While the St. Louis–based managed care insurer saw revenue grow almost 20% last year, to $194.8 billion, it posted a net loss of $6.7 billion. That was largely driven by a write-down that reflected the new reality for health care companies under the One Big Beautiful Bill Act championed by President Trump. Along with cutting federal Medicaid spending by more than $900 billion over 10 years, the law raises costs and reduces eligibility for people enrolled in Affordable Care Act (ACA) Marketplace plans.

Those changes are shaking up Centene’s core businesses. More than half of Centene’s revenue comes from Medicaid—it’s the country’s biggest Medicaid insurer—with the rest roughly divided between Medicare and Marketplace plans. While analysts don’t expect federal cuts to have a massive impact on Centene’s top line, they’re a sign of the challenges London faces.

Faced with new data that showed its ACA plans were enrolling both fewer and sicker people, London decided to withdraw earnings guidance last July, causing Centene’s share price to fall 40% in a single day, to an eight-year low.

“It’s hard not to feel like pulling guidance and cutting the stock in half is a failure,” London told Fortune in a recent interview. “We’ve watched a new normal unfold in terms of how many different pressures there are on the system and the magnitude of the change we’re facing.”

London is pushing to get ahead of that change. She’s been transforming Centene’s portfolio, technology, and culture since becoming CEO four years ago, at the age of 41, making her the youngest woman to lead a Fortune 500 company (a distinction she still holds).

Under London, Centene is using data and technology to better manage a business that cares for a higher proportion of sicker patients than many other insurers do. She has also launched a One-CenTeam initiative to make Centene a catalyst in creating healthier communities. In May 2024, at the Fortune Brainstorm Health conference, for example, London announced plans to partner in building $900 million of affordable housing in eight states to help boost health outcomes.

Other Centene initiatives spotlight preventive health measures that could help members avoid expensive medical problems—and leave Centene with a healthier bottom line

Mission-driven

After graduating with a history and literature degree from Harvard, London spent two years in the film industry before deciding she wanted to make a bigger social impact. She did stints at Harvard, supporting health, education, and equity initiatives, and at nonprofit Health Leads, building out its model of community-based care, before earning an MBA at the University of Chicago. Her goal: to move from storytelling to systems thinking, using data to drive change.

That mission drew her to Humedica, a pioneer in leveraging big data in public health. “Sarah sort of cold-called me in 2011,” recalls former CEO Michael Weintraub. “It wasn’t, ‘Hi, hello.’ It was, ‘I researched your company; this is what I work on. I’ve heard about your team; this is who I want to work with.’ We made a decision to hire her that day.”

London rose through the ranks at Humedica, which became part of UnitedHealth Group’s Optum, before joining Centene in 2020. She got the top job there in 2022 after longtime CEO Michael Neidorff stepped down shortly before his death.

Neidorff had built Centene from a regional Medicaid plan in St. Louis with about $40 million in annual revenues to the nation’s largest Medicaid managed care organization. With that growth came a lot of acquisitions and bloat. “The mission orientation was there from the get-go—that’s our superpower—but there hadn’t been as much focus on operating discipline,” says London, who subsequently sold off several noncore operations.

What distinguishes London’s leadership is an ability to connect the dots, says Karen Salfity, whom London brought in from Optum to create a more consistent strategy and member experience. “Sarah can look at a very complex situation, understand the various factors, and then create an assessment … with just enough heart that you know she cares deeply,” says Salfity, who has known London for 15 years. “The only thing that’s really changed is the scale at which she is able to do it.”

A new normal

London knows all too well that a lot of factors in health care are outside her control, not least of which is the Trump administration’s push to radically modernize and streamline federal programs. In February, the administration announced new steps to crack down on alleged fraud in Medicare and Medicaid, on top of the funding cuts and expired ACA tax credits that have already taken effect.

London is not as disheartened as one might think. “You could take a step back and come away with the conclusion that these [programs] are under attack,” she says. But she notes that there was “quite a bit of bipartisan support” for making the sector more efficient.

“I have yet to meet a politician who does not believe that affordable, high-quality health care is something very important to be able to provide for their citizens and voters.”

She sees the current reforms as underscoring the need to take a holistic, high-tech approach to caring for vulnerable populations. Indeed, some of Centene’s systems anticipated the changes that the administration has enacted. “We have work programs in more than 17 states; we partner with nonprofits and provide job training to Medicaid members,” London says. “We run every single claim through 75 algorithms every day to look for fraud, waste, and abuse.”

“Health care is wildly overdue for a digital revolution,” she argues, pointing to an array of tech initiatives that Centene has implemented. Those range from designing supplemental food benefits where there are food deserts—”because we know that if you don’t have access to food, medication adherence goes down”—to predictive algorithms identifying members likely to have high-risk births and mobilizing resources to support them. As London notes, “41% of all babies born in the U.S. are born onto Medicaid”; it’s crucial that the program keeps those children healthy so they can “go and get jobs and contribute to economic mobility and all the things we want as part of the American Dream.”

London knows how tough it is to deliver on that dream. “The country is getting poorer and sicker,” she says. “The dollars are not infinite. At the finite boundaries, you have to make decisions about what you are going to fund and what you are not.”