Sarah Barnett is leaving her post as entertainment president of AMC Networks

In a surprise move, Sarah Barnett is stepping down as president of AMC Networks Group after just 18 months on the job.

The entertainment company known for such TV hits as “The Walking Dead,” “Better Call Saul” and “Killing Eve” announced Thursday that Barnett, who has been with the company for 11 years, will exit her role shortly after Labor Day.

No replacement was named, as her duties will be handled by longtime AMC Networks Chief Operating Officer Ed Carroll on an interim basis.

The move comes as AMC Networks — which owns cable channels AMC, BBC America, Sundance and IFC — deals with the challenges facing traditional television companies that have watched streaming services siphon off viewers in recent years. The publicly traded company based in New York City is controlled by the Dolan family.

In a statement, Barnett said the decision to leave was hers.

“This is a year that has confronted us with radical change on multiple fronts,” Barnett said. “After a lot of consideration — and with a slightly breaking heart — I have decided that it is the right time for me to follow my curiosity and leave things in the very capable hands of the outstanding team at AMC Networks. Shaping stories and connecting them to audiences alongside brilliant people inside and outside of this company has been a unique joy and privilege for the past 11 years.”

Barnett’s exit, however, was unexpected. She was elevated to the top creative job at AMC Networks in November 2018 following the departure of Charles Collier, who left to become chief executive of entertainment for Fox, the company spun off from 21st Century Fox after the sale of most of its assets to Walt Disney Co.

Barnett’s departure comes less than a year after AMC Networks lost its programming chief David Madden, who exited last August. Madden is now president of Berlanti Productions, the company founded by producer Greg Berlanti.

Barnett took over the job after she developed the drama hit “Killing Eve” for BBC America, which she ran for four years. She took over a company that has continued to receive creative kudos for its series but is confronting systemic changes in viewing habits that have upended the traditional TV business.

AMC Networks’ flagship channel AMC has seen its audience levels decline as its long-running zombie apocalypse saga “The Walking Dead” is well past its peak as one of the most popular dramas on television.

Launching new series that can approach the popularity of “Walking Dead” is a nearly insurmountable task as viewers have a myriad of choices through streaming services and cord-cutting of pay TV services chips away at the number of homes that cable channels can reach.

AMC Networks has stepped up its program production in recent years and has focused on developing new businesses, such as over the top streaming channels, in order to reach viewers that are forgoing cable subscriptions.