Quantitative analysis of a novel HIV fusion inhibitor (sifuvirtide) in HIV infected human plasma using high-performance liquid chromatography–electrospray ionization tandem mass spectrometry

A sensitive method for measuring sifuvirtide, a novel HIV fusion inhibitor peptide drug in HIV-1+ human plasma by liquid chromatography–tandem mass spectrometry (LC–MS/MS) was developed. The plasma samples were treated by solvent/detergent (S/D) method to inactivate viral activity before analysis. After protein precipitation sifuvirtide was determined by LC–MS/MS. A structure analog was used as internal standard (IS). The mass spectrometer was operated in positive ion and multiple reaction monitoring mode with transitions m/z 946.3 → 159.0 for sifuvirtide and 951.7 → 159.2 for IS. The intra-day precision ranged from 2.74% to 7.57% with accuracy from 91.63% to 102.53%. The inter-day precision ranged from 2.65% to 3.58% and the accuracy from 95.53% to 105.28%. Stability studies showed that sifuvirtide was stable both during the assay procedure and long-term storage. The lower limit of quantitation (LLOQ) was 9.75 ng ml−1. The method was used for analyzing samples from phase IIa clinical study of sifuvirtide in China.