CHAPEL HILL –POZEN Inc. (NASDAQ: POZN), said expiration of a government anti-trust act waiting period triggers $25 million in initial payments to Pozen by GlaxoSmithKline in connection with their joint development of a new migraine treatment.

The Hart-Scott-Rodino Antitrust Improvements Act required a waiting period before the two companies could continue their pursuit of the new drug.

Now that the waiting period is over, Pozen said that it and GSK will proceed with development and commercialization of its migraine drug.

The product is a combination that may improve the effectiveness of GlaxoSmithKline’s proprietary triptan by adding a non-steroidal anti-inflammatory drug (NSAID).

NSAIDs are pain-killers such as aspirin and ibruprofen.

Pozen refers to the combination migraine drug as MT 400. The company specializes in improving the safety and effectiveness of existing pharmaceutical products.

Pozen stock fell 91 cents to $11.65 in midmorning trading Wednesday.