Gilead's sofosbuvir clears another HCV hurdle

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Evidence continues to mount suggesting Gilead's experimental drug for hepatitis C virus could flip the current HCV treatment paradigm on its head.

Results of the Phase II trial, sponsored and led by the National Institutes of Health, suggest that a regimen of sofosbuvir and ribavirin was highly effective in clearing the virus and well tolerated in two difficult-to-treat groups—patients with severe liver damage and African Americans. Both groups were comprised of those with genotype-1 HCV, which accounts for 70% of all HCV infections.

The findings among patients with genotype 1, which appear in the current issue of JAMA, come on top of data showing strong efficacy for sofosbuvir in cohorts with genotypes 2 and 3. As such, analysts say the drug is poised to take the lion's share of the HCV market. A recent forecast from FactSet Research Systems put annual sales of sofosbuvir at $6.4 billion by 2017.

In the current study, of the 60 enrolled volunteers, 50 were African American (88% of whom suffer from genotype 1 and are known to be harder to treat with interferon-based therapies).

The bifurcated study broke out one group of 10 people with liver fibrosis. Fibrosis is part of the scarring process and represents the liver's response to injury.They received sofosbuvir and ribavirin. After 12 weeks of therapy, HCV was no longer present in all volunteers who completed therapy (nine out of 10).

The other group consisted of 50 volunteers, including 13 with serious liver damage. They received sofousbuvir and either a dose of ribavirin based on weight or a low-dose ribavirin. From that group, 17 patients had no detectable levels of the virus 24 weeks after treatment stopped. Of the 22 volunteers who received the low-dose ribavirin, 12 were considered cured after the end of treatment.

In an NIH press release, researcher Dr. Shyam Kottilil summed up the findings, saying, “We saw an overall cure rate of about 70% using regimens that did not include interferon. This is an encouraging result, especially considering the proportion of volunteers who had characteristics…that are recognized as predictors of poor response to treatment.”

The findings could make it harder for other prospective all-oral treatment regimens. Boehringer Ingelheim unveiled Phase II data earlier this month of its HCV combo of faldaprevir and deleobuvir, reporting high efficacy rates—85% in genotype 1b—but the sample did not include African Americans.

Gilead's new drug application for sofosbuvir was filed in April. This initial application, under priority review, is for use in genotypes 2 and 3, and in the treatment-naïve for types 1, 4, 5 and 6.

FDA expects to review the application by December 8, the agency said. The European Medicines Association, too, has given sofosbuvir an “accelerated assessment,”and if approved the drug could become available by the first half of next year.

ISI Group analyst Mark Schoenebaum, in an investor note issued around the time of the FDA filing, wrote that “Gilead should be ready to launch an oral genotype 1 regime around the end of 2014.”

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