Pitavastatin achieves its potent pharmacologic action by strong binding to the active site of HMG-CoA reductase consists of hydrophilic areas and hydrophobic areas, and pitavastatin is thought to form 10 hydrogen bonds with hydrophilic amino groups in this active pocket. The cyclopropyl group is an important feature of the structure-activity relationship, and this group fits hydrophobic areas of HMG-CoA reductase, thus retaining preferable space and form, so that pitavastatin shows inhibitory action. It is reported that inhibitory activity of pitavastatin analog, which has an isoprppyl group instead of a cycloproply group, was only about a fifth of that of pitavastatin, so pitavastatin may be regarded as a compound that is designed to fit the enzyme structure