Study of REGN4659 in Combination With Cemiplimab in Patients With Advanced or Metastatic Non-Small Cell Lung Cancer (NSCLC)

KEY Inclusion Criteria: 1. Patients with histologically or cytologically documented squamous or non-squamous NSCLC with unresectable stage IIIB or stage IV disease 2. Combination dose escalation cohorts: Treatment-experienced patients who have received no more than 3 lines of systemic therapy including no more than 2 lines of cytotoxic chemotherapy, and for whom no available therapy has a high probability to convey clinical benefit. 3. Dose escalation cohort C: Anti-PD-1/PD-L1 naïve patients who have received 1 to 2 prior lines of cytotoxic chemotherapy including a platinum doublet-containing regimen 4. Expansion cohort(s): Anti-PD-1/PD-L1 experienced patients who have progressed while receiving therapy or within 6 months of stopping therapy for stage III or IV disease. Patients must not have permanently discontinued anti-PD-1/PD-L1 therapy due to treatment related AE. Patients must have received one line of anti-PD--1/PD-L1 immunotherapy. Patients may also have received one line of chemotherapy KEY Exclusion Criteria: 1. Expansion cohort(s) only: Patients who have never smoked, defined as smoking ≤100 cigarettes in a lifetime 2. Active or untreated brain metastases or spinal cord compression. Patients are eligible if central nervous system (CNS) metastases are adequately treated and patients have neurologically returned to baseline (except for residual signs or symptoms related to the CNS treatment) for at least 2 weeks prior to enrollment. Patients must be off (immunosuppressive doses of) corticosteroid therapy 3. Expansion cohort(s) only: Patients with tumors tested positive for epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK) gene mutations or ROS1 fusions. 4. Radiation therapy within 2 weeks prior to enrollment and not recovered to baseline from any AE due to radiation 5. Patients who received prior treatment with an anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibody 6. Previous treatment with idelalisib (ZYDELIG®) at any time Note: Other protocol defined inclusion/ exclusion criteria apply