Sullivan & Cromwell and Skadden Arps Slate Meagher & Flom have won roles advising as Canada's Valeant agrees to buy Sprout Pharmaceuticals for $1bn (£640m).

Valeant made an offer after Sprout gained regulatory approval this week (19 August) for its libido-enhancing drug. Flibanserin, marketed as Addyi, has been dubbed the "female Viagra".

Sullivan & Cromwell is advising Sprout on the deal with a New York-based team including corporate partners Matthew Hurd, Stephen Kotran, tax partner Ronald Creamer and executive compensation & benefits partner Matthew Friestedt.

Skadden is advising Valeant.

The deal is subject to regulatory approval but Valeant has said it should go through by the end of September.

Under the terms of the deal, Valeant will pay $500m (£318m) when the deal is finalised and a further $500m during the first three months of next year.

In February, Sullivan and Cadwalader Wickersham & Taft advised on Valeant's $14.5bn (£9.5bn) acquisition of gastrointestinal drug specialist Salix.

The pharmaceutical sector has seen a string of high value deals in recent months.

Most recently, Wachtell Lipton Rosen & Katz, Sullivan & Cromwell and Ropes & Gray were called in for US pharmaceutical company Alexion's $8.4bn (£5.5bn) purchase of fellow US drug-maker Synageva.

In February, Sullivan also acted on a merger deal between medical device companies Sorin Group and Cyberonics.

Meanwhile, in Janurary, Skadden secured a role alongside Slaughter and May and Davis Polk & Wardwell on Shire's $5.2bn (£3.4bn) acquisition of US company NPS Pharma.