A compound of formula wherein X 1 is selected from the group consisting of: N and CH; X 2 is selected from the group consisting of: N and CF; with the proviso that at least one of X 1 and X 2 is N; A is selected from the group consisting of: R 4 is selected from the group consisting of: azetidinyl, pyrrolidinyl, piperidinyl, piperazinyl, morpholinyl, tetrahydropyranyl, oxazolidinyl, C 3-8 -cycloalkyl, phenyl, pyridinyl, pyrazinyl, pyridazinyl, pyrimidinyl, [1,3,5]triazinyl, triazolyl, thiazolyl, imidazo[1,2-a]pyridin-2-yl, 2,3-dihydro-1H-isoindolyl, oxazolyl and oxadiazolyl, wherein each R 4 is optionally substituted with one or more groups independently of each other selected from the group consisting of halogen, OH, CO 2 H, CN, CF 3, C 1-3 -alkyl, C 3-6 -cycloalkyl, C 1-3 -alkyl-O-, (R N) 2 N-, C 1-3 -alkyl-C(=O)-, C 1-4 -alkyl-O-C(=O)-, (R N) 2 N-C(=O)-, (R N) 2 N-C 1-3 -alkyl-, C 3-6 -cycloalkyl-C 1-3 -alkyl-O-, C 1-3 -alkyl-SO 2 -, (R N) 2 N-SO 2 -, 2-oxo-pyrrolidinyl and C 1-3 -alkyl-C(=O)-(R N)N-C 1-3 -alkyl-; and wherein a -CH 2 - group of the pyrrolidinyl, 2,3-dihydro-1H-isoindolyl, oxazolidinyl, piperidinyl or piperazinyl group of R 4 is optionally replaced with a -C(=O)-, -S(=O)- or -S(=O) 2 - group; R N is selected from the group consisting of: H and C 1-4 -alkyl, wherein, if several R N groups are present, they may be identical or different from one another; R 5 is selected from the group consisting of: CN and OH; or, R 4 and R 5 groups together with the carbon atom, to which they are attached, may form the following group: wherein each of the above-mentioned alkyl and -O-alkyl groups may be linear or branched and are optionally substituted by one or more F; or a pharmaceutically acceptable salt thereof. X 1 is selected from the group consisting of: N and CH; X 2 is selected from the group consisting of: N and CF; A is selected from the group consisting of: R 4 is selected from the group consisting of: azetidinyl, pyrrolidinyl, piperidinyl, piperazinyl, morpholinyl, tetrahydropyranyl, oxazolidinyl, C 3-8 -cycloalkyl, phenyl, pyridinyl, pyrazinyl, pyridazinyl, pyrimidinyl, [1,3,5]triazinyl, triazolyl, thiazolyl, imidazo[1,2-a]pyridin-2-yl, 2,3-dihydro-1H-isoindolyl, oxazolyl and oxadiazolyl, wherein each R 4 is optionally substituted with one or more groups independently of each other selected from the group consisting of halogen, OH, CO 2 H, CN, CF 3, C 1-3 -alkyl, C 3-6 -cycloalkyl, C 1-3 -alkyl-O-, (R N) 2 N-, C 1-3 -alkyl-C(=O)-, C 1-4 -alkyl-O-C(=O)-, (R N) 2 N-C(=O)-, (R N) 2 N-C 1-3 -alkyl-, C 3-6 -cycloalkyl-C 1-3 -alkyl-O-, C 1-3 -alkyl-SO 2 -, (R N) 2 N-SO 2 -, 2-oxo-pyrrolidinyl and C 1-3 -alkyl-C(=O)-(R N)N-C 1-3 -alkyl-; and wherein a -CH 2 - group of the pyrrolidinyl, 2,3-dihydro-1H-isoindolyl, oxazolidinyl, piperidinyl or piperazinyl group of R 4 is optionally replaced with a -C(=O)-, -S(=O)- or -S(=O) 2 - group; R N is selected from the group consisting of: H and C 1-4 -alkyl, wherein, if several R N groups are present, they may be identical or different from one another; R 5 is selected from the group consisting of: CN and OH; or, R 4 and R 5 groups together with the carbon atom, to which they are attached, may form the following group: