Abstract: A unit-type polyion complex for use in delivering nucleic acid to a target site in a patient includes one or more molecules of a block copolymer having a poly(ethylene glycol) segment and a cationic poly(amino acid) segment and one or more molecules of a nucleic acid. A total quantity of positive charges derived from side chains of the cationic poly(amino acid) segment of the block copolymer in the unit-type polyion complex is not offset by a total quantity of negative charges derived from the nucleic acid. Furthermore, the nucleic acid has a strand length of 10-50 bases, the molecular weight of the poly(ethylene glycol) segment is 40×103 or more, and the block copolymer has a binding constant (Ka) for the nucleic acid of 3.0×105 or more.

Abstract: A unit structure-type pharmaceutical composition includes a single nucleic acid, such as an antisense nucleic acid, electrostatically bound to a single block copolymer having a cationic polyamino acid segment and a hydrophilic polymer chain segment. The negative charges of the nucleic acid are counterbalanced, at least substantially, by the positive charges of the cationic polyamino acid segment such that the pharmaceutical composition is electrically neutral or nearly electrically neutral. Further, the nucleic acid is covered with the hydrophilic polymer chain segment. The block copolymer thereby improves the blood retention capability of the nucleic acids.

Abstract: A unit-type polyion complex for use in delivering nucleic acid to a target site in a patient includes one or more molecules of a block copolymer having a poly(ethylene glycol) segment and a cationic poly(amino acid) segment and one or more molecules of a nucleic acid. A total quantity of positive charges derived from side chains of the cationic poly(amino acid) segment of the block copolymer in the unit-type polyion complex is not offset by a total quantity of negative charges derived from the nucleic acid. Furthermore, the nucleic acid has a strand length of 10-50 bases, the molecular weight of the poly(ethylene glycol) segment is 40×103 or more, and the block copolymer has a binding constant (Ka) for the nucleic acid of 3.0×105 or more.

Abstract: A unit structure consists of a single nucleic acid having a length of 10 to 30 bases, and a single block copolymer having a cationic polyamino acid segment and a hydrophilic polymer chain segment. In this unit structure: (i) 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 nucleic acid in the unit structure falls within a range of ±10% of the total of the negative charges derived from the nucleic acid, (ii) the hydrophilic polymer chain segment comprises polyethylene glycol, (iii) the polyethylene glycol has a radius of inertia (Rg) equal to or longer than the length of the nucleic acid, and (iv) the cationic polyamino acid segment is bound to the nucleic acid via electrostatic bonds.

Abstract: A unit structure-type pharmaceutical composition includes a single nucleic acid, such as an antisense nucleic acid, electrostatically bound to a single block copolymer having a cationic polyamino acid segment and a hydrophilic polymer chain segment. The negative charges of the nucleic acid are counterbalanced, at least substantially, by the positive charges of the cationic polyamino acid segment such that the pharmaceutical composition is electrically neutral or nearly electrically neutral. Further, the nucleic acid is covered with the hydrophilic polymer chain segment. The block copolymer thereby improves the blood retention capability of the nucleic acids.

Abstract: A unit structure-type pharmaceutical composition includes at least one nucleic acid, such as siRNA, electrostatically bound to at least one block copolymer having a cationic polyamino acid segment and a hydrophilic polymer chain segment. The negative charge(s) of the nucleic acid are counterbalanced, at least substantially, by the positive charge(s) of the cationic polyamino acid segment such that the pharmaceutical composition is electrically neutral or nearly electrically neutral. Further, the nucleic acid is covered with the hydrophilic polymer chain segment(s). The at least one block copolymer thereby improves the blood retention capability of the nucleic acid(s).

Abstract: A unit structure-type pharmaceutical composition includes at least one nucleic acid, such as siRNA, electrostatically bound to at least one block copolymer having a cationic polyamino acid segment and a hydrophilic polymer chain segment. The negative charge(s) of the nucleic acid are counterbalanced, at least substantially, by the positive charge(s) of the cationic polyamino acid segment such that the pharmaceutical composition is electrically neutral or nearly electrically neutral. Further, the nucleic acid is covered with the hydrophilic polymer chain segment(s). The at least one block copolymer thereby improves the blood retention capability of the nucleic acid(s).