Randomized Trial of Oral Cyclophosphamide and Veliparib in High-Grade Serous Ovarian, Primary Peritoneal, or Fallopian Tube Cancers, or BRCA-Mutant Ovarian Cancer

Real-life clinical benefit of oral metronomic cyclophosphamide administration in elderly and heavily pretreated epithelial ovarian cancer patients

PURPOSE

Oral metronomic cyclophosphamide (OMC) implicates the daily administration of low doses of chemotherapy. Its antitumor activity combined with an oral administration route and a good toxicity profile makes OMC an attractive option for heavily pretreated patients. We retrospectively evaluated OMC's clinical benefit and objective response in recurrent ovarian cancer patients.

METHODS

This is a retrospective observational study involving patients treated with OMC (50 mg daily) from 2017 to 2022 at the Academic Division Gynaecology, Mauriziano Hospital, Torino, Italy. Clinical benefit assessment included CA125 response, radiological response, and reported symptomatic improvement. Toxicities were reported using Common Terminology Criteria for Adverse Events version 5.0.

RESULTS

Thirty-eight patients (average age 72, range 49-88) were included. 90% had FIGO stage III/IV at diagnosis and 64% underwent ≥ 3 previous lines of chemotherapy. Before OMC, 79% had ECOG 1 or 2. 8.6% of patients had a partial response (PR), and 40% a stable disease (SD). Median duration of response was 7.4 months. After 3 months on OMC, 51% experienced symptom improvement, and 53.3% experienced Ca125 reduction or stabilization. 66.7% of patients older than 75 responded to treatment; in 40% of cases, responses lasted ≥ 6 months (p = 0.08). No G3-4 hematological toxicities occurred. Nausea and fatigue G1-G2 were reported in 5 (13%) and 13 (34%) cases, respectively.

CONCLUSION

OMC is a feasible therapeutic option for recurrent ovarian cancer, providing satisfying clinical responses with a good toxicity profile, even in elderly and heavily pretreated patients with a suboptimal performance status.

A retrospective, real-life analysis of metronomic oral single-agent cyclophosphamide for the treatment of platinum-pretreated advanced ovarian carcinoma in Italy

INTRODUCTION

Metronomic oral cyclophosphamide (MOC) presents many potential advantages, such as significantly less severe side effects than standard regimens, ease of administration, and the delivery of a dose-dense but not necessarily dose-intense treatment. These observations prompted us to evaluate in a retrospective, multicenter study the efficacy and toxicity of MOC in a real-life series of pretreated cancer patients.

METHODS

The study is a multicenter, retrospective analysis of the activity of single-agent MOC in patients with recurrent or residual epithelial ovarian, fallopian tube, or primary. Eligible patients were continuously treated with MOC at 50 mg/day until progression, toxicity, or death. Overall response rate (ORR), stable disease (SD), and disease control rate (DCR) were reported.

RESULTS

The study included 62 patients. Three patients reached a complete response rate (5%), 11 had a partial response rate (18), and 15 had stabilization of disease (24) for an ORR of 23% and a DCR of 47%. Patients with low-grade indolent tumors showed an ORR and an SD rate higher than that observed in non-indolent ones (33% vs. 18% and 28% vs. 14%, respectively). Overall, progression-free survival was 3.5 months (range 1-9 months).

CONCLUSION

Single-agent MOC is active and very well tolerated in a significant fraction of patients with refractory, recurrent, or residual epithelial ovarian, fallopian tube, or primary peritoneal cancer. In the vision of a practical approach, single-agent MOC may be a useful palliative treatment option for patients with poor tolerance to high-dose regimens or widely pretreated. Further studies are needed better to characterize the role of such an approach in clinical practice.

Veliparib‑Induced Toxicity in Cancer Patients: A Systematic Review and Meta‑Analysis

In this study, we investigate the veliparib‑induced toxicity in cancer patients. Databases were searched for RCTs treated with veliparib. We found veliparib could increase the risk of hematologic and gastrointestinal toxicities. Anemia, neutropenia, thrombocytopenia, and nausea were the most common toxicities. Patients diagnosed with gastrointestinal tumors tend to have a higher risk of high-grade neutropenia; patients in the first-line setting tend to have a higher risk of high-grade anemia and neutropenia than those in the ≥ second line setting. Patients receiving higher dosage of veliparib tend to have a higher risk of all-grade anemia. Veliparib could also increase the risk of insomnia, myalgia, pneumonia, dyspnea, hyponatremia, and fatigue.

PARP inhibitor era in ovarian cancer treatment: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Ovarian cancer is the eighth leading cause of cancer-related death among women, characterized by late diagnosis and a high relapse rate. In randomized controlled trials, we aimed to evaluate the efficacy and safety of PARP inhibitors (PARPi) in treating advanced ovarian cancer.

METHODS

This review was registered on PROSPERO (CRD42021283150), included all phase II and phase III randomized controlled trials (RCTs) assessing the effect of PARPi on ovarian cancer until the 13th of April, 2022. The main outcomes were progression- free survival (PFS), overall survival (OS), and adverse events (AEs). Pooled hazard ratios (HRs), and risk ratios (RRs) were calculated with 95% confidence intervals (95% CI). The random-effects model was applied in all analyses.

RESULTS

In the meta-analysis, 16 eligible RCTs were included, with a total of 5,815 patients. In recurrent ovarian cancer, PARPi maintenance therapy showed a significant PFS benefit over placebo in the total population (HR 0.34, CI 0.29-0.40), BRCA mutant (HR 0.24, CI 0.18-0.31), germline BRCA mutant (HR 0.23, CI 0.18-0.30), and BRCA wild-type cases (HR 0.50, CI 0.39-0.65). PARPi monotherapy also improved PFS (HR 0.62, CI 0.51-0.76) compared with chemotherapy in BRCAm patients with recurrent ovarian cancer. The use of PARPi maintenance therapy resulted in an improvement in PFS over placebo in newly-diagnosed cancers in the overall population (HR 0.46, CI 0.30-0.71) and the BRCAm population (HR 0.36, CI 0.29-0.44). Although the risk of severe AEs was increased by PARPi therapy compared to placebo in most settings investigated, these side effects were controllable with dose modification, and treatment discontinuation was required in the minority of cases.

CONCLUSIONS

PARPis are an effective therapeutic option for newly-diagnosed and recurrent ovarian cancer. Despite a minor increase in the frequency of serious adverse effects, they are generally well tolerated.

PARP inhibitors in ovarian cancer

Poly-ADP-ribose polymerase inhibitors (PARPis) were first approved for the treatment of epithelial ovarian cancer (EOC), where as a maintenance therapy they transformed clinical management of this disease in both patients with and without homologous recombination deficiency. In this review, we provide a historical overview of PARPi use in EOC and discuss recent updates on overall survival data, highlighting their impact on regulatory approvals. We explore their potential as combination regimens with antiangiogenic and cell-cycle checkpoint inhibitors, as well as other small molecule inhibitors, to overcome resistance mechanisms and enhance therapeutic efficacy, providing a future perspective on the use of PARPis in EOC treatment.

Efficacy and safety of combination of poly-ADP-ribose polymerase inhibitor (PARPi) and chemotherapy compared with chemotherapy alone in treatment of recurrent ovarian carcinoma: a systematic review

Platinum-based chemotherapy after surgical cytoreduction is the universal treatment for advanced ovarian cancer (OC), however, about eighty percent of patients experienced relapse and progression-free survival remained poor. Patients who relapsed within one year of treatment eventually become resistant to second-line chemotherapy. Poly-ADP-ribose polymerase inhibitors are a novel class of targeted therapy that could overcome these challenges by augmenting the chemotherapeutic activity of other cytotoxic agents. Cumulative Index to Nursing and Allied Health Literature (CINHAL), Cochrane and PubMed databases were searched for potentially relevant primary publications from 2011 to 2022 reporting on efficacy and safety of combination of a PARP inhibitor and chemotherapy versus chemotherapy in recurrent OC and reviewed. The outcomes of interest assessed qualitatively were progression-free survival (PFS) and grade 3 or higher adverse events (AEs) as measures of efficacy and safety respectively. Eight randomized controlled trials (RCTs) were included in the systematic review comprising 3,021 patients evaluated efficacy and safety of PARP inhibitors: Olaparib, niraparib and veliparib with combinations of bevacizumab, carboplatin, cisplatin, cediranib, cyclophosphamide and paclitaxel. 824 patients had 33 BRCA mutation while 1,430 had wild-type BRCA, an allele that confers increased risk of cancer. Most patients had platinum-sensitive cancers. There was significant prolongation of PFS with PARP inhibitor and chemotherapy combination compared to chemotherapy in all included trials except one which combined veliparib with cyclophosphamide. The prolongation of PFS was more remarkable in patients with BRCA mutation and occasionally patients with wild-type BRCA. Niraparib and veliparib were notably associated with grade 3 or higher anaemia, neutropenia, and thrombocytopenia, olaparib caused fatigue and gastrointestinal disturbances while bevacizumab and cediranib caused hypertension. This review suggested combined PARP inhibitor and chemotherapy significantly prolonged progression-free survival especially in patients with BRCA mutation compared to chemotherapy and the combined therapy is safe.

A review and metanalysis of metronomic oral single-agent cyclophosphamide for treating advanced ovarian carcinoma in the era of precision medicine

OBJECTIVE

Oral metronomic cyclophosphamide has been used as a single agent or in combination with other drugs for several solid tumors with interesting results in disease palliation and mild to moderate toxicity, notably in patients with recurrent epithelial ovarian cancer (EOC) progressing after systemic chemotherapy. In this paper, we report a review and a metanalysis of heterogeneous data published up to date.

DATA SOURCES

The literature search was restricted to single-agent MOC. The analysis was conducted through March 2023 by consulting PubMed, Embase, Google Scholar, and The Cochrane Library databases. Research string and Medical Subject Headings included "ovarian tumor," "ovarian carcinoma," or "ovarian cancer," "fallopian tube cancer," "primary peritoneal cancer," "oral chemotherapy," and "metronomic cyclophosphamide." All articles were assessed for quality by at least two investigators independently, and a < 18 patients sample size cutoff was chosen as a lower limit with a Cohen's kappa statistical coefficient for accuracy and reliability. Metanalysis of selected papers was carried out according to a fixed model.

