Chemical Probes Targeting Gliomas with IDH Mutation

描述（由申请人提供）：异柠檬酸脱氢酶（IDH）是三羧酸循环中的关键酶之一，使用NADP+催化异柠檬酸转化为α-酮基谷氨酸（α-KG）。大量人胶质瘤的DNA测序已经揭示，约75%的低-中等级别胶质瘤和继发性多形性胶质母细胞瘤（GBM，一种高致死性形式的脑肿瘤）携带IDH突变，其中IDH 1 R132 H突变占主导地位（约90%）。遗传学研究发现IDH突变总是杂合的，这表明野生型酶对正常细胞和肿瘤细胞都是必需的，IDH突变是胶质瘤发生的早期和关键事件。突变蛋白的生物化学表征显示它们在将异柠檬酸转化为α-KG中无活性。相反，所有的突变蛋白，例如，IDH 1（R132 H）具有新的酶活性：它们催化α-KG用NADPH还原为D-2-羟基谷氨酸（2-HG）。这种新功能导致携带IDH突变的原发性肿瘤细胞中2-HG水平大大升高（> 100倍）。越来越多的证据强烈支持2-HG是一种致癌代谢物，突变型IDH是干预的靶点。虽然高水平的2-HG对人体健康（尤其是中枢神经系统）的危害是显而易见的，但抑制突变型IDH是否能阻断这类肿瘤细胞的生长或诱导其凋亡仍有待回答。这是因为迄今为止还没有突变IDH的抑制剂。此外，RNA干扰（RNAi）不适合这项研究，因为它也会敲低野生型IDH酶，而野生型IDH酶的功能对正常细胞和肿瘤细胞都是必不可少的。第一个具体目标是使用药物化学，蛋白质X射线晶体学和定量构效关系（QSAR）来开发IDH 1（R132 H）的有效和选择性抑制剂。第二个具体目标是测试目标1中合成的化合物的体外生物活性以及所选化合物的药代动力学和毒理学性质。第三个具体目标是确定我们的有效IDH 1（R132 H）抑制剂在脑内异种移植小鼠模型中的体内抗肿瘤活性，以及使用分子和细胞生物学方法来鉴定这些新型抑制剂的作用机制。

DESCRIPTION (provided by applicant): Isocitrate dehydrogenase (IDH) is one of the key enzymes in the tricarboxylic acid cycle, catalyzing the conversion of isocitric acid to α-ketoglutaric acid (α-KG) using NADP+. DNA sequencing of a large number of human gilomas has revealed that ~75% of low - medium grade gliomas and secondary glioblastoma multiforme (GBM, a highly lethal form of brain tumor) carry IDH mutations, with IDH1 R132H mutation being predominant (~90%). Genetic investigations have found that IDH mutations are always heterozygous, suggesting the wild-type enzyme is essential for both normal and tumor cells, and IDH mutation is an early and critical event in the glioma tumorigenesis. Biochemical characterization of the mutant proteins revealed that they are inactive in converting isocitrate to α-KG. Rather, all of the mutant proteins, e.g., IDH1(R132H), possess a new enzymatic activity: they catalyze the reduction of α-KG to D-2-hydroxyglutaric acid (2-HG) using NADPH. This neo-function is responsible for the greatly elevated (>100x) level of 2-HG in primary tumor cells bearing IDH mutations. Growing evidence strongly supports 2-HG is an onco-metabolite and mutant IDH a target for intervention. Although it is clear that a high level of 2-HG is very harmfu to human health (especially central nervous system), whether inhibition of mutant IDH blocks the growth or induces apoptosis of this type of tumor cells remains to be answered. This is because there have been no inhibitors of mutant IDH to date. In addition, RNA interference (RNAi) is not appropriate for this study, since it will also knock down the wild-type IDH enzyme, whose function is essential for both normal and tumor cells. The first Specific Aim is to use medicinal chemistry, protein X-ray crystallography and quantitative structure activity relationship (QSAR) to develop potent and selective inhibitors of IDH1(R132H). The second Specific Aim is to test in vitro biological activities of compounds synthesized in Aim 1 as well as pharmacokinetic and toxicological properties of selected compounds. The third Specific Aim is to determine the in vivo antitumor activity of our potent IDH1(R132H) inhibitors in intra-cerebral xenograft mouse models as well as to use molecular and cell biology methods to identify the mechanisms of action of these novel inhibitors.