ON THE PREPARATION and PROPERTIES OF DIHEMATOPORPHYRIN ETHER, THE TUMOR‐LOCALIZING COMPONENT OF HPD*

Abstract
Abstract—A porphyrin mixture derived from hematoporphyrin and termed HPD (hematoporphyrin derivative) is used for localization and therapy of tumors. The major localizing component of HPD has been provisionally identified as a dihematoporphyrin ether (DHE). In this study, we describe HPLC procedures for analytical and preparative separation of HPD components. Optimal conditions for DHE formation were determined. A comparison of absorbance and fluorescence spectra in different solvents indicate that DHE aggregates are substantially more stable than are the analogous hematoporphyrin structures. Studies on the interaction between DHE and tumor cells indicate an initial binding of the drug at lipophilic membrane sites, followed by gradual relocation to intracellular loci.