, percentages and parts are by weight. Unless otherwise specified, the experimental materials and reagents used in the following examples are commercially available.

[0153] The room temperature described in the examples is the conventional room temperature in the art and is generally 10 - 30 °C.

[0154] Example 1: Immunity and Antibody Screening

[0155] Example 1-1: Preparation of Immunogen

[0156] A combination of recombinant protein antigens huHER3-His and rhesus HER3-His was used to immunize humanized mice (AlloyGK MIX strain). Briefly, 10 μg is a typical amount of protein antigen used for subcutaneous or intraperitoneal injection in experiments performed with ATX-Gx mice. The antigen was mixed with a proprietary adjuvant for immunization. For subcutaneous injection, 2 sites (50 - 100 μl per site) were used; for intraperitoneal injection, we typically used 200 μl.

[0157] Example 1-2: Immunity

[0158] Immunization protocol:

[0159] Anti-HER3 antibodies were obtained through a two-armed immunization protocol using gene-modified mice encoding human immunoglobulin heavy chain variable region and κ light chain variable region by the RIMMS (repeated immunization at multiple sites) protocol. One group of mice was immunized and boosted with the recombinant protein antigen huHER3-His (AcroBio, catalog number ER3-H5223), while another group of mice was immunized with the same huHER3-His but boosted with rhesus HER3-His (Sino Bio, catalog number 90043-K08H). The antibody immune response was monitored by HER3-specific immunoassays. When the desired immune response was achieved, splenocytes were harvested from each mouse and fused with mouse myeloma cells to maintain their viability and form hybridoma cells, and HER3 specificity was screened.

[0160] Examples 1 - 3: Splenocyte fusion

[0161] Splenic lymphocytes and myeloma cells Sp2 / 0 ( CRL-158) were fused by electrofusion or PEG fusion to obtain hybridoma cells. PEG fusion was performed using the Clonacell TM HY technology (STEMCELL technologies) according to the manufacturer's instructions. The ratio of primary cells to mouse myeloma cell line for electrofusion was 1:1, and for PEG fusion was 10:1.

[0162] Example 1 - 4: Screening of hybridoma clones specifically binding to HER3 protein by ELISA

[0163] ELISA was performed using the DuoSet ELISA accessory kit (R&D System, DY008). ELISA plates were coated overnight with 1 μg / ml human HER3 (Acro Bio, catalog number ER3-H5223), rhesus HER3 (Sino Bio, catalog number 90043-K08H), mouse HER3 (Acro Bio, catalog number ER3-M52H5), rat HER3 (Sino Bio, catalog number 80111-r08H), or BSA. Excess unbound protein was washed away by washing the plates three times with wash buffer, and then blocked for 1 hour at room temperature. 50 μl of HER3 hybridoma supernatant was added to the wells in duplicate and incubated for 1 hour. Excess unbound antibody was washed away, and 50 μl of 1:20,000 diluted secondary antibody goat anti-mouse IgG Fc-HRP (ab5870) was added to each well for an additional 1 hour. The plates were washed according to the manufacturer's protocol, and then 50 μL of chemiluminescent reagent (Color A and Color B) was added. The reaction was stopped using 25 μL of 2N sulfuric acid. The optical density of the samples was measured at 450 nm using a microplate reader (PerkinElmer). All tested clones showed selective binding to human HER3 but not to BSA, demonstrating HER3 specificity.

[0164] Table 1. Binding characterization of hybridoma clones by ELISA assay (OD 450 )

[0165]

[0166]

[0167] Examples 1 - 5: Screening of hybridoma clones that specifically bind to HER3+ cancer cells by flow cytometry

[0168] Binding tests of hybridoma supernatants were performed on the HER3+ cell line T-47D (ATCC, HTB-133) and the HER3- cell line Jurkat E6.1 (ATCC, TIB-152) using flow cytometry analysis. Briefly, 50 μL of cells (2×10 6Cells / mL) were mixed with 50 μL of undiluted hybridoma supernatant. The mixture was incubated on ice for 20 min and then washed twice with ice-cold staining buffer. Subsequently, the cells were stained with 50 μL of PE-conjugated secondary antibody (1:400 dilution, BioLegend, Cat#405307) for 20 min. After washing with staining buffer and fixing with 4% PFA, the cells were analyzed by flow cytometry. Purified anti-human HER3 antibody was used as a positive control. Purified mouse IgG1 antibody was used as an isotype control (R&D Systems, Cat#MAB3481). Figure 1 Examples of the selected cell-binding signals measured by flow cytometry are shown.

[0169] Examples 1 - 6: Screening of Hybridoma Clones with Cell Internalization Activity by Indirect Killing Assay

[0170] The cell internalization activity of anti-HER3 antibodies from hybridoma supernatants was measured by using an indirect killing assay in CHO-K1-huHER3 cells (KYinno, cat#KC-1511). CHO-K1-huHER3 cells were seeded at 3000 cells / well in a 96-well plate and incubated overnight. Hybridoma supernatants from each hybridoma clone were diluted with hybridoma medium and mixed with a Fab anti-mouse IgG Fc-MMAF conjugate (Moradec, AM-202AF) with a cleavable linker, and then added to each well. The final concentrations of mouse IgG were approximately 10 nM, 2 nM, and 0.4 nM. The final concentration of the Fab anti-mouse IgG Fc-MMAF conjugate in each well was 20 nM. In the presence of the second Fab-vc-MMAF, the internalized antibody / Fac-vc-MMAF conjugate complex would release the cytotoxic payload and kill the cells. After 3 days of incubation, the live cells in each well were detected by Cell Titer Glo 2.0 assay (Promega, G9243). Purified anti-human HER3 antibody was used as a positive control. Purified mouse IgG1 antibody was used as an isotype control (Biolegend, Cat#400102). As Figure 2 shown, the cells treated with the selected hybridoma supernatants showed reduced viability, indicating antibody internalization.

[0171] Example 2: Sequencing of Positive Hybridoma Clones

[0172] The process of cloning sequences from positive hybridomas is as follows. Hybridoma cells in the logarithmic growth phase are collected, RNA is extracted, reverse transcription is performed, and then the VDJ region is amplified. Next-generation sequencing is carried out on the cDNA library amplified from each clone. The amino acid sequences of the heavy-chain and light-chain variable region DNAs corresponding to the antibodies of the lead candidates are obtained. After manufacturability evaluation, several mutations are introduced in the FR region, and the amino acid sequences of the heavy-chain variable region and light-chain variable region of each antibody and the CDR sequences are shown in the following table. The amino acid residues of the CDRs in VH / VL are numbered and annotated according to the Kabat and Wu numbering systems.

