Purity >98% by HPLC. FTI-277 is a potent and selective farnesyltransferase (FTase) inhibitor (IC50 = 0.5 nM). It potently inhibits (IC50 = 100 nM) H-Ras, but not the geranylgeranylated Rap1A processing in whole cells. FTI-277 blocks constitutive activation of mitogen-activated protein kinase (MAPK) in H-RasF, but not H-RasGG, or Raf-transformed cells.