Chai Discovery’s $400m raise triples its value to $3.8bn in seven months. It is the latest sign that AI drug discovery has moved from promise to deployment.
AI drug discovery just minted another fast-rising star. Chai Discovery has raised a $400m Series C that values the San Francisco startup at $3.8bn, the company said. That is nearly triple the $1.3bn it was worth seven months ago.
Index Ventures led the round. Kleiner Perkins, Sequoia Capital, and Dimension joined, alongside new backers including Bain Capital Ventures, Battery Ventures, and Baillie Gifford. Returning investors OpenAI and Thrive Capital also put in more money.
The raise takes Chai’s total funding above $600m in about eleven months. It closed a $70m Series A in mid-2025, then a $130m round at a $1.3bn valuation in December.
What Chai builds
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Chai was founded in 2024 by Joshua Meier, Jack Dent, Matthew McPartlon, and Jacques Boitreaud. Their backgrounds span OpenAI, Meta’s FAIR lab, and Stripe. The pitch is to design new medicines rather than stumble on them.
Most drug discovery screens vast libraries of existing molecules. Chai instead uses generative AI to design new antibodies and proteins from scratch, tuned to a disease target before they reach a lab.
Its 2025 model, Chai-2, was the first zero-shot system for fully de novo antibody design to hit double-digit success rates in the lab. The company calls that a hundredfold jump over older methods. Its newer Chai-3 model binds more tightly to harder targets.
Pharma is already buying
The technology is not stuck in research. Chai says its models are deployed at Eli Lilly, Pfizer, and Novartis. It added a collaboration with the immunology firm argenx this week.
That commercial traction is the pitch. Big drugmakers rarely trust unproven software, so paying customers at that scale set Chai apart from most AI startups chasing the same problem.
A crowded, richly funded field
Money is pouring into AI-designed medicine. Isomorphic Labs, Google DeepMind’s drug-discovery spinout, closed a $2.1bn round in May, and it also counts Novartis as a partner. Xaira Therapeutics launched with $1bn, and Recursion has raised more than $1bn.
The big AI labs are circling too. Anthropic paid about $400m for a small drug-design startup, and ByteDance has entered the race. Academics such as Stanford’s James Zou are building their own AI-biology firms.
Analysts put the AI drug-discovery market at about $2.35bn in 2025, growing to $13.7bn by 2033. Chai’s value tripling in seven months suggests investors are moving faster than the forecasts.
The catch
The hard part comes next. A model can generate candidate molecules in minutes. Those molecules still face years of lab work, clinical trials, and regulators before they reach patients.
Chai and its rivals are betting the next medicines will be designed, not discovered. Whether that belief survives the first wave of clinical failures is what a $3.8bn price tag is really testing.
