Manumycin A is an antibiotic that acts as a potent and selective farnesyltransferase (FTase) inhibitor with anti-tumor activity.^1,2 It inhibits rat brain FTase with a Ki value of 1.2 µM, thereby preventing Ras activation which requires farnesylation at the C-terminus for membrane attachment.¹ It exhibits significant antitumor activity against Ki-ras-activated solid tumors in mice at a dose of 6.3 mg/kg.¹ Manymycin A inhibits IκB kinase (IKK), independent of FTase inhibition, in an number of cells types with effective concentrations of 2-10 µM.³ In ApoE-deficient mice, Manumycin A treatment for 22 weeks at 5 mg/kg reduced aortic fatty streak lesion size to 43% of vehicle-treated animals, indicating FTase inhibition as a potential target for prevention or treatment of atherosclerosis.⁴