A Study of Raludotatug Deruxtecan (R-DXd) in People With Gastrointestinal Cancers (MK-5909-005)

Inclusion Criteria: 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) Exclusion Criteria: 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