DEERFIELD, Ill. — Activist investor Barry Rosenstein, managing partner of hedge fund JANA Partners LLC, has stepped down from the Walgreens Boots Alliance Inc. (WBA) board after reducing his investment in the company.

WBA said Rosenstein, who had been a director since September 2014, was slated to end his service on the board once JANA’s stake in Walgreens fell below a certain threshold, based on the Nomination and Support Agreement that the companies signed at the time.

“I could not have dreamed up a better example of the value of constructive and positive engagement between a company and its shareholders, and I am proud of the work this board has done since 2014 to put Walgreens on the path to delivering maximum value for all of its shareholders,” Rosenstein said in a statement.

Under the Nomination and Support Agreement, Rosenstein would resign from the Walgreens board if JANA and its affiliates’ holdings of Walgreens common stock fell below 6.25 million shares. According to a Securities and Exchange Commission filing on May 18, Rosenstein disposed of 6 million shares of WBA common stock, leaving JANA with about 4.579 million shares of the company.

“We thank Barry for the new perspectives and experience he brought to the board during his tenure,” WBA chairman James Skinner stated. “He played a valuable role at an important time for the company as Walgreens and Alliance Boots combined in 2014 to transform into a global company.”

Rosenstein had joined the board shortly after Walgreens and Alliance Boots unveiled their plan to form the Walgreens Boots Alliance holding company. At the time, JANA held approximately 12.5 million shares, or 1.3%, of Walgreens common stock and agreed to cap its interest in Walgreens at 4.9% while Rosenstein served on its board.

“His talent and expertise have made a significant contribution to the success of our company and its future,” commented Stefano Pessina, executive vice chairman and chief executive officer of WBA.