文章基本信息

标题：Development of 1-N-11C-Methyl-l- and -d-Tryptophan for pharmacokinetic imaging of the immune checkpoint inhibitor 1-Methyl-Tryptophan
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作者：Lin Xie ; Jun Maeda ; Katsushi Kumata 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2015
卷号：5
期号：1
DOI：10.1038/srep16417
语种：English
出版社：Springer Nature
摘要：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 -¹¹C-methyl- l - and - d -tryptophan (¹¹C- l -1MTrp and ¹¹C- d -1MTrp), without modifying the chemical structures of the two isomers, and investigated their utility for pharmacokinetic imaging of the whole body. ¹¹C- l -1MTrp and ¹¹C- d -1MTrp were synthesized rapidly with radiochemical yields of 47 ± 6.3% (decay-corrected, based on ¹¹C-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 ¹¹C- l -1MTrp, the highest distribution of radioactivity was observed in the pancreas, while for ¹¹C- 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 ¹¹C- l -1MTrp and ¹¹C- 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.