Purine derivatives

1. A compound of formula (IIIa):

wherein

R 1 is hydrogen, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl, 4-6 membered heterocycloalkyl, or 4-6 membered heteroaryl, wherein the C 1 -C 6 alkyl is optionally substituted by one, two or three substituents selected from the group consisting of halogen, hydroxy, and C 1 -C 3 alkoxy, further wherein the C 3 -C 6 cycloalkyl, the 4-6 membered heterocycloalkyl, and the 4-6 membered heteroaryl are each independently optionally substituted by one, two or three substituents selected from the group consisting of C 1 -C 3 alkyl, hydroxy, and C 1 -C 3 alkoxy;

R 2 and R 5 are each independently hydrogen, halogen, cyano, difluoromethyl, trifluoromethyl, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 1 -C 6 alkoxy, —N(R 10 )(R 11 ), C 3 -C 5 cycloalkyl, or 4-6 membered heterocycloalkyl, wherein the C 1 -C 6 alkyl is optionally substituted by one, two or three substituents selected from the group consisting of halogen, hydroxy, C 1 -C 6 alkoxy, and —N(R 12 )(R 13 ),

provided that at least one of R 2 or R 5 is hydrogen;

R 3 is hydrogen, halogen, C 1 -C 6 alkyl, C 2 -C 6 alkynyl, C 1 -C 6 alkoxy, C 3 -C 7 cycloalkyl, or 3-7 membered heterocycloalkyl, wherein the C 1 -C 6 alkyl and the C 1 -C 6 alkoxy are each optionally substituted by one, two or three R 14 groups, and further wherein the C 3 -C 7 cycloalkyl and the 3-7 membered heterocycloalkyl are each optionally substituted by one, two or three R 15 groups;

R 6 and R 8 are each independently hydrogen, halogen, cyano, hydroxy, difluoromethyl, trifluoromethyl, C 1 -C 3 alkyl, C 1 -C 3 alkoxy, or C 3 -C 5 cycloalkyl, wherein the C 1 -C 3 alkyl is optionally substituted by hydroxy, difluoromethyl, trifluoromethyl, C 1 -C 3 alkoxy, or C 3 -C 5 cycloalkyl;

R 7 is

G is —NR 18 —;

R 10 and R 11 are each independently hydrogen or C 1 -C 6 alkyl; or R 10 and R 11 together with the nitrogen to which they are attached, may combine to form a 4-7 membered heterocycloalkyl ring, when R 10 and R 1l are each C 1 -C 3 alkyl, wherein the 4-7 membered heterocycloalkyl ring formed is optionally substituted by one, two, three or four R 15 groups;

R 12 and R 13 are each independently hydrogen or C 1 -C 3 alkyl;

each R 14 is independently halogen, cyano, C 1 -C 3 alkyl, hydroxy, C 1 -C 6 alkoxy,—N(R 19 )(R 20 ), —CON(R 21 )(R 22 ), or 3-7 membered heterocycloalkyl, wherein the 3-7 membered heterocycloalkyl is optionally substituted by one, two, three or four R 15 groups;

each R 15 is independently halogen, C 1 -C 3 alkyl, hydroxy, C 1 -C 6 alkoxy, —NH 2 , —NHCH 3 , or —N(CH 3 ) 2 ;

R 16 and R 17 are each independently hydrogen or C 1 -C 6 alkyl, wherein the C 1 -C 6 alkyl is optionally substituted by —N(R 23 )(R 24 ),

provided that R 16 and R 17 may form C 3 -C 5 cycloakyl ring;

R 18 is hydrogen or C 1 -C 3 alkyl;

each R 19 , R 20 , R 21 , R 22 , R 23 , and R 24 is independently hydrogen or C 1 -C 3 alkyl;

n is 0, 1, or 2; and

p is 0, 1, or 2; or

a pharmaceutically acceptable salt thereof.

2. The compound or salt of claim 1 , wherein n is 0.

3. The compound or salt of claim 1 , wherein R 6 and R 8 are each independently hydrogen, halogen, C 1 -C 3 alkyl, or C 1 -C 3 alkoxy.

4. The compound or salt of claim 1 , wherein R 6 is hydrogen, fluorine, methyl, or methoxy.

5. The compound or salt of claim 1 , wherein R 6 is fluorine.

6. The compound or salt of claim 1 , wherein R 8 is hydrogen, fluorine, or methyl.

7. The compound or salt of claim 1 , having formula (IIIb):

8. A compound, which is

or a pharmaceutically acceptable salt thereof.

9. A pharmaceutical composition comprising a compound of claim 1 , or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier or diluent.

10. A pharmaceutical composition comprising a compound, which is

or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier or diluent.

11. A method of treating lung cancer in a mammal comprising administering to the mammal an amount of a compound of claim 1 , or a pharmaceutically acceptable salt thereof, that is effective in treating lung cancer.