KL 001 is a Cryptochrome protein (CRY) stabilizer. KL001 prevented ubiquitin-dependent degradation of CRY, resulting in lengthening of the circadian period. KL001-mediated CRY stabilization inhibited glucagon-induced gluconeogenesis in primary hepatocytes. KL001 thus provides a tool to study the regulation of CRY-dependent physiology and aid development of clock-based therapeutics of diabetes.