AMG 436 as Monotherapy and Combination Therapy in Participants With MSI-H/dMMR Solid Tumors

Inclusion Criteria: * Age ≥ 18 years (or ≥ legal age within the country if it is older than 18 years). * Histologically confirmed MSI-H or dMMR metastatic or locally advanced solid tumor by local testing or central testing. * Tumor tissue (formalin-fixed, paraffin-embedded sample) archival block must be available. Participants without archived tumor tissue may enroll by undergoing tumor biopsy before dosing. * Disease measurable as defined by Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1). * Eastern Cooperative Oncology Group performance (ECOG) 0-1. * Adequate organ function as defined in the protocol. Exclusion Criteria: * Participants with primary central nervous system (CNS) tumors. * Impaired cardiac function or clinically significant cardiac disease. * Major surgery within 28 days of trial day 1. * Antitumor therapy (chemotherapy, antibody therapy, molecular targeted therapy, hormonal therapy, or investigational agent) within 21 days of first dose of trial treatment, unless anti-tumor therapy is a therapy with 5 times the half-life being shorter than 21 days (in this case, enrollment may be allowed with washout from prior therapy of \< 21 days. * Radiation therapy within 28 days of the first dose of trial treatment (or local or focal radiotherapy with palliative intent within 14 days of the first dose). * Gastrointestinal tract disease causing the inability to take per os (PO) medication, malabsorption syndrome, requirement for intravenous (IV) alimentation, uncontrolled inflammatory gastrointestinal disease (eg, Crohn's disease, ulcerative colitis).