Novel Topoisomerase I Inhibitors

项目描述（由申请人提供）：该项目的长期目标是设计、合成和评估新型拓扑异构酶I （Top1）抑制剂用于治疗癌症。临床研究将使临床结果揭示的未来问题得到立即有效的解决。这可能包括结构修改，以解决由药物毒性、耐药性、不利的药代动力学和缺乏效力引起的潜在问题。Top1设计策略将包括通过药物化学、计算机图形分子建模、分子力学、从头算量子力学和生化研究来评估稳定抑制剂/酶/DNA三元复合物的基本力。此外，晶体学抑制剂/酶/DNA的三元配合物将有助于新的Top1抑制剂的设计，这将有助于基于结构的药物设计。新的Top I抑制剂的合成将采用多种合成方法，包括吲哚异喹啉-喜树碱的混合物，称为“芳香素”，芳香素的氮类似物和叠氮异喹啉。由此产生的抗癌药物将通过低分子量的归家配体附着在癌细胞和实体肿瘤上，这些配体在选择性摄取到癌细胞而不是正常细胞后，会被代谢去除。将通过测试释放机制，监测细胞增殖抑制，阻断归巢配体与癌细胞的附着来帮助阐明作用机制，并确定NCI小组癌细胞培养物的选择性来评估缀合物。酪氨酸-DNA-磷酸二酯酶I （Tdp1）能水解酪氨酸-DNA-磷酸二酯键，将Top I的Tyr723与DNA的3'-磷酸连接起来。由于Tdp1抑制剂抵消了Top1抑制剂的作用，Tdp1抑制剂可能与Top1抑制剂协同作用。该项目的目标是将Top1和Tdp1的抑制活性结合到相同的抗癌药物中，预计这将比缺乏Tdp1抑制活性的Top I抑制剂更有效。这将利用在几种吲哚异喹啉中Tdp1抑制活性的独特发现。由本研究产生的Top1抑制剂将在各种试验中进行评估，包括：1)Top1介导的DNA切割反应；2)切割复合物的Top1-DNA连锁和可逆性；解理络合物形成与逆转动力学；4) DNA解绕监测插层；5)抑制top1介导的DNA松弛；6)哺乳动物细胞中抑制剂诱导的蛋白链断裂；7)癌细胞培养的细胞毒性测定，包括喜树碱耐药细胞系；8)中空纤维研究和异种移植试验；9)对非洲锥虫的抗生素活性。

DESCRIPTION (provided by applicant): The long-term goals of this project are to design, synthesize and evaluate novel topoisomerase I (Top1) inhibitors for the treatment of cancer. The clinical studies will allow future problems revealed by the clinical results to be addressed immediately and effectively. This could include structural modification to address potential problems resulting from drug toxicity, resistance, unfavorable pharmacokinetics, and lack of potency. The Top1 design strategy will involve an evaluation of the fundamental forces stabilizing the inhibitor/enzyme/DNA ternary complexes through medicinal chemistry, computer graphics molecular modeling, molecular mechanics, ab initio quantum mechanics, and biochemical studies. In addition, the design of new Top1 inhibitors will be aided by crystallography inhibitor/enzyme/DNA of ternary complexes, which will facilitate structure-based drug design. A variety of synthetic methods will be employed in the syntheses of new Top I inhibitors, including indenoisoquinoline-camptothecin hybrids termed "aromathecins", nitrogen analogues of the aromathecins, and azaindenoisoquinolines. The resulting anticancer agents will be targeted to cancer cells and solid tumors through attachment of low molecular weight homing ligands that will be removed metabolically after selective uptake into cancer cells as opposed to normal cells. The conjugates will be evaluated by testing the release mechanism, monitoring inhibition of cell proliferation, blocking the attachment of the homing ligand to cancer cells to help elucidate mechanism of action, and determining selectivities in the NCI panel of cancer cell cultures. The phosphodiester bond linking Tyr723 of Top I to the 3'-phosphate of DNA in stalled cleavage complexes is hydrolyzed by tyrosyl-DNA-phosphodiesterase I (Tdp1). Since Tdp1 inhibitors counteract the action of Top1 inhibitors, Tdp1 inhibitors might interact synergistically with Top1 inhibitors. A goal of this project is to incorporate both Top1 and Tdp1 inhibitory activities into the same anticancer agents, which are expected be significantly more potent than those of Top I inhibitors lacking Tdp1 inhibitory activity. This will exploit a unique discovery of Tdp1 inhibitory activity in several indenoisoquinolines. The Top1 inhibitors resulting from this study will be evaluated in a variety of assays including those involving: 1) Top1-mediated DNA cleavage reactions; 2) Top1-DNA linkage and reversibility of cleavage complexes; 3) kinetics of cleavage complex formation and reversal; 4) DNA unwinding to monitor intercalation; 5) inhibition of Top1-mediated DNA relaxation; 6) protein-linked strand breaks induced by inhibitors in mammalian cells; 7) cytotoxicity assays in cancer cell cultures, including camptothecin-resistant cells lines; 8) hollow fiber studies and xenograft testing; 9) antibiotic activity vs. African trypanosomes.