Development of GSK-3beta PET radioligands for in vivo imaging in brain

糖原合成酶-3(GSK-3或β)的功能障碍与中枢神经系统疾病的发病机制有关。 神经系统疾病，如双相情感障碍、精神分裂症、阿尔茨海默病和帕金森氏症 是一种疾病，也是治疗发展的目标。这项提议的目标是开发GSK-3正电子 放射断层成像(PET)显像剂在啮齿动物和猴子脑中的活体评价 促进其成功地转化为诊断、治疗监测和药物的临床研究 发展。一种用于GSK-3激酶的PET成像的放射性示踪剂可用于研究其在 作为小分子发展的一部分，精神障碍和加速目标占有率研究 GSK-3的抑制剂作为治疗药物。目前还没有有效的PET示踪剂可用于体内 脑组织中GSK-3的监测。因此，我们建议开发用于PET成像的特定放射性示踪剂GSK-3和 我选择了1-(7-methoxyquinolin-4-yl)-3-(6-(trifluoromethyl)pyridin-2-yl)urea(A1070722)作为第一个 从一组四个结构不同的GSK-3配体中进行测试的候选者(图2)。A1070722是一款高亲和力 (Ki=0.6 nM)和具有良好的对数P(3.2)的GSK-3选择性配体对血脑屏障(BBB)的穿透作用。 已知A1070722可以进入大脑，减少微管相关蛋白Tau的磷酸化。我们 合成了[11C]A1070722([11C]1，产率40%；纯度98%)，在这个应用中，我们建议评估 [11C]A1070722在脑内的分布与[11C]1的PET评估平行 大鼠，两个高选择性的二氢-~3H-吡唑-3-基于GSK-3的配体2和3和一个高亲和力 将合成恶二氮苯腈配体(4)作为后备候选配体。后备配体将是 进一步测定它们对GSK-3的选择性。基于特定的标准，包括对GSK-3的亲和力 相对于其他靶点，候选者将被放射性标记，它们在体内结合GSK-3的能力将是 用microPET成像法在大鼠体内测定。这些研究将证明血脑屏障的渗透性，大脑 在大鼠体内的分布、稳定性、特异性结合和示踪清除。然后，最佳候选人将是 对猴子进行PET研究，以确定更详细的脑分布、特异性结合 相对于非特异性结合和示踪剂动力学建模。将使用猴子研究中的重测数据 选择一种确定结果度量的最佳方法。圆满完成拟议中的 研究将有助于确定利用PET成像对体内GSK-3进行定量的有价值的工具 在正常脑组织中几种主要脑部疾病的发病机制及治疗新进展 针对GSK-3的治疗。

Dysfunction of glycogen synthase-3 (GSK-3 or ser9-pGSK3β) has been linked to the etiology of central nervous system diseases such as bipolar disorder, schizophrenia, Alzheimer's disease and Parkinson's disease and is a target for therapeutic development. The goal of this proposal is to develop a GSK-3 positron emission tomography (PET) imaging agent for in vivo evaluation in rodent and monkey brains in order to facilitate its successful translation into clinical studies of diagnosis, treatment monitoring and drug development. A radiotracer for PET imaging of the GSK-3 kinase could be used both for study of its role in psychiatric disorders and accelerate target occupancy studies as part of the development of small molecule inhibitors of GSK-3 as therapeutic agents. At present there is no validated PET tracer available for the in vivo monitoring of GSK-3 in brain. Hence we propose to develop specific radiotracers for PET imaging GSK-3 and have selected 1-(7-methoxyquinolin-4-yl)-3-(6-(trifluoromethyl)pyridin-2-yl)urea (A1070722) as the first candidate for testing from a set of four structurally diverse GSK-3 ligands (Figure 2). A1070722 is a high affinity (Ki = 0.6 nM) and selective ligand for GSK-3 with favorable logP (3.2) for blood brain barrier (BBB) penetration. A1070722 is known to enter brain and reduces phosphorylation of microtubule-associated protein Tau. We synthesized [11C]A1070722 ([11C]1, > 40% yield; > 98% purity) and in this application we propose to evaluate the in vivo distribution of [11C]A1070722 in brain by PET imaging. Parallel to the PET evaluation of [11C]1 in rats, two highly selective dihydro-3H-pyrazol-3-on based GSK-3 ligands 2 & 3 and a high affinity oxadiazabenzonitrile ligand (4) will be synthesized as back-up candidate ligands. The back-up ligands will be further assayed to determine their selectivity to GSK-3. Based on specified criteria including affinity for GSK-3 relative to other targets, the candidates will be radiolabeled and their in vivo ability to bind GSK-3 will be determined in rats in vivo with microPET imaging. These studies will prove the BBB permeability, brain distribution, in vivo stability, specific binding and tracer clearance in rats. The optimal candidate will then be advanced to PET studies in monkeys for determination of more detailed brain distribution, specific binding relative to nonspecific binding and tracer kinetic modeling. Test-retest data from the monkey study will be used to choose an optimal method for determining the outcome measure. Successful completion of the proposed studies would lead to the identification of a valuable tool for in vivo quantification of GSK-3 using PET imaging in the normal brain and pathogenesis of several major brain disorders and development of new therapeutic treatments targeting GSK-3.