Temsavir is the active component of the prodrug fostemsavir, used in the treatment of HIV-1 infection, particularly in heavily treatment-experienced patients with multidrug-resistant HIV. It functions as an attachment inhibitor, blocking the initial step of viral entry into host CD4+ T-cells by binding to the gp120 protein on the HIV envelope. This prevents the virus from attaching to the CD4 receptor, thereby inhibiting infection of healthy cells. Its primary application is in salvage therapy regimens where other antiretroviral drugs have failed due to resistance or intolerance. Temsavir has shown efficacy in restoring viral suppression when combined with other active antiretrovirals in patients with limited treatment options. Because of its unique mechanism of action, it has low cross-resistance with other classes of antiretrovirals, making it a valuable addition to combination therapy for resistant HIV strains.