Key Inclusion Criteria:

          -  Diagnosis:

               -  For Phase 1a and Phase 1b Cohort 2, have a histologically or cytologically
                  confirmed diagnosis of a locally advanced or metastatic solid tumor for which no
                  standard therapy is available (per local guidance) or standard therapy has
                  failed, or

               -  For Phase 1b Cohort 1, have histologically or cytologically confirmed
                  unresectable, recurrent or metastatic gastric or gastroesophageal junction
                  adenocarcinoma who have not previously received systemic therapy for advanced
                  disease

          -  Measurable disease: Have measurable disease on imaging based on Response Evaluation
             Criteria in Solid Tumors (RECIST) Version 1.1

          -  Have a life expectancy of at least 3 months and an Eastern Cooperative Oncology Group
             (ECOG) performance status of 0 or 1

        Key Exclusion Criteria:

          -  Is currently participating and receiving study therapy or has participated in a study
             of an investigational agent and received study therapy or used an investigation device
             within 3 weeks of the first dose of treatment

          -  Has persisting toxicity related to prior therapy of National Cancer Institute-Common
             Terminology Criteria for Adverse Events Version 5.0 (NCI-CTCAE) Grade >1 severity

          -  Is expected to require any other form of systemic or localized anticancer therapy
             while on trial (including maintenance therapy with another agent, radiation therapy,
             and/or surgical resection)

          -  Has concurrent active malignancy other than nonmelanoma skin cancer, carcinoma in situ
             of the cervix or superficial bladder cancer who has undergone potentially curative
             therapy with no evidence of disease. Individuals with other previous malignancies are
             eligible if disease-free for >2 years

          -  Has a known central nervous system metastasis(es), unless metastases are treated and
             stable and the individual does not require systemic corticosteroids for management of
             CNS symptoms at least 7 days prior to study treatment. Individuals with history of
             carcinomatous meningitis are excluded regardless of clinical stability.

          -  Has active or history of autoimmune disease that has required systemic treatment
             within 2 years of the start of trial treatment

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