wherein:

B¹, B² and B³ are same or different and each stands for hydrogen, halogen, lower alkyl or lower alkyloxy;

R¹ and R² are same or different and each stands for

1) hydrogen,

2) a 3-10 membered aliphatic ring group of the formula [A]

wherein R⁵ either stands for a substituent selected from later specified Group α, or two R⁵'s together form oxo group; Y stands for —CH₂—, —NR⁶— or —O—; R⁶ stands for a substituent selected from the group consisting of hydrogen, optionally fluorine-substituted lower alkyl, lower alkylcarbonyl, lower alkyloxycarbonyl, lower alkylsulfonyl, carbamoyl, mono-lower alkylcarbamoyl and di-lower alkylcarbamoyl; and a is an integer of 0-4, or

3) a lower alkyl group which optionally has substituent(s) selected from Group α or a 3-10 membered aliphatic ring group represented by the formula [A],

provided R¹ and R² are not hydrogen atoms at the same time;

R³ stands for hydrogen or a lower alkyl which optionally has substituents selected from Group α;

R⁴ stands for hydrogen or a lower alkyl;

W is a divalent group which stands for a mono- or bi-cyclic, 3-8 membered aromatic heterocycle wherein if the heterocycle is a pyrazole ring, the pyrazole ring may be substituted by methyl; and

Ar stands for mono- or bi-cyclic, aromatic carbocycle, optionally having one, two or more substitutents selected from Group β;

wherein Group α represents halogen, hydroxyl, amino, mono-lower alkylamino, di-lower alkylamino, optionally fluorine-substituted lower alkyloxy, lower alkyloxycarbonyl, (lower alkyloxycarbonyl)amino, (lower alkyloxycarbonyl)lower alkylamino, lower alkylcarbonyl, lower alkylcarbonyloxy, (lower alkylcarbonyl)amino, (lower alkylcarbonyl) lower alkylamino, carbamoyl, mono-lower alkylcarbamoyl, di-lower alkylcarbamoyl, carbamoylamino, mono-lower alkylcarbamoylamino, di-lower alkylcarbamoylamino, (mono-lower alkylcarbamoyl)lower alkylamino, (di-lower alkylcarbamoyl)lower alkylamino, carbamoyloxy, mono-lower alkylcarbamoyloxy, di-lower alkylcarbamoyloxy, lower alkylsulfonyl, lower alkylsulfonylamino, sulfamoyl, mono-lower alkylsulfamoyl, di-lower alkylsulfamoyl, sulfamoylamino, (mono-lower alkylsulfamoyl)amino, (di-lower alkylsulfamoyl)amino, (mono-lower alkylsufamoyl)lower alkylamino or (di-lower alkylsulfamoyl)lower alkylamino;

wherein Group β represents halogen, hydroxyl, amino, cyano, mono-lower alkylamino, di-lower alkylamino, optionally fluorine-substituted lower alkyl, optionally fluorine-substituted lower alkyloxy, lower alkyloxycarbonyl, (lower alkyloxycarbonyl)amino, (lower alkyloxycarbonyl)lower alkylamino, carboxyl, lower alkylcarbonyl, lower alkylcarbonyloxy, (lower alkylcarbonyl) amino, (lower alkylcarbonyl)lower alkylamino, di-lower alkylcarbamoyl, di-lower alkylcarbamoylamino, (di-lower alkylcarbamoyl)lower alkylamino, di-lower alkylcarbamoyloxy, lower alkylsulfonyl, lower alkylsufonylamino, di-lower alkylsulfamoyl, sulfamoylamino, (di-lower alkylsulfamoyl)amino, (di-lower alkylsulfamoyl)lower alkylamino, or 5-6 membered aliphatic carbocycle or heterocycle which is optionally substituted with a group selected from group γ; and

wherein Group γ represents lower alkylcarbonyl, lower alkylsulfonyl or lower alkyloxycarbonyl;