Cutaneous photosensitization by topical hematoporphyrin derivative formulations; potential clinical applications

Photoradiation therapy provides a valuable approach for the selective therapy of diseases localized to the skin and mucous membranes. The topical delivery of photo-reactive drugs provides a means of further enhancing this selectivity by decreasing the undesired prolonged cutaneous phototoxicity associated with the systemic use of such agents. In this study vehicles were selected for effective topical delivery of hematoporphyrin derivative (HPD). Irradiation with either red light (600 nm) or long wave ultraviolet light (UVA) (360 nm) produced localized cutaneous phototoxicity and selective inhibition of epidermal cell proliferation in guinea pigs. Topical delivery produced a higher HPD concentration in dysplastic mouse epidermis versus surrounding normal epidermis. Preliminary clinical studies have demonstrated a partial clinical response in vaginal intraepithelial neoplasia. Studies are in progress to evaluate topical HPD in the treatment of intraepithelial neoplasia of the female genital tract, and hyper...