Validation of a rapid liquid chromatography tandem mass spectrometric method for the quantitative analysis of vistusertib

•Assay developed and validated for vistusertib over the range of 5–5000 ng/mL.•Validated according to the FDA guidance.•Plasma stability documented for 29 months at −70 °C.•Applied to an on-going clinical trial to assess the pharmacokinetics in patients. Vistusertib is an orally bioavailable mTOR inhibitor that is being studied in clinical trials. A novel reliable method was developed to quantitate vistusertib using LC-MS/MS to explore drug exposure-response relationships. Sample preparation involved protein precipitation using acetonitrile. Separation of vistusertib and the internal standard, AZD8055, was achieved with a Waters Acquity UPLC BEH C18 column utilizing isocratic elution over a 3 min total analytical run time. A SCIEX 4500 triple quadrupole mass spectrometer operated in positive electrospray ionization mode was used for the detection of vistusertib. The assay range was 5–5000 ng/mL and proved to be accurate (98.7–105.7%) and precise (CV ≤ 10.5%). A 40,000 ng/mL sample that was diluted 1:10 (v/v) with plasma was accurately quantitated. Long-term frozen plasma stability for vistusertib at −70 °C has been determined for at least 29 months. The method was applied for the measurement of plasma concentrations of vistusertib in a patient a solid tumor receiving 35 mg twice daily dose orally.