Positive Allosteric Modulators as PET Imaging Ligans for mGluR4

摘要：50万美国人患有帕金森病(PD)，由此产生的医疗费用是 一年60亿美元。还有其他几种神经疾病的治疗费用非常高， 但在这种情况下，重点放在与谷氨酸有很强联系的紊乱上 神经传递。突触前mGlu4的定位使其成为谷氨酸的重要贡献者 由于谷氨酸和多巴胺从神经元的突触前部位释放出来，所以神经传递 而激活mGlu4可以抑制谷氨酸和GABA等神经递质的释放，从而 帕金森病患者通过直接和间接途径平衡神经传递。最近的一些出版物提出了 尤其是mGlu4作为包括帕金森病在内的不同神经系统疾病的治疗靶点。我们有广泛的 研究了正变构调节剂(PAM)作为mGlu4的PET成像配体。我们还调查了 用药理学核磁共振方法研究所开发的化合物的生物活性。这些研究 开辟了一种新的方法来表征化合物并探索其治疗目的的可用性。我们 基于两种不同化学类型的mGlu4 PAM合成了32种不同的化合物。其中六个 这些化合物已被体内研究表征为mGlu4的PET成像配体。主 我们开发的配体的局限性是快速洗脱和新陈代谢，尽管结合亲和力很强 一直都很体面。我们还开发了表达mGlu4的特定细胞系，并进行了细胞研究 确定我们的结构-亲和关系(SAR)的配基表征的基础 实验PAMS与测定内源性谷氨酸结合的协同关系 变构调节剂的正构体结合部位和亲和力。这些方法与 正构体配体与内源配体在同一结合部位竞争的经典方法。 基于开创性的工作和全球的兴趣，我们正在寻找开发特别是氟-18 MGlu4的标记阳性变构成像配体允许医学应用和分布 配基。准确地说，在目标1中，我们建议从N-18标记的铅化合物中合成两个F-18标记的先导化合物。 苯基吡啶甲酰胺和噻唑并吡唑为基础的mGlu4 PAM研究其成像效果，Bmax， 具有选择性、脑渗透性、药代动力学、代谢稳定性等特性。在《目标2》中我们将 合成了8个新的含氟N-苯基吡啶甲酰胺类化合物和12个含氟N-苯基吡啶甲酰胺类化合物. 含有用于合成孔径雷达分析的噻唑并吡唑衍生物。这项工作将由计算支持 化学反应。将选择两个最佳化合物作为mGlu4的PET成像配体进行开发。在……里面 目的3我们将使用mGlu4基因敲除的小鼠、大鼠和灵长类动物对这些配体进行体内表征 最终目标是验证用于人体研究的最佳化合物并获得IND批准的模型。

ABSTRACT: Half a million Americans suffer from Parkinson’s disease (PD) and the incurring health cost is $6 billion in a year. There are several other neurological disorders with extremely high cost for treatment, but in this context the focus is on the disorders, which have strong connection to glutamate neurotransmission. Presynaptic location of mGlu4 makes them important contributors for glutamate neurotransmission since glutamate as well as dopamine is released from the presynaptic site of the neuron and activation of mGlu4 can inhibit the release of neurotransmitters such as glutamate and GABA and thus balance neurotransmission through direct and indirect pathways in PD. Several recent publications propose especially mGlu4 as therapeutic target for different neurological diseases including PD. We have extensively investigated positive allosteric modulators (PAMs) as PET imaging ligands for mGlu4. We investigated also biological activity of the developed compounds using pharmacological MRI approaches. These studies opened a new way to characterize compounds and explore their usability for therapeutic purposes. We have synthetized 32 different compounds based on two different chemo-types of the mGlu4 PAMs. Six of these compounds have been characterized with in vivo studies as PET imaging ligands for mGlu4. The main limitation in our developed ligands has been fast washout and metabolism, even though binding affinities have been decent. We also developed specific cell lines to express mGlu4 and the cell studies have been fundamental in ligand characterization to determine the structure-affinity relationship (SAR) of our experimental PAMs and determine co-operative relationship between endogenous glutamate binding to orthosteric binding sites and affinity of allosteric modulators. These approaches are radically different from classical approach in which orthosteric ligands compete with endogenous ligands at the same binding site. Based on the pioneering work and worldwide interest we are looking for to develop especially fluorine-18 labeled positive allosteric imaging ligands for mGlu4 allowing medical applications and distribution of the ligands. Precisely, in Aim 1 we are proposing to synthesize two F-18 labeled lead compounds from the N- phenylpicolinamide- and thiazolopyrazole-based mGlu4 PAMs to study their imaging efficacy, Bmax, selectivity, brain penetration, pharmacokinetics, metabolic stability and other properties. In Aim 2 we will synthesize new series of eight fluorine-containing N-phenylpicolinamide derivatives and twelve fluorine- containing thiazolopyrazole derivatives for SAR analyses. This effort will be supported by computational chemistry. Two best compounds will be selected for the development as PET imaging ligands for mGlu4. In Aim 3 we will conduct in vivo characterization of these ligands using mGlu4 knockout mice, rat and primate models with an ultimate goal to validate the best compound for human studies and obtain IND approval.