Liquid chromatography-tandem mass spectrometry assay for the quantification of niraparib and its metabolite M1 in human plasma and urine

•The first reported validated LC-MS/MS assay for niraparib and its metabolite M1.•The assay has successfully been validated in the 1-500 and 1-100 ng/mL ranges.•The assay was successfully used for a bioavailability study and a mass balance study.

Niraparib (MK-4827) is a novel poly(ADP-Ribose) polymerase (PARP) inhibitor currently investigated in phase III clinical trials to treat cancers. The development of a new drug includes the characterisation of absorption, metabolism and excretion (AME) of the compound. AME studies are a requirement of regulatory agencies and for this purpose bioanalytical assays are essential. This article describes the development and validation of a bioanalytical assay for niraparib and its carboxylic acid metabolite M1 in human plasma and urine using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Sample pre-treatment involved protein precipitation for plasma and dilution of urine samples using acetonitrile-methanol (50:50, v/v). Final extracts were injected onto a SunFire C18 column and gradient elution using 20 mM ammonium acetate (mobile phase A) and formic acid:acetonitrile:methanol (0.1:50:50, v/v/v) (mobile phase B) was applied. Detection was performed on an API5500 tandem mass spectrometer operating in the positive electrospray ionisation mode applying multiple reaction monitoring (MRM). The assay was successfully validated in accordance with the Food and Drug Administration and latest European Medicines Agency guidelines on bioanalytical method validation and can therefore be applied in pharmacological clinical studies.