Inclusion Criteria:

          -  Recurrent/metastatic (R/M) SCCHN of the oral cavity, oropharynx, larynx and
             hypopharynx

          -  No prior systemic therapy for treatment of R/M disease

          -  Patients with squamous cell carcinoma of an unknown primary are eligible provided
             their tumor tested positive for p-16 and they have previously received treatment for
             locoregional head and neck cancer

          -  Must be at least four weeks since prior systemic therapy, radiation and/or surgery

          -  At least one measurable lesion as defined by Response Evaluation Criteria In Solid
             Tumors (RECIST) v1.1 on screening computed tomography (CT) or magnetic resonance
             imaging (MRI)

          -  18 years of age and older

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

          -  White blood cell (WBC) count > 2,500 cells/uL

          -  Absolute neutrophil count (ANC) >1,500 cells/uL

          -  Platelet count >= 100,000 cells/uL

          -  Hemoglobin >= 9 g/dL

          -  Creatinine =< 1.6 mg/dL

          -  Total bilirubin =< 1.6 mg/dL

          -  Serum glutamic oxaloacetic transaminase (SGOT) (aspartate transaminase [AST]), serum
             glutamic-pyruvic transaminase (SGPT) (alanine aminotransferase [ALT]) =< 2.5 x upper
             limit of normal (ULN)

          -  Potassium >= lower limit of normal (LLN)

          -  Willingness to use medically acceptable contraception throughout the study period and
             four weeks after the final administration of treatment

          -  For female subjects with reproductive potential: a negative serum pregnancy test at
             baseline

          -  Ability and willingness to provide written informed consent and to comply with the
             study visits and assessment schedule

        Exclusion Criteria:

          -  Disease which is amenable to curative local therapy

          -  Nasopharyngeal, salivary gland, lip, or sinonasal carcinoma

          -  Disease that requires corticosteroids (>10 mg prednisone or equivalent daily within
             four weeks prior to the first dose of cemiplimab) or other immune suppressives at
             baseline

          -  Previous treatment with mAb-based immune therapies

          -  Previous treatment with PI3K inhibitors

          -  Known brain metastases, unless stable for at least 21 days prior to registration

          -  Known infection human immunodeficiency virus (HIV), hepatitis B or C

          -  Clinically significant cardiac disease (e.g., congestive heart failure, unstable or
             uncontrolled angina, myocardial infarction) within the past six months

          -  History of pneumonitis within the past five years

          -  Recipient of live vaccines (including attenuated) within 30 days of study treatment

          -  Female patients who are pregnant or breast-feeding

          -  Any other condition or circumstance that could interfere with adherence to the study's
             procedures or requirements or otherwise compromise the study's objectives in the
             opinion of the Principal Investigator