Synthesis and Evaluation of Radioligands for Imaging Brain Nociceptin/Orphanin FQ Peptide (NOP) Receptors with Positron Emission Tomography
作者:Victor W. Pike、Karen S. Rash、Zhaogen Chen、Concepción Pedregal、Michael A. Statnick、Yasuyuki Kimura、Jinsoo Hong、Sami S. Zoghbi、Masahiro Fujita、Miguel A. Toledo、Nuria Diaz、Susan L. Gackenheimer、Johannes T. Tauscher、Vanessa N. Barth、Robert B. Innis
DOI:10.1021/jm101487v
日期:2011.4.28
Positron emission tomography (PET) coupled to an effective radioligand could provide an important tool for understanding possible links between neuropsychiatric disorders and brain NOP (nociceptin/orphanin FQ peptide) receptors. We sought to develop such a PET radioligand. High-affinity NOP ligands were synthesized based on a 3-(2'-fluoro-4',5'-dihydrospiro[piperidine-4,7'-thieno[2,3-c]pyran]-1-yl)-2(2-halobenzyl)-N-alkylpropanamide scaffold and from experimental screens in rats, with ex vivo LC-MS/MS measures, three ligands were identified for labeling with carbon-11 and evaluation with PET in monkey. Each ligand was labeled by C-11-methylation of an N-desmethyl precursor and studied in monkey under baseline and NOP receptor-preblock conditions. The three radioligands, [C-11] (S) 10a-c, gave similar results. Baseline scans showed high entry of radioactivity into the brain to give a distribution reflecting that expected for NOP receptors. Preblock experiments showed high early peak levels of brain radioactivity, which rapidly declined to a Much lower level than seen in baseline scans, thereby indicating a high level of receptor-specific binding in baseline experiments. Overall, [C-11](S)-10c showed the most favorable receptor-specific signal and kinetics and is now selected for evaluation in human subjects.