Validation of a LC‐MS/MS Assay for Rapid and Simultaneous Quantification of Cobicistat and Venetoclax in Human Plasma and Serum

Measuring cobicistat and venetoclax concentrations in human plasma and serum facilitates therapeutic drug monitoring (TDM) and pharmacokinetic (PK) boosting studies. Therefore, the objective of this study was to develop and validate a rapid LC-MS/MS analytical method for the simultaneous determination of cobicistat and venetoclax concentrations in plasma and serum. The method was validated according to EMA and FDA guidelines. Chromatographic separation was performed using a liquid chromatography (LC) system with a C18 column. The elution gradient involved two mobile phases: mobile phase A (ammonium formate) and mobile phase B (acetonitrile). The concentration range was 5-500 μg/L for cobicistat and 50-5000 μg/L for venetoclax. Accuracy and precision were within the required limits, with accuracy ranging from -5.9% to 2.4%, within-day precision from 1.2% to 4.8%, and between-day precision from 0.4% to 4.3%. Cobicistat and venetoclax were stable for at least 8 days under various storage and handling conditions. Clinical TDM samples showed mean concentrations ± standard deviation (SD) of 138.8 ± 123.3 μg/L for cobicistat and 1497.1 ± 1285.9 μg/L for venetoclax. The development and validation of this LC-MS/MS assay provide a reliable and efficient method for the simultaneous quantification of cobicistat and venetoclax in plasma and serum samples.