Nearly two-thirds of US doctors are turning to an AI-powered search engine to make patient decisions, propelling a little-known tech startup to a $15 billion valuation while prompting a debate over the future of patient care.
Miami-based OpenEvidence, founded by serial entrepreneur Daniel Nadler in 2022, said that many of America’s 1 million physicians processed more than 42 million prompts last month. Doctors are using the company’s chatbot to scour medical journals and clinical guidelines to help diagnose and treat patients.
The ads-powered platform has grown largely by word of mouth, penetrating a sector where few tools have seen similar traction. “We’re the first viral consumer internet app in healthcare,” Nadler told the FT in an interview.
OpenEvidence has won praise from medical professionals who have found it helped ease workloads, according to interviews with eight senior physicians.
But it faces a nascent threat from large AI companies such as OpenAI and Anthropic, who are making a push into the space. Its growing influence has also prompted scrutiny from researchers concerned over the accuracy of its results, as doctors grow more dependent on an AI tool shaping the course of treatments.
The company’s rapid ascent has attracted nearly $1 billion in investment in the past 18 months, from backers including Andreessen Horowitz, Blackstone, Thrive Capital, and Sequoia. The group raised $250 million in its latest funding round in September at a $15 billion valuation.
OpenEvidence booked $100 million in “ad buys”—a metric that covers current and future advertising commitments—for this year at the end of 2025, according to a person close to the company. The startup is on track to generate between $400 million and $500 million through ads by the end of 2026, the person added.
Nadler’s company has penetrated an established market for medical software that was sluggish to incorporate generative AI models. Dutch IT group Wolters Kluwer released an AI version of its leading subscription-based UpToDate medical software tool in October 2025, nearly two years after OpenEvidence entered the market.
Central to OpenEvidence’s pitch is a focusedgland Journal of Medicine and the Journal of the American Medical Association
“OpenEvidence allows me to provide a lot of context about my patient, find information, and make decisions faster,” said Nina Singh, a medical resident at the University of California San Francisco. “It’s a really useful tool.”
Widespread appeal has helped OpenEvidence forge relationships with several hospitals and specialist clinics such as Mount Sinai Health System and Memorial Sloan Kettering Cancer Center in New York, embedding its tool within the organizations’ electronic health records.
Paul Testa, chief health informatics officer at NYU Langone, said that the hospital system sought a formal tie-up with OpenEvidence after it found clinicians were already using the tool as an “independent resource.”
“We chose to deeply integrate a clinically informed version of OpenEvidence into the care process to ensure two things: first, our clinicians can get the most from these AI tools, and second, they use them securely,” he said.
OpenEvidence has leveraged its popularity with doctors to slowly expand into other domains, including ambient documentation—note-taking during doctors’ patient interactions.
Critics have questioned whether the company’s ad-based model warrants its high valuation, while its decision to withdraw from the EU and UK earlier this year over the bloc’s AI Act has stymied its expansion into two key markets.
Mike Vernal, a partner at venture firm Conviction and an OpenEvidence investor, said that the company’s popularity among physicians represented its strongest defense against startup rivals and incumbents.
Nadler said it will also launch clinical trials in the coming weeks, partnering with researchers to target cancer and rare diseases. It plans to apply AI models to drug discovery and draw on pre-existing literature to generate novel scientific hypotheses.
“The end game is literature-based drug discovery,” Nadler said, referencing the field of data mining scientific literature for insights. “The economic value of that as a company is going to dwarf by orders of magnitude whatever we could have charged hospitals or advertisers.”
Alexander Tarashansky, the creator of Claude Science, an Anthropic platform that supports research scientists, has also joined the company to support its clinical work.
The company needs to see off competition from frontier AI companies such as OpenAI, which has also made a play for the space with ChatGPT for healthcare. Anthropic has also released healthcare tools, though it recently partnered with OpenEvidence to bring the tools to 100 low- and middle-income countries.
“The fact that doctors are adopting and using a piece of software of their own volition means there is a degree of differentiation that OpenEvidence can really lean on,” said Nworah Ayogu, a partner at investor Thrive Capital.
But analysis of OpenEvidence’s effectiveness has led to mixed results.
One study by the Mayo Clinic, an investor in the startup, found that it “provided accurate, evidence-based recommendations” in all five patient case studies that were sampled, although its impact on treatment decisions was more limited.
Other research, including a June paper published in Nature, found that it underperformed general-purpose AI models such as Google’s Gemini and OpenAI’s GPT on clinical benchmarks.
Eric Oermann, a neurosurgeon at NYU Langone, said there was a lack of research into the performance of individual AI tools and scant guidance on how to implement the tools in a clinical setting.
There are also widely held concerns that more junior doctors could fall foul by relying too heavily on OpenEvidence and other systems without first mastering basic knowledge of particular conditions and their prescribed treatment options.
“It’s a fun, friendly competitive pressure to play with benchmarks… [But] there’s no question of what AI tool physicians trust and use,” Nadler said.
Additional reporting by George Hammond in San Francisco.
Financial Times
Financial Times
Source: arstechnica.com
