Substituted tricyclic compounds as indoleamine 2,3-dioxygenase inhibitors

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

wherein:

n is 0 or 1;

A is selected from (1) —CH═ and (2) —N═;

V is selected from (1) absent and (2) —C(O)—;

W is selected from (1) —C(O)—NH— and (2) —NH—C(O)—;

R 1 is selected from (1) aryl and (2) heteroaryl, wherein each of the aryl and heteroaryl is optionally substituted with 1-3 substituents independently selected from:

(a) halogen, and

(b) C 1-6 alkyl, optionally substituted with 1-4 halogens;

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

or alternatively, the two R 2 groups together with the carbon to which they are attached form a C 3-4 cycloalkyl, wherein the C 3-4 cycloalkyl is optionally substituted with C 1-6 alkyl;

R 3 is hydrogen, n is 1, and R 4 and R 5 together with the carbons to which they are attached form a C 3-4 cycloalkyl;

or alternatively, R 5 is hydrogen, n is 1, and R 3 and R 4 together with the carbons to which they are attached form a C 3-4 cycloalkyl;

or alternatively, R 5 is absent, n is 0, and R 3 and R 4 together with the carbons to which they are attached form a C 3-4 cycloalkyl;

or alternatively, R 4 is selected from (1) hydrogen and (2) C 1-6 alkyl optionally substituted with 1-3 halogens, n is 1, and R 3 and R 5 together with the carbons to which they are attached and the carbon to which R 4 is attached form a C 4-5 cycloalkyl;

R is selected from:

(1) hydrogen,

(2) aryl,

(3) C 1-6 alkyl, optionally substituted with 1-4 substituents halogens,

(4) C 3-6 cycloalkyl,

(5) —O—C 1-6 alkyl, optionally substituted with phenyl,

(6) —O—C 3-6 cycloalkyl,

(7) —O-heterocyclyl, and

(8) heteroaryl,

wherein each of the aryl of (2) and heteroaryl of (8) is optionally substituted with 1-3 substituents independently selected from:

(a) halogen,

(b) —OH,

(c) C 1-6 alkyl, optionally substituted with 1-4 substituents independently selected from (i) —OH and (ii) halogen,

(d) —O—C 1-6 alkyl, optionally substituted with 1-4 substituents independently selected from (i) —OH and (ii) halogen,

(e) C 3-6 cycloalkyl,

(f) —O—C 3-6 cycloalkyl, and

(g) —C(O)—O—C 1-6 alkyl.

2. The compound of claim 1 , or a pharmaceutically acceptable salt thereof, wherein R 1 is phenyl, optionally substituted with 1-3 halogens.

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

each occurrence of R 2 is independently selected from: (1) hydrogen and (2) C 1-4 alkyl;

or alternatively, the two R 2 groups together with the carbon to which they are attached form a C 3-4 cycloalkyl, wherein the C 3-4 cycloalkyl is optionally substituted with methyl or ethyl.

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

each occurrence of R 2 is independently selected from: (1) hydrogen, (2) methyl, and (3) ethyl;

or alternatively, the two R 2 groups together with the carbon to which they are attached form a cyclopropyl or cyclobutyl, wherein each of the cyclopropyl and cyclobutyl is optionally substituted with methyl.

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

R 3 is hydrogen, n is 1, and R 4 and R 5 together with the carbons to which they are attached form a cyclopropyl or cyclobutyl;

or alternatively, R 5 is hydrogen, n is 1, and R 3 and R 4 together with the carbons to which they are attached form a cyclopropyl or cyclobutyl;

or alternatively, R 5 is absent, n is 0, and R 3 and R 4 together with the carbons to which they are attached form a cyclopropyl or cyclobutyl;

or alternatively, R 4 is selected from (1) hydrogen, (2) methyl, and (3) ethyl, n is 1, and R 3 and R 5 together with the carbons to which they are attached and the carbon to which R 4 is attached form a cyclobutyl or cyclopentyl.

