Clinical Pharmacology for Zejula
Mechanism Of Action
Niraparib is an inhibitor of PARP enzymes, including PARP-1 and PARP-2, that 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 tumor cell lines with or without deficiencies in BRCA1/2. Niraparib decreased tumor growth in mouse xenograft models of human cancer cell lines with deficiencies in BRCA1/2 and in human patient-derived xenograft tumor models with homologous recombination deficiency (HRD) that had either mutated or wild-type BRCA1/2.
Pharmacodynamics
The pharmacodynamic response of niraparib has not been characterized.
Hypertension And Cardiovascular Effects
Niraparib has the potential to cause effects on pulse rate and blood pressure in patients receiving the recommended dose, which may be related to pharmacological inhibition of the dopamine transporter (DAT), norepinephrine transporter (NET), and serotonin transporter (SERT) [see Nonclinical Toxicology].
In the PRIMA study, mean pulse rate and blood pressure increased over baseline in the niraparib arm relative to the placebo arm at most on-study assessments. Mean greatest increases from baseline in pulse rate on treatment were 22.4 and 14.0 beats/min in the niraparib and placebo arms, respectively. Mean greatest increases from baseline in systolic blood pressure on treatment were 24.4 and 19.6 mmHg in the niraparib and placebo arms, respectively. Mean greatest increases from baseline in diastolic blood pressure on treatment were 15.9 and 13.9 mmHg in the niraparib and placebo arms, respectively.
In the NOVA study, mean pulse rate and blood pressure increased over baseline in the niraparib arm relative to the placebo arm at all on-study assessments. Mean greatest increases from baseline in pulse rate on treatment were 24.1 and 15.8 beats/min in the niraparib and placebo arms, respectively. Mean greatest increases from baseline in systolic blood pressure on treatment were 24.5 and 18.3 mmHg in the niraparib and placebo arms, respectively. Mean greatest increases from baseline in diastolic blood pressure on treatment were 16.5 and 11.6 mmHg in the niraparib and placebo arms, respectively.
Cardiac Electrophysiology
The potential for QTc prolongation with niraparib was evaluated in a randomized, placebo-controlled trial in patients with cancer (367 patients on niraparib and 179 patients on placebo). No large changes in the mean QTc interval (>20 ms) were detected in the trial following the treatment of niraparib 300 mg once daily.
Pharmacokinetics
Following a single-dose administration of 300 mg niraparib, the mean (±SD) peak plasma concentration (Cmax) was 804 (±403) ng/mL. The exposure (Cmax and AUC) of niraparib increased in a dose-proportional manner with daily doses ranging from 30 mg (0.1 times the approved recommended dose) to 400 mg (1.3 times the approved recommended dose). The accumulation ratio of niraparib exposure following 21 days of repeated daily doses was approximately 2-fold for doses ranging from 30 to 400 mg.
Absorption
The absolute bioavailability of niraparib is approximately 73%. Following oral administration of niraparib, peak plasma concentration, Cmax, is reached within 3 hours.
Food Effect
Following a high-fat meal (800 to 1,000 calories with approximately 50% of total caloric content of the meal from fat) in patients with solid tumors, the Cmax of niraparib tablets increased by 11% and AUCinf increased by 28%, as compared with fasted conditions.
Distribution
Niraparib is 83.0% bound to human plasma proteins. The average (±SD) apparent volume of distribution (Vd/F) was 1,220 (±1,114) L. In a population pharmacokinetic analysis, the Vd/F of niraparib was 1,074 L in patients with cancer.
Elimination
Following multiple daily doses of 300 mg of niraparib, the mean half-life (t½) is 36 hours. In a population pharmacokinetic analysis, the apparent total clearance (CL/F) of niraparib was 16.2 L/h in patients with cancer.
Metabolism
Niraparib is metabolized by carboxylesterases (CEs) to form a major inactive metabolite, which subsequently undergoes glucuronidation.
Excretion
Following administration of a single oral 300-mg dose of radio-labeled niraparib, the average percent recovery of the administered dose over 21 days was 47.5% (range: 33.4% to 60.2%) in urine and 38.8% (range: 28.3% to 47.0%) in feces. In pooled samples collected over 6 days, unchanged niraparib accounted for 11% and 19% of the administered dose recovered in urine and feces, respectively.
