Recently, AT&T, the American Multinational conglomerate holding company bought Appnexus for around $2B.

http://about.att.com/content/dam/snrprivate/2018/February 2018/globe_logo_1x1.jpg

Appnexus is an advertising marketplace, which has been recently struggling due to competitions from Facebook and other such platforms.

https://s.ppc.land/wp-content/uploads/2018/03/AppNexus-logo.png

AppNexus has raised $344M from investors like News Corp., WPP, Fidelity, TCV, Microsoft, Deutsche Telekom, Khosla, etc.