Production of ィイD1105ィエD1Rh and application of this nuclide to therapeutic radiopharmaceuticals

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Rhodium-105(ィイD1105ィエD1Rh) has favorable physical characteristics as a radiotherapeutic nuclide. Carrier-free ィイD1105ィエD1Rh can be produced by the neutron activation of ィイD1104ィエD1Ru followed by beta decay of ィイD1105ィエD1Ru. It was clarified that carrier-free ィイD1105ィエD1Rh can be produced in quantities and the purity necessary for chemical and clinical investigations of its use as a nuclide for radiotherapy.ィイD157ィエD1Co-bleomycin is selectively accumulated in some cancer. However, the long half-life of ィイD157ィエD1Co(270 days) poses contamination problems which preclude its widespread clinical use. Kono suggested from the similarity of chemical property between cobalt and rhodium and from the in vitro study that Rh-bleomycin would have tumor affinity. Bleomycin-hydrochloride was added the solution of ィイD1105ィエD1Rh(II) and heated for 5 min in boiling water. ィイD1105ィエD1Rh-bleomycin(BLM) was separated from the reaction mixture by thin-layer chromatography on silica gel plate using the solvent system, MeOH : 10% CHィイD23ィエD2COONHィイD24ィエD2 in HィイD22ィエD20(1:1). Tumor affinity of ィイD1105ィエD1Rh-BLM was examined with Ehrlich tumor-bearing mice. In this experiment, ィイD1105ィエD1Rh-BLM did not accumulated in tumor tissue.On the other hand, we produced ィイD1105ィエD1Rh-EDTMP for therapeutic bone agent. ィイD1105ィエD1Rh-EDTMP was simply obtained from ィイD1105ィエD1RhィイD13+ィエD1 and EDTMP by heating for 30 min in boiling water, giving a radiochemical yield of > 99 %. Dissociation of radioactivity assessed by paperchromatography was negligible for up to 5 days after its preparation. In animals, ィイD1105ィエD1Rh-EDTMP showed rapid blood clearance and selective uptake in the bone.Hence, ィイD1105ィエD1Rh-EDTMP is thought to be a promising therapeutic agent for the treatment of pain due to bone metastases.