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.

About Triple-Negative Breast Cancer (TNBC)
Triple-negative breast cancer is a subtype of breast cancer characterized by the absence of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) expression. Accounting for approximately 15‑20% of global breast cancer cases, TNBC is generally considered the most aggressive subtype due to the lack of clear therapeutic targets. It is more commonly diagnosed in younger and premenopausal women.

The global incidence of TNBC increased from 320.1 thousand in 2019 to 364.9 thousand in 2024, and is expected to further increase to 382.4 thousand in 2028 and 405.9 thousand in 2032, representing a CAGR of 1.2% and 1.5% respectively. In China, the incidence of TNBC increased from 49.5 thousand in 2019 to 55.9 thousand in 2024, and is expected to further increase to 58.6 thousand in 2028 and 60.4 thousand in 2032, representing a CAGR of 1.2% between 2024 and 2028 and 0.7% between 2028 and 2032.