Apatinib Plus Sintilimab in Advanced Gastric Cancer Refractory to at Least Two Previous Chemotherapy Regimens

Inclusion Criteria: * Age between 20-75 years old * Has histologically confirmed diagnosis of unresectable locally advanced,recurrent or metastatic gastric or GEJ adenocarcinoma * Life expectancy of more than 3 months * Eastern Cooperative Oncology Group (ECOG) performance status was 0 - 1 * Have failed for at least 2 lines of chemotherapy * At least 3 weeks from previous chemotherapy at first dose of trial drug * Resolution of all acute toxic side effects of prior therapy or surgical procedures to grade ≤ 1 National Cancer Institute-Common Toxicity Criteria (NCI-CTC) (except for the laboratory values) * Failure of prior palliative chemotherapy/chemotherapies (at least one irinotecan- or cisplatin-based). Failure is defined either by progression of disease or by significant toxicity that precludes further treatment. * At least one measurable lesion defined by RECIST 1.1 as determined by investigator assessment. * Has adequate organ function * At least 4 weeks from any major surgery (at first dose of trial drug) * Patients must be able to swallow apatinib Exclusion Criteria: * In the past, participants have received anti PD-1, anti PD-L1 or anti PD-L2 drugs or drugs targeting another stimulation or synergistic inhibition of T cell receptors (such as Cytotoxic T-Lymphocyte Antigen 4 \[CTLA-4\] and CD137) * Other co-existing malignancies or malignancies diagnosed within the last 5 years(except cured cutaneum carcinoma or carcinoma in situs of cervix) * Less than 4 weeks from the last clinical trial * Active and uncontrollable bleeding from gastrointestinal tract * Known history of QT interval prolongation, ongoing QT prolongation (\> 450 msec for males or \> 470 msec for females), any cardiac ventricular dysrhythmias, atrial fibrillation of any grade * Hypertension that cannot be controlled by medications (\> 140/90 mmHg despite optimal medical therapy) * Abnormal Coagulation (INR\>1.5、APTT\>1.5 UNL), with tendency of bleed; * Factors that could have an effect on oral medication (such as inability to swallow, chronic diarrhea and intestinal obstruction); * Active uncontrolled infection * Known human immunodeficiency virus (HIV) infection * Symptomatic central nervous metastasis and/or cancerous meningitis * Known allergic/hypersensitivity reaction to any of the components of the treatment; or known drug abuse/alcohol abuse * Pregnant or lactating women