Abstract 4270: Targeting CNTN4 with exatecan-based antibody-drug conjugate for the treatment of solid tumors

Abstract As a novel immune checkpoint, we previously confirmed that contactin 4 (CNTN4) expressed on tumors negatively regulates T cell activity by binding to amyloid precursor protein (APP) on T cells. Immunohistochemistry analysis revealed high expression of CNTN4 in various tumors, including gallbladder, pancreatic, gastric, endometrial, hepatic, prostatic, bladder cancers, melanoma, and others, while its expression remains low in normal tissues, including immune cells. Based on the tumor-specific expression profile of CNTN4, we have developed an antibody-drug conjugate (ADC) targeting CNTN4. This ADC utilizes GENA-104A16.hIgG1 (A16.1), an anti-CNTN4 antibody with reduced effector function of human IgG1, conjugated via cysteine-maleimide linkage to linker including hydrophilic moiety and the topoisomerase I inhibitor (exatecan) with high drug-to-antibody ratio (DAR)(A16.1-Exa). To evaluate its potential, the internalization performance of A16.1 was compared with trastuzumab (anti-HER2) using SK-BR3 cells engineered to overexpress CNTN4, which exhibited a higher HER2 target count than CNTN4 target count. A16.1-Exa demonstrated potent and highly specific cytotoxicity in CNTN4-positive cancer cells, accompanied by a robust bystander effect comparable to the Dxd conjugate. Additionally, A16.1-Exa exhibited high plasma stability and retained its immune checkpoint-blocking function, supporting T cell-mediated cytotoxicity alongside payload delivery. Treatment with A16.1-Exa demonstrated a very promising anti-tumor effect in a fibrosarcoma xenograft mouse model (HT1080/CNTN4). Investigation of the anti-tumor efficacy in a PDX model was conducted with GENA-104A16 (human IgG4 S228P) antibody in the IND-approved stage, conjugated with MMAF (low DAR) in a pancreatic cancer model. Once the tumor volume reached 195 mm3, mice were randomly divided, and the A16-MMAF conjugate (5 mg/kg) was administered intravenously twice post-grouping. The treatment showed strong anti-tumor activity, leading to tumor regression. Future studies will expand the PDX models and optimize the therapeutic potential of exatecan conjugates to advance the development of CNTN4-targeted therapies, offering a promising approach for treating diverse cancers. Citation Format: Mi Young Cha, Mira Kim, Seungmin Byun, Youngeun Ha, Kitae Park, Bu-Nam Jeon, Hyunuk Kim, Hyunkyung Yu, Hyunjin Yoo, Soojung Moon, Gyeong-Jin Cheon, Boeun Ju, Hansoo Park. Targeting CNTN4 with exatecan-based antibody-drug conjugate for the treatment of solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4270.