Abstract: The present invention provides a compound having a PDHK inhibitory activity and useful for the treatment or prophylaxis of diabetes (type 1 diabetes, type 2 diabetes etc.), insulin resistance syndrome, metabolic syndrome, hyperglycemia, hyperlactacidemia, diabetic complications (diabetic neuropathy, diabetic retinopathy, diabetic nephropathy, cataract etc.), cardiac failure (acute cardiac failure, chronic cardiac failure), cardiomyopathy, myocardial ischemia, myocardial infarction, angina pectoris, dyslipidemia, atherosclerosis, peripheral artery disease, intermittent claudication, chronic obstructive pulmonary disease s, brain ischemia, cerebral apoplexy, mitochondrial disease, mitochondrial encephalomyopathy, cancer, pulmonary hypertension, Alzheimer disease, vascular dementia, glaucoma, diabetic retinopathy, retinopathy of prematurity, retinal vein occlusion, ischemic optic neuropathy or chronic kidney disease.