A medicinal preparation is desired which has no harmful side effects such as hypersensitive reaction, heightens the water solubility of a sparingly water-soluble anticancer agent, maintains a high drug concentration in the blood, accumulates a drug in a tumor tissue at a high concentration, heightens the pharmacological effect of the sparingly water-soluble anticancer agent, and diminishes the side effects of the anticancer agent. Provided are: a novel 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 contains a sparingly water-soluble anticancer agent, especially paclitaxel, incorporated in the micelles in an amount necessary for a disease treatment without bonding it to the block copolymer and which can heighten the solubility of the drug in water； and an anticancer agent which comprises the micelle preparation as a medical ingredient, maintains a high concentration in the blood, has 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。
