Cooley Adds Sean W. Brownridge as Chair of Activism Defense Practice

New York – September 16, 2025 – Today, Cooley announced that Sean W. Brownridge has joined as a partner in the firm’s M&A group and new chair of its activism defense practice. Based in the firm’s New York office, Brownridge brings extensive experience counseling boards, management teams and investors on activist engagements, having guided some of the most high-profile proxy contests and campaigns in recent history. He is a widely regarded thought leader on activism and is recognized as a “Next Generation Partner” for Shareholder Activism by The Legal 500.    

“Sean is a force in his field, and we are honored to have him join our market-leading team,” said Cooley CEO and partner Rachel Proffitt. “Sean’s experience will be invaluable as we redefine what it means to be a destination defense practice servicing the complex needs of public companies across an elite, multidisciplinary platform. With teammates like Sean, we continue our commitment to scale with the fastest-growing and most scrutinized companies in the world.”

Brownridge joins from McDermott Will & Schulte, where he advised several of the leading engaged investors on all aspects of shareholder activism, including the assessment of investment opportunities, alternative activism strategies, settlements, proxy contests and contested M&A transactions. Previously, he was a member of the shareholder activism & hostile takeover defense group at Kirkland & Ellis and clerked for Judge Karen L. Valihura of the Delaware Supreme Court. 

“Sean’s arrival will be a key differentiator to our clients, particularly as our technology and life sciences companies increasingly sit in the crosshairs as potential activist targets,” said Jamie Leigh, Cooley partner and chair of the firm’s global M&A practice group. “Sean’s historical experience advising leading activists as well as management groups and boards adds another elite layer to our activism defense team.”

“I’m grateful to be joining Cooley, which I’ve long admired for its position within the corporate landscape and depth of public company expertise,” said Brownridge.  “Addressing shareholder activism effectively is a fundamental and ever-evolving function of boards and management teams, and I look forward to partnering with Cooley’s many talented lawyers to build a standout defense practice that enables our clients to productively navigate their most critical shareholder engagements.”

Ranked among the leading shareholder activism practices by The Legal 500, Cooley has successfully advised on hundreds of activist defense campaigns. Since 2020, Cooley has advised on 1,600+ M&A transactions, with an aggregate value of more than $735 billion, making its M&A practice one of the most active in the world. Bloomberg ranked Cooley as #1 for global and US M&A for both tech and life sciences transactions by deal count for H1 2025.

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