A Study of AK104 (SC) in Combination With Oxaliplatin and Capecitabine (XELOX) Versus AK104 (IV) in Combination With XELOX in Participants With Unresectable Locally Advanced or Metastatic Gastric Adenocarcinoma or Gastroesophageal Junction Adenocarcinoma

Inclusion Criteria:

1. Histologically confirmed adenocarcinoma of the stomach or gastroesophageal junction (GEJ).
2. Unresectable locally advanced or metastatic adenocarcinoma of the stomach or gastroesophageal junction (GEJ).
3. Participants have not received prior systemic therapy for locally advanced or metastatic gastric or gastroesophageal junction adenocarcinoma.
4. Adequate organ and bone marrow function.
5. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 at enrollment.
6. Measurable disease by RECIST 1.1.

Exclusion Criteria:

1. Receipt of systemic non-specific immunomodulatory therapy (e.g., interleukins, interferons, thymic peptides, etc.) within 2 weeks prior to the first dose.Receipt of Chinese herbal medicines or Chinese patent medicines with anti-tumor indications within 2 weeks prior to the first dose.
2. Deep venous thrombosis within 3 months before first treatment.
3. Uncontrolled arterial hypertension.
4. Bleeding events within the last 1 months.
5. Prior treatment with immune checkpoint inhibitors.
6. Known history of allogeneic organ transplantation and allogeneic hematopoietic stem cell transplantation.