Design of macromolecular prodrug of 5-fluorouracil using N-acetylpolygalactosamine as a targeting carrier to hepatoma

Abstract α-1,4-Polygalactosamine (PGA) purified from the culture fluid of Paecilomyces sp. I-1 strain and N-acetylated α-1,4-polygalactosamine (NAPGA) are chitosan- and chitin-like biodegradable, compatible α-1,4-linked polysaccharides, respectively. Partially N-acetylated PGA was found to show the stronger binding activity onto MH134Y hepatoma cells than three kinds of normal lymphocytes, bone marrow, T and B cells from the results of binding assay of 14 C-50% N-acetylated PGA in vitro. Since PGA and NAPGA have the unreducing end groups of galactosamine and N -acetyl galactosamine, respectively, they were suggested to exhibit the receptor-mediated affinities to hepatoma cells. In order to provide the lysosomotropic macromolecular prodrug of fluorouracil (5FU) having a targeting ability to hepatoma, we synthesized water-soluble 6- O -carboxymethyl-NAPGA-immobilized 5FUs through Gly-Phe-Leu-Gly, monomethylene spacer groups. The obtained conjugate showed the cathepsin-B-susceptible release behavior of 5FU and then xhibited the stronger cytotoxic activity than free 5FU against HLE hepatoma cells in vitro.