Poly(ethylene glycol)-Grafted Liposome Therapeutics

Abstract

PEG-lipid conjugates have been synthesized and incorporated into liposomes to form a steric polymer surface barrier that enhances drug delivery applications. The PEG steric coating reduces protein binding, cellular recognition, and uptake. Thus these liposomes persist in the blood permitting extravasation into tumors, infections, and sites of inflammation. Thus PEG-grafted liposome formulations can deliver encapsulated drugs to these pathological sites, shown with doxorubicin treatment of tumors and Kaposi's Sarcoma. Other drugs are being evaluated as PEG-grafted liposome drug formulations to take advantage of this form of "passive" targeting. Additionally, efforts are being applied to obtain ligand-mediated targeting or ligand presentation through chemical conjugation to the exterior surface of the PEG coating. Improved drug targeting and use for gene therapy, which requires intracellular delivery, are limited by a need to control tissue distribution separately from drug release or cellular interactions.