Therapeutic Na+ channel blockers: Receptor & Drug Design

描述（由申请人提供）：该项目的长期目标是开发与疼痛管理相关的长效钠离子通道阻滞剂，并更好地了解这些阻滞剂的工作机制。传统的局麻药（LAs）往往不适合慢性或顽固性癌症疼痛，因为它们的神经阻滞时间不足。我们的具体目标是(1)鉴定和合成有效阻断开放和/或失活的Na+通道的化合物，(2)评估有效的Na+通道阻滞剂的使用和状态依赖性阻断，(3)测试它们作为长效LAs的体内效力，以及(4)在Na+通道α亚基内绘制它们的受体位点。最近的筛选已经确定了几种新的铅结构，它们可以阻断具有高亲和力的开放Na+通道。早期的筛选表明，口服治疗神经性疼痛的药物，如阿米替林、氟卡奈和美西汀，在其治疗血浆浓度下也能有效阻断开放的Na+通道。我们假设这些药物缓解损伤神经中发现的异位高频放电是由于它们对开放Na+通道的高亲和力阻断。阿米替林，它太有效地阻断失活的Na+通道，确实作为一个长效的LA。我们计划在这些导联结构的基础上鉴定和合成新的开放和/或失活通道阻滞剂。在野生型和/或人类HEK293细胞中表达的Na+通道失活缺陷突变体中，将确定它们在重复脉冲期间使用依赖的Na+电流阻断以及静息、开放和失活通道阻断的50%抑制浓度（IC50）。通过不同途径注射强效钠离子通道阻滞剂前后，对大鼠或羊的神经阻滞感觉和运动功能进行评价。最后，我们计划通过位点定向诱变和配体-受体复合物的计算机模拟来划定Na+通道α -亚基内选定阻滞剂的受体。这些信息将反过来促进基于受体的药物设计。总之，这些研究应该为我们开发选择性靶向开放和/或失活Na+通道的长效la提供新的先导结构。这些药物，无论是口服还是局部注射，都可能对慢性和难治性癌症疼痛患者有益。

DESCRIPTION (provided by applicant): The long-term objectives of this project are to develop long-acting Na+ channel blockers pertinent for pain management and to gain a better understanding of how these blockers work mechanistically. Traditional local anesthetics (LAs) are often inept for chronic or intractable cancer pain due to their insufficient duration of nerve block. Our specific aims are (1) to identify and synthesize compounds that potently block the open and/or inactivated Na+ channels, (2) to assess the use- and state-dependent block of potent Na+ channel blockers, (3) to test their in vivo potency as long-acting LAs, and (4) to map their receptor site within the Na+ channel alpha-subunit. Recent screening has identified several new lead structures that block open Na+ channels with high affinities. Earlier screening demonstrated that drugs taken orally for neuropathic pain, such as amitriptyline, flecainide, and mexiletine, also block open Na+ channels effectively at their therapeutic plasma concentrations. We hypothesize that these drugs alleviate ectopic high-frequency discharges found in injured nerves due to their high-affinity block of open Na+ channels. Amitriptyline, which too potently blocks the inactivated Na+ channels, indeed acts as a long-acting LA. We plan to identify and synthesize novel open and/or inactivated-channel blockers based on these lead structures. Their use-dependent block of Na+ currents during repetitive pulses and the 50% inhibitory concentration (IC50) of resting-, open-, and inactivated-channel block will be determined in wild-type and/or in inactivation-deficient mutant Na+ channels expressed in human HEK293 cells. Sensory and motor functions of nerve block will be evaluated in rats or sheep before and after injection of potent Na + channel blockers via various routes. Finally, we plan to delimit the receptor for selected blockers within the Na+ channel alpha-subunit by site-directed mutagenesis and by computer simulation of the ligand-receptor complex. This information will in turn facilitate receptor-based drug design. Together, these studies should provide us new lead structures for the development of long-acting LAs that selectively target open and/or inactivated Na+ channels. Such drugs, either taken orally or injected locally, may be beneficial for patients with chronic and intractable cancer pain.