Cooperative lead development program for treatment of spinal muscular atrophy

描述（由申请人提供）：脊髓性肌萎缩症（SMA）是一种常见的肌营养不良症，是婴儿死亡的主要遗传原因。这种常染色体隐性遗传疾病的特征是由于运动神经元功能丧失而导致的进行性肌无力。SMA是由运动神经元存活（SMN）蛋白水平不足引起的，通常来自SMN1基因的纯合突变。一个几乎相同的拷贝基因SMN2，未能保护SMA的发展，因为其mRNA经历外显子7的选择性剪接。约10%的SMN2 RNA转录物包含外显子7，编码与SMN1相同的SMN蛋白。我们实施了一个新的铅发现计划，以确定药物样化合物，增加细胞内SMN蛋白水平。使用一种新的和改进的基于细胞的报告分析，我们与神经退行性疾病药物发现实验室，诺华基金会基因组学研究所和NIH化学基因组学中心合作，完成了三个大型化学多样性文库的高通量筛选。这些筛选已经鉴定了SMN蛋白表达的药物样激活剂，这些激活剂已经在二级测定中得到证实。这项为期三年的资助的第一个目标是基于我们已经确定的活性支架设计和合成更有效的化合物。然后，我们将研究出现的铅的药代动力学和急性毒理学。药物化学计划将修改这些化合物，以改善吸收和维持足够的组织水平，并制备用于动物给药的制剂。第二个目的是在SMA小鼠模型中测试最具活性和最合适的化合物在体内提高SMN蛋白水平的功效，并确定疾病的严重程度是否可以改善。该提案结合了六个团队的经验和人才，这些团队在SMA的分子生物学和临床前药物开发方面具有专业知识，并在神经退行性疾病新药设计方面具有领导地位。该提案的预测结果是鉴定出可增加SMA模型小鼠中SMN水平并恢复运动活性的合适的药物样化合物，这些药物样化合物可快速推进至人体试验。其最终目标是开发一种有效的治疗脊髓性肌萎缩症的药物。 公共卫生相关性：脊髓性肌萎缩症（SMA）是肌营养不良症的一种形式，是婴儿死亡的主要遗传原因，并且以较小的破坏性形式导致儿童和成人的症状性肌无力。所有形式的SMA都是由称为SMN的蛋白质水平不足引起的。SMA没有治疗方法。我们使用了一种策略来测试大量化合物增加细胞中SMN蛋白水平的能力。这项拨款申请要求资金用于最大限度地提高这些化合物的效力和药物样特性。然后，我们将在基因工程小鼠中测试它们的疗效，以复制SMA并测量它们的SMN水平和效果。发现一种增加SMN水平并改善SMA小鼠存活率的药物将是人类临床试验进展的重要里程碑。

DESCRIPTION (provided by applicant): Spinal Muscular Atrophy (SMA) is a common form of muscular dystrophy and the leading genetic cause of infant mortality. This autosomal recessive disorder is characterized by progressive muscle weakness due to loss of motor neuron function. SMA is caused by insufficient levels of the survival motor neuron (SMN) protein, usually from homozygous mutation of the SMN1 gene. A nearly identical copy gene, SMN2, fails to protect from development of SMA because its mRNA undergoes alternative splicing of exon 7. About 10% of SMN2 RNA transcripts include exon 7 and encode the same SMN protein as SMN1. We implemented a novel lead discovery program to identify drug-like compounds that increase intracellular SMN protein levels. Using a new and improved cell-based reporter assay, we completed three high-throughput screens of large chemical diversity libraries in collaborations with the Laboratory of Drug Discovery in Neurodegeneration, the Genomics Institute of Novartis Foundation, and the NIH Chemical Genomics Center. These screens have identified drug-like activators of SMN protein expression that have been confirmed in secondary assays. The first aim of this three-year grant is to design and synthesize more potent compounds based on the active scaffolds we have identified. We will then investigate the pharmacokinetics and acute toxicology of the leads that emerge. A medicinal chemistry program will modify these compounds for improved absorption and maintenance of adequate tissue levels and prepare formulations for their administration in animals. The second aim is to test the most active and pharmacologically suitable compounds in SMA mouse models for efficacy in raising SMN protein levels in vivo and to determine whether the severity of disease can be ameliorated. This proposal unites the experience and talents of six teams with expertise in molecular biology and pre-clinical drug development in SMA with leaders in design of novel medicines for neurodegenerative diseases. The predicted outcome of this proposal is identification of pharmacologically suitable drug-like compounds that increase SMN levels and restore motor activity in SMA model mice that can be rapidly advanced to human trials. The ultimate goal is to develop an effective drug treatment of spinal muscular atrophy. PUBLIC HEALTH RELEVANCE: Spinal muscular atrophy (SMA), a form of muscular dystrophy, is the leading genetic cause of infant death, and in less devastating forms leads to symptomatic muscle weakness in children and adults. All forms of SMA result from insufficient levels of the protein called SMN. There is no treatment for SMA. We used a strategy to test very large collections of chemical compounds for ability to increase SMN protein levels in cells. This grant application requests funds for maximizing the potency and drug-like properties of these compounds. We will then test their efficacy in mice genetically engineered to reproduce SMA and measure their SMN levels and effects. Discovery of a medicine that increases SMN levels and improves SMA mouse survival would represent an important milestone for advancement to human clinical trials.