Gildead Sciences has just announced that its experimental hepatitis C drug, called sofosbuvir, successfully met its primary efficacy endpoint in a fourth pivotal phase 3 study called FUSION.

The drug, an oral nucleotide inhibitor of HCV polymerase, performed very well in the late-stage trial testing. It was administered along with the medication ribavirin in a 12 and 16 week course of therapy for patients with genotype 2 or 3 chronic hepatitis C virus (HCV) infection who did not respond to previous treatment options, such as interferon – a common HCV drug which is unable to halt progression of the disease in certain patients.

The HCV genotype 2 or 3 patients – all of whom did not respond to interferon-based therapy – were randomly put into either a 12 week or 16 week course of 400 mg of sofosbuvir plus 1000-1,200 mg of ribavirin, taken daily.

After 12 weeks of therapy 50 percent of the patients showed no detectable HCV infection. After 16 weeks, this increased to 73 percent, meaning that the drug successfully met the endpoint criteria required.

Norbert Bischofberger, PhD, Executive Vice President of Research and Development and Chief Scientific Officer, said:

“This study demonstrates that all-oral therapy with sofosbuvir provides significant efficacy among difficult-to-treat hepatitis C patients who could not be cured by prior regimens containing pegylated interferon and now have limited treatment options.

With positive results from all four Phase 3 trials now in hand, Gilead is on track to meet its goal of filing regulatory applications in the United States and Europe in the second quarter.”

None of the patients discontinued the treatment because of adverse events. However, some the most common side effects – which were reported in less than fifteen percent of patients – included: headache, fatigue, nausea, and insomnia.

An initial regulatory filling for sofosbuvir will be supported by the results for this study, as well as from all the previous late-stage studies (POSITRON, FISSION, and NEUTRINO) where the drug showed promise among patients who weren’t able to receive interferon treatment.

The results support a prior study conducted by Boehringer Ingelheim, which found an interferon-free combination of two investigational compounds, the once-a-day protease inhibitor BI 201335 and the polymerase inhibitor BI 207127, was successfully able to sustain viral response in HPV patients.

Written by Joseph Nordqvist