Abstract: The invention provides block copolymers formed of poly(ethylene glycol) segments and poly(amino acid derivative) segments having side chains of at least one kind of specific amine residue. The invention also provides polyion complexes of such copolymers with polynucleotides and the like. These block copolymers are useful as carriers for in vivo delivery of active substances such as DNA.

Abstract: A process for purification which permits satisfactory removal of impurities from a block copolymer consisting essentially of polyethylene glycols and poly(acidic amino acid) and is suitable for the production of a polymeric carrier having a pharmaceutically acceptable purity; a process for producing such a polymeric carrier; a block copolymer reduced in impurity content; a polymeric carrier as described above; pharmaceutical preparations in polymeric form, produced by the use of the carrier; and a method of subjecting polyethylene glycols and poly(acidic amino acids)—which are impurities contained in the block copolymer—to treatment with either an ion-exchange resin or a partition/absorption resin and then determining the quantities of them with a gel filtration column.

Abstract: A dimer, trimer or tetramer of an anthracycline compound which can be obtained by directly, chemically bonding anthracycline compounds having anticancer activities to each other by an alkali treatment. A high molecular block copolymer-drug complex pharmaceutical preparation in which the high molecular block copolymer having a hydrophilic polymer segment and a hydrophobic polymer segment forms a micelle having the hydrophilic segment as its outer shell and contains in its hydrophobic inner core a dimer, trimer or tetramer of anthracycline compound alone or together with other drugs.