A compound of formula or a stereoisomeric form thereof, wherein R 1 is selected from the group consisting of a radical of formula (a-1), (a-2) and (a-3); wherein each R 6, R 7, R 8 independently is selected from the group consisting of fluoro; C 1-4 alkyl; C 1-4 alkyloxy; and C 1-4 alkyl substituted with 1, 2 or 3 fluoro atoms; R 9 is hydrogen or C 1-4 alkyl; each m 1, m 2, and m 3 is independently selected from 0, 1, 2, 3 and 4; p 2 is selected from 1, 2, 3, and 4; each p 1 and p 3 is independently selected from 1 and 2; or R 1 is selected from the group consisting of unsubstituted pyridinyl; pyridinyl substituted with 1 or 2 substituents selected from the group consisting of halogen, C 1-4 alkyl, trifluoromethyl and C 1-4 alkyloxy; and unsubstituted tetrahydropyranyl; R 2 is selected from the group consisting of hydrogen; C 1-4 alkyl; trifluoromethyl; C 3-8 cycloalkyl; C 1-4 alkyloxy; and cyano; R 3 is selected from the group consisting of hydrogen; C 1-4 alkyl; C 3-8 cycloalkyl; and C 1-4 alkyl substituted with 1, 2 or 3 fluoro atoms; Het is a 5- or 6- membered heterocyclic ring, selected from the group consisting of pyridinyl; pyrimidinyl; pyridazinyl; pyrazinyl; pyrrolyl; oxazolyl; thiazolyl; imidazolyl; pyrazolyl; isothiazolyl; isoxazolyl; oxadiazolyl and triazolyl; R 4 is selected from the group consisting of hydrogen; C 1-4 alkyl; C 1-4 alkyl substituted with 1, 2 or 3 fluoro atoms; (difluorocyclopropyl)methyl; (cyclopropyl)difluoromethyl; hydroxyC 1-4 alkyl; C 3-8 cycloalkyl; (C 3-8 cycloalkyl)-C 1-4 alkyl; C 1-4 alkyloxyC 1-6 alkyl; C 1-4 alkyloxy; C 1-4 alkyloxy substituted with 1, 2 or 3 fluoro atoms; (C 3-8 cycloalkyl)C 1-4 alkyloxy; (C 1-4 alkyloxyC 1-4 alkyl)oxy; (C 1-4 alkyl)-carbonyl; (C 1-4 alkyl)carbonylC 1-4 alkyl; (C 3-8 cycloalkyl)carbonyl; (C 3-8 cycloalkyl)-carbonylC 1-4 alkyl; unsubstituted phenyl; phenyl substituted with 1 or 2 substituents selected from the group consisting of halogen, C 1-4 alkyl, trifluoromethyl, trifluoromethoxy, cyano and C 1-4 alkyloxy; unsubstituted benzyl; benzyl substituted with 1 or 2 substituents selected from the group consisting of halogen, C 1-4 alkyl, trifluoromethyl, trifluoromethoxy, cyano and C 1-4 alkyloxy; unsubstituted tetrahydrofuranyl; tetrahydrofuranylmethyl; unsubstituted tetrahydropyranyl;tetrahydropyranylmethyl; pyridinylmethyl; quinolinylmethyl; (NR 10 R 11)C 1-4 alkyl; and NR 10 R 11; R 5 is hydrogen or fluoro; R 10 and R 11 are independently selected from hydrogen and C 1-4 alkyl, or taken together with the ring nitrogen atom may form a radical of Formula (b-1), (b-2) or (b-3) wherein each R 12, R 13 and R 14 independently is C 1-4 alkyl or C 1-4 alkyloxy; R 15 is hydrogen or C 1-4 alkyl; each q1, q2 and q3 is independently selected from 0, 1, 2, 3 and 4; s 1 is selected from 1, 2, 3 and 4; each s 2 and s 3 is independently