There is to provide is an agent for reduction of a lipid rich plaque, stabilization of a lipid rich plaque and/or prevention of rupture of a lipid rich plaque in an atherosclerotic lesion comprising an effective amount of 2-[4-[2-(benzimidazole-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamide (hereinafter, referred to as compound 1), its pharmaceutically acceptable salt or a hydrate thereof and Pitavastatin, and a pharmaceutically acceptable carrier, wherein the agent is intended to be simultaneously administered, or separately administered with interval of time to a patient in need thereof. There is also to provide a method for reduction of a lipid rich plaque, stabilization of a lipid rich plaque and/or prevention of rupture of a lipid rich plaque in an atherosclerotic lesion, comprising simultaneously administering, or separately administering with interval of time an effective amount of the compound 1, its pharmaceutically acceptable salt or a hydrate thereof and an effective amount of Pitavastatin to a patient in need thereof.