Nelfinavir (brand name Viracept) is an antiretroviral drug used in the treatment of the human immunodeficiency virus (HIV). Nelfinavir belongs to the class of drugs known as protease inhibitors (PIs) and like other PIs is generally used in combination with other antiretroviral drugs. Nelfinavir mesylate (Viracept, formally AG1343) is a potent and orally bioavailable human immunodeficiency virus HIV-1 protease inhibitor (Ki=2nM) and is[when?] being widely prescribed in combination with HIV reverse transcriptase inhibitors for the treatment of HIV infection. [1] source: http://en.wikipedia.org/wiki/Nelfinavir