Numerous photosensitizing pigments that absorb visible light and are selectively retained in neoplastic tissue are being investigated as potential photochemotherapeutic agents. While much emphasis is being placed on the synthesis of new, far-red absorbing photosensitizers, an alternative approach has been to stimulate the human body to produce its own natural photosensitizer, namely protoporphyrin IX (PpIX). Exogenous 5-aminolevulinic acid (ALA) is rapidly bioconverted into PP by mitochondria, the process being particularly efficient in tumor cells. Since PpIX has a natural and rapid clearing mechanism (via the capture of iron in the process of being converted into heme), ALA-PDT does not suffer from lingering skin phototoxicity. ALA may be introduced orally, intravenously, or topically, and ALA-PDT has been shown to be effective in the treatment of both malignant and non-malignant lesions.

Date Published: 31 January 1996
PDF: 9 pages
Proc. SPIE 2625, Photochemotherapy: Photodynamic Therapy and Other Modalities, (31 January 1996); doi: 10.1117/12.230940

Published in SPIE Proceedings Vol. 2625:
Photochemotherapy: Photodynamic Therapy and Other Modalities
Benjamin Ehrenberg; Giulio Jori; Johan Moan, Editor(s)