The 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).
Histologically or cytologically confirmed diagnosis of locally advanced, unresectable, or metastatic gastric, gastroesophageal junction (GEJ), or esophageal adenocarcinoma (EAC).
Human epidermal growth factor receptor 2 (HER2)-negative status, as determined by local assessment using a validated immunohistochemistry assay, in situ hybridization or other amplification testing.
Platinum- and fluoropyrimidine-based chemotherapy.
Therapy with an anti-programmed cell death protein 1 (PD1) or anti-programmed cell death ligand 1 (anti-PD-L1) monoclonal antibody (patients with PD-L1-positive tumors must have received prior PD-1/PD-L1-based therapy).
Active or history of autoimmune disease requiring systemic treatment within 2 years, inflammatory bowel disease (IBD) (Crohn's/ulcerative colitis), celiac disease, or noninfectious enteritis/colitis. (Physiologic hormone replacement not considered systemic treatment).
History or current noninfectious pneumonitis/interstitial lung disease, including radiation-induced pneumonitis requiring steroids or active/recurrent pneumonitis of any etiology.
Documented microsatellite instability-high (MSI-H) or deficient mismatch repair (dMMR) disease by local polymerase chain reaction (PCR) (microsatellite status) and/or informed consent form (ICH) (mismatch repair (MMR)) assay
(For Part 2 only) Has known history of peripheral neuropathy ≥ Grade 2 (per National Cancer Institute(NCI)-Common Tenninology Criteria for Adverse Events (CTCAE) Version 5.0).