An experimental antiviral agent called boceprevir doubled the cure rate for hepatitis C in a small phase 2 clinical trial designed to show efficacy, researchers reported Sunday. The drug will now be submitted to the larger Phase 3 trial required for approval of the drug by the Food and Drug Administration.
Hepatitis C is a chronic viral infection that affects an estimated 170 million people worldwide, leading eventually to cirrhosis and liver cancer if not controlled. The standard treatment now is a 48-week regimen of pegylated interferon, which boosts the immune system, and the antiviral agent ribavirin, which is a general-purpose antiviral agent. But the combination cures less than half of those who receive it and, for reasons that are not clear, is even less effective in African Americans. The most difficult strain to treat is the so-called genotype 1, which is the strain infecting about 70% of Americans.
Boceprevir, originally developed by Schering-Plough, which was recently purchased by Merck, is designed to attack the protease enzyme used by the hepatitis C virus to replicate. In that sense, it is analogous to the protease inhibitors, such as saquinavir and ritonavir, that revolutionized HIV treatment when used in conjunction with other AIDS drugs.
Dr. Paul Y. Kwo of the Indiana University School of Medicine and his colleagues studied 520 patients with genotype 1 hepatitis C who had not previously received drug treatment. They were divided into five groups that received various combinations of the drugs. No placebos were used, and patients and physicians knew which patients received which drugs.
Only 38% (39 of 104) patients receiving standard therapy had no signs of the virus at the end of 48 weeks, the team reported in the international medical journal the Lancet. In contrast, 75% (77 of 103 patients) of those who underwent a four-week induction period with interferon and ribavirin followed by 44 weeks of treatment with all three drugs were virus free. The induction period is designed to boost the immune system and lower virus count to prevent the development of resistance to beceprevir. Those in the other treament regimens had intermediate levels of virus clearance. Improvements were also noted in the treatment of of blacks and those who had already developed cirrhosis.
Slightly more than half of the patients (55%) receiving boceprevir developed anemia, compared with 34% of those receiving only standard care. About 27% of the boceprevir patients had a distortion of their sense of taste, compared with 9% of those in the standard care group.
The study was funded by Merck.
-- Thomas H. Maugh II