Elucidating the Role of Binding Kinetics in the Development of Abl Kinase Drug Resistance

项目摘要 小分子抑制剂的发展已经彻底改变了靶向治疗，特别是在药物治疗领域。 蛋白激酶然而，药物开发继续受到两个问题的困扰： 具有有限脱靶毒性的特定药物，以及（ii）对抗在 感兴趣的目标。结合动力学的作用，指的是配体的协会和解离速率，其目标， 在解决这些问题方面都没有得到充分的探索和利用。在非平衡环境中， 人体、药物结合和解离速率已被证明是候选药物上级优化参数 与传统的IC 50和KD指标相比，化合物的性能更好。此外，减少药物停留时间的突变， 定义为药物与其靶点结合的时间，可以推测为对治疗产生耐药性。 伊马替尼是合理药物设计的开创性成果，可抑制BCR-Abl癌蛋白， 慢性粒细胞白血病的死亡率降低了80%。伊马替尼对Abl激酶的特异性是由于其 构象选择性，它的成功引发了激烈的努力，发现特异性激酶抑制剂 在癌症和炎性疾病中失调。尽管其临床成功，复发伊马替尼治疗由于 耐药突变是常见的，并且对突变如何远离配体的基本理解 结合位点导致的耐药性仍然没有找到。我们已经初步确定了一系列患者源性 相反，耐药突变显示对伊马替尼的平衡亲和力没有变化。我们还 证实Abl N368 S突变体通过增加药物解离速率引起伊马替尼抗性。因此，我们认为， 我建议使用这些Abl激酶突变作为模型系统来探索结合动力学如何影响配体 特异性、效力和功效。我的中心假设是抑制剂结合或解离的改变 动力学可引起与抑制剂亲和力无关的抗性。我将通过测量 Abl激酶突变对药物滞留时间和功效的影响，并通过定义构象 Abl N368 S置换的变化。 通过这些研究，我将确定一种新类型的“动力学抗性”突变的结构机制 我相信这种耐药性会扩散到整个激酶组。我亦会阐释 Abl激酶的构象交换和伊马替尼解结合过程。另外，我会提供 如何通过缓慢的解离速率来延长体内药物作用， 最小的脱靶毒性。该提案的贡献是重要的，因为它们将验证更改 结合动力学作为高度治疗相关蛋白质家族中的一种新的耐药性机制 并作为改善药物特异性的可行策略。

PROJECT SUMMARY The development of small molecule inhibitors has revolutionized targeted therapeutics, especially in the field of protein kinases. However, pharmaceutical development continues to be plagued by two problems: (i) designing specific drugs with limited off-target toxicity and (ii) combating the occurrence of resistance mutations in the target of interest. The role of binding kinetics, referring to a ligand’s association and dissociation rate to its target, are underexplored and underexploited in addressing these issues. In the non-equilibrium environment of the human body, drug on- and off-rates have proven to be superior optimization parameters for candidate compounds than the traditional IC50 and KD metrics. Furthermore, mutations that reduce drug residence time, defined as how long a drug stays bound to its target, can presumably confer resistance to therapy. Imatinib, the seminal achievement of rational drug design, inhibits the BCR-Abl oncoprotein and has reduced the mortality rate for chronic myelogenous leukemia by 80%. Imatinib’s specificity for Abl kinase is due to its conformational selectivity, and its success has sparked intense efforts to discover specific inhibitors of kinases dysregulated in cancer and inflammatory disease. Despite its clinical success, relapse to imatinib therapy due to resistance mutations is common, and a fundamental understanding of how mutations distant from the ligand binding site cause resistance continues to elude us. We have preliminarily identified a series of patient-derived resistance mutations that paradoxically show no change in equilibrium affinity for imatinib. We have also validated that the Abl N368S mutant causes imatinib resistance by increasing drug dissociation rate. Therefore, I propose using these Abl kinase mutations as a model system to explore how binding kinetics affect ligand specificity, potency, and efficacy. My central hypothesis is that altered inhibitor binding or dissociation kinetics could cause resistance independent of inhibitor affinity. I will explore this hypothesis by measuring the effects of Abl kinase mutations on drug residence time and efficacy and by defining the conformational changes of the Abl N368S substitution. Through these studies, I will determine the structural mechanism of “kinetic resistance” mutations, a novel type of drug resistance which I believe extends throughout the kinome. I will also elucidate key structural factors in the conformational exchange of Abl kinase and the imatinib unbinding process. In addition, I will provide insight into how prolonging in vivo drug action through slow dissociation rates can be applied to develop drugs with minimal off-target toxicity. The contributions from this proposal are significant because they will validate altered binding kinetics as both a novel mechanism of drug resistance in a highly-therapeutically relevant protein family and as a viable strategy to improve drug specificity.