For the purpose of providing a GSK-3β inhibitor containing a 2-aminopyridine compound or a salt thereof or a prodrug thereof useful as an agent for the prophylaxis or treatment of a GSK-3β-related pathology or disease, the present invention provides a GSK-3β inhibitor containing a compound represented by the formula (IA):
wherein each symbol is as defined in the specification.
or a salt thereof or a prodrug thereof.