Biogen Inc. has agreed to pay as much as $550 million to develop and sell a drug to treat a genetic seizure disorder, the latest effort by the biotech company to fill holes in its pipeline.

Biogen and Stoke Therapeutics have signed a deal to co-develop and sell Stoke’s experimental drug for Dravet syndrome, outside the U.S.

In exchange for $165 million, Biogen now has access to zorevunersen, a potential first-of-its-kind treatment for Dravet syndrome.

From my colleague Adam Feuerstein: Biogen and Stoke Therapeutics have signed a partnership agreement to co-develop and sell Stoke’s experimental treatment for Dravet syndrome, a severe form of epilepsy, outside the U.S., the companies said this morning.

Biogen (NASDAQ:BIIB) and Stoke Therapeutics (NASDAQ:STOK) said on Tuesday they are collaborating to develop and commercialize zorevunersen, an investigational treatment for Dravet syndrome, in territories outside the United States,