A novel bispecific ADC targeting Nectin-4 and HER2 demonstrates superior and broad antitumor efficacy in preclinical models

Recently Nectin-4 has emerged as a prominent oncological target due to its high expression across various solid tumors (e.g., urothelial carcinoma, breast cancer, lung cancer, and pancreatic cancer) with restricted expression in normal adult tissues. The clinical significance of Nectin-4 is underscored by the FDA's approval of enfortumab vedotin (EV) for the treatment of urothelial carcinoma. Several novel therapeutic modalities targeting Nectin-4 are under active investigation for cancer therapies. Herein, we describe the design and development of a panel of bispecific antibodies (bsAbs) targeting both Nectin-4 and HER2. Each individual binding arms of the bsAb were engineered and fine-tuned to moderate affinity in order to instill an avidity-driven binding to cells co-expressing both target antigens. The formats of bsAbs were further optimized for favorable developability. The lead BsAb was subsequently conjugated with varieties of cytotoxic payloads to generate bispecific ADC candidates. Several assays were established to exam cell-binding, internalization, and biological activities of the bispecific ADC in cancer cells that express either one or both of the tumor antigens. Internalization assays demonstrated that the BsAbs were endocytosed in tumor cells co-expressing Nectin-4 and HER2 more efficiently than monoclonal antibodies against Nectin-4 or HER2. The antitumor activity of the bispecific ADCs in multiple CDX mouse models were assessed. The lead bsADC demonstrated potent efficacy in CDX models with varying target expression levels, indicating its potential for a broad anti-tumor spectrum for UC and other solid tumors with dual HER2/Nectin-4 antigen expression.