A compound of formula or a pharmaceutically acceptable salt thereof, wherein X is NH 2; R 1, R 2, R 3 are independently selected from the group consisting of H; halogen; CN; C OR 4; OR 4; C R 4; C N(R 4 R 4a); S 2 N(R 4 R 4a); S N(R 4 R 4a); S 2 R 4; S R 4; N(R 4)S 2 N(R 4a R 4b); N(R 4)S N(R 4a R 4b); SR 4; N(R 4 R 4a); OC R 4; N(R 4)C R 4a; N(R 4)S 2 R 4a; N(R 4)S R 4a; N(R 4)C N(R 4a R 4b); N(R 4)C OR 4a; OC N(R 4 R4 a); and C 1-6 alkyl, wherein C 1-6 alkyl is optionally substituted with one or more halogen, which are the same or different; R 4, R 4a, R 4b are independently selected from the group consisting of H; and C 1-6 alkyl, wherein C 1-6 alkyl is optionally substituted with one or more halogen, which are the same or different; T 1 is 4 to 7 membered heterocyclyl; 9 to 11 membered heterobicyclyl; phenyl; naphthyl; indenyl; or indanyl; wherein T 1 is optionally substituted with one or more R 5 and/or one or more R 6; R 5 is halogen; CN; C OR 7; OR 7; oxo (=O), where the ring is at least partially saturated; C R 7; C N(R 7 R 7a); S 2 N(R 7 R 7a); S N(R 7 R 7a); S 2 R 7; S R 7; N(R 7)S 2 N(R 7a R 7b); N(R 7)S N(R 7a R 7b); SR 7; N(R 7 R 7a); OC R 7; N(R 7)C R 7; N(R 7)S 2 R 7a; N(R 7)S R 7a; N(R 7)C N(R 7a R 7b); N(R 7)C OR 7a; OC N(R 7 R 7a); or C 1-6 alkyl, wherein C 1-6 alkyl is optionally substituted with one or more R 8; R 6 is T 2; C OR 9; OR 9; C R 9; C N(R 9 R 9a); S 2 N(R 9 R 9a); S N(R 9 R 9a); S 2 R 9; S R 9; N(R 9)S 2 N(R 9a R 9b); N(R 9)S N(R 9a R 9b); SR 9; N(R 9 R 9a); OC R 9; N(R 9)C R 9a; N(R 9)S 2 R 9a; N(R 9)S R 9a; N(R 9)C N(R 9a R 9b); N(R 9)C OR 9a; OC N(R 9 R 9a); or C 1-6 alkyl substituted with one or more T 2 and optionally substituted with one or more R 8; R 9, R 9a, R 9b are independently selected from the group consisting of R 9c; and R 9d, provided that at least one of R 9, R 9a, R 9b is R 9c; R 9c is T 2; or C 1-6 alkyl, wherein C 1-6 alkyl is substituted with one or more T 2 and optionally substituted with one or more R 8; R 7, R 7a, R 7b, R 9d are independently selected from the group consisting of H; and C 1-6 alkyl, wherein C 1-6 alkyl is optionally substituted with one or more R 8; R 8 is halogen; CN; C OR 10; OR 10; C R 10; C N(R 10 R 10a); S 2 N(R 10 R 10a); S N(R 10 R 10a); S 2 R 10; S R 10; N(R 10)S 2 N(R 10a R 10b); N(R 10)S N(R 10a R 10b); SR 10; N(R 10 R 10a); OC R 10; N(R 10)C R 10a; N(R 10)S 2 R 10a; N(R 10)S R 10a; N(R 10)C N(R 10a R 10b); N(R 10)C OR 10a; OC N(R 10 R 10a); or C 1-6 alkyl, wherein C 1-6 alkyl is optionally substituted with one or more halogen, which are the same or different; R 10, R 10a, R 10b are independently selected from the group consisting of H; and C 1-6 alkyl, wherein C 1-6 alkyl is optionally substituted with one or more halogen, which are the same or different; T 2 is C 3-7 cycloalkyl; 4 to 7 membered heterocyclyl; 9 to 11 membered heterobicyclyl; phenyl; naphthyl; indenyl; or indanyl, wherein T 2 is optionally substituted with one or more R 11; R 11 is halogen; CN; C OR 12; OR 12; oxo (=O), where the ring is at least partially saturated; C R 12; C N(R 12 R 12a); S 2 N(R 12 R 12a); S N(R 12 R 12a); S 2 R 12; S R 12; N(R 12)S 2 N(R 12a R 12b); N(R 12)S N(R 12a R 12b); SR 12; N(R 12 R 12a); OC R 12; N(R 12)C R 12a; N(R 12)S 2 R 12a; N(R 12)S R 12a; N(R 12)C N(R 12a R 12b); N(R 12)C OR 12a; OC N(R 12 R 12a); or C 1-6 alkyl, wherein C 1-6 alkyl is optionally substituted with one or more halogen which are the same or different; R 12, R 12a, R 12b are independently selected from the group consisting of H; and C 1-6 alkyl, wherein C 1-6 alkyl is optionally substituted with one or more halogen, which are the same or different, provided that the following compound is excluded: 6-(3,4-dimethoxyphenyl)-[1,3,4]triazolo-[1,5a]pyridine-2-amine. 6-(3,4-dimethoxyphenyl)-[1,3,4]triazolo-[1,5a]pyridine-2-amine.