DATA SUMMARY

The percentage of agreement between investigators on literature study selection was very high, reaching 96.9% with a Cohen's k of 0.929. MOC pooled objective response rate (ORR) and disease control rate for recurrent or platinum-refractory ovarian cancer were 18.8% (range 4-44%) and 36.2% (range 16-58.8%), respectively. The mean progressive-free survival and overall survival were 3.16 months (range 1.9 to 5.0 months) and 8.7 months (range 8 to 13 months), respectively. The fixed model metanalysis of selected studies showed a 16% median ORR (12-20% CI, p < 0.001).

CONCLUSIONS

Single-agent oral cyclophosphamide in EOC holds promise as a treatment option, even in the era of precision medicine. Genetic factors, such as DNA repair gene polymorphisms, may influence treatment response. Combining cyclophosphamide with biological agents such as PARP inhibitors or immunotherapy agents is an area of active investigation.

DNA repair biomarkers to guide usage of combined PARP inhibitors and chemotherapy: A meta-analysis and systematic review

PURPOSE

The addition of PARP inhibitors to chemotherapy has been assessed in > 80 clinical trials across multiple malignancies, on the premise that PARP inhibitors will increase chemotherapy effectiveness regardless of whether cancers have underlying disruption of DNA repair pathways. Consequently, the majority of combination therapy trials have been performed on patients without biomarker selection, despite the use of homologous recombination deficiency to dictate use of PARP inhibitors in the maintenance setting. An unresolved question is whether biomarkers are needed to identify patients who respond to combination PARP inhibitors and chemotherapy.

METHODS

A systematic literature review identified studies using PARP inhibitors in combination with chemotherapy versus chemotherapy alone, where the study included a biomarker of DNA repair function (BRCA1, BRCA2, homologous recombination deficiency test, ATM, ERCC1, SLFN11). Hazard ratios (HR) were pooled in a meta-analysis using generic inverse-variance, and fixed or random effects modelling. Subgroup analyses were conducted on biomarker selection and type of malignancy.

RESULTS

Nine studies comprising 2547 patients met the inclusion criteria. Progression-free survival (PFS) was significantly better in patients with a DNA repair biomarker (HR: 0.57, 95% CI: 0.48-0.68, p < 0.00001), but there was no benefit in patients who lacked a biomarker (HR: 0.94, 95% CI: 0.82-1.08, p = 0.38). Subgroup analysis showed that BRCA status and SLFN11 biomarkers could predict benefit, and biomarker-driven benefit occurred in ovarian, breast and small cell lung cancers. The addition of PARP inhibitors to chemotherapy was associated with increased grade 3/4 side effects, and particularly neutropenia.

CONCLUSIONS

Combination therapy only improves PFS in patients with identifiable DNA repair biomarkers. This indicates that PARP inhibitors do not sensitise patients to chemotherapy treatment, except where their cancer has a homologous recombination defect, or an alternative biomarker of altered DNA repair. While effective in patients with DNA repair biomarkers, there is a risk of high-grade haematological side-effects with the use of combination therapy. Thus, the benefit in PFS from combination therapy must be weighed against potential adverse effects, as individual arms of treatment can also confer benefit.

Small-molecule inhibitors of kinases in breast cancer therapy: recent advances, opportunities, and challenges

Breast cancer is the most common malignancy in women worldwide and despite significant advancements in detection, treatment, and management of cancer, it is still the leading cause of malignancy related deaths in women. Understanding the fundamental biology of breast cancer and creating fresh diagnostic and therapeutic strategies have gained renewed focus in recent studies. In the onset and spread of breast cancer, a group of enzymes known as kinases are extremely important. Small-molecule kinase inhibitors have become a promising class of medications for the treatment of breast cancer owing to their capacity to specifically target kinases involved in the growth and progression of cancer. The creation of targeted treatments that block these kinases and the signalling pathways that they activate has completely changed how breast cancer is treated. Many of these targeted treatments have been approved for the treatment of breast cancer as clinical trials have demonstrated their great efficacy. CDK4/6 inhibitors, like palbociclib, abemaciclib, and ribociclib, EGFR inhibitors such as gefitinib and erlotinib and HER2-targeting small-molecule kinases like neratinib and tucatinib are some examples that have shown potential in treating breast cancer. Yet, there are still difficulties in the development of targeted medicines for breast cancer, such as figuring out which patient subgroups may benefit from these therapies and dealing with drug resistance problems. Notwithstanding these difficulties, kinase-targeted treatments for breast cancer still have a lot of potential. The development of tailored medicines will continue to be fuelled by the identification of novel targets and biomarkers for breast cancer as a result of advancements in genomic and proteomic technology.

An Overview of PARP Resistance in Ovarian Cancer from a Molecular and Clinical Perspective

Epithelial ovarian cancer (EOC), a primarily high-grade serous carcinoma (HGSOC), is one of the major causes of high death-to-incidence ratios of all gynecological cancers. Cytoreductive surgery and platinum-based chemotherapy represent the main treatments for this aggressive disease. Molecular characterization of HGSOC has revealed that up to 50% of cases have a deficiency in the homologous recombination repair (HRR) system, which makes these tumors sensitive to poly ADP-ribose inhibitors (PARP-is). However, drug resistance often occurs and overcoming it represents a big challenge. A number of strategies are under investigation, with the most promising being combinations of PARP-is with antiangiogenetic agents and immune checkpoint inhibitors. Moreover, new drugs targeting different pathways, including the ATR-CHK1-WEE1, the PI3K-AKT and the RAS/RAF/MEK, are under development both in phase I and II-III clinical trials. Nevertheless, there is still a long way to go, and the next few years promise to be exciting.

Role of PARP inhibitors beyond BRCA mutation and platinum sensitivity in epithelial ovarian cancer: a meta-analysis of hazard ratios from randomized clinical trials

BACKGROUND

PARP inhibitors (PARPi) have a well-established role in platinum-sensitive ovarian cancer (PSOC), in BRCA mutant (BRCAm), and homologous recombination deficiency (HRD) population. However, their role in wild type and homologous recombination proficient population is still not clear.

METHODS

A meta-analysis of hazard ratios (HR) of randomized control trials (RCTs) was conducted to study the role of PARPi. The published RCTs comparing the efficacy of PARP inhibitors alone or in combination with chemotherapy and/or target therapies versus placebo/chemotherapy alone/target therapy alone in primary or recurrent ovarian cancer settings were selected. Progression-free survival (PFS) and overall survival (OS) were the primary endpoints.

RESULTS

A total of 14 primary studies and 5 updated studies are considered, consisting of 5363 patients. Overall, HR for PFS was 0.50 [95% CI 0.40-0.62]. HR of PFS was 0.94 [95% CI 0.76-1.15] in the PROC group, 0.41 [95% CI 0.29-0.60] was in HRD with BRCA unknown (BRCAuk), 0.38 [95% CI 0.26-0.57] in HRD with BRCAm, and 0.52 [95% CI 0.38-0.71] in HRD with BRCAwt. In the HRP group, overall HR for PFS was 0.67 [95% CI 0.56-0.80], 0.61 [95% CI 0.38-0.99] in HRD unknown with BRCA wt, and 0.40 [95% CI 0.29-0.55] in BRCAm HR for PFS. Overall, HR for OS was 0.86 [95% CI 0.73-1.031].

CONCLUSIONS

The results suggest that PARPi have a meaningful clinical benefit in PSOC, HRD, BRACm, and also in HRP and PROC; however, the evidence is not sufficient to recommend their routine use and further studies are needed to expand their role in the HRP and PROC groups.

The Current Status of DNA-Repair-Directed Precision Oncology Strategies in Epithelial Ovarian Cancers

Survival outcomes for patients with advanced ovarian cancer remain poor despite advances in chemotherapy and surgery. Platinum-based systemic chemotherapy can result in a response rate of up to 80%, but most patients will have recurrence and die from the disease. Recently, the DNA-repair-directed precision oncology strategy has generated hope for patients. The clinical use of poly(ADP-ribose) polymerase (PARP) inhibitors in BRCA germ-line-deficient and/or platinum-sensitive epithelial ovarian cancers has improved survival. However, the emergence of resistance is an ongoing clinical challenge. Here, we review the current clinical state of PARP inhibitors and other clinically viable targeted approaches in epithelial ovarian cancers.

Therapeutic targeting of DNA damage repair pathways guided by homologous recombination deficiency scoring in ovarian cancers

The susceptibility of cells to DNA damage and their DNA repair ability are crucial for cancer therapy. Homologous recombination is one of the major repairing mechanisms for DNA double-strand breaks. Approximately half of ovarian cancer (OvCa) cells harbor homologous recombination deficiency (HRD). Considering that HRD is a major hallmark of OvCas, scholars proposed HRD scoring to evaluate the HRD degree and guide the choice of therapeutic strategies for OvCas. In the last decade, synthetic lethal strategy by targeting poly (ADP-ribose) polymerase (PARP) in HR-deficient OvCas has attracted considerable attention in view of its favorable clinical effort. We therefore suggested that the uses of other DNA damage/repair-targeted drugs in HR-deficient OvCas might also offer better clinical outcome. Here, we reviewed the current small molecule compounds that targeted DNA damage/repair pathways and discussed the HRD scoring system to guide their clinical uses.

Combining Poly (ADP-Ribose) Polymerase (PARP) Inhibitors with Chemotherapeutic Agents: Promise and Challenges

Better understanding of molecular drivers and dysregulated pathways has furthered the concept of precision oncology and rational drug development. The role of DNA damage response (DDR) pathways has been extensively studied in carcinogenesis and as potential therapeutic targets to improve response to chemotherapy or overcome resistance. Treatment with small molecule inhibitors of PARP has resulted in clinical response and conferred survival benefit to patients with ovarian cancer, BRCA-mutant breast cancer, HRD-deficient prostate cancer and BRCA-mutant pancreatic cancer, leading to US Food and Drug Administration (FDA) approvals. However, the observed clinical benefit with single agent PARP inhibitors is limited to few tumor types within the relevant genetic context. Since DDR pathways are essential for repair of damage caused by cytotoxic agents, PARP inhibitors have been evaluated in combination with various chemotherapeutic agents to broaden the therapeutic application of this class of drugs. In this chapter, we discuss the combination of PARP inhibitors with different chemotherapeutics agents, clinical experience to date, lessons learnt, and future directions for this approach.

