BRCA Wild-type Ovarian Cancer Research Articles

First-in-Human Study of the Ataxia Telangiectasia and Rad3-Related (ATR) Inhibitor Tuvusertib (M1774) as Monotherapy in Patients with Solid Tumors.

Tuvusertib (M1774) is a potent, selective, orally administered ataxia telangiectasia and Rad3-related (ATR) protein kinase inhibitor. This first-in-human study (NCT04170153) evaluated safety, tolerability, maximum tolerated dose (MTD), recommended dose for expansion (RDE), pharmacokinetics (PK), pharmacodynamics (PD), and preliminary efficacy of tuvusertib monotherapy. Ascending tuvusertib doses were evaluated in 55 patients with metastatic or locally advanced unresectable solid tumors. A safety monitoring committee determined dose escalation based on PK, PD, and safety data guided by a Bayesian 2-parameter logistic regression model. Molecular responses (MR) were assessed in circulating tumor DNA samples. Most common grade ≥3 treatment-emergent adverse events were anemia (36%), neutropenia, and lymphopenia (both 7%). Eleven patients experienced dose-limiting toxicities, most commonly grade 2 (n = 2) or 3 (n = 8) anemia. No persistent effects on blood immune cell populations were observed. The RDE was 180 mg tuvusertib QD (once daily), 2 weeks on/1 week off treatment, which was better tolerated than the MTD (180 mg QD continuously). Tuvusertib median time to peak plasma concentration ranged from 0.5 to 3.5 hours and mean elimination half-life from 1.2 to 5.6 hours. Exposure-related PD analysis suggested maximum target engagement at ≥130 mg tuvusertib QD. Tuvusertib induced frequent MRs in the predicted efficacious dose range; MRs were enriched in patients with radiological disease stabilization, and complete MRs were detected for mutations in ARID1A, ATRX, and DAXX. One patient with platinum- and PARP inhibitor-resistant BRCA wild-type ovarian cancer achieved an unconfirmed RECIST v1.1 partial response. Tuvusertib demonstrated manageable safety and exposure-related target engagement. Further clinical evaluation of tuvusertib is ongoing.

316P First evidence of olaparib maintenance therapy in patients with newly diagnosed BRCA wild-type ovarian cancer: A real-world multicenter study

316P First evidence of olaparib maintenance therapy in patients with newly diagnosed BRCA wild-type ovarian cancer: A real-world multicenter study

Constitutional BRCA1 and RAD51C methylation associated with corresponding gene methylation in BRCA wildtype ovarian cancer (156)

Constitutional BRCA1 and RAD51C methylation associated with corresponding gene methylation in BRCA wildtype ovarian cancer (156)

Apatinib combined with olaparib induces ferroptosis via a p53-dependent manner in ovarian cancer.

PARP inhibitors combined with antiangiogenic drugs have been reported to improve outcomes in BRCA wild-type ovarian cancer patients, the mechanism of the combination is unclear. In this study, we explored the mechanism of apatinib combined with olaparib in the treatment of ovarian cancer. In this study, human ovarian cancer cell lines A2780 and OVCAR3 were used as experimental objects, and the expression of ferroptosis-related protein GPX4 after treatment with apatinib and olaparib was detected by Western blot. The SuperPred database was used to predict the target of the combined action of apatinib and olaparib, and the predicted results were verified by Western blot experiment to explore the mechanism of ferroptosis induced by apatinib and olaparib. Apatinib combined with olaparib-induced ferroptosis in p53 wild-type cells, and p53 mutant cells developed drug resistance. The p53 activator RITA sensitized drug-resistant cells to ferroptosis induced by apatinib combined with olaparib. Apatinib combined with olaparib-induced ferroptosis via a p53-dependent manner in ovarian cancer. Further studies showed that apatinib combined with olaparib-induced ferroptosis by inhibiting the expression of Nrf2 and autophagy, thereby inhibiting the expression of GPX4. The Nrf2 activator RTA408 and the autophagy activator rapamycin rescued the combination drug-induced ferroptosis. This discovery revealed the specific mechanism of ferroptosis induced by apatinib combined with olaparib in p53 wild-type ovarian cancer cells and provided a theoretical basis for the clinical combined use of apatinib and olaparib in p53 wild-type ovarian cancer patients.

