Pharmacotherapeutic group: other antineoplastic agents, ATC code: L01XK02.
Mechanism of action and pharmacodynamic effects
Niraparib is an inhibitor of poly(ADP‑ribose) polymerase (PARP) enzymes, PARP‑1 and PARP‑2, which play a role in DNA repair. In vitro studies have shown that niraparib‑induced cytotoxicity may involve inhibition of PARP enzymatic activity and increased formation of PARP‑DNA complexes resulting in DNA damage, apoptosis and cell death. Increased niraparib‑induced cytotoxicity was observed in tumour cell lines with or without deficiencies in the BReast CAncer (BRCA) 1 and 2 tumour suppressor genes. In orthotopic high‑grade serous ovarian cancer patient-derived xenograft tumours (PDX) grown in mice, niraparib has been shown to reduce tumour growth in BRCA 1 and 2 mutant, BRCA wild-type but homologous recombination (HR) deficient, and in tumours that are BRCA wild-type and without detectable HR deficiency.
Clinical efficacy and safety
First-line ovarian cancer maintenance treatment
PRIMA was a Phase 3 double-blind, placebo-controlled trial in which patients (n = 733) in complete or partial response to first-line platinum-based chemotherapy were randomised 2:1 to Zejula or matched placebo. PRIMA was initiated with a starting dose of 300 mg daily in 475 patients (whereof 317 was randomised to the niraparib arm vs 158 in the placebo arm) in continuous 28-day cycles. The starting dose in PRIMA was changed with Amendment 2 of the Protocol. From that point forward, patients with a baseline body weight ≥77 kg and baseline platelet count ≥150,000/µL were administered Zejula 300 mg (n = 34) or placebo daily (n = 21) while patients with a baseline body weight <77 kg or baseline platelet count <150,000/μL were administered Zejula 200 mg (n = 122) or placebo daily (n = 61).
Patients were randomised post completion of first-line platinum-based chemotherapy plus or minus surgery. Subjects were randomized within 12 weeks of the first day of the last cycle of chemotherapy.
Subjects had ≥6 and ≤9 cycles of platinum-based therapy. Following interval debulking surgery subjects had ≥2 post-operative cycles of platinum-based therapy. Patients who had received bevacizumab with chemotherapy but could not receive bevacizumab as maintenance therapy were not excluded from the study. Patients could not have received prior PARP inhibitor (PARPi) therapy, including Zejula. Patients who had neoadjuvant chemotherapy followed by interval debulking surgery could have visible residual or no residual disease. Patients with Stage III disease who had complete cytoreduction (i.e., no visible residual disease) after primary debulking surgery were excluded. Randomisation was stratified by best response during the front-line platinum regimen (complete response vs partial response), neoadjuvant chemotherapy (NACT) (Yes vs No); and homologous recombination deficiency (HRD) status [positive (HR-deficient) vs negative (HR-proficient) or not determined]. Testing for HRD was performed using the HRD test on tumour tissue obtained at the time of initial diagnosis. The CA-125 levels should be in the normal range (or a CA-125 decrease by > 90 %) during the patient's front-line therapy, and be stable for at least 7 days.
Patients began treatment on Cycle 1/Day 1 (C1/D1) with Zejula 200 or 300 mg or matched placebo administered daily in continuous 28‑day cycles. Clinic visits occurred each cycle (4 weeks ± 3 days).
The primary endpoint was progression-free survival (PFS), as determined by blinded independent central review (BICR) per RECIST, version 1.1. PFS testing was performed hierarchically: first in the HR deficient population, then in the overall population. Secondary efficacy endpoints included PFS after the first subsequent therapy (PFS2) and overall survival (OS) (Table 5). The median age was 62 years among patients randomised to Zejula (range 32 to 85 years) or placebo (range 33 to 88 years). Eighty-nine percent of all patients were white. Sixty-nine percent of patients randomised to Zejula and 71% of patients randomised to placebo had an ECOG of 0 at study baseline. In the overall population, 65% of patients had stage III disease and 35% had stage IV disease. In the overall population, the primary tumour site in most patients (≥ 80%) was the ovary; most patients (> 90%) had tumours with serous histology. Sixty-seven percent of patients received NACT. Sixty-nine percent of patients had a complete response to the first-line platinum-based chemotherapy. A total of 6 patients in the Zejula group had received bevacizumab as prior treatment for their ovarian cancer.
PRIMA demonstrated a statistically significant improvement in PFS for patients randomised to Zejula as compared with placebo in the HR-deficient and overall population (Table 5, and Figures 1 and 2). Efficacy results for the final analysis of OS data are presented in Table 5.
