Pyridazinones as DAAO enzyme inhibitors

A compound of formula (I), or a pharmaceutically acceptable salt thereof:

• wherein
• R1 is chosen from a hydrogen or fluorine atom or a trifluoromethyl group;
• R2 is chosen from a C2-C8 alkyl, C3-C8 cycloalkyl, tetrahydropyranyl, or —NR3R4 group,
• wherein the alkyl, cycloalkyl and tetrahydropyranyl groups are unsubstituted or substituted by at least one substituent chosen from halogen, hydroxyl, cyano, carboxyl, C1-C6 alkyl, difluoromethyl, trifluoromethyl, C1-C6 alkoxy, difluoromethoxy or trifluoromethoxy;
• R3 and R4 are each independently chosen from a hydrogen atom or a C1-C6 alkyl group, or R3 and R4 together with the nitrogen atom to which they are attached form a saturated or unsaturated 4- to 8-membered heterocyclic ring, wherein each alkyl group or the heterocyclic ring is unsubstituted or substituted by at least one substituent chosen from halogen, hydroxyl, cyano, carboxyl, C1-C6 alkyl, difluoromethyl, trifluoromethyl, C1-C6 alkoxy, difluoromethoxy or trifluoromethoxy;
• with the proviso that the compound of formula (I) is not:
• 2,3 -dihydro-4-hydroxy-6-morpholinopyridazin-3 -one, or
• 6-amino-4-hydroxy-pyridazinone.