A compound represented by the formula (I) or a pharmaceutically acceptable salt thereof: ** Formula ** wherein R 1 represents halogenated C 1-6 alkyl or halogenated C 3-8 cycloalkyl； R2 represents a substituent selected from a group consisting of the following groups: ** Formula ** in which W represents C1-6 alkylene, C2-6 alkenylene, C2-6 alkynylene or C3-6 cycloalkylene, wherein the alkylene, alkenylene, alkynylene or cycloalkylene may be substituted with optionally halogenated C1-3 alkyl, optionally halogenated C1-3 alkyloxy, hydroxy or halogen； R represents C1-6 alkyl C3-8 cycloalkyl, aryl or heteroaryl, wherein C1-6 alkyl C3-8 cycloalkyl, aryl or heteroaryl can be substituted with halogen, optionally halogenated C1-6 alkyl, optionally halogenated C1-6 alkyloxy, C 1-6 alkylsulfonyl, cyano, phenyl, C 1-6 alkylthio, hydroxyl, amino, C 1-6 alkylamino, C 1-6 alkylamino, C 1-6 hydroxy-alkyl, C 1-6 alkyl-alkylamino, C 1-6 -alkylamino -6, di- C 1-6 alkylaminoalkyl, C 1-6 alkoxy-C 1-6 alkyl, C 1-6 alkylcarbonyl, C 1-6 alkylcarbonylamino, C 1-6 alkylcarbamoyl, C 3-8 cycloalkylcarbamoyl, or C 1-6 alkylsulfonylamino or C 1-6 alkylaminosulfonyl； R3 represents a hydrogen atom, C1-6 alkyl, aryl or heteroaryl； X represents -O-, -C (R4a) (R4b) - or -NR5-； R4a, R4b and R5 each independently represent hydrogen, C1-6 alkyl, C3-8 cycloalkyl, aryl or heteroaryl, wherein C1-6 alkyl, C3-8 cycloalkyl, aryl or heteroaryl can be substituted with halogen, C1- alkyl 6 optionally halogenated, C1-6 alkyloxy optionally halogenated, C1-6 alkylsulfonyl, cyano, aryl or heteroaryl； Y1 represents -CR6 - or -N-； Y2 represents -CR7 - or -N-； Y3 represents -CR8 - or -N-； Y4 represents -CR9 - or -N-； R6, R7, R8 and R9 each independently represent a hydrogen atom, halogen, cyano, C1-6 alkyl C3-8 cycloalkyl, C1-6 alkoxy, hydroxyl, hydroxy-C1-6 alkyl, amino, C1-6 alkylamino, di- C1-6 alkylamino, C1-6 amino alkyl, C1-6 alkylamino-C1-6 alkyl, di- C1-6 alkylamino-C1-6 alkyl, C1-6 alkoxy-C1-6 alkyl, heterocy
