A new antiviral drug that recently won federal approval to treat hepatitis C can effectively cure most patients of the infectious disease, which for more than 20 years has been notoriously difficult to treat, according to two studies released today.

Roughly 80 percent of patients with the most common strain of hepatitis C and who had either never undergone treatment before or had suffered a relapse were cured when they took the antiviral Incivek in addition to the standard drugs, according to one study led by researchers at California Pacific Medical Center and published in the New England Journal of Medicine.

That is a marked improvement over the previous treatment, which cured less than half of those patients. Most patients in the study were able to stop treatment after 24 weeks instead of the standard 48 weeks - a significant change, because the drugs can have brutal side effects.

"This is going to change the field of hepatitis C dramatically," said Dr. Natalie Bzowej, a liver disease specialist at California Pacific Medical Center who was a lead researcher in the study. "The treatment may not be easier, but it does have a higher chance of cure. And side effects are a lot more tolerable if you have them for a shorter period of time."

What 'cure' means

Hepatitis C is a viral infection that is transmitted through the blood, similar to HIV. Like HIV, it has long carried a stigma that can prevent people from being screened for the virus or seeking treatment. Patients are considered cured of hepatitis C when the virus is no longer detectable in their blood, but it is possible for traces of the virus to remain, and people may have relapses.

About 4 million Americans are thought to be infected with hepatitis C, although public health officials believe 75 percent of them don't know it. New cases of hepatitis C are decreasing year to year, but Baby Boomers are thought to be a large reservoir of the disease. They were more likely than other generations to have been exposed to the virus, through anything from intravenous drug use in the '70s to blood transfusions in the '80s, when the nation's blood supply was much less protected.

Risk of liver cancer

Hepatitis C typically affects only the liver, and symptoms often don't become apparent until liver damage has started. One in 10 people infected with hepatitis C is able to lose the virus without any medical intervention. The remaining people have chronic hepatitis C, although about 80 percent of them will never suffer serious symptoms.

But in up to 20 percent of chronic patients, hepatitis C causes severe liver damage and can lead to liver cancer. The infection kills about 10,000 people every year in the United States, and it's the leading reason for liver transplants.

"You're talking about a disease that affects millions of people, and now we can more than double the response rate to medication. This is a very big deal," said Dr. Joanna Ready, chief of gastroenterology at Kaiser Santa Clara, who handles all of the hepatitis C cases there.

Incivek and an antiviral called Victrelis were approved by the U.S. Food and Drug Administration last month to treat people with the most common strain of hepatitis C. Both drugs are used in conjunction with the previous standard treatment for hepatitis C.

Difficult therapy

That treatment is a toxic cocktail of weekly intravenous chemotherapy drugs and an older antiviral that patients took for at least 48 weeks - if they could tolerate the side effects, which included flu-like symptoms, anemia and depression. The treatment didn't reach the hepatitis C virus specifically, but boosted the patient's immune system to help it fight off the infection.

But the treatment was effective only about 46 percent of the time, and if people underwent the drug therapy once without success, their chances of a cure if they tried again were slim - only about 5 percent if the earlier treatment didn't work at all.

"There was a danger I could actually die from the treatment," said Orlando Chavez, who was successfully treated for hepatitis C eight years ago and now is the hepatitis coordinator for the Berkeley Free Clinic. "I think I slept pretty much through the treatment. I staggered to the clinic once a week and took my pills every day and basically hibernated for a year."

Chavez said he's thrilled with the data he's seen on the new antiviral therapy. The antivirals bump up the chances of a cure to 79 percent for those who have never been treated, according to the recent studies, which looked at almost 2,000 hepatitis C patients. People who had been treated once and relapsed had an 86 percent chance of being cured. And those who hadn't responded at all to earlier treatment had a 32 percent chance of a cure - a sixfold improvement.

Less time in treatment

There's evidence that the antivirals magnify the side effects in some patients, in addition to sometimes causing a serious rash. But because the antivirals vastly improve the success rate and, in many cases, cut down the amount of time people have to take the drugs, the side effects may be easier for patients to deal with, doctors say.

"Even more scrupulous monitoring of the patient is required" because of the serious side effects, Ready said. "But you do get much more bang for your buck when you add either of these (antiviral) agents in."