SHR-A1811 Combinations for Advanced/Metastatic HER2 Expression Gastric/Gastroesophageal Junction Adenocarcinoma

This study focuses on a treatment for advanced or metastatic gastric/gastroesophageal junction adenocarcinoma, a type of cancer that affects the stomach and the area where the stomach joins the esophagus. The treatment being studied is SHR-A1811, which is used in combination with chemotherapy and/or immunotherapy. The main goal of this study is to evaluate the safety and effectiveness of this treatment for patients whose cancer expresses a protein called HER2. The study is important as it aims to provide a new treatment option for patients with this type of cancer, potentially improving their care and quality of life. The study consists of two parts, Phase Ib and Phase II. In Phase Ib, the study measures the safety, tolerability, and preliminary antitumor activity of SHR-A1811 in combination with chemotherapy and/or immunotherapy. This is done by evaluating the rates of dose limiting toxicity, occurrence of adverse events, and serious adverse events. In Phase II, the study evaluates the efficacy and safety of the same treatment combination. This is measured by the objective response rate, which is the percentage of patients whose cancer shrinks or disappears after treatment.