Main Inclusion Criteria:

          1. Age ≥ 18 years

          2. Histologically or cytologically-confirmed, HPV (+) or HPV (-) squamous cell carcinoma
             of the nasopharynx (WHO Type 1), oropharynx, hypopharynx, larynx (supraglottis,
             glottis, subglottis) or oral cavity.

          3. Recurrent or metastatic disease, documented by imaging (CT scan, MRI, X-ray) and/or
             physical examination with measurable disease as per Response Evaluation Criteria in
             Solid Tumors [RECIST] 1.1

        For phase II cohorts:

          -  Cohort #1: Patients who received a maximum of two prior systemic regimens for
             recurrent and/or metastatic disease and not amenable to further therapy with curative
             intent

          -  Cohort #2: Patients with R/M SCCHN not amenable to therapy of curative intent, who
             have received a maximum of two prior systemic regimens in the R/M setting and who have
             received prior PD-(L)1 blockers

          -  Cohort #3: Patients with R/M SCCHN who have not received prior systemic regimens in
             the R/M setting and who have not received prior PD-(L)1 inhibitors

        Main Exclusion Criteria:

          1. For phase II cohort #1 and cohort #2: Patients who received more than 2 prior systemic
             regimens for recurrent and/or metastatic disease (no restriction in the phase Ib part
             of the trial).

          2. For phase II cohort #1 and cohort #2: Patients who received cetuximab or another
             inhibitor of epidermal growth factor receptor are excluded from the phase II of the
             trial, except if cetuximab was given as part of a primary treatment approach, with no
             progressive disease for at least 4 months following the end of prior cetuximab
             treatment.