Preclinical development of GENA-104 ADC, an exatecan-based novel antibody-drug conjugate targeting CNTN4, for solid tumors

Contactin 4 (CNTN4) has emerged as a novel immune checkpoint molecule, previously shown to suppress T cell activity through interaction with amyloid precursor protein on T cells. Immunohistochemical (IHC) analysis revealed elevated CNTN4 expression across multiple tumor types, most notably in melanoma, liver, and endometrial cancers, while its expression remains low in normal tissues, including immune cells. Leveraging this tumor-specific expression profile, we developed an antibody-drug conjugate (ADC) targeting CNTN4, designated GENA-104A16B.LinkerE.Ex (hereafter referred to as GENA-104 ADC). This ADC consists of GENA-104A16.hIgG1, an anti-CNTN4 antibody engineered with reduced effector function, conjugated via cysteine to a hydrophilic, cleavable linker (Linker E) designed to minimize retro-Michael elimination. Linker E is an improved version of Linker D and demonstrated robust serum stability across species. The payload is exatecan, a potent topoisomerase I inhibitor, incorporated at a high drug-to-antibody ratio. GENA-104 ADC demonstrates potent cytotoxicity in CNTN4-positive cancer cells while maintaining low Fcgamma receptor-mediated cytotoxicity, an advantageous safety feature for ADCs. Mechanistically, it induces tumor cell death through multiple pathways: direct cytotoxicity via internalization, lysosomal trafficking, and payload release; a bystander effect; and immunogenic cell death. Additionally, it enhances T cell-mediated cytotoxicity through immune checkpoint blockade. In vivo , GENA-104 ADC showed robust anti-tumor efficacy in fibrosarcoma (HT1080) and hepatocellular carcinoma (HEPG2) xenograft models. Using IHC analysis, CNTN4 expression was evaluated in 23 patient-derived xenograft (PDX) tissues, including gastric, hepatic, NSCLC, pancreatic, and prostate cancers, as well as sarcoma. High CNTN4 expression (H-score >250) was observed in 11 tissues, notably in 4 of 5 sarcoma models. Moreover, CNTN4 gene expression generally showed a positive correlation with H-scores. Ex vivo and in vivo evaluations of the GENA-104 ADC using PDX models are currently in progress, and updated results will be presented. Non-GLP toxicology in Sprague-Dawley rats and cynomolgus monkeys is in progress, with safety updates to follow. Taken together, these findings support the therapeutic potential of GENA-104 ADC as a targeted treatment strategy for CNTN4-expressing solid tumors. This research represents a meaningful step toward the development of precision oncology therapeutics that may offer improved outcomes for patients with limited treatment options.