Daniel Nadler Raised $250 Million to Build AI App For Doctors

When Dr. Stephen Krieger, a neurologist at Mount Sinai, needed guidance on a rare infection, he didn’t reach for a textbook or scroll through outdated medical portals. He opened OpenEvidence, an AI-powered clinical assistant that answers real-time questions using only peer-reviewed medical literature. Before using it on a patient, he ran a test asking the platform to summarize one of his own published studies. The response captured the paper’s findings accurately and it surfaced limitations Krieger hadn’t yet written.

“I thought that was kind of great,” he said.

That interaction is emblematic of a shift happening across U.S. healthcare. OpenEvidence, founded in 2022 by Kensho founder Daniel Nadler and machine learning researcher Zack Ziegler, is becoming the default way doctors access medical knowledge. The app is used in more than 8.5 million patient consultations per month by over 430,000 physicians roughly 40% of all practicing doctors in the U.S. According to the company, one in three Americans this year will be treated by a physician using the platform.

And unlike most enterprise healthcare software, OpenEvidence didn’t get there through hospital procurement. It’s free for verified clinicians. There are no salespeople. Growth has been direct to clinician, viral in nature, built through reputation, not sales decks.