Amidine compound or salt thereof

A compound represented by a formula (I):

• (wherein
• A1 represents a nitrogen atom or a group represented by a formula CR6, where R6 represents a hydrogen atom, a halogen atom, a cyano group or a group represented by a formula COR7, where R7 represents a hydroxy group, a C1-6 alkoxy group, a C1-6 alkyl group, an aryl group or a group represented by a formula NR8R9, where
• R8 and R9 are the same or different and represent a hydrogen atom or a C1-6 alkyl group, or
• R8 and R9 represent, together with the nitrogen atom bonded thereto, a saturated heterocyclic ring which may be substituted with oxo group;
• A2 and A3 are the same or different and represent a nitrogen atom or a group represented by a formula CH;
• R1 represents a C3-6 cycloalkyl group which may be substituted with 1 to 5 substituents selected from Substituent Group 1, a C1-6 alkyl group which may be substituted with 1 to 6 substituents selected from Substituent Group 1, an aryl group which may be substituted with 1 to 5 substituents selected from Substituent Group 2, a heterocyclic group which may be substituted with 1 to 5 substituents selected from Substituent Group 2, a group represented by a formula OR10, a group represented by a formula COR11, a group represented by a formula NR12CO2R13, a group represented by a formula NR14CONR15R16, a group represented by a formula NR17COR18, a group represented by a formula NR19SO2R20 or a group represented by a formula OCONR21R22, where
• R10, R13, R15, R16, R21 and R22 are the same or different and represent a hydrogen atom, a C1-6 alkyl group which may be substituted with 1 to 6 substituents selected from Substituent Group 1, a C3-6 cycloalkyl group which may be substituted with 1 to 5 substituents selected from Substituent Group 1, an adamantyl group, an aryl group which may be substituted with 1 to 5 substituents selected from Substituent Group 2 or a heterocyclic group which may be substituted with 1 to 5 substituents selected from Substituent Group 2,
• R11 represents a hydroxy group, a C1-6 alkoxy group, a C1-6 alkyl group which may be substituted with 1 to 6 substituents selected from Substituent Group 1, a C3-6 cycloalkyl group which may be substituted with 1 to 5 substituents selected from Substituent Group 1, an adamantyl group, an aryl group which may be substituted with 1 to 5 substituents selected from Substituent Group 2, a heterocyclic group which may be substituted with 1 to 5 substituents selected from Substituent Group 2 or a group represented by a formula NR23R24, where
• R23 and R24 are the same or different and represent a hydrogen atom, a C1-6 alkyl group which may be substituted with 1 to 6 substituents selected from Substituent Group 1 or a C3-6 cycloalkyl group which may be substituted with 1 to 5 substituents selected from Substituent Group 1,
• R12, R14, R17 and R19 are the same or different and represent a hydrogen atom or a C1-6 alkyl group,
• R18 and R20 are the same or different and represent a C1-6 alkyl group which may be substituted with 1 to 6 substituents selected from Substituent Group 1, a C3-6 cycloalkyl group which may be substituted with 1 to 5 substituents selected from Substituent Group 1, an adamantyl group, an aryl group which may be substituted with 1 to 5 substituents selected from Substituent Group 2 or a heterocyclic group which may be substituted with 1 to 5 substituents selected from Substituent Group 2,
• Substituent Group 1 is the group consisting of a halogen atom, an aryl group which may be substituted with 1 to 5 substituents selected from Substituent Group 2, a heterocyclic group which may be substituted with 1 to 5 substituents selected from Substituent Group 2, a group represented by a formula —OR25, a group represented by a formula —COR26, a group represented by a formula —NR27R28 and a group represented by a formula —SO2R29, where
• R25 represents a hydrogen atom, a C1-6 alkyl group, an aryl group which may be substituted with 1 to 5 substituents selected from Substituent Group 2 or a C1-6 alkanoyl group,
• R26 represents a hydroxy group, a C1-6 alkoxy group or a group represented by a formula NR30R31, where
• R30 and R31 are the same or different and represent a hydrogen atom or a C1-6 alkyl group, or
• R30 and R31 represent, together with the nitrogen atom bonded thereto, a saturated heterocyclic ring which may be substituted with oxo group,
• R27 and R28 are the same or different and represent a hydrogen atom or a C1-6 alkyl group,
• R29 represents a C1-6 alkyl group, a C3-6 cycloalkyl group, an aryl group which may be substituted with 1 to 5 substituents selected from Substituent Group 2 or a heterocyclic group which may be substituted with 1 to 5 substituents selected from Substituent Group 2,
• Substituent Group 2 is the group consisting of a halogen atom, an oxo group, a hydroxy group, a C1-6 alkoxy group, a C1-6 alkyl group, a C1-6 haloalkyl group, a cyano group, a C1-6 alkylsulfanyl group, a C1-6 alkylsulfinyl group, a C1-6 alkylsulfonyl group, an aminosulfonyl group, a C1-6 alkylaminosulfonyl group and a group represented by a formula COR32, where
• R32 represents a hydroxy group, a C1-6 alkoxy group or a group represented by a formula NR33R34, where
• R33 and R34 are the same or different and represent a hydrogen atom or a C1-6 alkyl group, or
• R33 and R34 represent, together with the nitrogen atom bonded thereto, a saturated heterocyclic ring which may be substituted with oxo group;
• R2 and R3 are the same or different and represent a hydrogen atom, a halogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group or a C1-6 alkoxy group;
• R4 and R5 are the same or different and represent a hydrogen atom, a C1-6 haloalkyl group or a C1-6 alkyl group, wherein the C1-6 alkyl group may be substituted with 1 to 3 substituents selected from the group consisting of a hydroxy group and a group represented by a formula COR35, where
• R35 represents a hydroxy group, a C1-6 alkoxy group or a group represented by a formula NR36R37, where
• R36 and R37 are the same or different and represent a hydrogen atom or a C1-6 alkyl group, or
• R36 and R37 represent, together with the nitrogen atom bonded thereto, a saturated heterocyclic ring which may be substituted with oxo group, or
• R4 and R5 represent, together with the nitrogen atom bonded thereto, a saturated heterocyclic ring which may be substituted with oxo group)
• or a salt thereof.