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.