Liposomal drug delivery system

We have recently described an immunoliposome targeting system which involves the use of monoclonal antibodies specific for the pulmonary endothelial cells. We have employed the antibodies, 34A and 201B, which bind to a surface glycoprotein, gp112, which is specifically expressed in high concentrations in the capillary endothelial cells of the mouse lung. Intravenously injected immunoliposomes (34A- or 201B-liposomes) to the mice gain direct access and bind efficiently to the lung. Approximately 50% of the injected dose was accumulated in the lung for 34A-liposomes which contained an average of 935 antibody molecules per liposome. Lung accumulation of 34A-liposomes is completely blocked by a preinjection of free antibody 34A, indicating that the immunoliposome accumulation at the target site is immunospecific. The level of lung accumulation increases significantly as the antibody/lipid ratio of the immunoliposome increases.