RecruitingPhase 2Drug trialStudy of Denikitug (GS-1811) Given Alone or With Nivolumab or Chemotherapy in Adults With Metastatic Gastric, Gastroesophageal Junction (GEJ), and Esophageal AdenocarcinomasThe goal of this clinical study is to learn more about the study drug, Denikitug (DEN, GS-1811), to evaluate the efficacy and safety of Denikitug Monotherapy and Denikitug-based combinations in in participants with human epidermal growth factor receptor 2 (HER2)-Negative, unresectable, recurrent, and/or metastatic, gastroesophageal junction (GEJ), and esophageal adenocarcinomas. The primary objective of this study is to assess the effect of DEN as a monotherapy or in combination with nivolumab (NIVO) or ramucirumab (RAM) and paclitaxel (PAC) on objective response rate (ORR) as assessed by the investigator according to Response Evaluation Criteria in Solid Tumors (RECIST Version1.1).