['metastatic gastric adenocarcinoma', 'gastroesophageal junction adenocarcinoma']
['ramucirumab', 'placebo', 's-1', 'oxaliplatin', 'paclitaxel']

        Inclusion Criteria:

          -  Have a histopathologically or cytologically confirmed diagnosis of metastatic gastric
             or GEJ adenocarcinoma. Participants with esophageal cancer are not eligible.

          -  Have not received any prior first-line systemic therapy for gastric or GEJ
             adenocarcinoma (prior adjuvant or neoadjuvant therapy is permitted). Participants
             whose disease has progressed after >24 weeks 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).

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

          -  Have adequate organ function.

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

          -  Eligible participants of reproductive potential (both sexes) must agree to use
             contraception (hormonal or barrier methods) during the study period and at least 6
             months after the last dose of study treatment or longer if required per local
             regulations.

          -  Are willing to provide a blood sample for research purposes. Submission of a blood
             sample is mandatory for participation in this study unless restricted by local
             regulations or ethical review boards (ERBs); submission of a tumor tissue sample is
             optional.

        Exclusion Criteria:

          -  Participants with human epidermal growth factor receptor 2 (HER2)-positive status as
             determined per local standards. Participants with a negative test or having an
             indeterminate result due to any reason are eligible, provided these participants are
             not eligible for treatment directed against tumors which overexpress HER2.

          -  Have radiation therapy within 14 days prior to randomization. Any lesion requiring
             palliative radiation or which has been previously irradiated cannot be considered for
             response assessment.

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

          -  Have undergone major surgery within 28 days prior to randomization.

          -  Are currently enrolled in, or discontinued study drug within the last 28 days from, a
             clinical trial involving an investigational product or non-approved use of a drug or
             device (other than the study drug used in this study), or are concurrently enrolled in
             any other type of medical research judged not to be scientifically or medically
             compatible with this study. Participants participating in surveys or observational
             studies are eligible to participate in this study.

          -  Are pregnant or breast feeding. Females of childbearing potential must have a negative
             serum or urine pregnancy test within 7 days prior to first dose of study treatment.

          -  Have any prior malignancies.

          -  Have any condition (eg, psychological, geographical, or medical) that does not permit
             compliance with the study and follow-up procedures or suggest that the participant is,
             in the investigator's opinion, not an appropriate candidate for the study.
      