Photodynamic Therapy: A New Modality for the Treatment of Cancer*

Photodynamic therapy is a promising new modality for the treatment of neoplastic disease. Currently, Photofrin ® is the only photosensitizer approved for the treatment of human cancers. In the search for new, chemi cally pure second generation photosensitizing agents which absorb in the deep red region of the visible spectrum, a novel and unique photosensi tizer, CDS1, an iminium salt of copper octaethylbenzochlorin, was devel oped. This new photosensitizer is chemically pure, cationic, and possesses a strong (e = 35000 M- 1 • cm-1) absorption peak at 750 nm (in dichlo-romethane). With copper in the aromatic cavity and a triplet lifetime which is not measurable (<20 nsec), the photodynamic activity of CDS1 was unexpected. Preliminary in vitro and in vivo animal studies with a trans plantable urothelial tumor indicate that CDS1 is an effective photosensi tizing agent when used in conjunction with a broad band xenon arc light source or a low frequency, high peak power pulsed alexandrite laser