Two experimental drugs promise to strengthen the current 2-drug treatment routine for hepatitis C – a chronic viral infection that could led to liver scarring and cancer.
About 3.2 million Americans have the disease, which has a cure rate of less than 40%. It spreads mostly through contact with blood, and up to 70% of people infected don’t even know they have it. The disease accounts for $33.3 billion in medical costs a year.
Well now, two new drugs – Merck’s boceprevir and Vertex’s telaprevir – that suppress the virus are expected to be approved by the Food and Drug Administration as early as May.
Patients would take one or the other in addition to the current 2-drug regime, which is a multiweek course of peginterferon and the antiviral ribavirin.
Both new drugs are for hepatitis C genotype 1, the most common yet hardest to treat of the strains. And they’re both protease inhibitors, which stall virus replication by thwarting specific protease enzymes.
The results of two phase III trials for boceprevir – funded by Merck, which plans to sell the drug under the brand name Victrelis – were published in the New England Journal of Medicine today. (Similar results for telaprevir are expected to be reported soon.)
Adding boceprevir to the current regimen allowed patients to suppress the virus. The effect, known as ‘sustained viral response,’ means they’re effectively cured.
One trial looked at 1,097 patients who have never been treated:
- After 44 weeks of adding boceprevir to the regimen, up to 68% of non-black patients were effectively suppressing the virus.
- Compared with the 38% of controls receiving only the standard drugs.
- The drug combo wasn’t as effective for black patients, but adding boceprevir still boosted the response from 23% to 53%.
The other trial looked at 403 patients who had taken the current 2-drug treatment but showed no improvement or relapsed:
- After 44 weeks, adding boceprevir resulted in sustained viral response rates in 66% of the patients.
- Compared to 21% in control patients.
But as with the current peginterferon-ribavirin treatment, researchers are concerned with possible resistance and side effects. Early studies have shown that resistant strains of the virus could pop up within just days, and adding boceprevir exacerbated the anemia caused by ribavirin.
However, the chance of patients being cured is up to 70%, and boceprevir and telaprevir are likely in the home stretch to reach potentially millions of hepatitis C patients in the US.
The next steps are to simplify the treatment regimen. “Everyone wants to get rid of interferon and ribavirin because both have toxicity that make them often difficult to tolerate,” says Stuart Gordon of Henry Ford Hospital who coauthored one of the studies.
There is no vaccine for hepatitis C, and sometimes the only treatment is a liver transplant.
The two new drugs promise to be comparable to the improvement in HIV therapy when protease inhibitors were added to drug cocktails for that disease in 1995.
Image: A.D.A.M. via NIH