A composition comprising: a glutamic acid derivative represented by General Formula: wherein R 1 and R 2 each independently represent a group selected from the group consisting of a hydrogen atom, an alkyl group which may have a substituent, and an alkoxycarbonyl group which may have a substituent; R 3 represents a hydrogen atom or an alkyl group which may have a substituent; A 1 and A 2 each represent a group selected from the group consisting of C- R 6, C- R 7, and a nitrogen atom; R 6 represents one or more groups selected from the group consisting of a hydrogen atom, a halogen atom, a nitro group, a hydroxy group, an alkyl group which may have a substituent, and an alkoxy group which may have a substituent; R 7 is represented by the following General Formula: wherein R 4 and R 5 each independently represent a hydrogen atom or an alkyl group which may have a substituent; L represents a linking group selected from the group consisting of an oxygen atom, an oxycarbonyl group, and a bond; X represents a residue of a physiologically active substance having one or more functional groups selected from the group consisting of an aliphatic hydroxy group, an aromatic hydroxy group, an amino group, and a carboxy group, (a) when X is a residue of a physiologically active substance having one or more functional groups selected from the group consisting of an aliphatic hydroxy group and an amino group, L represents an oxycarbonyl group; (b) when X represents a residue of a physiologically active substance having a carboxy group, L represents an oxygen atom; and (c) when X represents a residue of a physiologically active substance having an aromatic hydroxy group, L represents a bond or an oxycarbonyl group, wherein any one of A 1 and A 2 represents C- R 7; the other represents C- R 6 or a nitrogen atom; and B 1, B 2, and B 3 each independently represent C- R 6 or a nitrogen atom; or a pharmacologically acceptable salt thereof; and a block copolymer having a polyethylene glycol segment linked to a polyamino acid segment with a hydrophobic functional group. a glutamic acid derivative represented by General Formula: wherein R 1 and R 2 each independently represent a group selected from the group consisting of a hydrogen atom, an alkyl group which may have a substituent, and an alkoxycarbonyl group which may have a substituent; R 3 represents a hydrogen atom or an alkyl group which may have a substituent; A 1 and A 2 each represent a group selected from the group consisting of C- R 6, C- R 7, and a nitrogen atom; R 6 represents one or more groups selected from the group consisting of a hydrogen atom, a halogen atom, a nitro group, a hydroxy group, an alkyl group which may have a substituent, and an alkoxy group which may have a substituent; R 7 is represented by the following General Formula: wherein R 4 and R 5 each independently represent a hydrogen atom or an alkyl group which may have a substituent; L represents a linking group selected from the group consisting of an oxygen atom, an oxycarbonyl group, and a bond; X represents a residue of a physiologically active substance having one or more functional groups selected from the group consisting of an aliphatic hydroxy group, an aromatic hydroxy group, an amino group, and a carboxy group, (a) when X is a residue of a physiologically active substance having one or more functional groups selected from the group consisting of an aliphatic hydroxy group and an amino group, L represents an oxycarbonyl group; (b) when X represents a residue of a physiologically active substance having a carboxy group, L represents an oxygen atom; and (c) when X represents a residue of a physiologically active substance having an aromatic hydroxy group, L represents a bond or an oxycarbonyl group, wherein any one of A 1 and A 2 represents C- R 7; the other represents C- R 6 or a nitrogen atom; and B 1, B 2, and B 3 each independently represent C- R 6 or a nitrogen atom; or a pharmacologically acceptable salt thereof; and (a) when X is a residue of a physiologically active substance having one or more functional groups selected from the group consisting of an aliphatic hydroxy group and an amino group, L represents an oxycarbonyl group; (b) when X represents a residue of a physiologically active substance having a carboxy group, L represents an oxygen atom; and (c) when X represents a residue of a physiologically active substance having an aromatic hydroxy group, L represents a bond or an oxycarbonyl group, a block copolymer having a polyethylene glycol segment linked to a polyamino acid segment with a hydrophobic functional group.