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-enriched168Er2O3. 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 separating169Er from168Er 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 pure169Er. The quality of the169Er product permitted radiolabeling and pre-clinical studies. A preliminaryin vitroexperiment was accomplished, using a169Er-PSMA-617, to show the potential of169Er to reduce tumor cell viability.