Fostemsavir
Fostemsavir is the phosphonooxymethyl prodrug of temsavir, a novel HIV-1 attachment inhibitor. It binds to and inhibits the activity of gp120, a subunit within the HIV-1 gp160 envelope glycoprotein that facilitates the attachment of HIV-1 to host cell CD4 receptors - in doing so, temsavir prevents the first step in the HIV-1 viral lifecycle. The discovery of gp120 as a potential target of interest in the treatment of HIV-1 infection is relatively recent, and was born out of a desire to find alternative target proteins (i.e. mechanistically orthogonal therapies) for the treatment of HIV-1 patients with resistant infections. Fostemavir is the first attachment inhibitor to receive FDA approval, granted in July 2020 for use in combination with other antiretrovirals in highly treatment-experienced patients with multidrug-resistant HIV-1 infection whom are failing their current therapy. Targeting gp120 subunits is a new and novel therapeutic approach to HIV-1 infection, and the addition of attachment inhibitors, like temsavir, to the armament of therapies targeted against HIV-1 fills a necessary niche for therapeutic options in patients left with few, if any, viable treatments.