Developing Ca2+/CaM Kinase II Inhibitors to Treat Arrhythmias in Heart Failure

描述(申请人提供)：室性心律失常具有多样和复杂的病因，包括对多种神经体液病理通路的过度刺激，这表明没有单一的上游阻滞剂会足够有效。Ca[2+]/钙调蛋白依赖性蛋白激酶II(CaMKII)是这些神经体液通路的常见下游介质，其过度活跃参与了室性心律失常的发生机制。我们认为，该激酶是一种新的治疗靶点，这一想法得到了以下证明的支持：在动物模型中，药物和遗传上降低CaMKII活性可以减少心律失常和CaMKII升高的患者的心肌细胞中的心律失常。我们已经开发了CaMKII的小分子抑制剂，并建议提高先导化合物的效力和选择性，然后在健壮的小鼠模型中测试抑制心律失常的最佳化合物。根据我们在新晶体结构中从对接抑制剂发展到其活性部位的见解，我们提出了一系列为铅优化设计的化合物。我们的目标是将效力提高10倍，并在15海里以下达到IC50。这项临床前概念验证研究将使用钙调神经磷酸酶过表达的小鼠模型来测试顶级抑制剂的体内疗效，该模型与较大的动物模型相关，也可能与人类心肌病变有关。由于CaMKII表达增加，小鼠有严重的心力衰竭和高水平的环境心律失常，我们的里程碑是显示至少一种CaMKII抑制剂的疗效。如果成功，我们将通过优化ADME/Tox和其他类药物特性的抑制剂来延长临床前开发，测试它们在 其他动物模型，并为IND应用程序执行IND使能研究，目的是治疗心力衰竭的心律失常。 公共卫生相关性：心脏性猝死是一个主要的公共卫生问题，据估计，每年有50万美国人死于猝死。大多数心源性猝死是由快速的室性心律失常引起的，心力衰竭患者风险最高。目前有证据表明，针对细胞内信号的药物靶向，特别是钙/钙调素依赖的蛋白激酶II，作为钙稳态失调的感受器，可以抑制心力衰竭时的心律失常，因此它是治疗心律失常的新靶点。我们建议修改我们为这种蛋白激酶开发的小分子抑制剂，以提高其效力，对新的抑制剂进行生化分析，以确保它们具有所需的特性，然后在小鼠模型中测试对心律失常的抑制作为概念验证。

DESCRIPTION (provided by applicant): Ventricular arrhythmias have diverse and complex etiologies that include excessive stimulation of multiple neurohumoral pathological pathways, suggesting that no single upstream blocker will be sufficiently efficacious. Ca[2+]/calmodulin-dependent protein kinase II (CaMKII) is a common downstream mediator of these neurohumoral pathways and its hyperactivity contributes to the mechanisms of ventricular arrhythmia. We propose that the kinase is a novel therapeutic target, an idea supported by the demonstration that pharmacological and genetic reduction of CaMKII activity decreases arrhythmia in animal models and in human cardiomyocytes from patients with arrhythmia and elevated CaMKII. We have developed small molecule inhibitors of CaMKII and propose to increase potency and selectivity of the lead compound then test the best compounds for inhibition of arrhythmia in a robust mouse model. Guided by insights we developed from docking inhibitors to its active site in our new crystal structures we propose a set of compounds designed for lead optimization. Our goal is to improve potency 10-fold and reach IC50s below 15 nM. The preclinical proof-of concept study will test the in vivo efficacy of the top inhibitors using a calcineurin over expressing mouse model that is relevant to larger animal models, and likely to diseased human myocardium as well. The mice have severe heart failure and high levels of ambient arrhythmias resulting from increased CaMKII expression and our milestone is to show efficacy with at least one CaMKII inhibitor. If successful we will be positioned to extend the preclinical development by optimizing the inhibitors for ADME/Tox and other drug-like properties, testing their efficacy in other animal models, and perform IND enabling studies for an IND application aimed at arrhythmia in heart failure. PUBLIC HEALTH RELEVANCE: Sudden cardiac death is a major public health problem, which is estimated to kill 500,000 Americans each year. Most sudden cardiac death is due to rapid ventricular arrhythmias and patients with heart failure are at highest risk. Evidence now supports that pharmacological targeting of intracellular signaling, in particular of Ca2+/calmodulin-dependent protein kinase II, a sensor of dysregulated calcium homeostasis, will inhibit arrhythmia in heart failure, and it is thus a novel target in arrhythmia. We propose to modify a small molecule inhibitor we developed for this protein kinase in ways that increase its potency, analyze the new inhibitors biochemically to ensure they have the desired properties, and then test for inhibition of arrhythmia in a mouse model as a proof-of-concept.