Abstract: Disclosed is a drug complex of a drug having a hydroxyl group, which is capable of controlling the rate of the release of the drug therefrom in blood, the drug complex being represented by the following formula (1): A—B—C  (1) wherein A represents at least one carrier selected from the group consisting of saccharides each having a carboxyl group, polyethylene glycols each having a carboxyl group, aliphatic carboxylic acids each having a carboxyl group, and derivatives thereof each having a carboxyl group; B represents at least one spacer comprised of a compound having a amino group and a carboxyl group; C represents at least one drug having a hydroxyl group, wherein the carrier A is bonded to the spacer B through an amide bond formed between the carboxyl group of the carrier A and the amino group of the spacer B; and the spacer B is bonded to the drug C through an ester bond formed between the carboxyl group of the spacer B and the hydroxyl group of the drug C.

Abstract: A novel polysaccharide derivative, a drug carrier comprising a novel polysaccharide derivative, and a drug complex are disclosed. The polysaccharide derivative according to the present invention comprises a polysaccharide having a carboxyl group in which a peptide chain is introduced at a part or all of the carboxyl groups of the polysaccharide. The peptide chain comprises 1-8 amino acids which may be the same or different. A part or all of the amino groups in the peptide chain which are not involved in the linkages with the carboxyl groups of the polysaccharide or the carboxyl groups in the peptide chain may form an acid amide linkage or an ester linkage with a carboxyl group, an amino group or a hydroxyl group of a third compound such as drugs. The polysaccharide derivative has a property of accumulating in a high amount at a tumor, and thus can deliver efficiently a drug which has a side-effect or a limited sustainment of the drug efficacy to the tumor.