Monoclonal antibody targeting of liposomes to mouse lung in vivo.

A monoclonal antibody (MoAb), 273-34A, specifically binds to an epitope expressed almost exclusively on capillary endothelial cells of the lung. Within 15 min after i.v. injection, approximately 80 to 85% of the injected radioiodinated MoAb 273-34A accumulates in the lung. Approximately 90 to 95% of the recovered dose is found in the lung for up to 1 week postinjection. Ratios of MoAb 273-34A to a nonspecific, irrelevant MoAb 135-14 are 250 to 285 times higher in the lung than in the serum. When 273-34A was coupled with palmitic acid and incorporated into liposomes, the amount of 125I-labeled liposomes recovered per g of tissue was 12 times higher in the lung than in the liver at 15 min postinjection, and 22 times higher at 5 h postinjection. At 24 h postinjection the amount of liposomes per gram of lung tissue was still 6.0 times the amount per gram of liver tissue. Liposomes conjugated to MoAb 273-34A locate in the lung 20 and 15 times better than do liposomes conjugated to the nonspecific MoAb 135-14 at 15 min and 24 h postinjection, respectively. The results indicate that this immunoliposome system could be used as a model for enhanced drug delivery to the lung. The potential use for delivering anticancer drugs for therapy of lung tumors is discussed.