ABSTRACT

Photodynamic therapy (PDT) involves photosensitizing (light-sensitive) drugs, light, and tissue oxygen to treat a wide range of medical conditions primarily in the oncology field. Photosensitizing agents, many of which are porphyrins or chemicals of similar structure, are administered locally or parenterally and selectively absorbed or retained within the tissues targeted for therapy. This differential selectivity or retention promotes selective damage when the target tissue is exposed to light of an appropriate wavelength; the surrounding normal tissue, containing little or no drug, absorbs little light and is thus spared injury.1,2 PDT clinical research has historically focused primarily and successfully on cancer treatment;3-6 however, it has shown promise as a breakthrough treatment in ophthalmic, urologic, autoimmune, and cardiovascular diseases. Any disease associated with rapidly growing tissue, including the formation of abnormal blood vessels, can potentially be treated with this technology. For the cardiovascular system, selectivity renders PDT particularly appealing in treating restenosis and atherosclerotic illnesses such as coronary artery disease, in which other catheter-based approaches are relatively non-selective and carry a substantial risk of damage to the normal arterial wall.7 Recently there have been preclinical and clinical studies targeted to examine the utility of PDT for vascular applications. This chapter summarizes the mechanisms of action, PDT systems, and the results of these preclinical and clinical studies.