ViroPharma says FDA wants new Cinryze study

The Food and Drug Administration wants ViroPharma Inc. to run another clinical trial of its drug Cinryze before it will consider a new approval for the drug, ViroPharma said Thursday.

Cinryze treats hereditary angioedema, a genetic disease that can cause dangerous swelling in the throat and extremities. The drug was approved in October as a routine preventive treatment for angioedema attacks, and ViroPharma is trying to gain additional marketing approval for the drug as a treatment for acute attacks.

The FDA wants a new clinical trial because the placebo-controlled study included in ViroPharma's application was not strong enough, ViroPharma said. The company did not say how long a new study might take.

It said the FDA did not mention any safety concerns in its complete response letter.

In premarket trading, shares of ViroPharma fell 73 cents, or 10.5 percent, to $6.20 after closing Wednesday at $6.93.