Development of Trabectedin Analogs that Target the EWS-FLI1 Transcription Factor

 描述（由申请人提供）：尤文肉瘤是一种预后不良的骨和软组织肿瘤，特别是复发或转移性疾病患者，总生存率低于30%。自目前采用的5种药物化疗方案建立以来，在过去25年中，这种疾病患者的生存率几乎没有改善，治疗方法也没有改变。因此，非常需要直接靶向负责尤文肉瘤细胞存活的基因的新化合物和方法。该提案的目标是建立一种以抑制这种肿瘤的定义分子特征EWS-FLI 1转录因子为中心的治疗方法。尤文肉瘤的生存完全依赖于EWS-FLI 1的持续表达。这种致癌转录因子改变了500多个基因的表达，以创建负责尤文肉瘤细胞持续增殖、耐药性甚至转移的转录程序。靶向EWS-FLI 1的挑战在于该蛋白是一种转录因子，并且被广泛认为是一种“不可治疗的靶标”。在这个提议中，我们采用了一种从床边到工作台再回来的方法来开发一种靶向EWS-FLI 1的疗法，使用一种称为trabectedin的化合物作为骨架。在早期I期研究中，1例尤文肉瘤患者接受Trabectedin治疗后完全缓解。与这一结果一致，我们以前已经表明，trabectedin干扰EWS-FLI 1转录因子的活性。不幸的是，后续的II期临床试验并没有证实这种药物在尤文肉瘤中的活性。在这个建议中，我们假设尤文肉瘤患者在II期研究中对trabectedin反应失败是由于药物的治疗指数差，限制了trabectedin的暴露水平，不足以阻断EWS-FLI 1。我们认为限制这些血清水平的药物相关毒性是在正常细胞以及尤文肉瘤细胞中引起毒性的附带DNA损伤。因此，为了与NIH了解极端临床反应者的倡议保持一致， 根据该提案，我们将评估82种曲贝替丁类似物，以鉴定具有改善的治疗指数的化合物，其将允许在患者中阻断EWS-FLI 1。在这个过程中，我们将确切地确定药物如何阻断EWS-FLI 1活性，以及药物相关的DNA损伤对这种活性的相对贡献。最后，我们将提出一种新的联合治疗，改善EWS-FLI 1抑制，重点是药物相关的DNA损伤，特别是尤文肉瘤细胞。总之，这些结果将为以EWS-FLI 1阻断为中心的基于曲贝替丁的治疗的临床转化提供基础，以改善患者存活率。

 DESCRIPTION (provided by applicant): Ewing sarcoma is a bone and soft tissue tumor with a poor prognosis, particularly for patients with relapsed or metastatic disease, where overall survival is less than 30%. In the last 25 years since the establishment of the currently employed 5-drug chemotherapeutic regimen, there has been very little improvement in survival and no change in the therapy for patients with this disease. Therefore, there is a great need for new compounds and approaches that directly target the genes responsible for Ewing sarcoma cell survival. The goal of this proposal is to build a therapy centered on the suppression of the defining molecular feature of this tumor, the EWS-FLI1 transcription factor. Ewing sarcoma absolutely depends on continued expression of EWS-FLI1 for cell survival. This oncogenic transcription factor alters the expression of more than 500 genes to create the transcriptional program responsible for the continued proliferation of Ewing sarcoma cells, drug resistance and even metastasis. The challenge in targeting EWS-FLI1 is that the protein is a transcription factor and widely believed to be an "undruggable target". In this proposal, we employ a bedside-to-bench and back again approach to develop a therapy that targets EWS-FLI1 using a compound called trabectedin as the backbone. In an early phase I study, a patient with Ewing sarcoma treated with Trabectedin achieved a complete response to this drug. Consistent with this result, we have previously shown that trabectedin interferes with the activity of the EWS-FLI1 transcription factor. Unfortunately, a follow-up phase II trial did not confirm that activity of th drug in Ewing sarcoma. In this proposal, we hypothesize that the failure of Ewing sarcoma patients to respond to the trabectedin in the phase II study was due to a poor therapeutic index of the drug that limited the exposure of trabectedin to levels that were not high enough to block EWS-FLI1. We believe that the drug associated toxicity that limited these serum levels was the collateral DNA damage that caused toxicity in normal cells as well as Ewing sarcoma cells. Therefore, in keeping with the NIH initiative of understanding extreme clinical responders, in this proposal, we will evaluate 82 analogs of trabectedin to identify compound(s) with an improved therapeutic index that will allow the blockade of EWS-FLI1 in patients. In the process, we will establish exactly how the drug works to block EWS-FLI1 activity and what the relative contribution of the drug associated DNA damage is to this activity. Finally, we will propose a novel combination therapy with improved EWS-FLI1 suppression that focuses the drug associated DNA damage specifically on Ewing sarcoma cells. Together, these results will provide the basis for the clinical translation of a trabectedin- based therapy centered on EWS-FLI1 blockade to improve patient survival.