A compound of formula wherein: - R 1 represents a five or six membered aryl or heteroaryl group optionally substituted by one or more substituents selected from the group consisting of halogen atom, C 1 -C 6 alkyl linear or branched, C 3 -C 12 cycloalkyl, hydroxyl, C 1 -C 6 alkoxy linear or branched and cyano group, - R 2 is selected from the group consisting of halogen atom and cyano group, - R 3 represents a five or six membered aryl or heteroaryl group optionally substituted by one or more substituents selected from the group consisting of halogen atom, cyano group, C 3 -C 12 cycloalkyl, hydroxyl, C 1 -C 6 alkoxy linear or branched, optionally substituted by one, two or three halogen atoms, C 1 -C 6 alkylthio, amino, mono or dialkylamino, C 1 -C 6 alcoxyalkyl, hydroxycarbonyl and C 2 -C 6 alcoxycarbonyl, and - R 4 represents independently: a) a hydroxyl group, b) -N(R 5)(R 6) group, wherein: i) R 5 and R 6 represent independently a C 3 -C 12 cycloalkyl group or C 3 -C 4 alkyl linear or branched, substituted by a carboxyl group (-COOH); or ii) R 5 and R 6 form together with the nitrogen atom to which they are bound a five or six membered saturated cycle comprising optionally a heteroatom selected from N and O, which is substituted by a carboxylic group (-COOH). and pharmaceutically acceptable salts thereof. - R 1 represents a five or six membered aryl or heteroaryl group optionally substituted by one or more substituents selected from the group consisting of halogen atom, C 1 -C 6 alkyl linear or branched, C 3 -C 12 cycloalkyl, hydroxyl, C 1 -C 6 alkoxy linear or branched and cyano group, - R 2 is selected from the group consisting of halogen atom and cyano group, - R 3 represents a five or six membered aryl or heteroaryl group optionally substituted by one or more substituents selected from the group consisting of halogen atom, cyano group, C 3 -C 12 cycloalkyl, hydroxyl, C 1 -C 6 alkoxy linear or branched, optionally substituted by one, two or three halogen atoms, C 1 -C 6 alkylthio, amino, mono or dialkylamino, C 1 -C 6 alcoxyalkyl, hydroxycarbonyl and C 2 -C 6 alcoxycarbonyl, and - R 4 represents independently: a) a hydroxyl group, b) -N(R 5)(R 6) group, wherein: i) R 5 and R 6 represent independently a C 3 -C 12 cycloalkyl group or C 3 -C 4 alkyl linear or branched, substituted by a carboxyl group (-COOH); or ii) R 5 and R 6 form together with the nitrogen atom to which they are bound a five or six membered saturated cycle comprising optionally a heteroatom selected from N and O, which is substituted by a carboxylic group (-COOH). a) a hydroxyl group, b) -N(R 5)(R 6) group, wherein: i) R 5 and R 6 represent independently a C 3 -C 12 cycloalkyl group or C 3 -C 4 alkyl linear or branched, substituted by a carboxyl group (-COOH); or ii) R 5 and R 6 form together with the nitrogen atom to which they are bound a five or six membered saturated cycle comprising optionally a heteroatom selected from N and O, which is substituted by a carboxylic group (-COOH). i) R 5 and R 6 represent independently a C 3 -C 12 cycloalkyl group or C 3 -C 4 alkyl linear or branched, substituted by a carboxyl group (-COOH); or ii) R 5 and R 6 form together with the nitrogen atom to which they are bound a five or six membered saturated cycle comprising optionally a heteroatom selected from N and O, which is substituted by a carboxylic group (-COOH).