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

描述(申请人提供)：阿片类镇痛剂，如吗啡、氢化吗啡和芬太尼，广泛用于治疗急性、手术后和慢性疼痛。尽管这种临床应用广泛，但一些副作用仍然存在，包括嗜睡、神志不清、恶心、痛觉过敏和呼吸抑制。阿片类药物也非常容易上瘾，被NIDA视为滥用药物。我们希望开发新的药理学工具来询问作为疼痛感觉基础的特定生化机制，并以揭示下一代疼痛治疗的长期目标为目标。电压门控钠离子通道是负责细胞间电通讯的完整膜蛋白。已经对10个哺乳动物基因进行了测序，这些基因编码10种不同的通道亚型(Nav1.1-1.9和NAx)，每种亚型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药使用，但不适用于任何类型的全身或慢性使用。然而，大量令人信服的证据表明，特定抑制单一NAV亚型可以降低疼痛敏感性，而不会伴随局部麻醉治疗的副作用(麻木、共济失调)(也没有阿片类药物所指出的上瘾机会)。九种NAV亚型的大分子结构相似，阻碍了开发仅对单一通道亚型起拮抗剂作用的药物的大部分努力。我们的方法将利用针对单一NAV亚型的单抗的高度特异性结合。我们设想利用针对Nav1.7的抗体，Nav1.7是一种特别感兴趣的通道亚型，作为疼痛治疗的靶点。离子传导将通过共价连接到这种有效的小分子通道拮抗剂抗体上而被抑制。岩藻毒素是一种低分子的天然产物，通过倒伏在通道孔的外口而对Nav1.1-1.4、1.6和1.7具有纳摩尔效力。将开发将修饰形式的()-岩藻毒素与抗体结合的策略，并测试这些药物作为NAV功能的异构体特异性阻滞剂的有效性。这一计划的成功将提供：1)可用于验证Nav1.7作为疼痛治疗靶标的工具；2)抗体-小分子结合物形式的新型治疗先导；以及3)制备其他NAV亚型的特定抑制剂的蓝图。 公共卫生相关性：阿片类镇痛剂，如吗啡，会引起一系列副作用，并容易被滥用，但仍是治疗疼痛最常用的处方药物。我们希望开发新的药理学工具，通过干预特定的产生疼痛的信号来发挥作用，以便更深入地了解疼痛的病因。这些研究的结果可能有助于指导下一代疼痛管理疗法的开发。

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.