Chengdu – September 16, 2026 -- Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. (6990.HK) said phase III results for its HER2-targeted antibody-drug conjugate trastuzumab botidotin have been published in the Journal of Clinical Oncology, a journal with an impact factor of 44.7, after the drug outperformed Roche's trastuzumab emtansine (T-DM1) in a head-to-head trial and secured approval from China's National Medical Products Administration.
Trial data show median progression-free survival more than doubled versus T-DM1
The randomized, open-label study enrolled 365 patients with HER2-positive unresectable or metastatic breast cancer who had previously received trastuzumab and taxane-based regimens, randomizing them 1:1 to trastuzumab botidotin or T-DM1. As of the April 26, 2025 data cutoff, with a median follow-up of 14.9 months, median PFS reached 11.1 months in the trastuzumab botidotin arm versus 4.4 months for T-DM1, a hazard ratio of 0.39 that met the study's primary endpoint. The benefit held across all prespecified subgroups.
Response rates and duration favor the new ADC
Objective response rate stood at 76.9% for trastuzumab botidotin against 53.0% for T-DM1, with median duration of response of 12.2 months compared with 5.7 months. Overall survival data remain immature in both arms, but investigators observed a trend toward benefit, with a 38% reduction in risk of death for patients on trastuzumab botidotin.
Safety profile shows lower toxicity rates than T-DM1
Patients on trastuzumab botidotin recorded a low incidence of interstitial lung disease and lower rates of hematologic, hepatic and gastrointestinal toxicities than the T-DM1 group, along with fewer serious adverse events and treatment discontinuations. The most common treatment-related adverse events were ocular in nature, described as recoverable or reversible with standardized management protocols.
NMPA approval marks first domestic HER2 ADC cleared for this indication
Based on the trial results, trastuzumab botidotin has been approved by the NMPA for second-line or later treatment of HER2-positive breast cancer, making it the first domestically developed HER2 ADC cleared for this indication in China. The study represents the first Chinese phase III trial of a HER2 ADC to post positive head-to-head results against T-DM1. Findings were first presented as a late-breaking abstract at the 2025 European Society for Medical Oncology Congress. Co-senior authors on the JCO publication include Professor Xichun Hu and Professor Hongxia Wang of Fudan University Shanghai Cancer Center and Dr. Junyou Ge of the National Engineering Research Center of Targeted Biologics.
Kelun-Biotech has also initiated an open, multi-center phase 2 study evaluating trastuzumab botidotin in HER2-positive breast cancer patients previously treated with a topoisomerase inhibitor payload ADC.