Cationic lipid

A cationic lipid represented by formula (I):

• (wherein:
• R1 and R2 are, the same or different, each linear or branched alkyl, alkenyl or alkynyl having 12 to 24 carbon atoms, or R1 and R2 are combined together to form dialkylmethylene, dialkenylmethylene, dialkynylmethylene or alkylalkenylmethylene,
• X1 and X2 are hydrogen atoms, or are combined together to form a single bond or alkylene,
• X3 is absent or is alkyl having 1 to 6 carbon atoms, or alkenyl having 3 to 6 carbon atoms,
• when X3 is absent,
• Y is absent, a and b are 0, L3 is a single bond, R3 is alkyl having 1 to 6 carbon atoms, alkenyl having 3 to 6 carbon atoms, pyrrolidin-3-yl, piperidin-3-yl, piperidin-4-yl, or alkyl having 1 to 6 carbon atoms or alkenyl having 3 to 6 carbon atoms substituted with 1 to 3 substituent(s), which is(are), the same or different, amino, monoalkylamino, dialkylamino, trialkylammonio, hydroxy, alkoxy, carbamoyl, monoalkylcarbamoyl, dialkylcarbamoyl, pyrrolidinyl, piperidyl or morpholinyl, and L1 and L2 are —O—,
• Y is absent, a and b are, the same or different, 0 to 3, and are not 0 at the same time, L3 is a single bond, R3 is alkyl having 1 to 6 carbon atoms, alkenyl having 3 to 6 carbon atoms, pyrrolidin-3-yl, piperidin-3-yl, piperidin-4-yl, or alkyl having 1 to 6 carbon atoms or alkenyl having 3 to 6 carbon atoms substituted with 1 to 3 substituent(s), which is(are), the same or different, amino, monoalkylamino, dialkylamino, trialkylammonio, hydroxy, alkoxy, carbamoyl, monoalkylcarbamoyl, dialkylcarbamoyl, pyrrolidinyl, piperidyl or morpholinyl, L1 and L2 are, the same or different, —O—, —CO—O— or —O—CO—,
• Y is absent, a and b are, the same or different, 0 to 3, L3 is a single bond, R3 is a hydrogen atom, and L1 and L2 are, the same or different, —O—, —CO—O— or —O—CO—, or
• Y is absent, a and b are, the same or different, 0 to 3, L3 is —CO— or —CO—O—, R3 is pyrrolidin-2-yl, pyrrolidin-3-yl, piperidin-2-yl, piperidin-3-yl, piperidin-4-yl, morpholin-2-yl, morpholin-3-yl, or alkyl having 1 to 6 carbon atoms or alkenyl having 3 to 6 carbon atoms substituted with 1 to 3 substituent(s), which is(are), the same or different, amino, monoalkylamino, dialkylamino, trialkylammonio, hydroxy, alkoxy, carbamoyl, monoalkylcarbamoyl, dialkylcarbamoyl, pyrrolidinyl, piperidyl or morpholinyl, wherein at least one of the substituents is amino, monoalkylamino, dialkylamino, trialkylammonio, pyrrolidinyl, piperidyl or morpholinyl, and L1 and L2 are, the same or different, —O—, —CO—O— or —O—CO—, and
• when X3 is alkyl having 1 to 6 carbon atoms or alkenyl having 3 to 6 carbon atoms,
• Y is a pharmaceutically acceptable anion, a and b are, the same or different, 0 to 3, L3 is a single bond, R3 is alkyl having 1 to 6 carbon atoms, alkenyl having 3 to 6 carbon atoms, pyrrolidin-3-yl, pyrrolidin-3-yl, piperidin-3-yl, piperidin-4-yl, or alkyl having 1 to 6 carbon atoms or alkenyl having 3 to 6 carbon atoms substituted with 1 to 3 substituent(s), which is(are), the same or different, amino, monoalkylamino, dialkylamino, trialkylammonio, hydroxy, alkoxy, carbamoyl, monoalkylcarbamoyl, dialkylcarbamoyl, pyrrolidinyl, piperidyl or morpholinyl, L1 and L2 are, the same or different, —O—, —CO—O— or —O—CO—).