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

This study is testing a new drug called IBI363 given before surgery in patients with advanced stomach cancer or cancer at the junction where the esophagus meets the stomach. The goal is to shrink the tumor before surgery to improve the chances of a successful operation. **You may be eligible if...** - You are between 18 and 75 years old - You have been diagnosed with stomach or gastroesophageal junction adenocarcinoma confirmed by biopsy - Your tumor has a specific protein profile (MHC-II negative) - Your cancer is locally advanced (has spread to nearby lymph nodes but not to distant organs) - You have not received any prior cancer treatment for this disease - You are physically fit enough to undergo surgery and can swallow tablets - Your expected survival is at least 6 months **You may NOT be eligible if...** - You are pregnant, breastfeeding, or planning to become pregnant - There are signs of active bleeding from the tumor - Your cancer has a specific genetic marker called dMMR/MSI-H - You have blockage in the esophagus or stomach that makes eating or swallowing difficult - You have serious heart or brain conditions - You have a known allergy to the chemotherapy drugs used (capecitabine or oxaliplatin) Talk to your doctor to see if this trial is right for you.