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

R 3 is hydrogen, n is 1, and R 4 and R 5 together with the carbons to which they are attached form a cyclobutyl;

or alternatively, R 5 is hydrogen, n is 1, and R 3 and R 4 together with the carbons to which they are attached form a cyclopropyl;

or alternatively, R 5 is absent, n is 0, and R 3 and R 4 together with the carbons to which they are attached form a cyclopropyl or cyclobutyl;

or alternatively, R 4 is selected from (1) hydrogen and (2) methyl, n is 1, and R 3 and R 5 together with the carbons to which they are attached and the carbon to which R 4 is attached form a cyclobutyl.

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

R is selected from:

(1) hydrogen,

(2) phenyl,

(3) C 1-4 alkyl, optionally substituted with 1-3 halogens,

(4) C 3-4 cycloalkyl,

(5) —O—C 1-4 alkyl, optionally substituted with phenyl,

(6) —O—C 3-4 cycloalkyl,

(7) —O-heterocyclyl, wherein the heterocyclyl is a 6-membered saturated monocyclic ring containing 1-3 hetero atoms independently selected from O, S, and N, and

(8) a 5- or 6-membered monocyclic heteroaryl containing 1-3 hetero atoms independently selected from O, S, and N,

wherein each of the phenyl of (2) and the heteroaryl of (8) is optionally substituted with 1-3 substituents independently selected from:

(a) halogen,

(b) —OH,

(c) C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(d) —O—C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(e) C 3-4 cycloalkyl,

(f) —O—C 3-4 cycloalkyl, and

(g) —C(O)—O—C 1-4 alkyl.

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

R is selected from:

(1) hydrogen,

(2) C 1-4 alkyl, optionally substituted with 1-3 halogens,

(3) C 3-4 cycloalkyl,

(4) —O—C 1-4 alkyl, optionally substituted with phenyl,

(5) —O-cyclopropyl,

(6) —O-heterocyclyl, wherein the heterocyclyl is a 6-membered saturated monocyclic ring containing 1-2 hetero atoms independently selected from O, S, and N, and

(7) a heteroaryl selected from (a) pyridinyl and (b) pyrimidinyl,

wherein the heteroaryl of (7) is optionally substituted with 1-3 substituents independently selected from:

(a) halogen,

(b) —OH,

(c) C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(d) —O—C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(e) cyclopropyl,

(f) —O-cyclopropyl, and

(g) —C(O)—O-methyl.

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

R is selected from:

(1) hydrogen,

(2) C 1-4 alkyl, optionally substituted with 1-3 halogens,

(3) cyclopropyl,

(4) —O—C 1-4 alkyl, optionally substituted with phenyl,

(5) —O-cyclopropyl,

(6) —O-heterocyclyl, wherein the heterocyclyl is tetrahydropyranyl, and

(7) a heteroaryl selected from (a) pyridinyl and (b) pyrimidinyl,

wherein the heteroaryl of (7) is optionally substituted with 1-3 substituents independently selected from:

(a) halogen,

(b) —OH,

(c) C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(d) —O—C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(e) cyclopropyl,

(f) —O-cyclopropyl, and

(g) —C(O)—O-methyl.

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

wherein:

m is 0 or 1; n is 0 or 1;

A is selected from (1) —CH═ and (2) —N═;

R a is selected from: (1) hydrogen and (2) C 1-4 alkyl;

R 1 is phenyl, optionally substituted with 1-3 halogens;

V is selected from (1) absent and (2) —C(O)—;

W is selected from (1) —C(O)—NH— and (2) —NH—C(O)—; and

R is selected from:

(1) hydrogen,

(2) C 1-4 alkyl, optionally substituted with 1-3 halogens,

(3) C 3-4 cycloalkyl,

(4) —O—C 1-4 alkyl, optionally substituted with phenyl,

(5) —O-cyclopropyl,

(6) —O-heterocyclyl, wherein the heterocyclyl is a 6-membered saturated monocyclic ring containing 1-2 hetero atoms independently selected from O, S, and N, and

(7) a heteroaryl selected from (a) pyridinyl and (b) pyrimidinyl,

wherein the heteroaryl of (7) is optionally substituted with 1-3 substituents independently selected from:

(a) halogen,

(b) —OH,

(c) C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(d) —O—C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(e) cyclopropyl,

(f) —O-cyclopropyl, and

(g) —C(O)—O-methyl.

