(Reuters) -CVS Health on Friday named company veteran David Joyner as new CEO, succeeding Karen Lynch who stepped down from the helm of the struggling healthcare giant after an agreement with the board.

Shares of the company tumbled 11% to $57 in premarket trading.

Joyner, who is the president of the company's pharmacy benefit manager CVS Caremark, takes over as president and CEO from Friday, the company said.

The change comes on the back of repeated profit forecast cuts this year as the company's insurance segment has struggled with rising medical costs.

"The board believes this is the right time to make a change, and we are confident that David is the right person to lead our company," said Chairman Roger Farah.

The healthcare giant is also exiting its core infusion services business and plans to either close or sell 29 related regional pharmacies in the coming months, Reuters reported earlier this week.

The Wall Street Journal had first reported the news of Joyner's appointment on Friday.