Drugmaker Pozen Inc. (POZN) on Monday said it will respond fully to U.S. regulators in the fourth quarter to address concerns raised about the safety of an experimental migraine drug it is developing with GlaxoSmithKline Plc (GSK), sending shares up 22 percent.

Analysts read Pozen's response to the U.S. Food and Drug Administration's so-called approvable letter announced on June 9 as a sign that the safety concerns could be easily addressed. Pozen's shares jumped $1.33 to $7.40 on the Nasdaq, where it was among the top percentage gainers.

The agency last month said it would not approve the drug Trexima until new safety information was available, sending shares down some 50 percent.

Pozen made the announcement after it and partner Glaxo met with the FDA.

"The fairly quick turnaround on the submission suggests no new clinical studies are necessary, and Pozen likely has the requisite safety data already in it possession," said Wachovia analyst Michael Tong, in a note to clients.

Trexima combines Imitrex with the painkiller naproxen, an older non-steroidal, anti-inflammatory drug or NSAID.

Imitrex is part of a class of drugs known as triptans used to stop but not prevent migraines. The drugs aim to relieve pain by allowing better blood flow. Adding naproxen helps extend the relief, Pozen has said.

Tong said he expects the product could be launched as early as the second half of 2007.