New Data On Antiherpetics Presented At ICAAC

New data presented at the 34th Interscience Conference on Anti-microbial Agents and Chemotherapy in Orlando, Florida, have provided further insights into the rational use of two new antiviral drugs, SmithKline Beecham's Famvir (famciclovir) and Wellcome's aciclovir follow-up Valtrex (valaciclovir). The studies include what is believed to be the first comparison between the two agents in the treatment of Herpes simplex infections.

In an animal model which simulates chronic HSV infection in the immunocompromised patient, famciclovir and valaciclovir were studied for their effectiveness in suppressing viral replication during and after antiviral therapy. Once-daily oral therapy with valaciclovir and famciclovir for five-10 days was equally effective in reducing viral replication, but twice-daily dosing revealed that famciclovir was more effective in reducing viral titers. Titers fell below the limit of detection after two days of famciclovir treatment and after five days with valaciclovir. After cessation of famciclovir therapy, prolonged suppression of viral replication was observed in the skin and central nervous system with no recurrence of infectious virus detectable after the five- or 10-day post-treatment period. In contrast, on cessation of valaciclovir treatment infectious virus reappeared at both tissue sites within two days.

These data may suggest a differing mode of action for famciclovir and valaciclovir in affecting virus pathogenesis, but it remains to be seen (and some researchers questioned by the Marketletter were sceptical) whether any differences will be observed in head-to-head clinical comparisons of the two agents.