Perioprative Study of IBI363 in Patients With MHC-II-Negative Locally Advanced Gastric Cancer

Prior treatment

• Pregnant or lactating women, or women planning to become pregnant within 6 months prior to, during, or after the last dose of the investigational medicinal product.
• Subjects with unresolved Grade \>1 toxicity related to any prior antineoplastic therapy (excluding persistent Grade 2 alopecia, anaemia, peripheral neuropathy, electrolyte abnormalities correctable with treatment, or endocrine abnormalities controlled and stable with hormone replacement therapy).
• Known dihydropyrimidine dehydrogenase (DPD) deficiency (or prior fluorouracil-containing therapy resulting in Grade 3 or higher mucositis).

Other illness

• Known signs of active bleeding from a lesion.
• Known hypersensitivity to any monoclonal antibody or component of the chemotherapy agents (capecitabine, oxaliplatin) (resulting in Grade 3 or higher hypersensitivity reaction).
• History of epileptic seizures, active, newly diagnosed, or untreated central nervous system metastases, spinal cord compression, carcinomatous meningitis, or leptomeningeal metastases.
• Clinically significant cardiovascular or cerebrovascular disease.

Other

• Patients with known dMMR/MSI-H status.
• Oesophageal or pyloric near-obstruction affecting the subject's ability to eat or gastric emptying, or difficulty swallowing tablets.

• Patients voluntarily enrolled in this study and signed informed consent forms;
• Age 18-75 years;
• Pathologically confirmed gastric adenocarcinoma or gastroesophageal junction adenocarcinoma;
• MHC-II negative, with \<5% tumour cells displaying staining \<2+ (grade 2 or stronger);
• Clinically staged as cT3-4aN+M0 gastric or gastroesophageal junction adenocarcinoma confirmed by CT and/or laparoscopy (per AJCC 8th Edition staging);
• No prior antineoplastic therapy for current disease (e.g., surgery, radiotherapy, chemotherapy, targeted therapy, immunotherapy);
• Scheduled for surgical intervention following completion of neoadjuvant therapy;
• Able to swallow tablets orally;
• ECOG performance status 0-1;
• Expected survival ≥6 months.