Photodynamic therapy of infectious and malignant diseases

The application of light-induced or photodynamic chemical reactions for inactivating or killing both disease-causing organisms and malignant tumors is discussed. Currently, Phase-III, FDA-sanctioned trials are under way using the initially commercially developed porphyrin photosensitizer, dihematopor-phyrin ether. They are designed to ascertain if photodynamic therapy is efficacious in treating cancer of the lung, bladder, and esophagus. Numerous investigations under way to identify other photosensitizers that can be activated at longer wavelengths and absorb light more efficiently, thus offering potential treatment of cancer tumors that are thicker or more deeply buried, are briefly summarized, as well as investigations of the effects of localizing photosensitizers in various portions of a normal cell, a tumor cell, or an infectious agent, whether viral or cellular. The purpose of these studies is to relate localization and cellular lethality to those chemical attributes of the photosensitizer that control its pattern of localization