Dual-target CLDN18.2/HER2 CAR-NK Cells for Advanced Gastric/GEJ Cancer

Inclusion Criteria: * Signed informed consent before any study-specific procedure. * Age 18 to 75 years. * Histologically confirmed unresectable locally advanced or metastatic gastric adenocarcinoma or gastroesophageal junction adenocarcinoma. * Central confirmation of CLDN18.2-positive disease by immunohistochemistry, defined for this draft as membranous CLDN18.2 expression in at least 10% of tumor cells. HER2 testing is required for all subjects; HER2-positive disease is defined as IHC 3+ or IHC 2+/ISH+ using gastric/GEJ testing criteria. * Disease progression after at least 2 prior systemic regimens for advanced disease, including a fluoropyrimidine and platinum agent unless contraindicated or not tolerated. If HER2-positive, prior HER2-directed therapy is expected unless unavailable, contraindicated, or not tolerated. * At least 1 measurable lesion according to RECIST v1.1. * ECOG performance status 0 or 1. * Life expectancy of at least 12 weeks. * Adequate hematologic, renal, hepatic, pulmonary, and cardiac function. * Recovery of prior treatment-related toxicities to Grade 1 or baseline, except alopecia or stable endocrine replacement therapy. * Willingness to provide archival tumor tissue or fresh biopsy material if archival tissue is inadequate for central biomarker confirmation. * Negative pregnancy test for women of childbearing potential and agreement to use effective contraception during the protocol-defined period Exclusion Criteria: * Prior CLDN18.2-targeted or HER2-targeted genetically modified cell therapy (CAR-T, CAR-NK, TCR-T, or similar). * Active or untreated central nervous system metastases or leptomeningeal disease. * Active uncontrolled infection, including uncontrolled HBV, HCV, or HIV viremia. * Active autoimmune disease requiring systemic immunosuppression. * Clinically significant uncontrolled cardiovascular disease, including recent myocardial infarction, unstable angina, uncontrolled arrhythmia, or severe heart failure. * Active gastrointestinal perforation, uncontrolled upper GI bleeding, clinically significant bowel obstruction, or unstable gastric ulcer. * History of solid-organ transplantation or prior allogeneic hematopoietic stem-cell transplantation with active graft-versus-host disease. * Requirement for systemic corticosteroids above physiologic replacement (for example, \>10 mg/day prednisone equivalent) within 7 days before lymphodepletion. * Pregnancy or breastfeeding. * Another active malignancy requiring systemic therapy, except for adequately treated non-melanoma skin cancer, carcinoma in situ, or other protocol-allowed low-risk malignancies. * Any medical, psychiatric, or social condition that, in the investigator's judgment, would make study participation unsafe or would interfere with interpretation of study results.