[Problem] 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. [Solution] 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°C shielded from light.
