Brian Lesser, a GroupM executive that has held a number of leadership roles within the WPP-owned media giant, is leaving to join AT&T.
Lesser, CEO of GroupM North America and former global CEO of programmatic powerhouse Xaxis, will become CEO of a new advertising and analytics business within the telecom titan.
AT&T hopes to build an automated advertising platform for TV and premium video that would be able to better target and reach consumers.
Lesser is "one of the best there is" in using data and tech for targeted advertising, said AT&T Chairman-CEO Randall Stephenson in a statement. He added that the company plans to start building the platform after completing the acquisition with Time Warner, which is still under review by the U.S. Department of Justice and other authorities.
Lesser was named CEO of GroupM North America in 2015. It was a new direction for the world's largest media buying company, which had hired leaders from the traditional media buying world. Lesser previously ran Xaxis, GroupM's data and digital buying arm, and before that was VP-product management and director of product marketing at 24/7 Real Media, which was acquired by WPP in 2007.
"This was a difficult decision for him and while I'm really disappointed that he's leaving, I wish him every success in his new role," GroupM Global CEO Kelly Clark wrote in a memo to staff.
Clark will take on Lesser's responsibilities as GroupM searches for his replacement.
In recent months, GroupM has announced a slew of leadership and structural changes, including the news in June that it would be combining MEC and Maxus to form a new company and increase its investment in Essence, the historically digital agency it acquired in 2015.
Lesser was included in Ad Age's 40 under 40 list in 2014.