Simultaneous quantification of ruxolitinib and nilotinib in rat plasma by LC–MS/MS: Application to a pharmacokinetic study

• Highly selective method for the determination of ruxolitinib and nilotinib in plasma.
• This is the first LC–MS/MS-based method for simultaneous determination of ruxolitinib and nilotinib in plasma.
• Plasma sample clean-up involves a simple protein precipitation procedures.
• The developed LC–MS/MS based method was applied successfully for pharmacokinetic study.

Efficacy assessments using a combination of ruxolitinib and nilotinib necessitate the development of a high precision analytical method for determination of both drugs in plasma. A high performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed for the simultaneous determination of ruxolitinib and nilotinib in rat plasma. Extraction of ruxolitinib, nilotinib and dasatinib (internal standard; IS) from 50 μl rat plasma was carried out by protein precipitation with methanol. Chromatographic separation of analytes was performed on YMC pack ODS AM (150 mm × 4.6 mm, 5 μm) column under gradient conditions with acetonitrile:2.0 mM ammonium acetate buffer as the mobile phase at a flow rate of 1 ml/min. Precursor ion and product ion transition for both analytes and IS were monitored on a triple quadrupole mass spectrometer, operated in the selective reaction monitoring with positive ionization mode. Method was validated over a concentration range of 0.16–247 ng/ml for ruxolitinib and 0.86–219 ng/ml for nilotinib. Mean extraction recovery for ruxolitinib, nilotinib, and IS of 99.6%, 97.6% and 90.3% were consistent across low, medium, and high QC levels. Precision and accuracy at low, medium and high quality control levels were less than 15% across analytes. Bench top, wet, freeze-thaw and long term stability were evaluated for both analytes. The analytical method was applied to support a pharmacokinetic study of simultaneous estimation of ruxolitinib and nilotinib in Wistar rat. Assay reproducibility was demonstrated by re-analysis of 18 incurred samples.

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