Inclusion Criteria:  Voluntarily participate in this study and provide written informed consent Age ≥ 18 years and ≤70 years, male or female Pathological confirmed locally advanced, unresectable or metastatic gastric adenocarcinoma, esophagogastric junction adenocarcinoma and lower esophagus adenocarcinoma that are resistant to anti-PD-1/L1 antibodies Able and willing to provide tumor tissue At least one measurable extracranial target lesion according to iRECIST Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1 Life expectancy ≥3 months  Exclusion Criteria:  History of other primary malignancies within 5 years except adequately treated in situ carcinoma of the cervix or non-melanoma carcinoma of the skin Had systemic diseases that were difficult to control within 4 weeks prior to screening History of anti-PD-1 antibodies related adverse reactions that led to the permanent withdrawal of anti-PD-1 therapy History of coagulation disorders Mechanical or paralytic obstruction of the gastrointestinal tract Anticipated to receive a great number of antibiotics during study period