A Study to Evaluate Immunotherapy Combinations in Participants With Gastrointestinal Malignancies

In the dose escalation phase, escalating doses of etrumadenant in combination with mFOLFOX at standard doses will be assessed in participants with advanced metastatic GEC or CRC. Eligible participants will receive oral administration of etrumadenant as well as IV infusion of mFOLFOX. The recommended dose for expansion (RDE) of etrumadenant will be determined upon completion of the dose-escalation phase. In the dose expansion phase, etrumadenant at the RDE in combination with mFOLFOX at standard doses may be assessed in participants with advanced metastatic GEC or CRC. Overall duration of treatment will depend on how well the treatment is tolerated. Treatment may continue until unacceptable toxicity or progressive disease or other reasons specified in the protocol.