Liposomes designed to avoid the reticuloendothelial system.

Recent work has revealed some new and important characteristics of liposomes: Inclusion of certain glycolipids within liposomes composed of phosphatidylcholine or sphingomyelin and cholesterol drastically prolongs the circulation time and reduces their uptake by liver and spleen. Concomitantly, their accumulation in several implanted tumors is substantially increased. These studies suggest that controlling the circulation time of liposomes and limiting their non-specific uptake by the Reticuloendothelial system (RES) opens up new opportunities for achieving specific targeting to tumors in vivo, with both diagnostic and therapeutic possibilities.