Treat Neuropathic Pain with Dissolvable Microneedles Containing Anti-CGRP Peptide

描述(申请人提供)：神经性疼痛是一种复杂的慢性疼痛状态，通常由组织损伤引起，部分原因是受损的周围神经纤维或支配受损组织的纤维随后功能障碍。神经纤维损伤的影响包括损伤部位和损伤周围区域神经功能的改变。某些类型的周围神经损伤会导致神经瘤的发展，并伴随着相关的局部慢性疼痛，表现为痛觉异常和痛觉过敏。大约30%的这些神经瘤变得足够疼痛，以至于受影响的手指、手或四肢被排除在日常生活活动之外，患者无法完成常规任务。神经瘤疼痛特别难治疗，而且通常对目前的神经病理性疼痛治疗反应较差。这种神经瘤疼痛的确切病理生理学机制尚不清楚，尽管已经推测了外周和中枢敏化作用。降钙素基因相关肽(CGRP)似乎在这一过程中起着关键作用。CGRP由背根神经节(DRG)的伤害性感觉神经元合成，在致敏次级神经元的脊髓和周围神经末梢释放。降钙素基因相关肽在外周的释放是多方面的，包括诱导血管扩张和巨噬细胞募集。周围神经损伤后大鼠背根神经节神经元中CGRP的表达增加，CGRP在实验诱导的大鼠神经瘤和人类神经瘤中均有积聚。此外，在实验诱导的糖尿病神经病变中，大鼠皮肤中过度释放降钙素基因相关肽。这些结果表明，CGRP合成和释放的增加在至少某些类型的神经病理性疼痛中是重要的，并可能特定地参与神经瘤疼痛。最有效和最有选择性的CGRP受体拮抗剂CGRP8-37是一种大分子多肽，不容易通过普通途径输送到神经源性炎症部位。为了克服这一问题，我们开发和使用了创新的可溶CGRP8-37微针技术，并完成了其在SBIR I期支持下的止痛潜力的可行性研究(R43 DA026363)。在这项研究中，我们证明了微针注射CGRP8-37或CGRP8-37与Na+通道阻滞剂的组合能成功地阻断大鼠皮肤中波紫外线照射(UVB)后的神经源性炎性疼痛。在这里建议的SBIR第二期研究中，我们 将重点评估微针在两种临床适用的神经病理性疼痛动物模型-备用神经损伤模型和胫骨神经瘤移位模型中的疗效。为了开发IND应用，我们还将研究微针在兔身上的安全性，因为兔的皮肤敏感度比大鼠高。1.应用CGRP8-37微针贴片制作大鼠神经病理性疼痛模型，观察CGRP8-37微针贴片在两种神经病理性疼痛模型中的应用效果。2.观察微针透皮给药对大鼠和兔的局部皮肤毒性，并对大鼠全身应用CGRP8-37进行毒性评价。3.研究优化微针贴片制造工艺的方法，为今后的IND研究做准备。这一第二阶段项目如果成功，将为IND支持研究提供一个基于证据的通过/不通过的决定，这将导致在这一第二阶段SBIR项目的竞争性更新的支持下，对CGRP8-37微针在志愿者和患者中进行首次人体测试。

DESCRIPTION (provided by applicant): Neuropathic pain is a complex, chronic pain state that is usually initiated by tissue injury and maintained, in part, by subsequent dysfunction of damaged peripheral nerve fibers or fibers that innervate that injured tissue. The impact of nerve fiber damage includes a change in nerve function both at the site of injury and areas around the injury. Certain types of peripheral nerve damage cause the development of neuromas with associated localized chronic pain manifested as allodynia and hyperalgesia. Approximately 30% of these neuromas become sufficiently painful that the affected digit, hand or limb becomes excluded from activities of daily living and the patient is unable to complete routine tasks. Neuroma pain is particularly difficult to treat, and generally responds poorly to current neuropathic pain treatments. The exact pathophysiology of this neuroma pain is poorly understood, though peripheral and central sensitization has been speculated. Calcitonin Gene-Related Peptide (CGRP) appears to be critical in this process. CGRP is synthesized by nociceptive sensory neurons of dorsal root ganglia (DRG) and released both in the spinal cord where the peptide sensitizes secondary neurons, and from peripheral nerve endings. The effects of CGRP release in the periphery are multifaceted, including induction of vasodilation and macrophage recruitment. Expression of CGRP increases in the DRG neurons of rats after peripheral nerve injury and CGRP accumulates in experimentally-induced neuromas in rats as well as in human neuromas. Furthermore, excessive release of CGRP into the skin of rats was demonstrated in experimentally-induced diabetic neuropathy. These results suggest that increases in CGRP synthesis and release are important in at least some types of neuropathic pain and may specifically be involved in neuroma pain. The most potent and selective CGRP receptor antagonist, CGRP8-37, is a large peptide and cannot be easily delivered to neurogenic inflammatory sites by common routes. To overcome this problem, we have developed and utilized innovative dissolvable CGRP8-37 microneedle technology and completed a feasibility study of their analgesic potential with SBIR Phase I support (R43 DA026363). In this study, we demonstrated that microneedle delivery of CGRP8-37 or a combination of CGRP8-37 and a Na+ channel blocker to the skin, successfully blocked neurogenic inflammatory pain after ultraviolet B irradiation (UVB) of the skin of rats. In the SBIR Phase II studies proposed here, we will focus on evaluation of microneedle efficacy in two clinically applicable animal models of neuropathic pain - the spared nerve injury model and the tibial neuroma transposition model. Toward the development of an IND application, we will also investigate the microneedle safety in rabbits which have higher skin sensitivity than rats. The Specific Aims are as follows: 1. Test the efficacy of CGRP8-37 microneedle patches in two rat neuropathic pain models: the Spared Nerve Injury model of regional pain and a more localized neuropathic model, the Tibial Neuroma Transposition model. 2. Investigate local dermal toxicity following the transdermal application of microneedles in rats and rabbits, and evaluate toxicity following systemic administration of CGRP8-37 in rats. 3. Examine means of optimizing manufacturing processes of microneedle patches in order to prepare for future IND studies. This Phase II project, if successful, will provide an evidence-based go/no go decision toward IND enabling studies that can lead to first-in-human testing of CGRP8-37 microneedles in volunteers and patients supported by competitive renewal of this Phase II SBIR project.