Abstract
The development of theranostic agents for radiopharmaceuticals based on therapeutic alpha emitters marks an important clinical need. We describe a strategy for the development of theranostic agents of this type via the functionalization of the ligand with the diagnostic radionuclide fluorine-18. An analogue of macropa, an 18-membered macrocyclic chelator with high affinity for alpha therapeutic radiometals, was synthesized and its complexation properties with metal ions were determined. The new macropa-F ligand was used for quantitative radiometal complexation with lead-203 and bismuth-207, as surrogates for their alpha-emitting radioisotopes. As a diagnostic partner, a radiofluorinated macropa ligand was used for quantitative bismuth(III) and lead(II) complexation. All fluorine-18 and radiometal complexes are highly stable in human serum over several days. This study presents a new proof-of-principle approach for developing theranostic agents based on alpha-emitting radionuclides and fluorine-18.