Synthesis, radiolabeling and preclinical evaluation of a [ 11 C]GMOM derivative as PET radiotracer for the ion channel of the N-methyl-D-aspartate receptor
作者:Pieter J. Klein、Robert C. Schuit、Athanasios Metaxas、Johannes A.M. Christiaans、Esther Kooijman、Adriaan A. Lammertsma、Bart N.M. van Berckel、Albert D. Windhorst
DOI:10.1016/j.nucmedbio.2017.05.003
日期:2017.8
Introduction: Presently available PET ligands for the NMDAr ion channel generally suffer from fast metabolism. The purpose of this study was to develop a metabolically more stable ligand for the NMDAr ion channel, taking [C-11]GMOM ([C-11]1) as the lead compound.Methods: [C-11]1, its fluoralkyl analogue [F-18]PK209 ([F-18]2) and the newly synthesized fluorovinyloxy analogue [C-11]7b were evaluated ex vivo in male Wistar rats for metabolic stability. In addition, [C-11]7b was subjected to a biodistribution study and its affinity (K-i) and lipophilicity (logD(7.4)) values were determined.Results: The addition of a vinyl chain in the fluoromethoxy moiety did not negatively alter the affinity of [C-11]7b for the NMDAr, while lipophilicity was increased. Biodistribution studies showed higher uptake of [C-11]7b in forebrain regions compared with cerebellum. Pre-treatment with MK-801 decreased the overall brain uptake significantly, but not in a region-specific manner. 45 min after injection 78, 90 and 87% of activity in the brain was due to parent compound for and [C-11]1, [F-18]2 and [C-11]7b, respectively. In plasma, 26-31% of activity was due to parent compound.Conclusion: Complete substitution of the alpha-carbon increased lipophilicity to more favorable values. Substitution of one or more hydrogens of the alpha-carbon atom in the methoxy moiety improved metabolic stability. In plasma, more parent compound was found for [F-18]2 and [C-11]7b then for [C-11]1, although differences were not significant. At 45 min, significantly more parent [F-18]2 and [C-11]7b was measured in the brain compared with [C-11]1. (C) 2017 The Authors. Published by Elsevier Inc.