[0173] Table 2. CDR Sequences of the Heavy-Chain Variable Domain of HER3 Hybridoma Clones

[0174]

[0175]

[0176] Table 3. CDR Sequences of the Light-Chain Variable Domain of HER3 Hybridoma Clones

[0177]

[0178]

[0179]

[0180] Table 4. Sequences of the Heavy-Chain and Light-Chain Variable Domains of HER3 Hybridoma Clones

[0181]

[0182]

[0183]

[0184]

[0185]

[0186] Example 3: Construction and Expression of Anti-HER3 Recombinant Antibodies

[0187] Example 3-1: Molecular Cloning of Recombinant Antibodies

[0188] Directly synthesize the cDNA sequences encoding the selected VH and VL regions of the clone as DNA fragments with a 5'-terminal in-frame leader sequence (MGWSCIILFLVATATGVHS). Clone these DNA fragments into the selected vector using the NEBuilder DNA Assembly Cloning Kit (New England Biolabs). Clone the VH region into the pFUSE-CHIg_hG1 vector (InvivoGen #pfuse-hchg1) using the EcoRI and NheI sites, with the VH region in-frame with the hIgG1 heavy chain constant region in the vector. Clone the VL region into the pFUSE2-CLIg_hk vector (InvivoGen, #pfuse2-hclk) using the AgeI and BsiWI sites, with the VL region in-frame with the hIgκ light chain constant region in the vector.

[0189] The IgG form of the antibody is disclosed as the following full lengths of the heavy and light chains.

[0190] Table 5. Sequences of the recombinant antibody IgG constant regions

[0191]

[0192] Table 6. Full length sequences of the heavy and light chains of the anti-HER3 recombinant antibody

[0193]

[0194]

[0195]

[0196]

[0197]

[0198]

[0199]

[0200]

[0201]

[0202]

[0203]

[0204]

[0205]

[0206] Example 3-2: Expression and Purification of Recombinant Antibody

[0207] The heavy chain expression plasmid and the light chain plasmid were co-transfected into Expi293F cells (ThermoFisher, #A14527) using the ExpiFectamine 293 transfection kit (ThermoFisher, A14524), or co-transfected into ExpiCHO-S cells (ThermoFisher, #A29127) using the ExpiFectamine CHO transfection kit (ThermoFisher, A29129). Based on the manufacturer's instructions, the plasmid DNA concentration reached 1.0 μg per ml of suspended cells, and the LC:HC vector ratio was 1:1. The transfected cells were cultured on an orbital shaker at 37 °C and 8% CO2 for 5 to 7 days. The conditioned medium was collected, and the antibody was purified using a HiTrap MabSelect SuRe chromatography column (Cytiva, #17549112) on an AKTA Pure 25 machine (Cytiva). The eluted antibody was neutralized with Tris buffer (pH 9.0) and buffer-exchanged with PBS buffer. The product concentration was measured by UV absorption, and the quality was determined by SDS-PAGE and HPLC.

[0208] Example 4: Binding Characterization of Anti-HER3 Recombinant Antibody to HER3 + Cell Lines by Flow Cytometry

[0209] The binding of hlgGl mAb to cell surface HER3 was determined by FACS analysis using the HER3-expressing positive cancer cell line T-47D cells.

[0210] The experimental procedure refers to Example 1-5.

[0211] Table 7. K + Values of Binding of Anti-HER3 Recombinant Antibody to HER3 D to T-47D Cells

[0212]

[0213]

[0214] Example 5: Characterization of Cellular Internalization of Anti-HER3 Recombinant Antibody in HER3-Expressing Cells

[0215] The cellular internalization activity of anti-HER3 recombinant antibodies was measured using an indirect fluorescence internalization assay in CHO-K1-huHER3 cells (KYinno, cat# KC-1511). CHO-K1-huHER3 cells were seeded at 20,000 cells / well in a 96-well plate and incubated overnight. The recombinant antibodies were diluted with cell culture medium and mixed with a Fab anti-human Fc-pHast conjugate (Advanced Targeting Systems, PH-01) with a pH-dependent fluorescent reporter gene pHast, and then added to each well. The final concentrations of the anti-HER3 recombinant antibodies were 1 nM, 3 nM, and 9 nM. The final concentration of the Fab anti-human Fc-pHast conjugate in each well was 35 nM. In the presence of the second Fab-pHast, the internalized antibody / Fac-pHast conjugate complex will show increased fluorescence in the acidic environment inside the cells. After incubation for 17 hours, the fluorescence from all wells was measured using a microplate reader. The purified anti-human HER3 antibody pertuzumab was used as a positive control. The purified human IgG1 antibody was used as a negative control. As Figure 3 shown, strong internalization signals of anti-HER3 antibodies were observed in CHO-K1-huHER3 cells.

[0216] Example 6: Epitope Characterization of Anti-HER3 Recombinant Antibodies

[0217] Example 6-1: ELISA Binding to Human HER3 Subdomain Proteins

[0218] ELISA was performed using the DuoSet ELISA Ancillary Kit (R&D System, DY008). A 96-well ELISA plate was coated overnight at 4 °C with 1 μg / well of human HER3 protein (HER3-His) or human HER3 subdomains 1&2 (HER3 D1-2, amino acids 20-329), HER3 subdomain 2 (HER3 D2, amino acids 185-329), HER3 subdomains 3&4 (HER3 D3-4, amino acids 330-643), and HER3 subdomain 4 (HER3 D4, amino acids 496-643). Excess unbound protein was washed away by washing the plate three times with wash buffer using a plate washer, and then blocked for 1 hour at room temperature. 100 μl of 10 μg / mL HER3 recombinant antibody was added to the wells in duplicate and incubated for 1 hour at room temperature. Excess unbound antibody was washed away by the plate washer, and 100 μl of 1:5000 diluted secondary antibody goat anti-human IgG Fc-HRP (ab6858) was added to each well to incubate for 30 min at room temperature. According to the manufacturer's protocol, the plate was washed again by the plate washer, and then 100 μL of chemiluminescent agent (TMB) was added. The reaction was stopped using 100 μL of 2N sulfuric acid. The optical density of the samples at 450 nm was measured using a microplate reader (PerkinElmer). All tested recombinant antibodies bound to the full-length human HER3 protein. Recombinant antibody 20B5-1 showed binding to human HER3 subdomains 3-4 and subdomain 4, indicating binding to subdomain 4. All remaining recombinant antibodies (see Table 8 below) showed binding to human HER3 subdomains 1-2 and subdomain 1, indicating binding to subdomain 1.

[0219] Table 8. Binding characterization of HER3 recombinant antibodies to human HER3 full-length or subdomain proteins by ELISA (OD 450 )

[0220]

[0221] Example 6-2: Octet binning

[0222] The epitopes of the first three clones (18E11-1, 20E1-3, 23F6-1) were binned and compared with the reference anti-HER3 antibody pertuzumab. Antibody epitope binning was performed using an Octet Red384 system equipped with a Ni-NTA biosensor from Pall Life Sciences (Menlo Park, CA). The experiment was conducted as a serial binning assay. The assay consisted of a five-step binding cycle: 1) establishing a buffer baseline for 30 seconds, 2) coupling 5 nM HER3 antigen (HER3-His) to the Ni-NTA octet sensor for 5 minutes using a standard 1× assay buffer (PBS + 0.02% Tween 20, 0.1% BSA, 0.05% sodium azide) diluted from a 10× kinetic buffer stock solution (ForteBio), 3) loading 25 nM of each antibody (saturating mAb) to saturate the immobilized antigen for 10 minutes, 4) allowing 25 nM of each antibody (competitive mAb) to bind for 5 minutes, and 5) regenerating the capture sensor for 30 seconds. As shown in Tables 9 and 10, all four anti-HER3 antibodies could be divided into 2 different epitope bins. 118E11-1, 20E1-3, and 23F6-1 were in the same bin, while pertuzumab was in a different bin. After the binding of 18E11-1, 20E1-3, or 23F6-1, pertuzumab could still bind to HER3 and had a good association curve, indicating different epitopes.

