Project 2: Combination PARPi-BETi to Overcome PARPi Resistance

摘要--项目2 PARP抑制剂已经成为上皮性卵巢癌(OvCa)的标准治疗选择。 大约一半的OvCa患者在同源重组中存在失活的基因改变 (HR)途径，导致合成致死与PARP抑制(PARPI)。PARPI具有良好的活性 在HR缺乏的OvCa中。尽管与HR缺乏的OvCa相比，PARPis的效果不那么好，但它也 在精通人力资源的OvCA中表现活跃。不幸的是，PARPI的活性受到以下因素的限制 PARPI抵抗。因此，迫切需要确定逆转PARPI耐药性的潜在策略 在Ovca。我们的初步研究表明，溴域体外抑制剂对BRD4活性的抑制 (Beti)是一种有吸引力的逆转PARPI耐药性的方法。值得注意的是，BRD4基因组座位19p13.12是 常见于高级别浆液性卵巢癌(~20%)。事实上，BRD4的扩增/过度表达与 这些患者的预后很差。 我们和其他人已经证明，Betis在抑制HR途径和损害G2/M方面发挥着重要作用 Checkpoint，它逆转了HR通路恢复引起的对PARPI的抵抗。因此，我们的 中心假设是，使用临床适用的BET抑制剂来靶向BRD4活性就足够了 以克服复发性Ovca对PARPI的耐药性。我们还假设以BRD4为目标 将通过同时下调HR活性，特别是BRCA1、RAD51和PARPI使肿瘤对PARPI敏感 TOPBP1表达，并通过抑制WEE1活性损害细胞周期的G2/M期，导致 DNA损伤积累和有丝分裂灾难。因此，本研究的目的是 联合应用PARPI和Beti治疗复发PARPI耐药的安全性和有效性 对铂敏感的卵母细胞瘤。我们还计划评估PARPI-Beti组合对功能性HR的影响 与基线相比，活动度和减少的百分比与治疗的客观反应相关。此外， 我们计划在患者衍生模型中研究这些发现的机制基础，这些模型是从 患者参加了试验。为了实现这一目标，我们提出了以下具体目标：SA1。要确定 PARPI联合倍他乐定治疗复发性PARPI耐药OvCA的安全性和有效性 IB临床试验。SA2.探讨联合用药对心率和DNA损伤的影响 使用组织和循环肿瘤DNA样本的反应(DDR)途径以及G2-M细胞周期检查点 在基线、治疗和进展时都是如此。SA3：研究反应的机制和 临床前模型对联合方案的抵抗力。潜在的影响是巨大的，因为 Ovca中迫切需要克服对PARPI的耐药性。这个项目研究了一种新的治疗方法 贝蒂将PARPI与表观遗传疗法相结合的方向。PARPI抵抗是一个重大挑战，因为 PARPI现已在一线和经常性环境中获得批准。此外，这项研究将调查预测性 生物标志物，这将有助于识别从该方案中受益的患者。这项研究的成功实施 将提供一个理论基础，将这种疗法推进到科学合理的试验中，重点是改善 在有限的治疗选择下，这种最致命的癌症的结果。

ABSTRACT – PROJECT 2 PARP inhibitors have emerged as an established standard of care option in epithelial ovarian cancer (OvCa). Approximately half of OvCa patients harbor inactivating genetic alterations in the homologous recombination (HR) pathway, which results in synthetic lethality with PARP inhibition (PARPi). PARPi have promising activity in HR-deficient OvCa. Even though less effective compared to HR-deficient OvCa, PARPis have also been shown to be active in HR-proficient OvCa. Unfortunately, the activity of PARPi is limited by the emergence of PARPi resistance. Therefore, there is an urgent need to identify potential strategies to reverse PARPi resistance in OvCa. Our preliminary studies suggest that inhibition of BRD4 activity by bromodomain extraterminal inhibitors (BETi) is an attractive approach to reverse PARPi resistance. Notably, the BRD4 genomic locus 19p13.12 is often amplified in high-grade serous OvCa (~20%). Indeed, BRD4 amplification/overexpression correlates with a poor prognosis in these patients. We and others have shown that BETis play a major role in suppressing the HR pathway and impairing the G2/M checkpoint, which reverses resistance to PARPi caused by restoration of the HR pathway. Therefore, our central hypothesis is that targeting BRD4 activity using clinically applicable BET inhibitor is sufficient to overcome resistance to PARPi developed in recurrent OvCa. We also hypothesize that targeting BRD4 will sensitize tumor to PARPi by simultaneously downregulating HR activity, specifically BRCA1, RAD51 and TOPBP1 expression, and impairing the G2/M phase of the cell cycle by suppressing WEE1 activity, leading to DNA damage accumulation and mitotic catastrophe. Accordingly, the objective of the present study is to evaluate the safety and efficacy of a combination of PARPi and BETi in recurrent PARPi-resistant platinum-sensitive OvCa. We also plan to assess the impact of PARPi-BETi combination on functional HR activity and percent reduction compared to baseline and correlate with objective response to therapy. Further, we plan to investigate the mechanistic basis of these findings in patient-derived models obtained from the patients enrolled in the trial. To achieve that, we propose the following specific aims (SA): SA1. To determine the safety and efficacy of PARPi combined with BETi in patients with recurrent PARPi-resistant OvCa in a phase Ib clinical trial. SA2. To investigate the impact of the combined regimen on modulating HR and DNA damage response (DDR) pathways as well as G2-M cell cycle checkpoint using tissue and circulating tumor DNA samples both at baseline, on treatment and at time of progression. SA3: To investigate the mechanisms of response and resistance to the combination regimen in preclinical models. The potential impact is significant as there is an urgent need to overcome resistance to PARPi in OvCa. This project investigates a novel new therapeutic direction combining PARPi with epigenetic therapy by BETi. PARPi resistance is a major challenge given that PARPi are now approved in first line and recurrent settings. Further, this study will investigate predictive biomarkers, which will help identify patients who benefit from this regimen. Successful execution of this study will provide a rationale to advance this regimen into scientifically rationalized trials focused on improving the outcome of this most lethal cancer with limited treatment options.