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

- 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.

- 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).