Continuation of Serplulimab Plus Chemotherapy After First Progression in Advanced Gastric or Gastro-oesophageal Junction Adenocarcinoma: an Open-label, Randomised Phase II Trial

Inclusion Criteria:

1. Volunteer to participate in this clinical study; completely understand and know thisstudy as well as sign the informed consent form (ICF); be willing to follow and beable to complete all study procedures;
2. Age ≥ 18 years and ≤ 75 years when ICF is signed;
3. Unresectable locally advanced, or metastatic gastric cancer including gastroesophagealjunction cancer, and histopathologically confirmed diagnosis of adenocarcinoma;
4. never received systemic anti-tumor drug therapy before；
5. HER2 negative and PD-L1 CPS≥5;
6. Measurable lesion according to RECIST v1.1 by IRRC;
7. ECOG score 0-1;

Exclusion Criteria:

1. Has other active malignancies within 5 years before the first administration of thestudy drug;
2. Plan to or have previously received organ or bone marrow transplantation;
3. Uncontrollable pleural effusion, pericardial effusion or ascites requiring repeateddrainage;
4. Have received any research drugs within 14 days before the first use of the studydrugs.