GB1275 Monotherapy and in Combination With an Anti-PD1 Antibody in Patients With Specified Advanced Solid Tumors or in Combination With Standard of Care in Patients With Metastatic Pancreatic Adenocarcinoma

Inclusion Criteria: * Subject has a performance status of 0 or 1 on the Eastern Cooperative Oncology Group (ECOG) Performance Scale. * Women of childbearing potential must use an acceptable method of contraception Phase 1 Subjects with the the following: * Regimen A and B: * pancreatic adenocarcinoma, * esophageal adenocarcinoma, or esophageal squamous cell carcinoma, or * gastric/gastroesophageal junction adenocarcinoma, or * TNBC, or * prostate cancer, or * colorectal adenocarcinoma, or subjects with tumor types that have progressed after receiving initial treatment benefit rom the last single agent checkpoint inhibitor that is approved for the indication or in combination with standard of care therapy, for example, non-small cell lung cancer, small cell lung cancer, head and neck squamous cell carcinoma, urothelial carcinoma, renal cell carcinoma, and hepatocellular carcinoma, etc. * Regimen C: newly diagnosed stage IV pancreatic cancer Phase 2 * Cohort 1: pancreatic cancer. * Cohort 2: colorectal cancer * Cohort 3: gastric/GEJ adenocarcinoma Exclusion Criteria: * History of another malignancy within 2 years prior to first study drug(s) administration, unless the malignancy was treated with curative intent and the likelihood of relapse is \<5% in 2 years * Pregnant or nursing * Known history of testing positive for human immunodeficiency virus (HIV) * Gastrointestinal (GI) tract disease causing the inability to take oral medication. * Positive test for Hepatitis B virus surface antigen (HBsAg) or a and/or positive Hep C antibody result with detectable hepatitis C virus (HCV) ribonucleic acid (RNA) indicating acute or chronic infection. Other protocol-defined inclusion/exclusion criteria will apply