Magic circle duo Slaughter and May and Clifford Chance (CC) are acting opposite US firms Wachtell Lipton Rosen & Katz and Kirkland & Ellis on a £9.8bn transatlantic joint venture between pharma giants GlaxoSmithKline (GSK) and Pfizer.

The agreement will see the two public companies combine their consumer health businesses into a joint venture, with anticipated sales expected to be close to £10bn.

Under the agreement, GSK will retain a 68% controlling interest, while Pfizer will have an equity interest of 32%.

Slaughters' team advising GSK includes corporate partners David Johnson and Simon Nicholls, and tax partner Dominic Robertson. GSK's in-house team on the deal is being led by general counsel James Ford, associate GC Charles Atkinson, GSK Consumer Healthcare GC Sean Roberts and senior vice-president for legal corporate affairs and pharma supply chain Sarah Clements.

Kirkland & Ellis advised GSK on US aspects of the transaction, led by New York-based partner Daniel Wolf, who was supported by partners Eric Schiele, Claire James, Patrick Jacobs and David Fox, as well as tax partners Dean Shulman and Benjamin Schreiner.

Pfizer, meanwhile, turned to Wachtell corporate partners Edward Herlihy and David Lam and soon-to-be partner Jacob Kling, who received support on the UK aspects of the deal from CC corporate partners Gareth Camp and Simon Thomas, and New York-based partner Sarah Jones. Skadden Arps Slate Meagher & Flom also provided tax advice.

The deal is subject to shareholder and authority approvals, and is expected to complete in the second half of 2019.

During the course of three years, GSK plans to demerge and float the joint venture, which will see the company separate its consumer business from its pharmaceuticals and vaccines business.

The company is yet to choose a legal adviser for the subsequent demerger and float, according to an individual close to the deal. 

Slaughters has taken on a number of big-ticket mandates for GSK in recent years, including advising on a $13bn (£9bn) deal that saw the company purchase a 36.5% stake in its consumer health joint venture with pharma giant Novartis. Clifford Chance is also a longstanding adviser to Pfizer.