Biopharmaceutical giant AbbVie Inc., represented by Kirkland & Ellis, has struck a $63 billion deal to acquire Irish pharmaceutical firm Allergan, with a legal team led by Wachtell, Lipton, Rosen & Katz.

While Kirkland has handled litigation work for AbbVie, this is the first time Kirkland has advised the client in a major transaction. Kirkland's corporate partners on the deal include Eric Schiele, Jonathan Davis and Carlo Zenkner. Kirkland recruited Schiele and Davis from Cravath, Swaine & Moore in 2018 and 2016, respectively, while adding Zenkner, who was a Sullivan & Cromwell associate, in 2017.

Other Kirkland partners on the deal include Sophia Hudson and Maggie Flores in capital markets; Melissa Hutson and Yuli Wang in debt finance; Scott Price, Michael Krasnovsky and Kate Coverdale in executive compensation; Matt Reilly and Paula Riedel in antitrust; Dean Shulman, Sara Zablotney and Adam Kool in tax; and Jim Hurst in litigation, alongside corporate associate Lukas Richards.

Across the table, the Wachtell team for Allergan included Andrew Brownstein, the co-chair of the firm's corporate group, and partners Igor Kirman and Elina Tetelbaum. Corporate Wachtell associates on the deal included Avi Sutton, Carmen Lu, Peter Fritz and Brian Junquera.

Wachtell executive compensation partner Andrea Wahlquist, litigation partners John Savarese and Ralph Levene, restructuring and finance partner Michael Benn and tax partners Jodi Schwartz and Tijana Dvornic also worked on the deal. They were supported by associates Katherine O'Neill, Daniel Wertman and Swift Edgar.

Allergan's legal advisers also included Dublin firm Arthur Cox, while another Irish firm, McCann FitzGerald, advised AbbVie.

Meanwhile, Davis Polk & Wardwell is advising Morgan Stanley & Co. as financial adviser to AbbVie, while Debevoise & Plimpton is guiding Allergan's financial adviser, J.P. Morgan Securities.

A tie-up with Allergan could be just what the doctor ordered for AbbVie, which has made a series of acquisitions over the years to lessen its reliance on the blockbuster rheumatoid arthritis drug Humira. The drug, which according to the Wall Street Journal is already facing competition from so-called biosimilars in Europe and will lose protection in the U.S. in 2023, brought in almost $20 billion for AbbVie last year, the majority of its revenue.

AbbVie has made stabs at a mega-merger before, making a $51.5 billion offer in 2014 to try to acquire Shire, another Irish drugmaker whose overseas domicile could have lowered its tax bill, but the deal ultimately did not go through. AbbVie was represented by Sullivan & Cromwell, Skadden, Arps, Slate, Meagher & Flom and Herbert Smith Freehills in that effort.

The AbbVie-Allergan cash-and-stock deal, which is expected to close in early 2020, values Allergan at about $188 a share, which is a 45% premium over its closing price Monday.