This study is a multicenter, open-label, randomized controlled phase III clinical study to compare the efficacy and safety of FS-1502 versus T-DM1 in patients with HER2-positive unresectable locally advanced or metastatic breast cancer. Patients who meet the inclusion and exclusion criteria will be randomized into the test group (FS-1502) or control group (T-DM1) in a 1:1 ratio. Patients in the test group will receive FS-1502 2.3 mg/kg, and those in the control group will receive T-DM1 3.6 mg/kg, by intravenous drip every 3 weeks. Patients will be treated until disease progression (PD), intolerable toxicity, withdrawal of consent, death, or other protocol-specified reasons. According to the Response Evaluation Criteria in Solid Tumours (RECIST 1.1), tumor assessment will be performed every 6 weeks (± 7 days) for the first 12 months and every 12 weeks (± 7 days) after 12 months until PD, withdrawal of consent, or death. Efficacy evaluation will be performed by the investigator and the Independent Review Committee (IRC), respectively.
This study is designed to compare the anti-tumor activity as well as the safety and efficacy of FS-1502 versus T-DM1 in HER2-positive, unresectable locally advanced or metastatic breast cancer subjects previously treated with trastuzumab and taxane.