Anticancer therapy using glucuronate modified long-circulating liposomes.
Since conventional liposomes tend to be trapped by the reticuroendothelial systems (RES), their use as drug carriers is limited when the targets are not RES cells. Therefore, many attempts have been made to avoid the RES-trapping of liposomes. Favorable results were obtained by a modification of liposomes with a glucuronic acid derivative, PGlcUA, and polyethyleneglycol. These liposomes have a long-circulating character, and showed the further advantage for passive targeting to tumor tissues, since the vasculature in tumor tissues is leaky enough for small-sized liposomes to extravasate. Thus long-circulating liposomes are useful for tumor imaging and treatment. PGlcUA-modified liposomes were actually found to accumulate effectively in tumor tissue, and showed enhanced efficacy of antitumor agents, such as adriamycin and vincristine when they were encapsulated into the liposomes. Usefulness of PGlcUA liposomes as drug carriers was also observed in photodynamic therapy and in treatment of cancer by amphiphilic novel antitumor agents.