The present invention addresses the problem of providing a polymer-micelle-type DDS preparation which makes it possible to improve the transfer, permeability and retention of a pharmacologically active substance to and in an affected target tissue, such as a tumor tissue and an inflammation affected tissue, to improve the activity of the pharmacologically active substance, thereby exerting the pharmacologically active effect of the pharmacologically active substance efficiently. A block copolymer (A) comprising a hydrophilic polymer segment containing a polyethylene glycol chain and a hydrophobic polymer segment containing a polyamic acid chain having a hydrophobic substituent in a side chain thereof, wherein the hydrophilic polymer segment and the hydrophobic polymer segment are linked to each other, a target binding site is bound to the hydrophilic polymer segment, and the molecular weight of a main chain polymer composed of the polyethylene glycol chain and the polyamic acid chain is 2 to 10 kilodaltons inclusive.本發明之課題在於提供一種高分子微胞型DDS製劑,其藉由提高對腫瘤組織或炎症患部組織等疾病靶組織之移行性、浸透性、滯留性,提高藥理活性物質之作用,而可有效率地發揮藥理活性效果,本發明之嵌段共聚物(A)係含有聚乙二醇鏈之親水性聚合物鏈段與含有側鏈具有疏水性取代基之聚胺基酸鏈之疏水性聚合物鏈段連結而成之嵌段共聚物,並且於該親水性聚合物鏈段鍵結有靶結合部位,合併該聚乙二醇鏈與該聚胺基酸鏈而成之主鏈聚合物之分子量為2千道爾頓以上且10千道爾頓以下。無
