US regulators have finally approved a new combination migraine drug called Treximet, which has been developed by GlaxoSmithKline and partner Pozen.

The US Food and Drug Administration has given the green light to Treximet/Trexima (sumatriptan/naproxen) for the acute treatment of migraine attacks with or without aura in adults. It is the first product designed to target multiple mechanisms of migraine by combining a triptan (sumatriptan is the active ingredient in GSK’s Imitrex) and an anti-inflammatory pain reliever in a single tablet.

The approval is based on clinical trials which show that Treximet provided a significantly greater percentage of migraine pain relief at two hours compared to sumatriptan 85mg or naproxen sodium 500mg alone. In addition, Treximet provided more patients with sustained migraine pain relief from two to 24 hours compared to the individual components.

The FDA approval comes as a pleasant surprise given the tricky regulatory path that GSK and Pozen have endured. Last August they received a second approvable letter for Trexima which followed the first missive sent by the agency in December last year. The firms responded to that letter in January 2007 by submitting additional safety and preclinical data from trials, but that still did not do the trick.

The approvable letters had expressed the FDA’s concern over heart safety, and a preclinical study had suggested possible chromosomal risks. The companies believed that they had answered the agency’s queries but earlier this month another possible problem arose.

The FDA sent a warning letter to GSK following an inspection at its corporate headquarters in North Carolina, which focused on postmarketing reporting requirements relating to Avandia (rosiglitazone) and how they did not comply with FDA regulations. This led to fears that Treximet could face further delays and Pozen’s shares in particular suffered.

However that situation has now reversed and Pozen shares leapt 33% to $14.01 on the FDA approval.