[PEG-liposome in DDS and clinical studies].

The current status of newly developed polyethyleneglycol coated liposome (PEG-liposome) were described in this review. Liposomes have demonstrated considerable promise as a carrier for the delivery of drugs in vivo. However, one of the drawback is that most liposomes intravenously injected into animals are rapidly removed from the blood circulation by uptake primarily in the cells of reticuloendothelial system (RES). It has been found that PEG-liposome are not readily taken up by the macrophages in the RES and hence stay in the circulation for a relatively long period of time. Pharmacokinetic analysis and therapeutic studies with tumor bearing mice revealed that PEG-liposomes have considerable potential as drug carriers for cancer therapy. Elevated liposome accumulation has been found in the tumor bearing mice model system. Results from clinical studies with doxorubicin encapsulated into PEG-liposomes (DOXIL) in AIDS-related Kaposi's sarcoma revealed an increased therapeutic efficacy compared to free-drug. These new formulations of long-circulating liposomes (PEG-liposome) offer the development of immunoliposomes with both long survival times in circulation and target recognition being retained in vivo. Fab'-PEG-immunoliposome was newly designed to gain long-circulating enough to extravasate to the targeted solid tumor in vivo. An ultimate goal of Fab'-PEG-immunoliposome is the incorporation of a fusogenic molecules that would induce fusion of liposome following their binding to the target cells or their internalization by endocytosis. Such liposomal formulations should be useful for endocytotic internalization of plasmid DNA and other bioactive materials.