Towards Personalized Management of Ovarian Cancer

Despite advances in surgery and chemotherapy, the overall outcomes for patients with advanced ovarian cancer remain poor. Although initial response rates to platinum-based chemotherapy is about 60-80%, most patients will have recurrence and succumb to the disease. However, a DNA repair-directed precision medicine strategy has recently generated real hope in improving survival. The clinical development of PARP inhibitors has transformed lives for many patients with BRCA germline-deficient and/or platinum-sensitive epithelial ovarian cancers. Antiangiogenic agents and intraperitoneal chemotherapy approaches may also improve outcomes in patients. Moreover, evolving immunotherapeutic opportunities could also positively impact patient outcomes. Here we review the current clinical state of PARP inhibitors and other clinically viable targeted approaches in ovarian cancer.

Combined inhibition of BADSer99 phosphorylation and PARP ablates models of recurrent ovarian carcinoma

Background

Poly (ADP-ribose) polymerase inhibitors (PARPis) have been approved for the treatment of recurrent epithelial ovarian cancer (EOC), regardless of BRCA status or homologous recombination repair deficiency. However, the low response of platinum-resistant EOC, the emergence of resistance in BRCA-deficient cancer, and therapy-associated toxicities in patients limit the clinical utility of PARPis in recurrent EOC.

Methods

The association of phosphorylated (p) BADS99 with clinicopathological parameters and survival outcomes in an EOC cohort was assessed by immunohistochemistry. The therapeutic synergy, and mechanisms thereof, between a pBADS99 inhibitor and PARPis in EOC was determined in vitro and in vivo using cell line and patient-derived models.

Results

A positive correlation between pBADS99 in EOC with higher disease stage and poorer survival is observed. Increased pBADS99 in EOC cells is significantly associated with BRCA-deficiency and decreased Cisplatin or Olaparib sensitivity. Pharmacological inhibition of pBADS99 synergizes with PARPis to enhance PARPi IC₅₀ and decreases survival, foci formation, and growth in ex vivo culture of EOC cells and patient-derived organoids (PDOs). Combined inhibition of pBADS99 and PARP in EOC cells or PDOs enhances DNA damage but impairs PARPi stimulated DNA repair with a consequent increase in apoptosis. Inhibition of BADS99 phosphorylation synergizes with Olaparib to suppress the xenograft growth of platinum-sensitive and resistant EOC. Combined pBADS99-PARP inhibition produces a complete response in a PDX derived from a patient with metastatic and chemoresistant EOC.

Conclusions

A rational and efficacious combination strategy involving combined inhibition of pBADS99 and PARP for the treatment of recurrent EOC is presented.

Ovarian cancer is difficult to successfully treat because it often recurs as the cancer becomes resistant to drugs used to treat it. As such, new drugs or combinations of drugs are needed to treat patients with recurrent ovarian cancer. Here, a drug combination is reported that is effective in experimental models of ovarian cancer, including those derived from patients. The combination approach uses drugs that have previously been approved for use in patients, known as PARP inhibitors, and another drug to inhibit cancer cell survival by targeting activation of a specific protein involved in cancer cell survival. The net effect of this drug combination in ovarian cancer models is greater than the sum of the drugs used individually. With further testing, this combination may offer a potential strategy to treat patients with recurrent ovarian cancer.

Zhang et al. test the therapeutic potential of an inhibitor of BAD phosphorylation, NPB, in epithelial ovarian cancer. The authors show that the small molecule synergises with PARP inhibition to kill patient-derived ovarian cancer organoids and suppress the growth of xenograft tumours, including a cisplatin-resistant model.

Improving PARP inhibitor efficacy in high-grade serous ovarian carcinoma: A focus on the immune system

High-grade serous ovarian carcinoma (HGSOC) is a genomically unstable malignancy responsible for over 70% of all deaths due to ovarian cancer. With roughly 50% of all HGSOC harboring defects in the homologous recombination (HR) DNA repair pathway (e.g., BRCA1/2 mutations), the introduction of poly ADP-ribose polymerase inhibitors (PARPi) has dramatically improved outcomes for women with HR defective HGSOC. By blocking the repair of single-stranded DNA damage in cancer cells already lacking high-fidelity HR pathways, PARPi causes the accumulation of double-stranded DNA breaks, leading to cell death. Thus, this synthetic lethality results in PARPi selectively targeting cancer cells, resulting in impressive efficacy. Despite this, resistance to PARPi commonly develops through diverse mechanisms, such as the acquisition of secondary BRCA1/2 mutations. Perhaps less well documented is that PARPi can impact both the tumour microenvironment and the immune response, through upregulation of the stimulator of interferon genes (STING) pathway, upregulation of immune checkpoints such as PD-L1, and by stimulating the production of pro-inflammatory cytokines. Whilst targeted immunotherapies have not yet found their place in the clinic for HGSOC, the evidence above, as well as ongoing studies exploring the synergistic effects of PARPi with immune agents, including immune checkpoint inhibitors, suggests potential for targeting the immune response in HGSOC. Additionally, combining PARPi with epigenetic-modulating drugs may improve PARPi efficacy, by inducing a BRCA-defective phenotype to sensitise resistant cancer cells to PARPi. Finally, invigorating an immune response during PARPi therapy may engage anti-cancer immune responses that potentiate efficacy and mitigate the development of PARPi resistance. Here, we will review the emerging PARPi literature with a focus on PARPi effects on the immune response in HGSOC, as well as the potential of epigenetic combination therapies. We highlight the potential of transforming HGSOC from a lethal to a chronic disease and increasing the likelihood of cure.

Cancer chemotherapy: insights into cellular and tumor microenvironmental mechanisms of action

Chemotherapy has historically been the mainstay of cancer treatment, but our understanding of what drives a successful therapeutic response remains limited. The diverse response of cancer patients to chemotherapy has been attributed principally to differences in the proliferation rate of the tumor cells, but there is actually very little experimental data supporting this hypothesis. Instead, other mechanisms at the cellular level and the composition of the tumor microenvironment appear to drive chemotherapy sensitivity. In particular, the immune system is a critical determinant of chemotherapy response with the depletion or knock-out of key immune cell populations or immunological mediators completely abrogating the benefits of chemotherapy in pre-clinical models. In this perspective, we review the literature regarding the known mechanisms of action of cytotoxic chemotherapy agents and the determinants of response to chemotherapy from the level of individual cells to the composition of the tumor microenvironment. We then summarize current work toward the development of dynamic biomarkers for response and propose a model for a chemotherapy sensitive tumor microenvironment.

Recent Insights into PARP and Immuno-Checkpoint Inhibitors in Epithelial Ovarian Cancer

Ovarian cancer is one of the most common gynecologic cancers and has the highest mortality rate of any other cancer of the female reproductive system. Epithelial ovarian cancer (EOC) accounts for approximately 90% of all ovarian malignancies. The standard therapeutic strategy includes cytoreductive surgery accompanied by pre- or postoperative platinum-based chemotherapy. Nevertheless, up to 80% of the patients relapse within the following 12-18 months from the completion of the treatment and then receive first-line chemotherapy depending on platinum sensitivity. Mutations in BRCA1/2 genes are the most significant molecular aberrations in EOC and serve as prognostic and predictive biomarkers. Poly ADP-ribose polymerase (PARP) inhibitors exploit defects in the DNA repair pathway through synthetic lethality. They have also been shown to trap PARP1 and PARP2 on DNA, leading to PARP-DNA complexes. Olaparib, rucaparib, and niraparib have all obtained Food and Drug Administration (FDA) and/or the European Medicine Agency (EMA) approval for the treatment of EOC in different settings. Immune checkpoint inhibitors (ICI) have improved the survival of several cancers and are under evaluation in EOC. However, despite the success of immunotherapy in other malignancies, the use of antibodies inhibiting the immune checkpoint programmed cell death (PD-1) or its ligand (PD-L1) obtained modest results in EOC so far, with median response rates of up to 10%. As such, ICI have not yet been approved for the treatment of EOC. We herein provided a comprehensive insight into the most recent progress in synthetic lethality PARP inhibitors, along with the mechanisms of resistance. We also summarised data regarding the role of immune checkpoint inhibitors, the use of vaccination therapy, and adoptive immunotherapy in treating epithelial ovarian cancer.

Poly(ADP-ribose) polymerase (PARP) inhibitors for the treatment of ovarian cancer

BACKGROUND

Ovarian cancer is the sixth most common cancer in women world-wide. Epithelial ovarian cancer (EOC) is the most common; three-quarters of women present when disease has spread outside the pelvis (stage III or IV). Treatment consists of a combination of  surgery and platinum-based chemotherapy. Although initial responses to chemotherapy are good, most women with advanced disease will relapse. PARP (poly (ADP-ribose) polymerase) inhibitors (PARPi), are a type of anticancer treatment that works by preventing cancer cells from repairing DNA damage, especially in those with breast cancer susceptibility gene (BRCA) variants. PARPi offer a different mechanism of anticancer treatment from conventional chemotherapy.

OBJECTIVES

To determine the benefits and risks of poly (ADP-ribose) polymerase) inhibitors (PARPi) for the treatment of epithelial ovarian cancer (EOC).

SEARCH METHODS

We identified randomised controlled trials (RCTs) by searching the Cochrane Central Register of Controlled Trials (Central 2020, Issue 10), Cochrane Gynaecological Cancer Group Trial Register, MEDLINE (1990 to October 2020), Embase (1990 to October 2020), ongoing trials on www.controlled-trials.com/rct, www.clinicaltrials.gov, www.cancer.gov/clinicaltrials, the National Research Register (NRR), FDA database and pharmaceutical industry biomedical literature.

SELECTION CRITERIA

We included trials that randomised women with EOC to PARPi with no treatment, or PARPi versus conventional chemotherapy, or PARPi together with conventional chemotherapy versus conventional chemotherapy alone.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodology. Two review authors independently assessed whether studies met the inclusion criteria. We contacted investigators for additional data. Outcomes included overall survival (OS), objective response rate (ORR), quality of life (QoL) and rate of adverse events.