11. The compound of claim 10 , or a pharmaceutically acceptable salt thereof, wherein:

R a is selected from: (1) hydrogen and (2) methyl;

R 1 is phenyl, optionally substituted with a halogen; and

R is selected from:

(1) hydrogen,

(2) C 1-4 alkyl, optionally substituted with 1-3 halogens,

(3) cyclopropyl,

(4) —O—C 1-4 alkyl, optionally substituted with phenyl,

(5) —O-cyclopropyl,

(6) —O-heterocyclyl, wherein the heterocyclyl is tetrahydropyranyl, and

(7) a heteroaryl selected from (a) pyridinyl and (b) pyrimidinyl,

wherein heteroaryl of (7) is optionally substituted with 1-3 substituents independently selected from:

(a) halogen,

(b) —OH,

(c) C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(d) —O—C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(e) cyclopropyl,

(f) —O-cyclopropyl, and

(g) —C(O)—O-methyl.

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

wherein:

m is 0 or 1;

A is selected from (1) —CH═ and (2) —N═;

R a is selected from: (1) hydrogen and (2) C 1-4 alkyl;

R 1 is phenyl, optionally substituted with 1-3 hydrogens;

V is selected from (1) absent and (2) —C(O)—;

W is selected from (1) —C(O)—NH— and (2) —NH—C(O)—; and

R is selected from:

(1) hydrogen,

(2) C 1-4 alkyl, optionally substituted with 1-3 halogens,

(3) C 3-4 cycloalkyl,

(4) —O—C 1-4 alkyl, optionally substituted with phenyl,

(5) —O-cyclopropyl,

(6) —O-heterocyclyl, wherein the heterocyclyl is a 6-membered saturated monocyclic ring containing 1-2 hetero atoms independently selected from O, S, and N, and

(7) a heteroaryl selected from (a) pyridinyl and (b) pyrimidinyl,

wherein the heteroaryl of (7) is optionally substituted with 1-3 substituents independently selected from:

(a) halogen,

(b) —OH,

(c) C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(d) —O—C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(e) cyclopropyl,

(f) —O-cyclopropyl, and

(g) —C(O)—O-methyl.

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

A is —CH═;

R a is hydrogen;

R 1 is phenyl, optionally substituted with a halogen; and

R is selected from:

(1) —O—C 1-4 alkyl,

(2) —O-cyclopropyl, and

(3) a heteroaryl selected from (a) pyridinyl and (b) pyrimidinyl, each of which is optionally substituted with a C 1-4 alkyl.

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

wherein:

m is 0 or 1;

A is selected from (1) —CH═ and (2) —N═;

R a is selected from: (1) hydrogen and (2) C 1-4 alkyl;

R b is selected from: (1) hydrogen and (2) C 1-4 alkyl;

R 1 is phenyl, optionally substituted with 1-3 halogens;

V is selected from (1) absent and (2) —C(O)—;

W is selected from (1) —C(O)—NH— and (2) —NH—C(O)—; and

R is selected from:

(1) hydrogen,

(2) C 3-4 cycloalkyl,

(3) —O—C 1-4 alkyl, optionally substituted with phenyl,

(4) —O-cyclopropyl,

(5) —O-heterocyclyl, wherein the heterocyclyl is a 6-membered saturated monocyclic ring containing 1-2 hetero atoms independently selected from O, S, and N, and

(6) a heteroaryl selected from (a) pyridinyl and (b) pyrimidinyl,

wherein the heteroaryl of (6) is optionally substituted with 1-3 substituents independently selected from:

(a) halogen,

(b) —OH,

(c) C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(d) —O—C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(e) cyclopropyl,

(f) —O-cyclopropyl, and

(g) —C(O)—O-methyl.

