Substituted tetrahydroquinoline compounds as indoleamine 2,3-dioxygenase inhibitors

1. A compound of formula (I), or a pharmaceutically acceptable salt thereof:

wherein:

X is selected from (1) a bond, (2) —O—, (3) —S— and (4) —NH—;

each occurrence of R 1 is independently selected from: (1) hydrogen, (2) halogen and (3) C 1-6 alkyl;

each of R 2 and R 3 is independently selected from: (1) hydrogen and (2) C 1-6 alkyl;

or alternatively, R 2 and R 3 together with the carbon to which they are attached form a C 3-5 cycloalkyl; and

R is selected from:

(1) aryl,

(2) heteroaryl and

(3) C 1-6 alkyl, optionally substituted with a C 3-5 cycloalkyl;

wherein each of the aryl of (1) and the heteroaryl of (2) is optionally substituted with one to four substituents independently selected from:

(a) halogen,

(b) —OH,

(c) —CN,

(d) C 1-6 alkyl, optionally substituted with one to four substituents independently selected from (i) halogen and (ii) C 3-6 cycloalkyl, and

(e) —NR a R a , wherein each occurrence of R a is independently selected from (i) hydrogen and (ii) C 1-6 alkyl.

2. The compound of claim 1 , or a pharmaceutically acceptable salt thereof, wherein:

X is selected from (1) a bond, (2) —O— and (3) —NH—;

each occurrence of R 1 is independently selected from: (1) hydrogen and (2) halogen;

R 2 is hydrogen and R 3 is C 1-4 alkyl;

or alternatively, R 2 and R 3 together with the carbon to which they are attached form a cyclopropyl; and

R is selected from:

(1) phenyl,

(2) heteroaryl, and

(3) C 1-4 alkyl, optionally substituted with a C 3-4 cycloalkyl;

wherein each of the phenyl of (1) and the heteroaryl of (2) is optionally substituted with one to four substituents independently selected from:

(a) halogen,

(b) —CN,

(c) C 1-6 alkyl, optionally substituted with one to four halogens, and

(d) —NR a R a , wherein each occurrence of R a is independently selected from (i) hydrogen and (ii) C 1-4 alkyl.

3. The compound of claim 1 , or a pharmaceutically acceptable salt thereof, wherein R is phenyl, optionally substituted with one to four substituents independently selected from:

(a) halogen,

(b) —CN,

(c) C 1-4 alkyl, optionally substituted with one to three halogens, and

(d) —NR a R a , wherein each occurrence of R a is independently selected from (i) hydrogen and (ii) C 1-4 alkyl.

4. The compound of claim 1 , or a pharmaceutically acceptable salt thereof, wherein R is a heteroaryl selected from pyridinyl and pyrimidinyl, each of which is optionally substituted with one to four substituents independently selected from:

(a) halogen,

(b) —CN,

(c) C 1-4 alkyl, optionally substituted with one to three halogens, and

(d) —NR a R a , wherein each occurrence of R a is independently selected from (i) hydrogen and (ii) C 1-4 alkyl.

5. The compound of claim 1 , or a pharmaceutically acceptable salt thereof, wherein R is selected from (1) methyl, (2) ethyl and (3) propyl, each of which is optionally substituted with a C 3-4 cycloalkyl.

6. The compound of claim 1 , or a pharmaceutically acceptable salt thereof, wherein R 2 is hydrogen and R 3 is selected from (1) methyl, (2) ethyl and (3) propyl.

7. The compound of claim 1 , or a pharmaceutically acceptable salt thereof, wherein R 2 and R 3 together with the carbon to which they are attached form a cyclopropyl or cyclobutyl.

8. The compound of claim 1 , or a pharmaceutically acceptable salt thereof, wherein one R 1 group is halogen and each of the three remaining R 1 groups is hydrogen.

9. The compound of claim 1 , or a pharmaceutically acceptable salt thereof, of formula (Ia):

wherein:

X is selected from (1) a bond, (2) —O— and (3) —NH—;

R 1 is a halogen;

R 2 is hydrogen;

R 3 is C 1-4 alkyl; and

R is selected from (1) phenyl and (2) a heteroaryl, each of which is optionally substituted with one to three substituents independently selected from:

(a) halogen, and

(b) C 1-4 alkyl, optionally substituted with one to three halogens.

10. The compound of claim 9 , or a pharmaceutically acceptable salt thereof,

wherein:

X is selected from (1) a bond and (2) —O—;

R 1 is a fluoro;

R 2 is hydrogen;

R 3 is selected from (1) methyl, (2) ethyl and (3) propyl; and

R is a heteroaryl selected from (1) pyridinyl and (2) pyrimidinyl, each of which is optionally substituted with one to three substituents independently selected from:

(a) halogen, and

(b) C 1-4 alkyl, optionally substituted with one to three halogens.

11. The compound of claim 1 , or a pharmaceutically acceptable salt thereof, of formula (Ib):

wherein:

n is 1 or 2;

X is selected from (1) a bond, (2) —O— and (3) —NH—;

each occurrence of R 1 is independently selected from: (1) hydrogen, (2) halogen and (3) C 1-6 alkyl; and

R is selected from:

(1) aryl,

(2) heteroaryl and

(3) C 1-6 alkyl, optionally substituted with a C 3-4 cycloalkyl;

wherein each of the aryl of (1) and the heteroaryl of (2) is optionally substituted with one to four substituents independently selected from:

(a) halogen,

(b) —CN,

(c) C 1-6 alkyl, optionally substituted with one to four halogens, and

(d) —NR a R a , wherein each occurrence of R a is independently selected from (i) hydrogen and (ii) C 1-6 alkyl.

