An object of the present invention is to provide a pharmaceutical preparation composition containing a polymerized camptothecin derivative formed by bonding a camptothecin derivative having nanoparticle-forming property aggregated in an aqueous solution to a polymer carrier And improve the stability of the preparation. In particular, its subject is to provide a pharmaceutical preparation having excellent storage stability while maintaining nanoparticle formation as an important factor. The pharmaceutical preparation of the present invention is a block copolymer comprising a polyethylene glycol segment and a polyglutamic acid segment including a glutamic acid unit bonded to a camptothecin derivative, and the above-mentioned pharmaceutical preparation is Aggregates are formed in the aqueous solution, and when the above-mentioned pharmaceutical preparation is made into an aqueous solution with the concentration of the above camptothecin derivative as 1 mg / mL, the pH of the aqueous solution is 2.4 to 7.0, under shading and at 40 ° C After storage for 1 week, the rate of change of the aggregate forming ability of the above-mentioned pharmaceutical preparation is 50% or less.本發明之課題在於提供一種醫藥製劑組合物，其係含有使於水溶液中聚集而具有奈米粒子形成性之喜樹鹼衍生物鍵結於高分子載體上而成之高分子化喜樹鹼衍生物者，並且製劑穩定性獲得提昇。其課題尤其在於提供一種維持作為重要因子之奈米粒子形成性而保存穩定性優異之醫藥製劑。本發明之醫藥製劑係含有聚乙二醇鏈段與包含喜樹鹼衍生物所鍵結之麩胺酸單元之聚麩胺酸鏈段連結而成之嵌段共聚物者，並且上述醫藥製劑於水溶液中形成聚集體，將上述醫藥製劑製成以上述喜樹鹼衍生物含量濃度計為1 mg/mL之水溶液之情形時之該水溶液之pH值為2.4～7.0，於遮光下且40℃下保存1週後，上述醫藥製劑之該聚集體之形成能力之變化率為50%以下。
