Development of a High-Affinity PET Radioligand for Imaging Cannabinoid Subtype 2 Receptor
作者:Rareş-Petru Moldovan、Rodrigo Teodoro、Yongjun Gao、Winnie Deuther-Conrad、Mathias Kranz、Yuchuan Wang、Hiroto Kuwabara、Masayoshi Nakano、Heather Valentine、Steffen Fischer、Martin G. Pomper、Dean F. Wong、Robert F. Dannals、Peter Brust、Andrew G. Horti
DOI:10.1021/acs.jmedchem.6b00554
日期:2016.9.8
Cannabinoid receptors type 2 (CB2) represent a target with increasing importance for neuroimaging due to its upregulation under various pathological conditions. Encouraged by preliminary results obtained with [C-11](Z)-N-(3- (2-methoxyethyl)-4,5-dimethylthiazol-2(3H)-ylidene)-2,2,3,3-tetramethyl-cyclopropanecarboxamide ([C-11]A-836339, [C-11]1) in a mouse model of acute neuroinflammation (induced by lipopolysaccharide, LPS), we designed a library of fluorinated analogs aiming for an [F-18]-labeled radiotracer with improved CB2 binding affinity and selectivity. Compound (Z)-N-(3-(4-fluorobutyl)-4,5-dimethylthiazol-2(3H)-ylidene)-2,2,3,3-tetramethyl-cyclopropanecarboxamide (29) was selected as a ligand with the highest CB2 affinity (K-i = 0.39 nM) and selectivity over CB1 (factor 1000). [F-18]29 was prepared starting from the bromo precursor (53). Specific binding was shown in vitro whereas fast metabolism was observed in vivo in CD-1 mice. Animal PET revealed a brain uptake comparable to [C-11]1. In the LPS treated mice, a 20-30% higher uptake in brain was found in comparison to non-treated mice (n = 3, P < 0.05).