Abstract: The invention relates to a pyrimidone derivative represented by formula (I) or a salt thereof: wherein: X represents hydrogen atoms, a sulphur atom, an oxygen atom or a C1-2 alkyl group and a hydrogen atom; Y represents a bond, an ethenylene group, an ethynylene group, a 1,2-cyclopropylene, an oxygen atom, a sulphur atom, a sulfonyl group, a sulfoxyde group, a carbonyl group, a nitrogen atom being optionally substituted; or a methylene group optionally substituted; R1 represents a 2, 3 or 4-pyridyl group optionally substituted by a C3-6 cycloalkyl group a C1-4 alkyl group, a C1-4 alkoxy group, a benzyl group or a halogen atom; when Y represents a bond, a methylene group optionally substituted or a carbonyl group then R2 represents a C1-6 alkyl group, a C3-6 cycloalkyl group, a C1-4 alkylthio group, a C1-4 alkoxy group, a C1-2 perhalogenated alkyl group, a C1-3 halogenated alkyl group, a 5,6,7,8-tetrahydronaphthyl ring, a naphthyl ring, a phenylthio group, a benzyl group, a phenyl ring, a pyridyl ring