The present invention to provide a novel pyruvate dehydrogenase kinase inhibitors. A pyruvate dehydrogenase kinase inhibitor comprising a compound represented by the general formula (I) as an active ingredient (wherein, ring A represents a 6-membered aromatic hydrocarbon ring optionally substituted with 2-4 substituents, R 1 and R 4 , which are the same or different, represent a hydrogen atom, a hydroxyl group, an optionally substituted C1-6 alkyl group, R 2 and R 3 , which are the same or different, represent a hydrogen atom, a carboxyl group, an optionally substituted C1-6 alkyl group, an optionally substituted C6-10 aryl group, or a group represented by -C (=R 9 )-R 10 ), a pharmaceutical composition for treatment or prophylaxis of diseases or disorders that pyruvate dehydrogenase kinase relates to its development or aggravation, and a cosmetic composition, and the like.
