UVA-induced phenoxyl radical formation: A new cytotoxic principle in photodynamic therapy.

Psoralens are regularly used in therapy in combination with ultraviolet A light irradiation (PUVA) to treat skin diseases such as psoriasis, vitiligo, and mycosis fungoides. PUVA therapy is also used within the scope of extracorporeal photopheresis to treat a variety of diseases that have a suspected involvement of pathogenic T cells, including rejection of organ transplants, graft-vs-host disease, cutaneous T cell lymphoma, and autoimmune disorders. Because psoralens are the only photosensitizers used in PUVA therapies and are considered to be responsible for a number of side effects, the identification of alternative drugs is of practical interest.