Calixarene-based ligands for Radium and Barium

Due to their high biological effectiveness and suitable half-lives, there is increased interest in using the radionuclides radium-223 and radium-224 for radiopharmaceutical applications. Xofigo ([223Ra]radium chloride) is a bone-seeking, alpha-emitting radiopharmaceutical with EMA and FDA approval. It is used to treat bone metastasis of castrate-resistant prostate cancer. To expand the possible applications for these promising radionuclides, it is necessary to stably bind the radionuclide within a chelator. Therefore, calixarene-based ligands have been synthesized, which show encouraging affinities to radium ions. In our recent studies, we have already presented the high potential of these ligands. Since radium and barium have similar chemistry, and therefore comparable affinities to our ligands, it is possible to create a matched pair for theragnostic approaches. The radionuclide barium-131 has a suitable physical half-life for therapeutic applications and the potential of being a SPECT nuclide.