MAIN RESULTS

We included 15 studies (6109 participants); four (3070 participants) with newly-diagnosed, advanced EOC and 11 (3039 participants) with recurrent EOC. The studies varied in types of comparisons and evaluated PARPi. Eight studies were judged as at low risk of bias in most of the domains. Quality of life data were generally poorly reported. Below we present six key comparisons.  The majority of participants had BRCA mutations, either in their tumour (sBRCAmut) and/or germline (gBRCAmut), or homologous recombination deficiencies (HRD) in their tumours. Newly diagnosed EOC Overall, four studies evaluated the effect of PARPi in newly-diagnosed, advanced EOC. Two compared PARPi with chemotherapy and chemotherapy alone. OS data were not reported. The combination of PARPi with chemotherapy may have little to no difference in progression-free survival (PFS) (two studies, 1564 participants; hazard ratio (HR) 0.82, 95% confidence interval (CI 0).49 to 1.38; very low-certainty evidence)(no evidence of disease progression at 12 months' 63% with PARPi versus 69% for placebo).  PARPi with chemotherapy likely increases any severe adverse event (SevAE) (grade 3 or higher) slightly (45%) compared with chemotherapy alone (51%) (two studies, 1549 participants, risk ratio (RR) 1.13, 95% CI 1.07 to 1.20; high-certainty evidence). PARPi combined with chemotherapy compared with chemotherapy alone likely results in little to no difference in the QoL (one study; 744 participants, MD 1.56 95% CI -0.42 to 3.54; moderate-certainty evidence).  Two studies compared PARPi monotherapy with placebo as maintenance after first-line chemotherapy in newly diagnosed EOC. PARPi probably results in little to no difference in OS (two studies, 1124 participants; HR 0.81, 95%CI 0.59 to 1.13; moderate-certainty evidence) (alive at 12 months 68% with PARPi versus 62% for placebo). However, PARPi may increase PFS (two studies, 1124 participants; HR 0.42, 95% CI 0.19 to 0.92; low-certainty evidence) (no evidence of disease progression at 12 months' 55% with PARPi versus 24% for placebo). There may be an increase in the risk of experiencing any SevAE (grade 3 or higher) with PARPi (54%) compared with placebo (19%)(two studies, 1118 participants, RR 2.87, 95% CI 1.65 to 4.99; very low-certainty evidence), but the evidence is very uncertain. There is probably a slight reduction in QoL with PARPi, although this may not be clinically significant (one study, 362 participants; MD -3.00, 95%CI -4.48 to -1.52; moderate-certainty evidence).  Recurrent, platinum-sensitive EOC Overall, 10 studies evaluated the effect of PARPi in recurrent platinum-sensitive EOC. Three studies compared PARPi monotherapy with chemotherapy alone. PARPi may result in little to no difference in OS (two studies, 331 participants; HR 0.95, 95%CI 0.62 to 1.47; low-certainty evidence) (percentage alive at 36 months 18% with PARPi versus 17% for placebo). Evidence is very uncertain about the effect of PARPi on PFS (three studies, 739 participants; HR 0.88, 95%CI 0.56 to 1.38; very low-certainty evidence)(no evidence of disease progression at 12 months 26% with PARPi versus 22% for placebo). There may be little to no difference in rates of any SevAE (grade 3 or higher) with PARPi (50%) than chemotherapy alone (47%) (one study, 254 participants; RR 1.06, 95%CI 0.80 to 1.39; low-certainty evidence). Four studies compared PARPi monotherapy as maintenance with placebo. PARPi may result in little to no difference in OS (two studies, 560 participants; HR 0.88, 95%CI 0.65 to 1.20; moderate-certainty evidence)(percentage alive at 36 months 21% with PARPi versus 17% for placebo). However, evidence suggests that PARPi as maintenance therapy results in a large PFS (four studies, 1677 participants; HR 0.34, 95% CI 0.28 to 0.42; high-certainty evidence)(no evidence of disease progression at 12 months 37% with PARPi versus 5.5% for placebo). PARPi maintenance therapy may result in a large increase in any SevAE (51%) (grade 3 or higher) than placebo (19%)(four studies, 1665 participants, RR 2.62, 95%CI 1.85 to 3.72; low-certainty evidence). PARPi compared with chemotherapy may result in little or no change in QoL (one study, 229 participants, MD 1.20, 95%CI -1.75 to 4.16; low-certainty evidence). Recurrent, platinum-resistant EOC Two studies compared PARPi with chemotherapy. The certainty of evidence in both studies was graded as very low. Overall, there was minimal information on the QoL and adverse events.

AUTHORS' CONCLUSIONS

PARPi maintenance treatment after chemotherapy may improve PFS in women with newly-diagnosed and recurrent platinum-sensitive EOC; there may be little to no effect on OS, although OS data are immature. Overall, this is likely at the expense of an increase in SevAE. It is  disappointing that data on quality of life outcomes  are relatively sparse. More research is needed to determine whether PARPi have a role to play in platinum-resistant disease.

Molecular methods for increasing the effectiveness of ovarian cancer treatment: a systematic review

Background: The aim of the current study is to analyze and summarize the latest research on improving therapy in ovarian cancer. Materials & methods: Data analysis was based on a review of publications from 2011 to 2021 in the PubMed database with use of the search terms including 'EGFR ovarian cancer', 'folate receptor inhibitors ovarian cancer', 'VEGF ovarian cancer', 'PDGF ovarian cancer' and 'CTLA-4 ovarian cancer'. Results: 6643 articles were found; 238 clinical trials and randomized control trials were analyzed; 122 studies were rejected due to inconsistency with the topic of the work. Conclusion: Extensive research on the treatment of ovarian cancer increases the chance of developing the most effective therapy suited to the individual needs of the patient.

Veliparib for the treatment of solid malignancies

OBJECTIVE

Veliparib is a poly adenosine diphosphate ribose polymerase (PARP) -1 and -2 inhibitor with chemo-sensitizing and anticancer activities that has shown promising results in early-phase trials. The aim of this comprehensive review is to summarise the profile of veliparib and to provide an overview of its early clinical investigations.

DATA SOURCES

Details of all the completed trials evaluating the profile of veliparib were identified from ClinicalTrials.gov with the relevant keywords. Furthermore, databases such as Google Scholar and PubMed were searched using the National Clinical Trial (NCT) number to retrieve publications of results not listed in the trial registry.

DATA SUMMARY

A total of 25 completed clinical trials indicating the use of veliparib in solid malignancies were identified. The results showed that veliparib is well tolerated, both as a single agent and in combination with standard chemotherapy doses. Being a broad-spectrum potentiator of DNA-damaging agents and radiation, it has shown to improve the clinical outcomes, particularly in solid tumors like ovarian cancer, breast cancer and lung cancer.

CONCLUSIONS

The results from clinical trials indicate that veliparib can be an excellent therapeutic strategy for BRCA mutation associated cancers and tumors bearing deficiencies in the HR pathway as well. Further studies establishing the dosing, sequence of therapy, extended use and compatibility with various anti-cancer drugs are warranted to define its exact role in cancer therapy.

A phase I study of veliparib with cyclophosphamide and veliparib combined with doxorubicin and cyclophosphamide in advanced malignancies

PURPOSE

Veliparib (V), an oral poly(ADP-ribose) polymerase (PARP) inhibitor, potentiates effects of alkylating agents and topoisomerase inhibitors in preclinical tumor models. We conducted a phase I trial of V with iv cyclophosphamide (C) and V plus iv doxorubicin (A) and C.

METHODS

Objectives were to establish the maximum tolerated dose (MTD) of the combinations, characterize V pharmacokinetics (PK) in the presence and absence of C, measure PAR in peripheral blood mononuclear cells (PBMCs) and γH2AX in circulating tumor cells (CTCs). In Group 1, dose escalations of V from 10 to 50 mg every 12 h Days 1-4 plus C 450 to 750 mg/m² Day 3 in 21-day cycles were evaluated. In Group 2, V doses ranged from 50 to 150 mg every 12 h Days 1-4 with AC (60/600 mg/m²) Day 3 in 21-day cycles. In Group 3, patients received AC Day 1 plus V Days 1-7, and in Group 4, AC Day 1 plus V Days 1-14 was given in 21-day cycles to evaluate effects on γH2AX foci.

RESULTS

Eighty patients were enrolled. MTD was not reached for V and C. MTD for V and AC was V 100 mg every 12 h Days 1-4 with AC (60/600 mg/m2) Day 3 every 21 days. V PK appears to be dose-dependent and has no effect on the PK of C. Overall, neutropenia and anemia were the most common adverse events. Objective response in V and AC treated groups was 22% (11/49). Overall clinical benefit rate was 31% (25/80). PAR decreased in PBMCs. Percentage of γH2AX-positive CTCs increased after treatment with V and AC.

CONCLUSION

V and AC can be safely combined. Activity was observed in patients with metastatic breast cancer.

Perspectives on PARP Inhibitor Combinations for Ovarian Cancer

Poly (ADP-ribose) polymerase (PARP) inhibitors constitute an important treatment option for ovarian cancer nowadays. The magnitude of benefit from PARP inhibitors is influenced by the homologous recombination status, with greater benefit observed in patients with BRCA mutated or BRCA wild-type homologous recombination deficient (HRD) tumors. Although some PARP inhibitor activity has been shown in homologous recombination proficient (HRP) ovarian tumors, its clinical relevance as a single agent is unsatisfactory in this population. Furthermore, even HRD tumors present primary or secondary resistance to PARP inhibitors. Strategies to overcome treatment resistance, as well as to enhance PARP inhibitors' efficacy in HRP tumors, are highly warranted. Diverse combinations are being studied with this aim, including combinations with antiangiogenics, immunotherapy, and other targeted therapies. This review discusses the rationale for developing therapy combinations with PARP inhibitors, the current knowledge, and the future perspectives on this issue.

