A medical search tool used by doctors is at the center of a fast-growing business and a debate about AI in patient care. OpenEvidence says physicians processed more than 42 million prompts last month, and the company reached a $15 billion valuation in its latest funding round.
A clinical search tool finds an audience
Founded by serial entrepreneur Daniel Nadler in 2022, Miami-based OpenEvidence uses a chatbot to search medical journals and clinical guidelines. Doctors use it to help with diagnoses and treatment decisions. Its focused source list includes peer-reviewed publications such as the New England Journal of Medicine and the Journal of the American Medical Association.
The company says many of America’s 1 million physicians used the tool, and its growth has come largely through word of mouth. Interviews with eight senior physicians found praise for its ability to ease workloads. Nina Singh, a medical resident at the University of California San Francisco, said the system lets her provide patient context, find information and make decisions faster.
OpenEvidence has also found a place in some healthcare organizations. Mount Sinai Health System and Memorial Sloan Kettering Cancer Center in New York have embedded it in electronic health records. NYU Langone pursued a formal tie-up after clinicians were already using it as an independent resource, according to Paul Testa, the hospital system’s chief health informatics officer.
That integration is intended to help clinicians use AI tools securely and get more from them, Testa said. The company has also expanded into ambient documentation, which involves taking notes during doctor-patient interactions.
Advertising fuels growth and raises questions
OpenEvidence’s business relies on advertising. A person close to the company said it booked $100 million in “ad buys”—a measure covering current and future advertising commitments—for this year at the end of 2025. The person said the startup is on track to generate between $400 million and $500 million through ads by the end of 2026.
The company raised $250 million in its latest funding round in September at a $15 billion valuation. It has attracted nearly $1 billion in investment in the past 18 months, with backers including Andreessen Horowitz, Blackstone, Thrive Capital, and Sequoia. The scale of that fundraising has brought attention to whether an advertising-based business model can support the valuation.
OpenEvidence entered a medical software market where generative AI adoption had been slow. Dutch IT group Wolters Kluwer released an AI version of its subscription-based UpToDate tool in October 2025, nearly two years after OpenEvidence entered the market. The startup’s early popularity among doctors is one argument its supporters make for its position against both established providers and newer rivals.
Evidence of performance is mixed
Studies have not reached a simple verdict on how well OpenEvidence performs. A Mayo Clinic study, from an institution that is also an investor in the startup, found that the tool “provided accurate, evidence-based recommendations” in all five sampled patient case studies. The study also found a more limited impact on treatment decisions.
Other research has raised concerns. A June paper published in Nature found that OpenEvidence underperformed general-purpose AI models such as Google’s Gemini and OpenAI’s GPT on clinical benchmarks. Eric Oermann, a neurosurgeon at NYU Langone, pointed to limited research into individual AI tools and scant guidance on putting them into clinical practice.
That uncertainty matters because the tool is used to inform care. Concerns include whether junior doctors might rely too heavily on AI before mastering the relevant medical knowledge and treatment options. The debate is not only about a system’s performance on a test; it also involves how doctors use its answers in real clinical decisions.
Expansion brings new competition and ambitions
OpenEvidence faces competition from large AI companies entering healthcare, including OpenAI and Anthropic. OpenAI has brought ChatGPT for healthcare to the space, while Anthropic has released healthcare tools and recently partnered with OpenEvidence to make tools available in 100 low- and middle-income countries.
Supporters argue that voluntary adoption by doctors gives OpenEvidence an advantage. The company’s expansion plans go beyond clinical search: Nadler said it will launch clinical trials in the coming weeks, working with researchers on cancer and rare diseases. It also plans to apply AI models to drug discovery and use existing scientific literature to generate new hypotheses.
Nadler described literature-based drug discovery as the company’s long-term goal, saying its economic value could exceed what it could charge hospitals or advertisers. For now, OpenEvidence’s growing presence puts two questions side by side: whether doctors continue to find the tool useful, and whether evidence and clinical guidance can keep pace with its use.