Developing CDK12 inhibitors to treat Myotonic Dystrophy

我们的目标是开发一种治疗1型肌强直性营养不良（DM1）的方法，这是一种严重的、进行性的、使人衰弱的疾病，影响包括骨骼肌、心脏和大脑在内的一系列系统。目前还没有治疗这种疾病的方法。DM1是由一种名为DMPK的基因的不寻常突变引起的。它被称为扩展突变，因为DNA的短序列被DM1大大扩展。有缺陷的DNA被制成RNA，被困在病人的细胞核中，在那里形成独特的斑点或病灶，在显微镜下可以检测到。我们开发了一种检测方法来识别能够去除患者细胞中斑点的小分子，因为它们将为开发治疗DM1的方法提供起点。药物发现项目通常会确定所谓的可药物靶标，即一种可以用小分子靶向的蛋白质。我们已经证明，去除核病灶的一组小分子抑制剂具有称为细胞周期蛋白依赖性激酶12 （CDK12）的共同靶标。我们还表明，CDK12与DM1细胞中的重复扩增灶共定位，其水平在DM1细胞系和DM1患者肌肉活检中升高。我们对CDK12知之甚少，因为它对修饰其他蛋白质很重要，尤其是RNA聚合酶II。它在应激反应中发挥作用，并参与长基因的转录（从长基因中制造RNA）。它也可能在细胞内的其他过程中发挥作用。尽管CDK12有许多可能的作用，但我们认为它是DM1治疗的一个很好的靶点。例如，已经产生了一种基因修饰的突变小鼠，它缺少Cdk12基因的一个拷贝，这些小鼠被称为敲除小鼠，缺乏Cdk12的拷贝，可以存活，看起来完全正常。这给了我们信心，我们应该能够将DM1患者中Cdk12的升高水平降低到正常水平。我们期望这样的减少可以防止病人的细胞产生错误的RNA，并消除我们在显微镜下看到的斑点。我们的初步结果表明这是可能的。我们已经开展了一项药物开发计划，以生产新型和选择性CDK12抑制剂。我们已经证明，这些化合物影响CDK12并降低重复扩增RNA的水平，在患者来源的细胞系中去除核病灶。我们的先导化合物在DM1小鼠模型的体内研究中显示出令人鼓舞的活性。因此，我们的先导系列分子是DM1治疗进一步开发的优秀候选者，该项目的重点是完成一项药物开发计划，称为先导优化调查，以推进我们的分子临床前研究。

Our aim is to develop a treatment for Myotonic Dystrophy type 1 (DM1), which is a severe, progressive, debilitating condition which affects a range of systems including skeletal muscle heart and brain. There is currently no treatment available for this condition. DM1 is caused by an unusual mutation in a gene called DMPK. It is called an expansion mutation because a short sequence of DNA is greatly expanded with DM1. The faulty DNA is made into RNA which gets trapped in the nuclei of patient's cells where it forms distinct spots or foci, detectable down a microscope. We developed an assay to identify small molecules that get rid of the spots in patient's cells as they would provide the starting point to develop a treatment for DM1. Drug discovery programmes typically identify what is known as a druggable target, that is a protein that can be targeted with a small molecule. We have shown that the set of small molecule inhibitors that remove nuclear foci have as their common target a protein called cyclin-dependent kinase 12 (CDK12). We have also shown that CDK12 co-locates with repeat expansion foci in DM1 cells and its levels are elevated in DM1 cell lines and in DM1 patient muscle biopsies. Quite a bit is known about CDK12 as it is important for modifying other proteins in particular one called RNA polymerase II. It plays a role in the stress response, and it is involved in the transcription (making RNA from) of long genes. It may also play a role in other processes within the cell. Despite the many possible roles for CDK12 we think it makes a good target for DM1 therapy. For example a genetically modified mutant mouse has been produced which lacks one copy of the Cdk12 gene and these mice called knockout mice, lacking a copy of Cdk12 are viable and appear perfectly normal. This gives us confidence that we should be able to reduce to normal the increased levels of Cdk12 in DM1 patients. We expect such a reduction to prevent the patient's cells making the faulty RNA and eliminate the spots we see down the microscope. Our initial results suggest this may be possible. We have undertaken a drug development programme to produce novel and selective CDK12 inhibitors. We have shown that these compounds affect CDK12 and reduce the levels of repeat expansion RNA, removing nuclear foci in patient-derived cell lines. Our lead compound showed encouraging activity in an in vivo study using a mouse model of DM1. Thus, our lead series of molecules are excellent candidates for further development for treatment of DM1 and this project is focussed on completing a drug development programme, called a Lead Optimisation investigation to progress our molecules towards pre-clinical studies.