The biological screening of the chemical library of our Organic Chemistry Department, carried out on an automated fluorescence-based FTase assay, allowed us to discover that a phenothiazine derivative (1d) was an inhibitor of farnesyltransferase. Three new series of human farnesyltransferase inhibitors, based on a phenothiazine scaffold, were synthesized with protein farnesyltransferase inhibition potencies in the low micromolar range. Ester ...