Targeting the DNA damage response: PARP inhibitors and new perspectives in the landscape of cancer treatment

Cancer derives from alterations of pathways responsible for cell survival, differentiation and proliferation. Dysfunctions of mechanisms protecting genome integrity can promote oncogenesis but can also be exploited as therapeutic target. Poly-ADP-Ribose-Polymerase (PARP)-inhibitors, the first approved targeted agents able to tackle DNA damage response (DDR), have demonstrated antitumor activity, particularly when homologous recombination impairment is present. Despite the relevant results achieved, a large proportion of patients fail to obtain durable responses. The development of innovative treatments, able to overcome resistance and ensure long-lasting benefit for a wider population is still an unmet need. Moreover, improvement in biomarker assays is necessary to properly identify patients who can benefit from DDR targeting agents. Here we summarize the main DDR pathways, explain the current role of PARP inhibitors in cancer therapy and illustrate new therapeutic strategies targeting the DDR, focusing on the combinations of PARP inhibitors with other agents and on cell-cycle checkpoint inhibitors.

Risk of fatigue with PARP inhibitors in cancer patients: a systematic review and meta-analysis of 29 phase II/III randomized controlled trials

Fatigue was a frequently reported adverse event associated with the use of PARP inhibitors. We performed a systematic review and meta-analysis to fully investigate the fatigue of PARP inhibitors in cancer patients. Databases were searched for randomized controlled trials (RCTs) treated with PARP inhibitors till July 2020. Twenty-nine RCTs and 9479 patients were included. This meta-analysis suggests that the use of PARP inhibitors significantly increase the risk of developing all-grade (RR, 1.25; 95%CI, 1.20-1.31; p < 0.00001; I2 = 48%) and high-grade fatigue (RR, 1.92; 95%CI, 1.51-2.45; p < 0.00001; I2 = 11%). Veliparib was associated with a relatively lower risk of fatigue. Patients with ovarian cancer tend to be associated with a higher risk of fatigue than those with non-ovarian cancer. Longer duration of therapy was associated with a higher risk of all-grade fatigue. Patients receiving PARP inhibitor monotherapy tends to be associated with a higher risk of all-grade fatigue than those receiving combination treatment.

Treatment opportunities and future perspectives for pancreatic cancer patients with germline BRCA1-2 pathogenic variants

Personalized treatments and predictive biomarkers of pancreatic cancer (PDAC) are still lacking. Recently germline mutations in BRCA 1 and 2 genes, leading to homologous repair deficiency, have emerged as new targets for more specific and effective therapies, exploiting the increased susceptibility to platinum salts and PARP inhibitors. In addition to BRCA, pathogenic variants in PALB2 and in other genes involved in the DNA damage response pathway (DDR) represent potential targets, as well as their respective somatic alterations. This enlarged molecularly-selected population sharing the BRCAness phenotype, is expected to show a higher sensibility to a number of DNA damaging agents and DDR inhibitors. However, the possibility of new therapeutic opportunities for DDR defective PDAC patients has to face the lack of solid evidence about the proper type and timing of targeted-treatments, the potential combination strategies and most importantly, the lack of informations on the functional impact of each specific pathogenic variant on the DDR pathway. This review summarizes the current and near-future options for the clinical management of PDAC patients harboring a DDR deficiency, analyzing the state of the art of the indications of platinum salts and other cytotoxic agents in the advanced and early stage PDAC, the development of PARP inhibitors and the rational for new combinations with immunotherapy and cycle checkpoint inhibitors, as well as the strategy to overcome the development of resistance over treatments.

Veliparib in combination with carboplatin/paclitaxel-based chemoradiotherapy in patients with stage III non-small cell lung cancer

OBJECTIVES

Veliparib is a potent poly(ADP)-ribose polymerase (PARP) 1 and 2 inhibitor that impedes repair of DNA damage induced by cytotoxic and radiation therapies. This phase 1 study evaluated veliparib in combination with chemoradiotherapy in patients with unresectable stage III non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

Patients received veliparib orally twice daily (BID) in escalating doses (60-240 mg, Day -3 to 1 day after last dose of radiation) combined with weekly carboplatin (area under the curve [AUC] 2 mg/mL/min), paclitaxel (45 mg/m²), and daily radiation therapy (60 Gy in 30 fractions), followed by two cycles of veliparib (120-240 mg BID, Days -2 through 5 of each 21-day cycle), carboplatin (AUC 6 mg/mL/min, Day 1 of each cycle), and paclitaxel (200 mg/m², Day 1 of each cycle) consolidation. Endpoints included veliparib maximum tolerated dose (MTD), recommended phase 2 dose (RP2D), pharmacokinetics, safety, and efficacy.

RESULTS

Forty-eight patients were enrolled. The MTD/RP2D of veliparib was 240 mg BID with chemoradiotherapy followed by 120 mg BID with consolidation. The most common any-grade adverse events (AEs) in this cohort for the whole treatment period were nausea (83%), esophagitis (75%), neutropenia (75%), and thrombocytopenia (75%). Dose-proportional pharmacokinetics of veliparib were observed. Median progression-free survival (mPFS) was 19.6 months (95% CI: 9.7-32.6). Median overall survival was estimated to be 32.6 months (95% CI: 15.0-not reached). In patients treated with the RP2D, mPFS was 19.6 months (95% CI: 3.0-not reached).

CONCLUSIONS

When combined with standard concurrent chemoradiotherapy and consolidation chemotherapy in patients with stage III NSCLC, veliparib demonstrated an acceptable safety profile and antitumor activity with an mPFS of 19.6 months.

Poly (ADP-ribose) polymerase inhibitors in solid tumours: Systematic review and meta-analysis

BACKGROUND

Poly (ADP-ribose) polymerase-inhibitors (PARPis) showed antitumour activity in BRCA1/2-mutated cancers, with more heterogeneous outcomes in tumours harbouring mutations that impair other genes involved in the DNA homologous recombination repair (HRR) or wild-type (wt).

METHODS

We conducted a systematic review and meta-analysis to better assess the role of PARPis in the treatment of metastatic solid tumours, with and without BRCA1/2 mutations. The primary end-point was progression-free survival (PFS). The secondary end-points were overall response rate (ORR) and overall survival (OS). A random-effects model was applied.

RESULTS

Twenty-nine studies (8,839 patients) were included. PFS was significantly improved (hazard ratio [HR]: 0.59, 95% confidence interval [CI]: 0.51-0.68, p < 0.001), without being affected by BRCA mutational status (p = 0.65). Significant subgroup differences were observed with regard to the tumour site (p = 0.001), line of therapy (p = 0.002), control arm (p < 0.001), type of PARPi (p < 0.001) and trials' phase (p = 0.006). PARPis were associated with ORR (relative risk: 1.35, 95% CI: 1.16-1.56, p < 0.001), with significant subgroup differences observed with regard to treatment line (p = 0.03), control arm (p = 0.04) and PARPis (p < 0.001) and independent of mutational status (p = 0.44), tumour site (p = 0.86) and trials' phase (p = 0.09). OS was significantly improved by PARPis (HR: 0.86, 95% CI: 0.80-0.92, p < 0.001), regardless of mutational status (p = 0.57), tumour site (p = 0.82), treatment line (p = 0.22), control arm (p = 0.21), PARPis (p = 0.30) and trials' phase (p = 0.26). Finally, an exploratory subgroup analysis showed a significant PFS improvement (HR: 0.51, 95% CI: 0.43-0.60, p < 0.001) with PARPis in BRCA-wt/HRR-deficient tumours.

CONCLUSION

Our results confirm the efficacy of already approved PARPi-based treatments in BRCA1/2-mutant solid tumours, support their role also in BRCA-independent HRR-deficient tumours and suggest a potentially broader efficacy in some wt tumours, perhaps with appropriate therapeutic partners. Prospective studies are warranted.

Poly (ADP-ribose) polymerase (PARP) as target for the treatment of epithelial ovarian cancer: what to know

INTRODUCTION

Poly (ADP-ribose) polymerase (PARP) inhibitors are being developed in maintenance and recurrence treatment settings of epithelial ovarian cancers (EOCs) with BRCA 1-2 gene mutation. PARP inhibitors are the first example of drugs targeting the loss of a gene suppressor: they block base-excision repair in the cancer cells, which have lost homologous recombination due to BRCA-mutation, resulting in loss of DNA repair and cell death, also known as synthetic lethality.

AREAS COVERED

This article provides an overview of PARP inhibitors in OC treatment and also an extensive section on the combined strategies of PARP inhibitors, including approved as well as currently investigated drugs. It also offers a section on the use of predictive biomarkers for PARP inhibitors treatment. Ongoing trials, including novel combinations, are discussed.

EXPERT OPINION

In recent years, there is increasing evidence that PARP inhibitor therapy can have life-long percussion in the treatment of EOC, even if some questions have to be solved yet, such as its use in combination therapy, the possibility to retreat with a PARP inhibitor, and finally how to overcome a resistance mechanism to this therapy. In this way, PARP inhibitors can obtain an important role in making a personalized therapeutic program in the case of first-line, neoadjuvant, platinum-sensitive, and resistant high-grade serous OC treatment.

Targeted therapy clinical trials in ovarian cancer: improved outcomes by gene mutation screening

Epithelial ovarian cancer is the most common and leading cause of death for gynaecologic cancer in the western world. Current standard treatments with limited selection of chemotherapies cannot meet patients' urgent needs. Novel targeted therapies may improve patients' survival rate with less side effects that have been demonstrated by using approved medicines such as poly ADP-ribose polymerase and angiogenesis inhibitors. Many classes of targeted therapies impacting cell signalling pathways related to ovarian cancer tumorigenesis have been investigated in clinical trial studies. Gene mutation screening is a powerful tool for improvement of success rate of the trials for better patient selection and interpretation of clinical outcomes. Increasing number of patients are being screened for genetic alterations particularly in 'basket' trials that are offering new, genetic-oriented therapies to patients. Thus, in this review, we have searched databases of Pubmed and Clinicaltrials.gov for the past and current phase III and selected phase II ovarian cancer clinical trials with focus on gene profiling. Lessons from both successful and failed trials and implications of ongoing trials are discussed.

Haematologic toxicities with PARP inhibitors in cancer patients: an up-to-date meta-analysis of 29 randomized controlled trials

WHAT IS KNOWN AND OBJECTIVE

Poly ADP-ribose polymerase (PARP) inhibitors have emerged as one of the most exciting new treatments for patients with certain types of cancer. Haematologic toxicities are common adverse events (AEs) for all PARP inhibitors. We conducted a meta-analysis to fully investigate the haematologic toxicities of PARP inhibitors in cancer patients.

