Abstract Nectin-4 is a validated therapeutic target for several epithelial cancers. Enfortumab vedotin (EV), the first FDA-approved Nectin-4-directed ADC, has demonstrated significant clinical benefit. However, its efficacy remains limited by multiple mechanisms, P-glycoprotein (P-gp)-mediated efflux, the emergence of EV-resistant tumor cells contribute to reduce cytotoxic activity where its short plasma half-life necessitates more frequent dosing. In addition, off-target hematological toxicities have been observed, potentially resulting from suboptimal linker stability and premature payload release in circulation. To address these limitations, we developed OBI-904, a next-generation Nectin-4-targeting ADC. OBI-904 is a homogeneous ADC and consists of a novel anti-Nectin-4 antibody (10K06) conjugated to an exatecan payload through a stable glycan-based site-specific linker platform. The 10K06 and Enfortumab antibody epitopes were compared by sequence and structural analysis. Cell binding, internalization, and keratinocyte binding were evaluated by flow cytometry and confocal microscopy. Cross-species reactivity was tested by ELISA. Cytotoxicity was tested in Nectin-4 low 3D spheroid models, bystander activity in co-cultures of Nectin-4-positive and -negative cells, and resistance mechanisms in P-gp-overexpressing and EV-resistant cell lines. The 10K06 antibody binds to the Nectin-4 IgV domain (amino acids 86-92) and shows good binding affinity and internalization in cell-based assays, ensuring efficient target engagement. In addition, OBI-904 shows reduced binding to keratinocytes compared with EV, suggesting a lower risk of skin toxicity. We also confirmed that 10K06 recognizes human and cynomolgus Nectin-4 but not murine Nectin-4, supporting its suitability for preclinical evaluation in non-human primates. OBI-904 exhibited superior cytotoxic potency in Nectin-4 low-expressing cell lines under 3D spheroid culture conditions, consistent with the high potency and membrane permeability of its exatecan payload. Moreover, OBI-904 mediated a robust bystander effect in co-culture systems with Nectin-4-positive and -negative cells, indicating efficient payload diffusion into neighboring tumor cells. Importantly, OBI-904 retained strong cytotoxic activity in P-gp-overexpressing and EV-resistant tumor cells. Collectively, these findings establish OBI-904 as a potent, next-generation Nectin-4 ADC with reduced skin binding, enhanced cytotoxicity, a pronounced bystander effect, and the ability to overcome P-gp-mediated and EV-acquired resistance. These attributes position OBI-904 as a promising clinical candidate with the potential to achieve improved therapeutic outcomes in Nectin-4-expressing cancers. Citation Format: Yuan-Liang Wang, Chi-Huan Lu, Woan-Eng Chan, Shin-Jin Lin, Ting-Yu Chang, Hong-Syuan Lin, Wei-Jhen Huang, Ya-Chi Chen. OBI-904, a next-generation nectin-4-targeting exatecan ADC, demonstrates enhanced cytotoxicity and overcomes enfortumab vedotin resistance abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1729.
Wang et al. (Fri,) studied this question.