DP303c in Patients With HER2-positive Unresectable Locally Advanced, Relapsed, or Metastaticbreast Cancer

This is a multi-center, open-lable, single-arm Phase II study to evaluate the efficacy and safety of DP303c in patients with HER2-positive unresectable locally advanced, relapsed, or metastatic breast cancer. Patients will be treated with DP303c injection at 3.0 mg/kg every 3 weeks. Patients will receive DP303c until disease progression, intolerable toxicity, withdrawal of informed consent, death, or any other reasons for treatment discontinuation, whichever occurs first.