Liquid chromatography-tandem mass spectrometric assay for the quantification of galunisertib in human plasma and the application in a pre-clinical study.

• First reported quantitative assay for the determination of galunisertib in human plasma. • Fast and elegant HPLC-MS/MS method for quantification of galunisertib in human plasma. • Application of a simple chromatographic method for quantification of galunisertib in small volumes of mouse plasma. Galunisertib is an anti-cancer drug currently evaluated in phase I and II clinical trials. This study describes the development and validation of a bioanalytical assay to quantify galunisertib in human plasma using HPLC-MS/MS. Stable isotope labelled galunisertib was added as internal standard and the analyte and internal standard were extracted from the matrix by protein precipitation using acetonitrile-methanol (50:50, v/v). Final extracts were injected onto a C18 column, gradient elution was applied for chromatographic separation and detection was performed using a triple quadrupole mass spectrometer operating in the positive ion mode. The assay was linear over the range 0.05–10 ng/mL, with acceptable accuracy (bias ranging from −6.1 to 3.1%) and precision (below 5.7% C.V.) values. The applicability of the assay was demonstrated in a pharmacokinetic experiment in mice. [ABSTRACT FROM AUTHOR]