Pyrazolo[3,4-B]pyridines and imidazo[1,5-B]pyridazines as PDE1 inhibitors

A compound according to formula (I)

• wherein
• A1=C, A2=N and R3=-NR6R7
• R1 is selected from the group consisting of hydrogen, linear or branched C1-4 alkyl and C3-4 cycloalkyl, wherein said linear or branched C1-4 alkyl and C3-4 cycloalkyl can optionally be substituted with one or more halogen;
• R2 is selected from the group consisting of linear or branched C1-6 alkyl, saturated monocyclic C3-6 cycloalkyl, oxetanyl, tetrahydrofuranyl and tetrahydropyranyl, wherein said linear or branched C1-6 alkyl and saturated monocyclic C3-6 cycloalkyl can optionally be substituted with one or more halogen, and wherein said oxetanyl, tetrahydrofuranyl and tetrahydropyranyl can be optionally substituted one or more times with a substituent selected from methyl and halogen;
• R4 is hydrogen;
• R5 is a 5-6 membered heteroaryl which can be substituted one or more times with one or more substituents selected from C1-4 alkoxy, —CH2—C1-4alkoxy, —CN, linear or branched C1-4 alkyl and C3-4 cycloalkyl, wherein said linear or branched C1-4 alkyl, said C3-4 cycloalkyl, said C1-4 alkoxy and said —CH2—C1-4alkoxy can optionally be substituted with one or more halogen;
• R6 is selected from the group consisting of hydrogen, linear or branched C1-6 alkyl and C3-6 cycloalkyl, wherein said linear or branched C1-6 alkyl and C3-6 cycloalkyl can be optionally substituted with one or more fluorine;
• and R7 is selected from the group consisting of hydrogen, linear or branched C1-6 alkyl, C3-6 cycloalkyl, oxetanyl, tetrahydrofuranyl, tetrahydropyranyl, —CH2-oxetanyl, —CH2-tetrahydrofuranyl, —CH2-tetrahydropyranyl and —CH2-pyrrolidinyl, wherein said linear or branched C1-6 alkyl, C3-6 cycloalkyl, oxetanyl, tetrahydrofuranyl, tetrahydropyranyl, —CH2-oxetanyl, —CH2-tetrahydrofuranyl, —CH2-tetrahydropyranyl and CH2-pyrrolidinyl-2-one can be optionally substituted with one or more substituents selected from methyl, methoxy, ethoxy, oxo and fluorine;
• or
• R6 and R7 are connected to form a 5-7 membered saturated heterocyclic ring with the nitrogen atom to which they are attached and 4-6 carbon atoms;
• wherein said heterocyclic ring can be optionally substituted with one or more substituents selected from methoxy, methyl and fluorine;
• or a pharmaceutically acceptable salt thereof.