Novel determination of sofosbuvir and velpatasvir in human plasma by UPLC–MS/MS method: Application to a bioequivalence study

: A novel and sensitive LC-MS/MS method was developed, optimized and validated for quantification of sofosbuvir (SOF) and velpatasvir (VEL) in human plasma using ledipasvir as an internal standard (IS). Sample preparation was done using acetonitrile for precipitation of plasma proteins. Chromatographic analysis was done on an Acquity UPLC BEH C18 column using 0.1% formic acid and acetonitrile as a mobile phase. The Xevo TQD LC-MS/MS system was run with electrospray ionization mode. The developed method was optimized and then validated according to the US Food and Drug Administration guidelines. Linearity was found to be in the range of 0.25-3500 ng/mL for SOF and 1-1000 ng/mL for VEL. A short run time of 1.5 min allows swift analysis of many plasma samples per day. The developed method was successfully utilized for estimating both SOF and VEL in the plasma of healthy human volunteers participated in a bioequivalence study.