OpenEvidence: Just What the Doctor Ordered

photo by OpenEvidence

Doximity spent eleven years building a base of 300,000 quarterly active prescribers before it went public at a $10 billion market cap in 2021. OpenEvidence got to comparable physician reach in roughly eleven months. We've looked at a lot of adoption curves in private markets but this one truly stands out. Taking a step back, the curve makes sense when you dig into what doctors actually choose and where the money is actually moving. On both questions, third-party data published this summer gave us confidence in the underlying traction.

Taken daily, as directed

OpenEvidence started in 2021 essentially as a search engine built for doctors. It is trained on licensed medical literature and made available free to any licensed clinician in the US, with access verified by NPI number or a hospital email. Founder Daniel Nadler had already sold one AI company, Kensho, to S&P Global and he built this one on the same bet: a narrow model grounded in the right data beats a general one in a field where being wrong has heavy costs.

The usage is what convinced us. Company-reported clinical queries grew from roughly 2.6 million a month in December 2024 to roughly 27 million this April, and the company says the platform is now used daily by physicians across more than 10,000 hospitals and care centers. Coatue, an investor in the company, reported last year that doctors spend an average of 13.3 minutes per session on the platform, which is several times what they spend on adjacent tools. Nobody sits with a free tool for thirteen minutes out of curiosity. They do it because it replaced something in their day.

Checking the vitals: Doximity vs OpenEvidence valuation:

Ask your doctor

That usage is backed up anecdotally (ask your doctor next time you see them) and in external research. In an independent study posted in July, 101 board-certified U.S. physicians worked through specialist consultation cases and were left free to consult whatever resources they wanted. Given that free choice, they selected OpenEvidence more often than every general-purpose AI chatbot combined, with 22.3% of responses, versus 19.8% for ChatGPT, Claude, Gemini and the rest put together.

The same study is also a useful reality check, showing that across the AI tools tested, up to a quarter of recommendations carried the potential for severe harm if applied blindly, with errors of omission dominating. That said, the purpose-built, citation-grounded clinical tools outperformed generalist chatbots in the study, which is the design bet OpenEvidence made from day one.

Direct to physician

OpenEvidence makes money the way a search engine does, with the product free to use, funded by pharma and med-device advertising delivered at the moment of clinical decision-making. A July 2026 Wells Fargo Securities survey of 30 pharma HCP digital ad buyers gives good insight into underlying advertising trends that are moving in OpenEvidence’s favor. 

Based on the survey results, Doximity is positioned as the incumbent while OpenEvidence is the share-taker. Doximity anchors the category with 100% adoption and roughly a quarter of healthcare professional (HCP) digital budgets. But OpenEvidence posted the largest share gain of any platform in the survey, rising some ~200bps to ~7% of budgets. Vendor-specific spend growth on OpenEvidence was estimated at ~13% in 2026, roughly double its 2025 pace and the strongest acceleration surveyed. In addition, HCP digital is the one pharma ad budget line accelerating in 2026 while overall digital and DTC decelerate, adding another tailwind to the sector.

Admitted to the hospital

Bottoms up viral-like usage and peer referrals got OpenEvidence in the door, while supported by advertising. The EHR represents the potential next stage of top-down adoption. Four hospital systems (Sutter, Mount Sinai, Cedars-Sinai, and Boston Children's) have signed on for full electronic health record integration within six months of each other, which turns a tool a doctor opens on the side into one embedded in the chart they're already working from. Going forward, ripping out a workflow tool is likely harder than ignoring a banner ad.

It also changes who pays and how much. Enterprise, EHR-embedded relationships can price well above what a free, ad-supported app collects per user, which is one reason the company can eventually be much larger than its current ad revenue suggests. Four hospital systems is a start worth tracking as OpenEvidence looks at potential category expansion.

Risks we’re watching

The NOHARM July study showed minimal separation between Germany-based AMBOSS, Doximity Ask and OpenEvidence on clinical accuracy, while acknowledging the gaps that AI diagnosis tools in general present. OpenEvidence’s exit from the EU and UK markets this April following the AI Act disruption also narrows the near-term map. Litigation with Doximity is unresolved (OpenEvidence claims the rival impersonated doctors to try to steal product secrets; Doximity counter-sued alleging false advertising and other issues), and the company's public handling of a recent research dispute generated controversy. As the NOHARM work shows, clinical AI safety will be an important regulatory topic to watch.

Our diagnosis

Funds managed by PEP hold an indirect position in OpenEvidence through a third-party special purpose vehicle, acquired in a secondary transaction in August 2026. The pattern we look for in private markets is a product that has already shown exceptional traction (i.e. becoming a daily habit for professionals who don't change habits easily), with a potential second act underway that the market hasn't fully priced. Independent physician preference data, accelerating third-party ad-spend evidence, and early EHR embedment give us important data points in our diagnosis. So far, OpenEvidence is just what the doctor ordered.

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