A late-stage hepatitis C drug tested by Vertex Pharmaceuticals substantially shortened the amount of time needed to tackle the virus, minimizing the side effects usually associated with current treatments. The trial showed that three quarters of the people treated with the drug telaprevir showed undetectable levels of the virus following a 24 week course of treatment. By comparison, the current standard of care—using a long-acting interferon combined with another drug called ribavirin over 48 weeks—is only effective at clearing the virus in 40 percent to 50 percent of people treated.

The results are a promising sign for people struggling with the potentially life-threatening virus, which can result in progressive liver damage. By dodging some of the common side effects of current treatments, such as fatigue and flu-like symptoms, and reducing the length of treatment, the drug could potentially make treatment an easier and more tolerable experience for many patients.

The Centers for Disease Control and Prevention estimates there were 17,000 new hepatitis C virus infections in the United States during 2007 and that about 3.2 million Americans have chronic hepatitis C virus infection. As many as 180 million people are estimated to be infected with the virus worldwide, though many do not know it.

For patients in Vertex's 12-week telaprevir-based trial arm, the 8-week telaprevir-based arm, and the control arm, 68 percent, 66 percent and 9 percent, respectively, had undetectable levels of hepatitis C virus in their blood 4 weeks after the initiation of treatment.

The results appeared to be in line which what Vertex investors expected, barely moving the company's shares on May 25, the day the results were announced. Shares traded for $34.74 on Wednesday, up just 2.3 percent from Tuesday's close.

The positive results of Vertex's trial have set a high bar for Merck's boceprevir, for which late-stage trial results are expected later this year. Roche, InterMune and Bristol-Myers Squibb are also working on their own combination therapies.

Vertex, which is based in Cambridge, Massachusetts, plans to submit a new drug application to the FDA for telaprevir in the second half of 2010 for both HCV patients being treated for the first time and patients for whom other treatments have failed.