MONDAY, Aug. 9 (HealthDay News) -- The current two-drug standard treatment for the potentially lethal hepatitis C could be rendered nearly twice as effective if doctors added in a third antiviral medication called boceprevir, new research suggests.

The finding might help the estimated 170 million people worldwide who are infected with this particular type of hepatitis C (genotype 1), the study authors say, given that the liver infection is difficult to treat.

The study, funded by Merck, the maker of boceprevir, was reported online Aug. 8 in The Lancet.

According to the researchers, led by Dr. Paul Y. Kwo of Indiana University School of Medicine in Indianapolis, the standard two-drug treatment of pegylated interferon plus ribavirin prompts the desired virological response in less than half of patients.

Searching for a way to improve these outcomes, the Indiana team launched a two-phase trial involving 520 hepatitis C patients in 67 sites across the United States, Canada and Europe. Patients received one of several drug cocktails of various strengths for upwards of 48 weeks. Some of the drug combinations included boceprevir, while some did not.

Irrespective of other factors -- including attempts to reduce the length of treatment or the amount of standard medications given to patients -- adding boceprevir to the mix appeared to consistently boost viral response, Kwo and his colleagues reported.

However, the effectiveness of the three-drug regimen was undercut somewhat when the team lowered the amount of ribavirin the patients received.

In a news release from the journal, the team concluded that, "boceprevir, in combination with pegylated interferon and ribavirin, achieves high (virological response) rates with 28 weeks of therapy in most patients, and is safe and effective for use up to 48 weeks in the few patients who benefit from longer duration of therapy." They also noted "increased response rates in difficult-to-treat groups, including black participants and those with cirrhosis."

In a journal commentary, Drs. Laura Milazzo and Spinello Antinori of the Universita degli Studi de Milano in Milan, said that the addition of the third drug "substantially improved the proportion of sustained virological responses, although not to the desired proportion."

They also noted that about a quarter of blood samples taken from the patients showed signs of viral resistance against boceprevir. Milazzo and Antinori say that a number of questions, including drug-drug interactions and the role of genetics in predicting patient outcomes, also need to be considered.

Dr. Eugene Schiff, director of the center for liver disease at the University of Miami School of Medicine, was enthusiastic about the current effort to improve hepatitis C treatment, and said that he expects more to come.

"Boceprevir is one of two protease inhibitors that we are anticipating will be licensed within the next year," he said. "And when coupled with the standard-of-care right now, these drugs should double the success rate in terms of the sustained viral response rate, which equates with cure in patients who have never been treated before."

Schiff added that even some patients who have undergone and failed to improve following a standard treatment regimen may be able to benefit from a second round of treatment with such protease inhibitors.

"So there is no question this a major advance in our current treatment of Hep C," Schiff said. "And it's the first of what we can anticipate in terms of the use of what we call direct antivirals. There are many studies ongoing regarding this, but the point to make is that this field is really advancing."

More information

Find out more about hepatitis C infection at the U.S. National Institute of Diabetes and Digestive ... Kidney Diseases.