Bombesin antagonist based radiotherapy of prostate cancer combined with WST-11 vascular targeted photodynamic therapy

Kim et al. (1) from Memorial Sloan-Kettering Cancer Center investigated the possibility to enhance the effect of radionuclide therapy by vascular-targeted photodynamic (VTP) therapy in an experimental prostate cancer animal model. They used bombesin-antagonist peptide as a targetor which is binding gastrin releasing peptide receptor (GRPr) and it was labeled with high energy beta-emitting radionuclide ⁹⁰Y and the radionuclide was linked with DOTA-chelate. This peptide receptor radionuclide therapy (PRRT) compound, ⁹⁰Y-DOTA-AR (bombesin antagonist) radiopeptide was followed by therapy with WST-11 (Weizmann STeba-11 drug; a negatively charged water-soluble palladium-bacteriochlorophyll derivative, Tookad^® Soluble) application. This VTP approach generates reactive oxygen/nitrogen species within tumor blood vessels, resulting in their instantaneous destruction and causes rapid tumor necrosis. Radionuclide emitting charged particle forms Cherenkov luminescence imaging (CLI) which can be used to monitor the retention of the accumulated ⁹⁰Y-PRRT. In this work, they demonstrated that the instantaneous arrest of tumor vasculature trapped radiopharmaceuticals in the vicinity of the tumor and thus improved the efficacy of targeted radiotherapy (1).