Optimization of Betulinic Acid analogs for T-type calcium channel inhibition for non-addictive relief of chronic pain

摘要 化疗引起的周围神经病变（CIPN）是一种常见的（患病率30-70%）和潜在的剂量- 限制了许多癌症化疗药物治疗方案的副作用。临床上，CIPN表现为疼痛 燃烧、射击或类似电击。癌症发病率的增加， 由于化疗方案的癌症存活率正在将癌症疼痛转化为一个巨大的，未满足的医疗需求， 问题.神经毒性化疗剂（例如，抗微管剂，如紫杉醇）可能导致结构性 外周神经损伤，导致外周和/或中枢躯体感觉处理异常 神经系统背根神经节（DRG）感觉神经元以及脊髓中的神经元细胞是脊髓的神经元。 化疗诱导的神经毒性发生的优先部位。发病机制复杂，但包括 离子通道的改变。紫杉醇（Taxol®）增加大鼠T型（Cav3.2）电压门控性Ca 2+电流 背根神经节（DRG）神经元;这些神经元负责传递有害的感觉刺激， 提示这些通道是与CIPN相关的特异性感觉异常的重要介质。 鉴于这些通道在调节脊髓背角传入纤维兴奋性和突触功能中的作用， 角和它们在疼痛状态期间的动态调节，阻断或耗尽这些组织中的Cav3.2通道 应介导镇痛作用。在过去的五年里，已经做出了相当大的努力， 新型T型钙通道阻滞剂。该提案旨在开发有效的，口服的， 选择性Cav3.2通道拮抗剂，基于天然产物桦木酸（BA）的结构， 由Leslie Gunatilaka博士（亚利桑那大学天然产品中心主任）的实验室鉴定 (UA))PI Rajesh卡纳博士（UA）将其表征为CIPN中的Cav3.2选择性和抗伤害感受性。 在这项工作中，我们与Regulonix，LLC合作，对选择的Cav3.2靶向化合物进行表征。 及其类似物在体外和体内功效测定以及早期ADME和PK优化中的应用。工作 这里提出的是为CIPN开发非阿片类药物疼痛治疗的第一步，也可以抑制阿片类药物的滥用 和上瘾。我们预计成功对抗紫杉醇引起的慢性疼痛会转化为其他慢性疼痛 类型，但CIPN为早期阶段的概念验证提供了重点。Regulonix的具体目标是：（1） 设计与合成（Dr. L. Gunatilaka）和Cav3.2特异性和生物物理学的阐明 选择BA类似物的性质，以获得机制和安全性信息，并记录独特的途径 （2）分析BA类似物的体外细胞毒性、早期ADME和 药代动力学特性，并筛选对GPCR、离子通道和已知替代药物的脱靶效应 疼痛靶点，包括阿片受体;和（3）表征来自目标2的最佳两种BA类似物，用于临床前 使用神经性疼痛模型（紫杉醇）进行研究，以提供关于口服有效性、安全性和阿片类药物的信息， 节省。完成后，我们希望有一个验证的BA类似物和几个有价值的备份化合物。

ABSTRACT Chemotherapy-induced peripheral neuropathy (CIPN) is a common (prevalence 30–70%) and potentially dose- limiting side effect of many cancer chemotherapy drug treatment regimens. Clinically, CIPN presents with pain that is burning, shooting or electric-shock-like. The increase in prevalence of cancer coupled with an increase in the cancer survival rates due to chemotherapy regimens is transforming cancer pain into a large, unmet medical problem. Neurotoxic chemotherapeutic agents (e.g., antimicrotubule agents like paclitaxel) may cause structural damage to peripheral nerves, resulting in aberrant somatosensory processing in the peripheral and/or central nervous system. Dorsal root ganglia (DRG) sensory neurons as well as neuronal cells in the spinal cord are the preferential sites in which chemotherapy induced neurotoxicity occurs. Pathogenesis is complex but includes alterations in ion channels. Paclitaxel (Taxol®) increases T-type (Cav3.2) voltage-gated Ca2+ currents in rat dorsal root ganglion (DRG) neurons; these neurons are responsible for conveying noxious sensory stimuli, suggesting these channels are important mediators of specific sensory abnormalities associated with CIPN. Given the roles of these channels in regulating afferent fiber excitability and synaptic function in the spinal dorsal horn and their dynamic regulation during pain states, blocking or depleting Cav3.2 channels in these tissues should mediate analgesic effects. In the past 5 years, considerable effort has been applied towards identifying novel classes of T-type calcium channel blockers. This proposal aims to develop potent, orally available, and selective Cav3.2 channel antagonists, building on the structure of a natural product – betulinic acid (BA) – identified by the laboratory of Dr. Leslie Gunatilaka (Director, Natural Products Center, University of Arizona (UA)) and characterized by the PI Dr. Rajesh Khanna (UA) to be Cav3.2-selective and antinociceptive in CIPN. For this work, we have partnered with Regulonix, LLC for characterizing select Cav3.2-targeted compounds and their analogs in in vitro and in vivo efficacy assays as well as early ADME and PK optimization. The work proposed here is the first step in developing non-opioid pain treatments for CIPN that also curb opioid misuse and addiction. We anticipate success against paclitaxel-induced chronic pain to translate into other chronic pain types as well, but CIPN provides focus for early stage proof-of-concept. Regulonix’s specific aims are: (1) Design and synthesis (Dr. L. Gunatilaka) of BA analogues and elucidation of Cav3.2 specificity and biophysical properties of select BA analogs to gain mechanistic and safety information and to document the unique pathway for function in neurons; (2) Profile BA analogues for their in vitro cellular cytotoxicity, early ADME and pharmacokinetic properties, and screening for off-target effects on GPCRs, ion channels and alternative known pain targets, including opioid receptors; and (3) Characterize the best two BA analogs, from Aim 2, for preclinical studies using a neuropathic pain model (paclitaxel) to provide information about oral efficacy, safety, and opioid- sparing. Upon completion, we expect to have a validated BA analog and several worthy backup compounds.