DDEL-07. DETERMINATION OF TOTAL AND UNBOUND LEVELS OF A POTENT INHIBITOR OF POLY ADP-RIBOSE POLYMERASE, NIRAPARIB, IN HUMAN PLASMA, CEREBROSPINAL FLUID AND BRAIN TUMOR BY A VALIDATED LC-MS/MS ASSAY

Abstract

Abstract BACKGROUND Niraparib is an orally available inhibitor of poly ADP-ribose polymerase with high selectivity for PARP1 and PARP2. It is currently approved in the United States for the treatment of ovarian, fallopian tube, and primary peritoneal cancer. Herein we present the development and validation of an LC-MS/MS method for determination of total and unbound levels of niraparib in human plasma, cerebrospinal fluid (CSF) and glioblastoma tissue. METHODS Niraparib was extracted from human plasma, CSF and glioblastoma homogenate samples by protein precipitation with methanol. Unbound fractions of niraparib in plasma and brain tissues were determined by equilibrium dialysis. Validation was performed using Sciex ExionLC UHPLC system coupled with Sciex QTRAP 6500+ MS/MS detector using positive electrospray ionization mode. The method was validated according to FDA guidelines and CAP/CLIA regulations. RESULTS The method was validated for 1-10,000 nmol/L concentration range using plasma as matrix for all biospecimens. The chromatographic separation was performed on Phenomenex Kinetex™ PS C18 column with total run time of 3.5 min with gradient elution. Maximum coefficient of variation for intra- and inter-day precision was 10.6% and the accuracy was within 92.8-118.5% in all matrices. The analyte is stable in plasma and brain homogenate for at least 6 hours at room temperature (RT) and at least 32 days at -20°C. Stability of stock and working solutions was demonstrated for at least 21 hours (RT) and 41 days (4°C). The fraction unbound of niraparib in human plasma and brain were determined to be 0.15 and 0.05, respectively. CONCLUSIONS A sensitive and rapid bioanalytical method is developed and validated to quantify total and unbound niraparib levels in human plasma, CSF and glioblastoma tissue. This method is currently employed to assess plasma pharmacokinetics and CNS penetration of niraparib in newly-diagnosed glioblastoma and recurrent IDH1/2(+) ATRX mutant glioma patients (NCT05076513).