Abstract 5977: Evaluation of the potential combination regimens for q901, a clinical stage selective cdk7 inhibitor, as a DNA damage repair inhibitor

Abstract Background; Q901 is an extremely selective CDK7 inhibitor with potent single agent activity in the multiple in vivo tumor models including small cell lung cancer, cholangiocarcinoma, colon cancer, pancreatic cancer, hormone receptor positive breast cancer, castrate-resistant prostate cancer, and ovarian cancer. Q901 is currently in Phase 1/2 clinical trial for patients with selected advanced solid tumors (ClinicalTrials.gov: NCT05394103). In the preclinical models, Q901 treatment induces DNA damage response (DDR) impairment markers, particularly ones involved in the double-strand break repair mechanisms. This opens up broad range of possibilities for new combination regimen that could benefit from the accumulated DNA damages caused by Q901 treatment. Methods: Various combinations have been tested to evaluate potential clinical regimens in multiple solid tumor models. Two different BRCA wild-type ovarian cancer A2780 and OVCAR3 models, an estrogen receptor positive MCF7 breast cancer model, or a syngeneic RENCA mouse renal cancer model was tested with Q901 in combination with poly ADP-ribose polymerase (PARP) inhibitor, selective estrogen receptor degrader (SERD), an estrogen receptor (ER) PROTAC degrader, or an anti-PD-1 antibody, respectively. Results: In the A2780 model, the PARPi alone group showed 15% TGI (tumor growth inhibition), but significant tumor regression (104% TGI) was observed in the Q901 and PARPi combination. In the OVCAR3 model, the Q901 and PARPi combination group showed 105% TGI, whereas the PARPi alone group showed 38% TGI. In the MCF7 model, SERD alone showed 64% TGI and Q901 combination with SERD showed 94% TGI. Remarkable tumor regression (111% TGI) was observed in the MCF7 model combining ER PROTAC and Q901, whereas ER PROTAC alone group showed 55% TGI. In the RENCA model, the anti-PD-1 antibody alone group showed 13.2% TGI and the combination of Q901 and anti-PD-1 antibody showed 66% TGI. In summary, these preclinical model studies demonstrated significant additive/synergistic effects of the Q901 combination on tumor growth inhibition. Conclusion: The non-clinical data demonstrate that Q901 not only has a potential as a single agent,but can also be used in combination with other therapeutic strategies to develop next-generation cancer therapeutics to potentially address unmet medical needs. Citation Format: Donghoon Yu, Yeejin Jeon, YoonJi Lee, Seung-Joo Lee, Jaeseung Kim, Hyerim Jung, Tae-Kyung Kim, Kiyean Nam. Evaluation of the potential combination regimens for q901, a clinical stage selective cdk7 inhibitor, as a DNA damage repair inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5977.

Anticancer Effect of Active Component of Astragalus Membranaceus Combined with Olaparib on Ovarian Cancer Predicted by Network-Based Pharmacology.

In China, a traditional Chinese medicine formulation called astragalus membranaceus (AM) has been utilised for more than 20 years to treat tumors with extraordinary effectiveness. The fundamental mechanisms, nevertheless, are still not well understood. The aim of this study is identifying its possible therapeutic targets and to evaluate the effects of AM in combination with a PARP inhibitor (olaparib) in the treatment of BRCA wild-type ovarian cancer. Significant genes were collected from Therapeutic Target Database and Database of Gene-Disease Associations. The components of AM were analyzed using the Traditional Chinese Medicine System Pharmacology (TCMSP) database to screen the active ingredients of AM based on their oral bioavailability and drug similarity index. In order to find intersection targets, Venn diagrams and STRING website diagrams were employed. STRING was also used to create a protein-protein interaction network. In order to create the ingredient-target network, Cytoscape 3.8.0 was used. DAVID database was utilized to carry out enrichment and pathway analyses. The binding ability of the active compounds of AM to the core targets of AM-OC was verified with molecular docking using AutoDock software. Experimental validations, including cell scratch, cell transwell, cloning experiment, were conducted to verify the effects of AM on OC cells. A total of 14 active ingredients of AM and 28 AM-OC-related targets were screened by network pharmacology analysis. The ten most significant Gene Ontology (GO) biological function analyses, as well as the 20 foremost Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathways were selected. Moreover, molecular docking results showed that bioactive compound (quercetin) demonstrated a good binding ability with tumor protein p53 (TP53), MYC, vascular endothelial growth factor A (VEGFA), phosphatase and tensin homolog (PTEN), AKT serine/threonine kinase 1 (AKT1) and cyclin D1 (CCND1) oncogenes. According to experimental methods, in vitro OC cell proliferation and migration appeared to be inhibited by quercetin, which also increased apoptosis. In addition, the combination with olaparib further enhanced the effect of quercetin on OC. Based on network pharmacology, molecular docking, and experimental validation, the combination of PARP inhibitor and quercetin enhanced the anti-proliferative activity in BRCA wild-type ovarian cancer cells, which supplies the theoretical groundwork for additional pharmacological investigation.

Ki67 as a Predictor of Response to PARP Inhibitors in Platinum Sensitive BRCA Wild Type Ovarian Cancer: The MITO 37 Retrospective Study.

