Mabwell (688062.SH, 02493.HK), an innovation-driven biopharmaceutical company with a fully integrated industry chain, will present Phase II clinical data on its Nectin-4-targeting antibody-drug conjugate (ADC) 9MW2821 (Bulumtatug Fuvedotin, "BFv") in locally advanced or metastatic triple-negative breast cancer (TNBC) as an oral presentation at the 2026 European Society for Medical Oncology (ESMO) Congress. The study focuses on patients previously treated with an ADC carrying a topoisomerase I inhibitor payload (hereinafter "Topo I ADC-pretreated"). The abstract is now available on the congress website.

The study (CTR20242376) is designed to evaluate the efficacy and safety of 9MW2821 as monotherapy or in combination with a PD-1 monoclonal antibody in patients with locally advanced or metastatic TNBC. As of April 10, 2026, among 60 efficacy-evaluable Topo I ADC-pretreated patients, the objective response rate (ORR) was 30.0%, the disease control rate (DCR) was 80.0%, the median progression-free survival (mPFS) was 3.7 months, the median duration of response (mDOR) was 8.7 months, and the median overall survival (mOS) was not yet mature. No new safety signals were observed during this follow-up period. The study results indicate that 9MW2821 has a manageable safety profile and positive therapeutic effects in patients with TNBC. 

In 2024, an estimated 375,800 women in China were newly diagnosed with breast cancer and approximately 73,000 died of the disease.[1] TNBC accounts for approximately 15%–20% of all breast cancers and is highly aggressive with a poor prognosis. Currently, all ADCs approved for TNBC use a topoisomerase I inhibitor payload. After progression on these agents, chemotherapy remains the mainstay of care and new treatment options are urgently needed.

[1] Xia C, Li H, Wu C, Chen W. Cancer burden and control in China. Nat Rev Clin Oncol. 2026. doi:10.1038/s41571-026-01165-8

About 9MW2821

9MW2821 is a Nectin-4-targeting ADC independently developed by Mabwell on its proprietary ADC development platform. It is currently conducting multiple clinical studies for several indications including urothelial carcinoma (UC), cervical cancer (CC), triple-negative breast cancer (TNBC), and esophageal cancer (EC), with a cumulative clinical enrollment of over 2,200 patients. Currently, four pivotal Phase III clinical trials of 9MW2821 are underway, including UC monotherapy and combination therapy, CC monotherapy, and monotherapy for topoisomerase I inhibitor-payload ADC-pretreated TNBC. 9MW2821 has been granted Breakthrough Therapy Designation by the Center for Drug Evaluation (CDE) for UC, both as monotherapy and in combination therapy. It is the first Nectin-4-targeting agent to enter Phase III clinical study in CC, and the first agent of any target to enter Phase III clinical study specifically in patients with Topo I ADC-pretreated TNBC.

The Phase III clinical trials of 9MW2821 for UC monotherapy, UC combination therapy, and CC monotherapy are planned to undergo interim analyses in 2026, and it is expected to, based on the interim analysis data, submit applications for pre-NDA meetings to the CDE under the National Medical Products Administration (NMPA). Multiple Phase I/II clinical trials are ongoing in parallel and progressing rapidly. In addition, the TNBC (Topo I ADC-pretreated) monotherapy has entered into Phase Ib clinical trials in the United States.