Allergan has announced a definitive merger agreement to purchase MAP Pharmaceuticals in a deal worth around $958 million (603.36 million pounds).

MAP Pharmaceuticals is a biopharmaceutical company that specialises in the development and commercialisation of new therapies in the field of neurology, including Levadex, a potentially promising new migraine therapy.

Levadex is currently under review by the US Food and Drug Administration and is seen as a strong product offering that will complement Allergan's Botox, which has been approved in 56 countries for the treatment of chronic migraine in recent years.

The deal will help Allergan strengthen its widely-recognised leadership position in the field of neurosciences.

David Pyott, chairman of the board, president and chief executive officer at Allergan, said the company plans to "use MAP's proprietary drug particle and inhalation technologies to generate new pipeline opportunities".

This comes after Allergan completed a $350 million takeover of the aesthetic skin care specialist SkinMedica last month.