Simultaneous determination of tenofovir alafenamide and tenofovir in human plasma by LC-MS/MS and its application to pharmacokinetics study in clinic.

An ultra performance liquid chromatography-tandem mass spectrometric (UHPLC-MS/MS) method has been developed for the simultaneous determination of tenofovir alafenamide (TAF) and it's metabolite tenofovir (TFV) in human plasma. The analytes and inter standards, TAF-d5 and TFV-d6 were extracted from human plasma via protein precipitation (PPT) and only 200 μl plasma was needed. Chromatography separation was achieved on a Waters Acquity UHPLC HSS T3 column (100 * 2.1 mm, 1.8 μm) with a total run time of 10 min. A tandem mass spectrometric detection was conducted using multiple reaction monitoring (MRM) mode under positive ionization mode with an electrospray ionization (ESI) interface. The method was developed and validated over the concentration range of 4.00-400 ng/ml for TAF and 0.400-40.0 ng/ml for TFV, respectively. Each analyte in acidified plasma was found stable during sample storage, preparation and analytical procedures. The method has successfully overcame the lack of stability of analytes in plasma samples and been applied to the pharmacokinetics study of treatment of 25 mg TAF in 8 healthy volunteers under fasting condition.