Saquinavir
Saquinavir is an HIV-1 protease inhibitor used in combination with [ritonavir] and other antiretrovirals for the treatment of human immunodeficiency virus-1 (HIV-1) infection. In 1995 it became the first protease inhibitor approved by the FDA, followed shortly by ritonavir in 1996, and remains in clinical use today due to a relatively benign adverse effect profile as compared to other antiretroviral therapies. While its efficacy was initially limited by exceptionally poor oral bioavailability (approximately 4%), its current indications require the co-administration of ritonavir - a potent enzyme inhibitor - that increases the bioavailability and subsequent serum concentrations of saquinavir, thus dramatically improving antiviral activity.