15. The compound of claim 14 , or a pharmaceutically acceptable salt thereof, wherein:

m is 0;

A is —N═;

R a is hydrogen;

R b is selected from: (1) hydrogen and (2) methyl;

R 1 is phenyl, optionally substituted with a halogen; and

R is selected from:

(1) hydrogen,

(2) cyclopropyl,

(3) —O—C 1-4 alkyl, optionally substituted with phenyl,

(4) —O-cyclopropyl, and

(5) a heteroaryl selected from (a) pyridinyl and (b) pyrimidinyl,

wherein the heteroaryl of (5) is optionally substituted with 1-3 substituents independently selected from:

(a) halogen,

(b) —OH, and

(c) C 1-4 alkyl.

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

wherein:

n is 0 or 1;

A is selected from (1) —CH═ and (2) —N═;

R 1 is phenyl, optionally substituted with 1-3 halogens;

R 2 is selected from: (1) hydrogen and (2) C 1-4 alkyl;

V is selected from (1) absent and (2) —C(O)—;

W is selected from (1) —C(O)—NH— and (2) —NH—C(O)—; and

R is selected from:

(1) hydrogen,

(2) C 1-4 alkyl, optionally substituted with 1-3 halogens,

(3) C 3-4 cycloalkyl,

(4) —O—C 1-4 alkyl, optionally substituted with phenyl,

(5) —O-cyclopropyl,

(6) —O-heterocyclyl, wherein the heterocyclyl is a 6-membered saturated monocyclic ring containing 1-2 hetero atoms independently selected from O, S, and N, and

(7) a heteroaryl selected from (a) pyridinyl and (b) pyrimidinyl,

wherein the heteroaryl of (7) is optionally substituted with 1-3 substituents independently selected from:

(a) halogen,

(b) —OH,

(c) C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(d) —O—C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(e) cyclopropyl,

(f) —O-cyclopropyl, and

(g) —C(O)—O-methyl.

17. The compound of claim 16 , or a pharmaceutically acceptable salt thereof, wherein:

R 1 is phenyl, optionally substituted with a halogen;

R 2 is selected from: (1) hydrogen, (2) methyl, and (e) ethyl; and

R is selected from:

(1) hydrogen,

(2) C 1-4 alkyl, optionally substituted with 1-3 halogens,

(3) cyclopropyl,

(4) —O—C 1-4 alkyl, optionally substituted with phenyl,

(5) —O-cyclopropyl,

(6) —O-heterocyclyl, wherein the heterocyclyl is tetrahydropyranyl, and

(7) a heteroaryl selected from (a) pyridinyl and (b) pyrimidinyl,

wherein heteroaryl of (7) is optionally substituted with 1-3 substituents independently selected from:

(a) halogen,

(b) —OH,

(c) C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(d) —O—C 1-4 alkyl, optionally substituted with 1-3 substituents independently selected from (i) —OH and (ii) halogen,

(e) cyclopropyl,

(f) —O-cyclopropyl, and

(g) —C(O)—O-methyl.

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

4-fluoro-N-(1-((1aR,7bS)-3-(2-methylpyrimidin-4-yl)-1a,2,3,7b-tetrahydro-1H-cyclopropa[c]quinolin-6-yl)cyclopropyl)benzamide,

1-(3-(cyclopropanecarbonyl)-1a,2,3,7b-tetrahydro-1H-cyclopropa[c]quinolin-6-yl)-N-(4-fluorophenyl)cyclobutanecarboxamide,

4-fluoro-N-(1-(3-(2-methylpyrimidin-4-yl)-1,2,2a,3,8,8a-hexahydrocyclobuta[b]quinolin-6-yl)cyclopropyl)benzamide,

methyl 6-(1-(4-fluorobenzamido)cyclopropyl)-1,2,2a, 7b-tetrahydro-3H-cyclobuta[b]indole-3-carboxylate,

4-fluoro-N-(1-(2-(2-methylpyrimidin-4-yl)-1,1a,2,6b-tetrahydrocyclopropa[b]indol-5-yl)cyclopropyl)benzamide,

4-fluoro-N-(1-(5-(2-methylpyrimidin-4-yl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridin-2-yl)cyclopropyl)benzamide,

N-(1-(5-(2-ethylpyrimidin-4-yl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridin-2-yl)cyclopropyl)-4-fluorobenzamide,

