Novel Topoisomerase I Inhibitors

项目描述（由申请人提供）：本项目的长期目标是设计、合成和评价用于治疗癌症的新型拓扑异构酶I（Top1）抑制剂。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。这可能包括结构修饰，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设计策略将涉及通过药物化学、计算机图形分子建模、分子力学、从头算量子力学和生物化学研究来评估稳定抑制剂/酶/DNA三元复合物的基本力。此外，新型Top1抑制剂的设计将得到晶体学抑制剂/酶/DNA三元复合物的帮助，这将促进基于结构的药物设计。各种合成方法将用于合成新的Top I抑制剂，包括被称为“aromathecins”的茚并异喹啉-喜树碱杂合物、aromathecins的氮类似物和氮杂茚并异喹啉。 所得抗癌剂将通过连接低分子量归巢配体靶向癌细胞和实体瘤，所述低分子量归巢配体将在选择性摄取到癌细胞而不是正常细胞中后代谢除去。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以帮助阐明作用机制以及确定癌细胞培养物的NCI组中的选择性来评价缀合物。 在停滞切割复合物中连接Top I的Tyr 723与DNA的3 '-磷酸的磷酸二酯键被酪氨酰-DNA-磷酸二酯酶I（Tdp 1）水解。由于Tdp 1抑制剂抵消Top1抑制剂的作用，Tdp 1抑制剂可能与Top1抑制剂协同相互作用。该项目的目标是将Top1和Tdp 1抑制活性结合到相同的抗癌剂中，预期其比缺乏Tdp 1抑制活性的Top I抑制剂显著更有效。这将利用几种茚并异喹啉中Tdp 1抑制活性的独特发现。 将在多种测定中评价由本研究产生的Top1抑制剂，所述测定包括涉及：1）Top1介导的DNA切割反应; 2）Top1-DNA连接和切割复合物的可逆性; 3）切割复合物形成和逆转的动力学; 4）DNA解旋以监测嵌入; 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质连接链断裂; 7）癌细胞培养物中的细胞毒性测定，包括喜树碱抗性细胞系; 8）中空纤维研究和异种移植物测试; 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.