AmerisourceBergen announced on Wednesday that chief legal officer John Chou will step down after almost 20 years with the company, and just weeks after the firm completed its $6.5 billion acquisition of Alliance Healthcare from Walgreens Boots Alliance.

Chou will be replaced by Elizabeth Campbell, who has served as deputy general counsel to the Conshohocken, Pennsylvania-based health care company for the past year. In her new role, Campbell will oversee the regulatory and legal teams at AmerisourceBergen. She will report directly to chairman and CEO Steven Collis.