An inhibitor of HMG-CoA reductase (Ki = 1.3 nM); inhibits cholesterol synthesis in and growth of human arterial myocytes (IC50s = 0.4 and 4.6 nM, respectively); inhibits cholesterol biosynthesis in rats and dogs (ED50 = 0.002 mg/kg for both); reduces serum levels of cholesterol, triglycerides, and LDL in dogs in a dose-dependent manner; decreases cholesterol ester accumulation in arterial tissue of rabbits fed a 0.2% cholesterol diet (0.1 mg/kg); stabilizes plaques and delays progression into atherosclerotic disease in LDL-receptor deficient rabbits with hypercholesterolemia,,