AIDS: Fomivirsen (Vitravene) is the first antisense drug to be approved by the Food and Drug Administration (FDA), and it will be used for the treatment of cytomegalovirus (CMV) retinitis. Fomivirsen is administered by intravitreal injection, and it can be used to help patients who are resistant to other treatments for CMV. Isis Pharmaceuticals, Inc., manufacturer of fomivirsen, had a difficult time recruiting people for its clinical trials, due to the decline in the incidence of opportunistic infections. However, Isis still made a presentation to the FDA, providing clinical data about patients, treatment methods, and outcomes. A detailed explanation of antisense drugs is included.