Evaluation of ABEMACICLIB Monotherapy in Patients With Locally Advanced/Metastatic Head and Neck Cancer After Failure of Platinum and Cetuximab or Anti-EGFR-based Therapy and Harboring an Homozygous Deletion of CDKN2A, and/or an Amplification of CCND1 and/or of CDK6

"400mg/day with 2 doses of 200mg 12-hour apart For each 28-day cycle, a total of 56 doses of study drug will be dispensed.~Route of administration : oral~Duration of treatment until the patient experiences an unacceptable toxicity or symptomatic deterioration attributed to disease progression as determined by the investigator after an integrated assessment of radiographic data and clinical status or withdrawal of consent."