RAD51 Inhibitors for Chemotherapy and Radiation Therapy

 描述(由申请人提供)：人类恶性肿瘤表现出同源重组(HR)DNA修复熟练程度的提高，我们建议这一常见的恶性肿瘤特征可以用于治疗。我们通过开发特定抑制HR并克服与癌细胞HR上调相关的治疗耐药性的候选药物来支持这一中心假设。我们的续订申请建立在这些药物发现努力的基础上，并探索以中央HR蛋白RAD51为靶点的化合物的新应用。这一建议的主要假设和目标如下：第一，我们将进一步优化RAD51抑制化合物，目标是克服肿瘤对化疗和放疗的耐药性。我们将开发一类针对RAD51特殊活性的新型化合物，我们假设这种化合物产生的毒性比更通用的RAD51抑制剂更小。其次，我们假设RAD51抑制化合物将失活一种称为替代端粒延长(ALT)的HR相关机制，这是某些癌症亚型细胞增殖所必需的。由于正常人类细胞只利用端粒酶而不是ALT来维持其端粒，我们预测RAD51抑制将迫使ALT依赖的肿瘤细胞衰老，同时对正常组织几乎没有毒性。第三，我们假设RAD51刺激化合物可以特异性地促进过度表达RAD51的肿瘤细胞的死亡。这一概念建立在我们的观察基础上，即高水平的RAD51过度表达会导致癌细胞中未受损的染色质上形成有毒的RAD51蛋白质复合体。我们还表明，RAD51刺激化合物在易感癌症类型中强调了这一潜在的毒性特征。所有这些假设都将使用相同的三个综合目标进行测试，这三个目标包含了广泛的药物开发方法。第一个目标将包括药物化学优化和ADMET测试。具体地说，我们的先导RAD51调节化合物的结构将通过旨在改善活性和药理性质的有针对性的化学修饰来优化。在第二个目标中，我们将使用纯化的体外生化系统和基于细胞的分析来表征RAD51调节化合物的活性和特异性。第三个目标将在动物模型中验证最优先的化合物。RAD51抑制化合物将在两个小鼠模型中进行测试，以确认它们：1)使人类肿瘤移植瘤对复制干扰化疗药物和/或放射治疗敏感，2)防止ALT依赖的癌细胞在小鼠体内形成肺转移。RAD51刺激化合物将通过催化有毒的RAD51蛋白聚集在未受损的染色质上，测试缩小敏感肿瘤类型的能力。我们的最终目标是产生两到三种候选药物，适合在临床试验中进行扩展的药理测试和后续测试。

 DESCRIPTION (provided by applicant): Human malignancies exhibit elevated levels of homologous recombinational (HR) DNA repair proficiency, and we propose that this common feature of malignancy can be exploited therapeutically. We have supported this central hypothesis by developing drug candidates that specifically inhibit HR and overcome the treatment resistance associated with HR up-regulation in cancer cells. Our renewal application builds on these drug discovery efforts and explores novel applications for compounds that target the central HR protein, RAD51. The major hypotheses and goals of this proposal are as follow: First, we will further optimize RAD51-inhibitory compounds with the goal of overcoming tumor resistance to chemotherapy and radiotherapy. We will develop a novel class of compounds that target a specialized activity of RAD51, which we hypothesize will generate less toxicity than more generalized RAD51 inhibitors. Second, we hypothesize that RAD51-inhibitory compounds will inactivate an HR-related mechanism called alternative lengthening of telomere (ALT), which is required for cell proliferation in some cancer subtypes. Since normal human cells exclusively utilize telomerase instead of ALT to maintain their telomeres, we predict that RAD51 inhibition will force ALT-dependent tumor cells into senescence while exerting little or no normal tissue toxicity. Third, we hypothesize that RAD51-stimulatory compounds can specifically promote death in tumor cells that overexpress RAD51. This concept builds on our observations that high levels of RAD51 overexpression cause the formation of toxic RAD51 protein complexes on undamaged chromatin in cancer cells. We have also shown that RAD51-stimulatory compounds accentuate this potentially toxic feature in susceptible cancer types. All of these hypotheses wil be tested using the same three integrated aims, which incorporate a wide range of drug development methods. The first aim will consist of medicinal chemistry optimization and ADMET testing. Specifically, the structures of our lead RAD51-modulating compounds will be optimized via targeted chemical modifications aimed at improving both activity and pharmacologic properties. In the second aim, we will characterize the activity and specificity of RAD51-modulating compounds, using both purified in vitro biochemical systems and cell-based assays. The third aim will validate the highest priority compounds in animal models. RAD51-inhibitory compounds will be tested in two mouse models to confirm that they: 1) sensitize human tumor xenografts to treatment with replication-disrupting chemotherapeutic drugs and/or radiation, and 2) prevent the ALT-dependent cancer cells from forming lung metastases in mice. RAD51- stimulatory compounds will be tested for the ability to shrink susceptible tumor types, by catalyzing toxic RAD51 protein aggregation on undamaged chromatin. Our ultimate goal is to generate two or three drug candidates that are suitable for extended pharmacologic testing and subsequent testing in clinical trials.