A compound having structural Formula I: and pharmaceutically acceptable salts thereof wherein the central ring system is a saturated heterocyclic ring, and wherein: n1 and n2 can be individually either 0 or 1; a is -CH 2 -, -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, -CH 2 OCH 2 - or absent; wherein the -CH 2 - is optionally substituted with 1-2 of -F, and wherein the -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, or -CH 2 OCH 2 - is optionally substituted with 1-3 of -F; b is -CH 2 -, -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, -CH 2 OCH 2 - or absent; wherein the -CH 2 - is optionally substituted with 1-2 of -F, and wherein the -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, or -CH 2 OCH 2 - is optionally substituted with 1-3 of -F; c is -CH 2 -, -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, -CH 2 OCH 2 - or absent; wherein the -CH 2 - is optionally substituted with 1-2 of -F, and wherein the -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, or -CH 2 OCH 2 - is optionally substituted with 1-3 of -F; wherein at least one of a, b, or c is absent; R 5 and R 6 together on the same carbon form C 3-6 cycloalkyl optionally substituted with 1-3 of-F; Z 1 is: Z 2 is: one of W 1 and W 2 is N and the other is CH; R 1 and R 2 are each independently -H, -F, -Cl, -Br, cyclopropyl, -C 1 - 3 alkyl optionally substituted with 1-3 of -F, or -OC 1 - 3 alkyl optionally substituted with 1-3 of -F; one of R 3a and R 3b is -CN, tetrazolyl, or -S 2 C alkyl and the other is -H, -F, -Cl, -Br, -S-CH 3, -NH-CH 3, -O-cyclopropyl, -C 1 - 3 alkyl optionally substituted with 1-3 of -F, or -OC 1-3 alkyl optionally substituted with 1-3 of -F; one of R 4a and R 4b is CN, tetrazolyl, or -S 2 C alkyl and the other is -H, -F, -Cl, -Br, -S-CH 3, -NH-CH 3, -O-cyclopropyl, -C 1 - 3 alkyl optionally substituted with 1-3 of -F, or -OC 1-3 alkyl optionally substituted with 1-3 of -F; R 3c and R 4c are each independently -H, -C 1-6 alkyl or -C 1-6 cycloalkyl; R a, R aa, R b and R bb are each independently -H, -F, -Cl, -C 1 - 3 alkyl optionally substituted with 1 to 3 of -F, or -OC 1 - 3 alkyl optionally substituted with 1 to 3 of -F; R c and R d are each independently -H, -F, -Cl, -C 1-3 alkyl optionally substituted with 1 to 3 of-F, or -OC 1-3 alkyl optionally substituted with 1 to 3 of -F; and one of Y 1 or Y 2 is -CH -; and the other is -CH -; -C -; -S 2 -; -CH 2 - or absent; provided that where Y 1 or Y 2 is -C -; -S 2 - or absent, then the adjacent n1 or n2, respectively, is 0; and provided further that where n1 or n2 is 0, the adjacent Y 1 or Y 2 is -C -, -S 2 -or absent. n1 and n2 can be individually either 0 or 1; a is -CH 2 -, -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, -CH 2 OCH 2 - or absent; wherein the -CH 2 - is optionally substituted with 1-2 of -F, and wherein the -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, or -CH 2 OCH 2 - is optionally substituted with 1-3 of -F; b is -CH 2 -, -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, -CH 2 OCH 2 - or absent; wherein the -CH 2 - is optionally substituted with 1-2 of -F, and wherein the -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, or -CH 2 OCH 2 - is optionally substituted with 1-3 of -F; c is -CH 2 -, -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, -CH 2 OCH 2 - or absent; wherein the -CH 2 - is optionally substituted with 1-2 of -F, and wherein the -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, or -CH 2 OCH 2 - is optionally substituted with 1-3 of -F; wherein at least one of a, b, or c is absent; R 5 and R 6 together on the same carbon form C 3-6 cycloalkyl optionally substituted with 1-3 of-F; Z 1 is: Z 2 is: one of W 1 and W 2 is N and the other is CH; R 1 and R 2 are each independently -H, -F, -Cl, -Br, cyclopropyl, -C 1 - 3 alkyl optionally substituted with 1-3 of -F, or -OC 1 - 3 alkyl optionally substituted with 1-3 of -F; one of R 3a and R 3b is -CN, tetrazolyl, or -S 2 C alkyl and the other is -H, -F, -Cl, -Br, -S-CH 3, -NH-CH 3, -O-cyclopropyl, -C 1 - 3 alkyl optionally substituted with 1-3 of -F, or -OC 1-3 alkyl optionally substituted with 1-3 of -F; one of R 4a and R 4b is CN, tetrazolyl, or -S 2 C alkyl and the other is -H, -F, -Cl, -Br, -S-CH 3, -NH-CH 3, -O-cyclopropyl, -C 1 - 3 alkyl optionally substituted with 1-3 of -F, or -OC 1-3 alkyl optionally substituted with 1-3 of -F; R 3c and R 4c are each independently -H, -C 1-6 alkyl or -C 1-6 cycloalkyl; R a, R aa, R b and R bb are each independently -H, -F, -Cl, -C 1 - 3 alkyl optionally substituted with 1 to 3 of -F, or -OC 1 - 3 alkyl optionally substituted with 1 to 3 of -F; R c and R d are each independently -H, -F, -Cl, -C 1-3 alkyl optionally substituted with 1 to 3 of-F, or -OC 1-3 alkyl optionally substituted with 1 to 3 of -F; and one of Y 1 or Y 2 is -CH -; and the other is -CH -; -C -; -S 2 -; -CH 2 - or absent; provided that where Y 1 or Y 2 is -C -; -S 2 - or absent, then the adjacent n1 or n2, respectively, is 0; and provided further that where n1 or n2 is 0, the adjacent Y 1 or Y 2 is -C -, -S 2 -or absent.