[0223] Table 9. Epitope binning of recombinant antibodies that bind to human HER3 protein determined by the Octet Red384 system.

[0224]

[0225]

[0226] Signal shift unit: nm

[0227] Table 10. Epitope bins of anti-HER3 recombinant antibodies against human HER3

[0228] Epitope bin Anti - HER3 antibody 1 Pertuzumab 2 18E11 - 1, 20E1 - 3, 23F6 - 1

[0229] Example 7: Generation of anti-HER3 antibody-drug conjugates (ADCs)

[0230] The antibodies of the present invention have cell affinity activity and endocytic activity, making them suitable for conjugation with drugs to form antibody-drug conjugates for the treatment of HER3-mediated diseases.

[0231] Purification of monoclonal antibodies

[0232] Referring to the preparation procedure of the anti-HER3 antibody described in Reference Example 3-2, the monoclonal antibody was purified for drug conjugation. Further antibodies for conjugation may include any of the antibodies described herein (see Example 3).

[0233] Preparation as an intermediate of the drug

[0234] The following intermediate compounds were used to generate antibody-drug conjugates (ADCs) of the anti-HER3 antibody. Compound D was prepared by the method disclosed in the PCT patent application. (See WO2022161385 filed on January 26, 2022). Deruxtecan (MedChemExpress, Cat#HY-114233) was the positive control. HR9106 was prepared by the method disclosed in the PCT patent application. (See WO2020063673 filed on September 25, 2019).

[0235]

[0236]

[0237] Conjugation of monoclonal antibody with drug molecule

[0238] The anti-HER3 antibody (PBS solution at 5 mg / mL, pH 7.4) was treated with a sufficient molar equivalent of tris(2-carboxyethyl)phosphine (TCEP, 10 mM) at 37 °C for 1 hour. Antibody B12 was the negative control, and pertuzumab and MOTA were the positive controls. A sufficient molar equivalent of the drug linker (e.g., DMSO solution of Deruxtecan or Compound D) was added to the PBS solution of the reduced antibody. Then, after incubation for one hour, the reaction mixture was purified by size exclusion chromatography (SEC) to separate the ADC and the free unconjugated drug linker.

[0239] The drug-antibody ratio (DAR) of the ADC was determined using a TOF LC / MS system (Agilent), and the average DAR values are summarized in Table 10. The average DAR value of the anti-HER3 antibody conjugated with Compound D was approximately 6.0 or 7.0. The average DAR value of the anti-HER3 antibody conjugated with Deruxtecan was approximately 8.0. The synthesis steps of the anti-HER3 antibody conjugated with Compound D having other DAR values can be referred to above.

[0240]

[0241]

[0242] Table 10: Conjugation of monoclonal antibody with linker / payload moiety

[0243] Compound number Monoclonal antibody Linker / payload part Average DAR ADC - 01 Pertuzumab Compound D 7.0 ADC - 02 18E11-1 Compound D 7.0 ADC - 03 20B5-1 Compound D 7.0 ADC - 04 20E1-3 Compound D 7.0 ADC - 05 MOTA Compound D 7.0 ADC - 06 Pertuzumab Deruxtecan 8.0 ADC - 07 18E11-1 Deruxtecan 8.0 ADC - 08 19F6-1 Deruxtecan 8.0 ADC - 09 20B5-1 Deruxtecan 8.0 ADC - 10 20E1-3 Deruxtecan 8.0 ADC - 11 23F6-1 Deruxtecan 8.0 ADC - 12 B12 Deruxtecan 8.0 ADC - 13 18E11-1 Compound D 6.0 ADC - 14 20E1-3 Compound D 6.0

[0244] Example 8: Inhibitory effect of ADC on tumor cell growth

[0245] An in vitro cell killing assay was used to examine the inhibitory effect of ADC on tumor cell growth. Different tumor cells were collected during logarithmic growth and distributed into 96-well plates at 1000 - 1500 cells / well. After overnight incubation, ADC was added to each well. The final concentration of ADC in the wells ranged from 0.01 nM to 666.7 nM. After incubation for 4 to 7 days, the cell viability in each well was determined by Cell Titer Glo 2.0 assay (Promega). Sigmoidal dose-response non-linear regression fitting was used in GraphPad Prism to generate curves and IC 50 values. Data from these experiments are summarized in Tables 11A and 11B. Figure 4 A- Figure 4 C shows representative killing curves for all ADCs tested against the indicated cell lines. All ADCs tested showed good in vitro toxicity against tumor cells, with ADC-02, ADC-03, ADC-04, ADC-07, ADC-10, and ADC-11 showing the most significant toxicity superior to the reference ADC.

[0246] Table 11A: Cytotoxicity assessment of antibody-drug conjugates (Compound D) against tumor cells

[0247]

[0248] ND: Not determined

[0249] Table 11B: Cytotoxicity assessment of antibody-drug conjugates (Deruxtecan) against tumor cells

[0250]

[0251] ND: Not determined

[0252] Example 9: In the presence of NRG1, unlike the reference ADC, HER3 ADC shows cytotoxicity in tumor cells

[0253] NRG1 has been shown to have high affinity for HER3 as a natural ligand ([Kd] < 100 pM) (Am J Respir Cell Mol Biol. April 2000; 22(4):432-40.), and it is difficult for antibodies to compete with it. However, antibodies can bind to antigens at different epitopes, which can be different from where NRG1 can bind, and then we tested our antibodies on different cell lines with different HER3 heterodimer states. By flow cytometry, we found that the binding signals of 18E11-1, 20B5-1, 20E1-3, and 23F6-1 were only slightly inhibited by equimolar concentrations of NRG1 molecules on SKBr3 cells, while the binding of pertuzumab was significantly affected. We further examined whether the binding differences would affect the cytotoxicity of HER3 ADCs, and we did observe that ADC-07 and ADC-10 exhibited superior cytotoxicity when NRG1 was presented on SKBr3 and HCC1569 cells.

[0254] Table 12: Evaluation of the cytotoxicity of antibody-drug conjugates (Deruxtecan) against tumor cells in the presence and absence of NRG

[0255]

[0256] Example 10: Tumor inhibition experiment of ADC on a subcutaneous xenograft tumor model of HER3-positive cancer cells in nude mice

[0257] 1. Xenograft (CDX) model derived from the HCC1569 cell line

[0258] HCC1569 cells were subcutaneously transplanted into mice (CB17 / SCID). When the tumor volume reached approximately 120 - 180 mm 3 ³, the transplanted mice were randomly divided into four groups (5 mice per group). The groups were vehicle control, ADC-01, ADC-03, and ADC-04. The mice were treated intravenously QW with ADC (3 mg / kg). The mean tumor growth inhibition (TGI) was calculated using the following formula:

[0259] TGI = ((mean(C) - mean(C0)) - (mean(T) - mean(T0))) / (mean(C) - mean(C0)) * 100%; where T is the current group value, C is the control group value, and T0 and C0 represent the tumor volume at the start of the test.

[0260] Tumor growth in mice treated with the three ADCs showed a statistically significant difference from that in the control group, resulting in tumor regression.

[0261] The results of the study are shown in Table 13 and Figure 6In group A. There were statistically significant differences in tumor growth between the mice treated with ADC-01, ADC-03, and ADC-04 and those treated with the vehicle, with TGI values of 40.2%, 105.2%, and 105.2% on day 28, respectively.

