Rationale and design of a randomized clinical study to investigate the effect of ezetimibe, a cholesterol absorption inhibitor, on the regression of intracoronary plaque evaluated by non-obstructive angioscopy and ultrasound: The ZIPANGU study

Background and purposeIt is well recognized that low-density lipoprotein cholesterol (LDL-C)-lowering therapy is effective for primary and secondary prevention of cerebrovascular/cardiovascular disease. Ezetimibe, an inhibitor of the Niemann-Pick C1-Like 1 cholesterol transporter, is a relatively new drug for LDL-C-lowering therapy in addition to statins. However, comparison between an aggressive LDL-C-lowering therapy with a combination of statin and ezetimibe versus a standard LDL-C-lowering therapy with statin alone is still unclear in terms of their effects on stabilization and volume regression of coronary plaque. The ZIPANGU (Ezetimibe clinical investigation for the regression of intracoronary plaque evaluated by angioscopy and ultrasound) study is aimed at comparing these two types of therapy based on indices of plaque characteristics using non-obstructive coronary angioscopy and intravascular ultrasound.MethodsThe study is a multi-center, prospective, randomized, open-label, blinded-endpoint trial. Through a centralized enrollment method, patients will be allocated to either monotherapy with atorvastatin alone or to combination therapy with atorvastatin (maximum: 20 mg/day) and ezetimibe (10 mg/day). The target LDL-C level will be <100 mg/dL for the monotherapy group and <70 mg/dL for the combination therapy group. At the baseline and the follow-up period of 9 months, non-obstructive coronary angioscopy and intravascular ultrasound will be performed to compare the changes in plaque color and volume between the two groups.ConclusionsThe ZIPANGU study will clarify whether combination therapy with statins and ezetimibe is better for stabilizing coronary plaque as secondary prevention than monotherapy by statins alone. The study will give new insights into lipid-lowering guidelines in Japan.