Purine derivative compounds for medical use

A method for treatment of disease by reduction in macrophages-mediated bacterial killing, including administration to patients in need a compound of formula (I): wherein A is N or CH; B is NO, or S; R 1 is H, (C 1 -C 4 )alkyl group, methyl(C 1 -C 6 )cycloalkyl group or (C 1 -C 6 )cycloalkyl group; R 2 is an aryl, arylmethyl group or methylheteroaryl group as methylpyridine and methylthiophene; R 3 is absent when B is O or S, or is H or (C 1 -C 4 )alkyl group when B is N; R 4 is (C 1 -C 5 )alkyl group or (C 1 -C 4 )cycloalkyl group, groups bearing a carboxylic acid group, and (C 1 -C 5 )alkyl group or (C 1 -C 4 )cycloalkyl substituted by hydroxyl group, halogen group or methoxy group, when B is N, R 3 and R 4 can together form a 5- or 6-membered heterocycle substituted by carboxylic acid group, substituted by a halogen atom, hydroxyl group, methoxy group or hydroxymethyl group, or pharmaceutically acceptable salt. Also provided are new compounds relating to this use.