N-(1-(5-(2-cyclopropylpyrimidin-4-yl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridin-2-yl)cyclopropyl)-4-fluorobenzamide,

methyl 4-(2-(1-(4-fluorobenzamido)cyclopropyl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridin-5-yl)pyrimidine-2-carboxylate,

4-fluoro-N-(1-(5-(2-(2-hydroxypropan-2-yl)pyrimidin-4-yl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridin-2-yl)cyclopropyl)benzamide,

4-fluoro-N-(1-(5-(2-(hydroxymethyl)pyrimidin-4-yl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridin-2-yl)cyclopropyl)benzamide,

(6aR, 7aS)-cyclopropyl 2-(1-(4-fluorobenzamido)cyclopropyl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate,

tetrahydro-2H-pyran-4-yl (6aR, 7aS)-2-(1-(4-fluorobenzamido)cyclopropyl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate,

tetrahydro-2H-pyran-4-yl (6aS,7aR)-2-(1-(4-fluorobenzamido)cyclopropyl)-6,6a, 7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate,

tert-butyl 2-(1-(4-fluorobenzamido)ethyl)-6,6a, 7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate,

cyclopropyl (6aR,7aS)-2-((S)-1-(4-fluorobenzamido)ethyl)-6,6a, 7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate,

cyclopropyl (6aS,7aR)-2-((S)-1-(4-fluorobenzamido)ethyl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate,

cyclopropyl (6aS,7aR)-2-((R)-1-(4-fluorobenzamido)ethyl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate,

cyclopropyl (6aR,7aS)-2-((R)-1-(4-fluorobenzamido)ethyl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate,

4-fluoro-N-(2-(5-(2-methylpyrimidin-4-yl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridin-2-yl)propan-2-yl)benzamide,

cyclopropyl 2-(2-(4-fluorobenzamido)propan-2-yl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate,

2-(2-(4-fluorobenzamido)propan-2-yl)-5-(2,2,2-trifluoroacetyl)-6,6a, 7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridin-1-ium,

cyclopropyl 2-(1-(4-fluorobenzamido)propyl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate,

4-fluoro-N-(1-(5-(2-methylpyrimidin-4-yl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridin-2-yl)propyl)benzamide,

(6aR,7aS) or(6aS,7aR)-tetrahydro-2H-pyran-4-yl 2-(1-(4-fluorobenzamido)cyclopropyl)-6,6a, 7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate,

(6aS,7aR) or(6aR,7aS)-tetrahydro-2H-pyran-4-yl 2-(1-(4-fluorobenzamido)cyclopropyl)-6,6a, 7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate,

4-fluoro-N-(2-methyl-1-(5-(2-methylpyrimidin-4-yl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridin-2-yl)cyclopropyl)benzamide,

4-fluoro-N-(1-(3-methyl-1-(2-methylpyrimidin-4-yl)-1,2,3,4-tetrahydro-2,4-methano-1,5-naphthyridin-6-yl)cyclopropyl)benzamide,

benzyl 6-(1-(4-fluorobenzamido)cyclopropyl)-3,4-dihydro-2,4-methano-1,5-naphthyridine-1(2H)-carboxylate,

cyclopropyl 6-(1-(4-fluorobenzamido)cyclopropyl)-3,4-dihydro-2,4-methano-1,5-naphthyridine-1(2H)-carboxylate,

4-fluoro-N-(1-(1-(2-methylpyrimidin-4-yl)-1,2,3,4-tetrahydro-2,4-methano-1,5-naphthyridin-6-yl)cyclopropyl)benzamide,

tert-butyl (6aR,7aS)-2-(1-(4-fluorobenzamido)cyclopropyl)-6,6a, 7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate,

tert-butyl (6aS,7aR)-2-(1-(4-fluorobenzamido)cyclopropyl)-6,6a,7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate,

4-fluoro-N-(2-(6,6a, 7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridin-2-yl)propan-2-yl)benzamide, and

tert-butyl 2-(2-(4-fluorobenzamido)propan-2-yl)-6,6a, 7,7a-tetrahydro-5H-cyclopropa[c][1,5]naphthyridine-5-carboxylate;

or a pharmaceutically acceptable salt thereof.

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