An Exploratory Tumor Biopsy-driven Study to Understand the Relationship Between Biomarkers and Clinical Response in Patients With Head and Neck Cancer Receiving REGN2810 (Anti-PD-1)

Key Inclusion Criteria: 1. Histologically confirmed diagnosis of recurrent and/or metastatic SCCHN (squamous cell carcinoma of the head and neck) with no curative options with at least 1 lesion that is measurable by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria and accessible for biopsies. Primary tumor sites of oral cavity, oropharynx, larynx, or hypopharynx are included. 2. Have failed/are refractory to at least first line chemotherapy OR deemed unsuitable candidate for first line chemotherapy due to medical co-morbidities or patient preference 3. Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 or 1 4. Adequate hepatic function 5. Adequate renal function 6. Adequate bone marrow function 7. Provide signed informed consent 8. Willing and able to comply with clinic visits and study-related procedures Key Exclusion Criteria: 1. Ongoing or recent (within 5 years) evidence of significant autoimmune disease that required treatment with systemic immunosuppressive treatments, which may suggest risk for immune-related adverse event (irAEs) 2. Prior treatment with an agent that blocks the programmed death-1/programmed death-ligand 1 (PD-1/PD-L1) pathway 3. Prior treatment with other immune modulating anti-cancer agents 4. Untreated or active brain metastases or spinal cord compression 5. Immunosuppressive corticosteroid doses within 4 weeks prior to the first dose of REGN2810 6. Prior treatment with idelalisib Other protocol-defined inclusion/exclusion criteria will apply