When Daniel Nadler and Zachary Ziegler launched OpenEvidence just three years ago, few could have predicted it would become the fastest-growing AI tool powering nearly half of US doctors’ clinical decisions. Today, the startup – dubbed “ChatGPT for doctors” – just hit a valuation of $12 billion, cementing its role in the future of healthcare technology.
OpenEvidence’s rapid rise reflects a broader shift in how specialized AI applications are reshaping professional workflows. Unlike broad AI tools, this platform is purpose-built to serve doctors by sifting through peer-reviewed medical literature and surfacing precise answers tailored to complex clinical questions – all within seconds.
He bet big on doctors – and it paid off
Daniel Nadler is no stranger to building AI companies. Raised in Toronto and trained at Harvard, he previously founded Kensho Technologies, an AI analytics startup that was acquired by S&P Global in 2018 for roughly $550 million.
With OpenEvidence, he put significant skin in the game – investing $10 million of his own money and retaining a majority ownership stake estimated at around 58%. That bet has paid off quickly. Recent estimates by Forbes put the founder’s net worth at about $7.6 billion, more than double what it was just a few months ago.
He’s joined by cofounder and CTO Zachary Ziegler, whose background in natural language processing research at Harvard helps power the technical backbone of the platform.
Why AI for doctors is suddenly big business
At its core, OpenEvidence functions as an AI-driven clinical decision support tool. Its search engine indexes millions of peer-reviewed studies, multimedia, and other verified clinical content, providing doctors quick access to evidence-based answers during patient care.
The platform’s strength lies in its specialized “expert” AI models that focus on domains like oncology, radiology, and neurology, mimicking the structure of a hospital by routing queries to the right expert model.
More than 740,000 US physicians – roughly 45% of the doctor population – now use the platform regularly. Last month alone, the software supported some 18 million clinical consultations. These numbers signal that OpenEvidence is not just a tool but an operational system embedded in frontline medicine.
Despite its role, OpenEvidence has chosen an ad-supported model that carefully balances revenue generation with user trust.
Pharmaceutical and medical device companies buy targeted, brief video ads based on the clinical search queries, but the founders have held back from monetizing fully to avoid compromising the physician experience. The startup surpassed $100 million in annualized revenue in 2025, with potential to scale much further.
The recent $250 million Series D round led by Thrive Capital and DST Global doubled the startup’s valuation to $12 billion, bringing total funding to approximately $700 million.
The future of healthcare depends on (even more) trust
With growing use from clinicians and enough funding to keep building, OpenEvidence appears well positioned to keep improving its medical AI tools. The company’s leadership has described its approach as bringing together many specialized AI systems, rather than relying on one all-purpose model – an idea that reflects how complex medical decision-making really is.
As AI becomes more common in healthcare, companies like OpenEvidence highlight an important point: success isn’t just about powerful technology. It’s about earning the trust of doctors and other professionals who rely on accurate, reliable information.
Instead of one giant AI dominating medicine, the future is likely to be shaped by smaller, focused tools built by teams with deep expertise in specific fields.
