DNA-PK INHIBITORS

1 . A compound of Formula (I):

or a pharmaceutically acceptable salt thereof, wherein:

Ring A is

Ring B is

wherein Ring B is optionally substituted with up to 4 fluorine atoms, up to two OH,or up to two C 1-4 alkyl, which is optionally substituted with up to 3 fluorine atoms, up to two OH, or up to two —OC 1-2 alkyl groups;

Ring C is a cyclohexane or a cyclobutane ring;

X is —NH—, —O—, or —OC 1-4 alkyl-;

each of R 1 and R 2 is, independently, hydrogen, —C(O)NHR 4 , —C(O)OR 4 , —NHC(O)R 4 , —NHC(O)OR 4 , —NHC(O)NHR 4 , —NHS(O) 2 R 4 , —C 0-4 alkyl—NHR 4 , or —OR 4 , wherein R 1 and R 2 cannot simultaneously be hydrogen, and wherein R 1 and R 2 and the intervening carbon atom can form a dioxane or dioxolane ring;

R 3 is hydrogen, —C 1-4 alkyl, fluoro, chloro, -OC 1-2 alkyl, —C(O)H, —C(O)OH, —C(O)OC 1-2 alkyl, —CN, —C(O)NHC 1-2 alkyl, or —C(O)NH 2 , wherein each of said R 3 alkyl is optionally substituted with up to 3 fluorine atoms, up to two OH, or up to two OC 1-2 alkyl groups;

R 4 is hydrogen, C 1-4 alkyl, C 2-4 alkenyl, C 2-4 alkynyl, C 3-5 cycloalkyl, phenyl, a 5-10-membered monocyclic or bicyclic heteroaryl ring selected from pyrrole, imidazole, pyrazole, triazole, thiazole, isothiazole, oxazole, pyridine, pyrimidine, pyrimidinone, pyrazine, pyridazine, ef and quinoline, or a 4-10-membered monocyclic or bicyclic heterocyclyl ring selected from oxetane, tetrahydrofuran, tetrahydropyran, dihydroisoxazole, pyrimidine-2,4(1H,3H)-dione, dihydrofuropyrimidine, dihydropyranopyrimidine, dihydropyrrolopyrimidine, tetrahydropteridine, and tetrahydropyridopyrimidine, wherein each of said R 4 groups is optionally substituted with up to four Br, Cl, F, or C 1-4 alkyl, up to three CN, NO 2 , C 2-4 alkenyl, C 2-4 alkynyl, C 3-6 cycloalkyl, C 0-4 alkyl-C 3-5 cycloalkyl, C 0-4 alkyl-O—C 1-4 alkyl, C o4 alkyl-O-0 0-4 alkyl-C 3-5 cycloalkyl, C(O)OC 1-4 alkyl, C(O)OC 0-4 alkyl-C 3-5 cycloalkyl, C 0-4 alkyl-C(O)NH 2 , C(O)NHC 1-4 alkyl, C(O)N(C 1-4 alkyl) 2 , C(O)NH(C 0-4 alkyl-C 3-5 cycloalkyl), CH 2 OR 5 , C 0-4 alkyl-C(O)R 5 , C 0-4 alkyl-C(O)N(R 5 ) 2 , C 0-4 alkyl-C(O)OR 5 , C 0-4 alkyl—NHC(O)R 5 , C 0-4 alkyl-N(R 5 ) 2 , a heterocyclic ring system selected from oxetane, azetidine, tetrahydrofuran, dihydropyran, tetrahydropyran, morpholine, piperidine, pyrrolidine ef and piperazine, a heteroaryl ring system selected from furan, oxazole, oxadiazole, pyrrole, pyrazole, triazole, oxadiazole ef and tetrazole, or up to two OR 5 , wherein each of said optional R 4 substituents is optionally substituted with up to four fluorine atoms, up to two C 1-4 alkyl groups, up to two OH groups, up to two OC 1-4 alkyl groups, up to two SC 1-4 alkyl groups, a C(O)C 1-4 alkyl, a C(O)OC 14 alkyl, or a C(O)OC 0-4 alkyl-C 3-5 cycloalkyl; and

each R 5 is, independently, hydrogen, C 1-4 alkyl, a 5-6-membered heteroaryl selected from imidazole, triazole, thiazole, pyridine, and pyrimidine, or a 4-6-membered heterocyclyl selected from oxetane, tetrahydrofuran, and tetrahydropyran, and each R 5 group is optionally substituted with chloro, up to three fluorine atoms, up to two C 1-2 alkyl, CH 2 OH, CN, up to two OH, up to two OC 1-2 alkyl, a spirooxetane, pyrrolidine, or triazole, or two R 5 groups together with the intervening nitrogen atom form a morpholine ring, azetidine ring, pyrrolidine ring, piperidine ring, or piperazine ring.

2 . The compound of claim 1 , or a pharmaceutically acceptable salt thereof, wherein Ring C is cyclobutane.

3 . The compound of claim 2 , wherein the compound is of Formula (II):

or a pharmaceutically acceptable salt thereof.

4 - 9 . (canceled)

10 . The compound of claim 2 , or a pharmaceutically acceptable salt thereof, wherein X is —O— or —OC 1-4 alkyl-.

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

12 - 16 . (canceled)

17 . The compound of claim 1 , or a pharmaceutically acceptable salt thereof, wherein Ring C is cyclohexane.

18 . The compound of claim 17 , wherein the compound is of Formula (III):

or a pharmaceutically acceptable salt thereof.

19 . The compound of claim 18 , or a pharmaceutically acceptable salt thereof, wherein X is —NH.

20 . The compound of claim 19 , wherein the compound is of Formula (III-A):

or a pharmaceutically acceptable salt thereof.

21 . (canceled)

22 . The compound of claim 20 , or a pharmaceutically acceptable salt thereof, wherein R 2 is —C 0-4 alkyl—NHR 4 or —OR 4 .

23 - 24 . (canceled)

25 . The compound of claim 17 , wherein the compound is of Formula (III-B):

or a pharmaceutically acceptable salt thereof.

26 . (canceled)

27 . The compound of claim 25 , or a pharmaceutically acceptable salt thereof, wherein R 1 is —C 0-4 alkyl—NHR 4 or —OR 4 .

28 - 29 . (canceled)

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

31 . (canceled)

32 . The compound of claim 18 , or a pharmaceutically acceptable salt thereof, wherein X is —O—.

33 . The compound of claim 17 , wherein the compound is of Formula (III-C):

or a pharmaceutically acceptable salt thereof.

34 - 37 . (canceled)

38 . The compound of claim 17 , wherein the compound is of Formula (III-D):

or a pharmaceutically acceptable salt thereof.

39 . (canceled)

40 . The compound of claim 38 , or a pharmaceutically acceptable salt thereof, wherein R 1 is —C 0-4 alkyl—NHR 4 or —OR 4 .

41 - 43 . (canceled)

44 . The compound of claim 32 , or a pharmaceutically acceptable salt thereof, wherein

45 - 60 . (canceled)

61 . A pharmaceutical composition comprising a compound of claim 1 , or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable excipient.

62 - 63 . (canceled)

64 . A method of treating cancer or inhibiting cancer cell growth in a patient comprising administering to said patient an effective amount of the compound of claim 1 , or a pharmaceutically acceptable salt thereof, or a pharmaceutical composition comprising said compound or pharmaceutically acceptable salt thereof, either alone or in combination with one or more additional therapeutic agent.