Inclusion Criteria:

        Patients must meet all of the inclusion criteria to participate in this study.

          1. Ability to understand and the willingness to sign a written informed consent.

          2. Histologically or cytologically proven squamous cell carcinoma of the head and neck
             (lip, oral cavity, oropharynx, larynx, hypopharynx, non-EBV related nasopharynx,
             sinonasal, cutaneous), not amenable to curative intent therapy.

          3. Platinum-refractory disease, or ineligible/unfit for platinum-based therapy

          4. Patients must have at least one measurable site of disease as defined by RECIST v.1.1,
             determined by investigator review

          5. Age ≥ 18 years.

          6. Eastern Cooperative Oncology Group (ECOG) Performance status 0 or 1.

          7. Patient has adequate hematologic, hepatic and renal function

          8. Female patient of childbearing potential has a negative serum or urine pregnancy
             within 72 hours prior to receiving the first dose of study medication.

          9. Female patient of childbearing potential agrees to use 2 methods of birth control or
             be surgically sterile, or abstain from heterosexual activity for the course of the
             study through 120 days after the last dose of study medication.

         10. Male patient with a partner of childbearing potential agrees to use an adequate method
             of contraception starting with the first dose of study therapy through 120 days after
             the last dose of study therapy.

        Additional Inclusion Criterion for Cohort 1 (PD-1/PD-L1 Inhibitor-naïve, Cetuximab-naïve)
        and Cohort 2 (PD-1/PD-L1 Inhibitor-refractory, Cetuximab-naïve):

        1. Cetuximab-naïve patients may not have received cetuximab therapy in the
        recurrent/metastatic setting (treatment in curative setting permitted)

        Additional Inclusion Criterion for Cohorts 2 and 3 (PD-1/PD-L1 Inhibitor-refractory):

        1. PD-1/PD-L1 inhibitor-refractory patients must have documented disease progression after
        prior response to anti-PD-1/PD-L1 therapy (response defined as stable disease, partial or
        complete response)

        Additional Inclusion Criterion for Cohort 4 (Cutaneous HNSCC):

        1. Cutaneous HNSCC must not be amenable to local treatment modalities, including surgery
        and/or radiation.

        Exclusion Criteria:

        Patients meeting any of the exclusion criteria at baseline will be excluded from study
        participation.

          1. Patient has salivary gland primary.

          2. Patient is currently receiving or has received another investigational agent within 4
             weeks prior to Day 1 of study.

          3. Patient has received chemotherapy or radiotherapy within 4 weeks prior to Day 1 of
             study. Prior palliative radiotherapy to metastatic lesion(s) is permitted, provided
             there is at least one measurable lesion that has not been radiated.

          4. Patient has received a prior anti-cancer monoclonal antibody (mAb) within 4 weeks
             prior to study Day 1 or who has not recovered (i.e., ≤ Grade 1 or baseline) from
             adverse events due to a previously administered agents.

          5. Patient has had major surgery or insufficient recovery from surgical-related trauma or
             wound healing within 14 days of Study Day 1.

          6. Patient has had a prior Grade ≥ 3 immune-related adverse event (irAE) while receiving
             any previous immunotherapy agent, or any unresolved irAE > Grade 1.

          7. Patient has had prior Grade 4 infusion reaction to cetuximab.

          8. Patient has a known additional malignancy that is progressing or requires active
             treatment. Exceptions include basal cell carcinoma of the skin or squamous cell
             carcinoma of the skin that has undergone potentially curative therapy or in situ
             cervical cancer.

          9. Patient has known active central nervous system (CNS) metastases and/or carcinomatous
             meningitis.

             Note: Patients with previously treated brain metastases may participate provided they
             are stable (without evidence of progression by imaging for at least four weeks prior
             to the first dose of trial treatment and any neurologic symptoms have returned to
             baseline), have no evidence of new or enlarging brain metastases, and are not using
             steroids for at least 7 days prior to trial treatment. This exception does not include
             carcinomatous meningitis which is excluded regardless of clinical stability.

         10. Patient has an active autoimmune disease that has required systemic treatment in the
             past 2 years (i.e. with use of disease modifying agents, corticosteroids or
             immunosuppressive drugs).

             Notes:

               -  Patients with vitiligo, Grave's disease, or psoriasis not requiring systemic
                  treatment within the past 2 years are not excluded.

               -  Replacement therapy (e.g., thyroxine, insulin, or physiologic corticosteroid
                  replacement therapy for adrenal or pituitary insufficiency, etc.) is not
                  considered a form of systemic treatment.

         11. Patient has a diagnosis of immunodeficiency or is receiving systemic steroid therapy
             (>10mg prednisone daily, or steroid equivalent) or any other form of immunosuppressive
             therapy within 7 days prior to the first dose of pembrolizumab.

         12. Patient has a known history of active TB (Baccillus Tuberculosis).

         13. Patient has a known history of, or any evidence of active, non-infectious pneumonitis.

         14. Patient has a known history of chronic interstitial lung disease.

         15. Patient has an active infection requiring systemic therapy.

         16. Patient has a history or current evidence of any condition, therapy, or laboratory
             abnormality that might confound the results of the trial, interfere with the subject's
             participation for the full duration of the trial, or is not in the best interest of
             the subject to participate, in the opinion of the treating investigator.

         17. Patient has a known psychiatric or substance abuse disorders that would interfere with
             cooperation with the requirements of the trial.

         18. Patient is pregnant or breastfeeding, or expecting to conceive or father children
             within the projected duration of the trial.

         19. Patient has known active Hepatitis B infection (defined as presence of HepB sAg and/
             or Hep B DNA), active hepatitis C infection (defined as presence of Hep C RNA) and/or
             known Human Immunodeficiency Virus (HIV) carrier (HIV 1/2 antibodies).

         20. Patient has received a live vaccine within 30 days of study Day 1.

        Note: Seasonal influenza vaccines for injection are generally inactivated flu vaccines and
        are allowed; however intranasal influenza vaccines (e.g., Flu-Mist®) are live attenuated
        vaccines, and are not allowed.

        Additional Exclusion Criterion for Cohorts 1 (PD-1/PD-L1 inhibitor-naïve, cetuximab-naïve)
        and 4 (cutaneous):

        1. Patient has received any prior immunotherapy with inhibitors of PD-1 or PD-L1.