Table 5: Efficacy results – PRIMA
| | HR-deficient population | Overall population |
| Zejula (N=247) | Placebo (N=126) | Zejula (N=487) | Placebo (N=246) |
| Primary endpoint (determined by BICR) | |
| PFS median, months (95% CI) | 21.9 (19.3, NE) | 10.4 (8.1, 12.1) | 13.8 (11.5, 14.9) | 8.2 (7.3, 8.5) |
| Hazard ratio (95% CI) | 0.43 (0.31, 0.59) | 0.62 (0.50, 0.76) |
| p-value | <0.0001 | <0.0001 |
| Secondary endpointsa, b, c |
| PFS2 median, months (95% CI) | 43.4 (37.2, 54.1) | 39.3 (30.3, 55.7) | 30.1 (27.1, 33.1) | 27.6 (24.2, 33.1) |
| Hazard ratio (95% CI) | 0.87 (0.66, 1.17) | 0.96 (0.79, 1.17) |
| OS median, monthsd (95% CI) | 71.9 (55.5, NE) | 69.8 (51.6, NE) | 46.6 (43.7, 52.8) | 48.8 (43.1, 61.0) |
| Hazard ratio (95% CI) | 0.95 (0.70, 1.29) | 1.01 (0.84, 1.23) |
PFS = progression-free survival; CI = confidence interval; NE = not evaluable; PFS2 = PFS after the first subsequent therapy; OS = Overall survival.
a Data based on final analysis.
b In the HR-deficient population and overall population, 15.8% and 11.7% of patients in the Zejula arm received subsequent PARPi therapy, respectively.
c In the HR-deficient population and overall population, 48.4% and 37.8% of placebo patients received subsequent PARPi therapy, respectively.
d The maturity of the OS data for the HR-deficient population and overall population was 49.6% and 62.5%, respectively.
Figure 1: Progression‑free survival in the HR-deficient population – PRIMA (ITT)
Figure 2: Progression-free survival in the overall population - PRIMA (ITT)
PFS subgroup analyses
Within the HR-deficient population, a PFS hazard ratio of 0.40 (95% 'CI' 0.27, 0.62) was observed in the subgroup of patients with BRCA mutation ovarian cancer (n = 223). In the subgroup of HR-deficient patients without a BRCA mutation (n = 150), a hazard ratio of 0.50 (95% CI: 0.31, 0.83) was observed.
The median PFS in the HR-proficient population (n = 249) was 8.1 months for patients randomised to Zejula compared with 5.4 months for placebo with a hazard ratio of 0.68 (95% CI: 0.49, 0.94).
In exploratory subgroup analyses of patients who were administered 200 or 300 mg dose of Zejula based on baseline weight or platelet count, comparable efficacy (investigator-assessed PFS) was observed with a PFS hazard ratio of 0.54 (95% 'CI' 0.33, 0.91) in the HR-deficient population, and with a hazard ratio of 0.68 (95% 'CI' 0.49, 0.94) in the overall population. In the HR-proficient subgroup, the dose of 200 mg appeared to give a lower treatment effect compared to the 300 mg dose.
OS subgroup analyses
In the subgroup of HR-deficient patients with BRCA mutation ovarian cancer (n = 223), an OS hazard ratio of 0.94 (95% CI: 0.63, 1.41) was observed. In the subgroup of HR-deficient patients without a BRCA mutation (n = 149), a hazard ratio of 0.97 (95% CI: 0.62, 1.53) was observed.
The median OS in the HR-proficient population (n = 249) was 36.6 months for patients randomised to Zejula compared to 32.2 months in the placebo arm, with a hazard ratio of 0.93 (95% CI: 0.69, 1.26).
Platinum-sensitive recurrent ovarian cancer maintenance treatment
The safety and efficacy of niraparib as maintenance therapy was studied in a Phase 3 randomised, double‑blind, placebo‑controlled international trial (NOVA) in patients with relapsed predominantly high grade serous epithelial ovarian, fallopian tube, or primary peritoneal cancer who were platinum sensitive, defined by complete response (CR) or partial response (PR) for more than six months to their penultimate (next to last) platinum‑based therapy. To be eligible for niraparib treatment, the patient should be in response (CR or PR) following completion of last platinum-based chemotherapy. The CA‑125 levels should be normal (or a > 90% decrease in CA‑125 from baseline) following their last platinum treatment, and be stable for at least 7 days. Patients could not have received prior PARPi therapy, including Zejula. Eligible patients were assigned to one of two cohorts based on the results of a germline BRCA (gBRCA) mutation test. Within each cohort, patients were randomised using a 2:1 allocation of niraparib and placebo. Patients were assigned to the gBRCAmut cohort based on blood samples for gBRCA analysis that were taken prior to randomisation. Testing for tumour BRCA (tBRCA) mutation and HRD was performed using the HRD test on tumour tissue obtained at the time of initial diagnosis or at the time of recurrence.
Randomisation within each cohort was stratified by time to progression after the penultimate platinum therapy before study enrolment (6 to < 12 months and ≥ 12 months); use or not of bevacizumab in conjunction with the penultimate or last platinum regimen; and best response during the most recent platinum regimen (complete response and partial response).
Patients began treatment on Cycle 1/Day 1 (C1/D1) with niraparib 300 mg or matched placebo administered daily in continuous 28‑day cycles. Clinic visits occurred each cycle (4 weeks ± 3 days).
