Cyclin dependent kinase inhibitors

1. A compound of Formula (IX):

or a pharmaceutically acceptable salt thereof, wherein:

R 1 is H, F, Cl, CN, C 1 -C 2 alkyl or C 1 -C 2 fluoroalkyl, where each said C 1 -C 2 alkyl and C 1 -C 2 fluoroalkyl is optionally substituted by R 20 ;

R 2 is H, C 1 -C 5 alkyl, C 1 -C 5 fluoroalkyl, C 3 -C 8 cycloalkyl or 3-6 membered heterocyclyl, where each said C 1 -C 5 alkyl and C 1 -C 5 fluoroalkyl is optionally substituted by R 20 and each said C 3 -C 8 cycloalkyl and 3-6 membered heterocyclyl is optionally substituted by R 21 ; and

R 4 is H, C 1 -C 4 alkyl, C 1 -C 4 fluoroalkyl, C 1 -C 4 alkoxy or C 1 -C 4 fluoroalkoxy, where each said C 1 -C 4 alkyl, C 1 -C 4 fluoroalkyl, C 1 -C 4 alkoxy and C 1 -C 4 fluoroalkoxy is optionally substituted by R 20 ; or

R 6 is H, F, Cl, CN, CH 3 , CH 2 F, CHF 2 or CF 3 ;

R 7 and R 8 are independently H, F, Cl, CN, C 1 -C 2 alkyl, C 1 -C 2 fluoroalkyl, C 1 -C 2 alkoxy or C 1 -C 2 fluoroalkoxy, where each said C 1 -C 2 alkyl, C 1 -C 2 fluoroalkyl, C 1 -C 2 alkoxy and C 1 -C 2 fluoroalkoxy is optionally substituted by R 20 ;

R 9 is H, OH, NH 2 , NHCH 3 or N(CH 3 ) 2 ;

each R 10 is independently F, CN, C 1 -C 2 alkyl or C 1 -C 2 fluoroalkyl, where each said C 1 -C 2 alkyl and C 1 -C 2 fluoroalkyl is optionally substituted by R 20 ;

R 11 is H, C 1 -C 4 alkyl, C 1 -C 4 fluoroalkyl, SO 2 R 14 , SO 2 NR 15 R 16 , COR 17 , COOR 17 or CONR 18 R 19 ;

R 14 is C 1 -C 4 alkyl or C 1 -C 4 fluoroalkyl;

each R 15 and R 16 is independently H or CH 3 ;

R 17 is C 1 -C 4 alkyl or C 1 -C 4 fluoroalkyl, where each said C 1 -C 4 alkyl and C 1 -C 4 fluoroalkyl is optionally substituted by R 20 ;

each R 18 and R 19 is independently H, C 1 -C 4 alkyl or C 1 -C 4 fluoroalkyl, where each said C 1 -C 4 alkyl and C 1 -C 4 fluoroalkyl is optionally substituted by R 20 ;

each R 20 is independently OH, C 1 -C 2 alkoxy, C 1 -C 2 fluoroalkoxy, CN or NR 22 R 23 ;

each R 21 is independently F, OH, CN, NR 22 R 23 , C 1 -C 4 alkyl, C 1 -C 4 fluoroalkyl, C 1 -C 4 alkoxy or C 1 -C 4 fluoroalkoxy, where each said C 1 -C 4 alkyl, C 1 -C 4 fluoroalkyl, C 1 -C 4 alkoxy and C 1 -C 4 fluoroalkoxy is optionally further substituted by OH, NH 2 , NHCH 3 or N(CH 3 ) 2 ;

each R 22 and R 23 is independently H, C 1 -C 2 alkyl or C 1 -C 2 fluoroalkyl; or

R 22 and R 23 may be taken together with the nitrogen atom to which they are attached to form an azetidinyl ring, which is optionally substituted by F or OH; and

n is 0, 1, 2, 3 or 4.

2. (3R,4R)-4-[(5-chloro-4-{4-fluoro-2-[(1R)-1-hydroxyethyl]-1-(propan-2-yl)-1H-benzimidazol-6-yl}pyrimidin-2-yl)amino]-1-(methanesulfonyl)piperidin-3-ol, or a pharmaceutically acceptable salt thereof.

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

4. A pharmaceutical composition comprising the compound of claim 2 , or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier or excipient.

5. A method for the treatment of cancer in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of the compound of claim 1 , or a pharmaceutically acceptable salt thereof.

6. A method for the treatment of cancer in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of the compound of claim 2 , or a pharmaceutically acceptable salt thereof.

7. A method for the treatment of cancer in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of 1,5-anhydro-3-({5-chloro-4-[4-fluoro-2-(2-hydroxypropan-2-yl)-1-(propan-2-yl)-1H-benzimidazol-6-yl]pyrimidin-2-yl}amino)-2,3-dideoxy-D-threo-pentitol, or a pharmaceutically acceptable salt thereof, wherein the cancer is selected from the group consisting of breast cancer, ovarian cancer, bladder cancer, uterine cancer, prostate cancer, lung cancer, esophageal cancer, head and neck cancer, colorectal cancer, kidney cancer, liver cancer, pancreatic cancer, stomach cancer and thyroid cancer.

8. The method of claim 7 , wherein the cancer is breast cancer.

9. The method of claim 8 , wherein the breast cancer is hormone receptor (HR)-positive, human epidermal growth factor 2 (HER2)-negative breast cancer.

10. The method of claim 9 , wherein the breast cancer is HR-positive, HER2-negative advanced or metastatic breast cancer.

11. The method of claim 10 , further comprising administering to the subject an additional anti-cancer agent.

12. The method of claim 11 , wherein the additional anti-cancer agent is an endocrine agent selected from the group consisting of an aromatase inhibitor, a selective estrogen receptor downregulator (SERD), and a selective estrogen receptor modulator (SERM).

13. The method of claim 12 , wherein the endocrine agent is letrozole or fulvestrant.

14. The method of claim 10 , wherein the 1,5-anhydro-3-({5-chloro-4-[4-fluoro-2-(2-hydroxypropan-2-yl)-1-(propan-2-yl)-1H-benzimidazol-6-yl]pyrimidin-2-yl}amino)-2,3-dideoxy-D-threo-pentitol, or a pharmaceutically acceptable salt thereof, is administered as a first line therapy.

15. The method of claim 14 , further comprising administering to the subject an additional anti-cancer agent, wherein the additional anti-cancer agent is letrozole.

16. The method of claim 10 , wherein the 1,5-anhydro-3-({5-chloro-4-[4-fluoro-2-(2-hydroxypropan-2-yl)-1-(propan-2-yl)-1H-benzimidazol-6-yl]pyrimidin-2-yl}amino)-2,3-dideoxy-D-threo-pentitol, or a pharmaceutically acceptable salt thereof, is administered as a second or later line therapy.

17. The method of claim 16 , further comprising administering to the subject an additional anti-cancer agent, wherein the additional anti-cancer agent is fulvestrant.

18. The method of claim 7 , wherein the cancer is lung cancer.

19. The method of claim 18 , wherein the lung cancer is non-small cell lung cancer (NSCLC).

20. The method of claim 7 , wherein the cancer is colorectal cancer.

21. The method of claim 7 , wherein the cancer is prostate cancer.