Treatment with olaparib monotherapy in the maintenance setting significantly improves progression-free survival in patients with platinum-sensitive relapsed ovarian cancer: Results from the phase III SOLO2 study

The power and the promise of synthetic lethality for clinical application in cancer treatment

Synthetic lethality is a phenomenon wherein the simultaneous deficiency of two or more genes results in cell death, while the deficiency of any individual gene does not lead to cell death. In recent years, synthetic lethality has emerged as a significant topic in the field of targeted cancer therapy, with certain drugs based on this concept exhibiting promising outcomes in clinical trials. Nevertheless, the presence of tumor heterogeneity and the intricate DNA repair mechanisms pose challenges to the effective implementation of synthetic lethality. This review aims to explore the concepts, development, and ethical quandaries surrounding synthetic lethality. Additionally, it will provide an in-depth analysis of the clinical application and underlying mechanism of synthetic lethality.

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.

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.

MicroRNA-506-3p increases the response to PARP inhibitors and cisplatin by targeting EZH2/β-catenin in serous ovarian cancers

Chemo-resistance is an important barrier to effective treatment of ovarian cancer. Poly (ADP-ribose) polymerase (PARP) inhibitors are currently promising targeted drugs used to treat BRCA-mutant ovarian cancer. Ovarian cancer patients with BRCA 1/2 mutations appear to benefit better from PARP inhibitors and chemotherapy. Understanding the mechanisms underlying PARP inhibitors and chemotherapy resistance is urgently needed. There is increasing evidence that microRNAs (miRNAs) are involved in drug resistance. MiR-506-3p is an effective inhibitor of the epithelial-to-mesenchymal transition (EMT), and can enhance chemotherapy and olaparib response in high-grade serous ovarian cancer (HGS-OvCa). Enhancer of Zeste Homolog 2 (EZH2) is considered as a direct target of miR-506-3p. The silencing of EZH2 mimics the inhibitory effects of miR-506-3p on chemo-resistance and olaparib response. Rescue of EZH2 prevented the functions of miR-506-3p. Moreover, EZH2 activates the β-catenin pathway. MiR-506-3p overexpression decreased the level of β-catenin, and the sensitivity to olaparib and cisplatin mediated by miR-506-3p was partially reversed by regulating β-catenin expression in ovarian cancer. Our results suggest that miR-506-3p increases response to PARP inhibitors and cisplatin in serous ovarian cancer by targeting EZH2/β-catenin signal pathway, which opens the possibility of using miR-506-3p overexpression as a potential therapeutic for ovarian cancer.

Integration of PARP-inhibitors in ovarian cancer therapy

Poly-ADP-ribose polymerase inhibitors (PARP-I) represent one of the most attractive and promising class of biological agents studied both in relapsed ovarian cancer (OC) and in the advanced setting. The availability of this new class of drugs has changed the clinical management of OC ensuring an unprecedented advance in such an aggressive cancer. Three oral PARP-I are currently available: olaparib, niraparib and rucaparib. Another two are in active clinical exploration: veliparib and talazoparib. Here the authors report clinical data with PARP-I with a particular emphasis on the phase II and III trials that support PARP-I approval by regulatory agencies in OC patients.

Evaluation and management of toxicity of cytoreductive surgery/hyperthermic intraperitoneal chemotherapy: the initial experience of a single centre study

BACKGROUND

Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) is a treatment modality for peritoneal surface malignancies with efficacy reported in many trials. Discrepancies, however, in the indication criteria, the extent of the surgical procedure, HIPEC regimens and toxicity evaluation represent a problem when comparing this method with other therapeutic modalities.

METHODS

We describe the initial experience with CRS/HIPEC using different chemotherapy regimens (oxaliplatin, cisplatin, mitomycin C and doxorubicin) at the Comprehensive Oncology Centre Olomouc.

RESULTS

A perioperative mortality of 2% and perioperative morbidity of 11%, according to Clavien-Dindo were observed. Interestingly, all these patients underwent HIPEC with oxaliplatin 460 mg/m². The median duration of admission to hospital was 6 days in the intensive care unit (range 2-28 days) and 7 days in the surgical ward (range 1-21 days). Hospital admission did not exceed 2 weeks in 75% of patients. These results are consistent with the published results of large centres performing this treatment modality mainly due to pre-operative preparation of patients and pre-treatment and post-treatment management of HIPEC/CRS toxicity. Evaluation of the efficacy in terms of time to progression and overall survival (OS) is limited by the short follow up period.

CONCLUSION

CRS/HIPEC performed is a safe method with low perioperative mortality.

Advances in the use of PARP inhibitors for BRCA1/2-associated breast cancer: talazoparib

Poly-ADP-ribosyl polymerase (PARP) enzymes PARP-1 and PARP-2 recognize DNA damage and set off a cascade of cellular mechanisms required for multiple types of DNA damage repair. PARP inhibitors are small molecule mimetics of nicotinamide which bind to PARP’s catalytic domain to inhibit poly-ADP-ribosylation (PARylation) of target proteins, including PARP-1 itself. PARP inhibitors olaparib, veliparib, talazoparib, niraparib and rucaparib have predominantly been studied in women with breast or ovarian cancers associated with deleterious germline mutations in BRCA1 and BRCA2 (gBRCA1/2+). The BRCA1 and BRCA2 proteins are involved in DNA repair by homologous recombination. This review will focus on talazoparib, a PARP inhibitor approved by the US FDA for the treatment of metastatic gBRCA1/2+ breast cancers in October 2018.

