Idenix Pharmaceuticals Inc said the U.S. health regulator had informed the company that it would need more time to conduct a safety review of Idenix's hepatitis C drug.
The company said on its website that the FDA had conveyed the need for additional time earlier this month. (r.reuters.com/jah25t)
Idenix said it submitted data to the U.S. Food and Drug Administration in December.
The FDA had placed the drug, IDX184, on a partial clinical hold last August, citing adverse cardiac events seen in rival Bristol-Myers Squibb Co's hepatitis C drug.
Idenix cannot enroll patients in further studies until it gets FDA clearance for the trial design. The company now expects a response in the first quarter of 2013.
Shares of the Cambridge, Massachusetts-based company were down 7 percent at $4.67 on Wednesday morning on the Nasdaq.
(Reporting by Pallavi Ail in Bangalore; Editing by Roshni Menon)