To provide a medicinal preparation that has no harmful side effects such as hypersensitive reaction, heightens the solubility in water of a hardly water-soluble anticancer agent, maintains a high drug concentration in the blood, accumulates a drug in a tumor tissue at a high concentration, enhances a pharmacological effect of the hardly water-soluble anticancer agent, and reduces side effects of the anticancer agent. ； There are provided a new block copolymer which can be a drug carrier having no harmful side effects such as hypersensitive reaction； a micelle preparation in which micelles are formed and which incorporates the hardly water-soluble anticancer agent, especially a paclitaxel, into the micelles in an amount necessary for disease treatment without bonding it to the block copolymer and which can heighten the solubility of the drug in water； and the anticancer agent which contains the micelle preparation as a medical ingredient, maintains a high concentration in the blood, shows more potent drug activity, and is reduced in toxicity.業者期望開發一種醫藥製劑，其不具有過敏反應等有害副作用，增加水難溶性抗癌劑對水之溶解性，維持較高之藥物血中濃度，以高濃度將藥物積聚於腫瘤組織，增強該水難溶性抗癌劑之藥理效果並且減輕副作用。本發明之目的在於提供一種新穎嵌段共聚物，其可成為不表示過敏反應等有害副作用之藥物載體；微胞調製物，其可形成微胞，無需使治療疾病所需量之水難溶性抗癌劑、尤其是紫杉醇結合於該嵌段共聚物就可直接吸入微胞內，提高該藥物對水之溶解性；以及抗癌劑，其將該微胞調製物作為藥效成分，可維持較高之血中濃度，顯示更強之藥效且減輕毒性。
