Liposomes as drug carriers in cancer therapy.

Liposomes, microscopic particles composed of lipid bilayer membranes, can carry water-soluble drugs in their aqueous compartments and lipid soluble drugs in their bilayers. Over the last 10 years, they have been studied more intensively than any other type of drug carrier. The first impulse, as with other pharmaceuticals, has been to inject them iv. However, since they do not leave the vascular system readily except in the sinusoids of liver and spleen, many of the projected applications to nonhematogenous cancers are unlikely to succeed. Nonetheless, the last few years have brought a great increase in sophistication with respect to the physical chemistry, biochemistry, and pharmacology of liposomes. Routes other than the vascular are being explored, and iv injection is being exploited for access to targets within the vascular space. The most likely clinical applications to be successful soon are in parasitology and immunology; practical applications in oncology are distinctly possible, but still speculative.