There is compelling need for novel biomarkers to predict response to PARP inhibitors (PARPi) in BRCA wild-type (WT) ovarian cancer (OC). MITO 37 is a multicenter retrospective study aiming at correlating Ki67 expression at diagnosis with a clinical outcome following platinum treatment and PARPi maintenance. Clinical data were collected from high grade serous or endometroid BRCAWT OC treated with niraparib or rucaparib maintenance between 2010-2021 in 15 centers. Ki67 expression was assessed locally by certified pathologists on formalin-fixed paraffin embedded (FFPE) tissues. Median Ki67 was used as a cut-off. A total of 136 patients were eligible and included in the analysis. Median Ki67 was 45.7% (range 1.0-99.9). The best response to platinum according to median Ki67 was 26.5% vs. 39.7% complete response (CR), 69.1% vs. 58.8% partial response (PR), 4.4% vs. 1.5% stable disease (SD). The best response to PARPi according to median Ki67 was 19.1% vs. 36.8% CR, 26.5% vs. 26.5% PR, 26.5 vs. 25% SD, 27.9% vs. 16.2% progressive disease (PD). No statistically significant differences in progression free survival (PFS) and overall survival (OS) were identified between low and high Ki67. PFS and OS are in line with registration trials. Ki67 at diagnosis did not discriminate responders to PARPi.

186P Degradation of BRCA2 expression by hyperthermia sensitizes HRD-negative (BRCA2 wild-type) ovarian cancer cells to niraparib

Poly (ADP-ribose) polymerase (PARP) inhibitors have significantly improved survival for advanced ovarian cancer patients as maintenance therapy and have become an important component of standard treatment for ovarian cancer. Ovarian cancer cells with BRCA mutations are particularly sensitive to PARP inhibitors, but how to improve the sensitivity of BRCA wild-type ovarian cancer to PARP inhibitors has become a focus of research. We identified if down-regulation of BRCA2 expression by hyperthermia (HT) sensitizes HRD-negative ovarian cancer to Niraparib.

The Influence of PARP, ATR, CHK1 Inhibitors on Premature Mitotic Entry and Genomic Instability in High-Grade Serous BRCAMUT and BRCAWT Ovarian Cancer Cells.

Olaparib is a poly (ADP-ribose) polymerase inhibitor (PARPi) that inhibits PARP1/2, leading to replication-induced DNA damage that requires homologous recombination repair. Olaparib is often insufficient to treat BRCA-mutated (BRCAMUT) and BRCA wild-type (BRCAWT) high-grade serous ovarian carcinomas (HGSOCs). We examined the short-term (up to 48 h) efficacy of PARPi treatment on a DNA damage response pathway mediated by ATR and CHK1 kinases in BRCAMUT (PEO-1) and BRCAWT (SKOV-3 and OV-90) cells. The combination of ATRi/CHK1i with PARPi was not more cytotoxic than ATR and CHK1 monotherapy. The combination of olaparib with inhibitors of the ATR/CHK1 pathway generated chromosomal abnormalities, independent on BRCAMUT status of cells and formed of micronuclei (MN). However, the beneficial effect of the PARPi:ATRi combination on MN was seen only in the PEO1 BRCAMUT line. Monotherapy with ATR/CHK1 inhibitors reduced BrdU incorporation due to a slower rate of DNA synthesis, which resulted from elevated levels of replication stress, while simultaneous blockade of PARP and ATR caused beneficial effects only in OV-90 cells. Inhibition of ATR/CHK1 increased the formation of double-strand breaks as measured by increased γH2AX expression at collapsed replication forks, resulting in increased levels of apoptosis. Our findings indicate that ATR and CHK1 inhibitors provoke premature mitotic entry, leading to genomic instability and ultimately cell death.

VEGF-C serum level is associated with response to bevacizumab maintenance therapy in primary ovarian cancer patients.

ObjectiveAt present, maintenance therapy with the antiangiogenic agent bevacizumab or with PARP-inhibitors represent two options for BRCA-wildtype ovarian cancer patients, after platinum-based first line chemotherapy. The identification of molecular markers to predict patient response to different maintenance therapies remains a major challenge. In the present study we analyzed the predictive potential of vascular endothelial growth factor C (VEGF-C) to identify ovarian cancer patients that might benefit from an antiangiogenic therapy.Methods101 patients with primary epithelial ovarian cancer were analyzed for serum levels of VEGF-A,–C and CA-125 by ELISA. Serum levels were compared between patients with low pT-stage (pT1a-pT2c n = 11), healthy individuals (n = 27) and patients with higher pT-stage (> = pT3 n = 90). Adjusted ROC curves and an adjusted logistic regression model were carried out to evaluate the potential impact of VEGF-A and -C, as well as CA-125 serum level concentration on bevacizumab-therapy response, under consideration of covariates such as FIGO, pM, pN and residual tumor after surgery.ResultsA patient which has in comparison twice the VEGF-C concentration in serum, has a significant increased chance of response to bevacizumab by a factor of 2.79. Further, only VEGF-C serum levels were significantly higher in the group of patients with lower pT-stage compared to healthy individuals, whereas VEGF-A or CA-125 serum levels could not discriminate between healthy individuals and patients with ovarian cancer at low pT-stages.ConclusionVEGF-C serum level might serve as as a biomarker to evaluate treatment response under bevacizumab.

