The invention relates to use of substituted-pyrimidone derivatives represented by formula (I) or a salt thereof:wherein X, Y, R1, R2, R3, R4, R5, n, p and q are as defined herein. More specifically, the invention relates to a medicament comprising the said derivative or a salt thereof as an active ingredient which is used for preventive and/or therapeutic treatment of a disease caused by abnormal activity of GSK3β, such as Pick's disease among various other diseases as claimed herein.
