Characterization of Absorption, Metabolism, and Elimination of Niraparib, an Investigational Poly (ADP-Ribose) Polymerase Inhibitor, in Cancer Patients

Comparison of Adverse Events Between PARP Inhibitors in Patients with Epithelial Ovarian Cancer: A Nationwide Propensity Score Matched Cohort Study

BACKGROUND

Despite improvement in progression-free survival (PFS) with poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) as maintenance treatment for patients with epithelial ovarian cancer (EOC), a comparative analysis of clinical events of interest (CEIs) of different PARPi is scarce.

OBJECTIVE

This study aimed to compare the safety of different PARPi in patients with EOC.

PATIENTS AND METHODS

Through analyzing the Korean National Health Insurance Service from January 2009 to January 2022, this study involved BRCA-mutated, platinum-sensitive patients with EOC treated with olaparib (tablet), niraparib, and olaparib (capsule) as first-line or second-line maintenance treatment. CEIs were identified using International Statistical Classification of Diseases (ICD) 9/10 codes, with additional outcomes being dose modification and persistence.

RESULTS

In the first-line maintenance treatment [118 niraparib, 104 olaparib (tablet) patients], no significant differences were noted in CEIs, dose reduction, or 6-month discontinuation rate. For second-line maintenance treatment [303 niraparib, 126 olaparib (tablet), and 675 olaparib (capsule) patients], niraparib was associated with a higher risk of hematologic CEIs, particularly anemia, compared with olaparib (tablet) (0.51 [0.26-0.98] and 0.09 [0.01-0.74], respectively), and higher rate of discontinuation rate at 6 months. Of note, patients over 60 years old showed an increased risk of CEIs with niraparib, as indicated by the hazard ratio divergence in restricted cubic spline plots.

CONCLUSIONS

No differences were observed among the PARPi during first-line maintenance treatment. However, in the second-line maintenance treatment, significant differences were observed in the risk of experiencing CEIs, dose alteration possibilities, and discontinuation of PARPi between niraparib and olaparib (tablets). Moreover, our findings suggest that an age of 60 years may be a critical factor in selecting PARPi to reduce CEI incidence.

Safety of PARP inhibitors as maintenance therapy in ovarian cancer

INTRODUCTION

Antiangiogenic agents and poly(ADP-ribose) polymerase inhibitors (PARP-Is) have improved the outcome of patients suffering from ovarian cancer. However, as they are associated with many adverse events (AEs), it is important to be aware of their safety and toxicity profiles.

AREAS COVERED

We reviewed PARP-I therapeutical indications, mechanism of action, metabolism, and interactions. We reported on all major and minor AEs that have emerged from clinical trials (SOLO1, PRIMA, PAOLA1, ATHENA, SOLO2, NOVA, ARIEL3, NORA), their follow-ups, meta-analyses, and real-world studies, particularly hematologic toxicities and their management, and secondary malignancies (myelodysplastic syndrome and acute myeloid leukemia). We also addressed gastrointestinal, neurological, respiratory, hepatic, and renal toxicity and the use of PARP-Is in older, pregnant, and lactating patients. No specific research strategy in terms of keywords, inclusive dates and databases was used.

EXPERT OPINION

PARP-Is benefits largely outweigh the risks associated with potential AEs. Randomized controlled trials produced strong good, quality data, but they enrolled a selected population and failed to capture rare events. More pharmacovigilance data and real-life studies on a larger and more heterogeneous sample are needed to understand PARP-Is differences and to clarify the incidence of late AEs to balance the risk/benefit ratio.

P-Glycoprotein (ABCB1/MDR1) Controls Brain Penetration and Intestinal Disposition of the PARP1/2 Inhibitor Niraparib

Niraparib (Zejula), a selective oral PARP1/2 inhibitor registered for ovarian, fallopian tube, and primary peritoneal cancer treatment, is under investigation for other malignancies, including brain tumors. We explored the impact of the ABCB1 and ABCG2 multidrug efflux transporters, the OATP1A/1B uptake transporters, and the CYP3A drug-metabolizing complex on oral niraparib pharmacokinetics, using wild-type and genetically modified mouse and cell line models. In vitro, human ABCB1 and mouse Abcg2 transported niraparib moderately. Compared to wild-type mice, niraparib brain-to-plasma ratios were 6- to 7-fold increased in Abcb1a/1b^-/- and Abcb1a/1b;Abcg2^-/- but not in single Abcg2^-/- mice, while niraparib plasma exposure at later time points was ∼2-fold increased. Niraparib recovery in the small intestinal content was markedly reduced in the Abcb1a/1b-deficient strains. Pretreatment of wild-type mice with oral elacridar, an ABCB1/ABCG2 inhibitor, increased niraparib brain concentration and reduced small intestinal content recovery to levels observed in Abcb1a/1b;Abcg2^-/- mice. Oatp1a/1b deletion did not significantly affect niraparib oral bioavailability or liver distribution but decreased metabolite M1 liver uptake. No significant effects of mouse Cyp3a ablation were observed, but overexpression of transgenic human CYP3A4 unexpectedly increased niraparib plasma exposure. Thus, Abcb1 deficiency markedly increased niraparib brain distribution and reduced its small intestinal content recovery, presumably through reduced biliary excretion and/or decreased direct intestinal excretion. Elacridar pretreatment inhibited both processes completely. Clinically, the negligible role of OATP1 and CYP3A could be advantageous for niraparib, diminishing drug-drug interaction or interindividual variation risks involving these proteins. These findings may support the further clinical development and application of niraparib.