selected from 1 and 2; or a pharmaceutically acceptable salt or a solvate thereof. each R 6, R 7, R 8 independently is selected from the group consisting of fluoro; C 1-4 alkyl; C 1-4 alkyloxy; and C 1-4 alkyl substituted with 1, 2 or 3 fluoro atoms; R 9 is hydrogen or C 1-4 alkyl; each m 1, m 2, and m 3 is independently selected from 0, 1, 2, 3 and 4; p 2 is selected from 1, 2, 3, and 4; each p 1 and p 3 is independently selected from 1 and 2; or R 1 is selected from the group consisting of unsubstituted pyridinyl; pyridinyl substituted with 1 or 2 substituents selected from the group consisting of halogen, C 1-4 alkyl, trifluoromethyl and C 1-4 alkyloxy; and unsubstituted tetrahydropyranyl; R 2 is selected from the group consisting of hydrogen; C 1-4 alkyl; trifluoromethyl; C 3-8 cycloalkyl; C 1-4 alkyloxy; and cyano; R 3 is selected from the group consisting of hydrogen; C 1-4 alkyl; C 3-8 cycloalkyl; and C 1-4 alkyl substituted with 1, 2 or 3 fluoro atoms; Het is a 5- or 6- membered heterocyclic ring, selected from the group consisting of pyridinyl; pyrimidinyl; pyridazinyl; pyrazinyl; pyrrolyl; oxazolyl; thiazolyl; imidazolyl; pyrazolyl; isothiazolyl; isoxazolyl; oxadiazolyl and triazolyl; R 4 is selected from the group consisting of hydrogen; C 1-4 alkyl; C 1-4 alkyl substituted with 1, 2 or 3 fluoro atoms; (difluorocyclopropyl)methyl; (cyclopropyl)difluoromethyl; hydroxyC 1-4 alkyl; C 3-8 cycloalkyl; (C 3-8 cycloalkyl)-C 1-4 alkyl; C 1-4 alkyloxyC 1-6 alkyl; C 1-4 alkyloxy; C 1-4 alkyloxy substituted with 1, 2 or 3 fluoro atoms; (C 3-8 cycloalkyl)C 1-4 alkyloxy; (C 1-4 alkyloxyC 1-4 alkyl)oxy; (C 1-4 alkyl)-carbonyl; (C 1-4 alkyl)carbonylC 1-4 alkyl; (C 3-8 cycloalkyl)carbonyl; (C 3-8 cycloalkyl)-carbonylC 1-4 alkyl; unsubstituted phenyl; phenyl substituted with 1 or 2 substituents selected from the group consisting of halogen, C 1-4 alkyl, trifluoromethyl, trifluoromethoxy, cyano and C 1-4 alkyloxy; unsubstituted benzyl; benzyl substituted with 1 or 2 substituents selected from the group consisting of halogen, C 1-4 alkyl, trifluoromethyl, trifluoromethoxy, cyano and C 1-4 alkyloxy; unsubstituted tetrahydrofuranyl; tetrahydrofuranylmethyl; unsubstituted tetrahydropyranyl;tetrahydropyranylmethyl; pyridinylmethyl; quinolinylmethyl; (NR 10 R 11)C 1-4 alkyl; and NR 10 R 11; R 5 is hydrogen or fluoro; R 10 and R 11 are independently selected from hydrogen and C 1-4 alkyl, or taken together with the ring nitrogen atom may form a radical of Formula (b-1), (b-2) or (b-3) wherein each R 12, R 13 and R 14 independently is C 1-4 alkyl or C 1-4 alkyloxy; R 15 is hydrogen or C 1-4 alkyl; each q1, q2 and q3 is independently selected from 0, 1, 2, 3 and 4; s 1 is selected from 1, 2, 3 and 4; each s 2 and s 3 is independently selected from 1 and 2; or a pharmaceutically acceptable salt or a solvate thereof.