GroupM, the giant media agency unit of WPP, has named Brian Lesser as CEO of North America, succeeding Kelly Clark, the company announced on Thursday.   Lesser presently serves as CEO of Xaxis, the data and and digital media buying unit of WPP.

Succeeding Lesser at Xaxis as CEO will be Brian Gleason , CEO of Xaxis Americas.

Rob Norman, the global Chief Digital Officer of GroupM Worldwide, will have the added post of Chairman of GroupM North America.

Clark announced he would stepping down earlier this week.

More on the announcement can be found in this report on Advertising Age.

Earlier this year, we sat down with Lesser for our series, the Media Revolutionaries. In this segment about his career journey, he is interviewed by Dave Moore, his long time colleague at 24/7 then Xaxis where Moore serves as Chairman. This video is part of series sponsored by Xaxis.