Photodynamic therapeutics: basic principles and clinical applications

Photodynamic therapy (PDT) is a promising new treatment for cancer that has been recently accepted in the clinic. PDT involves the localization of a l ight-sensitive drug (photosensitizer) in the target tissue prior to illumin ation using an appropriate wavelength. Cytotoxic agents generated upon illu mination trigger a cascade of biochemical responses that inactivate cancer cells either directly or through the induction of vascular stasis. These tr eatments are better tolerated as they destroy diseased tissue while leaving normal tissue intact. The haematoporphyrin derivative, Photofrin(R), has b een approved in a number of European and Asian countries, as well as in Nor th America. To enhance the potential of PDT and explore its application for other conditions, second-generation photosensitizers are being rigorously investigated.