T-20 (enfuvirtide, Fuzeon) is the first of a new class of drugs called fusion inhibitors, so-called because they stop HIV from binding to and entering the human cell.

T-20 binds to a protein on the surface of HIV called gp41, which is the ‘key’ used by HIV to bind onto and enter cells. By blocking gp41, T-20 blocks the infection of cells by HIV.

T-20 was developed by Trimeris Pharmaceuticals and Roche. Formerly known by the generic name pentafuside, it is now called enfuvirtide, and is marketed under the trade name Fuzeon.

European and United States drug regulatory authorities granted accelerated approval for T-20 in March 2003. It has been approved for use in individuals who have experienced failure of at least one drug from each existing class of antiretrovirals, or who have intolerance to previous antiretroviral regimens. Traditional approval in the United States was granted in October 2004.