The purpose of this study is to determine the safety and efficacy of an oral Farnesyl Protein Transferase Inhibitor (Lonafarnib/SCH 6636) as a single agent in Adult Patients With Squamous Cell Carcinoma of the Head \& Neck and will help determine if further development is justified.
Inclusion Criteria: * Histologically or cytologically proven squamous cell carcinoma of the head \& neck. * Age greater than or equal to 18. * ECOG performance status of 0 to 1 * Measurable malignant disease. * Patients that have failed at least one platinum-containing regimen and have received no more than three prior regimens and do not have other curative treatment options. * Patients must be at least 2 wks post surgery or radiation therapy * Patients must be at least 4 weeks post chemotherapy * Meets protocol requirements for specified laboratory values. * Written informed consent and cooperation of patient. * Appropriate use of effective contraception if of childbearing potential. * No investigational drugs of any type within 30 days prior to administration. Exclusion Criteria: * Prior exposure to farnesyl transferase inhibitors * Medical conditions that would interfere with taking oral medications. * Patients with significant QTc prolongation at baseline (\>500 msec.) * Pregnant or nursing women * Known HIV positivity or AIDS-related illness. * Concomitant chemotherapy, hormonal therapy, radiotherapy or immunotherapy * Patients with any signs of involvement of the dura, meninges, or brain. * Patients with squamous cell carcinoma of the nasopharynx * Patients who currently have other cancers or have been treated in the last 5 years for any other malignancy.