The regulator said the buyout “would lead to a highly concentrated market for outsourced hydrophilic coatings and eliminate significant head-to-head competition.”

The U.S. Federal Trade Commission (FTC) has sued to block the planned acquisition of medical device company Surmodics (Nasdaq:SRDX) by GTCR.

The FTC said merging Surmodics with Biocoat, where GTCR has a majority stake, would result in one company with over 50% of the hydrophilic coating market.

The agency is challenging the deal, citing antitrust concerns due to GTCR's existing ownership of Surmodics' rival Biocoat.

Surmodics (NASDAQ:SRDX) fell 4.6% after the Federal Trade Commission filed a lawsuit to block its planned $627 million sale to private equity firm GTCR. The FTC filed suit in the U.S. District Court for the Northern District of Illinois,