Inclusion Criteria:

          -  Measurable disease based on RECIST v1.1.

          -  Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

          -  Adequate organ function per protocol-defined criteria.

          -  Documentation of results from testing of human papilloma virus (HPV) status for
             oropharyngeal cancer.

          -  Baseline archival tumor specimen available or willing to undergo a prestudy treatment
             tumor core or excisional biopsy of a tumor lesion not previously irradiated, to obtain
             the specimen.

        Exclusion Criteria:

          -  Carcinoma of the nasopharynx, salivary gland, unknown primary origin, or nonsquamous
             histologies as primary tumors.

          -  Disease progression within 6 months of completion of curatively intended systemic
             treatment for locoregionally advanced HNSCC.

          -  Use of protocol-defined prior/concomitant therapy.

          -  Known additional malignancy that is progressing or has required active treatment
             within the past 3 years.

          -  Known active central nervous system (CNS) metastases and/or carcinomatous meningitis.

          -  Active autoimmune disease that has required systemic treatment in past 2 years.

          -  Known history of human immunodeficiency virus (HIV) infection. HIV testing is not
             required unless mandated by local health authority.

          -  Known history of or is positive for active hepatitis B (defined as hepatitis B surface
             antigen [HBsAg] reactive) or hepatitis C (defined as HCV RNA [qualitative] is
             detected).