Specific Populations
Age (18 to 65 years), race/ethnicity, and mild to moderate renal impairment (CLcr ≥30 to 90 mL/min) had no clinically significant effect on the pharmacokinetics of niraparib.
The effect of severe renal impairment (CLcr <30 mL/min) or end-stage renal disease undergoing hemodialysis on the pharmacokinetics of niraparib is unknown.
Patients With Hepatic Impairment
Mild hepatic impairment (total bilirubin <1.5 x ULN and any AST level or bilirubin ≤ ULN and AST > ULN) had no clinically significant effect on the pharmacokinetics of niraparib.
In a trial of patients with moderate hepatic impairment (total bilirubin ≥1.5 x ULN to 3.0 x ULN and any AST level) (n = 8), niraparib AUCinf was 1.56 (90% CI: 1.06 to 2.30) times higher compared with patients with normal hepatic function (n = 9) following administration of a single 300-mg dose. Niraparib dosage reduction is recommended for patients with moderate hepatic impairment [see DOSAGE AND ADMINISTRATION]. Moderate hepatic impairment did not have an effect on niraparib Cmax or on niraparib protein binding.
The effect of severe hepatic impairment (total bilirubin >3.0 x ULN and any AST level) on the pharmacokinetics of niraparib is unknown.
Drug Interaction Studies
No clinical drug interaction studies have been performed with ZEJULA.
In Vitro Studies
Inhibition of Cytochrome P450 (CYP) Enzymes: Neither niraparib nor the major primary metabolite M1 is an inhibitor of CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4.
Induction Of CYP Enzymes
Neither niraparib nor M1 is a CYP3A4 inducer. Niraparib weakly induces CYP1A2 in vitro.
Substrate Of CYP Enzymes
Niraparib is a substrate of CEs and the resulting M1 is further metabolized through the formation of glucuronides in vivo.
Inhibition Of Uridine 5'-Diphospho-Glucuronosyltransferases (UGTs)
Niraparib did not exhibit inhibitory effect against the UGT isoforms (UGT1A1, UGT1A4, UGT1A9, and UGT2B7) up to 200 microM in vitro. Therefore, the potential for a clinically relevant inhibition of UGTs by niraparib is minimal.
Inhibition Of Transporter Systems
Niraparib is a weak inhibitor of breast cancer resistance protein (BCRP), but does not inhibit P-glycoprotein (P-gp), bile salt export pump (BSEP), or multidrug resistance-associated protein 2 (MRP2).
Niraparib is an inhibitor of multidrug and toxin extrusion (MATE) 1 and 2 with IC50 of 0.18 microM and ≤0.14 microM, respectively. Increased plasma concentrations of coadministered drugs that are substrates of these transporters (e.g., metformin) cannot be excluded.
The M1 metabolite is not an inhibitor of P-gp, BCRP, BSEP, MRP2, or MATE1 or 2. Neither niraparib nor M1 is an inhibitor of organic anion transporting polypeptide (OATP)1B1, OATP1B3, organic cation transporter (OCT1)1, organic anion transporter (OAT)1, OAT3, or OCT2.
Substrate Of Transporter Systems
Niraparib is a substrate of P-gp and BCRP. Niraparib is not a substrate of BSEP, MRP2, or MATE1 or 2. The M1 metabolite is not a substrate of P-gp, BCRP, BSEP, or MRP2. However, M1 is a substrate of MATE1 and 2. Neither niraparib nor M1 is a substrate of OATP1B1, OATP1B3, OCT1, OAT1, OAT3, or OCT2.
Animal Toxicology And/Or Pharmacology
In vitro, niraparib bound to DAT, NET, and SERT and inhibited uptake of norepinephrine and dopamine in cells with IC50 values that were lower than the Cmin at steady-state in patients receiving the recommended dose. Niraparib has the potential to cause effects in patients related to inhibition of these transporters (e.g., cardiovascular, central nervous system).
