Simultaneous determination of subutinib and its active metabolite in human plasma by LC-MS/MS: Application to pharmacokinetic study

A selective liquid chromatographic-mass spectrometric method (LC-MS/MS) has been established and validated for simultaneous determination of subutinib and its active metabolite in human plasma. Plasma samples were extracted by liquid-liquid extraction with ethyl acetate and separated on a Wondasil C18 (150 mm × 2.1 mm, 3.5 μm), with methanol-0.2% formic acid solution (73:27, v/v) as mobile phase at flow rate of 0.2 ml/min. The linear range was 0.25-100 ng/mL for subutinib and 0.125-50.0 ng/mL for its active metabolite, with lower limit of quantitation of 0.25 ng/mL and 0.125 ng/mL, respectively. Intra- and inter-run precision were within 7.0 and 13.1%, and the accuracies (relative errors) were < 7.0 and 8.0%, with the extraction recoveries 97.0-101.2% and 93.0-98.1% for the two analytes, respectively. The validated method was successfully applied to a pharmacokinetic study of subutinib and its active metabolite in human after oral administration of subutinib maleate capsules.