Kirkland & Ellis advised AbbVie Inc. in its $63 billion cash and stock purchase of Botox-maker Allergan Inc., which was represented by Wachtell in one of the largest mergers in the pharmaceutical industry this year.

The merger will allow AbbVie, maker of top-selling rheumatoid arthritis injection Humira, to diversify its market portfolio. The deal would create a combined company with about $48 billion in sales, making it one of the biggest companies in the healthcare industry.

The deal is expected to close in early 2020.

Kirkland has represented Chicago-based AbbVie in a variety of matters over the years. Most recently Kirkland scored a victory as counsel for AbbVie in the third bellwether trial over its testosterone gel Androgel, vacating the jury verdicts in the first two trials.

Kirkland’s team advising AbbVie was led by corporate partners Eric Schiele, Jonathan Davis and Carlo Zenker along with one associate. Other lawyers leading on the deal were capital markets partners Sophia Hudson and Maggie Flores, debt finance partners Melissa Hutson and Yuli Wang, executive compensation partners Scott Price, Michael Krasnovsky, and Kate Coverdale, antitrust partners Matt Riley and Paula Reidel, tax partners Dean Shulman, Sara Zablotney, and Adam Kool and litigation partner Jim Hurst.

Irish law firm McCann FitzGerald also represented AbbVie in the transaction.

Wachtell, which recently represented United Technologies Corp. in its all-stock purchase of U.S. defense contractor Raytheon Co., has also had a history of working with Allergan. In 2015, the firm advised Allergan on its $66 billion sale to Irish drug maker Actavis.

Wachtell’s team was led by corporate partners Andrew Brownstein, Igor Kirman and Elina Tetelbaum.

Executive compensation and benefits partner Andrea Wahlquist, litigation partner John Savarese, restructuring and finance partner Michael Benn, and tax partners Jodi Schwartz and Tijana Dvornic also advised on the deal. Eight associates from various practice groups at Wachtell participated as well.

Dublin-based law firm Arthur Cox also advised Allergan.