LIPOSOME CIRCULATION TIME AND TUMOR TARGETING - IMPLICATIONS FOR CANCER-CHEMOTHERAPY

The pharmacokinetics and biodistribution of liposome-encapsulated drug s are controlled by the interplay of two variables: the rate of plasma clearance of the liposome carrier, and the stability of the liposome- drug association in circulation. inhibition of the rapid uptake of lip osomes by the reticuloendothelial system and reduction of the rate of drug leakage have resulted in long-circulating liposomal drug systems with valuable pharmacologic properties. These carrier systems show an improved extravasation profile with enhanced localization in tumors an d possibly in other tissues, such as skin. An anticancer drug, doxorub icin, encapsulated in polyethyleneglycol-coated, long-circulating lipo somes, shows a unique pharmacokinetic/toxicity pattern and promising a ntitumor activity in initial clinical studies.