DLA Piper has lost two more US rainmakers, including the co-chair of the firm's US private equity practice Steven Napolitano, following the recent exits of more than 20 partners to McDermott Will & Emery.

Napolitano and fellow private equity partner Brendan Head, the co-managing partner of DLA's Chicago office, are set to join Kirkland & Ellis as partners in the firm's much-vaunted private equity practice, according to two sources familiar with the moves.

Both sources said the pair had a large book of business, mostly representing private equity clients, worth up to $30m.

"We wish Steve and Brendan all the best and look forward to collaborating with them in the future," said a statement from a DLA Piper spokesman. A Kirkland spokeswoman did not immediately return a request for comment on the matter, nor did Napolitano and Head.

The departure of both lawyers follows closely on the heels of the recent major exodus from DLA to McDermott. In March, the US firm began a raid on DLA that would grow to nearly 50 lawyers with the hire of heavyweight Chicago litigator Michael Poulos.

Poulous, a former co-managing partner of the Americas at DLA, ran a litigation practice that several sources said was worth around $30m in business.

McDermott also brought aboard Michael Sheehan, the former co-chair of DLA's global employment practice and chair of its US employment practice. The firm subsequently added a real estate finance team headlined by Jeffrey Steiner, the former New York-based global co-chair of DLA Piper's finance practice, as well as a trio of London real estate partners – Laurence Rogers, Neville Wright and Tom Calnan.

In a letter to its partners, McDermott chairman Ira Coleman said that the firm expected the hires to add $100m to its annual revenues. (McDermott's gross revenue was $925.5m in 2017.)

For Kirkland, which broke the $3bn gross revenue mark in 2017, the move is yet another splashy addition its leading private equity practice, on the back of its February hire of Jennifer Perkins, the former co-chair of Latham & Watkins' global private equity practice.

Kirkland's appetite for lateral acquisitions has been fuelled by an almost unprecedented run of financial growth within the past decade. In April, the firm hired two lawyers from Cravath Swaine & Moore, including former litigation head Sandra Goldstein, only four months after it brought on ex-Cravath M&A partner Eric Schiele.

The move to Kirkland marks the second time that Napolitano and Head have made partnership transitions together, after the pair left Winston & Strawn to join DLA Piper's Chicago office in 2007.