An HIV protease inhibitor; inhibits recombinant HIV-1 protease by 79% at 0.5 nM; inhibits HIV-13B-induced cell death in MT-4 human T cell leukemia cells (EC50 = 25 nM); inhibits cell death induced by HIV-1LAI, HIV-2ROD, and HIV-2EHO in human MT-2 cells (IC50s = 0.045, 0.13, and 0.24 μM, respectively); inhibits the CYP isoform CYP3A (IC50 = 0.14 μM); inhibits CYP-mediated oxidative metabolism of saquinavir, indinavir, nelfinavir, and amprenavir in rat and human liver microsomes; prevents decreases in plasma levels of these four compounds in rats at 10 mg/kg