Lipids and lipid nanoparticle formulations for delivery of nucleic acids

A compound having a structure of Formula I:

• or a pharmaceutically acceptable salt, tautomer, or stereoisomer thereof, wherein:
• L1 and L2 are each independently —O(C═O)— or —(C═O)O—;
• R1a and R1b are, at each occurrence, independently either (a) H or C1-C12 alkyl, or (b) R1a is H or C1-C12 alkyl, and R1b together with the carbon atom to which it is bound is taken together with an adjacent R1b and the carbon atom to which it is bound to form a carbon-carbon double bond;
• R2a and R2b are, at each occurrence, H;
• R3a and R3b are, at each occurrence, H;
• R4a and R4b are, at each occurrence, independently either (a) H or C1-C12 alkyl, or (b) R4a is H or C1-C12 alkyl, and R4b together with the carbon atom to which it is bound is taken together with an adjacent R4b and the carbon atom to which it is bound to form a carbon-carbon double bond;
• R5 and R6 are each independently methyl or cycloalkyl;
• R7 is, at each occurrence, independently H or C1-C12 alkyl;
• R8 and R9 are each independently unsubstituted C1-C12 alkyl;
• or R8 and R9, 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,
• provided that:
• R1a and R1b are not isopropyl when a is 6 or n-butyl when a is 8.