Chai Discovery has closed a $400 million Series C funding round, pushing its valuation to $3.8 billion and bringing total funding past $600 million. The San Francisco startup builds AI models that predict and reprogram molecular interactions for drug discovery.
Founded in 2024, Chai has moved fast — raising a $30 million seed round, launching its Chai-1 model, and iterating through Chai-2 and Chai-3 within two years. Its technology is already in use at three of the world’s largest drugmakers: Eli Lilly, Novartis and Pfizer, all of which signed collaboration deals this year.
The Series C was led by Index Ventures, Kleiner Perkins and Sequoia Capital, with all three citing real-world pharmaceutical adoption as the reason for their investment. “AI drug discovery has moved from promise to deployment,” said CEO Joshua Meier in a statement. Companies are using Chai’s models to “design better molecules, move faster against difficult targets and take on challenges that traditional discovery methods have struggled to solve,” he added.
Chai has backed its claims with preprint data. One study showed its Chai-2 model achieved a 16% hit rate in fully de novo antibody design when given a defined epitope — roughly 100 times better than earlier computational methods. A subsequent paper demonstrated that the resulting antibodies have drug-like properties and can hit traditionally hard targets.
The round also included participation from Dimension and existing backers. Chai has disclosed few specifics about its next steps beyond plans to “further accelerate progress.” The company’s rapid fundraising trajectory — from seed to Series C in under 18 months — reflects sustained investor appetite for AI platforms that can deliver tangible drug discovery outcomes.
