Design, Synthesis and Evaluation of Novel Isoform-Selective Sodium Channel Inhibi

描述（由申请人提供）：与阿片类镇痛药相关的副作用，如恶心、嗜睡、呼吸抑制和潜在的成瘾性，正在推动急性、亚急性和慢性疼痛新疗法的设计和开发。电压门控钠离子通道是负责沿导电细胞传递信号的完整膜蛋白。对10个哺乳动物基因进行了测序，它们编码10种不同的通道异构体（NaV1.1-1.9和NaX），每种通道异构体都具有独特的门控特性和细胞和组织分布模式。最近的研究将一种人类Na+通道亚型NaV1.7的遗传功能缺失突变与一种罕见的遗传性疾病先天性疼痛不敏感（CIP）联系起来。CIP患者对正常疼痛刺激的敏感性降低，但感觉或认知功能没有明显缺陷。大量令人信服的证据表明，在正常人群中选择性抑制NaV1.7可以重现CIP的表型。人类NaV蛋白的高度同源性，加上对多个离子通道靶点进行高通量筛选的挑战，阻碍了针对单个NaV亚型开发选择性拮抗剂的大多数努力。最近的研究结果表明，hNaV1.7孔区两个氨基酸的变化是导致天然钠通道拮抗剂家族胍毒素（GTxs）对该亚型的效力降低的原因。这种变异存在于所有已知的hNaV1.7剪接变体中，但未在任何其他人类NaV异构体中发现。计算模型研究和蛋白质诱变实验表明，通过明智的合成修饰，有可能恢复GTx对hNaV1.7的效力，同时破坏GTx与其他8种hNaV亚型的结合。一个计划是准备GTxs的类似物，设计成与hNaV1.7高亲和力结合，并通过全细胞电生理学测试这些化合物，以测量效力和同型选择性。该项目的成功将提供1)对NaV孔结构和GTx结合姿态的更好理解，2)验证NaV1.7作为疼痛治疗靶点的新工具，以及3)高亲和力，异构体选择性钠通道拮抗剂作为优化下一代疼痛治疗的先导化合物。

DESCRIPTION (provided by applicant): Side effects associated with opioid analgesics, such as nausea, drowsiness, respiratory depression, and potential for addiction, are motivating the design and development of new therapies for acute, subacute and chronic pain. Voltage-gated Na+ ion channels are integral membrane proteins responsible for the transmission of signals along electrically conducting cells. Ten mammalian genes have been sequenced, which encode ten distinct channel isoforms (NaV1.1-1.9 and NaX), each having unique gating properties, and cellular and tissue distribution patterns. Recent studies have correlated a hereditary loss-of-function mutation in one human Na+ channel isoform - NaV1.7 - with a rare genetic disorder known as Congenital Insensitivity to Pain (CIP). Individuals with CIP have reduced sensitivity to normally painful stimuli without significant deficits to sensory or cognitive function. A compellin body of evidence indicates that selective inhibition of NaV1.7 in normal humans could recapitulate the phenotype of CIP. The high homology of human NaV proteins, coupled with challenges associated with high-throughput screening against multiple ion channel targets, have thwarted most efforts to develop selective antagonists for individual NaV subtypes. Recent findings indicate that a two amino acid variation in the pore region of hNaV1.7 is responsible for reduced potency of a family of naturally-occurring sodium channel antagonists, the guanidinium toxins (GTxs), against this isoform. This variation is present in all known hNaV1.7 splice variants, but is not found in any other human NaV isoform. Computational modeling studies and protein mutagenesis experiments indicate that it may be possible to restore potency of the GTxs against hNaV1.7 while destabilizing GTx binding to the other eight hNaV isoforms by judicious synthetic modifications. A plan is in place to prepare analogues of the GTxs designed to bind with high affinity to hNaV1.7, and to test these compounds by whole-cell electrophysiology to measure potency and isoform-selectivity. Success of this program will provide 1) an improved understanding of the NaV pore structure and GTx binding pose, 2) a novel tool to validate NaV1.7 as a target for pain treatment, and 3) a high-affinity, isoform-selective sodium channel antagonist as a lead compound for optimization toward a next-generation pain therapeutic.