Enfuvirtide is the first representative of a new group of antiretrovirals - fusion inhibitors, which was approved for clinical use. Due to its attachment to the HR1 domain of HIV glycoprotein gp 41 enfuvirtide blocks the fusion between the virus and the target cell. Enfuvirtide is chemically a synthetic peptide consisting of 36 amino acids which is not stable in GIT and must be administered only subcutaneously. Enfuvirtide has been registered for the use as salvage therapy of patients with multiresistance, for who it is not possible to constitute an effective combination of other available antiretrovirals.