Tislelizumab in Combination With Chemotherapy as First-Line Treatment in Adults With Inoperable, Locally Advanced or Metastatic Gastric, or Gastroesophageal Junction Carcinoma

Key Inclusion Criteria:

1. Locally advanced unresectable or metastatic gastric cancer (GC) or gastroesophagealjunction (GEJ) carcinoma and have histologically confirmed adenocarcinoma

2. No previous systemic therapy for locally advanced unresectable or metastaticgastric/GEJ cancer. NOTE: Participants may have received prior neoadjuvant oradjuvant therapy as long as it was completed and have no recurrence or diseaseprogression for at least 6 months.

3. Eastern Cooperative Oncology Group performance status (ECOG PS) ≤ 1 within 7 daysprior to randomization

4. Adequate organ function ≤ 7 days prior to randomization

Key Exclusion Criteria:

1. Has squamous cell or undifferentiated or other histological type GC

2. Active leptomeningeal disease or uncontrolled brain metastasis

3. Diagnosed with gastric or GEJ adenocarcinoma with positive HER2

4. Prior therapy with an anti-programmed cell death protein-1 (PD-1), anti-programmedcell death protein ligand-1 (PD-L1), anti-programmed cell death protein ligand-2 (PD-L2), or any other antibody or drug specifically targeting T-cell co-stimulationor checkpoint pathways

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.