Adding Amprenavir To HIV Drugs By Liquid Chromatography–Mass Spectrometry (LC/MS/MS) Assay

By Ronald E. Shoup, Yingjie Deng, Angela P. Johnson, and David M. Morris

Amprenavir is a second generation human immunodeficiency viral protease inhibitor marketed as Agenerase by GlaxoWellcome under license from Vertex Pharmaceuticals. The drug has demonstrated both additive and synergistic pharmacological activity against HIV in combination therapies involving both protease and reverse transcriptase inhibitors. The goal of this work was to extend our current multi-PI/RTI bioanalytical LC/MS/MS assay to include amprenavir.

Amprenavir is weakly basic and has limited aqueous solubility. The structure is given in Figure 1. In order to extract it under conditions also suitable for the other PI's and RTI's listed in Table 1, a fairly general extraction scheme had to be considered, since ritonavir was not significantly retained using a mixed mode solid phase support. We wanted the extraction scheme for amprenavir to also be suitable for ritonavir, since ritonavir is commonly administered in cocktail therapy with many of the listed drugs to boost their bioavailability.