Production of Mass-Separated Erbium-169 Towards the First Preclinical in vitro Investigations

The β(−)-particle-emitting erbium-169 is a potential radionuclide toward therapy of metastasized cancer diseases. It can be produced in nuclear research reactors, irradiating isotopically-enriched (168)Er(2)O(3). This path, however, is not suitable for receptor-targeted radionuclide therapy, where high specific molar activities are required. In this study, an electromagnetic isotope separation technique was applied after neutron irradiation to boost the specific activity by separating (169)Er from (168)Er targets. The separation efficiency increased up to 0.5% using resonant laser ionization. A subsequent chemical purification process was developed as well as activity standardization of the radionuclidically pure (169)Er. The quality of the (169)Er product permitted radiolabeling and pre-clinical studies. A preliminary in vitro experiment was accomplished, using a (169)Er-PSMA-617, to show the potential of (169)Er to reduce tumor cell viability.