Abstract 2432: Somatic mutations in the STAT3 activation pathway are associated with improved survival in gynecologic malignancies and provide a molecular rationale for therapeutic targeting

Abstract Background: Signal transducer and activator of transcription 3 (STAT3) activation promotes tumor cell survival, immune evasion, metastasis, and drug resistance in PARP inhibitors and platinum-based chemotherapy. Objective: Based on our in-vitro findings of the tumoricidal potential of STAT3 inhibition in BRCAwild-type and PARP inhibitor-resistant tumor cells, we sought to evaluate whether ovarian and uterine cancer patients with somatic mutations in the STAT3 activation pathway had improved overall survival (OS) compared to those with intact STAT3 activation pathway-related genes. Method: We induced Olaparib resistance in BRCAwild-type ovarian cancer cell lines (OVCAR8 and A2780) and treated both parental and PARP inhibitor-resistant cell lines with various STAT3 inhibitors. We then attempted to establish clinical correlations of our in-vitro studies and queried the Cancer Genome Atlas (TCGA) Pan-Cancer Atlas for uterine and ovarian cancers. OS in patients with somatic mutations in the STAT3 gene and/or associated STAT3 activation genes (IL6ST, GNAS, JAK1, JAK2) was compared to OS in patients with intact STAT3 pathway-related genes. Kaplan-Meier survival curves were compared using the log-rank test. Results: In-vitro, STAT3 inhibition demonstrated potent, tumoricidal propensity in all cell lines (EC50: 0.34uM-0.46uM) including A2780parental, A2780parpi-resistant, OVCAR8parental, and OVCAR8parpi-resistant. Clinically, 1,154 total patients were identified in TCGA, including 571 high-grade serous ovarian carcinoma, 397 uterine endometrioid adenocarcinomas, 109 uterine serous carcinoma/uterine papillary serous carcinomas, 56 uterine carcinosarcomas/uterine malignant mixed Mullerian tumors, and 21 uterine mixed endometrial carcinomas. When pooling all uterine and ovarian cancer patients, median survival (MS) was 52 months (0-185) in patients with intact STAT3 (n=1,007) compared to not reached (NR, 0-225) in the STAT3 mutated group (n=147) with a Hazard Ratio (HR) of 0.25 and Confidence Interval (CI) 0.20-0.32 (p<0.001). In ovarian cancer patients, MS was 45 months (0-180) in patients with intact STAT3 (n=551) compared to 95 months (0-145) in the STAT3 mutated group (n=20) with a HR of 0.48 and CI 0.29-0.80 (p=0.038). In uterine cancer patients, MS was 112 months (0-185) in patients with intact STAT3 (n=456) compared to NR (0-225) in the STAT3 mutated group (n=127) with a HR of 0.40 and CI 0.25-0.64 (p=0.003). Conclusion: Pharmacologic and genetic (siRNA) inhibition of the STAT3 activation pathway killed PARP inhibitor-resistant ovarian cancer cells in-vitro. Clinically, somatic mutations in the STAT3 activation pathway were associated with improved OS in both ovarian and uterine cancer. These findings provide a rationale for the therapeutic targeting of this pathway in gynecologic malignancies. Citation Format: Adrian Kohut, Antons Martincuks, Thanh Dellinger, Hua Yu, Lorna Rodriguez-Rodriguez. Somatic mutations in the STAT3 activation pathway are associated with improved survival in gynecologic malignancies and provide a molecular rationale for therapeutic targeting [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2432.

Enhanced Efficacy of Combined Therapy with Checkpoint Kinase 1 Inhibitor and Rucaparib via Regulation of Rad51 Expression in BRCA Wild-Type Epithelial Ovarian Cancer Cells.

PurposeThis study aimed to evaluate anticancer effects of combination treatment with poly(ADP-ribose) polymerase (PARP) and checkpoint kinase 1 (Chk1) inhibitors in BRCA wild-type ovarian cancer. PARP inhibitors can function as DNA-damaging agents in BRCA wild-type cancer, even if clinical activity is limited. Most epithelial ovarian cancers are characterized by a TP53 mutation causing dysfunction at the G1/S checkpoint, which makes tumor cells highly dependent on Chk1-mediated G/M phase cell-cycle arrest for DNA repair.Materials and MethodsWe investigated the anticancer effects of combination treatment with prexasertib (LY2606368), a selective ATP competitive small molecule inhibitor of Chk1 and Chk2, and rucaparib, a PARP inhibitor, in BRCA wild-type ovarian cancer cell lines (OVCAR3 and SKOV3).ResultsWe found that combined treatment significantly decreased cell viability in all cell lines and induced greater DNA damage and apoptosis than in the control and/or using monotherapies. Moreover, we found that prexasertib significantly inhibited homologous recombination–mediated DNA repair and thus showed a marked anticancer effect in combination treatment with rucaparib. The anticancer mechanism of prexasertib and rucaparib was considered to be caused by an impaired G2/M checkpoint due to prexasertib treatment, which forced mitotic catastrophe in the presence of rucaparib.ConclusionOur results suggest a novel effective therapeutic strategy for BRCA wild-type epithelial ovarian cancer using a combination of Chk1 and PARP inhibitors.

