Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. announced that its core product, trastuzumab botidotin (A166), a HER2-directed antibody-drug conjugate $(ADC)$, has been approved for marketing by the National Medical Products Administration (NMPA) for the treatment of adult patients with unresectable or metastatic HER2-positive breast cancer who have received one or more prior anti-HER2 therapies. The approval is based on results from a Phase 3 clinical study demonstrating significant improvement in progression-free survival compared to T-DM1. Trastuzumab botidotin is the first domestically developed HER2 ADC in China capable of broadly covering second-line and later HER2-positive breast cancer patients.