nab-P-SOX（nab-paclitaxel, oxaliplatin, S-1）

This is a single-center, single-arm, phase 2 clinical study testing a new neoadjuvant (pre-surgery) treatment for patients with locally advanced gastric cancer or gastroesophageal junction (GEJ) cancer. The treatment combines two parts: (1) a novel bispecific immunotherapy drug, iparomlimab and tuvonralimab (Qibain®) , which helps the immune system attack cancer cells by blocking the PD-1 and CTLA-4 pathways; and (2) a standard chemotherapy regimen called nab-P-SOX, made up of nab-paclitaxel, oxaliplatin, and S-1. About 28 adults (aged 18-75) with previously untreated, HER2-negative, locally advanced gastric or GEJ adenocarcinoma (clinical stage cT3-4aN+M0) will receive this combination before their planned surgery. The main goal is to see how well the tumor shrinks, measured by the objective response rate (RECIST v1.1). Secondary goals include the rate of complete response in the removed tumor tissue (pathological complete response), how often the cancer is removed with clear margins (R0 resection), survival outcomes, and the safety of the treatment. All participants will be closely followed to track both benefits and side effects. The study is sponsored by Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, with funding and the study drug provided by Qilu Pharmaceutical Co., Ltd.