Potential of liposomes as drug-carriers in cancer chemotherapy: a review.
Liposomes are bilayered phospholipid vesicles that have been proposed as vehicles for the selective delivery of cytotoxic drugs into malignant cells. In vitro and in vivo experiments have indicated that the activity of a range of drugs or their active metabolites may be enhanced by encapsulation in liposomes, particularly when used against drug-resistant tumours. Moreover, liposomal entrapment certainly has a marked effect on the tissue distribution and rates of clearance of cytotoxic drugs, and also appears to reduce their toxicity in most cases. However, in both animal and patient studies, the major sites of uptake following IV administration consistently appear as the liver and spleen. Preferential tumour uptake has therefore not yet been achieved, althrough a degree of localization of liposomal labels can be demonstrated in the vicinity of experimental animal tumours in certain circumstances. Liposomes may have a future role in cancer chemotherapy, but much laboratory work remains to be done before clinical application can be considered.