Explain Fomivirsen 

Fomivirsen, an  antisense oligonu- cleotide, is FDA-approved for intravitreal treatment of CMV retinitis in HIV-infected patients who cannot tolerate or have not responded to other drugs. The manufacturer recommends not giving fomivirsen to patients who have been treated with cidofovir in the previous 2 to 4 weeks because of increased risk of ocular inflammation. The most commonly reported adverse effects include iritis, vitritis, enhanced intraocular pressure and vision changes. In vivo resistance has not been observed