Cyclic EphA4 peptide antagonists for neuroprotection in ALS

 描述（由申请人提供）：受体酪氨酸激酶EphA 4与几种神经退行性过程有关。引人注目的是，最近的一项研究表明，EphA 4低表达和功能丧失突变与肌萎缩侧索硬化症（ALS）的迟发性和延长生存期有关，ALS是一种毁灭性的神经退行性疾病，无法治愈，唯一FDA批准的治疗只能增加几个月的生存期。甚至部分EphA 4基因失活在ALS动物模型中也显示出有益的效果，使得抑制EphA 4功能成为对抗神经变性的有吸引力的策略。因此，我们之前发现的一种作为选择性EphA 4拮抗剂的肽在经典的大鼠SOD 1 G93 A ALS模型中表现出了希望，它显着抑制了ALS发病机制，证明了EphA 4拮抗剂的治疗潜力。尽管有这些令人兴奋的结果，但我们的第一代EphA 4拮抗剂在生物系统中缺乏所需的效力和稳定性，使其适合作为药物开发的先导。因此，在本申请中，我们提出开发和评估新的有效的EphA 4拮抗剂，其具有适合于使其成为未来治疗ALS的真正治疗先导的药理学性质。在我们的初步工作中，我们开发了一种环状十二肽的衍生物，其特异性抑制EphA 4-ephrin结合，IC 50值约为25 nM。该原型比任何先前已知的EphA 4拮抗剂强80倍，并且具有优化成为期望的治疗先导物的潜力。为了朝着这个目标开发相关的环状EphA 4拮抗剂，我们提出了一种高度集成的迭代策略，使用肽药物化学，结构生物学和我们在EphA 4神经生物学方面的长期专业知识。合理设计的新肽拮抗剂的活性将使用生物化学测定和神经元细胞培养模型进行评价。作为这些研究的补充，我们最有前途的新EphA 4拮抗剂将针对其在血浆和脑脊液中的特性及其穿过血脑屏障的倾向以及其在血液循环中的半躺进行分析。最后，与著名ALS专家Wim Robberecht博士合作的体内研究将描述在ALS小鼠模型中延迟疾病发作和促进存活的最佳拮抗剂。我们预计，所提出的研究将产生一种有效的EphA 4抑制剂，其药理学特征适合于作为单独或与其他治疗组合的治疗剂立即开发。它们还将提供对EphA 4抑制对神经变性的益处的潜在机制的有价值的见解。

 DESCRIPTION (provided by applicant): The receptor tyrosine kinase EphA4 has been implicated in several neurodegenerative processes. Strikingly, a recent study has shown that low EphA4 expression and loss-of-function mutations are linked to late onset and prolonged survival in amyotrophic lateral sclerosis (ALS), a devastating neurodegenerative illness for which there is no cure and the only FDA-approved therapy can increase survival by only several months. Even partial EphA4 gene inactivation has shown beneficial effects in animal models of ALS, making inhibition of EphA4 function an attractive strategy to counteract neurodegeneration. Accordingly, a peptide that we previously discovered as a selective EphA4 antagonist has shown promise in the classic rat SOD1 G93A ALS model, where it significantly dampened ALS pathogenesis demonstrating the therapeutic potential of EphA4 antagonistic agents. Despite these exciting results, our first generation EphA4 antagonists lack the required potency and stability in biological systems to make them suitable as leads for drug development. Thus, in this application we propose to develop and evaluate new potent EphA4 antagonists with pharmacological properties suitable to make them bona fide therapeutic leads for future treatment of ALS. In our preliminary work, we have developed a derivative of a cyclic dodecapeptide that specifically inhibits EphA4-ephrin binding with an IC50 value of ~25 nM. This prototype is a striking 80 fold more potent than any previously known EphA4 antagonist and has the potential for optimization to become a desired therapeutic lead. To develop related cyclic EphA4 antagonists towards this goal, we propose a highly integrated iterative strategy using peptide medicinal chemistry, structural biology and our long-standing expertise in EphA4 neurobiology. The activities of rationally designed new peptide antagonists will be evaluated using biochemical assays and neuronal cell culture models. Complementing these studies, our most promising new EphA4 antagonists will be profiled for their properties in plasma and cerebrospinal fluid and their propensity to cross the blood-brain barrier, as well as their half-lie in the blood circulation. Finally, in vivo studies in collaboration with renowned ALS expert Dr. Wim Robberecht will characterize the best antagonists in delaying disease onset and promoting survival in an ALS mouse model. We anticipate that the proposed studies will result in a potent EphA4 inhibitor with a pharmacologic profile suited for immediate development as a therapeutic agent alone or in combination with other treatments. They will also provide valuable insight into the mechanism underlying the benefits of EphA4 inhibition against neurodegeneration.