Potential 166Ho radiopharmaceuticals for intravascular radiation therapy (IVRT)-I : [166Ho] holmium labeled ethylene dicysteine

The use of beta (-) emitting radionuclides in the control of restenosis in post angioplasty patients is currently under intense investigation at many leading cardiovascular research centers. P-32 coated metallic stents, Ir-192 wire source and balloons filled with an appropriate radionuclide solution such as of Re-188, attached to catheter are being studied. Ho-166 has comparable radionuclidic properties to that of Re-188, can be more easily produced and hence is an attractive alternative to Re-188. Ethylene dicysteine complex of Ho-166 was prepared and its pharmacological behavior studied. Optimum conditions for the preparation of complex with respect to the reaction time, ligand concentration, pH of the reaction mixture as well as reaction temperature were standardized. The stability of the labeled complex at room temperature as well as at 4 degreesC was determined. Biodistribution pattern of the injected complex in Wistar rats was estimated at 10 min, 30 min and 3 h post injection. This study indicated that >90% of the injected Ho-166-EC complex was excreted in urine within 3 h post injection, with insignificant retention in any major organ. These studies reveal that Ho-166-EC could be a viable substitute for Re-188 compounds in radioactive liquid-filled balloon IVRT. (C) 2001 Elsevier Science Inc. All rights reserved.