Ring-fused heterocyclic compound

1. A ring-fused heterocyclic compound represented by the general formula (I) or a pharmaceutically acceptable salt thereof:

wherein R 1 represents lower alkyl optionally substituted with halogen;

R 2 represents lower alkyl optionally substituted with cycloalkyl optionally substituted with halogen, or with phenyl optionally substituted with halogen;

R 3 represents:

wherein n represents 0 or 1,

R 3a represents a hydrogen atom or optionally substituted lower alkyl,

R 3b and R 3c may be the same or different, and each represents a hydrogen atom, optionally substituted lower alkyl, optionally substituted cycloalkyl, optionally substituted aryl, an optionally substituted aromatic heterocyclic group, an optionally substituted aliphatic heterocyclic group, —OR 3d wherein R 3d represents an optionally substituted aliphatic heterocyclic group, or —C(═O)R 3j wherein R 3j represents optionally substituted lower alkyl, optionally substituted cycloalkyl, or an optionally substituted aliphatic heterocyclic group, or R 3b and R 3c are combined together with the adjacent nitrogen atom thereto to form an optionally substituted nitrogen-containing heterocyclic group;

Q represents cyano,

W 1 represents C—R 4 wherein R 4 represents a hydrogen atom, and

W 2 represents C—R 5 wherein, R 5 represents a hydrogen atom, halogen, or lower alkyl.

2. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 1 , wherein R 3 is

3. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 1 , wherein R 3 is

4. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 3 , wherein n is 0.

5. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 4 , wherein R 3b is optionally substituted lower alkyl or an optionally substituted aliphatic heterocyclic group.

6. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 1 , wherein R 1 is lower alkyl optionally substituted with halogen.

7. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 1 , wherein R 1 is lower alkyl substituted with halogen.

8. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 1 , wherein R 2 is lower alkyl optionally substituted with cycloalkyl optionally substituted with halogen.

9. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 1 , wherein R 2 is cyclohexylmethyl optionally substituted with halogen.

10. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 1 , wherein R 2 is difluorocyclohexylmethyl.

11. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 1 , wherein W 1 is C—R 4 .

12. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 11 , wherein R 4 is a hydrogen atom.

13. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 1 , wherein W 2 is C—R 5 .

14. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 13 , wherein R 5 is a hydrogen atom.

15. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 13 , wherein R 5 is halogen.

16. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 13 , wherein R 5 is lower alkyl.

17. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 1 , wherein Q is cyano, W1 is C—R 4 , and W 2 is C—R 5 .

18. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 17 , wherein R 1 is lower alkyl optionally substituted with halogen.

19. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 17 , wherein R 2 is cyclohexylmethyl optionally substituted with halogen.

20. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 17 , wherein R 4 is a hydrogen atom.

21. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 17 , wherein R 5 is a hydrogen atom.

22. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 17 , wherein R 5 is halogen.

23. The ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 17 , wherein R 5 is lower alkyl.

24. A pharmaceutical composition, which comprises, as an active ingredient, the ring-fused heterocyclic compound or a pharmaceutically acceptable salt thereof according to claim 1 .

25. A method for treating pruritus, which comprises a step of administering an effective amount of the ring-fused heterocyclic compound selected from the group consisting of:

6-Chloro-N-(4,4-difluorocyclohexyl)-3-[(4,4-difluorocyclohexyl)methyl]-2-(1,1-difluoroethyl)imidazo[1,2-a]pyridine-7-carboxamide,

5-Cyano-3-[4,4-difluorocyclohexyl)methyl]-N-(tetrahydro-2H-pyran-4-yl)-2-(trifluoromethyl)imidazo[1,2-a]pyridine-7-carboxamide,

5-Cyano-N-(cyclopropylmethyl)-3-[(4,4-difluorocyclohexyl)methyl]-2-(trifluoromethyl)imidazo[1,2-a]-pyridine-7-carboxamide,

5-Cyano-3-[(4,4-difluorocyclohexyl)methyl]-N-(2-methoxy-2-methylpropyl)-2-(trifluoromethyl)imidazo[1,2-a]pyridine-7-carboxamide,

5-Chloro-3-[(4,4-difluorocyclohexyl)methyl]-N-(2-oxaspiro[3,3]heptan-6-yl)-2-(trifluoromethyl)imidazo[1,2-a]pyridine-7-carboxamide,

