['squamous cell carcinoma of the head and neck (scchn)']
['palbociclib', 'cetuximab', 'placebo']

        Key Inclusion Criteria:

          -  Histologically or cytologically confirmed squamous cell carcinoma of the oral cavity,
             oropharynx, hypopharynx or larynx, not amenable for salvage surgery or radiotherapy.

          -  Measurable disease as defined per RECIST v. 1.1. Tumor lesions previously irradiated
             or subjected to other locoregional therapy will only be deemed measureable if disease
             progression at the treated site after completion of therapy is clearly documented.

          -  HPV- negative SCCHN tumor as determined per institutional standard (eg, p16 IHC;
             multiplex nucleic acid sequence based amplification [NASBA] or other polymerase chain
             reaction [PCR]-based assays).

          -  Documented progressive disease according to RECIST v1.1 (Appendix 2) following receipt
             of at least 2 cycles of one platinum-containing chemotherapy regimen administered for
             R/M disease (min. 50 mg/m2 for cisplatin, minimum area under the curve [AUC] > 4 for
             carboplatin).

          -  Availability of a tumor tissue specimen (ie, archived formalin fixed paraffin embedded
             tissue [block preferred, or 15 unstained slides]), which will be used for centralized,
             retrospective biomarker analysis. If archived tumor tissue is not available, then a de
             novo biopsy will be required for patient participation.

        Key Exclusion Criteria:

          -  Prior nasopharyngeal cancer, salivary gland or sinus tumors.

          -  More than one chemotherapeutic regimen given for R/M disease. Prior treatment with
             immunotherapy is allowed.

          -  Known active uncontrolled or symptomatic central nervous system (CNS) metastases,
             carcinomatous meningitis, or leptomeningeal disease as indicated by clinical symptoms,
             cerebral edema, and/or progressive growth. Patients with a history of CNS metastases
             or cord compression are eligible if they have been definitively treated with local
             therapy (eg, radiotherapy, stereotactic surgery) and are clinically stable off
             anticonvulsants and steroids for at least 4 weeks before randomization.

          -  Progressive disease within 3 months after completion of curatively intended treatment
             for locoregionally advanced SCCHN.

          -  Difficulty swallowing capsules.

          -  Prior use of cetuximab in the R/M disease treatment setting (except cetuximab during
             curative radiotherapy)
      