Preactivation: a new concept for generation of photoproducts for potential therapeutic applications

Controlled exposure of photoactive compounds to light prior to their use in biological targets results in the formation of heretofore unknown photoproducts. This process of photoproduct generation, termed preactivation, renders the photoactive compound capable of systemic use without further dependence on light. We have demonstrated that preactivated Merocyanine and preactivated Photofrin-II possess significant antitumor and antiviral activity against certain tumor cells and viruses, while under identical conditions normal cells and tissues are minimally affected. Thus, the preactivation procedure may represent a promising therapeutic modality for controlling systemic malignancies and viral infections.