These researchers are always looking for new methods of conducting treatment, for which a promising option is astatine-211, known as 211At, which emits an alpha particle and thus has shown great promises in radionuclide therapy. Many landmarks have been obtained in the productions and applications of this radionuclide in research centers, but Japan took the lead in this area.
Production of Astatine-211 in Japan
Then, Japan started scrambling in the back for astatine-211. After the Fukushima nuclear accident in 2011, the country tightened its laws on atomic reactors very seriously. A policy shift and growing public unease over nuclear power reduced the available capacity to supply the material needed for the conventional production process of medical radionuclides.
However, the Japanese government has also facilitated the production of other devices for this purpose. For example, there has been a development where, in the country, five facilities are currently using cyclotron accelerators to generate astatine-211, including Osaka University and FMU. With that plan, Japan took the lead in conducting research to apply astatine-211 in medicine.
The Promise of Alpha Particle Therapy
Astatine-211 is a very promising nuclide for α particle-emitting radiotherapeutic applications against cancer. In fact, α radiation is five times more potent than the β or γ radiations usually used at the same doses. It has an increased ability to damage the DNA inside cancer cells and is therefore quite potent in fighting cancer.
But special challenges exist in using alpha particles in radiation therapy. Unlike other forms of radiotherapy, alpha particles do not go through and further than the skin and hence must be given intravenously or be injected into affected tissues directly. Because of this drawback, various targeting methods had to be devised to facilitate the reaching of target cancer cells effectively.
Targeting Specific Cancers
Japanese researchers are exploring various methods to target specific types of cancer using astatine-211:
- Thyroid cancer: Scientists at Osaka University in Japan are working on targeting thyroid cancer cells based on chemical similarities of astatine and iodine. In a manner similar to treatments being given today with iodine-131, scientists can target thyroid cancer cells by using a simple ionic form of astatine-211. “It could be particularly valuable for those patients whose cancers have become resistant to regular radioiodine therapy,”.
- Prostate cancer: The Osaka group is using astatine-211 to attach to a very small peptide molecule. The resultant compound is taken up selectively in the prostate membrane, which provides targeted treatment to the disease.
- Neuroendocrine tumors: In the case of the rather rare neuroendocrine tumors—namely, pheochromocytomas—one has found encouraging success in animal studies. Here, one uses astatine-211 bound to a norepinephrine analog; the uptake by the cancer cells is due to having more of a special type of transporter protein.
Clinical Trials and Future Prospects
Real-world application comes next. An example of current big effort is the phase I clinical trial for thyroid cancer treatment with astatine-211, of which its results are expected to be delivered in March 2025 for the determination of important factors of safety and best dosage in future Phase II trials.
Clinical trials for such use against prostate cancer are set to start in 2024, say researchers who have joined the project after good results in animal experiments. There is also a clinical trial at Fukushima Medical University on the treatment of pheochromocytomas by injection of astatine-211 compounds.
Infrastructure and Collaboration
The very short half-life of astatine-211 is 7.2 hours, involving the necessity for local production facilities near centers of treatment. Japan has risen to this challenge by establishing appropriate production sites throughout the country. This not only guarantees a regular supply of the radionuclide but also diminishes dependency on expensive imported materials.
The decision of the Japanese government to implement it, by establishing the F-REI in April 2023, shows a serious commitment in this area. This Japanese government effort is aimed at supporting scientific innovations in Fukushima through united efforts on both radionuclide production and clinical research.
Conclusion
Research on astatine-211 is a bold step toward strategic focusing by Japan in treating cancer. All the technological know-how and innovative spirit that this country possesses has helped it, up until now, to find a place among the leading countries concerned with this promising area of study. While its clinical trials progress and new applications are found, so does astatine-211’s great potential increase to fight cancer, hence giving patients and researchers hope.
The next few years will be important in determining its full impact. One thing, however, is already clear: Japan’s investment into production and research of astatine-211 has opened exciting new vistas in the continuing fight against cancer.
