Liposomes with enhanced circulation time

Abstract

A composition of liposomes which contain an entrapped pharmaceutical agent and are characterized by: (a) liposome sizes predominantly between about 0.08 and 0.5 microns: (b) at least about 50 mole percent of a membrane-rigidifying component, such as sphingomyelin or neutral phospholipids with predominantly saturated acyl chains: and (c) between about 5-15 mole percent ganglioside G.sub.M1. The liposomes show a blood/RES tissue distribution ratio, two hours after intravenous administration, which is substantially greater than the sum of the distribution ratios observed with similarly constructed liposome compositions containing the membrane-rigidifying agent alone and gangliosides alone. Also disclosed are methods for enhancing the blood/RES ratio of intravenously administered liposomes, and for assessing the effect of selected liposome components on in vivo uptake of liposomes by cells of the reticuloendothelial system (RES).

Dependencies are inferred from the claim text.