This Phase II clinical study is a prospective, open-label, single-arm trial designed to evaluate the efficacy and safety of combining anti-PD-1 therapy (Serplulimab) with thymalfasin and the SOX chemotherapy regimen as a neoadjuvant treatment for patients with clinical stage III gastric or gastroesophageal junction(GEJ) adenocarcinoma.

This is a prospective, open-label, single-arm phase II clinical study to assess the efficacy and safety of Serplulimab in combination with thymalfasin and SOX regimen for neoadjuvant therapy of locally advanced gastric cancer. It is planned to enroll 30 patients with HER2-negative gastric or gastroesophageal junction adenocarcinoma confirmed by histopathology and/or cytology who were clinically staged as stage III resectable G/GEJ carcinoma as assessed by endoscopic ultrasonography, CT/MRI and other imaging. The primary endpoint of the study was pathological complete response (pCR) rate. The secondary end points included major pathological response(MPR) rate, Tumor Regression Grade (TRG), Clinical downstaging rate (T and/or N downstaging), Objective Response Rate (ORR), Disease Control Rate (DCR), R0 resection rate, Disease-free Survival (DFS), Overall Survival (OS) and treatment-related adverse events (TRAEs).