Research and Development for Cyclotron Production of225Ac from226Ra—The Challenges in a Country Lacking Natural Resources for Medical Applications

Abstract

The high therapeutic effect of targeted radioisotope/radionuclide therapy (TRT) using αemitters, especially225Ac, is attracting attention worldwide. However, the only225Ac production method that has been put into practical use is extraction from a229Th generator derived from the nuclear fuel233U, and it is unlikely that this method alone is able to meet future global medical demand. Development towards new225Ac production methods is in progress. These new225Ac production methods require the irradiation of232Th or226Ra using an accelerator or a nuclear reactor. Global competition has already begun in the race to secure a reliable supply of232Th and226Ra, as well as229Th for the conventional production method. Japan is a “resource-poor country” that depends on foreign countries for most of its needs. As such, it is difficult for Japan to secure raw materials such as232Th and226Ra for medical application. In this paper, we look back on our research at the National Institutes for Quantum Science and Technology (QST) in the fields of225Ac production and225Ac-labeled pharmaceutical development. We present the history and details of our research from 2011, as well as the development of a collaboration between QST and Nihon Medi-Physics that focuses on research into225Ac production via226Ra(p,2n)225Ac reaction using an accelerator. Furthermore, we review the valuable discussion at the 2018 Joint IAEA-JRC Workshop—“Supply of Actinium-225”, an international conference that we participated in. Overall, the statuses of external225Ac supply, domestic production, and distribution are discussed, as are the latest developments in225Ac production methods,225Ac pharmaceuticals, and future prospects for the domestic production of225Ac in Japan, a country lacking natural resources for medical applications.