Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. (the "Company") announced that the Company's human epidermal growth factor receptor 2 (HER2)-directed antibody-drug conjugate (ADC) trastuzumab botidotin (also known as A166)  was approved for marketing by the National Medical Products Administration (NMPA) for the treatment of adult patients with unresectable or metastatic HER2-positive breast cancer (BC) who have received one or more prior anti-HER2 therapy.

The approval is based on a multi-center, randomized, open-label, controlled, Phase 3 KL166-III-06 study that evaluates the efficacy and safety profile of trastuzumab botidotin versus T-DM1 in patients with HER2-positive unresectable or metastatic BC who have received prior trastuzumab and taxane-containing regimens. At a pre-specified interim analysis, trastuzumab botidotin monotherapy demonstrated a statistically significant and clinically meaningful improvement in the primary endpoint of progression-free survival (PFS) as assessed by the blinded independent central review (BICR) compared with T-DM1; the beneficial trend for overall survival (OS) of trastuzumab botidotin was also observed. Results from this study will be presented as an oral report at the 2025 European Society for Medical Oncology (ESMO) Congress held in Berlin, Germany (Presentation # LBA24, Proffered paper session 1: Breast cancer, metastatic).

The Company has initiated an open, multi-center Phase 2 clinical study of trastuzumab botidotin in the treatment of HER2+ unresectable or metastatic BC that previously received a topoisomerase inhibitor ADC.

Dr. Michael Ge, CEO of Kelun-Biotech said, "We are thrilled to see our first HER2 ADC drug, trastuzumab botidotin, successfully approved for market. This marks a significant advancement in the treatment of HER2-positive breast cancer. As China's first domestically developed HER2 ADC capable of broadly covering 2L+ HER2 BC patients, trastuzumab botidotin leverages its differentiated structural design to deliver superior efficacy while addressing unmet clinical needs in this population."