Lipids and lipid nanoparticle formulations for delivery of nucleic acids

A compound having one of the following structures (IC) or (ID):

• or a pharmaceutically acceptable salt or stereoisomer thereof, wherein:
• one of L1 and L2 is —O (C═O)—, —(C═O)O—, —C(═O)—, —O—, —S(O)x—, —S—S—, —C(═O)S—, —SC(═O)—, —NRaC(═O)—, —C(═O)NRa—, NRaC(═O)NRa—, —OC(═O)NRa— or —NRaC(═O)O—, and the other of L1 and L2 is —O(C═O)—, —(C═O)O—, —C(═O)—, —O—, —S(O)x—, —S—S—, —C(═O)S—, SC(═O)—, —NRaC(═O)—, —C(═O)NRa—, , NRaC(═O)NRa—, —OC(═O)NRa— or —NRaC(═O)O— or a direct bond;
• Ra is H or C1-C12 alkyl;
• R1 and R2 are each independently branched C6-C24 alkyl or branched C6-C24 alkenyl;
• R3 is H, OR5, CN, —C(═O)OR4, —OC(═O)R4 or —NR5C(═O)R4;
• R4 is C1-C12 alkyl;
• R5 is H or C1-C6 alkyl;
• A is a 3 to 8-membered cycloalkyl or cycloalkylene ring;
• R6 is, at each occurrence, independently H, OH or C1-C24 alkyl;
• n is 3, 4, 5 or 6;
• y and z are each independently an integer ranging from 4 to 9;
• and
• x is 0, 1 or 2.