Saxitoxin-Antibody Conjugates as Tools for Na+ Ion Channel Study and Therapeutics

描述（由申请人提供）：阿片类镇痛药，如吗啡、氢吗啡酮和芬太尼，广泛用于急性、术后和慢性疼痛的治疗。尽管这种广泛的临床应用，一些副作用仍然存在，包括嗜睡，精神错乱，恶心，痛觉过敏和呼吸抑制。阿片类药物也很容易上瘾，被NIDA认为是滥用药物。我们希望开发新的药理学工具来探究疼痛感觉背后的特定生化机制，以揭示下一代疼痛治疗的长期目标。电压门控钠离子通道是负责细胞间电通信的完整膜蛋白。对10个哺乳动物基因进行了测序，编码10种不同的通道亚型（NaV1.1- 1.9和NaX），每种基因都具有独特的生物物理特征，以及细胞和组织分布模式。非特异性抑制nav的药物（如利多卡因）可作为短期局部麻醉剂使用，但不适合用于任何类型的全身或慢性使用。然而，一个令人信服的证据表明，对单一NaV亚型的特异性抑制可以减少疼痛敏感性，而不会伴随局部麻醉治疗的副作用（麻木、运动失调）（并且不会上瘾，如阿片类药物）。九种NaV亚型在大分子结构上的相似性阻碍了大多数开发仅针对单一通道亚型拮抗剂的药物的努力。我们的方法将利用单克隆抗体的高度特异性结合来靶向单个NaV亚型。我们设想利用针对NaV1.7的抗体，这是一种特别感兴趣的通道异构体，作为疼痛治疗的靶标。离子传导将被抑制共价连接到该抗体一个有效的，小分子通道拮抗剂。蛤蚌毒素是一种低分子量的天然产物，通过停留在通道孔的外口，对NaV1.1-1.4、1.6和1.7具有纳摩尔效力。将制定策略，将(+)-蛤蚌毒素的修饰形式偶联到抗体上，并测试这些药物作为NaV功能的同种异构体特异性阻滞剂的功效。该项目的成功将提供：1)可用于验证NaV1.7作为疼痛治疗靶点的工具；2)以抗体-小分子偶联物形式出现的新型治疗先导物；3)制备其他NaV亚型特异性抑制剂的蓝图。

DESCRIPTION (provided by applicant): Opioid analgesics, such as morphine, hydromorphone and fentanyl, are broadly prescribed for the management of acute, post-operative and chronic pain. Despite this widespread clinical use, a number of side effects persist including drowsiness, confusion, nausea, hyperalgesia and respiratory depression. Opioids are also highly addictive, and considered drugs of abuse by the NIDA. We wish to develop new pharmacological tools for interrogating specific biochemical mechanisms that underlie pain sensation with the longer-term goal of revealing next-generation therapeutics for pain treatment. Voltage-gated Na+ ion channels are integral membrane proteins responsible for electrical communication between cells. Ten mammalian genes have been sequenced that encode for ten different channel isoforms (NaV1.1- 1.9 and NaX), each having unique biophysical characteristics, and cellular and tissue distribution patterns. Drugs that inhibit NaVs non-specifically (e.g., lidocaine) find application as short-lasting, local anesthetics, but are less than desirable for any type of systemic or chronic use. A compelling body of evidence, however, suggests that specific inhibition of a single NaV isoform could reduce pain sensitivity without the accompanying side effects (numbness, ataxia) associated with local anesthetic treatments (and without chance of addiction, as noted with opioids). Similarities in the macromolecular structures of the nine NaV isoforms have thwarted most efforts to develop drugs that function as antagonist against only a single channel subtype. Our approach will capitalize on the highly specific binding of a monoclonal antibody engineered to target a single NaV isoform. We envision utilizing antibodies raised against NaV1.7, a channel isoform of particular interest as a target for pain treatment. Ion conduction will be inhibited by covalently linking to this antibody a potent, small molecule channel antagonist. Saxitoxin is a low molecular weight, naturally occurring product that acts with nanomolar potency on NaV1.1-1.4, 1.6, and 1.7 by lodging in the outer mouth of the channel pore. Strategies will be developed for conjugating modified forms of (+)-saxitoxin to the antibody and for testing the efficacy of these agents as isoform-specific blockers of NaV function. The success of this program will provide: 1) a tool that can be used to validate NaV1.7 as a target for pain treatment; 2) a novel therapeutic lead in the form of an antibody-small molecule conjugate; and 3) a blueprint for preparing specific inhibitors of other NaV isoforms. PUBLIC HEALTH RELEVANCE: Opioid analgesics, such as morphine, cause a range of side effects and are subject to abuse, yet remain the most frequently prescribed drugs for the treatment of pain. We wish to develop new pharmacological tools that act by intervening with specific pain-producing signals in order to gain a deeper understanding of the etiology of pain. Results from these studies could help guide the development of next-generation therapies for pain management.