Among 60 TNBC patients who had already progressed on a topoisomerase I ADC, Mabwell’s 9MW2821 produced a 30% objective response rate and held disease at bay in 80% of cases, with a median duration of response of 8.7 months. Those numbers land at ESMO 2026 as an oral presentation, a format the congress reserves for data committees consider notable, and they matter because this patient group has almost nowhere else to turn: every ADC currently approved for TNBC carries a topoisomerase I payload, so patients who exhaust those agents cycle back to chemotherapy.
The Phase II study (CTR20242376) enrolled patients with locally advanced or metastatic TNBC and tested 9MW2821, a Nectin-4-targeting ADC the company calls Bulumtatug Fuvedotin, as monotherapy or combined with a PD-1 antibody. The data cutoff was April 10, 2026, and median overall survival had not yet matured at that point, leaving the survival story incomplete. Median progression-free survival was 3.7 months, a modest number in isolation but one that needs context: prior-ADC TNBC carries a grim baseline, and an 8.7-month median duration of response in responders suggests the drug’s benefit concentrates in a meaningful subset rather than spreading thin across the whole population.
Mabwell is not treating this as a proof-of-concept endpoint. A Phase III trial in Topo I ADC-pretreated TNBC is already running, and the company describes it as the first Phase III study in this specific prior-treatment population anywhere in its drug class. A Phase Ib study in the United States is also underway, which suggests Mabwell is building toward an eventual regulatory filing outside China. The company has already secured two Breakthrough Therapy Designations from China’s CDE for 9MW2821 in urothelial carcinoma, one for monotherapy and one for combination therapy with an anti-PD-1 agent, giving it a regulatory tailwind in at least one indication as it advances the TNBC program.
The number to watch from the Phase III readout will not be ORR: it will be whether the duration of response seen here holds or contracts in a larger, more heterogeneous population, because 8.7 months of response in 30% of patients is the entire clinical case for this drug in a line where oncologists currently have little to offer.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
