A pyrimidone derivative having tau protein kinase 1 inhibitory activity which is represented by formula (I) or a salt thereof, or a solvate thereof or a hydrate thereof: wherein Q represents CH or nitrogen atom； R represents a C1-C12 alkyl group； the ring of: represents piperazine ring or piperidine ring； each X independently represents a C1-C8 alkyl group, an optionally partially hydrogenated C6-C10 aryl ring, an indan ring or the like； m represents an integer of 1 to 3； each Y independently represents a halogen atom, a hydroxy group, a cyano group, a C1-C6 alkyl group or the like； n represents an integer of 0 to 8； when X and Y or two Y groups are attached on the same carbon atom, they may combine to each other to form a C2-C6 alkylene group.一種具有τ蛋白質激酶1抑制活性而由通式(I)表示之嘧啶酮衍生物或其鹽、或其溶劑合物或其水合物：其中Q係表示CH或氮原子；R係表示C1-C12烷基；下式之環：係表示哌環或哌啶環；各X係個別表示C1-C8烷基、視情況部分氫化之C6-C10芳基、氫茚環或其類者；m係表示1至3之整數；各個Y係個別表示鹵原子、羥基、氰基、C1-C6烷基或其類者；n係表示0至8之整數；當X與Y或兩Y基團係連接於相同碳原子上時，其可彼此結合形成C2-C6伸烷基。
