(AP) -- Federal health officials say a highly anticipated hepatitis C drug from Vertex Pharmaceuticals successfully treats a clear majority of patients in less time than older medicines that have been used for 20 years.

The posted its review of Vertex's telaprevir ahead of a meeting Thursday where outside experts will vote on the benefits of the drug. On Wednesday the experts will review a similar drug from Merck.

Both new drugs work by blocking the enzyme protease, which allows the hepatitis virus to reproduce. The new approach represents a breakthrough from older medicines, which are designed to help the fight hepatitis.

FDA scientists said 79 percent of patients who added telaprevir to older medicines were virus free six months after treatment.