Speaker
Description
Astatine-211 with the half-life of T1/2 = 7.214 h is one of the promising radionuclides for targeted α-particle therapy (TAT) [1]. The 5.87- and 7.45-MeV α-particle emissions occur in intensities of 41.8% and 58.2%, respectively, associated with the 211At decay. Due to the proper ranges of these α-particles in tissue, the 211At-labeled medicine is effective in killing cancer cells. 211At is produced in the 209Bi(α,2n)211At reaction. Since 2015, we have been developing an 211At production system on the beam line of the RIKEN AVF cyclotron [2-5]. The metallic 209Bi target (20 mg/cm2) is irradiated by the 28-MeV α beam from AVF. The typical beam intensity is 25 particle μA (pμA). Under our current experimental condition, 1.2 GBq of 211At can be produced in 1-h irradiation. The irradiated 209Bi target is placed in a quartz tube and heated up to 850°C. 211At sublimated from the target is transported from the quartz tube to a cold PFA tube (–96°C) by O2 gas flow (10 mL/min). After the distillation, the PFA tube is washed with CHCl3 (300–400 μL) which is then dried up by N2 gas (100 mL/min). The typical chemical yield of 211At is 80%.
We are distributing 211At to about 20 universities, research institutes, and companies, where radiolabelling and animal experiments are ongoing to develop novel radiopharmaceuticals for cancer therapy. Our 211At has been supplied to Osaka University Hospital since 2016, and in 2022, the Japan's first clinical trial of TAT for refractory differentiated thyroid cancer has been initiated.
In January 2020, RIKEN heavy-ion Linear ACcelerator (RILAC) was upgraded with the 28-GHz superconducting ECR ion source and the superconducting RILAC (SRILAC) [6]. SRILAC is expected to generate high intensity α beams of >100 pμA. We are developing a large-scale production technology of 211At using a liquid 209Bi target in a rotating cup in collaboration with Metal Technology Co. Ltd., Japan.
References
[1] Y. Feng and M. R. Zalutsky, Nucl. Med. Biol. 100–101, 12 (2021).
[2] S. Yano et al., RIKEN Accel. Prog. Rep. 50, 261 (2017).
[3] N. Sato et al., RIKEN Accel. Prog. Rep. 50, 262 (2017).
[4] Y. Wang et al., RIKEN Accel. Prog. Rep. 53, 192 (2020).
[5] H. Haba, Drug Deliv. Syst. 35, 114 (2020) (in Japanese).
[6] N. Sakamoto and T. Nagatomo, Nucl. Phys. News 32, 21 (2022).
| Themes for the contribution | 8 Multipurpose use of targets and beam dumps: |
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