Germline and Somatic Tumor Testing in Gynecologic Cancer Care

New technologies have advanced the science of tumor biology and genomics. Commercially available germline and somatic testing modalities have the downstream benefits of enabling prevention strategies in women with hereditary cancers and their family members in addition to identifying women who benefit most from novel targeted therapeutics. The matrix of available testing is complex and evolving. Women's health providers need to be versed in benefits and limitations of available testing. Genetic counselors play a pivotal role in interpretation of relevant mutations, and in avoiding common pitfalls, but their skill set is not sufficient to optimally integrate cancer genomics into clinical practice.

Maintenance treatment of recurrent ovarian cancer: Is it ready for prime time?

Approximately 1% of women in the United States will be diagnosed with epithelial ovarian cancer (EOC) during their lifetime. It is most likely to present at a more advanced stage, requiring aggressive therapeutic measures, and most women will succumb to this illness. Due to advancements in therapy, the oncology community has begun to shift its focus to molecular targeted agents, alternative dosing schedules, and maintenance therapy. Women who achieve a response to initial adjuvant chemotherapy may be candidates for maintenance therapy, with the goal of inducing a lasting remission or prolonging the disease-free interval before recurrence. The rationale for maintenance therapy is to delay disease progression by eliminating residual, slowly-dying cancerous cells, or impeding cell turnover. This review discusses the goals of maintenance therapy for EOC with antiangiogenic agents or poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors, and reviews clinical studies that have demonstrated improvements in survival outcomes. The side-effect profiles for PARP inhibitors and the implications for preserving quality of life during maintenance therapy will also be discussed.

[Recommendations for biomarker testing in epithelial ovarian cancer. A national consensus statement by the Spanish Society of Pathology and the Spanish Society of Medical Oncology]

Advances in the understanding of the histological and molecular characteristics of ovarian cancer now allow 5subtypes to be identified, leading to a more refined therapeutic approach and improved clinical trials. Each of the subtypes has specific histological features and a particular biomarker expression, as well as mutations in different genes, some of which have prognostic and predictive value. CA125 and HE4 are examples of ovarian cancer biomarkers used in diagnosis and follow-up. Currently, somatic or germinal mutations on BRCA1 and BRCA2 genes are the most important biomarkers in epithelial ovarian cancer, having prognostic and predictive value. In this article, a group of experts from the Spanish Society of Medical Oncology and the Spanish Society of Pathology review the histological and molecular characteristics of the 5subtypes of ovarian cancer and describe the most useful biomarkers and mutations for diagnosis, screening and tailored treatment strategy.

Drug development in the era of precision medicine

For the past three decades, the use of genomics to inform drug discovery and development pipelines has generated both excitement and scepticism. Although earlier efforts successfully identified some new drug targets, the overall clinical efficacy of developed drugs has remained unimpressive, owing in large part to the heterogeneous causes of disease. Recent technological and analytical advances in genomics, however, have now made it possible to rapidly identify and interpret the genetic variation underlying a single patient's disease, thereby providing a window into patient-specific mechanisms that cause or contribute to disease, which could ultimately enable the 'precise' targeting of these mechanisms. Here, we first examine and highlight the successes and limitations of the earlier phases of genomics in drug discovery and development. We then review the current major efforts in precision medicine and discuss the potential broader utility of mechanistically guided treatments going forward.

Advances in ovarian cancer therapy

Epithelial ovarian cancer is typically diagnosed at an advanced stage. Current state-of-the-art surgery and chemotherapy result in the high incidence of complete remissions; however, the recurrence rate is also high. For most patients, the disease eventually becomes a continuum of symptom-free periods and recurrence episodes. Different targeted treatment approaches and biological drugs, currently under development, bring the promise of turning ovarian cancer into a manageable chronic disease. In this review, we discuss the current standard in the therapy for ovarian cancer, major recent studies on the new variants of conventional therapies, and new therapeutic approaches, recently approved and/or in clinical trials. The latter include anti-angiogenic therapies, polyADP-ribose polymerase (PARP) inhibitors, inhibitors of growth factor signaling, or folate receptor inhibitors, as well as several immunotherapeutic approaches. We also discuss cost-effectiveness of some novel therapies and the issue of better selection of patients for personalized treatment.

Recommendations for biomarker testing in epithelial ovarian cancer: a National Consensus Statement by the Spanish Society of Pathology and the Spanish Society of Medical Oncology

Because of advances in the understanding of histological and molecular characteristics in ovarian cancer, it is now possible to recognize the existence of five subtypes, which in turn has allowed a more refined therapeutic approach and better design of clinical trials. Each of these five subtypes has specific histological features and a particular biomarker expression, as well as mutations in different genes, some of which have prognostic and predictive value. CA125 and HE4 are examples of ovarian cancer biomarkers used in the diagnosis and follow-up of these malignancies. Currently, somatic or germinal mutations on BRCA1 and BRCA2 genes are the most important biomarkers in epithelial ovarian cancer having prognostic and predictive value. This article will review the histological and molecular characteristics of the five subtypes of ovarian cancer, describing the most important biomarkers and mutations that can guide in diagnosis, screening and tailored treatment strategy.