US firms Wachtell Lipton Rosen & Katz, Skadden Arps Slate Meagher & Flom, Cleary Gottlieb Steen & Hamilton and Latham & Watkins have lined up alongside leading Irish firms to advise on the $160bn pharmaceutical mega-merger between Pfizer and Allergan.

The high profile mandate – which will create the world's biggest drug company by sales – sees Wachtell advising Pfizer on the deal alongside Skadden and Ireland's A&L Goodbody.

Wachtell's team is being led by New York corporate partners Edward Herlihy and David Lam and also includes antitrust partner David Schwartz, executive compensation and benefits partner Jeannemarie O'Brien, finance partner Gregory Pessin and tax partner Jodi Schwartz.

Skadden is advising Pfizer on tax matters with A&L Goodbody advising on Irish law matters.

Skadden's team includes New York partners Paul Schnell, Sean Doyle and Michael Chitwood advising on M&A, Sally Thurston, Steven Matays and Brian Krause advising on tax; Resa Schlossberg and Jose Esteves advising on intellectual property (IP) and technology and litigation partner Douglas Nemec.They are working alongside lawyers from offices including Washington and Brussels, where competition partner Ingrid Vandenborre is advising.

Skadden also advised Pfizer on its £60bn bid for UK rival AstraZeneca in 2014, which was later rejected. The firm fielded a London-based team comprising corporate partners Michael Hatchard and Scott Hopkins and tax partner Tim Sanders.

Morgan Lewis is providing antitrust advice to Pfizer on the deal with a team led by partners Scott Stempel and Harry Robins.

Clifford Chance is advising Pfizer on all antitrust aspects outside the US and Canada. The firm's team is bead led by antitrust partners Marc Besen and Joachim Schütze.

Debevoise & Plimpton is advising Guggenheim Securities and Goldman Sachs, the financial advisers to Pfizer.

The Debevoise team is being led by corporate partner Andrew Bab and includes fellow corporate partner Jeffrey Rosen.

Irish heavyweight Arthur Cox is advising Dublin-headquartered Allergan alongside US leaders Cleary Gottlieb and Latham.

Arthur Cox's team is being led by corporate partner Geoff Moore. He is being assisted by fellow corporate partners Chris McLaughlin and Stephen Ranalow. Tax partner Ailish Finnerty and finance partner Ultan Shannon are also advising on the deal, which was confirmed earlier today.

The multidisciplinary Cleary Gottlieb team advising Allergan is led by corporate partners Paul Shim and Jim Langston. Partner Michael Albano is providing employment advice and partner Romano Subiotto QC is providing non-US antitrust advice.

Partners Jeff Karpf and Meme Peponis are providing capital markets, securities and financing advice, while partner Daniel Ilan and is providing intellectual property advice.

All the partners on the firm's team are based in New York, apart from Subiotto who is based in Brussels and London, Maydell who is based in Brussels, and Sterling who is based in Washington.

In July Latham advised Allergan on the sale of its generics business to Teva Pharmaceutical for $40.5bn (£26bn). The firm's team on the deal was led by New York partner Charles Ruck and Orange County partner Scott Shean.

The US firm also won a role on Allergan's acquisition of Kythera Biopharmaceuticals for $2.1bn (£1.3bn) in June this year, however on that occasion it advised Kythera. Covington & Burling advised Allergan on the deal.

The Pfizer/Allergan deal will see the two businesses combining under Allergan, which will be renamed Pfizer. The combined company will be listed on the New York Stock Exchange but will be domiciled in Ireland.