The main inclusion criteria include but are not limited to the following: - Has one of the following cancers: - Unresectable or metastatic pancreatic ductal adenocarcinoma (PDAC) - Unresectable or metastatic adenocarcinoma of the biliary tract [intra- or extrahepatic holangiocarcinoma (CCA) or gallbladder cancer (GBC)] - Unresectable or metastatic colorectal adenocarcinoma - Unresectable or metastatic gastric adenocarcinoma - Gastroesophageal junction adenocarcinoma (GEJAC) - Esophageal adenocarcinoma (EAC) - Has received prior therapy for the cancer - Has a life expectancy of at least 3 months - If human immunodeficiency virus (HIV) infected, must have well controlled HIV on antiretroviral therapy (ART)

The main exclusion criteria include but are not limited to the following: - Has a history of (noninfectious) interstitial lung disease (ILD)/pneumonitis that required steroids or has current ILD/pneumonitis, and/or suspected ILD/pneumonitis - Has clinically severe pulmonary compromise resulting from intercurrent pulmonary illnesses - Has uncontrolled or significant cardiovascular disease - Has a known additional malignancy that is progressing or has required active treatment within the past 3 years - Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis - Active autoimmune disease that has required systemic treatment in the past 2 years - Has not adequately recovered from major surgery or has ongoing surgical complications - HIV-infected participants with a history of Kaposi's sarcoma and/or Multicentric Castleman's Disease