WEDNESDAY, Jan. 18 (HealthDay News) -- A new cocktail of two investigational drugs appears to have successfully cleared the hepatitis C virus in people who don't respond to standard treatment.

What's more, the approach seems to work without the need for injections with interferon alpha, an onerous medication that causes serious side effects in many patients.

Scientists from seven U.S. medical centers and drug maker Bristol-Myers Squibb published the small study in the Jan. 19 issue of the New England Journal of Medicine that is being heralded as "landmark" research.

"We saw a sustained virologic response -- the virus was undetectable in the patients -- during treatment and remained undetectable after the drugs were stopped," said study author Dr. Anna Lok, director of clinical hepatology at the University of Michigan Medical School in Ann Arbor.

Hepatitis C virus, spread through contact with contaminated blood, is the most common form of the virus and affects 180 million people globally, including 4.1 million Americans. It's the leading cause of chronic liver disease, and can lead to liver cancer. The standard treatment includes injections of the antiviral drug interferon alpha, which isn't tolerated well by everyone, said Dr. Andrew Muir, director of gastroenterology and hepatology research at the Duke Clinical Research Institute. Its many side effects include flu-like symptoms, fatigue, fever and depression.

"Many patients cannot complete treatment or decide not to take treatment because of interferon alpha," Muir said.

The study had two arms, said Lok. A group of 10 patients received four medications, including the two investigational drugs, the antivirals daclatasvir and asunaprevir, along with the standard treatment combination of interferon and ribavirin. The other arm of the study included 11 patients who received only the two investigational drugs. Both groups underwent treatment for 24 weeks.

The 10 patients on the four-drug regimen experienced a sustained virologic response with undetectable virus at the end of treatment and again at 12 weeks beyond their treatment, the researchers reported. In the two-drug group, four of the 11 patients also had undetectable levels of the hepatitis C virus in their blood 12 weeks after treatment ended.

All of the patients were infected with genotype 1, the most common type of hepatitis C virus in the United States, and had not responded to previous treatment with interferon and ribavirin, said Lok.

"The four-drug arm was very impressive. These patients had not shown a response before and now we get a 90 to 100 percent rate of sustained response," said Lok.

She said even though only four patients in the two-drug group reached a sustained response, this is the first study to show it can be achieved without interferon or ribavirin.

"Clearly, this is the biggest development in hepatitis C research in a very long time," said Dr. Raymond Chung, director of hepatology at Massachusetts General Hospital in Boston, who wrote an accompanying editorial in the same issue of the journal. "It has enormous implications for our ability to treat many more patients with regimens that are significantly more tolerable."

The most common side effects reported were headache, diarrhea, nausea and fatigue, the study authors said.

Chung called the study "a watershed moment" because it suggests that an interferon-free treatment is possible. "The conventional wisdom for quite some time has been that hepatitis C would likely not be curable without an interferon backbone."

Duke's Dr. Muir added, "The study is also exceptional because it included patients we would describe as the most difficult to treat." Their viral load did not go down very much when they underwent interferon and ribavirin treatment in the past.

The new drugs are not FDA-approved yet, but a number of trials are under way, said Chung, who believes an interferon-sparing regimen is only a few years away. "It is not beyond belief that we'll have an all-oral therapy available as early as 2015. That's the pace it's going right now," he said.

"There's certainly hope," said Lok, who noted that the research was funded by drug maker Bristol-Myers Squibb.

More information

The U.S. National Institutes of Health has more on clinical trials for hepatitis C.