Mechanisms of resistance to ponatinib therapy in chronic myeloid leukemia

描述（由申请人提供）：2001年伊马替尼的引入使慢性粒细胞白血病（CML）成为许多患者可管理的疾病。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。这些抑制剂结合BCR-ABL1的激酶结构域，BCR-ABL1是CML的分子病因。然而，对于某些患者，BCR-ABL1突变导致TKI耐药和疾病进展。我们最近对一种新的TKI（泊那替尼）的表征导致了成功的临床试验，以评估其对TKI耐药CML的疗效。Ponatinib成功的关键是能够杀死具有突变BCR-ABL1的细胞。不幸的是，对于一些患者，泊那替尼治疗 由于出现耐药性，仅短暂有效。泊那替尼治疗前和治疗后样本的分析表明泊那替尼耐药的两种机制：（1）每个BCR-ABL 1分子有两个或多个突变，可阻止泊那替尼结合;（2）尽管BCR-ABL 1未突变，但由于激活了替代的促生存/抗程序性细胞死亡途径，BCR-ABL 1仍存活。目的1：确定BCR-ABL1复合突变在泊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做出自信的治疗决定。在泊那替尼治疗前和治疗期间使用最先进的技术对激酶结构域进行测序，将有助于更全面地了解复杂白血病人群，并提供有关突变在TKI耐药中作用的进一步信息。目的2：确定尽管BCR-ABL1持续抑制，但对泊那替尼耐药的原发性CML标本中的替代致癌途径。在BCR-ABL1未突变的患者中记录了TKI耐药，表明内源性存活途径的异常激活。为了揭示这些途径并探索其作为治疗靶点的适用性，我们将使用激酶抑制剂和siRNA文库结合泊那替尼筛选患者样本。这将提供有关每个白血病患者生存机制的信息，并将开始为TKI耐药CML的个性化治疗开辟道路。目的3：靶向TKI耐药CML中的STAT3。对TKI耐药细胞系的初步研究表明，STAT3是TKI耐药背景下异常信号通路的下游整合者。我们正在与一个化学家团队合作，开发越来越特异和活跃的STAT3抑制剂。我们创新了一种快速而强大的荧光素酶筛选，已经将最知名的STAT3抑制剂带到了CML研究的最前沿。总之，BCR-ABL1复合突变和旁路途径激活是CML治疗中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。这些研究的数据对于治疗TKI耐药的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.