A compound of structural Formula I: or a pharmaceutically acceptable salt thereof, wherein: R 1 is -C 1-6 alkyl; R 2 is -C 1-6 alkyl; or R 1 and R 2 are joined together with the carbon to which they are both attached to form spiro-C 3-6 cycloalkyl; R 3 is: (a) -C 1-10 alkyl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -CN, -CF 3, -OR 5, -SR c, -NR 6 R 7, -C 3-6 cycloalkyl or spiro-C 3-6 cycloalkyl, (b) -CH 2 -phenyl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR 6 R 7 or -C 1-3 alkyl, (c) -C 3-8 cycloalkyl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR 6 R 7 or -C 1-3 alkyl, (d) aryl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR 6 R 7 or -C 1-3 alkyl, (e) -C 1-5 alkyl-X-C 1-5 alkyl wherein X is O, S or NH, (f) heteroaryl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR6R7 or -C 1-3 alkyl, or (g) a heterocyclic ring unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR 6 R 7 or -C 1-3 alkyl; R is -H, -CF 3, -C 1-3 alkyl or -C 3-6 cycloalkyl; R c is -H, -CF 3 or -C 3-6 cycloalkyl; R 4 is -H, -CF 3, -C 1-3 alkyl or -C 3-6 cycloalkyl; R 5 is -H, -CF 3 or -C 3-6 cycloalkyl; R 6 is ―H, -C 1-3 alkyl or -C 3-6 cycloalkyl; R 7 is ―H, -C 1-3 alkyl or -C 3-6 cycloalkyl. R 8 is -H or -C 1-3 alkyl; R 9 is -H, -C 1-6 alkyl or -C 1-6 alkyl substituted with 1 to 3 of F; R 10 is -H, -C 1-6 alkyl or -C 1-6 alkyl substituted with 1 to 3 of F; or R 9 and R 10 are joined together with the carbon to which they are both attached to form spiro-C 3-6 cycloalkyl; R a is halo, -CN, -C 1-6 alkyl, -C 1-6 alkyl substituted with 1 to 3 of F, -OC 1-6 alkyl or -OC 1-6 alkyl substituted with 1 to 3 of F; and Rb is ―H, halo, -CN, -C 1-6 alkyl, -C 1-6 alkyl substituted with 1 to 3 of F, -OC 1-6 alkyl or -OC 1-6 alkyl substituted with 1 to 3 of F. R 1 is -C 1-6 alkyl; R 2 is -C 1-6 alkyl; or R 1 and R 2 are joined together with the carbon to which they are both attached to form spiro-C 3-6 cycloalkyl; R 3 is: (a) -C 1-10 alkyl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -CN, -CF 3, -OR 5, -SR c, -NR 6 R 7, -C 3-6 cycloalkyl or spiro-C 3-6 cycloalkyl, (b) -CH 2 -phenyl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR 6 R 7 or -C 1-3 alkyl, (c) -C 3-8 cycloalkyl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR 6 R 7 or -C 1-3 alkyl, (d) aryl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR 6 R 7 or -C 1-3 alkyl, (e) -C 1-5 alkyl-X-C 1-5 alkyl wherein X is O, S or NH, (f) heteroaryl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR6R7 or -C 1-3 alkyl, or (g) a heterocyclic ring unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR 6 R 7 or -C 1-3 alkyl; (a) -C 1-10 alkyl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -CN, -CF 3, -OR 5, -SR c, -NR 6 R 7, -C 3-6 cycloalkyl or spiro-C 3-6 cycloalkyl, (b) -CH 2 -phenyl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR 6 R 7 or -C 1-3 alkyl, (c) -C 3-8 cycloalkyl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR 6 R 7 or -C 1-3 alkyl, (d) aryl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR 6 R 7 or -C 1-3 alkyl, (e) -C 1-5 alkyl-X-C 1-5 alkyl wherein X is O, S or NH, (f) heteroaryl unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR6R7 or -C 1-3 alkyl, or (g) a heterocyclic ring unsubstituted or substituted with one, two or three of fluoro, chloro, bromo, -OR 4, -SR, -NR 6 R 7 or -C 1-3 alkyl; R is -H, -CF 3, -C 1-3 alkyl or -C 3-6 cycloalkyl; R c is -H, -CF 3 or -C 3-6 cycloalkyl; R 4 is -H, -CF 3, -C 1-3 alkyl or -C 3-6 cycloalkyl; R 5 is -H, -CF 3 or -C 3-6 cycloalkyl; R 6 is ―H, -C 1-3 alkyl or -C 3-6 cycloalkyl; R 7 is ―H, -C 1-3 alkyl or -C 3-6 cycloalkyl. R 8 is -H or -C 1-3 alkyl; R 9 is -H, -C 1-6 alkyl or -C 1-6 alkyl substituted with 1 to 3 of F; R 10 is -H, -C 1-6 alkyl or -C 1-6 alkyl substituted with 1 to 3 of F; or R 9 and R 10 are joined together with the carbon to which they are both attached to form spiro-C 3-6 cycloalkyl; R a is halo, -CN, -C 1-6 alkyl, -C 1-6 alkyl substituted with 1 to 3 of F, -OC 1-6 alkyl or -OC 1-6 alkyl substituted with 1 to 3 of F; and Rb is ―H, halo, -CN, -C 1-6 alkyl, -C 1-6 alkyl substituted with 1 to 3 of F, -OC 1-6 alkyl or -OC 1-6 alkyl substituted with 1 to 3 of F.