Neoadjuvant Iparomlimab and Tuvonralimab With Nab-P-SOX in Locally Advanced Gastric or Gastroesophageal Junction Cancer

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.

Inclusion Criteria: * 1\. Age 18-75 years. 2. Histologically confirmed gastric or gastroesophageal junction (GEJ) adenocarcinoma, with clinical stage cT3-4aN+M0. 3\. Resectable disease, as determined by the surgical investigator. 4. No prior radiotherapy, chemotherapy, or other systemic antitumor therapy. 5. HER-2 negative. 6. Eastern Cooperative Oncology Group (ECOG) performance status 0-1. 7. Life expectancy \> 6 months. 8. Adequate organ function, defined as: hemoglobin (Hb) ≥ 90 g/L, absolute neutrophil count (ANC) ≥ 1.5 × 10⁹/L, platelet count (PLT) ≥ 100 × 10⁹/L, serum creatinine (Cr) ≤ 1.5 × upper limit of normal (ULN), alanine/aspartate aminotransferase (ALT/AST) ≤ 2.5 × ULN, total bilirubin (TBIL) ≤ 1.5 × ULN, amylase/lipase \< 1.5 × ULN, international normalized ratio (INR)/activated partial thromboplastin time (APTT) ≤ 1.5 × ULN, urine protein \< 2+, left ventricular ejection fraction (LVEF) ≥ 50%, etc. 9\. Women of childbearing potential must be non-pregnant, non-lactating, and agree to use adequate contraception. 10\. Voluntary provision of written informed consent, with good treatment compliance anticipated. Exclusion Criteria: * 1\. Known allergy or hypersensitivity to the investigational drug(s) or any of their excipients. 2\. History of other prior antitumor therapy. 3. Therapeutic full-dose anticoagulation or thrombolysis within 10 days prior to the first dose. 4\. Requirement for systemic corticosteroids or immunosuppressive therapy within 2 weeks prior to the first dose. 5\. Active autoimmune disease, or an autoimmune disease with a high risk of relapse upon immunosuppression. 6\. Within 6 months: gastrointestinal perforation, fistula, or obstruction; Crohn's disease or ulcerative colitis; or extensive intestinal resection. 7\. Symptomatic and uncontrolled brain or leptomeningeal metastases. 8. History of interstitial lung disease/pneumonitis, or pulmonary hypertension. 9. History of organ transplantation. 10. Uncontrolled hypertension (\>150/100 mmHg), diabetes mellitus, or cardiac arrhythmia. 11\. Arterial or venous thrombotic/embolic event within 6 months. 12. Within 12 months: myocardial infarction, unstable angina, or New York Heart Association (NYHA) class III/IV heart failure. 13\. Drainage of ascites, pleural effusion, or pericardial effusion within 4 weeks prior to enrollment. 14\. Non-healing wound, active ulcer, or untreated fracture. 15. Other active malignancy (except cured basal/squamous cell skin carcinoma or in situ carcinoma). 16\. Active HIV, HBV, or HCV infection. 17. Major surgery within 4 weeks prior to the first dose. 18. Any other condition that, in the investigator's judgment, renders the patient unsuitable for study participation.