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: Concomitant administration of a high-fat meal (800 to 1,000 calories with approximately 50% of total caloric content of the meal from fat) did not significantly affect the pharmacokinetics of niraparib.
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 (t1/2) 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 (2.4)]. 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.