Fusion inhibitors are a new class of drugs offered to patients with HIV-1 strains resistant to standard drug treatment. The U.S. Food and Drug Administration (FDA) approved Trimeris and Hoffmann-La Roche’s Fuzeon (enfuvirtide) in March 2003 and Pfizer’s Selzentry (maraviroc) in August 2007 to accompany current antiviral regimens.

Fuzeon is injected into the body, while Selzentry is taken orally. Both drugs work by preventing the virus from entering and infecting human immune cells. Fuzeon binds to an HIV protein and blocks its necessary conformational change to bring the viral…