STUDY DESIGN

PubMed/Medline and Embase were searched for articles published till September 2020. The relevant randomized controlled trials (RCTs) in cancer patients treated with PARP inhibitors were retrieved, and the systematic evaluation was performed.

RESULTS

Twenty-nine RCTs and 9247 patients were included. The current meta-analysis suggests that the use of PARP inhibitors significantly increases the risk of all-grade anaemia (RR, 2.32; 95% CI, 1.78-3.01; p < 0.00001), neutropenia (RR, 1.69; 95% CI, 1.38-2.07; p < 0.00001) and thrombocytopenia (RR, 2.54; 95% CI, 1.87-3.45; p < 0.00001). The use of these agents also significantly increased the risk of high-grade anaemia (RR, 3.06; 95% CI, 2.11-4.43; p < 0.00001), neutropenia (RR, 1.66; 95% CI, 1.33-2.07; p < 0.00001) and thrombocytopenia (RR, 2.76; 95% CI, 1.83-4.16; p < 0.00001). Anaemia was the most common haematologic toxicity, and all the five included PARP inhibitors were associated with a significant increased risk of anaemia. Combination treatment may reduce the risk of anaemia and thrombocytopenia compared to those receiving PARP inhibitor monotherapy.

WHAT IS NEW AND CONCLUSION

The available data suggested that the use of PARP inhibitors was associated with a significantly increased risk of haematologic toxicities.

Myelodysplastic syndrome and acute myeloid leukaemia in patients treated with PARP inhibitors: a safety meta-analysis of randomised controlled trials and a retrospective study of the WHO pharmacovigilance database

BACKGROUND

Poly(ADP-ribose) polymerase (PARP) inhibitors have shown efficacy and acceptable safety in a range of neoplasms, particularly in ovarian cancers. However, some concerns have emerged regarding rare and delayed adverse events including cases of myelodysplastic syndrome and acute myeloid leukaemia, for which data are scarce. The aim of this study was to estimate the risk of myelodysplastic syndrome and acute myeloid leukaemia related to PARP inhibitors, via a systematic review and safety meta-analysis, and to describe clinical features of PARP inhibitor-related myelodysplastic syndrome and acute myeloid leukaemia cases reported in WHO's pharmacovigilance database (VigiBase).

METHODS

We systematically reviewed randomised controlled trials (RCTs) comparing PARP inhibitor therapy versus control treatments (placebo and non-placebo) in adults (age ≥18 years) treated for cancer in MEDLINE, the Cochrane Central Register of Controlled Trials, and the ClinicalTrials.gov registry with ongoing surveillance up to May 31, 2020. The date range for included studies was not restricted. By a stepwise method to capture all available adverse events, we first extracted data on myelodysplastic syndrome and acute myeloid leukaemia cases from ClinicalTrials.gov. If cases were not available, we extracted them from published manuscripts, or subsequently contacted corresponding authors or sponsors to provide data. RCTs without available data from ClinicalTrials.gov, publications, or corresponding authors or sponsors were excluded. The primary outcome was the summary risk of myelodysplastic syndrome and acute myeloid leukaemia related to PARP inhibition versus placebo treatment in RCTs. We used a fixed-effects meta-analysis to obtain Peto odds ratios (ORs) with 95% CIs. In a separate observational, retrospective, cross-sectional pharmacovigilance study of VigiBase, cases of myelodysplastic syndrome and acute myeloid leukaemia related to PARP inhibitor therapy were extracted on May 3, 2020, and clinical features summarised with a focus on median duration of PARP inhibitor exposure, median latency period between first drug exposure and diagnosis, and proportion of cases resulting in death. Our systematic review and safety meta-analysis were registered with PROSPERO, CRD42020175050. Our retrospective pharmacovigilance study was registered on ClinicalTrials.gov, NCT04326023.

FINDINGS

For our safety meta-analysis, initial searches identified 1617 citations, and 31 RCTs were systematically reviewed for eligibility. 28 RCTs with available adverse events were analysed (18 placebo and ten non-placebo RCTs), with 5693 patients in PARP inhibitor groups and 3406 patients in control groups. Based on the 18 placebo RCTs (n=7307 patients), PARP inhibitors significantly increased the risk of myelodysplastic syndrome and acute myeloid leukaemia compared with placebo treatment (Peto OR 2·63 [95% CI 1·13-6·14], p=0·026) with no between-study heterogeneity (I²=0%, χ² p=0·91). The incidence of myelodysplastic syndrome and acute myeloid leukaemia across PARP inhibitor groups was 0·73% (95% CI 0·50-1·07; I²=0%, χ² p=0·87; 21 events out of 4533 patients) and across placebo groups was 0·47% (0·26-0·85; I²=0%, χ² p=1·00; three events out of 2774 patients). All 28 RCTs were rated as having unclear risk of bias. In VigiBase, 178 cases of myelodysplastic syndrome (n=99) and acute myeloid leukaemia (n=79) related to PARP inhibitor therapy were extracted. In cases with available data, median treatment duration was 9·8 months (IQR 3·6-17·4; n=96) and median latency period since first exposure to a PARP inhibitor was 17·8 months (8·4-29·2; n=58). Of 104 cases that reported outcomes, 47 (45%) resulted in death.

INTERPRETATION

PARP inhibitors increased the risk of myelodysplastic syndrome and acute myeloid leukaemia versus placebo treatment. These delayed and often lethal adverse events should be studied further to improve clinical understanding, particularly in the front-line maintenance setting.

FUNDING

None.

A phase II randomised, placebo-controlled trial of low dose (metronomic) cyclophosphamide and nintedanib (BIBF1120) in advanced ovarian, fallopian tube or primary peritoneal cancer

BACKGROUND

We investigated the safety and efficacy of a combination of the oral tyrosine kinase inhibitor, nintedanib (BIBF 1120) with oral cyclophosphamide in patients with relapsed ovarian cancer.

PATIENTS AND METHODS

Patients with relapsed ovarian, fallopian tube or primary peritoneal cancer received oral cyclophosphamide (100 mg o.d.) and were randomised (1,1) to also have either oral nintedanib or placebo. The primary endpoint was overall survival (OS). Secondary endpoints included progression free survival (PFS), response rate, toxicity, and quality of life.

RESULTS

117 patients were randomised, 3 did not start trial treatment, median age 64 years. Forty-five (39%) had received ≥5 lines chemotherapy. 30% had received prior bevacizumab. The median OS was 6.8 (nintedanib) versus 6.4 (placebo) months (hazard ratio 1.08; 95% confidence interval 0.72-1.62; P = 0.72). The 6-month PFS rate was 29.6% versus 22.8% (P = 0.57). Grade 3/4 adverse events occurred in 64% (nintedanib) versus 54% (placebo) of patients (P = 0.28); the most frequent G3/4 toxicities were lymphopenia (18.6% nintedanib versus 16.4% placebo), diarrhoea (13.6% versus 0%), neutropenia (11.9% versus 0%), fatigue (10.2% versus 9.1%), and vomiting (10.2% versus 7.3%). Patients who had received prior bevacizumab treatment had 52 days less time on treatment (P < 0.01). 26 patients (23%) took oral cyclophosphamide for ≥6 months. There were no differences in quality of life between treatment arms.

CONCLUSIONS

This is the largest reported cohort of patients with relapsed ovarian cancer treated with oral cyclophosphamide. Nintedanib did not improve outcomes when added to oral cyclophosphamide. Although not significant, more patients than expected remained on treatment for ≥6 months. This may reflect a higher proportion of patients with more indolent disease or the higher dose of cyclophosphamide used.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.govNCT01610869.

Development of new poly(ADP-ribose) polymerase (PARP) inhibitors in ovarian cancer: Quo Vadis?

Epithelial ovarian cancer (EOC) is the fifth leading cause of cancer mortality among women, potentially due to ineffectiveness of screening tests for early detection. Patients typically present with advanced disease at diagnosis, whereas, up to 80% relapse and the estimated median progression-free survival (PFS) is approximately 12–18 months. Increased knowledge on the molecular biology of EOC resulted in the development of several targeted therapies, including poly(ADP-ribose) polymerase (PARP) inhibitors. These agents have changed the therapeutic approach of the EOC and exploit homologous recombination (HR) deficiency through synthetic lethality, especially in breast cancer genes 1 and 2 (BRCA1/2) mutation carriers. Furthermore, BRCA wild-type patients with other defects in the HR repair pathway, or those with platinum-resistant tumors may obtain benefit from this treatment. While PARP inhibitors as a class display many similarities, several differences in structure can translate into differences in tolerability and antitumor activity. Currently, olaparib, rucaparib, and niraparib have been approved by Food and Drug Administration (FDA) and/or European Medicines Agency (EMA) for the treatment of EOC, while veliparib is in the late stage of clinical development. Finally, since October 2018 talazoparib is FDA and EMA approved for BRCA carriers with metastatic breast cancers. In this article, we explore the mechanisms of DNA repair, synthetic lethality, efficiency of PARP inhibition, and provide an overview of early and ongoing clinical investigations of the novel PARP inhibitors veliparib and talazoparib.

Gastrointestinal events with PARP inhibitors in cancer patients: A meta-analysis of phase II/III randomized controlled trials

WHAT IS KNOWN AND OBJECTIVE

PARP inhibitors are currently one of the most promising PARP targeted drugs for patients with certain types of cancer. Gastrointestinal (GI) events are common adverse events for all PARP inhibitors. We conducted this meta-analysis of randomized controlled trials (RCTs) to fully investigate the incidence and the relative risk of GI events in cancer patients receiving PARP inhibitors.

STUDY DESIGN

Randomized controlled trials in cancer patients treated with PARP inhibitors were retrieved, and the systematic evaluation was conducted. Embase and PubMed/Medline were searched for articles published till July 2020.

RESULTS

Twenty-nine RCTs and 9529 patients were included. The present meta-analysis suggests that the use of PARP inhibitors significantly increases the risk of developing all-grade nausea (RR, 1.46; 95% CI, 1.29-1.66; p < .00001), vomiting (RR, 1.39; 95% CI, 1.17-1.64; p = .0001), diarrhoea (RR, 1.14; 95% CI, 1.06-1.23; p = .0003) and decreased appetite (RR, 1.24; 95% CI, 1.14-1.36; p < .00001), but not for constipation. And the use of these agents significantly increased the risk of high-grade nausea (RR, 1.99; 95% CI, 1.44-2.74; p < .0001), vomiting (RR, 1.54; 95% CI, 1.11-2.14; p = .01) and decreased appetite (RR, 2.03; 95% CI, 1.22-3.40; p = .007), except for diarrhoea and constipation. Nausea was the most common GI event for these agents. Patients receiving veliparib were associated with a relatively lower risk of all-grade nausea and vomiting. Patients with ovarian cancer tend to have a higher risk of all-grade nausea and vomiting than those with non-ovarian cancer. The risk of all-grade nausea and vomiting tended to be higher when PARP inhibitors treatment was longer.

