A compound of formula wherein: R1 is hydrogen, halogen or a group selected from amino, straight or branched C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, cycloalkyl-alkyl, aryl, arylalkyl, heterocyclyl and heterocyclylalkyl; X is a single bond or a divalent radical selected from -NR'-, -CONR'-, -NH-CO-NH-, -O-, -S-, -SO 2 - and -OSO 2 -, wherein R' is hydrogen or a group selected from straight or branched C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, cycloalkyl-alkyl, aryl, arylalkyl, heterocyclyl and heterocyclylalkyl; one of Y and Z is nitrogen and the other is N-R3, wherein R3 is hydrogen or a group selected from straight or branched C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, cycloalkyl-alkyl, aryl, arylalkyl, heterocyclyl and heterocyclylalkyl or is a group -(CH 2) n -, wherein n is 2 or 3, forming a ring with R2, or Y is oxygen and Z is nitrogen, or Y is nitrogen and Z is oxygen; R2 is a group selected from -NR"R"', -N(OR"')R" and OR", wherein R" and R'" are, each independently, hydrogen or a group selected from straight or branched C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, cycloalkyl-alkyl, aryl, arylalkyl, heterocyclyl and heterocyclylalkyl or, together with the nitrogen atom to which they are bonded, R" and R'" may form a 5 to 6 membered heteroaryl or heterocyclyl group, optionally containing one additional heteroatom selected among N, O and S; or a pharmaceutically acceptable salt thereof, wherein any of the above R1, R2, R3, R', R" and R"' groups may be optionally substituted, in any of their free positions, by one or more groups, for instance 1 to 6 groups, independently selected from: halogen, nitro, oxo (=O), cyano, C 1 -C 6 alkyl, polyfluorinated alkyl, polyfluorinated alkoxy, alkenyl, alkynyl, hydroxyalkyl, aryl, arylalkyl, heterocyclyl C 3 -C 7 cycloalkyl, hydroxy, alkoxy, aryloxy, heterocyclyloxy, methylenedioxy, alkylcarbonyloxy, arylcarbonyloxy, cycloalkenyloxy, heterocyclylcarbonyloxy, alkylideneaminooxy, carboxy, alkoxycarbonyl, aryloxycarbonyl, cycloalkyloxycarbonyl, heterocyclyloxycarbonyl, amino, ureido, alkylamino, dialkylamino, arylamino, diarylamino, heterocyclylamino, formylamino, alkylcarbonylamino, arylcarbonylamino, heterocyclylcarbonylamino, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, arylaminocarbonyl, heterocyclylaminocarbonyl, alkoxycarbonylamino, hydroxyaminocarbonyl alkoxyimino, alkylsulfonylamino, arylsulfonylamino, heterocyclylsulfonylamino, formyl, alkylcarbonyl, arylcarbonyl, cycloalkylcarbonyl, heterocyclylcarbonyl, heterocyclylsulfonyl, alkylsulfonyl, arylsulfonyl, aminosulfonyl, alkylaminosulfonyl, dialkylaminosulfonyl, arylaminosulfonyl, heterocyclylaminosulfonyl, arylthio, alkylthio, phosphonate and alkylphosphonate; and, in their turn, each of the above substituent may be further substituted by one or more of the aforementioned groups. R1 is hydrogen, halogen or a group selected from amino, straight or branched C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, cycloalkyl-alkyl, aryl, arylalkyl, heterocyclyl and heterocyclylalkyl; X is a single bond or a divalent radical selected from -NR'-, -CONR'-, -NH-CO-NH-, -O-, -S-, -SO 2 - and -OSO 2 -, wherein R' is hydrogen or a group selected from straight or branched C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, cycloalkyl-alkyl, aryl, arylalkyl, heterocyclyl and heterocyclylalkyl; one of Y and Z is nitrogen and the other is N-R3, wherein R3 is hydrogen or a group selected from straight or branched C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, cycloalkyl-alkyl, aryl, arylalkyl, heterocyclyl and heterocyclylalkyl or is a group -(CH 2) n -, wherein n is 2 or 3, forming a ring with R2, or Y is oxygen and Z is nitrogen, or Y is nitrogen and Z is oxygen; Y is oxygen and Z is nitrogen, or Y is nitrogen and Z is oxygen; R2 is a group selected from -NR"R"', -N(OR"')R" and OR", wherein R" and R'" are, each independently, hydrogen or a group selected from straight or branched C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, cycloalkyl-alkyl, aryl, arylalkyl, heterocyclyl and heterocyclylalkyl or, together with the nitrogen atom to which they are bonded, R" and R'" may form a 5 to 6 membered heteroaryl or heterocyclyl group, optionally containing one additional heteroatom selected among N, O and S;