12. The compound of claim 11 , or a pharmaceutically acceptable salt thereof, of formula (IC):

wherein:

X is selected from (1) a bond, (2) —O— and (3) —NH—;

R 1 is a halogen; and

R is selected from:

(1) phenyl,

(2) heteroaryl and

(3) C 1-4 alkyl; optionally substituted with a C 3-4 cycloalkyl;

wherein each of the phenyl of (1) and the heteroaryl of (2) is optionally substituted with one to three substituents independently selected from:

(a) halogen,

(b) —CN,

(c) C 1-4 alkyl, optionally substituted with one to three substituents independently selected from (i) halogen and (ii) C 3-4 cycloalkyl, and

(d) —NR a R a , wherein each occurrence of R a is independently selected from (i) hydrogen, (ii) methyl and (iii) ethyl.

13. The compound of claim 12 , or a pharmaceutically acceptable salt thereof:

wherein:

X is selected from (1) a bond, (2) —O— and (3) —NH—;

R 1 is a fluoro; and

R is selected from:

(1) phenyl,

(2) a heteroaryl selected from (1) pyridinyl and (2) pyrimidinyl,

(3) methyl, optionally substituted with a cyclopropyl and

(4) ethyl, optionally substituted with a cyclopropyl;

wherein each of the phenyl of (1) and heteroaryl of (2) is optionally substituted with one tothree substituents independently selected from:

(a) halogen,

(b) —CN,

(c) C 1-4 alkyl, optionally substituted with one to three halogens, and

(d) —N(CH 3 ) 2 .

14. The compound of claim 1 selected from the group consisting of:

N-(1-(5-(3-chlorophenoxy)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)-4-fluorobenzamide,

N-(1-(5-((2-(dimethylamino)pyrimidin-5-yl)oxy)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)-4-fluorobenzamide,

4-fluoro-N-(1-(5-(6-fluoropyridin-3-yl)oxy)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)benzamide,

N-(1-(5-((5-chloropyridin-3-yl)oxy)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)-4-fluorobenzamide,

N-(1-(5-(3-cyanophenoxy)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)-4-fluorobenzamide,

4-fluoro-N-(1-(5-(6-fluoropyridin-3-yl)oxy)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)benzamide,

4-fluoro-N-(1-(5-((4-methylpyridin-3-yl)oxy)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)benzamide,

N-(1-(5-((5-chloropyridin-3-yl)oxy)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)-4-fluorobenzamide,

N-(1-(5-(3-cyanophenoxy)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)-4-fluorobenzamide,

4-fluoro-N-(1-(5-((2-methylpyrimidin-5-yl)oxy)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)benzamide,

N-(1-(5-((2-(dimethylamino)pyrimidin-5-yl)oxy)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)-4-fluorobenzamide,

4-fluoro-N-(1-(5-((2-methylpyrimidin-5-yl)oxy)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)benzamide,

N-(1-(5-((3-chlorophenyl)amino)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)-4-fluorobenzamide,

N-(1-(5-(cyclopropylmethoxy)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)-4-fluorobenzamide,

4-fluoro-N-(1-(5-(2-methylpyrimidin-4-yl)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)benzamide,

4-fluoro-N-(1-(5-(5-fluoropyridin-3-yl)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)benzamide,

4-fluoro-N-(1-(5-(5-fluoropyridin-3-yl)-5,6,7,8-tetrahydroquinolin-2-yl)propyl)benzamide,

4-fluoro-N-(1-(5-(5-methylpyridin-3-yl)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)benzamide,

4-fluoro-N-(1-(5-(5-methylpyridin-3-yl)-5,6,7,8-tetrahydroquinolin-2-yl)propyl)benzamide,

4-fluoro-N-(1-(5-(5-(trifluoromethyl)pyridin-3-yl)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)benzamide,

4-fluoro-N-(1-(5-(5-(trifluoromethyl)pyridin-3-yl)-5,6,7,8-tetrahydroquinolin-2-yl)propyl)benzamide, and

4-fluoro-N-(1-(5-(2-methylpyrimidin-5-yl)-5,6,7,8-tetrahydroquinolin-2-yl)cyclopropyl)benzamide;

or a pharmaceutically acceptable salt thereof.

15. A composition which comprises an inert carrier and a compound of claim 1 or a pharmaceutically acceptable salt thereof.

16. A method for treating an IDO-associated disease or disorder in a mammalian subject having an IDO-associated disease or disorder, which comprises administering to the subject an effective amount of a compound of claim 1 or a pharmaceutically acceptable salt thereof.

17. A method for treating an IDO-associated disease or disorder in a mammalian subject having an IDO-associated disease or disorder, which comprises administering to the subject an effective amount of a compound of claim 1 or a pharmaceutically acceptable salt thereof in combination with another anti-cancer agent.

18. A method for treating an IDO-associated disease or disorder in a mammalian subject having an IDO-associated disease or disorder, which comprises administering to the subject an effective amount of a compound of claim 1 or a pharmaceutically acceptable salt thereof in combination with two additional anti-cancer agents.

19. The method of claim 16 , wherein the IDO-associated disease or disorder is a cancer, viral infection, HCV infection, depression, neurodegenerative disorders, trauma, age-related cataracts, organ transplantation, and autoimmune diseases.

20. The method of claim 19 , wherein the cancer is selected from colon cancer, pancreas cancer, breast cancer, prostate cancer, lung cancer, brain cancer, ovarian cancer, cervical cancer, testes cancer, renal cancer, head and neck cancer, lymphoma, leukemia and melanoma.