Inclusion Criteria:

          1. Histologically- or cytologically-confirmed diagnosis of gastric or gastroesophageal
             junction adenocarcinoma.

          2. Confirmed metastatic or locally advanced, unresectable disease.

          3. Progression on or after prior first-line therapy containing any
             platinum/fluoropyrimidine or platinum/taxane doublet.

          4. Willing to provide tumor tissue for PD-L1 biomarker analysis.

          5. Human epidermal growth factor receptor 2 (HER-2/neu) status known and participants
             with HER2/neu positive tumors show documentation of previous treatment containing
             trastuzumab.

          6. ECOG performance status of 0 to 1.

          7. Life expectancy of more than 12 weeks.

          8. Signing the informed consent forms.

          9. Adequate bone marrow, liver and renal function.

        Exclusion Criteria:

          1. Squamous cell or undifferentiated gastric cancer.

          2. Known active central nervous system (CNS) metastases and/or carcinomatous meningitis.

          3. Subjects with an active, known or suspected autoimmune disease. Patients with type I
             diabetes who are receiving a stable dose of insulin, hypothyroidism who only needs
             hormone replacement therapy, and skin diseases (such as eczema, vitiligo, or
             psoriasis) that do not require systemic treatment and do not have acute deterioration
             within 1 year before the screening period, are allowed.

          4. Clinically significant cardiovascular and cerebrovascular diseases.

          5. Subjects with high blood pressure who cannot be controlled well with antihypertensive
             drugs.

          6. Previous digestive tract bleeding history within 3 months or evident gastrointestinal
             bleeding tendency.

          7. Arterial / venous thrombosis events, such as cerebrovascular accidents (including
             transient ischemic attacks, cerebral hemorrhage, cerebral infarction), deep vein
             thrombosis, and pulmonary embolism, occurred within the first 6 months of
             randomization.

          8. Subjects who have previously received anti-PD-1 / PD-L1 monoclonal antibody,
             anti-CTLA-4 monoclonal antibody, and VEGFR small molecule inhibitor therapy.

          9. Prior systemic chemotherapy, radiotherapy and surgery within 4 weeks before the study
             drug administration, or any unresolved AEs > Common Terminology Criteria for Adverse
             Events (CTCAE) Grade 1.