Discovery and development of novel glycine transporter-2 inhibitors for the treatment of neuropathic pain

据估计，7-10%的一般人群患有慢性神经性疼痛和相关的神经性疼痛。 美国每年的经济损失超过1600亿美元。目前用于治疗慢性神经病变的镇痛药 疼痛缺乏疗效、引起剂量限制性副作用或存在耐受和滥用的显著风险。因此，在本发明中， 新的镇痛药的发现，提供有意义的疼痛缓解，提高了安全性，耐受性和 减少滥用可能性仍然是一个未满足的医疗需求。在涉及的各种机制中， 在病理性疼痛中，从脊髓到高级CNS的伤害性信号传导的去抑制起着关键的作用。 作用事实上，我们和其他人已经表明，抑制甘氨酸能神经传递的背角是 病理性疼痛状态受损。因此，已经提出，增强脊髓甘氨酸能神经递质的表达是可能的。 神经传递可以减少伤害感受器信号传导并提供镇痛。甘氨酸转运蛋白-2（GlyT-2） 调节CNS中的细胞外甘氨酸浓度，并提供了一个高度有吸引力的靶点， 受损的脊髓抑制信号传导。事实上，GlyT-2抑制剂已经在几种啮齿类动物中证明了功效。 急性和慢性疼痛的模型。最近的研究表明，部分或可逆的GlyT-2抑制 可以潜在地规避基于机制的潜在副作用， 有效性和耐受性的平衡。我们合成了60种生物活性脂质变构部分抑制剂， 不同程度的效力和%最大抑制，我们这类最有效的化合物增强了 大鼠脊髓切片中的离体紧张性甘氨酸能电流，而不消耗突触前甘氨酸再加载， 在PNL大鼠中产生体内剂量依赖性功效而无副作用。另外，我们合成了 18种新的GlyT-2抑制剂击中了来自ORG-25543的化合物，这些化合物在以下方面表现出可重现的变化： 可逆性和转运回收率。从这两个库中，我们建议 进行双管齐下的药物化学活动，以确定具有 适用于测量脊髓中作用的良好效价、结合特征和ADME特征 切片和体内PK。将在大鼠PNL模型中筛选选定的化合物以评估镇痛功效 以及行为模型中的剂量限制效应和TI。我们的建议寻求支持，以优化我们的打击 化合物，以提供选择性和口服生物可利用的GlyT-2抑制剂，用于进一步开发和最终应用。 神经性疼痛的人体临床试验本提案中概述的研究旨在进行药物治疗， 使用一组主要、次要、计数筛选和ADMET测定进行化学优化，以评估 效价、结合特征（%最大抑制、可逆性和结合机制）、选择性和药物- 类似性质（具体目标1），并评估晚期镇痛药的PK、临床前镇痛疗效和耐受性。 化合物在神经病理性疼痛动物模型和运动行为不同阶段的化合物 优化（具体目标2）。

It is estimated that 7–10% of the general population suffers from chronic neuropathic pain and associated annual economic costs exceed $160 billion in the US. Current analgesics used to treat chronic neuropathic pain lack efficacy, induce dose-limiting side effects or present a significant risk of tolerance and abuse. Thus, the discovery of novel analgesics that provide meaningful pain relief with improved safety, tolerability and reduced abuse potential remains an unmet medical need. Among the various mechanisms involved in pathological pain, disinhibition of nociceptive signaling from the spinal cord to the higher CNS plays a critical role. Indeed, we and others have shown that inhibitory glycinergic neurotransmission in the dorsal horn is impaired in pathological pain states. Thus, it has been proposed that enhancing spinal glycinergic neurotransmission could reduce nociceptor signaling and provide analgesia. Glycine transporter-2 (GlyT-2) regulates extracellular glycine concentrations in the CNS and presents a highly attractive target to augment impaired spinal inhibitory signaling. Indeed, GlyT-2 inhibitors have demonstrated efficacy in several rodent models of acute and chronic pain. Recent studies suggest that either partial or reversible GlyT-2 inhibition can potentially circumvent potential mechanism-based adverse effects and provide analgesics with a suitable balance of efficacy and tolerability. We synthesized 60 bioactive lipid allosteric partial inhibitors exhibiting varying degrees of potency and %maximal inhibition and our most potent compound of this class enhances tonic glycinergic currents ex vivo in rat spinal cord slices without depleting presynaptic glycine reloading and produces in vivo dose-dependent efficacy in PNL rats without adverse effects. Separately, we synthesized 18 novel GlyT-2 inhibitor hit compounds derived from ORG-25543 that exhibit reproducible variations in reversibility and transport recovery using a washout assay protocol. From these two libraries, we propose conducting a dual-pronged medicinal chemistry campaign to identify optimized compounds possessing favorable potency, binding profiles and ADME characteristics suitable for measuring effects in spinal cord slices and in vivo PK. Selected compounds will be screened in the rat PNL model to assess analgesic efficacy and in behavioral models for dose-limiting effects and TI. Our proposal seeks support to optimize our hit compounds to provide selective and orally bioavailable GlyT-2 inhibitors for further development and eventual human clinical trials in neuropathic pain. The studies outlined in this proposal seek to conduct medicinal chemistry optimization using a battery of primary, secondary, counter-screen, and ADMET assays to assess potency, binding profile (%maximal inhibition, reversibility and mechanism of binding), selectivity and drug- like properties (Specific Aim 1), and assess PK, preclinical analgesic efficacy and tolerability of advanced compounds in animal models of neuropathic pain and motor behavior at different stages of compound optimization (Specific Aim 2).