Two experimental drugs promise to transform hepatitis C from a debilitating liver disease into a manageable condition for a majority of patients, researchers said Wednesday.
The new drugs work by blocking a key enzyme that the hepatitis C virus needs to make copies of itself and spread. They promise to revolutionize treatment for patients in much the same way as protease inhibitors did for HIV patients in 1995, experts said.
The two drugs, called boceprevir and telaprevir, nearly doubled the number of patients who achieve what is known as a sustained viral suppression — in effect, a cure — among those with new hepatitis C infections. For patients who did not respond to initial therapy or who suffered a relapse, the drugs tripled the odds of bringing the virus under control.
"This is opening up a new door" for treatment of hepatitis C, said Dr. Raymond Koff of the University of Connecticut School of Medicine in Farmington, who was not involved in the research.
The Food and Drug Administration is expected to approve both medications in May and, "once these drugs are available, doctors are going to be overwhelmed" by patients demanding them, said Koff, who is on the board of directors of Hepatitis Foundation International.
The results of two clinical trials with boceprevir were reported Wednesday in the New England Journal of Medicine. Similar results with telaprevir were expected to be reported Thursday at a meeting of liver researchers in Berlin.
The hepatitis C virus was discovered only in 1989, but it has clearly been around for a long time. An estimated 3.2 million Americans are infected by it, typically by transmission through blood. Infections may initially be asymptomatic, but eventually they include debilitating fatigue, liver disease (including fibrosis and scarring) and liver cancer. There is no vaccine against the virus.
Current therapy for infections involves treatment with the antiviral drugs peginterferon and ribavirin for as long as a year. Response rates are about 50% at best for those with hepatitis C genotype 1, the most common — and most difficult — form of the virus.
In one of the two trials reported in the New England Journal of Medicine, a team led by Dr. Fred Poordad of the Cedars-Sinai Medical Center in Los Angeles studied 1,097 patients with hepatitis C genotype 1 who had never been treated for the virus. All were given the two standard drugs for four weeks. Then one-third of the patients continued to receive only the standard drugs, while two other groups received different regimens of boceprevir in addition to the usual therapy.
Among patients in the boceprevir groups, 63% and 66% had a sustained suppression of virus, compared with 38% for patients who took only the standard.
In the second trial, a team headed by Dr. Bruce R. Bacon of the Saint Louis University School of Medicine studied 403 hepatitis C patients who failed an initial round of therapy with the two standard drugs or who suffered a relapse, using the same design as in the first study.
Among patients in the boceprevir groups, 59% and 66% had a sustained virus suppression, compared with 21% for those receiving only the standard drugs.
"This is a major breakthrough in treatment," especially for African Americans, said Dr. Sammy Saab, a hepatitis specialist at UCLA's David Geffen School of Medicine who was not involved in the research. Blacks respond much more poorly than whites to the existing treatments for hepatitis C, but the new drugs sharply reduce that disparity, he said.
Still, there are some side effects, said Dr. James Ou, a hepatitis specialist at USC's Keck School of Medicine who was not involved in the study. The biggest side effect is anemia, which is caused by ribavirin and exacerbated by boceprevir. Many patients had to be given the drug erythropoietin to stimulate red blood cell production, and some dropped out of the trial because of the anemia.
Also, boceprevir must be taken three times a day.
"But if the patients can tolerate it, then the chance of them being cured is up to 70% … that's a very big improvement," Ou said.
The boceprevir trials were sponsored by Merck & Co., which plans to sell the drug under the brand name Victrelis. Telaprevir is being developed by Vertex Pharmaceuticals, Tibotec Pharmaceuticals and Mitsubishi Tanabe Pharma.