Schering-Plough drug results pressure Vertex stock

BOSTON (Reuters) - Schering-Plough Corp (SGP.N: Quote, Profile, Research, Stock Buzz) said on Monday that results from a study of its experimental hepatitis C drug showed promising results, sending the shares of rival Vertex Pharmaceuticals Inc (VRTX.O: Quote, Profile, Research, Stock Buzz) down nearly 11 percent.

Schering's drug, boceprevir, is the closest competitor to Vertex's experimental hepatitis C drug telaprevir and, although

Vertex is further ahead in development, investors are closely watching the competitive landscape.

Analysts said data from the mid-stage boceprevir trial was better than expected in patients who have not received previous treatment and a reminder that Vertex, while still in the lead, has rivals nipping at its heels.

Schering-Plough's shares rose nearly 3 percent to $20 in afternoon trading.

The company said interim analysis of a mid-stage trial showed that at 48 weeks, 74 percent of patients receiving boceprevir in combination with standard treatment had undetectable levels of the hepatitis C virus in their blood for a sustained period of time, compared with 38 percent of patients receiving standard treatment alone.

The results were achieved by first giving patients a four- week "lead-in" time where they received the standard current treatment alone.

The company also tested a group of patients who did not receive "lead-in" treatment. In those patients, 66 percent saw the virus eliminated from the blood-stream.

Analysts said the results were solid, but most held to their view that Vertex's drug holds the commercial advantage since telaprevir requires a shorter period of treatment and appears to be more effective in patients who have failed previous therapies.