[0262] Table 13. Efficacy of ADCs against HCC1569 xenograft tumors in tumor-bearing mice

[0263]

[0264] 2. Xenograft (CDX) model derived from the MX-1 cell line

[0265] MX-1 cells were subcutaneously transplanted into mice (CB17 / SCID). When the tumor volume reached approximately 120 - 180 mm 3 at that time, the transplanted mice were randomly divided into four groups (5 mice per group). The groups were vehicle control, ADC-01, ADC-03, and ADC-04. The mice were treated intravenously QW with ADC (3 mg / kg). The average tumor growth inhibition (TGI) was calculated using the following formula:

[0266] TGI = ((mean(C) - mean(C0)) - (mean(T) - mean(T0))) / (mean(C) - mean(C0)) * 100%; where T is the value of the current group, C is the value of the control group, and T0 and C0 represent the tumor volume at the start of the test.

[0267] The results of the study are shown in Table 14 and Figure 6 in B. There were statistically significant differences in tumor growth between the mice treated with ADC-04 and those treated with the vehicle, with TGI values of 5.0%, 48.7%, and 88.4% on day 28, respectively.

[0268] Table 14. Efficacy of ADCs against MX-1 xenograft tumors in tumor-bearing mice

[0269]

[0270] Tracking tumor inhibition studies of ADC-01, ADC-02, ADC-03, and ADC-04 were conducted in the same MX-1 xenograft mouse model. The MX-1 transplanted mice were randomly divided into eight groups (5 mice per group). The groups were vehicle control, 3 mg / kg ADC-01, 6 mg / kg ADC-02, 6 mg / kg ADC-03, 6 mg / kg ADC-04, 2 mg / kg ADC-02, 2 mg / kg ADC-03, and 2 mg / kg ADC-04. The mice were treated intravenously QW with ADC.

[0271] The results of the study are shown in Table 15 and Figure 7 in. The tumor growth in mice treated with ADC-02 and ADC-04 at 2 and 6 mg / kg showed statistically significant differences from that in mice treated with ADC-01 at 3 mg / kg, with TGI values of 111.9%, 91.0%, 113.2%, and 95.2% respectively, while the tumor in mice treated with ADC-01 at 3 mg / kg showed a TGI of 58.8%.

[0272] Table 15. Efficacy of ADCs against MX-1 xenograft tumors in tumor-bearing mice

[0273]

[0274] ADC-02, ADC-04, ADC-06, ADC-13, and ADC-14 were conducted in the same MX-1 xenograft mouse model. The MX-1 xenograft mice were randomly divided into six groups (5 mice per group). The groups were vehicle control, ADC-02, ADC-04, ADC-06, ADC-13, and ADC-14. Mice were treated intravenously QW with ADC (3 mg / kg) for 3 weeks.

[0275] The results of the study are shown in Table 16 and Figure 8 in. ADC-02 and ADC-04 with different DAR values showed comparable tumor growth inhibition.

[0276] Table 16. Efficacy of ADCs against MX-1 xenograft tumors in tumor-bearing mice

[0277]

[0278] Example 11: Pharmacokinetic (PK) determination of anti-HER3 antibody and antibody-drug conjugate in mice

[0279] Female Balb / C mice (6 - 8 weeks old) were used to evaluate the pharmacokinetics of the antibody-drug conjugate. Blank serum was collected before dosing. ADC was administered intravenously at 3 mg / kg. After injection, at predetermined time points (1, 4, 24, 48, 72, 120, 168, 336, and 504 hours), serum was collected from the designated mice and immediately stored at -80 °C until further analysis.

[0280] The serum concentration of ADC was measured by ELISA, and pharmacokinetic parameters were calculated by PK Solver 2.0. The main pharmacokinetic parameters are shown in Table 16 and Table 17.

[0281] Table 16. Pharmacokinetic parameters of total antibody in mice

[0282]

[0283] Table 17. Pharmacokinetic parameters of ADC in mice

[0284]

[0285] The AUCs of HER3 antibody ADC-02 and ADC-04 in mice are similar. The elimination half-lives of ADC-02 and ADC-04 are superior to those of ADC-01, which may contribute to their superior in vivo therapeutic efficacy.

