Development and validation of a simple, selective, and sensitive LC-MS/MS assay for the quantification of remdesivir in human plasma

Remdesivir, formerly GS-5734, has recently become the first antiviral drug approved by the U.S. Food and Drug Administration (FDA) to treat COVID-19, the disease caused by SARS-CoV-2. Therapeutic dosing and pharmacokinetic studies require a simple, sensitive, and selective validated assay to quantify drug concentrations in clinical samples. Therefore, we developed a rapid and sensitive LC-MS/MS assay for the quantification of remdesivir in human plasma with its deuterium-labeled analog, remdesivir-²H5, as the internal standard. Chromatographic separation was achieved on a Phenomenex® Synergi™ HPLC Fusion-RP (100 × 2 mm, 4 μm) column by gradient elution. Excellent accuracy and precision (<5.2% within-run variations and. <9.8% between-run variations) were obtained over the range of 0.5–5000 ng/mL. The assay met the FDA Bioanalytical Guidelines for selectivity and specificity, and low inter-matrix lot variability (<2.7%) was observed for extraction efficiency (77%) and matrix effect (123%) studies. Further, stability tests showed that the analyte does not degrade under working conditions, nor during freezing and thawing processes.