RT Journal Article SR Electronic T1 Radiosynthesis, Photoisomerization, Biodistribution, and Metabolite Analysis of 11C-PBB3 as a Clinically Useful PET Probe for Imaging of Tau Pathology JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1532 OP 1538 DO 10.2967/jnumed.114.139550 VO 55 IS 9 A1 Hiroki Hashimoto A1 Kazunori Kawamura A1 Nobuyuki Igarashi A1 Makoto Takei A1 Tomoya Fujishiro A1 Yoshiharu Aihara A1 Satoshi Shiomi A1 Masatoshi Muto A1 Takehito Ito A1 Kenji Furutsuka A1 Tomoteru Yamasaki A1 Joji Yui A1 Lin Xie A1 Maiko Ono A1 Akiko Hatori A1 Kazuyoshi Nemoto A1 Tetsuya Suhara A1 Makoto Higuchi A1 Ming-Rong Zhang YR 2014 UL http://jnm.snmjournals.org/content/55/9/1532.abstract AB 2-((1E,3E)-4-(6-(11C-methylamino)pyridin-3-yl)buta-1,3-dienyl)benzo[d]thiazol-6-ol (11C-PBB3) is a clinically useful PET probe that we developed for in vivo imaging of tau pathology in the human brain. To ensure the availability of this probe among multiple PET facilities, in the present study we established protocols for the radiosynthesis and quality control of 11C-PBB3 and for the characterization of its photoisomerization, biodistribution, and metabolism. Methods: 11C-PBB3 was synthesized by reaction of the tert-butyldimethylsilyl desmethyl precursor (1) with 11C-methyl iodide using potassium hydroxide as a base, followed by deprotection. Photoisomerization of 11C-PBB3 under fluorescent light was determined. The biodistribution and metabolite analysis of 11C-PBB3 was determined in mice using the dissection method. Results: 11C-PBB3 was synthesized with 15.4% ± 2.8% radiochemical yield (decay-corrected, n = 50) based on the cyclotron-produced 11C-CO2 and showed an averaged synthesis time of 35 min from the end of bombardment. The radiochemical purity and specific activity of 11C-PBB3 were 98.0% ± 2.3% and 180.2 ± 44.3 GBq/μmol, respectively, at the end of synthesis (n = 50). 11C-PBB3 showed rapid photoisomerization, and its radiochemical purity decreased to approximately 50% at 10 min after exposure to fluorescent light. After the fluorescent light was switched off, 11C-PBB3 retained more than 95% radiochemical purity over 60 min. A suitable brain uptake (1.92% injected dose/g tissue) of radioactivity was observed at 1 min after the probe injection, which was followed by rapid washout from the brain tissue. More than 70% of total radioactivity in the mouse brain homogenate at 5 min after injection represented the unchanged 11C-PBB3, despite its rapid metabolism in the plasma. Conclusion: 11C-PBB3 was produced with sufficient radioactivity and high quality, demonstrating its clinical utility. The present results of radiosynthesis, photoisomerization, biodistribution, and metabolite analysis could be helpful for the reliable production and application of 11C-PBB3 in diverse PET facilities.