Shanghai – October 18, 2026 -- Mabwell's Nectin-4-targeting antibody-drug conjugate 9MW2821 (Bulumtatug Fuvedotin, "BFv") achieved a 30.0% objective response rate in 60 efficacy-evaluable triple-negative breast cancer (TNBC) patients previously treated with a topoisomerase I (Topo I) ADC, according to Phase II data to be presented orally at the 2026 European Society for Medical Oncology (ESMO) Congress.
Phase II data show 80% disease control and 8.7-month response duration
The study (CTR20242376) evaluates 9MW2821 as monotherapy or combined with a PD-1 monoclonal antibody in locally advanced or metastatic TNBC. Data are as of April 10, 2026.
Beyond the 30.0% ORR, the disease control rate was 80.0%. Median progression-free survival reached 3.7 months, and median duration of response was 8.7 months. Median overall survival is not yet mature. Mabwell reported no new safety signals during follow-up and described the safety profile as manageable. The abstract is available on the congress website.
Treatment gap: all approved TNBC ADCs share one payload class
All ADCs currently approved for TNBC use a Topo I inhibitor payload, according to Mabwell. After progression on these agents, chemotherapy remains the mainstay of care. TNBC accounts for roughly 15%-20% of all breast cancers and is highly aggressive with a poor prognosis.
In China, an estimated 375,800 women were newly diagnosed with breast cancer in 2024, and about 73,000 died of the disease.
Four Phase III trials underway across 2,200+ enrolled patients
9MW2821 has accumulated clinical enrollment of more than 2,200 patients across urothelial carcinoma (UC), cervical cancer (CC), TNBC and esophageal cancer. Four pivotal Phase III trials are running: UC monotherapy, UC combination therapy, CC monotherapy, and monotherapy in Topo I ADC-pretreated TNBC.
Mabwell says it is the first agent of any target to enter Phase III specifically in Topo I ADC-pretreated TNBC, and the first Nectin-4-targeting agent in Phase III for CC. China's Center for Drug Evaluation (CDE) granted Breakthrough Therapy Designation for UC, as monotherapy and in combination.
Interim analyses due in 2026 could trigger pre-NDA meeting requests
Interim analyses are planned in 2026 for the UC monotherapy, UC combination and CC monotherapy Phase III trials. Based on those results, Mabwell expects to apply for pre-NDA meetings with the CDE under the National Medical Products Administration. In the United States, TNBC monotherapy in Topo I ADC-pretreated patients has entered Phase Ib trials.