Claims

1. An antibody-drug conjugate of general formula (A) or a pharmaceutically acceptable salt or solvate thereof, Ab-(L2-L1-D) y (A) wherein: D is a cytotoxic drug; L1 and L2 are linking units; y is a number from 1 to 20, preferably from 2 to 10, more preferably from 2 to 8, more preferably from 2 to 6 or from 4 to 8, most preferably 2, 4, 6, 7, 8; Ab is an anti-HER3 antibody or an antigen-binding fragment thereof, which comprises: a heavy-chain variable region of the antibody comprising HCDR1, HCDR2 and HCDR3 regions and a light-chain variable region of the antibody comprising LCDR1, LCDR2 and LCDR3 regions, wherein: The heavy-chain variable region of the Ab comprises: HCDR1 as shown in SEQ ID NO: 08, HCDR2 as shown in SEQ ID NO: 27, and HCDR3 as shown in SEQ ID NO: 46; or HCDR1 as shown in SEQ ID NO: 09, HCDR2 as shown in SEQ ID NO: 28, and HCDR3 as shown in SEQ ID NO: 47; or HCDR1 as shown in SEQ ID NO: 10, HCDR2 as shown in SEQ ID NO: 29, and HCDR3 as shown in SEQ ID NO: 48; or HCDR1 as shown in SEQ ID NO: 11, HCDR2 as shown in SEQ ID NO: 30, and HCDR3 as shown in SEQ ID NO: 49; or HCDR1 as shown in SEQ ID NO: 12, HCDR2 as shown in SEQ ID NO: 31, and HCDR3 as shown in SEQ ID NO: 50; or HCDR1 as shown in SEQ ID NO: 01, HCDR2 as shown in SEQ ID NO: 21, and HCDR3 as shown in SEQ ID NO: 51; or HCDR1 as shown in SEQ ID NO: 06, HCDR2 as shown in SEQ ID NO: 32, and HCDR3 as shown in SEQ ID NO: 52; or HCDR1 as shown in SEQ ID NO: 13, HCDR2 as shown in SEQ ID NO: 33, and HCDR3 as shown in SEQ ID NO: 53; or HCDR1 as shown in SEQ ID NO: 14, HCDR2 as shown in SEQ ID NO: 33, and HCDR3 as shown in SEQ ID NO: 54; or HCDR1 as shown in SEQ ID NO: 15, HCDR2 as shown in SEQ ID NO: 34, and HCDR3 as shown in SEQ ID NO: 55; or HCDR1 as shown in SEQ ID NO: 16, HCDR2 as shown in SEQ ID NO: 35, and HCDR3 as shown in SEQ ID NO: 56; or HCDR1 as shown in SEQ ID NO: 17, HCDR2 as shown in SEQ ID NO: 36, and HCDR3 as shown in SEQ ID NO: 57; or HCDR1 as shown in SEQ ID NO: 06, HCDR2 as shown in SEQ ID NO: 32, and HCDR3 as shown in SEQ ID NO: 58; or HCDR1 as shown in SEQ ID NO: 01, HCDR2 as shown in SEQ ID NO: 18, and HCDR3 as shown in SEQ ID NO: 37; or HCDR1 as shown in SEQ ID NO: 02, HCDR2 as shown in SEQ ID NO: 19, and HCDR3 as shown in SEQ ID NO: 38; or HCDR1 as shown in SEQ ID NO: 03, HCDR2 as shown in SEQ ID NO: 20, and HCDR3 as shown in SEQ ID NO: 39; or HCDR1 as shown in SEQ ID NO: 04, HCDR2 as shown in SEQ ID NO: 21, and HCDR3 as shown in SEQ ID NO: 40; or HCDR1 as shown in SEQ ID NO: 05, HCDR2 as shown in SEQ ID NO: 22, and HCDR3 as shown in SEQ ID NO: 41; or HCDR1 as shown in SEQ ID NO: 06, HCDR2 as shown in SEQ ID NO: 23, and HCDR3 as shown in SEQ ID NO: 42; or HCDR1 as shown in SEQ ID NO: 07, HCDR2 as shown in SEQ ID NO: 24, and HCDR3 as shown in SEQ ID NO: 43; or HCDR1 as shown in SEQ ID NO: 06, HCDR2 as shown in SEQ ID NO: 25, and HCDR3 as shown in SEQ ID NO: 44; or HCDR1 as shown in SEQ ID NO: 06, HCDR2 as shown in SEQ ID NO: 26, and HCDR3 as shown in SEQ ID NO: 45; and / or The variable region of the antibody light chain of said Ab comprises: LCDR1 as shown in SEQ ID NO: 66, LCDR2 as shown in SEQ ID NO: 83, and LCDR3 as shown in SEQ ID NO: 96; or LCDR1 as shown in SEQ ID NO: 67, LCDR2 as shown in SEQ ID NO: 79, and LCDR3 as shown in SEQ ID NO: 97; or LCDR1 as shown in SEQ ID NO: 68, LCDR2 as shown in SEQ ID NO: 77, and LCDR3 as shown in SEQ ID NO: 98; or LCDR1 as shown in SEQ ID NO: 69, LCDR2 as shown in SEQ ID NO: 84, and LCDR3 as shown in SEQ ID NO: 99; or LCDR1 as shown in SEQ ID NO: 70, LCDR2 as shown in SEQ ID NO: 85, and LCDR3 as shown in SEQ ID NO: 100; or LCDR1 as shown in SEQ ID NO: 71, LCDR2 as shown in SEQ ID NO: 85, and LCDR3 as shown in SEQ ID NO: 100; or LCDR1 as shown in SEQ ID NO: 61, LCDR2 as shown in SEQ ID NO: 77, and LCDR3 as shown in SEQ ID NO: 90; or LCDR1 as shown in SEQ ID NO: 72, LCDR2 as shown in SEQ ID NO: 86, and LCDR3 as shown in SEQ ID NO: 101; or LCDR1 as shown in SEQ ID NO: 73, LCDR2 as shown in SEQ ID NO: 82, and LCDR3 as shown in SEQ ID NO: 103; or LCDR1 as shown in SEQ ID NO: 64, LCDR2 as shown in SEQ ID NO: 82, and LCDR3 as shown in SEQ ID NO: 103; or LCDR1 as shown in SEQ ID NO: 74, LCDR2 as shown in SEQ ID NO: 79, and LCDR3 as shown in SEQ ID NO: 92; or LCDR1 as shown in SEQ ID NO: 75, LCDR2 as shown in SEQ ID NO: 82, and LCDR3 as shown in SEQ ID NO: 104; or LCDR1 as shown in SEQ ID NO: 65, LCDR2 as shown in SEQ ID NO: 82, and LCDR3 as shown in SEQ ID NO: 95; or LCDR1 as shown in SEQ ID NO: 76, LCDR2 as shown in SEQ ID NO: 85, and LCDR3 as shown in SEQ ID NO: 100; or LCDR1 as shown in SEQ ID NO: 66, LCDR2 as shown in SEQ ID NO: 83, and LCDR3 as shown in SEQ ID NO: 96; or LCDR1 as shown in SEQ ID NO: 59, LCDR2 as shown in SEQ ID NO: 77, and LCDR3 as shown in SEQ ID NO: 58; or LCDR1 as shown in SEQ ID NO: 60, LCDR2 as shown in SEQ ID NO: 78, and LCDR3 as shown in SEQ ID NO: 89; or LCDR1 as shown in SEQ ID NO: 61, LCDR2 as shown in SEQ ID NO: 77, and LCDR3 as shown in SEQ ID NO: 90; or LCDR1 as shown in SEQ ID NO: 59, LCDR2 as shown in SEQ ID NO: 77, and LCDR3 as shown in SEQ ID NO: 90; or LCDR1 as shown in SEQ ID NO: 62, LCDR2 as shown in SEQ ID NO: 77, and LCDR3 as shown in SEQ ID NO: 91; or LCDR1 as shown in SEQ ID NO: 63, LCDR2 as shown in SEQ ID NO: 79, and LCDR3 as shown in SEQ ID NO: 92; or LCDR1 as shown in SEQ ID NO: 60, LCDR2 as shown in SEQ ID NO: 80, and LCDR3 as shown in SEQ ID NO: 93; or LCDR1 as shown in SEQ ID NO: 64, LCDR2 as shown in SEQ ID NO: 81, and LCDR3 as shown in SEQ ID NO: 94; or LCDR1 as shown in SEQ ID NO: 65, LCDR2 as shown in SEQ ID NO: 82, and LCDR3 as shown in SEQ ID NO: 95; or LCDR1 as shown in SEQ ID NO: 60, LCDR2 as shown in SEQ ID NO: 80, and LCDR3 as shown in SEQ ID NO:

89.

