FS-1502 Versus T-DM1 for HER2-Positive Unresectable Locally Advanced or Metastatic Breast Cancer

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.