Hypolipidemic effects of NB-598 in dogs.

NB-598, a new inhibitor of mammalian squalene epoxidase, was found to be a potent inhibitor of microsomal squalene epoxidase from dog liver. Hypolipidemic effects of NB-598 were compared with those of simvastatin (MK-733, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor) in dogs. NB-598 was found to decrease serum total cholesterol levels and increase serum squalene levels in a dose-dependent manner. MK-733 decreased serum total cholesterol and squalene levels. Both NB-598 and MK-733 decreased all classes of lipoprotein cholesterol, and they decreased low density lipoprotein cholesterol most potently. Both drugs decreased phospholipid levels in parallel with cholesterol levels. NB-598 also decreased triacylglycerol levels. After termination of drug administration, these levels returned to the control levels. The potency of NB-598 is thought to be as great or greater than that of MK-733. Moreover, NB-598 increased squalene concentrations in the feces and gallbladder bile, but it did not affect neutral sterol and bile acid concentrations. NB-598 did not affect the lithogenic index.