WHAT IS NEW AND CONCLUSION

PARP inhibitors were associated with a significant increased risk of GI events. Clinicians should be aware of these risks and perform regular monitoring.

Oral metronomic cyclophosphamide in advanced ovarian cancer: long-lasting clinical response in an elderly frailty patient

Elderly patients with ovarian cancer are an increasing population and many of them are frailty with an increased risk of postoperative complications, chemotherapy intolerance and mortality. Metronomic chemotherapy is the chronic administration of low, equally spaced, doses of antineoplastic drugs with therapeutic efficacy and low toxicity. Oral metronomic cyclophosphamide has gained increasing interest in recent years in the treatment of patients with recurrent ovarian cancer. We report the case of a 87-year-old and -frailty woman with advanced ovarian cancer, not eligible for surgery or standard first-line intravenous chemotherapy. The patient has received oral metronomic cyclophosphamide with a long-lasting clinical response and improved performance status. Oral metronomic cyclophosphamide is a promising treatment for elderly and frailty advanced ovarian cancer patients and should be further investigated.

Targeting Six Hallmarks of Cancer in Ovarian Cancer Therapy

Normal cells must overcome multiple protective mechanisms to develop into cancer cells. Their new capabilities include self-sufficiency in growth signals and insensitivity to antigrowth signals, evasion of apoptosis, a limitless replicative potential, sustained angiogenesis, and tissue invasion and metastasis; these are also termed the six hallmarks of cancer. A deep understanding of the genetic and protein alterations involved in these processes has enabled the development of targeted therapeutic strategies and clinical trial design in the search for ovarian cancer treatments. Clinically, significantly longer progression-free survival has been observed in the single use of PARP, MEK, VEGF and Chk1/Chk2 inhibitors. However, the clinical efficacy of the targeted agents is still restricted to specific molecular subtypes and no trials illustrate a benefit in overall survival. Exploring novel drug targets or combining current feasible biological agents hold great promise to further improve outcomes in ovarian cancer. In this review, we intend to provide a comprehensive description of the molecular alterations involved in ovarian cancer carcinogenesis and of emerging biological agents and combined strategies that target aberrant pathways, which might shed light on future ovarian cancer treatment.

Development of new medical treatment for epithelial ovarian cancer recurrence

Epithelial ovarian cancer (EOC) is the scariest gynaecological cancer. Many advances have been done with evolving knowledge, leading to the introduction of new drugs, most in maintenance setting. The antiangiogenic Bevacizumab and the three approved PARP-inhibitors-olaparib, niraparib and rucaparib-are gradually improving PFS of patients with EOC, with initial effects on OS too. But recurrence is still a heavy sentence and lethality continues to be high. Ovarian cancer is a complex disease, with different clinical presentation, histological aspect, and molecular expression, leading to disappointing results, when using a single drug. Implementation of biobanking and analysis of patients' tumour samples, before starting a treatment, could be a promising way to better understand molecular aspects of this disease, to identify markers predictive of response and to allow a better use of experimental drugs, as immunomodulators, targeted therapies, and combinations of these, to fight tumour growth and clinical progression. We reviewed the literature on the updated treatments for recurrent ovarian cancer, summarizing all the available drugs and combinations to treat patients with this diagnosis, and focusing the attention on the new approved molecules and the contemporary Clinical Trials, investigating new target therapies and new associations.

PARP Inhibition in Cancer: An Update on Clinical Development

PARP (poly(ADP-ribose) polymerase) inhibitors represent a novel class of anti-cancer therapy; they take advantage of synthetic lethality and induce cell death by exploiting a defect in DNA repair. This class of medication was initially evaluated in patients with BRCA-associated tumors, but efficacy was also demonstrated in other populations. Since 2014, four PARP inhibitors have been approved in various indications: olaparib, niraparib, and rucaparib in high-grade serous ovarian cancer, and olaparib and talazoparib in metastatic breast cancer. The exact indications and study populations vary slightly between the different approvals in both disease states but there is significant overlap. PARP inhibitors continue to be investigated in ongoing clinical trials. In line with other targeted therapies, benefit appears to be strongest in a distinct population of patients with BRCA mutations or other defects in homologous recombination repair. Combination therapies, which include anti-angiogenesis agents and immunotherapy, show promise as a strategy to broaden efficacy for unselected patients. Initial studies of PARP inhibitors in combination with chemotherapy were limited by toxicity, but further studies are underway. To date, head-to-head trials comparing various PARP inhibitors have not been conducted, so questions remain in terms of choosing a PARP inhibitor to administer when indications overlap, as well as how to sequence these medications. Here we review both completed and ongoing clinical trials involving PARP inhibitors and mechanisms of resistance to this class of drugs.

Evaluation of the Efficacy and Safety of PARP Inhibitors in Advanced-Stage Epithelial Ovarian Cancer

Purpose: PARP inhibitors are a novel targeted anti-cancer drug and a large number of clinical studies on PARP inhibitors have been accomplished. This updated meta-analysis was conducted to evaluate the efficacy and safety of PARP inhibitors in advanced-stage epithelial ovarian cancer.

Methods: Medline (PubMed), Embase, Cochrane Central Register of Controlled Trials, Web of Science, and Scopus were searched to identify the eligible trials up to April 2020. ClinicalTrials.gov was also screened for additional unpublished trials. Data extraction and risk of bias assessment were performed by two independent investigators, respectively. The hazard ratios (HRs) and its 95% confidence intervals (CI) for time-to-event data of progression-free survival (PFS) and overall survival (OS), and the risk ratios (RRs) with 95% CI for dichotomous data of overall response rate (ORR) and occurrence of adverse events (AEs) were calculated by Review Manager 5.3 and Stata 12.0 software.

Results: A total of 12 trials with 5,347 patients were included in this meta-analysis. Compared with the control group, PARP inhibitors significantly improved PFS (HR, 0.51; 95% CI, 0.40–0.65; P < 0.00001) and ORR (RR, 1.26; 95% CI, 1.11–1.43; P = 0.0003). Specifically, PFS was improved regardless of BRCA genes mutations and homologous-recombination status. However, no difference was observed in OS between the PARP inhibitors group and the control group (95% CI, 0.73–1.01; P = 0.06). PARP inhibitors were associated with a statistically significant higher risk of hematologic events and different PARP inhibitors had different toxicities profiles.

Conclusion: PARP inhibitors are an effective and well-tolerated treatment for patients with advanced-stage epithelial ovarian cancer.

Efficacy and Prognostic Factors for PARP Inhibitors in Patients With Ovarian Cancer

Background: The prognostic factors for efficacy of poly(ADP-ribose) polymerase (PARP) inhibitors in ovarian cancer remain unknown. The purpose of this study is to evaluate the efficacy of PARP inhibitors and to explore their prognostic factors in ovarian cancer. Methods: PubMed, Embase, and conference databases were searched for relevant prospective clinical trials. The primary outcomes included overall survival (OS), progression-free survival (PFS), and their prognostic factors. Secondary outcomes included PFS2, time to first subsequent therapy (TFST), time to second subsequent therapy (TSST), chemotherapy-free interval (CFI), and their prognostic factors. Hazard ratio (HR) with a 95% confidence interval (CI) was used as an effect measure. Results: PARP inhibitors significantly prolonged PFS in patients with ovarian cancer regardless of their BRCA and HRD status (HR = 0.44, 95% CI = 0.36-0.55). BRCA mutation, HRD-positive status, and sensitivity to platinum represented effective prognostic factors for PFS (Pinteraction < 0.01 and within-trial interaction HR < 1). Other clinicopathological factors did not predict the benefit of PFS (Pinteraction > 0.10). Moreover, PARP inhibitors significantly increased PFS2, TFST, TSST, and CFI, with significant BRCA-related differences. However, HRD-related differences could not be evaluated due to the lack of eligible studies. Furthermore, PARP inhibitors did not translate into prolonged OS, although there was a benefit associated with OS (HR = 0.84, 95% CI = 0.70-1.02). PARP inhibitors used as maintenance therapy after first or subsequent line therapy improved OS (HR = 0.77, 95% CI = 0.63-0.93). Conclusions: PARP inhibitors can significantly prolong PFS, PFS2, TFST, TSST, and CFI in ovarian cancer patients. BRCA mutation, HRD-positive status, and sensitivity to platinum are effective prognostic factors for the efficacy of PARP inhibitors. However, despite the PFS improvement, this does not translate into prolonged OS for patients.

Incorporating Parp-inhibitors in Primary and Recurrent Ovarian Cancer: A Meta-analysis of 12 phase II/III randomized controlled trials

BACKGROUND

The second decade of 2000s is witnessing a new ovarian cancer (OC) paradigm shift thanks to the results recently obtained by a new class of targeted agents: the Poly(ADP-ribose)polymerase (PARP)-Inhibitors (PARPi). Aim of this meta-analysis is to analyze available results obtained with PARPi, administered alone or in combination with chemo- and/or target-therapies in terms of efficacy and safety for the treatment of recurrent and primary advanced OC.

METHODS

On December 2019, all published phase II/III randomized clinical studies were systematically searched using the terms "[Parp-Inhibitor] AND [ovar*]". Twelve phase II/III randomized controlled trials were identified, with a total number of 5171 patients included.

RESULTS

Results demonstrated that PARPi account for a significant improvement of PFS in both recurrent and primary OC setting, independently from their administration schedule and independently from patients' BRCA mutational status. Moreover, patients harboring a Homologous Recombination Deficiency (HRD) positive testing primary or recurrent OC progress significantly later after PARPi administration/association. Results also reported that PARPi increase the occurrence of severe (G3-G4) anemia. Furthermore, severe fatigue occurred more frequently among patients subjected to PARPi combined with chemotherapy and to PARPi plus Bevacizumab. Finally, a significant increase in severe high blood pressure occurrence was observed when PARPi was added to antiangiogenetics, compared to PARPi alone but a significant decrease in G3-G4 hypertension occurrence was found in PARPi plus bevacizumab users compared to Bevacizumab alone.

