Patent ID: 8519051

Claim:
A drug conjugated block copolymer in which a drug having a ketone structure being bound to a hydrazide group of the block copolymer, said block copolymer comprising a water-soluble polymer region consisting of polyethylene glycol and a polyamino acid region having a hydrazide group and a hydrophobic group in the side chain, wherein the block copolymer comprises the following structure: wherein R 1 , which may be the same or different, represents a hydrogen atom, a methoxy group, a methyl group, or a substituted linear or branched or cyclic C 1 -C 12 alkyl group, in which the substituent represents a functional group selected from the group consisting of a maleimide group, an amino group, a carboxyl group, a thiol group, a hydroxy group and an active ester group which may be protected, R 2 represents a hydrogen atom, a saturated or an unsaturated C 1 -C 30 aliphatic carbonyl group or an arylcarbonyl group, R 3 represents —O—R 5 or —NH—R 5 in which R 5 , which may be the same or different, represents a hydrophobic group, and R 4 represents a hydroxy group, a saturated or an unsaturated C 1 -C 30 aliphatic oxy group or an aryl-lower alkyloxy group, L 1 and L 2 independently from each other represents a linker, m represents an integer of 5-1000, n represents an integer of 0-1000, p represents an integer of 1-1000, and q represents an integer of 1-1000, provided that when units having a hydrophobic group in the side chain account for 25% or more 75% or less of the total units of the polyamino acids in the block copolymer and when units having a carboxylic acid group in the side chain are present, then the units having a carboxylic acid group in the side chain, units having a hydrophobic group in the side chain, and units having a hydrazide group in the side chain are randomly distributed throughout the polyamino acid region, and when units having a carboxylic acid group in the side chain are absent, then the units having a hydrophobic group in the side chain and units having a hydrazide group in the side chain are randomly distributed throughout the polyamino acid region, and y represents an integer of 1 or 2, and wherein as a result of said drug being bound to said block copolymer, the units having a hydrazide group in the side chain account for more than 0% to 35% or less of the total units of the polyamino acids in the block copolymer.