Wet harvesting of no-carrier-added ²¹¹At from an irradiated ²⁰⁹Bi target for radiopharmaceutical applications

Abstract

Astatine-211 is one of the most promising α-emitters for targeted cancer radiotherapy. However, research and clinical trials involving ²¹¹At-labeled radiopharmaceuticals have often been impeded due to the irregular and sometimes inconveniently low recovery yields obtained by the currently used dry distillation procedure. Therefore, a wet harvesting procedure isolating ²¹¹At from an irradiated ²⁰⁹Bi target was explored. The procedure involves target dissolution in concentrated HNO₃ and extraction of the high oxidation state ²¹¹At activity with butyl or isopropyl ether. This method resulted in consistent and nearly quantitative yields. The activity was re-extracted in aqueous phase and applied to NIS6 UVW human glioma cells transfected with cDNA encoding the human sodium/iodide symporter (NIS). The significant and specific uptake of ²¹¹At activity by these cells suggests that in the ether phase, high oxidation state ²¹¹At is reduced to [²¹¹At]astatide anion. The synthesis of the first astatinated organic compound derived from wet harvested ²¹¹At, 3-astatobenzoic acid (ABA), was achieved.