Mechanisms of resistance to ponatinib therapy in chronic myeloid leukemia

描述(申请人提供)：2001年伊马替尼的引入使慢性粒细胞白血病(CML)成为许多患者可控制的疾病。酪氨酸激酶抑制剂(TKI)，包括伊马替尼、尼洛替尼和达沙替尼，现在是CML患者的常规治疗方法。这些抑制剂结合BCR-ABL1的激活域，BCR-ABL1是CML的分子病因。然而，对于一些患者，bcr-abl1突变会导致TKI耐药和疾病进展。我们最近对一种新的TKI进行了鉴定，Ponatinib导致了成功的临床试验，以评估其对TKI耐药CML的疗效。波纳替尼成功的关键是有能力杀死突变的bcr-abl1细胞。不幸的是，对一些患者来说，波纳替尼疗法 由于抗药性的出现，只能暂时有效。对Ponatinib治疗前后样本的分析表明，Ponatinib耐药有两种机制：(1)每个BCR-ABL1分子有两个或更多的突变阻止Ponatinib结合；(2)尽管BCR-ABL1未发生突变，但由于激活了另一种促进生存/反编程的细胞死亡途径，BCR-ABL1仍然存活。目的1：确定bcr-abl1复合突变在波那替尼耐药中的作用，并确定恢复bcr-abl1抑制的策略。这些信息将使临床医生能够从诊断开始就做出自信的治疗决定。使用最先进的技术对波纳替尼治疗前和治疗期间的激酶结构域进行测序将使我们能够更全面地了解复杂的白血病人群，并提供关于突变在TKI耐药中所起作用的进一步信息。目的2：在对bcr-abl1持续抑制的原发慢性粒细胞白血病标本中发现对波纳替尼耐药的替代致癌途径。在BCR-ABL1未发生突变的患者中发现TKI抵抗，这表明内源性生存通路异常激活。为了揭示这些途径并探索它们作为治疗靶点的适宜性，我们将使用激酶抑制剂和siRNA文库结合poatinib来筛选患者样本。这将提供有关每个患者白血病存活机制的信息，并将开始为耐TKI的CML建立一条个性化治疗之路。目的3：针对TKI耐药的慢性粒细胞白血病中的STAT3。对TKI耐药细胞株的初步研究表明，在TKI耐药的设置中，STAT3是异常信号通路的下游整合因子。我们正在与一组化学家合作，开发越来越特异和活性更高的STAT3抑制剂。我们创新了一种快速而强大的荧光素酶筛查，它已经将最著名的STAT3抑制剂送到了慢性粒细胞白血病研究的前沿。总之，BCR-ABL1复合突变和替代通路激活是CML治疗中尚未满足的临床挑战的来源，我们提出了一个平台来设计和实施新的策略来克服这两种耐药机制。这些研究的数据将对治疗耐TKI的CML患者至关重要，并将影响许多其他耐药癌症的治疗。

DESCRIPTION (provided by applicant): The introduction of imatinib in 2001 made chronic myeloid leukemia (CML) a manageable disease for many patients. Tyrosine kinase inhibitors (TKIs), including imatinib, nilotinib, and dasatinib, are now routine therapy for patients with CML These inhibitors bind the kinase domain of BCR-ABL1, the fusion protein that is the molecular cause of CML. However, for some patients, BCR-ABL1 mutations lead to TKI-resistance and progressive disease. Our recent characterization of a new TKI, ponatinib, led to successful clinical trials to evaluate its efficacy for TKI-resistant CML. The key to ponatinib's success is is ability to kill cells with mutated BCR-ABL1. Unfortunately, for some patients, ponatinib therapy is only transiently effective due to onset of resistance. Analysis of pre- and post-ponatinib treatment samples suggests two mechanisms of ponatinib resistance: (1) two or more mutations per BCR-ABL1 molecule that prevent ponatinib binding and (2) survival despite non-mutated, inhibited BCR-ABL1 due to activation of alternative pro-survival/anti-programmed cell death pathways. Aim 1: Determine the role of BCR-ABL1 compound mutations in resistance to ponatinib and identify strategies to restore BCR-ABL1 inhibition. This information will enable clinicians to make confident treatment decisions starting at diagnosis. Sequencing the kinase domain before and during ponatinib treatment with the most advanced technology will allow for a more complete understanding of the complex leukemia population and provide further information about the role of mutations in TKI resistance. Aim 2: Identify alternative oncogenic pathways in primary CML specimens exhibiting resistance to ponatinib despite sustained inhibition of BCR-ABL1. TKI resistance is documented in patients whose BCR- ABL1 is not mutated, indicating anomalous activation of an endogenous survival pathway. To uncover these pathways and explore their suitability as therapeutic targets, we will screen patient samples using kinase inhibitor and siRNA libraries in conjunction with ponatinib. This will provide information about the mechanism of survival of each individual patient's leukemia and will begin building a road toward personalized therapy for TKI-resistant CML. Aim 3: Target STAT3 in TKI-resistant CML. Preliminary studies with TKI-resistant cell lines indicate STAT3 as a downstream integrator of aberrant signaling pathways in the setting of TKI resistance. We are working with a team of chemists to develop increasingly specific and active STAT3 inhibitors. We have innovated a rapid and robust luciferase screen that has already delivered the best known STAT3 inhibitors to the forefront of CML research. In summary, BCR-ABL1 compound mutations and alternative pathway activation are the sources of unmet clinical challenges in CML treatment and we propose a platform to design and implement new strategies to overcome both resistance mechanisms. Data from these studies will be critical for treating TKI-resistant CML patients and will impact therapy for many other drug resistant cancers.