This is an open-label, multicenter, phase II study of DP303c injection in patients with HER2-positive advanced or metastatic gastric cancer with two parts. In part 1, patients will be treated with DP303c injection at three dose levels (2.0 mg/kg，2.5 mg/kg or 3.0 mg/kg) every 3 weeks to determine the recommended dose . Once the recommended dose has been established in part 1, patients will be enrolled into 4 cohorts in part 2.
This study is an open-label, multicenter, phase II study to evaluate the efficacy and safety of DP303c injection in patients with HER2-positive advanced or metastatic gastric cancer.