Amprenavir (Agenerase, VX-478), is an orally-available, sulfonamide-based inhibitor of HIV-1 protease, with relatively weak potency towards HIV-2, at IC50 values of 0.6 and 19 nM, respectively. [1] Similar to other HIV-1 protease inhibitors, Amprenavir binds to the active site of HIV-1 and inhibits the processing of the gag and gag-pol polyprotein precursors. The drug concentration of Amprenavir required to reduce viral production by 50% (IC50) against HIV-1 strain IIIB was 0.08 uM in acutely infected cells and 0.41 uM in chronically infected cells. Using a different cell line derived from a human T-cell lymphoma, the IC90 of Amprenavir against HIV-1 strain IIIB was 0.079 uM. [1]

Human dose-escalation studies showed that Amprenavir was well tolerated at single doses up to 1200 mg with minimal effect on absorption by food administration, unlike with other protease inhibitors such as indinavir, nelfinavir, and saquinavir. [2]