Journal Article Synthesis and Evaluation of Novel Radioligands Based on 3-[5-(Pyridin-2-yl)-2H-tetrazol-2-yl]benzonitrile for Positron Emission Tomography Imaging of Metabotropic Glutamate Receptor Subtype 5

Shimoda, Yoko  ,  Yamasaki, Tomoteru  ,  Fujinaga, Masayuki  ,  Ogawa, Masanao  ,  Kurihara, Yusuke  ,  Nengaki, Nobuki  ,  Kumata, Katsushi  ,  Yui, Joji  ,  Hatori, Akiko  ,  Xie, Lin  ,  Zhang, Yiding  ,  Kawamura, Kazunori  ,  Ming-Rong, Zhang

59 ( 8 )  , pp.3980 - 3990 , 2016-04 , ELSEVIER
We found out 3-[5-(pyridin-2-yl)-2H-tetrazol-2-yl]benzonitrile analogues as the candidate for positron emission tomography (PET) imaging agents of metabotropic glutamate receptor subtype 5 (mGluR5). Among these compounds, 3-methyl-5-(5-(pyridin-2-yl)-2H-tetrazol-2-yl)benzonitrile (10) exhibited high binding affinity (Ki = 9.4 nM) and moderate lipophilicity (cLogD, 2.4). Subsequently, [11C]10 was radiosynthesized at 25 ± 14% radiochemical yield (n = 11) via C-[11C]methylation of the arylstannyl precursor 15 with [11C]methyl iodide. In vitro autoradiography and PET assessments using [11C]10 showed high specific binding in the striatum and hippocampus, two brain regions enriched with mGluR5. Moreover, test–retest PET studies with [11C]10 indicated high reliability to quantify mGluR5 density, such as the intraclass correlation coefficient (0.90) and Pearson r (0.91) in the striatum of rat brain. We demonstrated that [11C]10 is a useful PET ligand for imaging and quantitative analysis of mGluR5. Furthermore, [11C]10 might be modified using its skeleton as a lead compound.

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