High yield cyclotron production of a novel 133/135La theranostic pair for nuclear medicine

This study reports the high-yield production of a novel 133/135 La theranostic pair at a 22 MeV proton beam energy as an attractive alternative to the recently introduced 132/135 La pair, demonstrating over an order of magnitude production increase of 133/135 La (231 ± 8 MBq 133 La and 166 ± 5 MBq 135 La at End of Bombardment (EOB)) compared to 11.9 MeV production of 132/135 La (0.82 ± 0.06 MBq 132 La and 19.0 ± 1.2 MBq 135 La) for 500 µA·min irradiations. A new sealed solid cyclotron target is introduced, which is fast to assemble, easy to handle, storable, and contains reusable components. Radiolabeling with macrocyclic chelators DOTA and macropa achieved full incorporation, with respective apparent 133 La molar activites of 33 ± 5 GBq/µmol and 30 ± 4 GBq/µmol. PET centers with access to a 22 MeV capable cyclotron could produce clinically-relevant doses of 133/135 La, via nat Ba irradiation, as a standalone theranostic agent for PET imaging and Auger electron therapy. With lower positron energies and less energetic and abundant gamma rays than 68 Ga, 44 Sc and 132 La, 133 La appears to be an attractive radiometal candidate for PET applications requiring a higher scanning resolution, a relatively long isotopic half-life, ease of handling, and a low patient dose.