Chai Discovery, a San Francisco startup that uses AI to design new drug molecules, said on July 14 it raised a $400 million Series C round led by Index Ventures, valuing the company at $3.8 billion.
What the round funds
Kleiner Perkins, Sequoia Capital and Dimension joined the round alongside new backers including Bain Capital Ventures, Battery Ventures and Baillie Gifford, plus existing investors such as Thrive Capital, OpenAI and General Catalyst, the company said in a statement. Founded in 2024 by CEO Joshua Meier and co-founders Jack Dent, Matthew McPartlon and Jacques Boitreaud, Chai Discovery builds AI models that predict how molecules interact and generate entirely new candidate molecules, rather than merely screening existing compound libraries.
From screening to design
The company’s Chai-2 model, released in 2025, was described as the first zero-shot generative platform for designing antibodies from scratch, reporting double-digit success rates in laboratory testing without prior examples of a working binder. Its successor, Chai-3, further improves target “hit” rates and binding affinity, according to the company. Pharmaceutical giants Eli Lilly and Pfizer are among the partners already using Chai’s models to pursue drug discovery targets that traditional methods have struggled to reach.
Why it matters
“AI drug discovery has moved from promise to deployment, and Chai’s models are already unlocking progress for our partners,” CEO Joshua Meier said in the announcement. The raise adds Chai Discovery to a small cluster of AI-native biotech startups — alongside firms working on protein structure prediction and generative chemistry — that have drawn large late-stage rounds this year as pharmaceutical companies look for ways to cut the yearslong, multibillion-dollar cost of bringing a new drug to market.