Local therapy provides high intraocular concentrations of antiviral medications, is highly effective in controlling infection, is less costly than systemic treatment, and gives the patient a better quality of life. Antiviral agents used for intraocular therapy include Ganciclovir, Foscarnet, Cidofovir, and Fomivirsen. It is highly effective and probably superior to the intravenous agents at controlling infection. Fomivirsen represents the first of a new class of antisense drugs. Fomivirsen prevents the CMV virus from forming proteins essential to its growth.
Drug resistance is a problem with current antivirals.
However, drug resistance cannot develop with antisense drugs. Initial clinical trials evaluated two dosing regimens, one for new and one for previously treated cases of CMV retinitis. Intraocular fomivirsen prevented the progression of CMV retinitis in both of these trials. Retinal detachment was less common than that usually observed with other treatments for CMV retinitis. There were no systemic toxicities from the ocular injections.