The Federal Trade Commission on Friday sued to block the $1.9 billion merger of infection-prevention firm Steris Corp. and U.K. peer Synergy Health PLC, with the companies pledging to fight back in court.

Steris agreed to buy Synergy in October in a combination that mirrors larger inversion deals, in which U.S. firms relocate to lower-tax jurisdictions. Originally slated for completion by March 31, the deal has been on hold since January, when the FTC asked the companies for extra information.

The FTC alleged the deal would violate antitrust law by significantly reducing future competition for the sterilization of medical devices and other products using radiation. The FTC said Synergy was planning X-ray-sterilization facilities in the U.S. that would in the future compete with gamma-sterilization services offered by Steris. It is unlikely that other companies would replicate that competition, the FTC said.

The FTC said it is asking a federal court in Ohio to issue a preliminary injunction blocking the deal while it holds an in-house administrative trial on the merger in late October.

A public copy of the FTC's legal complaint wasn't immediately available because confidential information was still being redacted from it.

"We have worked diligently to address the FTC's concerns and to avoid litigation, but we will now focus our efforts on prevailing in court," Walt Rosebrough, president and chief executive of Steris Corp, said in a statement.

The companies said they would extend the deadline for the deal to Dec. 31, buying time to contest the decision. Steris also plans to extend a bridging loan. Synergy has twice postponed a shareholder vote to approve the deal.

Richard Steeves, CEO of Swindon-based Synergy Health, said the FTC has been paying close attention to a Synergy unit that provides outsourced sterilization services to manufacturers.

"They've asked for a lot of information on Applied Sterilization Technologies," he said. "That's where they've been focusing their attention."

He described the division as a "tiny" part of Synergy Health's business, with a market share of between 1.8% and 4% in the U.S., depending on how the FTC decides to categorize its sales.

The unit may be a sticking-point for the FTC because it is "probably" the third-largest company in its corner of the health-care market, while Steris itself is one of the top two, said Julie Simmonds, an analyst at Canaccord Genuity Ltd.

Write to Ed Ballard at ed.ballard@wsj.com and Brent Kendall at brent.kendall@wsj.com

Access Investor Kit for Synergy Health Plc

Visit http://www.companyspotlight.com/partner?cp_code=P479&isin=GB0030757263

Access Investor Kit for STERIS Corp.

Visit http://www.companyspotlight.com/partner?cp_code=P479&isin=US8591521005

Subscribe to WSJ: http://online.wsj.com?mod=djnwires

Synergy Health (LSE:SYR)
Historical Stock Chart
From Mar 2024 to Apr 2024 Click Here for more Synergy Health Charts.
Synergy Health (LSE:SYR)
Historical Stock Chart
From Apr 2023 to Apr 2024 Click Here for more Synergy Health Charts.