Unit structure-type pharmaceutical composition for nucleic acid delivery

1. A unit structure consisting of a single antisense nucleic acid and a single block copolymer, wherein:

(i) the block copolymer has a cationic polyamino acid segment and a polyethylene glycol at one terminal of the polyamino acid chain segment,

(ii) the polyethylene glycol has a molecular weight of from 20,000 Da or more,

(iii) a difference between a total of positive charges derived from cationic groups of the cationic polyamino acid segment and a total of negative charges derived from the antisense nucleic acid in the unit structure falls within a range of ±10% of the total of the negative charges derived from the antisense nucleic acid, and

(iv) the cationic polyamino acid segment is bound to the antisense nucleic acid via electrostatic bonds, and

wherein the block copolymer is selected from the group consisting of the following formulae (1)-(2):

wherein:

R 1a to R 1d are each independently a hydrogen atom, an unsubstituted or substituted linear or branched alkyl group having 1 to 12 carbon atoms, or a group represented by the following formula (I):

where k represents an integer of from 1 to 5, and D represents a target binding site;

R 2 is a hydrogen atom, an unsubstituted or substituted linear or branched alkyl group having 1 to 12 carbon atoms, or an unsubstituted or substituted linear or branched alkylcarbonyl group having 1 to 24 carbon atoms;

R 3 is a hydroxyl group, an unsubstituted or substituted linear or branched alkyloxy group having 1 to 12 carbon atoms, an unsubstituted or substituted linear or branched alkenyloxy group having 2 to 12 carbon atoms, an unsubstituted or substituted linear or branched alkynyloxy group having 2 to 12 carbon atoms, or an unsubstituted or substituted linear or branched alkyl-substituted imino group having 1 to 12 carbon atoms;

R 4a and R 4b are each independently a methylene group or an ethylene group;

R 5a and R 5b are the same group or different groups selected from the group consisting of:

—NH—(CH 2 ) p1 —[NH—(CH 2 ) q1 —] r1 NH 2   (i);

—NH—(CH 2 ) p2 —N[—(CH 2 ) q2 —NH 2 ] 2   (ii);

—NH—(CH 2 ) p3 —N{[—(CH 2 ) q3 —NH 2 ][—(CH 2 ) q4 —NH—] r2 H}  (iii); and

—NH—(CH 2 ) p4 —N{—(CH 2 ) q5 —N[—(CH 2 ) q6 —NH 2 ] 2 } 2   (iv),

where p1 to p 4 , q1 to 6, and r1 to 2 are each independently an integer of from 1 to 5;

Q is —NH 2 , —NHC(═NH)NH 2 , or a group represented by the following formula (II);

L is a divalent linking group or a valence bond;

x1 to x4 are each independently an integer of from 450-2000;

y, z, and v are each independently an integer of from 0 to 60, provided that y, z, and v satisfy the relationship 5≤y+z+v≤60;

w is an integer of from 1 to 6;

l and m are each independently an integer of from 0 to 5; and

n is 1.

2. The unit structure according to claim 1 , wherein x1 to x4 are each independently an integer of from 450 to 1200.

3. The unit structure according to claim 1 , wherein:

the antisense nucleic acid has a length of 18 to 30 bases.

4. The unit structure according to claim 1 , wherein all cationic amino acids in the cationic polyamino acid segment have only one cationic group in each side chain.

5. The unit structure according to claim 1 , wherein the cationic polyamino acid segment contains exclusively cationic amino acid residues.

6. The unit structure according to claim 4 , wherein the single antisense nucleic acid consists of 18 to 30 bases.

7. A pharmaceutical composition, comprising:

the unit structure according to claim 1 , and

an excess of the block copolymer that is not electrostatically bound with the nucleic acid.

8. The pharmaceutical composition according to claim 7 , wherein the pharmaceutical composition has an N/P ratio of 5 or more, the N/P ratio being defined as [total number (N) of cationic groups in all block copolymers in the pharmaceutical composition]/[total number (P) of phosphate groups in all nucleic acid in the pharmaceutical composition].

9. The pharmaceutical composition according to claim 8 , wherein the N/P ratio is 10 or more.

10. A unit structure consisting of a single antisense nucleic acid and a single block copolymer, wherein:

a difference between a total of positive charges derived from cationic groups of a cationic polyamino acid segment of the single block copolymer and a total of negative charges derived from the antisense nucleic acid in the unit structure falls within a range of 10% of the total of the negative charges derived from the antisense nucleic acid,

the cationic polyamino acid segment is bound to the antisense nucleic acid via electrostatic bonds, and

the block copolymer is selected from the group consisting of the following formulae (1)-(2):

wherein:

R 1a to R 1d are each independently a hydrogen atom, an unsubstituted or substituted linear or branched alkyl group having 1 to 12 carbon atoms, or a group represented by the following formula (I):

where k represents an integer of from 1 to 5, and D represents a target binding site;

R 2 is a hydrogen atom, an unsubstituted or substituted linear or branched alkyl group having 1 to 12 carbon atoms, or an unsubstituted or substituted linear or branched alkylcarbonyl group having 1 to 24 carbon atoms;

R 3 is a hydroxyl group, an unsubstituted or substituted linear or branched alkyloxy group having 1 to 12 carbon atoms, an unsubstituted or substituted linear or branched alkenyloxy group having 2 to 12 carbon atoms, an unsubstituted or substituted linear or branched alkynyloxy group having 2 to 12 carbon atoms, or an unsubstituted or substituted linear or branched alkyl-substituted imino group having 1 to 12 carbon atoms;

R 4a and R 4b are each independently a methylene group or an ethylene group;

R 5a and R 5b are the same group or different groups selected from the group consisting of:

—NH—(CH 2 ) p1 —[NH—(CH 2 ) q1 —] r1 NH 2   (i);

—NH—(CH 2 ) p2 —N[—(CH 2 ) q2 —NH 2 ] 2   (ii);

—NH—(CH 2 ) p3 —N{[—(CH 2 ) q3 —NH 2 ][—(CH 2 ) q4 —NH—] r2 H}  (iii); and

—NH—(CH 2 ) p4 —N{—(CH 2 ) q5 —N[—(CH 2 ) q6 —NH 2 ] 2 } 2   (iv),

where p1 to p4, q1 to 6, and r1 to 2 are each independently an integer of from 1 to 5;

Q is —NH 2 , —NHC(═NH)NH 2 , or a group represented by the following formula (II);

L is a divalent linking group or a valence bond;

x1 to x4 are each independently an integer of from 450-2000;

y, z, and v are each independently an integer of from 0 to 60, provided that y, z, and v satisfy the relationship 5≤y+z+v≤60;

w is an integer of from 1 to 6;

l and m are each independently an integer of from 0 to 5; and

n is 1.

11. The unit structure according to claim 10 , wherein the single antisense nucleic acid consists of 18 to 30 bases.