Ionizable lipids and nanoparticle compositions thereof

An ionizable lipid represented by Formula (I):

• or a pharmaceutically acceptable salt thereof, wherein:
• R1 and R1′ are each independently optionally substituted linear or branched C1-3 alkylene;
• R2 and R2′ are each independently optionally substituted linear or branched C1-6 alkylene;
• R3 and R3′ are each independently optionally substituted linear or branched C1-6 alkyl;
• or alternatively, when R2 is optionally substituted branched C1-6 alkylene, R2 and R3, taken together with their intervening N atom, form a 4- to 8-membered heterocyclyl;
• or alternatively, when R2′ is optionally substituted branched C1-6 alkylene, R2′ and R3′ taken together with their intervening N atom, form a 4- to 8-membered heterocyclyl;
• R4 and R4′ are each independently —CRa, —C(Ra)2CRa, or —[C(Ra)2]2CRa;
• Ra, for each occurrence, is independently H or C1-3 alkyl;
• or alternatively, when R4 is —C(Ra)2CRa, or —[C(Ra)2]2CRa and when Ra is C1-3 alkyl, R3 and R4, taken together with their intervening N atom, form a 4- to 8-membered heterocyclyl;
• or alternatively, when R4′ is —C(Ra)2CRa, or —[C(Ra)2]2CRa and when Ra is C1-3 alkyl, R3′ and R4′, taken together with their intervening N atom, form a 4- to 8-membered heterocyclyl;
• R5 and R5′ are each independently C1-20 alkylene or C2-20 alkenylene;
• R6 and R6′, for each occurrence, are independently C1-20 alkylene, C3-20 cycloalkylene, or C2-20 alkenylene;
• and
• m and n are each independently an integer selected from 1, 2, 3, 4, and 5.