A Clinical Study of MK-2870 Alone or With Other Treatments to Treat Gastrointestinal Cancers (MK-9999-02A)

Inclusion Criteria: The main inclusion criteria include but are not limited to the following: * Has one of the following cancers: * Unresectable or metastatic colorectal cancer and has received prior therapy for the cancer * Advanced or metastatic pancreatic ductal adenocarcinoma (PDAC) and has received prior therapy for the cancer * Advanced and/or unresectable biliary tract cancer (BTC) and has received prior therapy for the cancer * Advanced and/or unresectable BTC and has not received prior therapy for the cancer * For participants who have received prior therapy for cancer: Has recovered from any side effects due to previous cancer treatment Exclusion Criteria: The main exclusion criteria include but are not limited to the following: * History of severe eye disease * For participants who have received prior therapy for cancer: Received prior systemic anticancer therapy including investigational agents within 4 weeks before starting study intervention * History of (noninfectious) pneumonitis/interstitial lung disease (ILD) that required steroids, has current pneumonitis/ILD, or has suspected ILD or pneumonitis that cannot be ruled out by standard diagnostic assessments at Screening