The present invention provides a polymer DDS which enables the controlled release of a drug having a carboxyl group. A drug-conjugated block copolymer according to the present invention is represented by the general formula: A-B. In the general formula, A represents a polyethylene glycol chain segment； and B represents a copolyamino acid chain segment containing a repeating unit represented by general formula (i) and/or (ii), wherein X in each of formulae (i) and (ii) represents a residue of the drug and the residue may have a linking group.本發明提供一種使具有羧基之藥物之釋出控制成為可能之聚合物DDS。本發明之藥物複合化嵌段共聚合體係由通式A-B表示。A表示聚乙二醇鏈段，B表示包含由下述通式(i)及/或(ii)所表示之重複單位之共聚胺基酸鏈段，式(i)及(ii)中之X表示可具有連結基之藥物之殘基。
