The present invention provides a pharmaceutical composition. The pharmaceutical composition includes a block copolymer includng: a hydrophilic segment； a hydrophobic segment； and a boronic acid compound bonded to a side chain of the hydrophobic segment via a linker moiety including a heterocyclic structure, wherein: a cyclic skeleton of the heterocyclic structure has a boron atom derived from the boronic acid compound, atoms X's bonded to the boron atom and each selected from an oxygen atom and a nitrogen atom, and carbon atoms bonded to the atoms X's； and the block copolymer further comprises an organic group bonded to the carbon atoms, the organic group containing an aromatic group or cyclic alkyl group as a structure for protecting a boronic acid ester bond and/or a boron amide bond resulting from bonding between the boron atom and the atoms X's.