5-Cyano-3-[(4,4-difluorocyclohexyl)methyl]-2-(1,1-difluoroethyl)-N-(2-methoxy-2-methylpropyl)imidazo[1,2-a]pyridine-7-carboxamide,

6-Chloro-5-cyano-3-[(4,4-difluorocyclohexyl)methyl]-N-(2-methoxy-2-methylpropyl)-2-(trifluoromethyl)imidazo[1,2-a]pyridine-7-carboxamide,

5-Chloro-N-[(1-cyanocyclopropyl)methyl]-3-[(4,4-difluorocyclohexyl)methyl]-2-(trifluoromethyl)imidazo[1,2-a]pyridine-7-carboxamide,

N-[(1R,2S,4S)-7-Oxabicyclo[2,2,1]heptan-2-yl]-5-cyano-3-[(4,4-difluorocyclohexyl)methyl]-2-(trifluoromethyl)imidazo[1,2-a]pyridine-7-carboxamide,

N-[(1R,2S,4S)-7-Oxabicyclo[2,2,1]heptan-2-yl]-5-cyano-3-[(4,4-difluorocyclohexyl)methyl]-2-isopropylimidazo[1,2-a]pyridine-7-carboxamide,

5-Cyano-3-[(4,4-difluorocyclohexyl)methyl]-6-methyl-N-(tetrahydro-2H-pyran-4-yl)-2-(trifluoromethyl)imidazo[1,2-a]pyridine-7-carboxamide,

5-Cyano-3-[(4,4-difluorocyclohexyl)methyl]-N-[3-(dimethylamino)-2,2-dimethylpropyl]-2-(trifluoromethyl)imidazo[1,2-a]pyridine-7-carboxamide,

N-[(1R,2S,4S)-7-Oxabicyclo[2,2,1]heptan-2yl]-5-cyano-3-[(4,4-difluorocyclohexyl)methyl]-2-(1,1-difluoroethyl)imidazo[1,2-a]pyridine-7-carboxamide,

5-Cyano-3-[(4,4-difluorocyclohexyl)methyl]-2-(1,1-difluoroethyl)-N-(2-methoxy-2-methylpropyl)-6-methylimidazo[1,2-a]pyridine-7-carboxamide,

5-Cyano-3-[(4,4-difluorocyclohexyl)methyl]-2-(1,1-difluoroethyl)-6-methyl-N-tetrahydro-2H-pyran-4-yl)imidazo[1,2-a]pyridine-7-carboxamide,

5-Cyano-3-[(4,4-difluorocyclohexyl)methyl]-N-(2-methoxy-d3-2-methylpropyl)-2-(trifluoromethyl)imidazo[1,2-a]pyridine-7-carboxamide,

5-Cyano-3-[(4,4-difluorocyclohexyl)methyl]-N-[2-methyl-2-(methylsulfonyl)propyl]-2-(trifluoromethyl)imidazo[1,2-a]pyridine-7-carboxamide,

5-Cyano-3-[(4,4-difluorocyclohexyl)methyl]-2-(1,1-difluoroethyl)-N-(2-methoxy-d3-2-methylpropyl)-6-methylimidazo[1,2-a]pyridine-7-carboxamide,

5,6-Dichloro-3-[(4,4-difluorocyclohexyl)methyl]-N-(tetrahydro-2H-pyran-4-yl)-2-(trifluoromethyl)imidazo[1,2-a]pyridine-7-carboxamide,

5-Cyano-3-[(4,4-difluorocyclohexyl)methyl]-2-(1,1-difluoroethyl)-N-(2-methoxy-d3-2methylpropyl)imidazo[1,2-a]pyridine-7-carboxamide,

5-Chloro-3-[(4,4-difluorocyclohexyl)methyl]-N-[2-methyl-2-(methylsulfonyl)propyl]-2-(trifluoromethyl)imidazo[1,2-a]pyridine-7-carboxamide, and

3-(4-Chlorobenzyl)-5-methyl-N-(tetrahydro-2H-pyran-4-yl)-2-(trifluoromethyl)imidazo[1,2-a]pyridine-7-carboxamide,

or a pharmaceutically acceptable salt thereof.