The 6 Law Firms Behind the Pfizer Allergan Merger

Pfizer and Allergan announced on Monday that the two drug companies have agreed to combine to create a $160 billion behemoth , effective in 2016, with products from Viagra to Botox.

The deal is structured so the smaller company — Dublin-based Allergan — is technically the buyer, therefore easing the tax burden on the combined entity with its headquarters stationed in a low-cost tax base abroad. Its operational headquarters will be in New York City.

President Obama has called such mergers “unpatriotic” because they have deprived the United States from billions in tax revenue .

Not surprisingly, Skadden, Arps, Slate Meagher & Flom, the law firm known for pioneering the so-called tax inversion mergers, advised on the Pfizer, Allergan transaction, along with a handful of other law firms.

Per the companies’ announcement, the law firms are listed below, along with data about where each ranks in Bloomberg’s year-to-date league tables in pending and completed deals. [Note: the data is updated regularly as companies submit deal information to Bloomberg, so the figures are constantly changing]

One law firm, Dublin-based Arthur Cox with about 350 lawyers, had advised on at least two other deals this year: Emirates National Oil Company’s $3.7 billion purchase of Dragon Oil and the sale of Ikaria to specialty biopharmaceutical company Mallincrodt for $2.3 billion.

Its involvement in the Pfizer, Allergan merger lifts the law firm’s standing in Bloomberg’s M&A league tables to being among the top 20 advisors worldwide in terms of deal value, advising on a total of three deals in 2015 with an average deal value of $66 billion.

By doing so, it currently ranks higher than much larger law firms such as Jones Day, which ranks No. 22, Sidley Austin, which ranks No. 29 and Morrison & Foerster at rank No. 30.

Arthur Cox managing partner Brian O’Gorman did not respond to a request for comment.

Pfizer:

• Wachtell, Lipton, Rosen & Katz

Rank: 2, Market Share: 13.4 percent, Total Deal Value: $685 billion, Average Deal Value: $3.2 billion, Deal Count: 274

• Skadden, Arps, Slate, Meagher & Flom

Rank: 1, Market Share: 17.6 percent, Total Deal Value: $901 billion, Average Deal Value: $5.4 billion, Deal Count: 126

• A&L Goodbody

Rank: 21, Market Share: 3.8 percent, Total Deal Value: $194 billion, Average Deal: $7 billion, Deal Count: 26

Allergan:

• Cleary Gottlieb Steen & Hamilton

Rank: 6, Market Share: 10 percent, Total Deal Value: $512 billion, Average Deal Value: $7.2 billion, Deal Count: 71

• Latham & Watkins

Rank: 4, Market Share: 12.3 percent, Total Deal Value: $632 billion, Average Deal Value: $2.2 billion, Deal Count: 284

• Arthur Cox

Rank: 20, Market Share, 3.9 percent, Total Deal Value: $198 billion, Average Deal Value: $66 billion, Deal Count: 3

(UPDATED: This post has been updated to correct the number of lawyers at Arthur Cox and clarify that the firm has advised on more than two deals this year)