Moreover, most patients taking a 12-week course of telaprevir combination therapy were able to shorten the total length of their grueling treatment from 48 weeks to 24 weeks.
Because hepatitis C virus (HCV) rapidly becomes resistant to telaprevir, the drug must be given in combination with other antiviral treatments, and these treatments are continued for weeks after completion of telaprevir therapy.
All of the patients in the clinical trial were infected with HCV genotype 1 -- the most common U.S. strain, and the hardest to cure. Without telaprevir, less than half of patients with genotype 1 HCV achieve a cure.
In the world of hepatitis C treatment, "cure" is a relative term. Treatment does not necessarily eradicate the virus from the body. Successful treatment results in "sustained viral response (SVR)" or "viral cure," meaning that treatment has brought the virus to undetectable levels. Usually, the immune system is able to keep any remaining HCV under control after a viral cure.
About 9% of telaprevir-treated patients who achieved SVR relapsed -- that is, their HCV levels once again became detectable during post-treatment follow-up.
Testing Telaprevir's Effects
In the study, two groups received either eight- or 12-week courses of the telaprevir/interferon/ribavirin combination, followed by 12 or 36 more weeks of treatment with interferon/ribavirin. Those whose HCV became undetectable at weeks 4 and 12 got the shorter treatment course. A third group of patients got 48 weeks of standard interferon/ribavirin treatment.
Telaprevir increased the number of patients who dropped out of the trial because of side effects: from 3.6% in the control group receiving only standard therapy to 6.9% in those who took telaprevir for 12 weeks and to 7.7% of those who took telaprevir for eight weeks.
Telaprevir Not FDA Approved
Overall, researchers consider the study a huge success.
The study findings mark "what we believe may be a potentially dramatic improvement in the future treatment of hepatitis C," said Robert Kauffman, MD, PhD, chief medical officer for Vertex.
The study findings will be presented at a medical conference later this year. Also expected later this year are results from two other clinical trials of telaprevir, including one in patients for whom previous standard treatment failed.
Vertex expects to file for FDA approval of telaprevir in the second half of 2010.
Telaprevir inhibits the HCV protease enzyme. Another HCV protease inhibitor, Merck's boceprevir, also is in clinical trials. Merck plans to file for FDA approval of boceprevir in 2010.
Citing analyst reports, the New York Times estimates that the cost of telaprevir treatment will be tens of thousands of dollars.
The findings of this study should be considered preliminary as they were released by the drug manufacturer and have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.