Studies of Hpd and Radiolabelled Hpd In-Vivo and In-Vitro

Successful tumor sterilization by Photodynamic Therapy (PDT) depends on delivery of a light dose appropriate for the concentration of photoactive HPD in the tumor at the time of irradiation. Since the concentration of HPD in target cells or tissues is an important determinant of response to PDT, we have radioactively labelled HPD with the positron emitter Copper-64 to allow non-invasive in-vivo quantitation of HPD concentration by external nuclear detectors. Imaging of HPD distribution is also made possible by Positron Emission Tomography (PET). Labelling with the pure gamma-emitting Copper-67 would permit standard nuclear scintigraphy or Single Photon Emmission Computed Tomography (SPECT) in patients, the longer half-life of 67Cu (58 hours compared to 13 hours for 64Cu) being advantageous in this application.