A supported liquid extraction LC–MS/MS method for determination of concentrations of GDC‐0425, a small molecule Checkpoint kinase 1 inhibitor, in human plasma

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of GDC-0425 concentrations in human plasma has been developed and validated. Supported liquid extraction was used to extract plasma samples (50 μL) and the resulting samples were analyzed using reverse-phase chromatography and mass spectrometry coupled with a turbo-ionspray interface. The mass analysis of GDC-0425 was performed using multiple reaction monitoring transitions in positive ionization mode. The method was validated over the calibration curve range of 1.00-1000 ng/mL using linear regression and 1/x2 weighting. Within-run relative standard deviation ranged from 0.8 to 5.1%, while between-run RSD varied from 1.9 to 4.7% for QCs. The accuracy ranged from 90.0 to 101.0% of nominal for within-run and from 94.0 to 100.0% of nominal for between-run. Overall extraction recovery was 87.4% for GDC-0425 and 87.9% for GDC-0425-d9 . Stability of GDC-0425 was established in human plasma for 374 days at -20 and -70 °C and established in reconstituted sample extracts for 88 h when stored at 2-8 °C. Stable-labeled internal standard was used to minimize matrix effects. This assay was used to characterize the pharmacokinetics of GDC-0425 in cancer patients.