Development of mGlu7 receptor allosteric modulators for neurological and psychiatric disorders

项目总结 代谢型谷氨酸受体7(MGlu7)广泛调节突触前神经递质的释放 中枢神经系统是在海马体和杏仁体中诱导长时程增强(LTP)所必需的， 这表明它在突触可塑性中起着中心作用。最近，GRM7基因的主要突变被认为与 到智力残疾、刻板印象和癫痫，这些症状在神经发育障碍中很常见。 此外，我们还发现，临床上患者大脑中mGlu7蛋白水平显著降低。 被诊断为神经发育障碍，雷特综合征(RTT)。甲基功能缺失突变 CPG结合蛋白2(MECP2)是一种表观遗传的转录调节蛋白，是RTT的主要原因，RTT是一种 导致刻板印象行为发展的疾病、运动迟缓、焦虑、认知障碍、自闭症 特征、癫痫发作和呼吸暂停。与RTT患者和模型小鼠mGlu7的减少一致，增强了 MGlu7与小分子正变构调节剂(PAM)结合可纠正多突触的可塑性， 带有MeCP2基因敲除(KO)等位基因的小鼠的认知、社交和呼吸表型。这些早期研究 使用了一种化合物，与其他几种代谢性谷氨酸受体相比，对mGlu7没有选择性。 我们最近对VU6027459进行了优化，这是一种高度选择性的mGlu7工具，具有合适的药代动力学 啮齿动物体内使用的参数。使用VU6027459，我们进一步验证了mGlu7增强在 逆转异常的RTT表型。我们建议将RTT的单基因紊乱与一种 药物开发运动，作为开发mGlu7 PAM的临床进入途径；预计 未来的研究可能会扩展到替代适应症，如原发性癫痫或精神分裂症。 我们之前的RTT研究主要集中在MECP2/MeCP2等位基因具有功能性的患者和小鼠身上 空。然而，很大一部分RTT患者的MECP2基因存在单点突变，而我们的 初步数据表明，人类RTT组织中mGlu7的表达水平存在差异，这与 有特定的突变。这表明，对这种疾病进行疗效测试的疗法需要临床前研究。 在反映这种临床异质性的各种小鼠模型中进行验证。使用扩展的临床样本集 和建模不同突变的小鼠，我们将检验mGlu7水平可能存在差异的假设 在不同的MECP2突变的背景下受到影响，并确定特定的突变是否是疾病状态的基础 最有可能对mGlu7 PAM表现出有效和安全的响应，或者如果mGlu7 PAM将在 整个突变谱。最后，我们将进行生物标记物研究，以我们的发现为基础，MeCP2- 缺陷小鼠在整个病程中表现出脑电频谱的变化和REM睡眠的减少。这些 研究结果反映了RTT患者的睡眠异常，表明EEG代表了临床上可翻译的 以及该项目的非侵入性生物标志物。

PROJECT SUMMARY Metabotropic glutamate receptor 7 (mGlu7) regulates presynaptic neurotransmitter release widely throughout the CNS and is required for the induction of long-term potentiation (LTP) in the hippocampus and amygdala, suggesting a central role in synaptic plasticity. Recently, primary mutations in the GRM7 gene have been linked to intellectual disability, stereotypies, and seizures, symptoms common in neurodevelopmental disorders. Additionally, we have found that mGlu7 protein levels are significantly reduced in the brains of patients clinically diagnosed with the neurodevelopmental disorder, Rett syndrome (RTT). Loss-of-function mutations in Methyl CpG Binding Protein 2 (MECP2), an epigenetic regulation of transcription, are the major cause of RTT, which is a disease resulting in the development of stereotyped behaviors, motor delays, anxiety, cognitive deficits, autistic features, seizures, and apneas. Consistent with reductions in mGlu7 in RTT patients and model mice, potentiating mGlu7 activity with small molecule positive allosteric modulators (PAMs) corrects multiple synaptic plasticity, cognitive, social, and respiratory phenotypes in mice with an Mecp2 knockout (KO) allele. These early studies employed a compound that was not selective for mGlu7 versus several other metabotropic glutamate receptors. We have recently optimized VU6027459, a highly selectivity mGlu7 tool that exhibits suitable pharmacokinetic parameters for in vivo rodent use. Using VU6027459, we have further validated a role for mGlu7 potentiation in reversing abnormal RTT phenotypes. We propose to use the monogenetic disorder of RTT, in tandem with a drug development campaign, as a clinical entry path for the development of mGlu7 PAMs; it is anticipated that future studies could then expand into alternate indications, such as primary epilepsies or schizophrenia. Our previous RTT studies have focused on patients and mice with an MECP2/Mecp2 allele that is a functional null. A large proportion of RTT patients, however, have single point mutations in the MECP2 gene, and our preliminary data suggest that there are differences in mGlu7 expression levels in human RTT tissue that correlate with specific mutations. This indicates that therapeutics for efficacy testing in this disease require preclinical validation in various mouse models that reflect this clinical heterogeneity. Using an expanded clinical sample set and mice modeling different mutations, we will test the hypothesis that mGlu7 levels may be differentially impacted in the context of distinct MECP2 mutations and determine if specific mutations underlie disease states most likely to exhibit efficacious and safe responses to mGlu7 PAMs or if mGlu7 PAMs will have utility across the entire mutation spectrum. Finally, we will perform biomarker studies that build upon our findings that Mecp2- deficient mice exhibit EEG spectral changes and reductions in REM sleep across the disease course. These findings mirror sleep abnormalities seen in RTT patients, suggesting that EEG represents a clinically translatable and noninvasive biomarker for the program.