AI-driven drug discovery keeps attracting megarounds even as public markets wobble. Chai Discovery, which builds AI models for molecular design, said on July 14, 2026 that it raised a $400 million Series C led by Index Ventures, with Kleiner Perkins, Sequoia Capital and Dimension joining, at a $3.8 billion post-money valuation.
A valuation that tripled in seven months
The new price is roughly triple the company's $1.3 billion valuation from December 2025 — a jump compressed into about seven months — and lifts total funding to around $630 million. Existing backers span the AI and venture worlds: Thrive Capital, OpenAI, Menlo Ventures and General Catalyst were already on the cap table before this round.
What Chai builds
Founded by CEO Joshua Meier, Chai develops models that predict and reprogram molecular interactions — the core problem in designing drugs that bind their targets. Its latest system, Chai-3, is pitched as a tool for generating and validating candidate molecules, with a particular focus on AI-designed antibodies. The company frames its models as moving beyond structure prediction toward actively designing therapeutics.
Big-pharma validation
The commercial signal is the customer list. Chai counts Pfizer, Eli Lilly and Novartis among its partners — the kind of names that turn a research lab into a platform business. Getting AI-designed candidates into the pipelines of the largest drugmakers is the bet investors are underwriting at $3.8 billion.
The category's momentum
Chai's raise lands amid a broader surge in AI-for-biology funding, where investors are paying up for "capital-efficient defensibility" — models that solve a systemic bottleneck rather than chase consumer scale. A tripled valuation in seven months, backed by both tier-one venture firms and OpenAI, underscores how quickly molecular-design AI has moved from promising research to a contested, well-capitalized market.