The goal of this clinical trial is to explore the efficacy and safety in patients with gastric adenocarcinoma or adenocarcinoma of esophagogastric junction. The main questions it aims to answer are:

• Does this therapy have a promising efficacy?
• Does this therapy have a manageable toxicity? Participants will receive fruquintinib plus sintilimab as first-line therapy for gastric cancer.

Inclusion Criteria:

• Histological or cytological confirmed advanced, recurrent, of metastatic gastric adenocarcinoma or adenocarcinoma of esophagogastric junction;
• ECOG PS: 0-2;
• Adequate hepatic, renal, heart, and hematologic functions;
• At least one measurable lesion (according to RECIST1.1);
• Haven't received any systematic treatment for the cancer involved;
• Expected survival > 12 weeks;
• Contraception until 6 months after the study termination;
• Signed informed consent.

Exclusion Criteria:

• Her-2-positive gastric cancer, or exposed to any immune checkpoint inhibitor;
• Participated in another study;
• Immunodeficiency;
• Received allograft；
• Unmanageable hypertension, diabetes, or coronary disease;
• Have difficulty in taking medicine, or active bleeding;
• Pulmonary tuberculosis, or interstitial lung disease that needs steroid therapy;
• Infection of HIV, HBV, HCV, or other unmanageable infection;
• Other malignant tumor history;
• Allergic to the test drug;
• Other diseases which will affect the results of this study;
• Received resection of stomach;
• Taking anti-tumor traditional Chinese Medicine;
• Severe active bleeding.

There is not a plan to make IPD available.