Recommendations on the clinical application and future potential of α-particle therapy

This review comprehensively assesses the clinical applications and future potential of alpha-emitting radionuclides available for targeted alpha-particle therapy (TAT) in cancer treatment. The approval of radium-223 therapy in 2013 marked a significant advancement in alpha-emitting therapeutic radiopharmaceuticals, which are primarily used in treatment of prostate cancer. The EU SECURE project was introduced as a major initiative to enhance the sustainability and safety of medical alpha-emitting radionuclides production in Europe. This literature review was conducted by a multidisciplinary team on selected radionuclides, including actinium-225, bismuth-213, astatine-211, lead-212, terbium-149, radium-223 and thorium-227. These were selected based on their clinical significance, as identified in the EU PRISMAP project and subsequent literature searches. The review process involved searching major databases using specific keywords related to alpha-emitter therapy and was limited to articles in English. For each selected radionuclide, the physical characteristics, the radiochemistry, and the pre-clinical and clinical studies are explored. Actinium-225 is the most widely studied alpha emitter, with several preclinical and clinical studies on prostate cancer and neuroendocrine tumours. Other types of tumours (such as glioblastoma) still require preclinical and clinical development. Bismuth-213 bound to antibodies, peptides and nanobodies has shown optimal results in preclinical and clinical studies, with increased median survival and no significant toxicity. Astatine-211 differs from most other α-emitters relevant to TAT, since it yields one α-particle per decay. This offers certain translational advantages, including the simplification of radiation dosimetry calculations and quality control (QC). Lead-212 has the advantage of being an in situ generator with likely widespread availability. Although clinical data are limited, the findings are promising at this stage. The unconventional production of Terbium-149 is the primary reason it has not yet progressed to clinical trials. Overcoming this production obstacle would allow more detailed preclinical investigations. Optimal results with Thorium-227-labelled agents have been observed in preclinical studies, including delays in cellular growth, multiple double-strand breaks and complete regression. Intermediate phase I trial results have also been reported, demonstrating safety and tolerability, as well as an objective response rate of 25%.: The results highlight the advantages of alpha particles in targeting cancer cells with minimal radiation to normal tissue, emphasising the need for high specificity and stability in delivery mechanisms, as well as suggesting that the full clinical potential of alpha particle therapy remains unexplored. Theranostic approach and dosimetric evaluations still represent relevant challenges.