A Study to Test Combination Treatments in Participants With Advanced Gastric Cancer

Inclusion Criteria

• Inoperable, advanced or metastatic esophageal cancer (EC), gastric cancer (GC) or gastroesophageal junction (GEJ) carcinoma and have histologically confirmed predominant adenocarcinoma and/or squamous carcinoma
• Eastern Cooperative Oncology Group (ECOG) performance status ≤ 1
• At least 1 lesion with measurable disease

Exclusion Criteria

• HER2-positive tumor and previously untreated with trastuzumab
• Suspected, known or progressive central nervous system metastases
• Other active malignancy requiring concurrent intervention
• Active, known or suspected autoimmune disease Other protocol-defined inclusion/exclusion criteria apply