A novel antiretroviral class (fusion inhibitors) in the management of HIV infection. Present features and future perspectives of enfuvirtide (T-20)

Enfuvirtide (Fuzeon (R), Roche), is the first member of a novel class of antiretroviral agents, the so-called fusion inhibitors, which act against HIV with a completely novel (extra cellular) mechanism of action, and can therefore be easily added to all anti-HIV association therapies including all other antiretroviral agents belonging to nucleoside/nucleotide reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, and protease inhibitors, since no interactions of any type are expected with enfuvirtide. Despite the need of a twice-daily parenteral (subcutaneous) delivery due to the polypeptide structure of the drug, and its proportionally short elimination lifetime, two extensive multicentre randomized clinical trials and a huge amount of other clinical and laboratory experiences confirmed the elevated potency and the safety profile of enfuvirtide in appropriate samples of HIV-infected patients (both adults and children), who failed and/or became intolerant to all previously available anti-HIV regimens, and had a very restricted choice of antiviral compounds showing residual activity. As a consequence, enfuvirtide is recommended as an adjunct to an "optimized background" containing at least one or two antiretroviral drugs, which are still active against the isolated viral strain, as assessed by resistance testing. The extremely promising profile of this novel anti-HIV drug and the reduced potential for the development of viral resistance (with no possibility of cross-resistance with the other anti-HIV classes) however warrant further pharmacokinetic, pharmacodynamic, pharmacogenomic, and pharmacoeconomic investigation. Also more extensive and prolonged clinical and quality of life studies are strongly needed to establish the best positioning of enfuvirtide in the current therapeutic guidelines of HIV disease and its future role, besides its current approval for salvage therapy of adult and pediatric HIV-infected patients with limited therapeutic options.