Primary Gastric Adenocarcinoma

This study is a prospective, randomized, open, multicenter phase II clinical trial. It plans to enroll 70 participants with locally advanced gastric and gastroesophageal junction adenocarcinoma (G/GEJ AC) who are assessed as suitable for D2 radical surgery and capable of R0 resection.To evaluate the clinical efficacy and tolerability of IBI343 in combination with sintilimab and SOX regimen for perioperative treatment of resectable, locally advanced gastric or gastroesophageal junction adenocarcinoma.Enroll patients who are CLDN18.2 positive.