Approved by the fda, telaprevir and boceprevir usher in a new era of treatment
by Larry Buhl
The first breakthrough treatments for liver disease to be approved in twenty years are about to hit the market, giving new hope for the most difficult-to-treat patients with the hepatitis C virus (HCV).
In May the FDA approved boceprevir, to be marketed as Victrelis by Merck & Co., and telaprevir, to be sold in North America by Vertex Pharmaceuticals under the name Incivek. Both drugs are targeted at patients who have some liver damage from hepatitis C who either have not been treated, or were not cured by other drugs.
Current standard HCV therapy—forty-eight weeks of ribavirin (Rebetol, Copegus) plus Pegasys (pegylated interferon alfa-2a) or PegIntron (pegylated interferon alfa-2b)—stimulates the immune response in people with HCV. Telaprevir and boceprevir are direct-acting antiviral agents that attack the virus itself by blocking an enzyme that helps it reproduce. Patients on Incivek take two pills three times per day; patients on Victrelis take one pill three times a day. The new drugs are, in most cases, not meant to be replacements for ribavirin and pegylated interferon, but will likely be prescribed in combination with these traditional HCV drugs.
For people with HIV and hepatitis C, the benefits of the new drugs are not clear yet. Experts say more research needs to be completed before clinicians will feel comfortable prescribing Incivek or Victrelis to people with HIV. Both drugs are in Phase II clinical trials for people who are co-infected with HIV and HCV.
For patients with only HCV, trials showed both drugs contributed to a higher sustained virologic response (SVR) when combined with traditional HCV drugs than could be produced with the traditional HCV drugs alone. People who achieve SVR—generally considered a cure—reduce their risk of developing liver cirrhosis and liver cancer.
Phase III clinical trials showed that adding boceprevir or telaprevir to standard HCV treatment raised cure rates from about forty to forty-five percent to about sixty-five to eighty percent for the hardest to treat HCV sufferers, genotype 1.
Subgroups in genotype 1 are “relapsers,” who either were treated but experienced a relapse, “partial responders,” whose treatment brought the virus to a lower but still detectable level, and “null responders,” who experienced no significant reduction in HCV viral load with previous therapy.
In the RESPOND 2 trial, boceprevir, in combination with pegylated interferon plus ribavirin, produced higher SVR rates than standard therapy alone for all genotype 1 subgroups. The likelihood of SVR for genotype 1 prior null responders was around sixty percent with boceprevir plus pegylated interferon and ribavirin compared to about twenty percent with standard therapy alone. For partial responders, cure rates approached seventy percent with boceprevir combination therapy versus about forty percent with standard treatment alone. Previous relapsers had SVR rates of up to seventy-five percent on boceprevir triple therapy, while previous non-responders had sustained response rates of forty to fifty-two percent.
The REALIZE trial for telaprevir showed tremendous potential for that drug as part of an HCV treatment regimen. Results showed telaprevir in combination with standard HCV treatment significantly improved outcomes in three categories of genotype 1 hepatitis C patients who had failed standard treatment, In that study, genotype 1 non-responders ranged from eighty-six percent SVR for relapsers (versus twenty-two percent with a second course of standard therapy alone) to thirty-two percent SVR for prior null responders.
The side effects of both drugs are few and manageable, according to REALIZE head researcher, Zobair Younossi, MD, of the Center of Liver Diseases at Inova Fairfax Hospital in Virginia. “There were a few subjects on telaprevir who had anemia and/or rashes—four percent with telaprevir alone, and three percent with combination therapy.” Dr. Younossi presented the study findings in Digestive Disease Week.
Both telaprevir and boceprevir will change the face of HCV treatment, but they will also make treatment somewhat more complicated, Younossi told A&U. “There will have to be programs and guided seminars for gastroenterologists. There are many experts involved in these trials and I hope they will provide education to other doctors.”
Vertex and Merck say there are expanding their public awareness and patient education efforts, as well as a patient assistance program to help eligible patients obtain access to the new drugs. Vertex says it will give Incivek for free to people with no health insurance and annual household income of less than $100,000. It will also cover some co-pay or co-insurance costs.
Full Victrelis prescribing information is available at
Full Incivek prescribing information is available at www.vrtx.com/current-projects/approved-medicines/incivek.html
Larry Buhl wrote about hepatitis B and HIV coinfection in the May issue.