Long-acting therapy of viral retinitis with (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine.

(S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC), a high-potency antiherpes and anticytomegalovirus (CMV) drug was evaluated in the treatment of experimental retinitis caused by preretinal herpes simplex virus (HSV-1) injection in rabbits. HPMPC (100 micrograms/0.1 mL) was intravitreally injected 10, 15, 21, 30, or 46 days before, concurrently, or 3, 5, or 7 days after viral inoculation. Ganciclovir (200 micrograms/0.1 mL) was intravitreally injected 3, 7, or 10 days before HSV-1 inoculation, concurrent with viral inoculation, or 3, 5, or 7 days after viral inoculation. Eyes pretreated with HPMPC were protected from retinitis for 15-21 days. Ganciclovir did not protect completely even if administered 3 days before inoculation. Early treatment of established retinitis with HPMPC markedly delayed the progression of the infection. However, with ganciclovir there was delayed progression only in rabbits treated 3 days after viral inoculation. HPMPC had a remarkably potent and prolonged (< or = 1 month) antiviral effect in this retinitis model and may prove more useful than ganciclovir in local treatment of CMV retinitis.