VALLEY FORGE, Pa. — AmerisourceBergen Corp. announced last month that Steve Collis, the company’s chief executive officer, will succeed company chairman Richard Gozon next year.

The company has also adopted measures to make it easier for certain shareholders to nominate directors to the board.

Collis will take on the chairman role following Gozon’s retirement at the annual stockholder meeting, which is to be held in March, the company noted. Collis has served as CEO of AmerisourceBergen since July 2011 and as a company director since May 2011.

The company also announced that Jane Henney will become the board’s lead independent director. Henney has served as a company director since January 2002.

AmerisourceBergen said it has changed its bylaws to allow for so-called proxy access, joining a growing list of big companies that are making similar moves.

The new rules stipulate that a shareholder or a group of shareholders who have owned at least 3% of shares outstanding for three years is allowed to nominate directors to the board — two directors, or 20% of the board, whichever is greater.