A compound represented by the following formula wherein R1, R2, R3 and R4 may be the same or different and are each independently a hydrogen atom, a nitro group, a halogeno group, a cyano group, a hydroxyl group, a.thiol group, an amino group, a guanidino group, a formyl group, a lower alkyl group, a lower alkenyl group, a lower alkynyl group, a lower acyl group, a carboxyl group, a sulfo group, a phosphono group, a lower alkoxyl group, a lower alkylthio group, a lower alkylamino group, a lower acyloxy group, a lower acylamino group, a lower alkoxycarbonyl group, a carbamoyl group, a lower alkylcarbamoyl group, a lower alkylsulfonylamino group or a sulfamoyl group, HetAr is a 5- to 10-membered aromatic ring containing 1-3 heteroatoms selected from a nitrogen atom, an oxygen atom and a sulfur atom, and optionally having substituent(s), X is a lower alkylene group optionally having substituent(s), a lower alkenylene group optionally having substituent(s), a lower alkynylene group optionally having substituent(s), or a thiophenylene group, Y is a carbonyl group, a thiocarbonyl group or a sulfonyl group, and A is -OR5 (R5 is a hydrogen atom or a lower alkyl group), a group of the following formula: wherein R6 and R7 may be the same or different and are each independently a hydrogen atom, a hydroxyl group, a lower alkyl group optionally having substituent(s), a lower alkenyl group optionally having substituent(s), a lower alkynyl group optionally having substituent(s) or a lower alkoxyl group optionally having substituent(s), or R6 and R7 may be bonded to form a cyclic amino group optionally having substituent(s), a group of the following formula (II-2): -U-CH(R6')R7' (II-2) wherein U is O or S, and R6' and R7' may be the same or different and are each independently a hydrogen atom, a hydroxyl group, a carboxyl group, a lower alkyl group optionally having substituent(s), a lower alkenyl group optionally having substituent(s), a lower alkynyl group optionally having substituent(s) or a lower alkoxyl group optionally having substituent(s), or R6' and R7' may be bonded to form a cyclic amino group optionally having substituent(s), or a group of the following formula (II-3): -NH-N(R6")R7" (II-3) wherein R6" and R7" may be the same or different and are each independently a hydrogen atom, a hydroxyl group, a lower alkyl group optionally having substituent(s), a lower alkenyl group optionally having substituent(s), a lower alkynyl group optionally having substituent(s) or a lower alkoxyl group optionally having substituent(s), or R6" and R7" may be bonded to form a cyclic amino group optionally having substituent(s), or a pharmaceutically acceptable salt thereof; and wherein "lower alkyl" implies a straight chain or branched chain or cyclic alkyl group having a carbon number of 1-6; "lower alkenyl" implies a straight chain or branched chain alkenyl group having a carbon number of 2-6; "lower alkynyl" implies a straight chain or branched chain alkynyl group having a carbon number of 2-6; "lower alkylene" implies a straight chain or branched chain or cyclic alkylene group having a carbon number of 1-6; "lower alkenylene" implies a straight chain or branched chain alkenylene group having a carbon number of 2-6; "lower alkynylene" implies a straight chain or branched chain alkynylene group having a carbon number of 2-6; and "lower acyl" implies an acyl group having a straight chain or branched chain or cyclic alkyl group or alkenyl group having a carbon number of 1 to 6.