Update on Poly ADP-Ribose Polymerase Inhibitors in Ovarian Cancer With Non-BRCA Mutations

Poly ADP-ribose polymerase inhibitor (PARPi) has become an important maintenance therapy for ovarian cancer after surgery and cytotoxic chemotherapy, which has changed the disease management model of ovarian cancer, greatly decreased the risk of recurrence, and made the prognosis of ovarian cancer better to certain extent. The three PARPis currently approved by the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of ovarian cancer are Olaparib, Niraparib and Rucaparib. With the incremental results from new clinical trials, the applicable population of PARPi for ovarian cancer have expanded to population with non-BRCA mutations. Although BRCA mutated population are still the main beneficiaries of PARPi, recent clinical trials indicated PARPis' therapeutic potential in non-BRCA mutated population, especially in homologous recombination repair deficiency (HRD) positive population. However, lack of unified HRD status detection method poses a challenge for the accurate selection of PARPi beneficiaries. The reversal of homologous recombination (HR) function during the treatment will not only cause resistance to PARPis, but also reduce the accuracy of the current method to determine HRD status. Therefore, the development of reliable HRD status detection methods to determine the beneficiary population, as well as rational combination treatment are warranted. This review mainly summarizes the latest clinical trial results and combination treatment of PARPis in ovarian cancer with non-BRCA mutations, and discusses the application prospects, including optimizing combination therapy against drug resistance, developing unified and accurate HRD status detection methods for patient selection and stratification. This review further poses an interesting topic: the efficacy and safety in patients retreated with PARPis after previous PARPi treatment---"PARPi after PARPi".

The evolving role of PARP inhibitors in advanced ovarian cancer

The field of ovarian cancer has been revolutionized with the use of poly (ADP-ribose) polymerase (PARP) inhibitors, which present greater inhibition effect in epithelial subtype due to high rates of homologous recombination deficiency. PARP inhibition exploits this cancer pitfall by disrupting DNA repair, leading to genomic instability and apoptosis. Three PARP inhibitors (olaparib, niraparib, and rucaparib) are now approved for use in women with epithelial ovarian cancer, while others are under development. Among women with BRCA1/2 mutations, maintenance PARP therapy has led to a nearly fourfold prolongation of PFS, while those without BRCA1/2 mutations experience an approximately twofold increase in PFS. Differences in trial design, patient selection and primary analysis population affect the conclusions on PARP inhibitors. Limited OS data have been published and there is also limited experience regarding long-term safety. With regard to toxicity profile, there are no differences in serious adverse events between the experimental and control groups. However, combining adverse event data from maintenance phases, a trend towards more events in the experimental group, compared with controls, has been shown. The mechanisms of PARP-inhibitor resistance include restoration of HR through reversion mutations in HR genes, leading to resumed HR function. Other mechanisms that sustain sufficient DNA repair are discussed as well. PARP inhibitors play a pivotal role in the management of ovarian cancer, affecting the future treatment choices. Defining exactly which patients will benefit from them is a challenge and the need for HRD testing to define ‘BRCA-ness’ will add additional costs to treatment.

Niraparib in the maintenance treatment of advanced epithelial ovarian, fallopian tube, or primary peritoneal cancer: safety and efficacy

Introduction: Approximately 300,000 women worldwide are diagnosed each year with ovarian cancer. Frequently diagnosed in late stages with ambiguous symptomatology, ovarian cancer has a low survival rate.Areas covered: Niraparib, a PARP inhibitor, was approved in 2020 for use in the maintenance treatment of ovarian cancer regardless of biomarker status. Included in the review are PRIMA (NCT02655016), NOVA (NCT01847274), AVANOVA2 (NCT02354131), and QUADRA (NCT02354586) trials which herald the advent of using maintenance oral therapies in the treatment of ovarian cancer. Additionally, with new combination drug trials, exciting avenues for treatment are also discussed with the FIRST (NCT03016338) trial.Expert opinion: Maintenance niraparib treatment regardless of genetic profile offers a new modality for the treatment of ovarian cancer with a low side effect profile and importantly oral dosing. New combinations of synergistic immunotherapeutics, and antiangiogenesis therapies with niraparib also offer exciting new frontiers for patients with ovarian cancer.

