A compound of structural Formula I: or a pharmaceutically acceptable salt thereof, wherein: W is selected from the group consisting of CH and N; Z is selected from the group consisting of: and -(CH 2) 3 -NR 3 R 3a; R 1 is selected from the group consisting of -OH, -OC 1-6 alkyl and -N(R 5) 2; R 2 is selected from the group consisting of -C 1-2 perfluoroalkyl and -NH 2; R 3 is selected from the group consisting of: 1) -C 1-6 alkyl substituted with 1-3 of -F, 2) -COR 4 and 3) -SO 2 R 6; R 3a is selected from the group consisting of -H; -C 1-3 alkyl; C 3-6 cycloalkyl optionally mono-or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F; and -CH 2 -C 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F; R 4 is selected from the group consisting of: 1) -H, 2) -C 1-3 alkyl, 3) -OC 1-3 alkyl 4) -C 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F, 5) -CH 2 -C 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F, 6) -OC 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F, and 7) -N(R 5) 2; R 5 is independently selected at each occurrence from -H and -C 1-3 alkyl; R 6 is selected from the group consisting of -C 1-3 alkyl; -C 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F; and -CH 2 -C 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F; R 7 is selected from the group consisting of -H and -CH 3; R a and R b are independently selected at each occurrence from -F, -Cl and -C 1-3 alkyl optionally substituted with 1-3 of -F; and R c and R d are independently selected at each occurrence from -F, -Cl and -C 1-3 alkyl optionally substituted with 1-3 of -F. W is selected from the group consisting of CH and N; Z is selected from the group consisting of: and -(CH 2) 3 -NR 3 R 3a; R 1 is selected from the group consisting of -OH, -OC 1-6 alkyl and -N(R 5) 2; R 2 is selected from the group consisting of -C 1-2 perfluoroalkyl and -NH 2; R 3 is selected from the group consisting of: 1) -C 1-6 alkyl substituted with 1-3 of -F, 2) -COR 4 and 3) -SO 2 R 6; 1) -C 1-6 alkyl substituted with 1-3 of -F, 2) -COR 4 and 3) -SO 2 R 6; R 3a is selected from the group consisting of -H; -C 1-3 alkyl; C 3-6 cycloalkyl optionally mono-or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F; and -CH 2 -C 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F; R 4 is selected from the group consisting of: 1) -H, 2) -C 1-3 alkyl, 3) -OC 1-3 alkyl 4) -C 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F, 5) -CH 2 -C 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F, 6) -OC 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F, and 7) -N(R 5) 2; 1) -H, 2) -C 1-3 alkyl, 3) -OC 1-3 alkyl 4) -C 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F, 5) -CH 2 -C 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F, 6) -OC 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F, and 7) -N(R 5) 2; R 5 is independently selected at each occurrence from -H and -C 1-3 alkyl; R 6 is selected from the group consisting of -C 1-3 alkyl; -C 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F; and -CH 2 -C 3-6 cycloalkyl optionally mono- or di-substituted with one or more substituents selected from the group consisting of -CH 3 and -F; R 7 is selected from the group consisting of -H and -CH 3; R a and R b are independently selected at each occurrence from -F, -Cl and -C 1-3 alkyl optionally substituted with 1-3 of -F; and R c and R d are independently selected at each occurrence from -F, -Cl and -C 1-3 alkyl optionally substituted with 1-3 of -F.