Like Victrelis, also approved this month, Incivek greatly boosts the chances that hepatitis C treatment will result in a cure -- that is, a "sustained viral response" or SVR. Although hepatitis C virus (HCV) may not be totally eliminated, an SVR essentially means a person will never have to worry about developing complications of hepatitis C disease.
Standard treatment with interferon and ribavirin lasts 48 weeks, yet results in an SVR for fewer than half of patients. In clinical trials, adding Incivek to this regimen boosted SVR rates 20% to 45%.
Moreover, most patients taking Incivek will have to tolerate the side effects of the triple combination therapy for only 24 weeks.
Earlier this month, an FDA advisory panel enthusiastically recommended approval of Incivek and Victrelis.
Incivek and Victrelis both target the HCV protease enzyme, making it nearly impossible for the virus to replicate. Although the virus quickly becomes resistant to either drug used alone, combination therapy with interferon and ribavirin keeps HCV in check.
"With the approval of Incivek, there are now two important new treatment options for hepatitis C that offer a greater chance at a cure for some patients with this serious condition," Edward Cox, MD, MPH, director of the FDA's office of antimicrobial products, says in a news release.
Incivek and Victrelis increase the already difficult side effects of standard therapy -- particularly anemia -- but they do not have to be taken for the full 48 weeks of standard therapy. And there's evidence that patients who have a strong early response to the drugs may be able to shorten the grueling course of treatment.
Incivek is given for the first 12 weeks of combination treatment. Interferon/ribavirin treatment lasts a total of 48 weeks, although early responders may be able to stop at 24 weeks.
Incivek has two major side effects: It increases the anemia seen with interferon/ribavirin, and it causes an itchy rash in more than half of patients. Other side effects include nausea, fatigue, headache, diarrhea, and anal or rectal irritation and pain.
The clinical trials that led to the Incivek reported somewhat higher cure rates than the trials that led to Victrelis' approval. But the two drugs have never been tested head to head, so it's impossible to say for sure whether one works better than the other.
A major marketing battle is expected between Merck and Vertex. Although each of the drugs is a major advance over current hepatitis C therapy, even better treatments are in the pipeline.
New polymerase inhibitors promise to make combination treatment even more effective -- and may even allow some patients to avoid the interferon/ribavirin combination. But such drugs are at least three years away from the marketplace.