This is a single arm phase II trial to study the efficacy and safety of a Cdk inhibitor P276-00 in the treatment of squamous cell carcinoma of head and neck. Patients with recurrent or metastatic disease that is unresectable and incurable by radiation will be enrolled. Thirty eight evaluable patients need to be enrolled in the study. All patients will receive protocol treatment i.e. P276-00 as an intravenous infusion from day 1 to day 5 and from day 8 to day 12 in each 21 day cycle till progression of disease or unacceptable toxicity. Safety evaluations by means of recording vitals, physical examination and lab investigations like hematology and clinical chemistry will be undertaken at regular intervals in each cycle. Tumor measurements by spiral CT scan will be undertaken at baseline and at the end of every 2 cycles for response evaluation by RECIST criteria. All patients will be followed up for survival status till one year of cycle 1 day 1.