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Efficacy assessments using a combination of ibrutinib and lenalidomide necessitate the development of an analytical method for determination of both drugs in plasma with precision. A high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous determination of lenalidomide, ibrutinib, and its active metabolite PCI45227 in rat plasma. Extraction of lenalidomide, ibrutinib, PCI45227 and tolbutamide (internal standard; IS) from 50 μl rat plasma was carried out by liquid-liquid extraction with ethyl acetate:dichloromethane (90:10) ratio. Chromatographic separation of analytes was performed on YMC pack ODS AM (150 mm × 4.6 mm, 5 μm) column under gradient conditions with acetonitrile:0.1% formic acid buffer as the mobile phases at a flow rate of 1 ml/min. Precursor ion and product ion transition for 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 0.72-183.20 ng/ml for ibrutinib, 0.76-194.33 ng/ml for PCI-45227 and 1.87-479.16 ng/ml for lenalidomide. Mean extraction recovery for ibrutinib, PCI-45227, lenalidomide and IS of 75.2%, 84.5%, 97.3% and 92.3% 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 was evaluated for all the analytes. The analytical method was applied to support a pharmacokinetic study of simultaneous estimation of lenalidomide, ibrutinib, and its active metabolite PCI-45227 in Wistar rat. Assay reproducibility was demonstrated by re-analysis of 18 incurred samples., (Copyright © 2014 Elsevier B.V. All rights reserved.)

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 50μl rat plasma was carried out by protein precipitation with methanol. Chromatographic separation of analytes was performed on YMC pack ODS AM (150mm×4.6mm, 5μm) column under gradient conditions with acetonitrile:2.0mM ammonium acetate buffer as the mobile phase at a flow rate of 1ml/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 0.16-247ng/ml for ruxolitinib and 0.86-219ng/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., (Copyright © 2014 Elsevier B.V. All rights reserved.)