Treatment for Hepatitis C Genotype 2
Infecting an estimated 170 million people worldwide, the Hepatitis C virus is a leading cause of chronic liver disease. Treatment for Hepatitis C has recently improved with the addition of two U.S. Food and Drug Administration (FDA)-approved medications; however, many don’t realize that the improved triple drug regimen is primarily intended for infection with Hepatitis C genotype 1. For those with Hepatitis C genotype 2, the standard treatment remains pegylated interferon and ribavirin – a drug combination that is intolerable for many people.
The Hepatitis C genotype describes the viral strain, and does not change after initial infection. There are 6 genotypes of Hepatitis C, half of which are common in the United States. The strains typically encountered in the U.S. are:
- Hepatitis C genotype 1
- Hepatitis C genotype 2
- Hepatitis C genotype 3
Differentiation is important because treatment responses and, thus medication recommendations, are different for each genotype. Because nearly three quarters of infected Americans have Hepatitis C genotype 1, this strain is the primary recipient of pharmaceutical research efforts. Constituting the next largest proportion of Hepatitis infections in the U.S., at least 10 percent of those with Hepatitis C have genotype 2.
Before protease inhibitors were added to the standard Hepatitis C treatment duo of pegylated interferon and ribavirin, the response rates between genotype 1 (g1) and genotype 2 (g2) were dramatic:
- Hepatitis C g1 was considered to be the hardest to treat with a 50 percent success rate on interferon and ribavirin treatment.
- Hepatitis C g2 was considered to be a better strain to be infected with since interferon and ribavirin helped 65 to 80 percent of those infected clear the virus.
- Another advantage of Hepatitis C g2 was that the course of treatment was typically half the amount of time required to treat Hepatitis C g1.
However, adding a third drug (a protease inhibitor) to Hepatitis C treatment has substantially improved the success odds for treating g1. The protease inhibitors attack the Hepatitis C virus directly and keep it from reproducing. Those with Hepatitis C g1 receiving treatment for the first time now have a 75 to 80 percent chance of clearing the virus on the triple drug regimen, comparable to the success rates for g2 on just interferon and ribavirin.
Unfortunately, the two protease inhibitors on the market, Victrelis (boceprevir) and Incevik (telaprevir), are approved to be combined with pegylated interferon and ribavirin – only for Hepatitis C g1. Omission of Hepatitis C g2 from triple drug therapy has prevented any major advances for this viral strain. However, research to improve treatment for g2 is finally catching up. The potential exists for off-label use of one of the protease inhibitors and improved treatments for all Hepatitis C genotypes appear to be on the rapidly-approaching horizon. Examples include:
- Data from a small, single, randomized trial suggest some efficacy of telaprevir against Hepatitis C g2.
- Still in development, the nucleotide analogue polymerase inhibitor PSI-7977 by Pharmasett demonstrated an extremely high efficacy against Hepatitis C g2 – without interferon.
For those with g2 waiting for advances in treating their Hepatitis C strain, the possibility of adding telaprevir to Hepatitis C treatment or a future approval of PSI-7977 may seem overly hopeful. Nonetheless, the medical community is finally recognizing the need for improving Hepatitis C treatment for all genotypes – including genotype 2.
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