The problem is to provide a pharmaceutical formulation containing a polymerized camptothecin derivative obtained by bonding a camptothecin derivative having the ability to form nanoparticles by association in aqueous solution to a polymer carrier, wherein the pharmaceutical formulation composition has improved formulation stability. In particular, the problem is to provide a pharmaceutical formulation having excellent storage stability that maintains the ability to form nanoparticles and the camptothecin derivative bonding stability, which are important factors. A pharmaceutical formulation containing a block copolymer linking a polyethylene glycol segment and a polyglutamic acid segment including a camptothecin derivative bonded to a glutamic acid unit, and a saccharide, wherein the pharmaceutical formulation forms aggregates in aqueous solution, and the change in the scattered light intensity of the aggregates in the pharmaceutical formulation is 20% or less after the pharmaceutical formulation has been stored for four weeks at 40 DEG C shielded from light.本發明之課題在於提供一種醫藥製劑組合物，其係含有於水溶液中締合而具有奈米粒子形成性之使喜樹鹼衍生物鍵結於高分子載體而成之高分子化喜樹鹼衍生物之醫藥製劑，且製劑穩定性得到提高。尤其，其課題在於提供一種可維持作為重要因素之奈米粒子形成性與喜樹鹼衍生物鍵結穩定性而保存穩定性優異之醫藥製劑。 本發明之醫藥製劑含有聚乙二醇鏈段與包含鍵結有喜樹鹼衍生物之麩胺酸單元之聚麩胺酸鏈段連結而成之嵌段共聚物、及糖類，上述醫藥製劑於水溶液中形成締合體，將上述醫藥製劑於遮光下且40℃下保存4週後，上述醫藥製劑之該締合體之散射光強度變化率為20%以下。
