{"groups":[{"description":"Participants received pembrolizumab 200 mg intravenously (IV) on Day 1 of each 3-week cycle (Q3W). Eligible participants who stopped the initial course of pembrolizumab with Stable Disease (SD) or better but progressed after discontinuation may have been able to initiate a second course of pembrolizumab for up to 17 cycles (up to approximately 1 additional year) at the investigator's discretion.","id":"FG000","title":"Pembrolizumab Monotherapy (Pembro Mono)"},{"description":"Participants received pembrolizumab 200 mg Q3W plus cisplatin 80 mg/m\\^2 Q3W plus 5-fluorouracil (5-FU) 800 mg/m\\^2/day IV infusion on Days 1-5 Q3W. Capecitabine 1000 mg/m\\^2 twice a day (BID) on Days 1-14 Q3W could be substituted for 5-FU per local guidelines. Eligible participants who stopped the initial course of pembrolizumab with Stable Disease (SD) or better but progressed after discontinuation may have been able to initiate a second course of pembrolizumab for up to 17 cycles (up to approximately 1 additional year) at the investigator's discretion.","id":"FG001","title":"Pembrolizumab + SOC Chemotherapy (Pembro Combo)"},{"description":"Participants received placebo IV Q3W plus cisplatin 80 mg/m\\^2 Q3W plus 5-FU 800 mg/m\\^2/day IV infusion on Days 1-5 Q3W. Capecitabine 1000 mg/m\\^2 BID on Days 1-14 Q3W could be substituted for 5-FU per local guidelines.","id":"FG002","title":"Placebo + SOC Chemotherapy (SOC)"}],"periods":[{"dropWithdraws":[{"reasons":[{"groupId":"FG000","numSubjects":"224"},{"groupId":"FG001","numSubjects":"214"},{"groupId":"FG002","numSubjects":"225"}],"type":"Death"},{"reasons":[{"groupId":"FG000","numSubjects":"1"},{"groupId":"FG001","numSubjects":"0"},{"groupId":"FG002","numSubjects":"0"}],"type":"Lost to Follow-up"},{"reasons":[{"groupId":"FG000","numSubjects":"1"},{"groupId":"FG001","numSubjects":"2"},{"groupId":"FG002","numSubjects":"0"}],"type":"Protocol Violation"},{"reasons":[{"groupId":"FG000","numSubjects":"0"},{"groupId":"FG001","numSubjects":"1"},{"groupId":"FG002","numSubjects":"0"}],"type":"Screen Failure"},{"reasons":[{"groupId":"FG000","numSubjects":"15"},{"groupId":"FG001","numSubjects":"15"},{"groupId":"FG002","numSubjects":"6"}],"type":"Transferred to Extension Study"},{"reasons":[{"groupId":"FG000","numSubjects":"8"},{"groupId":"FG001","numSubjects":"10"},{"groupId":"FG002","numSubjects":"4"}],"type":"Did Not Continue on Extension Study"},{"reasons":[{"groupId":"FG000","numSubjects":"7"},{"groupId":"FG001","numSubjects":"15"},{"groupId":"FG002","numSubjects":"15"}],"type":"Withdrawal by Subject"}],"milestones":[{"achievements":[{"groupId":"FG000","numSubjects":"256"},{"groupId":"FG001","numSubjects":"257"},{"groupId":"FG002","numSubjects":"250"}],"type":"STARTED"},{"achievements":[{"comment":"1 participant randomized to the pembro combo arm received pembrolizumab monotherapy by mistake.","groupId":"FG000","numSubjects":"254"},{"groupId":"FG001","numSubjects":"250"},{"groupId":"FG002","numSubjects":"244"}],"type":"Received First Course of Pembrolizumab"},{"achievements":[{"groupId":"FG000","numSubjects":"4"},{"groupId":"FG001","numSubjects":"5"},{"groupId":"FG002","numSubjects":"0"}],"type":"Received Second Course of Pembrolizumab"},{"achievements":[{"groupId":"FG000","numSubjects":"0"},{"groupId":"FG001","numSubjects":"0"},{"groupId":"FG002","numSubjects":"0"}],"type":"COMPLETED"},{"achievements":[{"groupId":"FG000","numSubjects":"256"},{"groupId":"FG001","numSubjects":"257"},{"groupId":"FG002","numSubjects":"250"}],"type":"NOT COMPLETED"}],"title":"Overall Study"}],"preAssignmentDetails":"Of 1,787 screened, 763 were randomized 1:1:1 to the pembrolizumab monotherapy (pembro mono) arm, pembrolizumab plus standard of care (SOC) chemotherapy (pembro combo) arm, or placebo plus SOC chemotherapy (SOC) arm. Per protocol, response/progression or adverse events (AEs) that occurred during the second course were not counted towards efficacy outcome measures or safety outcome measures, respectively.","recruitmentDetails":"Participants with advanced gastric or gastroesophageal junction (GEJ) adenocarcinoma who were programmed death-ligand 1 (PD-L1)-positive (Combined Positive Score \\[CPS\\]≥1) and human epidermal growth factor receptor 2 (HER2/neu)-negative were recruited to the study."}