WEDNESDAY, March 30 (HealthDay News) -- Adding the new drug boceprevir to the current two-drug treatment for hepatitis C appears significantly more effective than the standard therapy, according to two new studies.

The drugs now used to treat hepatitis C, a chronic liver disease, are the antivirals peginterferon and ribavirin (Copegus, Rebetol, RibaTab and Ribasphere). Combining them with the not-yet approved drug boceprevir increased the response rate, researchers say.

Merck, the manufacturer of boceprevir, funded both studies, which are published in the March 31 issue of the New England Journal of Medicine.

"Boceprevir, a protease inhibitor, along with peginterferon and ribavirin increases response rates in previously untreated patients," said Dr. Raj Reddy, co-researcher of one of the studies and director of hepatology and medical director of liver transplantation at the University of Pennsylvania in Philadelphia.

"Also, with this new strategy you have the potential of reducing the duration of therapy, from 48 weeks to 28 weeks," he added.

"We have turned the corner, a bit, and we have a combination treatment that is likely to be more effective in more people," he said.

For his study, 1,097 people, 159 of whom were black, who had not been treated for hepatitis C were randomly assigned to one of three groups. All groups were treated with peginterferon and ribavirin. After four weeks, one group also received a placebo for 44 weeks; another group had boceprevir added to their treatment for 24 weeks. The third group was given the three drugs for 44 weeks.

Among non-black patients, 40 percent achieved a sustained response to standard care. But as many as 68 percent of those also receiving boceprevir achieved sustained response at 28 weeks, the researchers found.

For black patients, the response rate was 23 percent for those receiving standard care and up to 53 percent with the addition of boceprevir.

The most severe side effect was anemia, which was seen in 13 percent of those receiving standard care and in 21 percent of those receiving all three drugs, Reddy's team noted.

In the other study, a group led by Dr. Bruce R. Bacon, director of the gastroenterology and hepatology division at St. Louis University Health Sciences Center, tested boceprevir on 403 patients with chronic hepatitis C. These patients had been previously treated with peginterferon and ribavirin.

Again, patients were divided into three groups similar to those in the other study. For those receiving boceprevir, the response rate was as high as 66 percent, compared with 21 percent for those receiving only peginterferon and ribavirin, the researchers found.

For patients who had no detectable hepatitis C RNA, the response rate to boceprevir was as high as 88 percent, the researchers noted.

As in the other study, anemia was the most serious side effect, affecting up to 46 percent of those taking boceprevir and 21 percent of those on standard care.

"The addition of boceprevir to peginterferon-ribavirin resulted in significantly higher rates of sustained virologic response in previously treated patients with chronic HCV (hepatitis C) genotype 1 infection, as compared with peginterferon-ribavirin alone," the authors concluded.

Commenting on the studies, Dr. Donald M. Jensen, a professor of medicine at the University of Chicago Medical Center and author of an accompanying journal editorial, said "there is a significant improvement in sustained response [with boceprevir], which really relates to cure of hepatitis C."

Jensen noted that a similar drug is also being tested. "These drugs will offer patients a significant advantage over current therapy," Jensen said.

Hepatitis C affects at least 3.2 million Americans, according to the U.S. Centers for Disease Control and Prevention. More than 12,000 people die each year from liver disease and cancer caused by hepatitis C. There is no vaccine for hepatitis C, the researchers note.

Many people with hepatitis C are symptom-free and don't know they are infected, Jensen said. When symptoms do appear, it can be too late to treat the disease effectively, and the only option then is a liver transplant, he added.

More information

For more information on hepatitis C, visit the U.S. National Library of Medicine.