Project 2: Combination PARPi-BETi to Overcome PARPi Resistance

摘要-项目2 PARP抑制剂已成为上皮性卵巢癌（OvCa）的既定标准治疗选择。 大约一半的OvCa患者在同源重组中存在失活遗传改变， (HR)途径，其导致具有PARP抑制的合成致死性（PARPi）。PARPi具有良好的活性 在缺乏HR的OvCa中。尽管与HR缺乏的OvCa相比效果较差，但PARPis也被认为是有效的。 显示在HR熟练的OvCa中是活跃的。不幸的是，PARPi的活动受到了 PARPi抗性。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，通过布罗莫结构域末端外抑制剂抑制BRD 4活性， （BETi）是逆转PARPi抗性的有吸引力的方法。值得注意的是，BRD 4基因组位点19p13.12是 常在高级别浆液性OvCa中扩增（~20%）。事实上，BRD 4扩增/过表达与以下相关： 这些患者的预后很差。 我们和其他人已经表明，BETis在抑制HR途径和损害G2/M中起主要作用。 检查点，其逆转由HR途径的恢复引起的对PARPi的抗性。所以我们的 中心假设是使用临床适用的BET抑制剂靶向BRD 4活性是足够的 以克服复发性OvCa中产生的对PARPi的抗性。我们还假设，针对BRD 4 通过同时下调HR活性，特别是BRCA 1、RAD 51和 TOPBP 1表达，并通过抑制WEE 1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 评估PARPi和BETi联合治疗复发性PARPi耐药患者的安全性和有效性 铂敏感OvCa。我们还计划评估PARPi-BETi组合对功能性HR的影响 与基线相比的活性和百分比降低，并与对治疗的客观反应相关。此外，本发明还 我们计划研究这些发现的机制基础，这些发现来自患者的模型， 参加试验的患者。为了实现这一目标，我们提出了以下具体目标（SA）：SA 1。以确定 PARPi联合BETi治疗复发性PARPi耐药OvCa患者的安全性和有效性 Ib临床试验。SA 2.研究联合方案对调节HR和DNA损伤的影响 使用组织和循环肿瘤DNA样本，研究DDR反应（DDR）途径以及G2-M细胞周期检查点 在基线、治疗期间和进展时。SA 3：研究反应机制， 在临床前模型中对联合方案的耐药性。潜在的影响是巨大的，因为有一个 迫切需要克服OvCa对PARPi的耐药性。该项目研究了一种新的治疗方法， 将PARPi与BETi的表观遗传疗法相结合。PARPi抗性是一个重大挑战， PARPi现在已被批准用于一线和经常性环境。此外，这项研究将调查预测 生物标志物，这将有助于确定谁受益于这种方案的患者。成功执行本研究 将提供一个理论基础，以推动这一方案成为科学合理的试验，重点是改善 这是一种最致命的癌症，治疗选择有限。

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.