Drugmaker Bristol-Myers Squibb says it is suspending a mid-stage study of a potential hepatitis C treatment due to a serious patient safety issue.
The New York company did not elaborate on the problem in a brief statement. It says the cause of the issue and potential relationship to the drug are unknown.
Bristol-Myers shares are down more than 5 percent in premarket trading Thursday.
The drug company is making a push to become a player in the hepatitis C drug market, and it acquired the potential treatment as part of a $2.5 billion acquisition of drug developer Inhibitex that closed earlier this year.
Hepatitis C is a virus that can lead to life-threatening liver damage and is the main cause of liver transplants in the United States. Analysts say the market for treatments is potentially lucrative for drugmakers.