Mr Brian Byrne > Cleary Gottlieb Steen & Hamilton LLP > San Francisco, United States > Lawyer Profile

Cleary Gottlieb Steen & Hamilton boasts a dynamic cross-border antitrust practice, adept at navigating complex cartel matters. The team’s expertise spans civil and criminal investigations, litigation defense, and enforcement actions, with a comprehensive regulatory offering supported by former FTC and DOJ officials. The practice is jointly steered by Leah Brannon and Heather Nyong’o. Brannon excels in investigations led by the DOJ, FTC, and European Commission, while Nyong’o regularly represents multinational corporations and executives in high-stakes domestic and international cartel investigations and litigation. Elsewhere in the team, Kenneth Reinker stands out for his skill in applying complex economic analysis to antitrust challenges across the healthcare, pharmaceuticals, tech, and finance sectors, while Daniel Culley is noted for his experience in cross-examinations and focus on high-tech industries and two-sided markets. In San Francisco, Brian Byrne shines in cross-border enforcement and antitrust litigation, including M&A reviews. Jeremy Calsyn adds further depth, specializing in global cartel investigations and follow-on class actions. Attorneys are based in Washington DC unless otherwise stated.

The ‘extremely deep bench of expertise’ at Cleary Gottlieb Steen & Hamilton includes experts in complex merger clearance advocacy and multi-jurisdictional criminal and civil investigations, as well as litigation. Its international reach is significant, often working closely with teams in Europe to handle cross-border matters: a particular area of strength for both Brian Byrne  and Daniel Culley. Leah Brannon  and Heather Nyong’o co-head the team; Brannon has notable experience in global merger clearance, while San Francisco-based Nyong’o focuses her practice on antitrust enforcement. George Cary works between DC and San Francisco, a longstanding expert in the field, while David Gelfand has a practice spanning merger review, civil litigation, and criminal investigations, a go-to trial counsel in complex litigated mergers. Bruce Hoffman leverages his experience as a former FTC Bureau of Competition Director to support clients in highly regulated sectors, and Kenneth Reinker is noted for his expertise in the application of complex economics to antitrust matters; Elaine Ewing is also a key name. In January 2025 the New York team was bolstered by the addition of Puja Patel, formerly of A&O Shearman , alongside the promotion to partner of Blair Matthews. Attorneys are based in Washington DC unless otherwise stated.

With numerous victories against the DOJ, FTC, and state attorneys general, Cleary Gottlieb Steen & Hamilton‘s antitrust team boasts a strong track record in merger litigation. Renowned for its work on significant mandates, the team handles everything from complex litigation to high-stakes civil and criminal investigations. Recent highlights include advising prominent clients in the media, food and beverage, TMT, and real estate sectors. Co-chair Leah Brannon, based in Washington DC, oversees high-profile competition litigation in both federal and state courts. Also in DC, George Cary and Jeremy Calsyn bring extensive expertise in complex monopolization, merger disputes, and class action litigation. Operating out of the Bay Area, co-chair Heather Nyong’o is a skilled litigator who frequently represents multinationals and executives, guiding them from investigations to trials and appeals. Splitting his time between the East and West Coasts, Brian Byrne is an adept defender of clients involved in class action and Sherman Act antitrust lawsuits.