CONCLUSIONS

PARPi are a valid option for the treatment of both primary and relapsed OC patients, with a relative low incidence of severe side effects.

Comparison of PARPis with Angiogenesis Inhibitors and Chemotherapy for Maintenance in Ovarian Cancer: A Network Meta-Analysis

INTRODUCTION

Seventy-five percent of ovarian cancer would relapse within 18-28 months after platinum-base chemotherapy. Evidence suggests that maintenance chemotherapy is effective in prolonging remission. Recent target therapies such as poly(ADP-ribose) polymerase inhibitors (PARPis) and angiogenesis inhibitors (AIs) are known to ease burden and recurrence of ovarian cancer. There is limited data for head-to-head comparison of PARPis, AIs, and chemotherapeutic agents (CTAs) as maintenance treatment. This network meta-analysis thus assessed the effectiveness and toxicity of these three maintenance therapies in patients with ovarian cancer.

METHODS

We searched relevant sources (PubMed, EMBASE) to identify randomized controlled trials assessing efficacy and safety of maintenance therapy in patients with ovarian cancer. Primary outcome was progression-free survival (PFS) as assessed by blinded review; safety and tolerability were secondary outcomes. A network meta-analysis to compare three drug classes was performed using statistical software R.

RESULTS

We included 24 trials (11,366 patients) assessing efficacy and safety of PARPis (n = 4), AIs (n = 12), and CTAs (n = 8). PARPis [hazard ratio (HR) 0.64; 95% credible intervals (CrI) 0.55-0.73] and AIs (HR 0.87; 95% CrI 0.81-0.93) showed significant improvement in PFS compared to placebo but not CTA (HR 1.00; 95% CrI 0.86-1.15). PARPis showed significant improvement in PFS compared to AIs (HR 0.73; 95% CrI 0.63-0.86) and CTA (HR 0.64; 95% CrI 0.52-0.78). Adverse events (AEs) leading to treatment discontinuation and dose reduction were lower in PARPis [incidence rate ratio (IRR) 0.60; CrI 0.31-1.18 and IRR 0.73, 95% CrI 0.50-1.06, respectively] compared to AIs, but the differences were not significant.

CONCLUSION

PARPi as maintenance treatment improved PFS in ovarian cancer and was relatively safer in terms of implications caused by AEs when compared to AIs. This network meta-analysis provides valuable evidence and significant insights into treatment of ovarian cancer.

PARP Inhibitors and the Evolving Landscape of Ovarian Cancer Management: A Review

As a drug class, inhibitors of poly-(ADP-ribose) polymerase (PARP) have had their greatest impact on the treatment of women with epithelial ovarian cancers (EOC), in particular, those with the most common histological subtype, high-grade serous cancer, as it has high rates of homologous recombination (HR) deficiency. PARP inhibition exploits this cancer vulnerability by further disrupting DNA repair, thus leading to genomic catastrophe. Early clinical data demonstrated the effectiveness of PARP inhibition in women with recurrent EOC harbouring BRCA1/2 mutations and those with platinum-sensitive recurrences. Three PARP inhibitors (olaparib, niraparib, and rucaparib) are now approved for use in women with recurrent EOC. Based upon randomised controlled trials, PARP inhibitors are in use as "maintenance" therapy for those with platinum-sensitive and platinum-responsive recurrences (irrespective of BRCA1/2 mutation status). Among women with BRCA1/2 mutations (either germline or somatic), maintenance PARP inhibitor therapy for those with recurrence has led to a nearly fourfold prolongation of progression-free survival compared to placebo control. Those without BRCA1/2 mutations experience an approximately twofold increase in progression-free survival. The latest clinical data demonstrate that women with BRCA1/2 mutations who respond to first-line chemotherapy and go on to have maintenance olaparib experience a doubling of the rate of freedom from death at 3 years when compared to placebo (60% vs 27%). PARP inhibitors are also approved as active therapy for women with germline or tumour BRCA1/2 mutations and recurrent EOC treated with three or more prior lines of therapy. Apart from the presence of a BRCA1/2 mutation (germline or somatic) and clinical factors such as platinum sensitivity and responsiveness, other predictive biomarkers are not in routine clinical use. Assays to identify genomic aberrations caused by HR deficiency, or mutations in genes involved in HR, have not been sufficiently sensitive to identify all patients who benefit from treatment. The mechanisms of PARP-inhibitor resistance include restoration of HR through reversion mutations in HR genes, capable of re-establishing the DNA open-reading frame and leading to resumed HR function. Other mechanisms that sustain sufficient DNA repair may also be important. This review focuses on the rationale for the use of PARP inhibitors in EOC. The data that have shaped clinical research are presented, and the trials that have changed management standards are reviewed and discussed. Highlighted are the past and ongoing efforts to further improve and explore the use of PARP inhibitors in EOC.

Maintenance therapy for recurrent epithelial ovarian cancer: current therapies and future perspectives - a review

Epithelial ovarian cancer (EOC) is usually diagnosed late at an advanced stage. Though EOC initially responds to treatment, the recurrence rate is pretty high. The efficacy of different targeted therapies reduces with each recurrence. Hence there is need of effective maintenance therapy in recurrent EOC. Recently, polyADP-ribose polymerase (PARP) inhibitors (PARPi) have been approved both for initial treatment of EOC and as its maintenance treatment. PARPi have also been found to act regardless of BRCA status or homologous recombination (HR) deficiency. Several trials testing PARPi early in maintenance therapy are in progress and their results will shed light on the optimal timing of maintenance therapy that gives the most benefit with least toxicity. Right patient selection for maintenance treatment is also a challenge. Hence, though PARPi are emerging as a promising maintenance treatment in recurrent EOC with prolongation of progression free survival (PFS), results from further trials and overall survival (OS) data from current trials are awaited to fulfill the gaps in understanding the role of this pathway in treatment of EOC. This review discusses the current therapies for EOC, challenges in the treatment of recurrent EOC, recent developments and trials in recurrent EOC maintenance with special focus on PARPi and future perspectives.

Veliparib in ovarian cancer: a new synthetically lethal therapeutic approach

Epithelial ovarian cancer (EOC) accounts for nearly 90% of all ovarian malignancies. The standard therapeutic strategy includes cytoreductive surgery and neo (adjuvant) platinum-based chemotherapy. Relapse of advanced high grade serous ovarian cancer (HGSOC) is related to the development of drug resistance. A defective DNA damage response is a defining hallmark of HGSOC. Poly (ADP-ribose) polymerase (PARP) inhibitors exploit this deficiency through synthetic lethality and have emerged as promising anticancer therapies, especially in breast cancer gene (BRCA1 or BRCA2) mutation carriers. Apart from inducing synthetic lethality, PARP inhibitors have also been shown to trap PARP1 and PARP2 on DNA, leading to PARP-DNA complexes. This "PARP trapping" potentiates synergism between PARP inhibition and both alkylating agents and platinum-based chemotherapy. However, there are remarkable differences in the ability of PARP inhibitors to trap PARP, based on the size and structure of each separate molecule. Since monotherapy with PARP inhibitors is unlikely to induce cancer cell death in BRCA-proficient tumors, the efficacy of PARP inhibitors could be potentially optimized when combined with DNA-damaging agents, or with molecular targeted agents that also impair mechanisms of DNA repair. Olaparib, rucaparib, and niraparib have all obtained US Food and Drug Administration (FDA) and/or European Medicines Agency (EMA) approval in ovarian cancer in different settings. Veliparib does not yet have an approved label; nevertheless, there are currently promising results available in preclinical and early clinical settings. This comprehensive review summarizes the mechanism of action of veliparib and provides an overview of its early and ongoing clinical investigations.

Combined Strategies with Poly (ADP-Ribose) Polymerase (PARP) Inhibitors for the Treatment of Ovarian Cancer: A Literature Review

Poly (ADP-ribose) polymerase (PARP) inhibitors are the first clinically approved drugs designed to exploit synthetic lethality, and were first introduced as a cancer-targeting strategy in 2005. They have led to a major change in the treatment of advanced ovarian cancer, and altered the natural history of a disease with extreme genetic complexity and defective DNA repair via homologous recombination (HR) pathway. Furthermore, additional mechanisms apart from breast related cancer antigens 1 and 2 (BRCA1/2) mutations can also result in HR pathway alterations and consequently lead to a clinical benefit from PARP inhibitors. Novel combinations of PARP inhibitors with other anticancer therapies are challenging, and better understanding of PARP biology, DNA repair mechanisms, and PARP inhibitor mechanisms of action is crucial. It seems that PARP inhibitor and biologic agent combinations appear well tolerated and clinically effective in both BRCA-mutated and wild-type cancers. They target differing aberrant and exploitable pathways in ovarian cancer, and may induce greater DNA damage and HR deficiency. The input of immunotherapy in ovarian cancer is based on the observation that immunosuppressive microenvironments can affect tumour growth, metastasis, and even treatment resistance. Several biologic agents have been studied in combination with PARP inhibitors, including inhibitors of vascular endothelial growth factor (VEGF; bevacizumab, cediranib), and PD-1 or PD-L1 (durvalumab, pembrolizumab, nivolumab), anti-CTLA4 monoclonal antibodies (tremelimumab), mTOR-(vistusertib), AKT-(capivasertib), and PI3K inhibitors (buparlisib, alpelisib), as well as MEK 1/2, and WEE1 inhibitors (selumetinib and adavosertib, respectively). Olaparib and veliparib have also been combined with chemotherapy with the rationale of disrupting base excision repair via PARP inhibition. Olaparib has been investigated with carboplatin and paclitaxel, whereas veliparib has been tested additionally in combination with temozolomide vs. pegylated liposomal doxorubicin, as well as with oral cyclophosphamide, and topoisomerase inhibitors. However, overlapping myelosuppression observed with PARP inhibitor and chemotherapy combinations requires further investigation with dose escalation studies. In this review, we discuss multiple clinical trials that are underway examining the antitumor activity of such combination strategies.