The Food and Drug Administration issued a second approvable letter seeking more data from Pozen Inc. and GlaxoSmithKline on their migraine medication, Trexima, further delaying the drug's approval.
Shares of Pozen plunged $7.67, or 44 percent, to $9.78 in morning trading.
The companies said Thursday the FDA asked Pozen to address potential implications from a preclinical study into chromosomal risks _ one of four standard genotoxicity studies _ in which genotoxicity was seen for the combination of naproxen sodium and sumatriptan, but not with either component alone.
Trexima combines Glaxo's migraine drug Imitrex, known generically as sumatriptan, with naproxen sodium, an older anti-inflammatory drug.
None of the other three standard genotoxicity studies demonstrated any genotoxicity for the combination of naproxen sodium and sumatriptan, according to the companies.
An approvable letter is an official notification from the FDA that contains conditions that must be satisfied prior to obtaining final U.S. marketing approval.
The companies said they plan to request a meeting with the FDA as quickly as possible to discuss the necessary steps to address the agency's concerns.
In June 2006, the FDA issued an approvable letter on Trexima that asked for additional drug safety information. The FDA did not accept the additional data submitted by the company in November. The companies then filed additional safety data in January.