2. The antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof according to claim 1, wherein the Ab comprises: a) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 08, SEQ ID NO: 27, and SEQ ID NO: 46, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 66, SEQ ID NO: 83, and SEQ ID NO: 96, respectively; or b) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 09, SEQ ID NO: 28, and SEQ ID NO: 47, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 67, SEQ ID NO: 79, and SEQ ID NO: 97, respectively; or c) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 10, SEQ ID NO: 29, and SEQ ID NO: 48, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 68, SEQ ID NO: 77, and SEQ ID NO: 98, respectively; or d) a heavy chain variable region sequence comprising HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 11, SEQ ID NO: 30, and SEQ ID NO: 49, respectively; and a light chain variable region sequence comprising LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 69, SEQ ID NO: 84, and SEQ ID NO: 99, respectively; or e) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 12, SEQ ID NO: 31, and SEQ ID NO: 50, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 70, SEQ ID NO: 85, and SEQ ID NO: 100, respectively; or f) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 12, SEQ ID NO: 31, and SEQ ID NO: 50, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 71, SEQ ID NO: 85, and SEQ ID NO: 100, respectively; or g) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 01, SEQ ID NO: 21, and SEQ ID NO: 51, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 61, SEQ ID NO: 77, and SEQ ID NO: 90, respectively; or h) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 06, SEQ ID NO: 32, and SEQ ID NO: 52, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 72, SEQ ID NO: 86, and SEQ ID NO: 101, respectively; or i) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 06, SEQ ID NO: 32, and SEQ ID NO: 52, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 73, SEQ ID NO: 87, and SEQ ID NO: 102, respectively; or j) The heavy chain variable region sequence comprises HCDR1, HCDR2 and HCDR3 as shown in SEQ ID NO: 13, SEQ ID NO: 33 and SEQ ID NO: 53 respectively; and the light chain variable region sequence comprises LCDR1, LCDR2 and LCDR3 as shown in SEQ ID NO: 73, SEQ ID NO: 82 and SEQ ID NO: 103 respectively; or k) The heavy chain variable region sequence comprises HCDR1, HCDR2 and HCDR3 as shown in SEQ ID NO: 14, SEQ ID NO: 33 and SEQ ID NO: 54 respectively; and the light chain variable region sequence comprises LCDR1, LCDR2 and LCDR3 as shown in SEQ ID NO: 64, SEQ ID NO: 82 and SEQ ID NO: 103 respectively; or l) The heavy chain variable region sequence comprises HCDR1, HCDR2 and HCDR3 as shown in SEQ ID NO: 15, SEQ ID NO: 34 and SEQ ID NO: 55 respectively; and the light chain variable region sequence comprises LCDR1, LCDR2 and LCDR3 as shown in SEQ ID NO: 74, SEQ ID NO: 79 and SEQ ID NO: 92 respectively; or m) The heavy chain variable region sequence comprises HCDR1, HCDR2 and HCDR3 as shown in SEQ ID NO: 16, SEQ ID NO: 35 and SEQ ID NO: 56 respectively; and the light chain variable region sequence comprises LCDR1, LCDR2 and LCDR3 as shown in SEQ ID NO: 75, SEQ ID NO: 82 and SEQ ID NO: 104 respectively; or n) The heavy chain variable region sequence comprises HCDR1, HCDR2 and HCDR3 as shown in SEQ ID NO: 16, SEQ ID NO: 35 and SEQ ID NO: 56 respectively; and the light chain variable region sequence comprises LCDR1, LCDR2 and LCDR3 as shown in SEQ ID NO: 65, SEQ ID NO: 82 and SEQ ID NO: 95 respectively; or o) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 17, SEQ ID NO: 36, and SEQ ID NO: 57, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 76, SEQ ID NO: 85, and SEQ ID NO: 100, respectively; or p) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 06, SEQ ID NO: 32, and SEQ ID NO: 58, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 66, SEQ ID NO: 83, and SEQ ID NO: 96, respectively; or q) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 01, SEQ ID NO: 18, and SEQ ID NO: 37, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 59, SEQ ID NO: 77, and SEQ ID NO: 88, respectively; or r) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 02, SEQ ID NO: 19, and SEQ ID NO: 38, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 60, SEQ ID NO: 78, and SEQ ID NO: 89, respectively; or s) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 03, SEQ ID NO: 20, and SEQ ID NO: 39, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 61, SEQ ID NO: 77, and SEQ ID NO: 90, respectively; or t) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 04, SEQ ID NO: 21, and SEQ ID NO: 40, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 59, SEQ ID NO: 77, and SEQ ID NO: 90, respectively; or u) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 05, SEQ ID NO: 22, and SEQ ID NO: 41, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 62, SEQ ID NO: 77, and SEQ ID NO: 91, respectively; or v) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 06, SEQ ID NO: 23, and SEQ ID NO: 42, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 63, SEQ ID NO: 79, and SEQ ID NO: 92, respectively; or w) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 07, SEQ ID NO: 24, and SEQ ID NO: 43, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 60, SEQ ID NO: 80, and SEQ ID NO: 93, respectively; or x) The heavy chain variable region sequence comprises HCDR1, HCDR2, and HCDR3 as shown in SEQ ID NO: 06, SEQ ID NO: 25, and SEQ ID NO: 44, respectively; and the light chain variable region sequence comprises LCDR1, LCDR2, and LCDR3 as shown in SEQ ID NO: 64, SEQ ID NO: 81, and SEQ ID NO: 94, respectively; or y) The heavy chain variable region sequence comprises HCDR1, HCDR2 and HCDR3 as shown in SEQ ID NO: 06, SEQ ID NO: 26 and SEQ ID NO: 45 respectively; and the light chain variable region sequence comprises LCDR1, LCDR2 and LCDR3 as shown in SEQ ID NO: 65, SEQ ID NO: 82 and SEQ ID NO: 95 respectively; or z) The heavy chain variable region sequence comprises HCDR1, HCDR2 and HCDR3 as shown in SEQ ID NO: 08, SEQ ID NO: 27 and SEQ ID NO: 46 respectively; and the light chain variable region sequence comprises LCDR1, LCDR2 and LCDR3 as shown in SEQ ID NO: 60, SEQ ID NO: 80 and SEQ ID NO: 89 respectively.

3. The antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof according to any one of claims 1 to 2, wherein the Ab is a murine antibody, a chimeric antibody, a humanized antibody, a human antibody or an antigen-binding fragment thereof.

4. The antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof according to any one of claims 1 to 3, wherein the Ab comprises a heavy chain variable region of the following sequences: SEQ ID NO: 127, 129, 131, 133, 135, 137, 139, 141, 144, 145, 147, 149, 151, 153, 155, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123 and 125, or has at least 80%, 85%, 90%, 95% or 99% sequence identity therewith; and / or the Ab comprises a light chain variable region of the following sequences: SEQ ID NO: 128, 130, 132, 134, 136, 138, 140, 142, 143, 146, 148, 150, 152, 154, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124 and 126, or has at least 80%, 85%, 90%, 95% or 99% sequence identity therewith.

5. The antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof according to any one of claims 1 to 4, wherein the Ab comprises: a-1) A heavy chain variable region as shown in SEQ ID NO: 127 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 128 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or a-2) A heavy chain variable region as shown in SEQ ID NO: 127 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 126 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or b) A heavy chain variable region as shown in SEQ ID NO: 129 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 130 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or c) A heavy chain variable region as shown in SEQ ID NO: 131 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 132 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or d) A heavy chain variable region as shown in SEQ ID NO: 133 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 134 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or e-1) A heavy chain variable region as shown in SEQ ID NO: 135 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 136 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or e-2) A heavy chain variable region as shown in SEQ ID NO: 137 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 138 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or f) a heavy chain variable region as shown in SEQ ID NO: 139 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 140 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or g-1) a heavy chain variable region as shown in SEQ ID NO: 141 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 142 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or g-2) a heavy chain variable region as shown in SEQ ID NO: 141 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 143 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or g-3) a heavy chain variable region as shown in SEQ ID NO: 144 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 142 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or h) a heavy chain variable region as shown in SEQ ID NO: 145 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 146 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or i) a heavy chain variable region as shown in SEQ ID NO: 147 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 148 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or j) a heavy chain variable region as shown in SEQ ID NO: 149 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 150 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or k-1) a heavy chain variable region as shown in SEQ ID NO: 151 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 152 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or k-2) a heavy chain variable region as shown in SEQ ID NO: 151 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 122 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or l) a heavy chain variable region as shown in SEQ ID NO: 153 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 154 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or m) a heavy chain variable region as shown in SEQ ID NO: 155 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 126 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or n) a heavy chain variable region as shown in SEQ ID NO: 105 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 106 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or o) a heavy chain variable region as shown in SEQ ID NO: 107 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 108 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or p) a heavy chain variable region as shown in SEQ ID NO: 109 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 110 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or q) a heavy chain variable region as shown in SEQ ID NO: 111 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 112 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or r) a heavy chain variable region as shown in SEQ ID NO: 113 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 114 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or s) a heavy chain variable region as shown in SEQ ID NO: 115 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 116 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or t) a heavy chain variable region as shown in SEQ ID NO: 117 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 118 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or u) a heavy chain variable region as shown in SEQ ID NO: 119 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 120 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or v) a heavy chain variable region as shown in SEQ ID NO: 121 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 122 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or w-1) a heavy chain variable region as shown in SEQ ID NO: 123 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 124 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or w-2) a heavy chain variable region as shown in SEQ ID NO: 125 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 126 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; or x) a heavy chain variable region as shown in SEQ ID NO: 123 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto; and / or a light chain variable region as shown in SEQ ID NO: 126 or having at least 80%, 85%, 90%, 95% or 99% sequence identity thereto.