Abstract 1379: Entinostat induces PARPi sensitivity across multiple ovarian cancer models

Abstract Introduction: Ovarian cancer is a rare, but fatal disease and a leading cause of gynecologic cancer death, in the United States. Poly ADP ribose polymerase inhibitors (PARPi) are promising drugs, most effective in patients with tumors deficient in homologous recombination (HR) genes, mainly BRCA1/2. Our group has published that histone deacetylase inhibitors (HDACi) sensitized HR proficient BRCA wild-type ovarian cancer cells to PARPi, however the mechanism still remains elusive and the efficacy needed to be tested across multiple models. We recently tested Entinostat with and without Olaparib in three different ovarian cancer models, including human/mouse established cell lines, PDX derived primary cell lines and immune-competent/immune-compromised xenograft as well as PDX-derived preclinical mouse models. Objective: To delineate the efficacy of Entinostat to sensitize ovarian tumors to Olaparib across multiple models and determine the underlying mechanism. Methods: HR proficient BRCA wild-type ID8/SKOV3 and PDX derived primary cell lines were treated with Entinostat and Olaparib, alone or in combination and analyzed for cell proliferation. DNA damage was studied using Comet assay. Expression of cell proliferation, DNA damage and repair protein were studied using Western blot analysis and immunofluorescence. Further, ID8-treated immune-competent mouse models, SKOV3-treated immune-compromised mouse model and HGSOC patient derived PDX mouse model generated in our lab were treated with vehicle, Entinostat, Olaparib, or the combination. The mice were monitored for toxicity and body weight measured twice weekly, till tissue harvest or survival. Results: Cell proliferation was significantly decreased (p&lt0.05) in Entinostat-Olaparib combination treated groups in all cell lines tested. Comet assay showed significantly longer comet tail length in combination treated cells compared to control (p&lt0.05). Western blot and Immunofluorescence showed that combination treatment significantly decreased BRCA1, PCNA, RAD51 and increased cleaved PARP, ΓH2AX (p&lt0.05). Further, SKOV3- xenograft mouse model showed decreased tumor burden ((p&lt0.07), ID8-xenograft mouse tumors showed decreased Ki67 (p&lt0.05) and HGSOC derived PDX model showed longer survival when treated with Entinostat-Olaparib combination therapy. Conclusion: Entinostat in combination with Olaparib decreased cell proliferation, increased DNA damage, induced HR deficiency in vitro, reduced tumor burden, decreased Ki67 in xenograft mouse model, and improved survival of HGSOC derived PDX mice, thereby potentially sensitizing homologous recombination proficient ovarian cancer to PARPi across multiple models. Citation Format: Vijayalaxmi G. Gupta, Shariska Petersen, Jeff Hirst, Katherine Roby, Harsh Pathak, Meghan Kusch, Andrew Wilson, Andrew Godwin, Dineo Khabele. Entinostat induces PARPi sensitivity across multiple ovarian cancer models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1379.

Resistance to the CHK1 inhibitor prexasertib involves functionally distinct CHK1 activities in BRCA wild-type ovarian cancer

High grade serous ovarian cancer (HGSOC) is a fatal gynecologic malignancy in the U.S. with limited treatment options. New therapeutic strategies include targeting of the cell cycle checkpoints, e.g., ATR and CHK1. We recently reported a promising clinical activity of the CHK1 inhibitor (CHK1i) prexasertib monotherapy in BRCA wild-type (BRCAwt) HGSOC patients. In this study, biopsies of treated patients and cell line models were used to investigate possible mechanisms of resistance to CHK1i. We report that BRCAwt HGSOC develops resistance to prexasertib monotherapy via a prolonged G2 delay induced by lower CDK1/CyclinB1 activity, thus preventing cells from mitotic catastrophe and cell death. On the other hand, we noted CHK1’s regulation on RAD51-mediated homologous recombination (HR) repair was not altered in CHK1i-resistant cells. Therefore, CHK1i sensitizes CHK1i-resistant cells to DNA damaging agents such as gemcitabine or hydroxyurea by inhibition of HR. In summary, our results demonstrate new mechanistic insights of functionally distinct CHK1 activities and highlight a potential combination treatment approach to overcome CHK1i resistance in BRCAwt HGSOC.

Characterization of patients (pts) with long-term responses to rucaparib in recurrent ovarian cancer (OC).

