Slaughter and May and Kirkland & Ellis are advising on the sale of London-listed software security company Sophos to U.S. private equity firm Thoma Bravo for $3.9 billion.

Thoma Bravo invests in the software and technology enabled-services sector, with more than $35 billion in investor commitments, according to the company.

Magic Circle firm Slaughters is acting for Sophos on the sale. Its team includes senior partner and corporate heavyweight Steve Cooke and fellow corporate partner Rob Innes, as well as competition partner Will Turtle and employment partner Phil Linnard.

U.S. powerhouse Kirkland & Ellis is advising Thoma Bravo, according to a statement by the company.

Sophos floated on the London Stock Exchange in 2015. At the time, it was the largest ever initial public offering in the U.K. tech sector.

Freshfields Bruckhaus Deringer, Gibson Dunn & Crutcher and White & Case won roles on the move.

Earlier this year, Sophos general counsel Eleanor Lacey left the company to join teamwork management application company Asana.