A pyrimidone derivative represented by formula (I) or a salt thereof, or a solvate thereof or a hydrate thereof: Y represents two hydrogen atoms, a sulphur atom, an oxygen atom, an hydroxy group and a hydrogen atom, an hydroxy group and a C 1-2 alkyl group, an hydroxy group and a C 1-2 perhalogenated alkyl group； a halogen atom and a hydrogen atom or a -(CH2)p-；Z represents a bond, an oxygen atom, NH, a nitrogen atom substituted by a hydrogen atom or a C 1-3 alkyl group, a sulphur atom, a methylene group optionally substituted ； R1 represents a 2, 3 or 4-pyridine ring or a 2, 4 or 5-pyrimidine ring, the ring being optionally substituted； R2 represents a hydrogen atom, a C 1-6 alkyl group or a halogen atom； R3 represents a hydrogen atom； a phenyl or a naphthyl group, these groups being optionally substituted a 4-15 membered heterocyclic group optionally substituted a -C(O)O (C 1-6 -alkyl) group optionally substituted ； a -C(O)-phenyl group, a -C(O)O-phenyl group, or a - C(O)O-CH 2 -phenyl group,the benzene rings of the above-mentioned groups being optionally substituted ； a -C(O)-4-15 membered heterocyclic group optionally substituted； R4 represents a hydrogen atom, a halogen atom, a hydroxyl group, a C 1-6 alkyl group optionally substituted； n represents 0 to 3； m represents 0 to 3 ； p represents 2 to 7； in the form of a free base or of an addition salt with an acid. Use in therapeutic
