Positive Allosteric Modulators as PET Imaging Ligans for mGluR4

摘要：美国有50万人患有帕金森病，其医疗费用是 一年60亿还有其他几种治疗费用极高的神经系统疾病， 但在这种情况下，重点是与谷氨酸盐密切相关的疾病， 神经传递mGlu 4的突触前位置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， mGlu 4的激活可以抑制神经递质如谷氨酸和GABA的释放， 通过直接和间接途径平衡PD中的神经传递。最近的一些出版物提出， 特别是mGlu 4作为包括PD在内的不同神经系统疾病的治疗靶点。我们广泛 研究了正变构调节剂（PAM）作为mGlu 4的PET成像配体。我们还调查了 使用药理学MRI方法的开发的化合物的生物活性。这些研究 开辟了表征化合物并探索其用于治疗目的的可用性的新途径。我们 基于mGlu 4 PAM的两种不同化学类型合成了32种不同的化合物。六 这些化合物已经通过体内研究表征为mGlu 4的PET成像配体。主要 我们开发的配体的限制是快速洗脱和代谢，即使结合亲和力 都很得体我们还开发了表达mGlu 4的特异性细胞系，细胞研究已被证实。 配体表征的基础，以确定我们的结构-亲和关系（SAR） 实验性PAM，并确定内源性谷氨酸结合与 正构结合位点和别构调节剂的亲和力。这些方法完全不同于 经典的方法，其中正构配体与内源性配体在相同的结合位点竞争。 基于开创性的工作和世界范围内的兴趣，我们正在寻找开发特别是氟-18 标记的mGlu 4的正变构成像配体，其允许医疗应用和分布， 配体。准确地说，在目标1中，我们提出从N-甲基-N- 基于苯基吡啶酰胺和噻唑并吡唑的mGlu 4 PAM，以研究其成像功效，Bmax， 选择性、脑渗透性、药代动力学、代谢稳定性和其它性质。在目标2中， 合成了新系列八种含氟N-苯基吡啶酰胺衍生物和十二种含氟 含有噻唑并吡唑衍生物，用于SAR分析。这一努力将得到计算支持。 化学.将选择两种最佳化合物作为mGlu 4的PET成像配体用于开发。在 目的3我们将使用mGlu 4敲除小鼠、大鼠和灵长类动物进行这些配体的体内表征 该模型的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。

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.