FIELD: chemistry.SUBSTANCE: invention relates to 1,2,4-triazolone derivatives and pharmaceutically acceptable salts thereof. The disclosed compounds have antagonistic activity with respect to the arginine vasopressin V1b receptor. In formula (IA): R1 is C1-5 alkyl (the C1-5 alkyl is optionally substituted with 1-3 groups selected from a group consisting of hydroxy, halogen atoms, and C3-7 cycloalkyl), C3-7 cycloalkyl or a 4-8-member saturated heterocycle, containing one heteroatom selected from an oxygen atom； R2 is a hydrogen atom； R3 is a phenyl or pyridyl (the phenyl or pyridyl is optionally substituted with 1 or 2 groups selected from a group consisting of C1-5 alkoxy, halogen atoms, cyano and C1-5 alkylsulphonyl)； R4 and R5 can be identical or different, and each is a hydrogen atom or C1-5 alkyl (the C1-5 alkyl is optionally substituted with one hydroxy), or R4 and R5 optionally, together with a nitrogen atom with which they are bonded, form a 4-8-member saturated or unsaturated heterocycle, optionally containing one nitrogen, oxygen or sulphur atom, in addition to the nitrogen atom with which they are bonded, in a ring (the 4-8-member saturated or unsaturated heterocycle is optionally substituted with one or two groups selected from a group consisting of hydroxy, C1-5 alkyl ( the C1-5 alkyl is optionally substituted with one hydroxy), C1-5 alkoxy, halogen atoms, cyano, C2-5 alkanoyl, aminocarbonyl, trifluoromethyl and amino (the amino is optionally substituted with one or two groups selected from a group consisting of C1-5 alkyl and C2-5 alkanoyl), and the 4-8-member saturated heterocycle optionally has a C1-5 alkylene group which crosslinks two different carbon atoms in the ring, or form 2-oxa-6-azaspiro[3.3]hept-6-yl or 7-oxa-2-azaspiro[3.5]non-2-yl； A is phenylene, pyridinediyl or pyrimidinediyl (the phenylene, pyridinediyl and pyrimidinediyl are optionally substituted with one group selected from halogen atoms and C1-5 alkoxy)； X is a single bond or -O-；
