What are described are compounds of formulas ?, HI, IV, and V. The compound of formula II consists of a compound in which R1 and R2 are both a linear alkyl consisting of 1 to 12 carbons, an alkenyl or alkynyl consisting of 2 to 12 carbons； L1 and L2 both consist of a linear alkylene or alkenylene consisting of 5 to 18 carbons, or forming a heterocycle with N； X is S； L3 consists of a bond or a linear alkylene consisting of 1 to 6 carbons, or farming a heterocycle with N； R3 consists of a linear or branched alkylene consisting of 1 to 6 carbons； and R4 and R5 are the same or different, each consisting of hydrogen or a linear or branched alkyl consisting of 1 to 6 carbons. The compound of formulas HI and IV consists of a compound in which R1 consists of a branched alkyl with 12 to 20 carbons； R2 consists of a linear alkyl with 5 to 10 carbons or a branched alkyl with 12 to 20 carbons； L1 and L2 each consists of a bond or a linear alkyl having 1 to 3 carbon atoms； X consists of S or O； L3 consists of a bond or a lower alkyl； R3 consists of a lower alkyl； and R4 and R5 are the same or different, each consisting of a lower alkyl. The compound of formula V consists of a compound in which R1 consists of a linear or branched alkyl consisting of 1-18 carbons, an alkenyl or alkynyl consisting of 2 to 12 carbons, or a cholesteryl； R2 consists of a 606338680v1 linear or branched alkyl or an alkenyl consisting of 1 to 18 carbons； L1 consists of a linear alkyl consisting of 5 to 9 carbons or, when R1 consists of a cholesteryl then L1 consists of a linear alkylene or alkenyl consisting of 3 to 4 carbons； X1 consists of -0-(CO) or -(CO)-0； X2 consists of S or O； La consists of a bond or a linear alkylene of 1 to 6 carbons； R3 consists of a linear or branched alkylene with 1 to 6 carbons； and R4 and R5 are the same or different, each consisting of a linear or branched alkyl of 1 to 6 carbons. The compound of formulas II, III, IV, and V may comprise a pharmaceutically acceptable salt
