Inclusion Criteria: - Phase 2: Histologically confirmed diagnosis of unresectable or metastatic NSCLC with KRAS G12C mutation and any PD-L1 TPS - Phase 3: Histologically confirmed diagnosis of unresectable or metastatic squamous or nonsquamous NSCLC with KRAS G12C mutation and PD-L1 TPS >=50% - Phase 3: Presence of evaluable or measurable disease per RECIST - Phase 3: CNS Inclusion - Based on screening brain imaging, patients must have one of the following: 1. No evidence of brain metastases 2. Untreated brain metastases not needing immediate local therapy 3. Previously treated brain metastases not needing immediate local therapy Exclusion Criteria: - Phase 2 and Phase 3: Prior systemic treatment for locally advanced or metastatic NSCLC including chemotherapy, immune checkpoint inhibitor therapy, or a therapy targeting KRAS G12C mutation (e.g., AMG 510). - Phase 2: Active brain metastases - Phase 3: Patients with known central nervous system (CNS) lesions must not have any of the following: 1. Any untreated brain lesions > 1.0 cm in size 2. Any brainstem lesions 3. Ongoing use of systemic corticosteroids for control of symptoms of brain lesions at a total daily dose of > 10 mg of prednisone (or equivalent) prior to randomization. 4. Have poorly controlled (> 1/week) generalized or complex partial seizures, or manifest neurologic progression due to brain lesions notwithstanding CNS-directed therapy - Phase 3: Radiation to the lung > 30 Gy within 6 months prior to the first dose of study treatment