[Recent advances in antiviral drugs--antiviral agents to HCMV, HHV-6, and HHV-7].

Foscarnet, Phosphonoformate, has recently approved for the treatment of HCMV retinitis in AIDS patients in Japan. It inhibits the viral DNA polymerase and effective against ganciclovir-resistant HCMV. Cidofovir, (S)-1-[3-hydroxy-2-(phosphonylmethoxy)propyl]cytosine, a new acyclic nucleotide phosphonate analogues has potent activity against HCMV retinitis in AIDS at 3-7.5 mg/kg/week, once/week with concomitant oral probenecid and saline prehydration to prevent nephrotoxicity. The highest potency and selectivity against HHV-6 and HHV-7 was demonstrated S2242 (N7-isomer of 6-deoxy-ganciclovir). Ganciclovir, foscarnet, and cidofovir also exhibited selective inhibitory activity to these viruses, although the activities were not so remarkable compared with in case of HCMV. Thymidine kinase-dependent drugs (acyclovir, brivudin) showed little, if any, activity. These results suggest a structural homology of the DNA polymerase and a lack of TK gene among these three beta-herpesviruses.