Compound as cationic lipid

1. A compound represented by formula (I):

wherein R 1 is a hydrogen atom, C1-C3 alkyl, hydroxyC2-C4 alkyl, di-C1-C3 alkylaminoC2-C4 alkyl, formula (A):

wherein R 2 and R 3 are, the same or different, a hydrogen atom or C1-C3 alkyl, or R 2 and R 3 , together with the nitrogen atom to which they are attached, may form a C2-C6 nitrogen-containing heterocycle, and n 3 is an integer from 2 to 6, or

formula (B):

wherein R 4 and R 5 are, the same or different, a hydrogen atom or C1-C3 alkyl, or R 4 and R 5 , together with the nitrogen atom to which they are attached, may form a C2-C6 nitrogen-containing heterocycle, and n 4 is an integer from 1 to 6;

n 1 is an integer from 0 to 4; n 2 is an integer from 1 to 4, provided that the case where n 1 is 0 and n 2 is 1 is excluded;

Z 1 is, independently for each carbon atom bonded thereto, a hydrogen atom or C1-C3 alkyl;

Z 2 is, independently for each carbon atom bonded thereto, a hydrogen atom or C1-C3 alkyl;

A 1 and A 2 are, the same or different, linear or branched C8-C20 alkylene or C8-C20 alkenylene, or C6-C18 alkyleneoxyC1-C3 alkylene or C6-C18 alkenyleneoxyC1-C3 alkylene;

M 1 and M 2 are, the same or different, selected from the group consisting of —OC(O)—, —C(O)O—, —SC(O)—, —C(O)S—, —OC(S)—, —C(S)O—, —SS—, —C(R 6 )═N—, —N═C(R 6 )—, —C(R 6 )═N—O—, —O—N═C(R 6 )—, —N(R 6 )C(O)—, —C(O)N(R 6 )—, —N(R 6 )C(S)—, —C(S)N(R 6 )—, —N(R 6 )C(O)N(R 7 )—, —N(R 6 )C(O)O—, —OC(O)N(R 6 )—, and —OC(O)O—;

R 6 and R 7 are, the same or different, a hydrogen atom or C1-C4 alkyl; and

B 1 and B 2 are, the same or different, linear or branched C1-C16 alkyl or C2-C16 alkenyl or a pharmaceutically acceptable salt thereof.

2. The compound according to claim 1 or a pharmaceutically acceptable salt thereof, wherein M 1 and M 2 are, the same or different, selected from the group consisting of —OC(O)—, —C(O)O—, —N(R 6 )C(O)—, and —C(O)N(R 6 )—.

3. The compound according to claim 2 or a pharmaceutically acceptable salt thereof, wherein M 1 and M 2 are, the same or different, —OC(O)— or —C(O)O—.

4. The compound according to claim 1 or a pharmaceutically acceptable salt thereof, wherein A 1 and A 2 are, the same or different, linear or branched C8-C20 alkylene or C8-C20 alkenylene.

5. The compound according to claim 1 or a pharmaceutically acceptable salt thereof, wherein B 1 -M 1 -A 1 - and B 2 -M 2 -A 2 - are the same.

6. The compound according to claim 1 or a pharmaceutically acceptable salt thereof, wherein R 1 is C1-C3 alkyl.

7. The compound according to claim 1 or a pharmaceutically acceptable salt thereof, wherein n 1 is 1, and n 2 is an integer from 1 to 3.

8. The compound according to claim 1 or a pharmaceutically acceptable salt thereof, wherein both of n 1 and n 2 are 1.

9. A composition comprising the compound according to claim 1 or a pharmaceutically acceptable salt thereof and a nucleic acid.

10. The composition according to claim 9 , further comprising a neutral lipid and/or a polymer.

11. The composition according to claim 9 , wherein the nucleic acid is a nucleic acid having a silencing effect on a target gene through the use of RNA interference (RNAi).

12. The composition according to claim 11 , wherein the target gene is a gene expressed in the liver, the lung, the kidney, the digestive tract, the central nervous system, or the spleen.

13. The composition according to claim 9 , wherein the composition is for intravenous administration.

14. A medicament comprising the composition according to claim 9 .

15. A method for therapeutically treating a disease related to the liver, the lung, the kidney, the digestive tract, the central nervous system, or the spleen, comprising administering the composition according to claim 9 to a patient in need thereof.