Chai Discovery raises $400M at $3.8B valuation for AI molecule design
Chai Discovery, a San Francisco company founded in 2024, announced a $400 million Series C on July 14, 2026 at a $3.8 billion valuation. Index Ventures led the round alongside Kleiner Perkins, Sequoia Capital and Dimension, with OpenAI and Thrive Capital among the returning investors. Chai builds AI models that predict and redesign interactions between molecules. Pharmaceutical companies including Eli Lilly, Novartis and Pfizer use them in preclinical drug design. The company has now raised more than $600 million, across three rounds in under a year.
Why it's notable: This is one of the largest venture rounds for an AI drug-design company, and big drugmakers already use Chai's models. Investors are betting that AI-designed molecules will shorten early drug discovery.