Liquid chromatography-tandem mass spectrometric assay for the quantitative determination of the tyrosine kinase inhibitor quizartinib in mouse plasma using salting-out liquid-liquid extraction

A bioanalytical assay for quizartinib -a potent, and selective FLT3 tyrosine kinase inhibitor-in mouse plasma was developed and validated. Salting-out assisted liquid-liquid extraction (SALLE), using acetonitrile and magnesium sulfate, was selected as sample pretreatment with deuterated quizartinib as internal standard. Separation was performed with reversed-phase liquid chromatography followed by detection with positive electrospray-triple quadrupole mass spectrometry in the selected reaction monitoring mode. The assay was successfully validated for mouse plasma in a 2-2000 ng/ml calibration range with r(2) = 0.9958 +/- 0.0028 (n = 7) for linear regression with the inverse square of the concentration as a weighting factor. The within-run precision (n = 18), between run precision and accuracy were 2.9-6.0%, 4.5-8.9% and 91.7-109.4% respectively. The drug was stable under all relevant conditions. Finally, the assay was successfully applied in a pharmacokinetic pilot study in plasma of FVB/NRj mice treated with quizartinb orally.