The bottom line
According to a Financial Times article published on October 21, 2026, the AI system OpenEvidence, built for searching medical literature, is now used by two-thirds of the nearly 1 million physicians in the US. A source close to the company told the publication that the ad-supported product is expected to bring in $400–500 million in ad revenue in 2026 — one of the biggest investment stories in medical AI.
In September 2026, the company closed a $250 million funding round with participation from Andreessen Horowitz, Blackstone, Thrive Capital, and Sequoia Capital. As a result, OpenEvidence was valued at $15 billion — a significant jump from $12 billion in January 2026.
"The $15 billion ad-powered AI startup your doctor may already be using" — Ars Technica
OpenEvidence was founded in 2022 by Daniel Nadler and Zachary Ziegler in Miami. The system gives physicians evidence-based answers across medical journals and clinical guidelines. According to the company, physicians send more than 42 million prompts a month.
Two-thirds of nearly a million physicians means two out of every three doctors already turn to this system in their daily work. That kind of reach signals unusually fast adoption for a four-year-old company — and that pace is likely the main reason investors signed off on the $15 billion valuation.
OpenEvidence is free for physicians — revenue comes from advertising sold to pharmaceutical companies. Ads appear alongside answers. Citing a source close to the company, the Financial Times reports that ad revenue is projected to reach $400–500 million by the end of 2026.
The valuationʻs rise from $12 billion to $15 billion in eight months is striking: this growth is a bet not on the companyʻs current revenue, but on the growth rate of its user base. In other words, the market is valuing OpenEvidence not for todayʻs ad revenue, but for tomorrowʻs share of the medical search market. That valuation logic cuts both ways — if growth continues, the valuation keeps rising; if it stalls, the correction could be sharp. So this story reads not just as financial news, but as a new chapter in the debate over AIʻs role in medicine.
The Ad-Supported Business Model
Critics ask whether the advertising model justifies a $15 billion valuation, and the question of how the conflict of interest between advertisers and clinical answers is managed remains open.
The notable thing here is that the payer and the user are not the same person. The physician uses the service for free; pharmaceutical companies foot the bill. While this "user doesnʻt pay" model is widespread in internet services, in the context of medical decisions it naturally raises the question: does the advertising next to the answers affect the clinical content itself? That question is at the heart of the "questions about advertising" mentioned by Ars Technica — and for now it remains unanswered.
Accuracy Questions
There are also questions about the systemʻs accuracy. A study published in Nature found that OpenEvidence scored below Google Gemini and OpenAI GPT on some clinical benchmarks. At the same time, an accuracy study by Mayo Clinic came out in the companyʻs favor.
Ars Technica wrote that the system is "thriving despite questions about accuracy and advertising."
The critical conclusion in Nature and the positive one from Mayo Clinic donʻt actually contradict each other: the former compared OpenEvidence against the most advanced general models, while the latter measured its absolute clinical accuracy. In other words, the system can be both "accurate enough to use" and "behind the strongest competitors" at the same time. For physicians, that distinction isnʻt theoretical — in daily decisions they rely on exactly the answers this system shows. This shows that a single metric isnʻt enough to evaluate medical AI tools: there can be a gap between a lab benchmark and real clinical use.
Leaving Europe and Competition
OpenEvidence has official integrations with major medical institutions: Mount Sinai Health System and Memorial Sloan Kettering Cancer Center have connected the system to their electronic health records. But earlier this year, the company exited the European Union and United Kingdom markets — citing the costs of complying with the AI Act as the reason. Closing off these two large markets also shows the limits of growth.
The decision to leave the EU and UK signals the companyʻs strategy: regulatory costs weigh heavily even on a startup valued at $15 billion. In other words, OpenEvidence chose to keep growing precisely in markets with lighter regulatory burdens. The consequences of that choice will show in the pace of expansion in the coming quarters.
Primary sources: Financial Times, Ars Technica.
