Novel (thio)urea compounds and the pharmaceutical compositions containing the same

Compound of formula I: (see formula) or a pharmaceutically acceptable salt thereof, wherein, X represents a sulfur atom or an oxygen atom; R1 represents a lower alkylsulfonyl group having 1 to 5 carbon atoms, an arylsulfonyl group or a lower alkylcarbonyl group having 1 to 5 carbon atoms which may be unsubstituted or substituted with a halogen atom; R2 represents a hydrogen atom, a methoxy group or a halogen; in case that A is -NHCH2, B represents: (Omitted) (wherein n is 0 or 1), or in the case that A is -CH2-, B represents 4-t-butylbenzyl, 3, 4-dimethylphenylethyl (Omitted) or an oleyl group; It represents -CH2- or -CH2CH2- Y; R3 represents a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms; and R4 represents a lower alkyl group having 1 to 5 carbon atoms or a phenyl group.