A compound having structural Formula I: or a pharmaceutically acceptable salt thereof wherein: Z is X is C(R 4) or N; R 1 is -H, halo, -OH, or -OC 1-3 alkyl; R 2 is -H, = O, -OH, -C 1 - 3 alkyl or -OC 1 - 3 alkyl; R 3a is -H, -C 3-4 cycloalkyl or -C 1-3 alkyl optionally substituted with -OCH 3 or 1 to 3 of-F; R3b is -H or -C 1-3 alkyl, or R3b is absent when the dashed bond is a double bond; or R 3a and R 3b are joined together with the carbon to which they are both attached to form cyclopropyl or cyclobutyl; R 4 is -H, halo, -CN, -C 3-6 cycloalkyl, -C OC 1-4 alkyl, -OC 1-4 alkyl, or -C 1-4 alkyl optionally substituted with OH or 1-3 of-F; R 5 is -H, halo, or -C 1 - 3 alkyl optionally substituted with -O-C 1-3 alkyl; R 6 is -H or -C 1-3 alkyl; R 7 is -H or -C 1-3 alkyl optionally substituted with -OH, -OCH 3 or 1 to 3 of-F, or R 7 is absent when n is zero; R 8 is -H or -C 1-3 alkyl, or R 8 is absent when n is zero; or R 7 and R 8 are joined together with the carbon to which they are both attached to form cyclopropyl or cyclobutyl; R 9 is -H, halo, -OH, -C 1-3 alkyl, -OC 1-3 alkyl or -CH 2 OH; R 10 is -H, or -C 1 - 3 alkyl optionally substituted with -OH, -OCH 3, or 1 to 3 of-F; R 11 is -H, or -C 1 - 3 alkyl optionally substituted with -OH, -OCH 3, or 1 to 3 of-F; or R 10 and R 11 are joined together to represent -CH 2 -CH 2 -, -CH 2 -N(CH 3)-CH 2 - or -CH 2 OCH 2 -; R 12 and R 13 are each independently -H, halo, -CN, -C 3-6 cycloalkyl, -C OC 1-4 alkyl, -OC 1-4 alkyl, or -C 1 - 4 alkyl optionally substituted with -OH or 1-3 of -F; m is zero where R3b is absent, or one where R3b is present; the partially dashed double bond (" --- ") represents a single or double bond wherein: (i) when m is one, then the dashed bond is a single bond; and (ii) when m is zero and R 2 is not = O, then the dashed bond is a double bond; and n is zero or one. Z is X is C(R 4) or N; R 1 is -H, halo, -OH, or -OC 1-3 alkyl; R 2 is -H, = O, -OH, -C 1 - 3 alkyl or -OC 1 - 3 alkyl; R 3a is -H, -C 3-4 cycloalkyl or -C 1-3 alkyl optionally substituted with -OCH 3 or 1 to 3 of-F; R3b is -H or -C 1-3 alkyl, or R3b is absent when the dashed bond is a double bond; or R 3a and R 3b are joined together with the carbon to which they are both attached to form cyclopropyl or cyclobutyl; R 4 is -H, halo, -CN, -C 3-6 cycloalkyl, -C OC 1-4 alkyl, -OC 1-4 alkyl, or -C 1-4 alkyl optionally substituted with OH or 1-3 of-F; R 5 is -H, halo, or -C 1 - 3 alkyl optionally substituted with -O-C 1-3 alkyl; R 6 is -H or -C 1-3 alkyl; R 7 is -H or -C 1-3 alkyl optionally substituted with -OH, -OCH 3 or 1 to 3 of-F, or R 7 is absent when n is zero; R 8 is -H or -C 1-3 alkyl, or R 8 is absent when n is zero; or R 7 and R 8 are joined together with the carbon to which they are both attached to form cyclopropyl or cyclobutyl; R 9 is -H, halo, -OH, -C 1-3 alkyl, -OC 1-3 alkyl or -CH 2 OH; R 10 is -H, or -C 1 - 3 alkyl optionally substituted with -OH, -OCH 3, or 1 to 3 of-F; R 11 is -H, or -C 1 - 3 alkyl optionally substituted with -OH, -OCH 3, or 1 to 3 of-F; or R 10 and R 11 are joined together to represent -CH 2 -CH 2 -, -CH 2 -N(CH 3)-CH 2 - or -CH 2 OCH 2 -; R 12 and R 13 are each independently -H, halo, -CN, -C 3-6 cycloalkyl, -C OC 1-4 alkyl, -OC 1-4 alkyl, or -C 1 - 4 alkyl optionally substituted with -OH or 1-3 of -F; m is zero where R3b is absent, or one where R3b is present; the partially dashed double bond (" --- ") represents a single or double bond wherein: (i) when m is one, then the dashed bond is a single bond; and (ii) when m is zero and R 2 is not = O, then the dashed bond is a double bond; and (i) when m is one, then the dashed bond is a single bond; and (ii) when m is zero and R 2 is not = O, then the dashed bond is a double bond; and n is zero or one.