A Safety and Antitumor Activity Trial of Immunoradiotherapy Combinations as a Treatment Option for Subjects With Metastatic Solid Tumors

Key Inclusion Criteria: * Participants with histologically confirmed non-central nervous system (CNS) solid tumor that is metastatic and for whom there is no available standard therapy. * At least 18 years of age. * Signed informed consent prior to any screening procedures. * Measurable disease according to RECIST v1.1. * Life expectancy of \>3 months. * Qualify for palliative radiotherapy as an available option for disease management. * Eastern Cooperative Oncology Group (ECOG) 0-1. * Normal or adequate liver, renal, cardiac and bone marrow function. Key Exclusion Criteria: * Prior malignancy except for non-melanoma skin cancers and in situ cancers. * Condition contraindicating radiotherapy. * Rapidly progressing disease. * Active, known or suspected autoimmune disease. * History of non-infectious pneumonitis that required steroids or currently has pneumonitis. * Contraindications to the use of pembrolizumab. * Condition requiring systemic treatment with either corticosteroids or other immunosuppressive medications within 14 days of first treatment. * Received an allogeneic tissue/solid organ transplant. * Active infection requiring systemic therapy. Note: Other protocol defined inclusion and exclusion criteria may apply.