Pyrimidone derivative or a salt thereof or a solvate or hydrate thereof represented by the formula (1).
(Wherein, Y is two hydrogen atoms, a sulfur atom, an oxygen atom or a C _1-2 alkyl group and a hydrogen atom, Z is a bond, is substituted with an oxygen atom, a hydrogen atom or a C _1-3 alkyl group nitrogen atom, a sulfur atom, optionally substituted methylene group, _{R 1} is 2,3,4-pyridine ring or a 2,4,5-pyridine ring (wherein the ring is optionally substituted. ) represents a, _{R 2} is a benzene ring or a naphthalene ring (which ring is optionally substituted.) represent, _{R 3} represents a hydrogen _{atom, C 1-6} alkyl group or a halogen atom, _{R 4} represents a hydrogen atom or a _{C 1-6} alkyl group, _{R 5} represents a _{C 1-6} alkyl group substituted hydrogen atom, optionally, _{R 6} is a hydrogen _{atom, C 1-6} alkyl group or a halogen represents an atom, _{R 7} represents a hydrogen atom or a _{C 1-6} alkyl group, n represents 3 0, m represents from 0 1, o denotes.) the present invention 0-2 is also used for prophylactic and / or therapeutic treatment of neurodegenerative diseases such as Alzheimer's disease caused by abnormal activity of GSK3?, pharmaceutical agents containing the derivative or its salt as an active ingredient.