Pyridazin-3(2h)-one derivatives as pde4 inhibitors

A compound of formula (I)

• wherein
• R1 represents:
• a hydrogen atoms
• a group chosen from acyl, alkoxycarbonyl, carbamoyl, monoalkylcarbamoyl and dialkylcarbamoyl;
• an alkyl group, which is optionally substituted by one or more substituents chosen from halogen atoms, and hydroxy, alkoxy, aryloxy, alkylthio, oxo, amino, mono- and di-alkylamino, acylamino, carbamoyl sand mono- and alkylcarbamoyl groups;
• or
• a group of formula
• —(CH2)n—R6
• wherein n is an integer from 0 to 4 and wherein
• R6 represents:
• a cycloalkyl group;
• an aryl group, which is optionally substituted by one or more substituents chosen from halogen atoms, and alkyl, hydroxy, alkoxy, alkylenedioxy, alkylthio, amino, mono- and di-alkylamino, nitro, acyl, hydroxycarbonyl, alkoxycarbonyl, carbamoyl, mono- and di-alkylcarbamoyl, cyano, trifluoromethyl, difluoromethoxy and trifluoromethoxy groups;
• or
• 3- to 7-membered ring comprising from 1 to 4 heteroatoms chosen from nitrogen, oxygen and sulphur, wherein the 3- to 7-membered ring is optionally substituted by one or more substituents chosen from halogen atoms, and alkyl, hydroxy, alkoxy, alkylenedioxy, amino, mono- and di-alkylamino, nitro, cyano and trifluoromethyl groups;
• R2 represents a substituent chosen from R1 and an alkyl group, wherein the alkyl group is substituted by a hydroxycarbonyl or an alkoxycarbonyl group,
• R3 and R5, each independently. represent a monocyclic or bicyclic aryl group, wherein each monocyclic or bicyclic aryl group is independently optionally substituted by one or more substituents chosen from:
• halogen atoms;
• alkyl and alkylene groups, wherein the alkyl and alkylene groups, independently, optionally substituted by one or more substituents chosen from halogen atoms, and phenyl, hydroxy, alkoxy, aryloxy, alkylthio, oxo, amino, mono- and di-alkylamino, acylamino, hydroxycarbonyl, alkoxycarbonyl, carbamoyl and mono- and di-alkylcarbamoyl groups;
• and
• phenyl, hydroxy, alkylenedioxy, alkoxy, cycloalkyloxy, alkylthio, alkylsulphinyl, amino, mono- and di-alkylamino, acylamino, nitro, acyl, hydroxycarbonyl, alkoxycarbonyl, carbamoyl, mono- and di-alkylcarbamoyl, ureido, N′-alkylureido, N′,N′-dialkylureido, alkylsulphamido, aminosuphonyl, mono- and di-alkylaminosulphonyl, cyano, difluoromethoxy and trifluoromethoxy groups;
• R4 represents:
• a hydrogen atom;
• a hydroxy, alkoxy, amino, mono- or di-alkylamino group;
• an alkyl group, which is optionally substituted by one or more substituents chosen from halogen atoms, and hydroxy, alkoxy, aryloxy, alkylthio, oxo, amino, mono- and di-alkylamino, acylamino, hydroxycarbonyl, alkoxycarbonyl, carbamoyl and mono- and di-alkylcarbamoyl groups;
• or
• a group of formula
• —(CH2)n—R6
• with the proviso that when simultaneously R2 is H, and R3 and R5 are unsubstituted phenyl, R1 is not methyl;
• or a pharmaceutically acceptable salt of a compound of formula (I).