Structure–Affinity Relationships of 2,3,4,5-Tetrahydro‑1<i>H</i>‑3-benzazepine and 6,7,8,9-Tetrahydro‑5<i>H</i>‑benzo[7]annulen-7-amine Analogues and the Discovery of a Radiofluorinated 2,3,4,5-Tetrahydro‑1<i>H</i>‑3-benzazepine Congener for Imaging GluN2B Subunit-Containing <i>N</i>‑Methyl‑d‑aspartate Receptors

Aspiring to develop a positron emission tomography (PET) imaging agent for the GluN2B subunits of the N-methyl-d-aspartate receptor (NMDAR), a key therapeutic target for drug development toward several neurological disorders, we synthesized a series of 2,3,4,5-tetrahydro-1H-3-benzazepine and 6,7,8,9-tetrahydro-5H-benzo­[7]­annulen-7-amine analogues. After in vitro testing via competition binding assay and autoradiography, [18F]­PF-NB1 emerged as the best performing tracer with respect to specificity and selectivity over σ1 and σ2 receptors and was thus selected for further in vivo evaluation. Copper-mediated radiofluorination was accomplished in good radiochemical yields and high molar activities. Extensive in vivo characterization was performed in Wistar rats comprising PET imaging, biodistribution, receptor occupancy, and metabolites studies. [18F]­PF-NB1 binding was selective to GluN2B-rich forebrain regions and was specifically blocked by the GluN2B antagonist, CP-101,606, in a dose-dependent manner with no brain radiometabolites. [18F]­PF-NB1 is a promising fluorine-18 PET tracer for imaging the GluN2B subunits of the NMDAR and has utility for receptor occupancy studies.本研究旨在开发针对N-甲基-D-天冬氨酸受体（N-methyl-d-aspartate receptor, NMDAR）GluN2B亚基的正电子发射断层显像（positron emission tomography, PET）显像剂——该受体是多种神经系统疾病药物研发的关键治疗靶点——我们合成了一系列2,3,4,5-四氢-1H-3-苯并氮杂䓬及6,7,8,9-四氢-5H-苯并[7]环庚烯-7-胺类衍生物。经竞争结合实验（competition binding assay）与放射自显影（autoradiography）完成体外筛选后，[¹⁸F]­PF-NB1展现出最优的特异性与对σ1和σ2受体（σ1 and σ2 receptors）的选择性，因此被选中开展进一步的体内评价。铜介导的放射性氟化（copper-mediated radiofluorination）反应取得了良好的放化产率（radiochemical yields）与较高的摩尔活度（molar activities）。我们在Wistar大鼠（Wistar rats）中完成了全面的体内表征，涵盖PET显像、生物分布（biodistribution）、受体占位（receptor occupancy）及代谢物研究（metabolites studies）。[¹⁸F]­PF-NB1的结合具有GluN2B富集前脑区域的特异性，且可被GluN2B拮抗剂CP-101,606以剂量依赖性方式特异性阻断，同时未检出脑部放射性代谢物。[¹⁸F]­PF-NB1是一款极具潜力的氟-18（fluorine-18）标记PET显像剂，可用于靶向NMDAR GluN2B亚基的显像，同时适用于受体占位研究。