Intravenous administration of niraparib to vagotomized dogs over 30 minutes at 1, 3, and 10 mg/kg resulted in an increased range of arterial pressures of 13% to 20%, 18% to 27%, and 19% to 25%, respectively, and increased range of heart rates of 2% to 11%, 4% to 17%, and 12% to 21%, respectively, above pre-dose levels. The unbound plasma concentrations of niraparib in dogs at these dose levels were approximately 0.5, 1.5, and 5.8 times the unbound Cmax at steady-state in patients receiving the recommended dose.
In addition, niraparib crossed the blood-brain barrier in rats and monkeys following oral administration. The cerebrospinal fluid:plasma Cmax ratios of niraparib administered at 10 mg/kg orally to 2 rhesus monkeys were 0.10 and 0.52.
Clinical Studies
First-Line Maintenance Treatment Of Advanced Ovarian Cancer
PRIMA (NCT02655016) was a double-blind, placebo-controlled trial in which patients (N = 733) in complete or partial response to first-line platinum-based chemotherapy were randomized 2:1 to ZEJULA or matched placebo. Initially, the patients received a starting dosage of 300 mg once daily regardless of body weight or platelet count. The study was amended to include a starting dose of 200 mg for patients weighing <77 kg (<170 lbs) OR with a platelet count of <150,000/mcL or 300 mg for patients weighing ≥77 kg (≥170 lbs) AND who had a platelet count ≥150,000/mcL.
Patients were randomized post-completion of first-line platinum-based chemotherapy plus surgery. Randomization was stratified by best response during the front-line platinum regimen (complete response vs. partial response), neoadjuvant chemotherapy (NACT) (yes vs. no), and HRD status (positive vs. negative or not determined). HRD status was determined using the FDA-approved Myriad myChoice CDx assay. HRD positive status included either tumor BRCA mutant (tBRCAm) or a genomic instability score (GIS) ≥42.
The major efficacy outcome measure, progression-free survival (PFS), was determined by blinded independent central review (BICR) per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. In some cases, criteria other than RECIST, such as clinical signs and symptoms and increasing CA-125, were also applied. Overall survival was an additional efficacy outcome measure. PFS testing was performed hierarchically: first in the homologous recombination (HR)-deficient (HRD positive) population, then in the overall population. The median age of 62 ranged from 32 to 85 years among patients randomized with ZEJULA and 33 to 88 years among patients randomized with placebo. Eighty-nine percent of all patients were White. Sixty-nine percent of patients randomized with ZEJULA and 71% of patients randomized with placebo had an Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0 at study baseline. Approximately 45% of patients were enrolled in the U.S. or Canada. In the overall population, 65% of patients had stage III disease and 35% had stage IV disease. Sixty-seven percent of the patients received NACT. Sixty-nine percent of the patients had a complete response to the first-line platinum-based chemotherapy. Approximately 35% (n = 258) of patients received a starting dose of 200 or 300 mg depending on baseline body weight and platelet count. Among those patients, 186 patients received a starting dose of 200 mg.
PRIMA demonstrated a statistically significant improvement in PFS for patients randomized to ZEJULA as compared with placebo in the HR-deficient and overall population (Table 10, Figure 1, and Figure 2).
Table 10: Efficacy Results – PRIMA (determined by BICRa)
|
HR-Deficient Population |
Overall Population |
ZEJULA
(n = 247) |
Placebo
(n = 126) |
ZEJULA
(n = 487) |
Placebo
(n = 246) |
| Progression-free survival events, n (%) |
81 |
73 |
232 |
155 |
| (33) |
(58) |
(48) |
(63) |
| Progression-free survival median in months (95% CI) |
21.9 |
10.4 |
13.8 |
8.2 |
| (19.3, NE) |
(8.1, 12.1) |
(11.5, 14.9) |
(7.3, 8.5) |
| Hazard ratiob |
0.43 |
0.62 |
| (95% CI) |
(0.31, 0.59) |
(0.50, 0.76) |
| P valuec |
<0.0001 |
<0.0001 |
BICR = Blinded Independent Central Review, HR = Homologous Recombination, NE = not estimable.
a Efficacy analysis was based on blinded independent central review.
b Based on a stratified Cox proportional hazards model.
c Based on a stratified log-rank test. |
In exploratory subgroup analyses of patients who were administered a starting dose of ZEJULA or matched placebo based on baseline weight or platelet count, the hazard ratio for PFS was 0.39 (95% CI: 0.22, 0.72) in the HR-deficient subgroup (n = 130) and 0.68 (95% CI: 0.48, 0.97) in the overall population (n = 258).
