(Reuters) -UnitedHealth said on Thursday it will replace its finance chief John Rex with an external hire, Wayne DeVeydt, adding to the management changes at the health insurer that has been struggling to control its medical costs.

Rex, who has been handling the role since 2016, will continue as a strategic advisor to the CEO, with the changes effective September 2.

DeVeydt was most recently managing director and operating partner at Bain Capital, and was also the finance chief of UnitedHealth's rival Elevance , then called Anthem, between 2007 and 2016.

The largest U.S. health insurer had seen an abrupt departure of Andrew Witty as CEO in May, with Stephen Hemsley replacing him following struggles with elevated medical costs that were also seen in the rest of the industry.

Hemsley is under pressure to regain investor trust as the company faces financial struggles and reputational damage that surfaced after the then-CEO of its health insurance unit was gunned down on a New York City street in December.