Polymerase Inhibitors of Respiratory Syncytial Virus

总结 呼吸道合胞病毒（RSV）是婴儿因感染性疾病住院的主要原因， 美国的在季节性流行期间，成人的定期再感染可在一生中发生，但可 特别是对老年人和免疫功能低下的人有生命危险。尽管进行了广泛的研究， 疫苗保护是可用的，目前基于抗体治疗的免疫预防仍然保留给 高危患者。认识到对有效、适用和耐受性良好的RSV的临床需求未得到满足 该项目的目标是追求严格的临床前表征和降低风险， 两个口服有效的RSV聚合酶抑制剂类，我们已经确定在以前的工作计划 和试点研究。 开创RSV报告病毒技术，完成大规模高通量抗RSV 药物筛选活动，我们已经确定了两个结构和机制不同的命中类， 抑制RSV RNA依赖性RNA聚合酶（RdRP）复合物，一种新的尿苷核糖核苷类似物， 启动子处RdRP介导的RNA合成起始的非竞争性抑制剂。目前的线索显示 对RSV报告菌株和临床分离株的有效活性， 疾病相关的分化良好的原代人气道上皮细胞培养物，良好的药代动力学（PK） 具有持续血药浓度和良好的初步耐受性的曲线。试点研究已经建立了 RSV感染小鼠模型中口服有效性的概念验证，降低肺病毒载量和标志物 RSV细支气管炎的临床体征。该项目将双管齐下， 战略，同时开发底物类似物和非竞争性抑制剂类， 减轻早期失败的风险或为将来作为伴随药物使用奠定实验基础。 最初的方法将分别针对这两个系列，旨在确定和解决潜在的 在这个过程中，早期的特定类别的负债。核糖核苷类似物的研究显示 活性三磷酸盐形式的浓度和灭菌口服抗RSV功效。在编写正式的 开发时，该类药物将接受作用机制表征、耐药性分析， RSV靶向和脱靶效应评估（目标1）。第一代非竞争性抑制剂 已经成功地进行了耐药性、细胞毒性和机制分析，但必须进行最终结构 和QSAR指导的效价和PK特性的合成优化，以揭示其全部抗病毒潜力（目的是 2）。将使用RSV感染的小鼠模型降低任何一类新出现的确认的导联的风险， 将评估化合物经历的RSV群体的发病机制，并将PK特征与 在原代人气道上皮细胞培养物中的性能， 在相关人体组织模型中，动态药物浓度对抗病毒疗效和安全范围的影响（目的3）。

Summary Respiratory syncytial virus (RSV) is the primary cause of infant hospitalization from infectious diseases in the United States. Regular re-infection of adults can occur throughout life during seasonal epidemics, but can be life-threatening especially to the elderly and the immunocompromised. Despite extensive research, no vaccine protection is available and current antibody therapy-based immunoprophylaxis remains reserved for high-risk patients. Recognizing the unmet clinical need for efficacious, applicable, and well-tolerated RSV therapeutics, it is the goal of this project to pursue a rigorous preclinical characterization and de-risking program of two orally efficacious RSV polymerase inhibitor classes that we have identified in previous work and pilot studies. Having pioneered RSV reporter virus technology and completed large-scale high-throughput anti-RSV drug screening campaigns, we have identified two structurally and mechanistically distinct hit classes that both inhibit the RSV RNA-dependent RNA polymerase (RdRP) complex, a novel uridine ribonucleoside analog and a non-competitive inhibitor of initiation of RdRP-mediated RNA synthesis at the promoter. Current leads show potent activity against RSV reporter strains and clinical isolates, nanomolar inhibitory concentrations in disease-relevant well-differentiated primary human airway epithelia cultures, good pharmacokinetic (PK) profiles with sustained plasma concentrations, and good preliminary tolerability. Pilot studies have established proof-of-concept of oral efficacy in the mouse model of RSV infection, reducing lung viral load and hallmark clinical signs of RSV bronchiolitis. This project will pursue the RSV polymerase target in a two-pronged strategy, developing the substrate-analog and non-competitive inhibitor classes simultaneously to proactively mitigate the risk of early stage failure or lay the experimental foundation for future use as companion drugs. The initial approach will be tailored individually to either series, designed to identify and address potential class-specific liabilities early in the process. The ribonucleoside analog lead has shown sustained tissue concentrations of the active triphosphate form and sterilizing oral anti-RSV efficacy. In preparation of formal development, this class will be subjected to mechanism of action characterization, resistance profiling against the RSV target, and assessment of off-target effects (aim 1). The first-generation non-competitive inhibitor lead has been successfully resistance, cytotoxicity, and mechanism profiled, but must be subjected to final structure and QSAR-guided synthetic optimization of potency and PK properties to uncover its full antiviral potential (aim 2). Emerging confirmed leads of either class will be de-risked using the mouse model of RSV infection, pathogenesis of compound-experienced RSV populations will be assessed, and PK profiles correlated with performance in primary human airway epithelium cultures to inform simulations of the impact of physiological, dynamic drug concentrations on antiviral efficacy and safety margin in relevant human tissue models (aim 3).