In the phase IIa trial evaluating Idenix' lead drug candidate valopicitabine, patients are randomized to one of two treatment arms, valopicitabine (NM283) monotherapy, or valopicitabine (NM283) plus pegylated interferon. This interim data analysis found that the patients receiving the combination of NM283 and pegylated interferon achieved a mean reduction of serum hepatitis C virus (HCV) RNA of 99.94% at week 12. "In patients infected with HCV genotype 1 - a difficult-to-treat strain of hepatitis C virus - virologic response to the current standard therapy of ribavirin and interferon is inconsistent," commented Dr Nathaniel Brown, Idenix's executive vice president of clinical development and chief medical officer. "However, the consistency of response to the combination of valopicitabine and interferon appears promising". Based on the encouraging interim data, Idenix has extended the phase IIa trial to six months in order to investigate longer duration treatment.