In the NOVA study, 48 % of patients had a dose interruption in Cycle 1. Approximately 47% of patients restarted at a reduced dose in Cycle 2.
The most commonly used dose in niraparib‑treated patients in the NOVA study was 200 mg.
Progression‑free survival (PFS) was determined per RECIST (Response Evaluation Criteria in Solid Tumors, version 1.1) or clinical signs and symptoms and increased CA‑125. PFS was measured from the time of randomisation (which occurred up to 8 weeks after completion of the chemotherapy regimen) to disease progression or death.
The primary efficacy analysis for PFS was determined by blinded central independent assessment and was prospectively defined and assessed for the gBRCAmut cohort and the non‑gBRCAmut cohort separately. Overall survival (OS) analyses were secondary outcome measures.
Secondary efficacy endpoints included chemotherapy‑free interval (CFI), time to first subsequent therapy (TFST), PFS after the first subsequent therapy (PFS2), and OS.
Demographics, baseline disease characteristics, and prior treatment history were generally well balanced between the niraparib and placebo arms in the gBRCAmut (n = 203) and the non‑gBRCAmut cohorts (n = 350). Median ages ranged from 57 to 63 years across treatments and cohorts. The primary tumour site in most patients (> 80%) within each cohort was the ovary; most patients (> 84%) had tumours with serous histology. A high proportion of patients in both treatment arms in both cohorts had received 3 or more prior lines of chemotherapy, including 49 % and 34 % of niraparib patients in the gBRCAmut and non‑gBRCAmut cohorts, respectively. Most patients were age 18 to 64 years (78%), Caucasian (86%) and had an ECOG performance status of 0 (68%).
In the gBRCAmut cohort, the median number of treatment cycles was higher in the niraparib arm than the placebo arm (14 and 7 cycles, respectively). More patients in the niraparib group continued treatment for more than 12 months than patients in the placebo group (54.4% and 16.9% respectively).
In the overall non‑gBRCAmut cohort, the median number of treatment cycles was higher in the niraparib arm than in the placebo arm (8 and 5 cycles, respectively). More patients in the niraparib group continued treatment for more than 12 months than patients in the placebo group (34.2% and 21.1%, respectively).
The study met its primary objective of statistically significantly improved PFS for niraparib maintenance monotherapy compared with placebo in the gBRCAmut cohort as well as in the overall non‑gBRCAmut cohort. Table 6 and Figures 3 and 4 show the results for the PFS primary endpoint for the primary efficacy populations (gBRCAmut cohort and the overall non‑gBRCAmut cohort).
Table 6: Summary of primary objective outcomes in the NOVA study
| | gBRCAmut cohort | Non‑gBRCAmut cohort |
| Zejula (N = 138) | Placebo (N = 65) | Zejula (N = 234) | Placebo (N = 116) |
| PFS median (95% CI) | 21.0 (12.9, NE) | 5.5 (3.8, 7.2) | 9.3 (7.2, 11.2) | 3.9 (3.7, 5.5) |
| p‑value | < 0.0001 | < 0.0001 |
| Hazard ratio (Zejula:placebo) (95% CI) | 0.27 (0.173, 0.410) | 0.45 (0.338, 0.607) |
PFS = progression-free survival; CI denotes confidence interval; NE = not evaluable.
Figure 3: Progression‑free survival in the gBRCAmut cohort based on IRC assessment -NOVA (ITT)
Figure 4: Progression‑free survival in the non‑gBRCAmut cohort/overall based on IRC assessment -NOVA (ITT)
Secondary efficacy endpoints in NOVA
At the final analysis, the median PFS2 in the gBRCAmut cohort was 29.9 months for patients treated with niraparib compared to 22.7 months for patients on placebo (HR = 0.70; 95% CI: 0.50, 0.97). The median PFS2 in the non-gBRCAmut cohort was 19.5 months for patients treated with niraparib compared to 16.1 months for patients on placebo (HR = 0.80; 95% CI: 0.63, 1.02).
At the final analysis of overall survival, the median OS in the gBRCAmut cohort (n = 203) was 40.9 months for patients treated with niraparib compared with 38.1 months for patients on placebo (HR = 0.85; 95% CI: 0.61, 1.20). The cohort maturity for the gBRCAmut cohort was 76%. The median OS in the non-gBRCAmut cohort (n = 350) was 31.0 months for patients treated with niraparib compared with 34.8 months for patients on placebo (HR = 1.06; 95% CI: 0.81, 1.37). The cohort maturity for the non-gBRCAmut cohort was 79%.
Patient reported outcomes
Patient-reported outcome data from validated survey tools (FOSI and EQ-5D) indicate that niraparib-treated patients reported no difference from placebo in measures associated with quality of life (QoL).
Paediatric population
The European Medicines Agency has waived the obligation to submit the results of studies with Zejula in all subsets of the paediatric population in ovarian carcinoma excluding rhabdomyosarcoma and germ cell tumours (see section 4.2 for information on paediatric use).