Mabwell reports a 30% response rate and 8.7-month median response duration for 9MW2821 in ADC-pretreated triple-negative breast cancer ahead of ESMO 2026.
Written By: Neha Vishwakarma, PharmD
Reviewed By: Pharmacally Editorial Team
Mabwell (688062.SH, 02493.HK) will present Phase 2 clinical data on 9MW2821 (bulumtatug fuvedotin, BFv), its investigational Nectin-4-targeting antibody-drug conjugate (ADC), at the European Society for Medical Oncology (ESMO) Congress 2026 in Madrid, Spain, from October 23 to 27. The oral presentation, abstract 4640RO, is scheduled for October 26 in the advanced breast cancer session and will be delivered by Prof. Zhang Jian of Fudan University Shanghai Cancer Center.
The study evaluates 9MW2821 in patients with locally advanced or metastatic triple-negative breast cancer (TNBC) previously treated with an ADC carrying a topoisomerase I (Topo I) inhibitor payload. Mabwell reported an objective response rate of 30.0% among 60 efficacy-evaluable patients, although the available preview does not provide a breakdown by treatment cohort.
TNBC and the Need for Additional Treatment Options
TNBC accounts for approximately 15% to 20% of breast cancers and is associated with aggressive disease and poor prognosis. ADCs approved for TNBC use Topo I inhibitor payloads, leaving an unmet treatment need for patients whose disease progresses following these therapies.
In China, an estimated 375,800 women were newly diagnosed with breast cancer in 2024, while approximately 73,000 died of the disease, according to the cited analysis by Xia and colleagues in Nature Reviews Clinical Oncology.
After progression on a Topo I-based ADC, chemotherapy remains an important treatment option. Therapies directed at alternative targets and using different payloads are therefore being investigated to address this treatment gap.
About 9MW2821
9MW2821 is a Nectin-4-targeting ADC developed by Mabwell using its proprietary ADC platform. The company is studying the candidate in urothelial carcinoma, cervical cancer, TNBC and esophageal cancer, with cumulative clinical enrollment exceeding 2,200 patients across its development programme.
Four pivotal Phase 3 trials are underway, covering urothelial carcinoma as monotherapy and in combination, cervical cancer as monotherapy, and Topo I ADC-pretreated TNBC as monotherapy. China’s Center for Drug Evaluation has granted Breakthrough Therapy Designation for urothelial carcinoma in both monotherapy and combination settings.
Mabwell describes 9MW2821 as the first Nectin-4-targeting agent to enter Phase 3 development for cervical cancer and the first agent of any target to enter Phase 3 specifically for Topo I ADC-pretreated TNBC.
Phase 2 Study Design and Efficacy Results
The Phase 2 study, CTR20242376, evaluates 9MW2821 alone or in combination with a PD-1 monoclonal antibody in locally advanced or metastatic TNBC. According to Mabwell’s October 19, 2026 announcement, the efficacy data had a cutoff date of April 10, 2026.
Among 60 efficacy-evaluable patients previously treated with a Topo I ADC, the company reported:
Endpoint | Result |
Objective response rate (ORR) | 30.0% |
Disease control rate (DCR) | 80.0% |
Median progression-free survival (mPFS) | 3.7 months |
Median duration of response (mDOR) | 8.7 months |
Median overall survival (mOS) | Not yet mature |
The preview does not disclose how many patients received monotherapy versus the PD-1 combination. It also omits confidence intervals, subgroup results and the distribution of previous treatment lines, limiting assessment of the precision and generalizability of the findings.
Safety and Tolerability
Mabwell reported no new safety signals during follow-up and characterized the safety profile as manageable. However, the preview does not provide adverse-event frequencies, severity grades or treatment discontinuation rates.
The full presentation should clarify the incidence and severity of skin reactions, peripheral neuropathy and hematologic toxicities, alongside other treatment-emergent adverse events. Without these details, the tolerability profile cannot be independently assessed from the preview alone.
Development Plans
Mabwell plans interim analyses in 2026 for its Phase 3 urothelial carcinoma monotherapy, urothelial carcinoma combination and cervical cancer monotherapy trials. The company expects to use the results to pursue pre-NDA meetings with China’s Center for Drug Evaluation.
For TNBC, a randomized, open-label Phase 3 study comparing 9MW2821 with investigator’s-choice chemotherapy was initiated in April 2026. The company has also advanced 9MW2821 monotherapy into Phase 1b testing in the United States for ADC-pretreated TNBC.
9MW2821 remains investigational and has not been approved by a regulatory authority.
Clinical Interpretation
The 30.0% response rate and median response duration of 8.7 months indicate antitumour activity in patients whose disease has progressed following Topo I-based ADC treatment. However, the median progression-free survival of 3.7 months suggests that the duration of disease control remains an important consideration.
The findings do not establish that 9MW2821 overcomes resistance to Topo I ADCs, nor do they demonstrate superiority over chemotherapy. The absence of confidence intervals, treatment-cohort breakdowns and detailed patient characteristics further limits interpretation. The randomized Phase 3 comparison will be critical in determining whether the observed activity translates into a clinically meaningful improvement in outcomes.
References
Mabwell. ESMO 2026 Preview: Mabwell to Present Clinical Results for Nectin-4-Targeting ADC 9MW2821 in ADC-Pretreated Triple-Negative Breast Cancer. October 19, 2026.
A Clinical Study of 9MW2821 (and PD-1 Inhibitor) in Locally Advanced or Metastatic Triple-Negative Breast Cancer, ClinicalTrials.gov ID NCT06908928
A Dose Randomization Study of Bulumtatug Fuvedotin in TNBC Patients Previously Treated with ADCs, ClinicalTrials.gov ID NCT06908928
Xia, C., Li, H., Wu, C. et al. Cancer burden and control in China: landscape, trends and challenges. Nat Rev Clin Oncol 23, 694–711 (2026). https://doi.org/10.1038/s41571-026-01165-8
About the Writer
Neha Vishwakarma (LinkedIn) is a Pharm.D professional with experience in clinical pharmacy, pharmacovigilance, and clinical research. She has hands-on experience in ADR assessment, ICSR processing, medication safety, and clinical data evaluation. Her research background in surgical site infections and antibiotic use supports her focus on evidence-based healthcare writing.