Improved therapeutic approaches for hematological disorder treated with tyrosine

描述（由申请人提供）：慢性髓性白血病（CML）是一种造血干细胞疾病，目前使用BCR/ABL酪氨酸激酶抑制剂如伊马替尼、达沙替尼和尼洛替尼治疗。临床复发是常见的，给成功的酪氨酸激酶抑制剂（TKI）治疗带来了巨大的挑战。ABL激酶结构域突变是伊马替尼耐药（IMR）的主要机制。第二代BCR/ABL抑制剂尼罗替尼和达沙替尼可有效抑制IMR变异，但对看门人突变体T315I无效。gatekeeper残基突变介导广谱耐药，是酪氨酸激酶抑制剂治疗如ABL、KIT、SRC、PDGFRA、PDGFRB和EGFR耐药的常见机制。最近，我们对这些激酶中的看门人突变进行了表征，并发现用一个庞大的疏水残基取代看门人苏氨酸，通过稳定在活性状态下组装的“疏水脊”来激活激酶。我们提出下一代抑制剂应该破坏活性态的组装并稳定非活性态。这项工作使我们开发了第三代ABL激酶抑制剂AP24163， AP24534和GNF-5。鉴于我们对第一代和第二代抑制剂的数据和经验，对第三代抑制剂的耐药性很可能也会发展。最近，我们已经证明第三代抑制剂AP24163 -临床药物AP24534的母体化合物-特异性地选择我们没有任何治疗选择的ABL激酶的化合物突变。该提案旨在鉴定对第三代临床抑制剂AP24534 （Ponatinib）的耐药突变。复合突变主要出现在ABL激酶的变构位点。本研究旨在研究复合突变产生耐药性的机制，并开发小分子抗变构抑制剂靶向抗变构位点的策略。为此，我们已经确定了一个独特的疏水模块-疏水环-控制激酶调节。我们预计，对这种疏水基序的详细描述将有助于我们开发新的变构抑制剂，这些抑制剂可以与ATP竞争性抑制剂联合使用，以抑制所有形式的抗性突变。

DESCRIPTION (provided by applicant): Chronic myeloid leukemia (CML) is a hematopoietic stem cell disorder and currently treated by BCR/ABL tyrosine kinase inhibitors such as Imatinib, Dasatinib and Nilotinib. Clinical relapses are common and pose great challenge for successful tyrosine kinase inhibitor (TKI) therapy. Mutations in the ABL kinase domain are the principal mechanism of Imatinib resistance (IMR). The second-generation BCR/ABL inhibitors Nilotinib and Dasatinib effectively inhibit IMR variants, but are ineffective against the gatekeeper mutant, T315I. Mutation of the gatekeeper residue mediates broad-spectrum drug resistance and is a common mechanism of resistance across tyrosine kinase inhibitor therapy such as ABL, KIT, SRC, PDGFRA, PDGFRB and EGFR. Recently, we have characterized the gatekeeper mutations in these kinases and discovered that the substitution of a bulky hydrophobic residue for the gatekeeper threonine activates the kinase by stabilizing the "hydrophobic spine" assembled during the active state. We proposed that the next-generation inhibitor should disrupt the assembly of active state and stabilize the inactive state. This work has led us to develop third-generation ABL kinase inhibitors, AP24163, AP24534 and GNF-5. Given our data and experiences with first and second-generation inhibitors, it is likely that resistance to third-generation inhibitors will develop as well. Recently we have shown that the third-generation inhibitor AP24163 - the parent compound of the clinical agent AP24534 - specifically selects for compound mutations in ABL kinase to which we do not have any therapeutic option. This proposal is aimed to identify drug resistant mutations against third generation clinical inhibitors AP24534 (Ponatinib). Compound mutations are mostly presented from the allosteric sites of the ABL kinase. This proposal is aimed to study the mechanism employed by the compound mutations to confer resistance and to develop strategies to target the allosteric sites by small molecule allosteric inhibitors. Towards this end we have identified a unique hydrophobic module- hydrophobic girdle-that governs kinase regulation. We anticipate that a detail characterization of this hydrophobic-motif will help us in developing new allosteric inhibitors tha can be used in combination with ATP- competitive inhibitors to suppress all forms resistant mutations.