@article{oai:repo.qst.go.jp:00047380,
 author = {Xie, Lin and Maeda, Jun and Kumata, Katsushi and Yui, Joji and Zhang, Yiding and Hatori, Akiko and Nengaki, Nobuki and Wakizaka, Hidekatsu and Fujinaga, Masayuki and Yamasaki, Tomoteru and Shimoda, Yoko and Higuchi, Makoto and Suhara, Tetsuya and Wang, Feng and Zhang, Ming-Rong and 謝 琳 and 前田 純 and 熊田 勝志 and 由井 譲二 and 張 一鼎 and 羽鳥 晶子 and 念垣 信樹 and 脇坂 秀克 and 藤永 雅之 and 山崎 友照 and 下田 陽子 and 樋口 真人 and 須原 哲也 and 張 明栄},
 journal = {Scientific Reports (Online Only URL:http://www.nature.com/srep/index.html)},
 month = {Nov},
 note = {1-Methyl-tryptophan (1MTrp) is known as a specific inhibitor targeting the immune- checkpoint protein indoleamine-2,3-dioxygenase, in two stereoisomers of levorotary (l) and dextrorotary (d). A long-standing debate exists in immunology and oncology: which stereoisomer has the potential of antitumor immunotherapy. Herein, we developed two novel radioprobes, 1-N-(11)C-methyl-l- and -d-tryptophan ((11)C-l-1MTrp and (11)C-d-1MTrp), without modifying the chemical structures of the two isomers, and investigated their utility for pharmacokinetic imaging of the whole body. (11)C-l-1MTrp and (11)C-d-1MTrp were synthesized rapidly with radiochemical yields of 47 ± 6.3% (decay-corrected, based on (11)C-CO2), a radiochemical purity of >98%, specific activity of 47-130 GBq/μmol, and high enantiomeric purity. PET/CT imaging in rats revealed that for (11)C-l-1MTrp, the highest distribution of radioactivity was observed in the pancreas, while for (11)C-D-1MTrp, it was observed in the kidney. Ex vivo biodistribution confirmed the PET/CT results, indicating the differences in pharmacokinetics between the two isomers. Both (11)C-l-1MTrp and (11)C-d-1MTrp are therefore useful PET probes for delineating the distribution and action of the checkpoint inhibitor 1MTrp in vivo. This study represents the first step toward using whole-body and real-time insight to disentangle the antitumor potential of the two stereoisomers of 1MTrp, and it can facilitate the development of 1MTrp immunotherapy.},
 title = {Development of 1-N-(11)C-Methyl-l- and -d-Tryptophan for pharmacokinetic imaging of the immune checkpoint inhibitor 1-Methyl-Tryptophan.},
 volume = {5},
 year = {2015}
}