This review outlines the accomplishments and potential developments of targeted alpha (α) particle therapy (TAT). It discusses the therapeutic advantages of the short and highly ionizing path of α-particle emissions; the ability of TAT to complement and provide superior efficacy over existing forms of radiotherapy; the physical decay properties and radiochemistry of common α-emitters, including 225Ac, 213Bi, 224Ra, 212Pb, 227Th, 223Ra, 211At, and 149Tb; the production techniques and proper handling of α-emitters in a radiopharmacy; recent preclinical developments; ongoing and completed clinical trials; and an outlook on the future of TAT.
This study reports the high-yield production of a novel 133/135La theranostic pair at a 22 MeV proton beam energy as an attractive alternative to the recently introduced 132/135La pair, demonstrating over an order of magnitude production increase of 133/135La (231 ± 8 MBq 133La and 166 ± 5 MBq 135La at End of Bombardment (EOB)) compared to 11.9 MeV production of 132/135La (0.82 ± 0.06 MBq 132La and 19.0 ± 1.2 MBq 135La) 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 133La 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 133/135La, via natBa 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 68Ga, 44Sc and 132La, 133La 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.
Background
The radiometal gallium-68 (68Ga) is increasingly used in diagnostic positron emission tomography (PET), with 68Ga-labeled radiopharmaceuticals developed as potential higher-resolution imaging alternatives to traditional 99mTc agents. In precision medicine, PET applications of 68Ga are widespread, with 68Ga radiolabeled to a variety of radiotracers that evaluate perfusion and organ function, and target specific biomarkers found on tumor lesions such as prostate-specific membrane antigen, somatostatin, fibroblast activation protein, bombesin, and melanocortin.
Main body
These 68Ga radiopharmaceuticals include agents such as [68Ga]Ga-macroaggregated albumin for myocardial perfusion evaluation, [68Ga]Ga-PLED for assessing renal function, [68Ga]Ga-t-butyl-HBED for assessing liver function, and [68Ga]Ga-PSMA for tumor imaging. The short half-life, favourable nuclear decay properties, ease of radiolabeling, and convenient availability through germanium-68 (68Ge) generators and cyclotron production routes strongly positions 68Ga for continued growth in clinical deployment. This progress motivates the development of a set of common guidelines and standards for the 68Ga radiopharmaceutical community, and recommendations for centers interested in establishing 68Ga radiopharmaceutical production.
Conclusion
This review outlines important aspects of 68Ga radiopharmacy, including 68Ga production routes using a 68Ge/68Ga generator or medical cyclotron, standardized 68Ga radiolabeling methods, quality control procedures for clinical 68Ga radiopharmaceuticals, and suggested best practices for centers with established or upcoming 68Ga radiopharmaceutical production. Finally, an outlook on 68Ga radiopharmaceuticals is presented to highlight potential challenges and opportunities facing the community.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.