In this study, We investigated the efficacy and safty of camrelizumab combined with S-1 maintenance after first-line induction chemotherapy for GC. Patients without progressive disease after 4-6 weeks of first-line chemotherapy with SOX will be treated with camrelizumab combined with S-1.

Inclusion Criteria:

1. Male or female subjects aged from 18 to 75 years old;
2. Subjects with histologically confirmed unresectable locally advanced or metastatic adenocarcinoma of the stomach or gastro-esophageal junction (GEJ);
3. Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0 to 1 at trial entry;
4. Disease must be measurable by Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1);
5. Estimated life expectancy of more than 3 months;
6. Adequate haematological, hepatic and renal functions defined by the protocol;
7. Negative blood pregnancy test at Screening for women of childbearing potential; Highly effective contraception for both male and female subjects if the risk of conception exists;

Exclusion Criteria:

1. Concurrent anticancer treatment such as chemotherapy, radiotherapy, targeted or immunotherapy;
2. Tumor shown to be human epidermal growth factor 2 plus (HER2+);
3. Previous malignant disease (other than gastric cancer) within the last 5 years with the exception of basal or squamous cell carcinoma of the skin or carcinoma in situ (bladder, cervical, colorectal, breast);
4. Severe infection (e.g. need for intravenous antibiotics, antifungal or antiviral drugs) occurred within 4 weeks before the first administration, or fever (>38.5%) of unknown reason occurred during the screening period/before the first administration；
5. Any active autoimmune disease or history of autoimmune disease (such as interstitial pneumonia, uveitis, enteritis, hepatitis, hypophysitis, vasculitis, myocarditis, nephritis, hyperthyroidism, hypothyroidism (can be included after hormone replacement therapy)); The subjects with childhood asthma who had been completely relieved and did not need any intervention or vitiligo in adulthood could be included, but the subjects who needed bronchodilator for medical intervention could not be included;
6. Patients with congenital or acquired immune deficiency, such as human immunodeficiency virus (HIV) infection, active hepatitis B (HBV DNA ≥ 500 IU / ml), hepatitis C (HCV antibody positive and HCV-RNA higher than the detection limit of the analytical method), or co infection of hepatitis B and hepatitis C;
7. Used immunosuppressive drugs within 14 days before the first dose of study drug, excluding nasal and inhaled corticosteroids or physiological doses of systemic corticosteroids;
8. Accination with live or live/attenuated viruses within 28 days of the first dose of camrelizumab and while on trial is prohibited except for administration of inactivated vaccines;
9. History of uncontrolled intercurrent illness including hypertension, active infection, diabetes or cardiac diseases or symptoms;
10. Prior organ transplantation, including allogeneic stem-cell transplantation； Other protocol-defined inclusion/exclusion criteria could apply.