Modeling and impact of organ function on the population pharmacokinetics (PK) of niraparib, a selective poly (ADP-Ribose) polymerase (PARP)-1 and -2 inhibitor

Abstract

Background: Niraparib (ZEJULATM) is a selective PARP-1 and -2 inhibitor approved for maintenance treatment in adults with recurrent ovarian cancer in complete or partial response to platinum-based chemotherapy.We developed a population PK (PPK) model for niraparib and determined the impact of hepatic and renal organ impairment on niraparib exposure. Method(s): Data from the phase 1 dose escalation and expansion (dose ranging from 30 to 400 mg once daily [qd]) and phase 3 ENGOT-OV16/NOVA (300 mg qd) studies were modeled using a compartmental population approach within nonlinear mixedeffects modeling (NONMEM). Patients (pts) who received a dose of niraparib were included in the PK analysis. The PPK base model was built usingNONMEMtechniques from the phase 1 study. The impact of pt variables (age, race, ethnicity, body weight), renal impairment (normal, mild, or moderate, based on serum creatinine clearance) and hepatic function (baseline serum alanine and aspartate aminotransferase, albumin, total bilirubin) on niraparib PK parameters was evaluated. A step-wise elimination procedure for each covariate was used to develop the final model. Model evaluation was performed via a visual predictive check. Result(s): 512 pts (33-83 years old) were available for PK analysis (4109 measurements) from the phase 1 (n=104) and phase 3 (n=408) studies. A 2-compartment model (2CM) with first-order absorption and elimination best described the niraparib PK. In the base model, the typical value for niraparib apparent clearance was 16.2 L/h, with interindividual variability of 52.6%. The estimated volume of distribution was 1074 L (290 L central and 784 L peripheral compartment. Model diagnostics showed good agreement between predicted and observed individual niraparib plasma concentrations. No patient variables impacted niraparib PK. Neither the mild to moderate renal impairment nor the mild hepatic impairment significantly altered niraparib PK. Conclusion(s): Niraparib disposition was best described by a 2-compartment model with moderate to high interindividual variability. Mild to moderate organ impairment did not significantly impact niraparib PK; no dose adjustments are recommended.