Attorneys from Simpson Thacher & Bartlett LLP helped bring long-running litigation over alleged Libor manipulation to an end, while steering Mattress Firm to a win over a challenge of its $5 billion acquisition by Tempur Sealy, earning the firm a spot among Law360's 2025 Competition Groups of the Year.

Simpson Thacher has 21 partners and 73 other attorneys working on antitrust matters spread across offices in Washington, D.C., New York, California and London, as well as a Brussels office that opened in 2021. The team handles a wide range of merger and conduct work, from the investigation phase through litigation, across numerous industries.

John Terzaken, global co-chair of the firm's antitrust and trade regulation practice, told Law360 the group's work also runs the gamut in terms of cutting-edge issues in the antitrust space, including work on cases involving algorithmic pricing allegations and claims over viewpoint restrictions, or the marketplace of ideas.

"We're involved in the full panoply of issues that exist out there right now," he said.

The group represented Mattress Firm in its successful defeat of a Federal Trade Commission challenge to its acquisition by Tempur Sealy in January. A Texas federal court sided with the companies and found that combining the mattress supplier and retail chain would likely increase competition, if it has any impact at all.

Sara Razi, global co-chair of the firm's antitrust and trade regulation practice, told Law360 the ruling was precedent-setting because the court rejected the FTC's allegations about the specific market that was supposed to be harmed by the deal.

The commission alleged the transaction would reduce competition for "premium" mattresses that cost $2,000 or more. But the court declined to accept a market tied to a specific price range after recognizing there was a lot of variation in what people consider to be premium or luxury mattresses.

"That was an important aspect of the case because previously there had been some decisions by courts that suggested that price bands could be a relevant way to define a product market," Razi said. "But in this particular case, given the evidence, the court disagreed with that allegation."

A Simpson Thacher team represented home health and hospice company Amedisys in a U.S. Department of Justice challenge of its $3.3 billion acquisition by UnitedHealth. The companies reached a settlement with enforcers ending the case in August, conditioned on the sale of at least 164 locations across 19 states.

The firm also represented Paramount Global in its $8 billion merger with Skydance Media that closed in August. That transaction avoided a second request for information in the U.S. and received clearances from antitrust authorities in a number of jurisdictions, including the European Union and the United Kingdom.

Peter Guryan, also a global co-chair of the practice group, said the firm works on a large volume of high-profile mergers across a wide range of industries that are reviewed by the FTC, DOJ and others, many of which close without any intervention.

"We have been very successful, frankly, in avoiding a challenge, or a settlement or resolution, and in many cases, having deals cleared outright," he said.

On the conduct side, Simpson Thacher helped JPMorgan Chase defeat a 14-year-old case accusing more than a dozen large banks of conspiring to manipulate the Libor rate. A New York federal court granted summary judgment to the banks in September, dismissing the remaining claims against all the defendants.

Terzaken said the judge ultimately found there was no antitrust violation because no collusion was demonstrated and because she found the banks could have all been acting on their own.

"It was a lot of time, and a lot of money, and a lot of life spent on an action that, at the end of the day, the basic facts didn't quite meet muster," he said.

The firm also represented McKesson Corp., which helped convince a Pennsylvania federal court in February to toss claims against several pharmaceutical distributors in the sprawling multidistrict litigation over alleged price-fixing in the generic-drug industry.

"Now there's nothing pending against the distributors anymore as a result," Razi said.

Terzaken said the firm won dismissal in several other antitrust cases last year as well, including for Deutsche Bank in a bond-rigging case, Covestro AG in cases over chemicals used to make polyurethane and RPM International in a case over the alleged fixing of concrete and cement additive prices.

"We had a pretty substantial year in terms of the number of motions to dismiss that we won," Terzaken said. "Motions to dismiss — which are not that often granted and tend to be the exception to the rule."