Project 2: Next Generation TOP1 Inhibition for the Treatment of Ovarian Cancer

摘要--项目2 DNA修复酶多聚(ADP-核糖)聚合酶1(PARP1)的抑制剂在高密度脂蛋白中具有高度的活性。 异基因重组(HR)缺陷型卵巢癌，尤其是BRCA1或BRCA2(BRCA1/2)突变的卵巢癌。 特兹。然而，即使在这种情况下，也有40%-80%的病例对PARP抑制剂(PARPI)具有耐药性，最常见的情况是 恢复心率的遗传或生化变化的结果。在卵巢癌的其他基因组亚群中， 对PARPI的耐药性甚至更为普遍。获得性PARPI最常见机制的观察 耐药性不是由于未能抑制PARP1而产生的，这增加了PARPis可能是 在这种环境中用作化学增敏剂，如果能确定合适的组合。因此， 本项目旨在通过将PARPI rucaparib与一种 第三代拓扑异构酶I(TOP1)抑制剂(TOP1I)。最近的研究表明，纳米颗粒 如PLX038，一种聚乙二醇偶联型超长作用形式的TOP1I 7-乙基-10- 羟基喜树碱(SN-38)表现出比传统TOP1更低的骨髓毒性和更好的疗效 临床前癌症模型。我们的初步研究表明，包括PLX038在内的TOP1IS缓释剂是 对七种PARPI耐药卵巢癌患者来源的异种移植(PDX)中的五种有效。此外， 使用一种独特的抗体来检测TOP1-DNA共价复合体(Top1ccs)，这些复合体是TOP1-DNA共价复合体的中间产物 TOP1i诱导的杀伤过程中，我们已经证明在PDX中Top1cc减少或检测不到 对TOP1i/PARPI联合耐药，为了解卵巢癌耐药提供了起点 接受这种治疗。总而言之，这些结果导致了这样的假设，即容易识别的HR子集- 熟练的卵巢癌在接受下一代治疗时将显示出持久的抗肿瘤效果 TOP1I单独或与PARPI结合使用。为了检验这一假设，我们现在建议：1)评估疗效 PLX038单独和与PARPI rucaparib联合使用，在一组基因组特征为高级别的队列中 卵巢浆液性癌对单药PARPis固有或获得性耐药谱的鉴定 可能受益于PLX038或其组合的卵巢癌；ii)确定 在PDX和细胞系中对TOP1i/PARPI组合的耐药性；以及iii)检查 药物稳定的TOP1-DNA共价复合体在肿瘤细胞中的形成及对卵巢癌的反应 在II期临床试验中，患者接受PLX038/鲁卡帕利联合治疗。总的来说，这些研究不仅将 深入了解影响卵巢第三代TOP1i反应的基因组和生化因素 癌症，但也决定了是否有可能在以下情况下使用PARPis作为化学增敏剂 他们不再作为单一代理活跃。如果成功，这个项目将为不断增长的 患有对PARPI耐药的卵巢癌的女性人数。

ABSTRACT – PROJECT 2 Inhibitors of the DNA repair enzyme poly(ADP-ribose) polymerase 1 (PARP1) are highly active in homol- ogous recombination (HR)-deficient ovarian cancers, especially those with BRCA1 or BRCA2 (BRCA1/2) muta- tions. Even in this setting, however, 40-80% of cases become PARP inhibitor (PARPi) resistant, most often as a result of genetic or biochemical changes that restore HR. Among other genomic subsets of ovarian cancer, PARPi resistance is even more prevalent. The observation that most common mechanisms of acquired PARPi resistance do not result from a failure to inhibit PARP1 raises the possibility that PARPis can potentially be utilized as chemosensitizing agents in this setting if suitable combinations can be identified. Accordingly, the present project seeks to enhance the efficacy of the PARPi rucaparib and extend its use by combining it with a 3rd generation topoisomerase I (TOP1) inhibitor (TOP1i). Recent studies have shown that nanoparticle formulations such as PLX038, a polyethylene glycol-conjugated ultra-long acting form of the TOP1i 7-ethyl-10- hydroxycamptothecin (SN-38), exhibit less marrow toxicity and greater efficacy than conventional TOP1is in preclinical cancer models. Our preliminary studies show that sustained release TOP1is, including PLX038, are active against five of seven PARPi-resistant ovarian cancer patient-derived xenografts (PDXs) tested. Moreover, using a unique antibody that detects TOP1-DNA covalent complexes (TOP1ccs), which are intermediates in the TOP1i-induced killing process, we have shown that TOP1ccs are diminished or undetectable in PDXs that are resistant to the TOP1i/PARPi combination, providing a starting point for understanding ovarian cancer resistance to this treatment. Collectively, these results lead to the hypothesis that a readily identifiable subset of HR- proficient ovarian cancers will exhibit sustained antitumor effects when treated with a next generation TOP1i alone or in combination with a PARPi. To test this hypothesis, we now propose to i) assess the efficacy of PLX038, alone and in combination with the PARPi rucaparib, in a cohort of genomically profiled high grade serous ovarian cancer PDXs with intrinsic or acquired resistance to single agent PARPis to identify the spectrum of ovarian cancers that could potentially benefit from PLX038 or the combination; ii) identify mechanisms of resistance to the TOP1i/PARPi combination in PDXs and cell lines; and iii) examine the association between the formation of drug-stabilized TOP1-DNA covalent complexes in tumor cells and the response of ovarian cancer patients to the PLX038/rucaparib combination in a phase II clinical trial. Collectively, these studies will not only provide insight into the genomic and biochemical factors that affect response to a 3rd generation TOP1i in ovarian cancer, but also determine whether it is possible to use PARPis as chemosensitizing agents in settings where they are no longer active as single agents. If successful, this project will point to a new therapy for the growing number of women with PARPi-resistant ovarian cancer.