Farnesyl transferase inhibitors in clinical development

Farnesyl transferase (FT) inhibitors block the main post-translational modification of the Ras protein, thus interfering with its localisation to the inner surface of the plasma membrane and subsequent activation of downstream effectors. Although initially developed as a strategy to target Ras in cancer, FT inhibitors have subsequently been acknowledged as acting by additional and more complex mechanisms that may extend beyond Ras, involving RhoB, centromere-binding proteins and probably other farnesylated proteins. SCH66336 (lonafarnib, Sarasar™, Schering-Plough), a tricyclic orally active FT inhibitor, was the first of these compounds to undergo clinical development. Gastrointestinal tract toxicities and fatigue have qualified as dose-limiting toxicities in all Phase I/II studies. Evidence of clinical activity has been reported. Lonafarnib combination studies with both gemcitabine and paclitaxel have been carried out. No unexpected toxicities were observed in these Phase I studies, while encouraging cli...