Perioperative Ivonescimab Plus S-1 and Oxaliplatin (SOX) for Locally Advanced Gastric or GEJ Adenocarcinoma

The purpose of this clinical trial is to evaluate whether perioperative ivonescimab in combination with S-1 and oxaliplatin (SOX) is effective in treating locally advanced gastric or gastroesophageal junction (GEJ) adenocarcinoma. The study will also assess the safety profile of this treatment regimen. Primary Objective: To determine whether perioperative ivonescimab plus SOX improves the pathological complete response (pCR) rate compared with SOX alone in patients with locally advanced gastric or GEJ adenocarcinoma. Study Design: Participants will be randomly assigned to receive either ivonescimab plus SOX or SOX alone to evaluate the potential added benefit of ivonescimab in this setting. Participation Details: Participants will receive the assigned treatment (ivonescimab plus SOX or SOX alone) every 21 days for approximately 4 months. They will visit the clinic once every 3 weeks for evaluations, laboratory tests, and monitoring. Participants will be asked to keep a daily diary to record any symptoms or side effects experienced during the study.