Centene promoted executive Sarah London to CEO, effective immediately, the insurer announced Tuesday.

London most recently served as president of the company’s non-insurance healthcare enterprises division and executive vice president of advanced technology business line. In these roles, she was in charge of charting the company’s technology services and digital strategy, while also overseeing corporate strategy, quality operations, internal audit, compliance and risk management.

London succeeds longtime CEO Michael Neidorff, who led Centene for more than a quarter century before announcing a plan to retire at the end of 2022. Neidorff is on a medical leave of absence. James Dallas has been named acting chairman in Neidorff’s stead, while London helped lead the insurer’s day-to-day management.

“I am delighted that the Board has appointed Sarah as CEO. Her strategic thinking, fresh perspective and diverse experience make her the natural leader to harness the potential of Centene,” Dallas said in a news release. “Sarah has infused an innovative mindset across the enterprise in her relentless effort to improve Centene’s capabilities to provide the highest quality of care for our members.”

Before joining Centene in 2020, London served as a partner at UnitedHealth Group’s Optum Ventures investment arm and chief product officer for the Optum Analytics data services division. Her appointment comes as more insurers invest in care delivery and healthcare services as a way to grow their revenue beyond insurance premiums, after the Affordable Care Act reduced how much revenue payers can pocket through medical loss ratio requirements.

Activist hedge fund Politan Capital Management grabbed a $900 million stake in the insurer at the end of last year, with the aim of selling off the company’s non-core assets and overhauling Centene’s leadership to drive growth for shareholders. Since Politan invested in Centene, five independent board members approved by the hedge fund have joined the company and six longtime board members have retired or announced plans to step down.

Rumors also have swirled that the company could be entertaining acquisition offers from rivals Humana or Cigna.

Centene is one of the largest Medicaid carriers in the nation, with lower-income adults and children making up more than half of its 26.6 million enrollees. The company also is a major player in the Medicare Advantage and ACA exchanges business. The company has largely grown through acquisition, with recent deals including its $2.2 billion purchase of behavioral health platform Magellan Health and $17.3 billion buyout of insurer Wellcare.

At the end of 2021, the insurer generated $125.9 billion in revenue on net earnings of $1.3 billion. As the company has grown, so has its legal liability.

Over the past month, the company has been hit with four proposed class actions on behalf of its workers. The insurer has also reserved $1.25 billion to settle claims its former pharmacy benefit manager, Envolve, defrauded state Medicaid departments.

“The healthcare landscape is rapidly changing, and Centene’s mission–to transform the health of our communities one member at a time–has never been more relevant,” London said in the news release.