6015 Background: Pts who derive durable benefit from PARP inhibitor treatment may provide insights into improving outcomes. Here we describe long-term responders from Study 10 (NCT01482715) and ARIEL2 (NCT01891344), studies of the PARP inhibitor rucaparib for the treatment of high-grade recurrent OC. Methods: This analysis included pts enrolled in Study 10 (Part 2A: BRCA1 or BRCA2 [ BRCA]-mutant OC, platinum sensitive, 2–4 prior chemotherapies; Part 2B: any platinum status, 3–4 prior chemotherapies) and ARIEL2 (Part 1: BRCA-mutant or wild-type OC, platinum sensitive; Part 2: any platinum status, 3–4 prior chemotherapies). Final results from Study 10 (n = 54) and ARIEL2 (n = 491) were pooled. Long-term responders were defined as pts with duration of response (DOR) > 1 y, and short-term responders as pts with DOR ≤ 20 weeks; responses were evaluated using RECIST. Targeted next-generation sequencing was used to detect deleterious mutations and loss of heterozygosity (LOH) in tumors. BRCA1 methylation was quantified by digital droplet PCR. Results: Overall, 25% (138/545) of enrolled pts were responders. Of these, 29% (40/138) had long-term responses, including 16/138 (12%) with DOR > 2 y; 21% (29/138) were short-term responders. Both groups received a median of 3 prior anticancer therapies. Among patients with BRCA mutations, BRCA homozygous deletion or rearrangement was detected in 15% (4/27) of long-term responders vs 0% (0/15) of short-term responders. In an expanded analysis of the 95 pts with BRCA mutations and confirmed response, pts with BRCA homozygous deletion or rearrangement had significantly longer DOR than pts with other mutation types (median 3.5 vs 0.6 y; HR = 0.30; p = 0.024). There was no apparent difference in BRCA gene or mutation location for long- vs short-term responders. Ten of the 13 long-term responders with BRCA wild-type OC had high genome-wide LOH (≥16% LOH), a genomic scar indicative of homologous recombination deficiency, including OC associated with BRCA1 hypermethylation (n = 2) and RAD51C/D mutations (n = 2). Conclusions: Long-term responders to rucaparib include OC with BRCA mutation, particularly homozygous deletion or rearrangements, which would not be susceptible to somatic reversion mutations, as well as BRCA1 hypermethylation, and RAD51C/D mutations. Clinical trial information: NCT01482715; NCT01891344.

Defining and targeting wild-type BRCA high-grade serous ovarian cancer: DNA repair and cell cycle checkpoints

ABSTRACTIntroduction: Molecular analyzes including molecular descriptor/phenotype interactions have led to better characterization of epithelial ovarian cancer patients, including a definition of a BRCA wild-type (BRCAwt) phenotype. Understanding how and when to use agents targeted against dependent BRCAwt pathways or other molecular events at disease progression is an important translational and therapeutic direction in ovarian cancer research.Areas covered: In this overview, we provide definitions and descriptions of a BRCAwt genotype and phenotype. We discuss novel investigational drugs that hold promise for the treatment of BRCAwt ovarian cancer, including inhibitors of poly(ADP-ribose) polymerase, ribonucleotide reductase, DNA protein kinase-catalytic subunit, ataxia-telangiectasia-mutated kinase (ATM), ataxia-telangiectasia mutated and Rad3-related kinase (ATR), CHK 1/2, cyclin kinases, glutaminase-1, WEE1 kinase, as well as tumor microenvironment and angiogenesis inhibitors. This article explores the known and the emerging areas of clinical research on patients with BRCAwt ovarian cancer.Expert opinion: Discovery of molecular changes tied to annotated disease information, along with an expanding array of pathway targets and targeted therapeutic agents, creates optimism and opportunity for women with ovarian cancer. Using precision oncology approaches, clinical researchers are, and will be, poised to select more effective treatments for ovarian cancer patients.

Abstract 3501: Entinostat enhances the efficacy of olaparib in preclinical models of ovarian cancer

