A compound having a structure of Formula lb: or a pharmaceutically acceptable salt, tautomer or stereoisomer thereof, wherein: R 1a and R 1b are, at each occurrence, independently either (a) H or C 1 -C 12 alkyl, or (b) R 1a is H or C 1 -C 12 alkyl, and R 1b together with the carbon atom to which it is bound is taken together with an adjacent R 1b and the carbon atom to which it is bound to form a carbon-carbon double bond; R 2a and R 2b are, at each occurrence, independently either (a) H or C 1 -C 12 alkyl, or (b) R 2a is H or C 1 -C 12 alkyl, and R 2b together with the carbon atom to which it is bound is taken together with an adjacent R 2b and the carbon atom to which it is bound to form a carbon-carbon double bond; R 3a and R 3b are, at each occurrence, independently either (a) H or C 1 -C 12 alkyl, or (b) R 3a is H or C 1 -C 12 alkyl, and R 3b together with the carbon atom to which it is bound is taken together with an adjacent R 3b and the carbon atom to which it is bound to form a carbon-carbon double bond; R 4a and R 4b are, at each occurrence, independently either (a) H or C 1 -C 12 alkyl, or (b) R 4a is H or C 1 -C 12 alkyl, and R 4b together with the carbon atom to which it is bound is taken together with an adjacent R 4b and the carbon atom to which it is bound to form a carbon-carbon double bond; R 5 and R 6 are each independently methyl or cycloalkyl; R 7 is, at each occurrence, independently H or C 1 -C 12 alkyl; R 8 and R 9 are each independently unsubstituted C 1 -C 12 alkyl; or R 8 and R 9, together with the nitrogen atom to which they are attached, form a 5, 6 or 7-membered heterocyclic ring comprising one nitrogen atom; a and d are each independently an integer from 0 to 24; b and c are each independently an integer from 4 to 12; and e is 1 or 2. R 1a and R 1b are, at each occurrence, independently either (a) H or C 1 -C 12 alkyl, or (b) R 1a is H or C 1 -C 12 alkyl, and R 1b together with the carbon atom to which it is bound is taken together with an adjacent R 1b and the carbon atom to which it is bound to form a carbon-carbon double bond; R 2a and R 2b are, at each occurrence, independently either (a) H or C 1 -C 12 alkyl, or (b) R 2a is H or C 1 -C 12 alkyl, and R 2b together with the carbon atom to which it is bound is taken together with an adjacent R 2b and the carbon atom to which it is bound to form a carbon-carbon double bond; R 3a and R 3b are, at each occurrence, independently either (a) H or C 1 -C 12 alkyl, or (b) R 3a is H or C 1 -C 12 alkyl, and R 3b together with the carbon atom to which it is bound is taken together with an adjacent R 3b and the carbon atom to which it is bound to form a carbon-carbon double bond; R 4a and R 4b are, at each occurrence, independently either (a) H or C 1 -C 12 alkyl, or (b) R 4a is H or C 1 -C 12 alkyl, and R 4b together with the carbon atom to which it is bound is taken together with an adjacent R 4b and the carbon atom to which it is bound to form a carbon-carbon double bond; R 5 and R 6 are each independently methyl or cycloalkyl; R 7 is, at each occurrence, independently H or C 1 -C 12 alkyl; R 8 and R 9 are each independently unsubstituted C 1 -C 12 alkyl; or R 8 and R 9, together with the nitrogen atom to which they are attached, form a 5, 6 or 7-membered heterocyclic ring comprising one nitrogen atom; a and d are each independently an integer from 0 to 24; b and c are each independently an integer from 4 to 12; and e is 1 or 2.