Prospects for hepatitis C virus therapeutics: levovirin and viramidine as improved derivatives of ribavirin.

Ribavirin, in combination with interferons, has proved clinically useful for the treatment of hepatitis C virus (HCV) infection despite uncertainty as to its true mechanism of action. Its immunomodulatory effects have been proposed to be crucial for its efficacy in HCV treatment. Two new derivatives of zibavirin, Levovirin and virmidine, are currently in development as HCV therapeutics. Both drugs retain ribavirin's immunomodulatory properties but appear to be less toxic than the parent drug. Clinical evaluation of these drugs may aid in understanding the relevant mechanism of action of ribavirin itself, as well as the role of immunomodulators in HCV therapy.