Abstract Introduction: Ovarian cancer is a rare but often fatal disease and a leading cause of gynecologic cancer death, in the United States. Poly ADP ribose polymerase inhibitors (PARPi) are promising new drugs that are most effective in patients with tumors with altered homologous recombination (HR) DNA repair genes, particularly BRCA1/2. To expand their clinical utility, PARPi are being tested in combination with other drugs. Our group has published that histone deacetylase inhibitors (HDACi) sensitize HR proficient BRCA wild-type ovarian cancer cells to PARPi. We have developed an investigator-initiated phase 1/2 clinical trial of the PARPi olaparib combined with the HDACi entinostat in patients with recurrent, HR proficient/BRCA wild-type ovarian cancer. Objective: To test the effects of a novel combination of olaparib and entinostat in preclinical models of BRCA wild-type ovarian cancer. Methods: HR proficient BRCA wild-type SKOV3 and ID8 ovarian cells were treated with Entinostat followed by Olaparib alone or the combination of Entinostat and Olaparib. Treated and control cells were analyzed for cell proliferation by sulforhodamine B assays, clonogenicity, and DNA damage by Comet assays. SKOV-3-luciferase cells were injected intraperitoneally into NOD-SCID mice. Mice were randomized into 4 treatment groups and treated with vehicle, entinostat, olaparib, or the combination. The mice were monitored for toxicity and by bioluminescence imaging (BLI). At sacrifice, tumor burden was quantified. Results: In cell culture assays, entinostat significantly enhanced the sensitivity of SKOV3 and ID8 cells to Olaparib. Entinostat combined with olaparib led to synergistic reductions in cell proliferation and clonogenicity in SKOV-3 and ID8 ovarian cancer cells, compared to each drug alone. Evidence of DNA damage was enhanced by the drug combination. In the SKOV3-luc xenograft mouse model, a significant reduction in tumor burden in the group of mice treated with the combination of entinostat and olaparib, compared to each drug alone. There was no significant toxicity with drug treatment. Conclusion: Entinostat sensitizes ovarian cancer cells to Olaparib in vitro and in vivo. Experiments in ID-luciferase and patient-derived xenograft models are ongoing. These preclinical models are powerful tools that will be used to discover markers and mechanisms of sensitivity and resistance to inform the parallel clinical trial. Citation Format: Vijayalaxmi G. Gupta, Yoskaly Lazo Fernandez, Katherine Roby, Harsh Pathak, Jeff Hirst, Andrew J. Wilson, Andrew Godwin, Dineo Khabele. Entinostat enhances the efficacy of olaparib in preclinical models of ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3501.

PARP inhibitors for BRCA wild type ovarian cancer; gene alterations, homologous recombination deficiency and combination therapy.

After a brief summary of the current status of poly-ADP ribose polymerase (PARP) inhibitors for ovarian cancer, we summarize the current status of PARP inhibitors for BRCA wild type ovarian cancer, especially regarding gene alterations other than BRCA, homologous recombination deficiency (HRD), and combinations. Discussion of gene alterations other than BRCA include the results of multiple gene panels studying homologous recombination repair deficiency genes and cancer susceptibility genes, and influences of these alterations on efficacy of PARP inhibitors and cancer susceptibility. Discussions of HRD include the results of phase three trials using HRD assay, the definition of HRD assays, and the latest assays. Discussions of combinations include early phase trial results and ongoing trials combining PARP inhibitors with immune checkpoint inhibitors, anti-angiogenic agents, and triplets.

Abstract PR06: ARIEL3: A phase 3, randomized, double-blind study of rucaparib vs placebo following response to platinum-based chemotherapy for recurrent ovarian cancer (OC)

