The purpose of the present invention is to provide a therapeutic agent or preventive agent for exacerbation of influenza, specifically to provide a novel pyruvate dehydrogenase kinase 4 (PDK4) inhibitor. The present invention relates to a PDK4 inhibitor, medical composition or cosmetic composition containing as the active ingredient a compound represented by any one of the following general formulas (I) through (III) and a pharmacologically acceptable ester derivative thereof, or a pharmacologically acceptable salt of the same.