Niraparib: A Review in Ovarian Cancer

Niraparib (Zejula^®), a poly (ADP-ribose) polymerase (PARP) inhibitor, is approved for the maintenance treatment of recurrent, epithelial ovarian, fallopian tube, or primary peritoneal cancer in patients who are in complete or partial response to platinum-based chemotherapy. Approval was based on the results of the randomized, double-blind, placebo-controlled phase III NOVA trial. In NOVA, niraparib significantly prolonged progression-free survival (primary endpoint), chemotherapy-free interval and time to first subsequent therapy compared with placebo in patients with recurrent, platinum-sensitive, high grade serous ovarian, fallopian tube or primary peritoneal cancer. The beneficial effects of niraparib were consistent regardless of BRCA mutation or homologous recombination deficiency (HRD) status. Niraparib had a manageable tolerability profile, with the majority of grade 3 or 4 adverse events being haematologic abnormalities (e.g. thrombocytopenia, anaemia, neutropenia). Adverse events were generally well managed with dose interruption or modification of niraparib. Current evidence suggests that niraparib is an effective new option with a manageable tolerability profile for the maintenance treatment of recurrent, platinum-sensitive epithelial ovarian, fallopian tube, or primary peritoneal cancer in adults, with or without BRCA1/2 mutation or HRD.

Exploring and comparing adverse events between PARP inhibitors

Ovarian cancer remains one of the most challenging malignancies to treat. Targeted therapies such as poly (ADP-ribose) polymerase (PARP) inhibitors have emerged as one of the most exciting new treatments for ovarian cancer, particularly in women with BRCA1 or BRCA2 mutations or those without a functional homologous recombination repair pathway. Perhaps the most advantageous characteristic of PARP inhibitors is their mechanism of action, which targets cancer cells on the basis of their inherent deficiencies while seemingly avoiding normally functioning cells. Although health-care providers might assume a low toxicity profile because of their specific mechanism of action, PARP inhibitors are not completely benign and overall show a class effect adverse-event profile. Further complicating this situation, three different PARP inhibitors have been approved by the US Food and Drug Administration since 2014, each with their own specific indications and individual toxicity profiles. The diversity of adverse events seen both within and across this class of drug underscores the importance of having a comprehensive reference to help guide clinical decision making when treating patients. This Review characterises and compares all toxicities associated with each PARP inhibitor, both in monotherapy and in novel combinations with other drugs, with a particular focus on potential management strategies to help mitigate toxic effects. Although the excitement surrounding PARP inhibitors might certainly be warranted, a thorough understanding of all associated toxicities is imperative to ensure that patients can achieve maximal clinical benefit.

PARP inhibitors as potential therapeutic agents for various cancers: focus on niraparib and its first global approval for maintenance therapy of gynecologic cancers

Poly (ADP-ribose) polymerases (PARPs) are an important family of nucleoproteins highly implicated in DNA damage repair. Among the PARP families, the most studied are PARP1, PARP2 and PARP 3. PARP1 is found to be the most abundant nuclear enzyme under the PARP series. These enzymes are primarily involved in base excision repair as one of the major single strand break (SSB) repair mechanisms. Being double stranded, DNA engages itself in reparation of a sub-lethal SSB with the aid of PARP. Moreover, by having a sister chromatid, DNA can also repair double strand breaks with either error-free homologous recombination or error-prone non-homologous end-joining. For effective homologous recombination repair, DNA requires functional heterozygous breast cancer genes (BRCA) which encode BRCA1/2. Currently, the development of PARP inhibitors has been one of the promising breakthroughs for cancer chemotherapy. In March 2017, the United States Food and Drug Administration (FDA) approved niraparib for maintenance therapy of recurrent gynecologic cancers (epithelial ovarian, primary peritoneal and fallopian tube carcinomas) which are sensitive to previous platinum based chemotherapy irrespective of BRCA mutation and homologous recombination deficiency status. It is the third drug in this class to receive FDA approval, following olaparib and rucaparib and is the first global approval for maintenance therapy of the aforementioned cancers. Niraparib preferentially blocks both PARP1 and PARP2 enzymes. The daily tolerated dose of niraparib is 300 mg, above which dose limiting grade 3 and 4 toxicities were observed. In combination with humanized antibody, pembrolizumab, it is also under investigation for those patients who have triple negative breast cancer. By and large, there are several clinical trials that are underway investigating clinical efficacy and safety, as well as other pharmacokinetic and pharmacodynamic profiles of this drug for various malignancies.