By Helen Coster and Sheila Dang
(Reuters) - Brian Lesser, chief executive of AT&T (NYSE:T) Inc's advertising unit Xandr, has resigned, a source familiar with the matter said on Wednesday, raising questions about the future of its advanced advertising strategy.
A spokesman for AT&T declined to comment. Lesser was not immediately reachable.
Lesser had interviewed for the CEO role at WarnerMedia, AT&T's media unit, but received an indication that he would not be selected, the source said.
A replacement at Xandr is not yet known.
AT&T has spent a combined $134 billion to buy satellite TV provider DirecTV and media company Time Warner to take on Netflix Inc (NASDAQ:NFLX) and then craft a digital and TV advertising strategy that would make use of the combined companies' assets.
The company launched Xandr in 2018 to offer partners a better way to target ads to consumers using data collected from phone, internet and TV services.
Lesser felt comfortable stepping down because Xandr is in a good position and its first quarter results are expected to show significant growth, the source said.
A long-time advertising executive, Lesser joined AT&T in 2017 and was previously CEO of ad agency GroupM North America. Lesser also founded Xaxis, an ad technology company.
At Xandr, he oversaw the purchase of ad tech companies AppNexus and clypd to give Xandr the technical capabilities of selling digital and TV ads.
However, ad agency executives who spoke with Reuters earlier this year have viewed Xandr's progress as slow, citing few new product offerings for advertisers since its launch.
A spokeswoman for Xandr did not immediately respond to a request for comment.
News of Lesser's resignation came on the same day the company announced a move toward its long-stated goal of changing how TV ads are purchased.
On Wednesday, Xandr launched a TV ad-buying tool in partnership with Walt Disney (NYSE:DIS) Co, AMC Networks and WarnerMedia that would allow advertisers to target certain viewers across the networks using AT&T data.
One ad agency executive who did not want to be named said the timing of Lesser's resignation was a surprise. The executive added that clients would be advised against using Xandr's new ad buying tool until there was more clarity surrounding the company's technology strategy.