Mabwell (688062.SH), an innovation-driven biopharmaceutical company with a fully integrated industry chain, announces the initiation of a Phase III clinical study of its proprietary Nectin-4-targeting ADC (R&D code: 9MW2821) for the treatment of triple-negative breast cancer (TNBC). 9MW2821 is the world's first Nectin-4 ADC to enter Phase III clinical study for TNBC. This marks the fourth pivotal trial initiated for 9MW2821.

This is a randomized, open-label, controlled, multicenter Phase III clinical study designed to evaluate the efficacy of 9MW2821 compared with investigator's choice of chemotherapy in patients with locally advanced or metastatic triple-negative breast cancer who have previously received taxane-based chemotherapy with or without immunotherapy and an antibody-drug conjugate with a topoisomerase inhibitor payload.

Currently, topoisomerase inhibitor-based ADCs (TOPi-ADCs) are among the standard treatment options for patients with advanced TNBC. For TNBC patients who have failed prior TOPi-ADC therapy, treatment remains primarily based on chemotherapy, representing a significant unmet medical need.

9MW2821 is the world's first Nectin-4‑targeting ADC to report efficacy data in triple-negative breast cancer. It has received Fast Track Designation (FTD) from the FDA for the treatment of locally advanced or metastatic Nectin-4‑positive TNBC. TNBC is the third tumor type for which 9MW2821 has entered Phase III pivotal trial, following urothelial carcinoma (UC) and cervical cancer (CC). 9MW2821 has also initiated a clinical study in the United States for ADC-treated TNBC, with the first patient dosed in August 2025.