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修复能力水平升高，我们建议可以在治疗上利用恶性肿瘤的这一共同特征。我们通过开发特异性抑制HR并克服与癌细胞中HR上调相关的治疗抗性的候选药物来支持这一中心假设。我们的更新申请建立在这些药物发现工作的基础上，并探索了靶向中心HR蛋白RAD51的化合物的新应用。本研究的主要假设和目标如下：首先，我们将进一步优化RAD51抑制化合物，以克服肿瘤对化疗和放疗的抵抗。我们将开发一类新的化合物，靶向RAD51的专门活性，我们假设这将产生比更广泛的RAD51抑制剂更少的毒性。其次，我们假设RAD51抑制化合物将抑制一种称为端粒（ALT）替代延长的HR相关机制，这是某些癌症亚型细胞增殖所必需的。由于正常的人类细胞专门利用端粒酶而不是ALT来维持其端粒，我们预测RAD51抑制将迫使ALT依赖性肿瘤细胞衰老，同时产生很少或没有正常组织毒性。第三，我们假设RAD51刺激化合物可以特异性地促进过表达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过表达导致癌细胞中未受损染色质上形成毒性RAD51蛋白复合物。我们还表明，RAD51刺激化合物在易感癌症类型中加重了这种潜在的毒性特征。 所有这些假设都将使用相同的三个综合目标进行测试，其中包括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。具体而言，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学性质的靶向化学修饰进行优化。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测定来表征RAD51调节化合物的活性和特异性。第三个目标是在动物模型中验证最优先的化合物。将在两种小鼠模型中测试RAD51抑制性化合物以证实它们：1）使人肿瘤异种移植物对用复制破坏性化疗药物和/或辐射的治疗敏感，和2）防止ALT依赖性癌细胞在小鼠中形成肺转移。将通过催化未受损染色质上的毒性RAD 51蛋白聚集来测试RAD 51刺激化合物缩小易感肿瘤类型的能力。我们的最终目标是产生两个或三个候选药物，适用于扩展的药理学测试和随后的临床试验测试。

 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.