A drug called T-20 or enfuvirtide (Fuzeon ®) is the first in a new class of drugs called fusion inhibitors that appear to have antiviral activity against most HIV strains. Fusion inhibitors stop HIV from replicating, by preventing the viruss membrane from fusing with the target cell membrane. In 2003, the U.S. Food and Drug Administration approved Fuzeon for use in combination with other HIV drugs. It also approved its use for adults and children over age six, who have advanced infection and who have developed resistance to other drugs. Fuzeon ® is given by injection.
Injection site reactions, neutropenia
Bonding of HIV gp-120 to cell CD4 receptors and coreceptors provides a stable connection between the virus and the cell. Once bound to the CD4 receptor gp-120 changes shape, this exposes the central gp-41 fusion unit. The gp-41 fusion unit is an assembly of three dynamic helices endowed with terminal spikes. The spikes insert into the cell membrane. Once attached to the cell membrane, the gp-41 helices begin to coil, contract and contort which brings the cell membrane and the viral membrane into proximity. It is believed that T-20 binds to the gp-41 helices thereby inhibiting contraction.