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(Reuters) - Biotechnology company Gilead Sciences on Monday said two trials of its hepatitis C drug, the centerpiece of its oral hepatitis C treatment program, met their goals in two late-stage studies.
The results are expected to be used to support the company's regulatory filing seeking approval in the United States. Industry analysts say the market for such drugs could reach $25 billion by 2020.
An estimated 4 million Americans have the virus, with 170 million infected worldwide.
Gilead's hepatitis C drugs program is considered among the most advanced of many companies racing to bring an interferon-free treatment regimen to market. The newer hepatitis C drugs, while doubling the cure rate of prior treatments, must still be taken with interferon, which causes miserable flu-like symptoms that lead many patients to discontinue or put off treatment.
Gilead, widely seen as a front runner in a crowded field, paid about $11 billion last year to acquire Pharmasset, the company that developed the drug.
Both studies, dubbed Fission and Neutrino, tested the drug for 12 weeks in patients who have chronic hepatitis C virus (HCV) infection and have never been treated for it.
The Fission study evaluated once-daily nucleotide sofosbuvir in combination with ribavirin. The Neutrino study combined nucleotide sofosbuvir with ribavirin and pegylated interferon.
In the Fission study, patients with HCV infection were selected at random to receive either a 12-week course of sofosbuvir plus ribavirin (RBV), or standard of care with 24 weeks of pegylated interferon alfa-2a (peg-IFN) plus RBV.
The study met its primary goal, showing that the experimental treatment, sofosbuvir plus RBV, was just as good as the standard treatment, peg-IFN plus RBV. In the study, 67 percent of patients achieved a sustained virologic response in the sofosbuvir plus RBV treatment group, versus 67 percent in the peg-IFN plus RBV treatment group.
Common adverse events - fatigue, headache, nausea, insomnia and dizziness - occurred more frequently in patients receiving peg-IFN and RBV, compared with those receiving sofosbuvir and RBV.
In the Neutrino study, patients were given sofosbuvir, RBV and peg-IFN. This study met its primary goal of achieving superiority, with 90 percent of patients in the study group showing a sustained response versus a 60 percent cure rate for RBV and peg-IFN based on historical expectations.
The most common adverse events that occurred in about 20 percent of patients in the Neutrino study were fatigue, headache, nausea, insomnia and anemia.
Gilead shares were off 86 cents at $39.70 in midday trading on the Nasdaq, tracking a broadly weaker stock market.
Some investors may view the trial results as initially disappointing because they highlight the perils of extrapolating efficacy directly from small, carefully conducted phase II trials to the larger population involved in phase III trials, noted Bernstein analyst Geoff Porges.
But he said he was confident the data will support the regulatory filings.
"We regard the results positively, as the company's key HCV medicine is further de-risked, and the drug should be approved by year-end 2013 with a profile that remains better than both incumbent antivirals (Incivek and Victrelis) and also its next two rivals," Porges wrote in a research note.
The rivals he referred to are Bristol-Myers Squibb's daclatasvir and Johnson & Johnson's JNJ's simeprevir, or TMC435.
Reporting By Debra Sherman; Editing by Maureen Bavdek and Dan Grebler