Pozen (Nasdaq: POZN) is cashing in big time on its drug development partnership with GlaxoSmithKline.

The Food and Drug Administration’s approval of the migraine drug Treximet triggered a $20 million milestone payment to Pozen by GSK, its development partner. GSK has already paid Pozen more than $30 million in development and milestone payments.

The FDA approved Treximet on April 15. According to Pozen, the drug will be available by mid-May.

Treximet includes Imitrex in combination with an anti-inflammatory pain reliever. Pozen’s proprietary technology is used to combine the drugs.

Treximet is expected to be good news for the more than 29 million Americans who suffered from migraines. The FDA approved the drug after a review of data that showed Treximet had “a significantly greater percentage of patients migraine relief at two hours” compared with being treated by the drugs in Treximet separately.