Overview of Antiretroviral Agents in 2005

To date, 25 antiretroviral agents (including fixed-dose combinations) have gained approval by the Food and Drug Administration and are currently available on the market for the treatment of HIV-1 infection. New protease inhibitors, atazanavir sulfate (Reyataz) and fosamprenavir (Lexiva), were licensed, in addition to the nucleoside analogue reverse transcriptase inhibitor (NRTI) emtricitabine (Emtriva) and 2 fixed-dose NRTI combinations, emtricitabine/tenofovir disoproxil fumarate (Truvada) and lamivudine/abacavir (Epzicom). These newly licensed antiretroviral agents allow for lower pill burden and dosing schedule simplification, and some agents such as atazanavir sulfate are associated with improved lipid profile in comparison to other currently marketed protease inhibitors. In addition, a new class of anti-retroviral agents, entry inhibitors, of which a subclass exists called fusion inhibitors with its representative member, enfuvirtide (Fuzeon), which is currently the only available drug in its class, was marketed almost 2 years ago. Despite a remarkable progress in the treatment of HIV infection noted during the past decade, significant challenges to therapy such as tolerability issues and emergence of drug-resistant strains remain. Therefore, new antiretroviral drug development has focused on a design of drugs that work against the resistant strains of HIV and/or have a novel mechanism of action.