Abstract Background: Rucaparib, a poly(ADP-ribose) polymerase (PARP) inhibitor, is approved in the United States for treatment of women with deleterious BRCA mutation (germline and/or somatic) associated advanced OC who have been treated with two or more chemotherapies. Rucaparib has also demonstrated antitumor activity in the treatment setting in patients (pts) with BRCA wild-type associated recurrent OC whose tumor has high genomic loss of heterozygosity (LOH). ARIEL3 evaluated rucaparib vs placebo as maintenance treatment in pts with recurrent platinum-sensitive OC. Methods: Eligible pts received ≥2 prior platinum-based therapies, had platinum-sensitive OC (disease progression ≥6 mo after penultimate platinum), and achieved a complete response (RECIST v1.1) or partial response (RECIST v1.1 or Gynecologic Cancer InterGroup CA-125 criteria) to their most recent platinum. All pts were required to have CA-125 less than the upper limit of normal. Pts were randomized 2:1 to receive oral rucaparib 600 mg BID or placebo. Investigator-assessed progression-free survival (PFS) (primary endpoint) was assessed in a step-down procedure for 3 nested cohorts: (1) BRCA mutant (deleterious germline or somatic BRCA mutation); (2) homologous recombination deficient (HRD) (BRCA mutant or BRCA wild type/LOH high); and (3) intent-to-treat (ITT) population. PFS was also assessed by blinded independent central review (BICR) (secondary endpoint) and LOH status in pts with BRCA wild type OC (exploratory endpoint). Adverse events (AEs) were summarized descriptively. Results: ARIEL3 enrolled 564 pts (375, rucaparib; 189, placebo). Nearly 200 pts (n=196) had BRCA mutation-associated OC. Of these pts, 130 had a germline BRCA mutation (82 [21.9%], rucaparib; 48 [25.4%], placebo), 56 had a somatic BRCA mutation (40 [10.7%], rucaparib; 16 [8.5%], placebo), and 10 pts had tumors with germline and/or somatic BRCA status unknown (8 [2.1%], rucaparib; 2 [1.1%], placebo). Median investigator-assessed PFS in the BRCA-mutant cohort (130, rucaparib; 66 placebo) was 16.6 mo vs 5.4 mo (hazard ratio [HR], 0.23; 95% confidence interval [CI], 0.16-0.34; P<0.0001). In the HRD cohort (236, rucaparib; 118, placebo), median PFS was 13.6 mo vs 5.4 mo (HR, 0.32; 95% CI, 0.24-0.42; P<0.0001), and in the ITT population, median PFS was 10.8 mo vs 5.4 mo (HR, 0.37; 95% CI, 0.30-0.45; P<0.0001). Median PFS by BICR in the BRCA-mutant cohort was 26.8 mo vs 5.4 mo (HR, 0.20; 95% CI, 0.13-0.32; p<0.0001). In the HRD cohort, median PFS by BICR was 22.9 mo vs 5.5 mo (HR, 0.34; 95% CI, 0.24-0.47; p<0.0001), and in the ITT population, median PFS by BICR was 13.7 mo vs 5.4 mo (HR, 0.35; 95% CI, 0.28-0.45; p<0.0001). In the safety population (372, rucaparib; 189, placebo), the most common treatment-emergent AEs (≥35% of pts in either arm) included nausea (75.3% and 36.5%), asthenia/fatigue (69.4% and 43.9%), dysgeusia (39.2% and 6.9%), anemia (37.4% and 5.8%), constipation (36.6% and 23.8%), and vomiting (36.6% and 14.8%). The most common grade 3 or higher treatment-emergent AEs were anemia (18.8% and 0.5%) and alanine/aspartate aminotransferase increase (10.5% and 0%). At the visit cutoff date (15 April 2017), 13.4% and 1.6% of pts discontinued maintenance treatment due to treatment-emergent AEs (excluding disease progression), and 1.6% and 1.1% of pts died due to treatment-emergent AEs (including disease progression). Conclusion: Rucaparib significantly improved PFS vs placebo in pts with platinum-sensitive, recurrent OC in all primary analysis groups of pts with platinum-sensitive, recurrent OC. Additionally, rucaparib significantly improved PFS vs placebo in pts with BRCA wild-type OC (LOH high and LOH low). Clinical trial identification: NCT01968213. This abstract is also being presented as Poster A47. Citation Format: Robert L. Coleman, Amit M. Oza, Domenica Lorusso, Carol Aghajanian, Ana Oaknin, Andrew Dean, Nicoletta Colombo, Johanne I. Weberpals, Andrew Clamp, Giovanni Scambia, Alexandra Leary, Robert W. Holloway, David M. O’Malley, Terri Cameron, Lara Maloney, Sandra Goble, Kevin Lin, James Sun, Heidi Giordano, Jonathan A. Ledermann. ARIEL3: A phase 3, randomized, double-blind study of rucaparib vs placebo following response to platinum-based chemotherapy for recurrent ovarian cancer (OC). [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr PR06.

Abstract IA01: PARP inhibitors as single agents and in combinations for ovarian cancer: What lies ahead?

Abstract Poly (ADP ribose) polymerase (PARP) inhibitors are an exciting and promising new class of anticancer drugs. Initial clinical trials of PARP inhibitors began over a decade ago following the discovery that PARP inhibitors in vitro had heightened anticancer activity in BRCA mutated cancer cells compared to BRCA wild-type cells. PARP inhibitor clinical development has taken several strategies, including single-agent and combination testing. Single-agent PARP inhibitors have been used as either primary treatment of recurrent ovarian cancer or as maintenance treatment following anticancer response after platinum-based chemotherapy. Three PARP inhibitors are now FDA approved for recurrent ovarian cancer, all as single agents: 1) olaparib for patients with recurrent germline BRCA mutated ovarian cancer who have received 3 or more prior lines of chemotherapy and also as maintenance therapy post-platinum therapy for patients with platinum sensitive recurrence who are in response to platinum-based chemotherapy and regardless of BRCA or tumor HR status; 2) rucaparib for patients with BRCA mutated ovarian cancer (either deleterious tumor or germline mutation) who have received at least 2 prior lines of chemotherapy; and 3) niraparib for platinum-sensitive recurrent ovarian cancer patients as maintenance therapy who are in response to platinum-based chemotherapy and regardless of BRCA or tumor HR status. Because of the myelosuppression observed with PARP inhibitors, combining these agents with chemotherapy has been difficult and has required lowering the doses of either the PARP inhibitor and/or the chemotherapy agents and often abbreviating the treatment schedule; several negative phase III studies have been reported. Combining PARP inhibitors with biologic agents is another strategy currently being tested in clinical trials and one that avoids overlapping toxicities. The combination of the PARP inhibitor olaparib and the antivascular endothelial growth factor receptor agent cediranib has shown promising phase II results against olaparib alone, especially in BRCA wild-type ovarian cancer. These results have led to phase III studies comparing the olaparib and cediranib combination to standard therapies (NCT02502266 and NCT02446600). Other studies are under way testing PARP inhibitors with other biologic agents such as immunotherapy agents and other targeted agents such as ATR inhibitors, PI3 kinase inhibitors, and heat shock protein 90 inhibitors. Citation Format: Ursula A. Matulonis. PARP inhibitors as single agents and in combinations for ovarian cancer: What lies ahead? [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr IA01.