Vertex Nears Hit or Miss

But first, here's why the drug has generated so much excitement already.

Telaprevir is designed to attack hepatitis C by inhibiting the protease enzyme, one of the key enzymes used by the virus to make copies of itself. This "direct antiviral" approach differs from current hepatitis C drugs, which work by boosting the body's immune system to tamp down and eliminate the virus.

A weekly injection of alpha interferon (Schering-Plough's (SGP Quote) PEG-Intron or Roche's(RHHBY Quote) Pegasys) combined with daily oral doses of a generic drug ribavirin is the current standard of care for hepatitis C patients. A normal treatment course for Type 1 hepatitis C (the most prevalent form) takes 48 weeks to complete. But only about half of patients are cured, and the side effects can be difficult to tolerate, including flulike symptoms, anemia and depression.

Vertex believes that adding telaprevir to the current standard of care will increase cure rates and shorten the length of treatment. Early clinical data have backed that view, although final proof will only come from longer studies in more patients. That's what Vertex intends to do with its PROVE 1 and PROVE 2 studies, which are being run in the U.S. and Europe, respectively.