6. The antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof according to any one of claims 1 to 5, wherein the Ab comprises: a-1) a heavy chain variable region as shown in SEQ ID NO: 127 and a light chain variable region as shown in SEQ ID NO: 128; a-2) a heavy chain variable region as shown in SEQ ID NO: 127 and a light chain variable region as shown in SEQ ID NO: 126; b) a heavy chain variable region as shown in SEQ ID NO: 129 and a light chain variable region as shown in SEQ ID NO: 130; c) a heavy chain variable region as shown in SEQ ID NO: 131 and a light chain variable region as shown in SEQ ID NO: 132; d) a heavy chain variable region as shown in SEQ ID NO: 133 and a light chain variable region as shown in SEQ ID NO: 134; e-1) a heavy chain variable region as shown in SEQ ID NO: 135 and a light chain variable region as shown in SEQ ID NO: 136; e-2) a heavy chain variable region as shown in SEQ ID NO: 137 and a light chain variable region as shown in SEQ ID NO: 138; f) a heavy chain variable region as shown in SEQ ID NO: 139 and a light chain variable region as shown in SEQ ID NO: 140; g-1) a heavy chain variable region as shown in SEQ ID NO: 141 and a light chain variable region as shown in SEQ ID NO: 142; g-2) a heavy chain variable region as shown in SEQ ID NO: 141 and a light chain variable region as shown in SEQ ID NO: 143; g-3) The heavy chain variable region as shown in SEQ ID NO: 144 and the light chain variable region as shown in SEQ ID NO: 142; h) The heavy chain variable region as shown in SEQ ID NO: 145 and the light chain variable region as shown in SEQ ID NO: 146; i) The heavy chain variable region as shown in SEQ ID NO: 147 and the light chain variable region as shown in SEQ ID NO: 148; j) The heavy chain variable region as shown in SEQ ID NO: 149 and the light chain variable region as shown in SEQ ID NO: 150; k-1) The heavy chain variable region as shown in SEQ ID NO: 151 and the light chain variable region as shown in SEQ ID NO: 152; k-2) The heavy chain variable region as shown in SEQ ID NO: 151 and the light chain variable region as shown in SEQ ID NO: 122; l) The heavy chain variable region as shown in SEQ ID NO: 153 and the light chain variable region as shown in SEQ ID NO: 154; m) The heavy chain variable region as shown in SEQ ID NO: 155 and the light chain variable region as shown in SEQ ID NO: 126; n) The heavy chain variable region as shown in SEQ ID NO: 105 and the light chain variable region as shown in SEQ ID NO: 106; o) The heavy chain variable region as shown in SEQ ID NO: 107 and the light chain variable region as shown in SEQ ID NO: 108; p) The heavy chain variable region as shown in SEQ ID NO: 109 and the light chain variable region as shown in SEQ ID NO: 110; q) The heavy chain variable region as shown in SEQ ID NO: 111 and the light chain variable region as shown in SEQ ID NO: 112; r) The heavy chain variable region as shown in SEQ ID NO: 113 and the light chain variable region as shown in SEQ ID NO: 114; s) The heavy chain variable region as shown in SEQ ID NO: 115 and the light chain variable region as shown in SEQ ID NO: 116; t) The heavy chain variable region as shown in SEQ ID NO: 117 and the light chain variable region as shown in SEQ ID NO: 118; u) The heavy chain variable region as shown in SEQ ID NO: 119 and the light chain variable region as shown in SEQ ID NO: 120; v) A heavy chain variable region as shown in SEQ ID NO: 121 and a light chain variable region as shown in SEQ ID NO: 122; w-1) A heavy chain variable region as shown in SEQ ID NO: 123 and a light chain variable region as shown in SEQ ID NO: 124; w-2) A heavy chain variable region as shown in SEQ ID NO: 125 and a light chain variable region as shown in SEQ ID NO: 126; x) A heavy chain variable region as shown in SEQ ID NO: 123 and a light chain variable region as shown in SEQ ID NO:

126.

7. The antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof according to any one of claims 1 to 6, wherein the Ab is a full-length antibody, which further comprises a human antibody constant region; Preferably, the heavy chain constant region of the human antibody constant region is selected from the constant regions of human IgG1, IgG2, IgG3 and IgG4 and their conservative variants, and the light chain constant region of the human antibody constant region is selected from the kappa chain constant region and lambda chain constant region of human antibodies and their conservative variants; More preferably, the full-length antibody comprises the human antibody heavy chain constant region of SEQ ID NO: 156 and the human light chain constant region of SEQ ID NO:

157.

8. The antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof according to any one of claims 1 to 7, wherein the Ab comprises: a-1) A heavy chain as shown in SEQ ID NO: 180 and a light chain as shown in SEQ ID NO: 181; a-2) A heavy chain as shown in SEQ ID NO: 180 and a light chain as shown in SEQ ID NO: 179; b) A heavy chain as shown in SEQ ID NO: 182 and a light chain as shown in SEQ ID NO: 183; c) A heavy chain as shown in SEQ ID NO: 184 and a light chain as shown in SEQ ID NO: 185; g) A heavy chain as shown in SEQ ID NO: 186 and a light chain as shown in SEQ ID NO: 187; e-1) A heavy chain as shown in SEQ ID NO: 188 and a light chain as shown in SEQ ID NO: 189; e-2) A heavy chain as shown in SEQ ID NO: 190 and a light chain as shown in SEQ ID NO: 191; f) A heavy chain as shown in SEQ ID NO: 192 and a light chain as shown in SEQ ID NO: 193; g-1) A heavy chain as shown in SEQ ID NO: 194 and a light chain as shown in SEQ ID NO: 195; g-2) A heavy chain as shown in SEQ ID NO: 194 and a light chain as shown in SEQ ID NO: 196; g-3) A heavy chain as shown in SEQ ID NO: 197 and a light chain as shown in SEQ ID NO: 195; h) A heavy chain as shown in SEQ ID NO: 198 and a light chain as shown in SEQ ID NO: 199; i) A heavy chain as shown in SEQ ID NO: 200 and a light chain as shown in SEQ ID NO: 201; j) A heavy chain as shown in SEQ ID NO: 202 and a light chain as shown in SEQ ID NO: 203; k-1) A heavy chain as shown in SEQ ID NO: 204 and a light chain as shown in SEQ ID NO: 205; k-2) A heavy chain as shown in SEQ ID NO: 204 and a light chain as shown in SEQ ID NO: 175; l) A heavy chain as shown in SEQ ID NO: 206 and a light chain as shown in SEQ ID NO: 207; m) A heavy chain as shown in SEQ ID NO: 208 and a light chain as shown in SEQ ID NO: 179; n) A heavy chain as shown in SEQ ID NO: 158 and a light chain as shown in SEQ ID NO: 159; o) A heavy chain as shown in SEQ ID NO: 160 and a light chain as shown in SEQ ID NO: 161; p) A heavy chain as shown in SEQ ID NO: 162 and a light chain as shown in SEQ ID NO: 163; q) A heavy chain as shown in SEQ ID NO: 164 and a light chain as shown in SEQ ID NO: 165; r) A heavy chain as shown in SEQ ID NO: 166 and a light chain as shown in SEQ ID NO: 167; s) A heavy chain as shown in SEQ ID NO: 168 and a light chain as shown in SEQ ID NO: 169; t) A heavy chain as shown in SEQ ID NO: 170 and a light chain as shown in SEQ ID NO: 171; u) A heavy chain as shown in SEQ ID NO: 172 and a light chain as shown in SEQ ID NO: 173; v) a heavy chain as shown in SEQ ID NO: 174 and a light chain as shown in SEQ ID NO: 175; w-1) a heavy chain as shown in SEQ ID NO: 176 and a light chain as shown in SEQ ID NO: 177; w-2) a heavy chain as shown in SEQ ID NO: 178 and a light chain as shown in SEQ ID NO: 179; x) a heavy chain as shown in SEQ ID NO: 176 and a light chain as shown in SEQ ID NO:

179.

9. The antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof according to any one of claims 1 to 8, wherein the antigen-binding fragment is selected from: Fab, Fab', F(ab')2, variable fragment (Fv), single-chain variable fragment (scFv), dimeric domain V (diabody), disulfide-stabilized Fv (dsFv), and CDR-containing peptides.

10. The antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof according to any one of claims 1 to 9, wherein the cytotoxic drug is selected from toxins, chemotherapeutic agents, antibiotics, radioisotopes, and nucleases.

11. The antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof according to any one of claims 1 to 10, wherein the cytotoxic drug is selected from tubulin inhibitors or topoisomerase inhibitors; preferably auristatin analogs or camptothecin derivatives; more preferably SN-38, MMAE, MMAF, or irinotecan.

12. The antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof according to claim 11, wherein the antibody-drug conjugate is as shown in general formula (B): Wherein: L1 and L2 are linking units; y is a number selected from 1 to 10, preferably a number selected from 2 to 8, more preferably a number from 2 to 6 or 4 to 8, even more preferably a number from 6 to 8, and most preferably 4, 6, 7, 8; Ab is an anti-HER3 antibody or an antigen-binding fragment thereof according to any one of claims 1 to 9.

13. The antibody-drug conjugate of general formula (B) or a pharmaceutically acceptable salt or solvate thereof according to claim 12, wherein the antibody-drug conjugate is as shown in general formula (C): Wherein: R1 is selected from hydrogen, C 1-6 haloalkyl or C 3-8 cycloalkyl; R2 is selected from hydrogen, C 1-6 haloalkyl or C 3-8 cycloalkyl; Or, R1 and R2 together with the carbon atom to which they are attached form a C 3-8 cycloalkyl group.

14. The antibody-drug conjugate of general formula (C) according to claim 13, or a pharmaceutically acceptable salt or solvate thereof, wherein: R1 is selected from hydrogen, C 1-3 haloalkyl or C 3-6 cycloalkyl; R2 is selected from hydrogen, C 1-3 haloalkyl or C 3-6 cycloalkyl; Or, R1 and R2 together with the carbon atom to which they are attached form a C 3-6 cycloalkyl group.

15. The antibody-drug conjugate according to any one of claims 12 to 14, or a pharmaceutically acceptable salt or solvate thereof, wherein L2 is as shown in general formula (I): wherein: s 1 and s 2 each independently is an integer selected from 0 - 8, preferably, s 1 and s 2 are independently selected from 1, 2, 3, 4, 5 or 6; or, s 1 is an integer from 1 to 8, s 2 is 0, preferably, s 1 is selected from 4, 5, 6, 7 or 8, and s 2 is 0; or, s 2 an integer selected from 2 to 8, s 1 is 2, preferably, s 2 selected from 2, 3, 4, 5 or 6, and s 1 is 2.

16. The antibody-drug conjugate according to any one of claims 12 to 15, or a pharmaceutically acceptable salt or solvate thereof, wherein the antibody-drug conjugate has the following structure: wherein: y is a number selected from 1 to 10, preferably a number selected from 2 to 8, more preferably a number from 2 to 6 or 4 to 8, even more preferably a number from 6 to 8, and most preferably 4, 6, 7, 8; Ab is an anti-HER3 antibody or an antigen-binding fragment thereof according to any one of claims 1 to 9.

17. The antibody-drug conjugate of general formula (B) according to any one of claims 1 to 16, or a pharmaceutically acceptable salt or solvate thereof, wherein the antibody-drug conjugate is selected from the following compounds: wherein: y is a number selected from 1 to 10, preferably a number selected from 2 to 8, more preferably a number from 2 to 6 or 4 to 8, even more preferably a number from 6 to 8, and most preferably 4, 6, 7, 8.

18. A method for preparing an antibody-drug conjugate or a pharmaceutically acceptable salt or solvate thereof, the method comprising the following steps: After reduction, Ab is conjugated with a compound to obtain an antibody-drug conjugate; wherein: Ab is an anti-HER3 antibody or an antigen-binding fragment thereof according to any one of claims 1 to 9; R1 is selected from hydrogen, C 1-3 haloalkyl or C 3-6 cycloalkyl; R2 is selected from hydrogen, C 1-3 haloalkyl or C 3-6 cycloalkyl; Or, R1 and R2 together with the carbon atom to which they are attached form a C 3-6 cycloalkyl group; L2 is the linker according to claim 15; y is a number selected from 1 to 10, preferably a number selected from 2 to 8, more preferably a number from 2 to 6 or 4 to 8, even more preferably a number from 6 to 8, and most preferably 4, 6, 7, 8.

19. A pharmaceutical composition comprising the antibody-drug conjugate according to any one of claims 1 to 17 or a pharmaceutically acceptable salt or solvate thereof, and one or more pharmaceutically acceptable excipients, diluents or carriers.

20. Use of the antibody-drug conjugate according to any one of claims 1 to 17 or a pharmaceutically acceptable salt or solvate thereof, or the pharmaceutical composition thereof according to claim 19, for the manufacture of a medicament for the treatment or prevention of a disease associated with human HER3.

21. The use according to claim 20, characterized in that It is used for manufacturing a medicament for treating or preventing cancers having HER3 expression; preferably, the cancers are breast cancer, colorectal cancer, lung cancer, multiple myeloma, ovarian cancer, liver cancer, gastric cancer, pancreatic cancer, prostate cancer, acute myeloid leukemia, chronic myeloid leukemia, osteosarcoma, squamous cell carcinoma, peripheral nerve sheath tumor, schwannoma, head and neck cancer, bladder cancer, esophageal cancer, glioblastoma, soft tissue clear cell sarcoma, malignant mesothelioma, neurofibromatosis, renal cancer and melanoma.

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