NEW YORK — The co-founders of the consumer powerhouse Catalyst abruptly stepped down this week, three years after the agency sold to IMG (now part of WME/IMG following the merger with William Morris).

Managing partners Bret Werner and Bill Holtz parted ways with the firm, several months before their contract expires at the end of the year. The Catalyst business will remain under the oversight of Ed Horne, EVP of strategy and activation at WME/IMG. Catalyst SVPs Joe Flores, Rob Bronfeld and Ted Fragulis will also remain, reporting into Horne.

Catalyst is a division of WME/IMG’s Global Partnerships Group, which includes global marketing, sponsorship sales, brand strategy and activation, public relations and communications, research and insights focused on brands. As part of this group, the firm partners with sister agencies such as droga5, Red Interactive and Grab Analytics.

“We thank Bret and Bill for their hard work and leadership these past three years, and we wish them all the best in the future," Horne said in a statement. 

Separately, Werner told the Holmes Report, "It has been an incredibly rewarding, 10-year experience building Catalyst into an award-winning agency and successfully integrating the firm into IMG over the last three years. These accomplishments are simply not possible without a world-class staff and an amazing group of client partners. As I reach the conclusion of my contract, I wish my friends and colleagues the best in the future and look forward to my next professional challenge."

This year, the Holmes Report named Catalyst Consumer Agency of the Year , recognizing the firm's growth beyond traditional sports marketing to entertainment and lifestyle marketing, and its overall range of capabilities.

The firm has doubled in size since 2011 and was up by 10% last year, picking up new assignments from clients such as Facebook, Marriott, Purity Vodka, Tata and Warner Bros, joining a roster that includes Dockers, Subway, Timex and Under Armour.

The firm's high-profile work included enlisting A-list celebrities to help introduce the new Xbox One; launching the Sports Matter cause-related marketing initiative for Dick’s Sporting Goods; and managing the crisis that ensued after Under Armour’s speedskating suits came under fire at the Olympics.