Gilead Sciences has presented promising top-line results from a Phase III trial investigating a combination treatment for hepatitis C virus based around its experimental drug sofosbuvir.

After a 12-week course of once-daily sofosbuvir plus ribavirin in patients with genotype 2 or 3 chronic HCV infection who are not candidates to take interferon, the study found that 78% of patients remained clear of the virus 12 weeks after completing therapy. The safety profile of sofosbuvir was similar to that observed in previous studies, Gilead said, and there were few treatment discontinuations due to adverse events.

The trial, called Positron, is the first of three Phase III studies to be completed that are evaluating sofosbuvir therapy in HCV genotype 2 or 3 infected patients. Gilead's R&D chief Norbert Bischofberger, said that "achieving a sustained virologic response in three-quarters of patients is an impressive result for a sofosbuvir-based, all-oral treatment in a group of individuals for which no suitable alternative therapy exists". He added that data from other Phase III studies will be presented in early 2013 and the first regulatory filings for sofosbuvir are scheduled by mid-2013.

Sofosbuvir (formerly known as GS-7977) is a once-daily nucleotide analogue polymerase inhibitor and is also being studied as a once-daily fixed-dose combination containing the NS5A inhibitor GS-5885 for genotype 1 infected HCV patients.