Inclusion Criteria:

          -  Have a histopathologically confirmed diagnosis of metastatic gastric or
             gastroesophageal junction (GEJ) adenocarcinoma. All histologies of nonsquamous cell
             origin including undifferentiated gastric carcinoma are eligible.

          -  Have not received any prior first-line systemic therapy (prior adjuvant or
             neo-adjuvant therapy is permitted). Participants whose disease has progressed after
             >12 months following the last dose of systemic treatment in the adjuvant/neoadjuvant
             setting are eligible.

          -  Have measurable or nonmeasurable but evaluable disease determined using guidelines in
             Response Evaluation Criteria in Solid Tumors, Version 1.1 (RECIST v 1.1). Baseline
             tumor assessment should be performed using a high resolution computed tomography (CT)
             scan using IV and oral contrast unless clinically contra-indicated. Magnetic resonance
             imaging (MRI) is acceptable if a CT cannot be performed.

          -  Have a performance status of 0 or 1 on the Eastern Cooperative Oncology Group scale at
             baseline.

          -  Have adequate organ function.

          -  Have baseline clinical and laboratory parameters that are consistent with the
             requirements prescribed in respective labels and are suitable for consideration of
             treatment with capecitabine (or 5-FU) and cisplatin (for example, dihydropyrimidine
             dehydrogenase deficiency).

          -  Have an estimated life expectancy of ≥12 weeks in the judgment of the investigator.

        Exclusion Criteria:

          -  Participants with adenocarcinoma of the esophagus are excluded.

          -  Participants with human epidermal growth factor receptor 2 (HER2)-positive status.

          -  Participants receiving chronic therapy with nonsteroidal anti-inflammatory agents.

          -  Have radiation therapy within 14 days prior to randomization.

          -  Have documented brain metastases, leptomeningeal disease or uncontrolled spinal cord
             compression.

          -  Have significant bleeding disorders, vasculitis, or had a significant bleeding episode
             from the gastrointestinal tract within 12 weeks prior to randomization.

          -  Have experienced any arterial thromboembolic event, including myocardial infarction,
             unstable angina, cerebrovascular accident, or transient ischemic attack, within 6
             months prior to randomization.

          -  Have symptomatic congestive heart failure (New York Heart Association II-IV) or
             symptomatic or poorly controlled cardiac arrhythmia.

          -  Have uncontrolled hypertension prior to initiating study treatment, despite
             antihypertensive intervention.

          -  Have undergone major surgery within 28 days prior to randomization, or central venous
             access device placement within 7 days prior to first dose of study treatment, except
             if the procedure is minimally invasive (for example, introduction of peripherally
             inserted central catheter [PICC] line) and the investigator does not anticipate any
             significant bleeding.

          -  Have a history of gastrointestinal perforation and/or fistulae within 6 months prior
             to randomization.

          -  Have a history of inflammatory bowel disease or Crohn's disease requiring medical
             intervention (immunomodulatory or immunosuppressive medications or surgery) ≤12 months
             prior to randomization.

          -  Have an acute or subacute bowel obstruction or history of chronic diarrhea which is
             considered clinically significant in the opinion of the investigator.

          -  The participant has:

               -  cirrhosis at a level of Child-Pugh B (or worse) or

               -  cirrhosis (any degree) and a history of hepatic encephalopathy or clinically
                  meaningful ascites resulting from cirrhosis. Clinically meaningful ascites is
                  defined as ascites resulting from cirrhosis and requiring ongoing treatment with
                  diuretics and/or paracentesis.

          -  Have known allergy or hypersensitivity to any components of study treatment.

          -  Are pregnant or lactating.