Figure 1: Progression-Free Survival – PRIMA Patients with HR-Deficient Tumors (Intent-to-Treat Population, N = 373)
Figure 2: Progression-Free Survival – PRIMA Overall Population (Intent-to-Treat Population, N = 733)
At the time of the PFS analysis, overall survival data were immature, with 11% deaths in the overall population.
Maintenance Treatment Of Recurrent Germline BRCA-mutated Ovarian Cancer
NOVA (NCT01847274) was a double-blind, placebo-controlled trial in which patients (N = 553) with platinum-sensitive recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer were randomized 2:1 to ZEJULA 300 mg orally daily or matched placebo within 8 weeks of the last therapy. Treatment was continued until disease progression or unacceptable toxicity. All patients had received at least 2 prior platinum-containing regimens and were in response (complete or partial) to their most recent platinum-based regimen.
Randomization was stratified by time to progression after the penultimate platinum therapy (6 to <12 months and ≥12 months), use of bevacizumab in conjunction with the penultimate or last platinum regimen (yes/no), and best response during the most recent platinum regimen (complete response and partial response). Eligible patients were assigned to 1 of 2 cohorts based on the results of germline BRCA testing with Myriad BRACAnalysis CDx. Patients with deleterious or suspected deleterious germline BRCA mutations (gBRCAmut) were assigned to the germline BRCA-mutated (gBRCAmut) cohort (n = 203), and those without germline BRCA mutations were assigned to the non-gBRCAmut cohort (n = 350). The efficacy results are based on the gBRCAmut cohort only.
The major efficacy outcome measure, PFS, was determined primarily by central independent assessment per RECIST version 1.1. In some cases, criteria other than RECIST, such as clinical signs and symptoms and increasing CA-125, were also applied. Overall survival (OS) was an additional outcome measure.
For the gBRCAmut cohort, the median age of patients was 57 years among patients treated with ZEJULA and 58 years among patients treated with placebo. Eighty-eight percent of all patients were White. Sixty-six percent of patients receiving ZEJULA and 74% of patients receiving placebo had an ECOG PS of 0 at study baseline. Approximately 40% of patients were enrolled in the U.S. or Canada, and 51% of all patients were in complete response to most recent platinum-based regimen, with 39% on both arms with an interval of 6 to 12 months since the penultimate platinum regimen. Twenty-four percent of those treated with ZEJULA and 26% treated with placebo had received prior bevacizumab therapy. Approximately 50% of patients had 3 or more lines of treatment.
The trial demonstrated a statistically significant improvement in PFS for patients randomized to ZEJULA as compared with placebo in the gBRCAmut cohort (Table 11 and Figure 3).
Table 11: Efficacy Results – NOVA gBRCAmut Cohort (IRC Assessmenta)
|
ZEJULA
(n = 138) |
Placebo
(n = 65) |
| Progression-free survival median in months (95% CI) |
21.0 (12.9, NR) |
5.5 (3.8, 7.2) |
| Hazard ratiob (95% CI) |
0.26 (0.17, 0.41) |
| P valuec |
<0.0001 |
IRC = Independent Review Committee, gBRCAmut = germline BRCA-mutated, NR = not reached.
a Efficacy analysis was based on blinded central independent radiologic and clinical oncology review committee.
b Based on a stratified Cox proportional hazards model.
c Based on a stratified log-rank test. |
Figure 3: Progression-Free Survival – NOVA gBRCAmut Cohort Based on IRC Assessment (N = 203)
gBRCAmut = germline BRCA-mutated, IRC = Independent Review Committee.
A final OS analysis was conducted after 154 events were observed. Exploratory OS results showed a HR of 0.85 (95% CI: 0.61, 1.20) in the gBRCAmut cohort with a median OS of 40.9 months (95% CI: 34.9, 52.9) for patients treated with ZEJULA and 38.1 months (95% CI: 27.6, 47.3) for patients on placebo.