A compound of formula wherein A is N or CH; R 1 is selected from the group consisting of C 1-6 -alkyl, C 3-6 -cycloalkyl, heterocyclyl, -O-R 2, -S-R 2, -NH-R 2 and -N(R 2) 2, wherein each R 2 is independently selected from the group consisting of C 1-6 -alkyl, C 3-6 -cycloalkyl, heterocyclyl, -(C 1-2 -alkyl)-(C 3-6 -cycloalkyl), -(C 1- 2 -alkyl)-heterocyclyl, -(C 1-2 -alkyl)-aryl, -(C 1-2 -alkyl)-heteroaryl and -(C 1-2 -alkyl)-C≡CH; wherein each heterocyclyl of R 1 and R 2 is a 4- to 7-membered saturated carbocyclic group, in which 1 or 2 CH 2 -moieties are independently of each other replaced by an atom or group selected from the group consisting of NH, O, S, -S(=O)-, -S(=O) 2 - and -C(=O)-; and wherein each aryl is selected from the group consisting of phenyl and naphthyl; and wherein each heteroaryl is a 5- or 6-membered heteroaromatic ring which contains 1, 2 or 3 heteroatoms independently selected from the group consisting of =N-, -NH-, -O- and -S-, wherein in heteroaromatic groups containing a -CH=N- unit, this group is optionally replaced by -NH-C(=O)-; and wherein each of the alkyl, cycloalkyl, heterocyclyl, aryl and heteroaryl groups of R 1 and R 2 is optionally independently substituted with one or more substituents independently selected from the group consisting of F, Cl, CN, OH, C 1-3 -alkyl, -O-(C 1-3 -alkyl), -C(=O)-(C 1-3 -alkyl) and -C(=O)-(C 3-7 -cycloalkyl); wherein each of the above-mentioned alkyl groups may be linear or branched and is optionally substituted by one or more F; or a salt thereof. A is N or CH; R 1 is selected from the group consisting of C 1-6 -alkyl, C 3-6 -cycloalkyl, heterocyclyl, -O-R 2, -S-R 2, -NH-R 2 and -N(R 2) 2, wherein each R 2 is independently selected from the group consisting of C 1-6 -alkyl, C 3-6 -cycloalkyl, heterocyclyl, -(C 1-2 -alkyl)-(C 3-6 -cycloalkyl), -(C 1- 2 -alkyl)-heterocyclyl, -(C 1-2 -alkyl)-aryl, -(C 1-2 -alkyl)-heteroaryl and -(C 1-2 -alkyl)-C≡CH; wherein each heterocyclyl of R 1 and R 2 is a 4- to 7-membered saturated carbocyclic group, in which 1 or 2 CH 2 -moieties are independently of each other replaced by an atom or group selected from the group consisting of NH, O, S, -S(=O)-, -S(=O) 2 - and -C(=O)-; and wherein each aryl is selected from the group consisting of phenyl and naphthyl; and wherein each heteroaryl is a 5- or 6-membered heteroaromatic ring which contains 1, 2 or 3 heteroatoms independently selected from the group consisting of =N-, -NH-, -O- and -S-, wherein in heteroaromatic groups containing a -CH=N- unit, this group is optionally replaced by -NH-C(=O)-; and wherein each of the alkyl, cycloalkyl, heterocyclyl, aryl and heteroaryl groups of R 1 and R 2 is optionally independently substituted with one or more substituents independently selected from the group consisting of F, Cl, CN, OH, C 1-3 -alkyl, -O-(C 1-3 -alkyl), -C(=O)-(C 1-3 -alkyl) and -C(=O)-(C 3-7 -cycloalkyl); wherein each heterocyclyl of R 1 and R 2 is a 4- to 7-membered saturated carbocyclic group, in which 1 or 2 CH 2 -moieties are independently of each other replaced by an atom or group selected from the group consisting of NH, O, S, -S(=O)-, -S(=O) 2 - and -C(=O)-; and wherein each aryl is selected from the group consisting of phenyl and naphthyl; and wherein each heteroaryl is a 5- or 6-membered heteroaromatic ring which contains 1, 2 or 3 heteroatoms independently selected from the group consisting of =N-, -NH-, -O- and -S-, wherein in heteroaromatic groups containing a -CH=N- unit, this group is optionally replaced by -NH-C(=O)-; and wherein each of the alkyl, cycloalkyl, heterocyclyl, aryl and heteroaryl groups of R 1 and R 2 is optionally independently substituted with one or more substituents independently selected from the group consisting of F, Cl, CN, OH, C 1-3 -alkyl, -O-(C 1-3 -alkyl), -C(=O)-(C 1-3 -alkyl) and -C(=O)-(C 3-7 -cycloalkyl);