Chai Discovery, a San Francisco company that builds AI models for designing molecules, raised $400m in a Series C led by Index Ventures. The round values the company at $3.8bn, up from $1.3bn in December 2025, The Next Web reported.
Kleiner Perkins, Sequoia Capital and Dimension also took part, according to Chai's announcement. The Next Web added that new backers include Bain Capital Ventures, Battery Ventures and Baillie Gifford, while OpenAI and Thrive Capital returned as investors. The company's announcement is dated 14 July 2026, and The Next Web cited a Business Wire release from 13 July.
The Next Web put Chai's total funding at more than $600m in about eleven months.
What Chai Discovery does
Chai says it is building frontier AI to predict and reprogram interactions between biochemical molecules. Its 2025 model Chai-2 was described by The Next Web as the first zero-shot system for fully de novo antibody design to reach double-digit lab success rates, which the company calls a hundredfold improvement over older methods.
Its latest model, Chai-3, binds more tightly to harder targets, according to the report. The company's announcement said Chai-3 is unlocking targets that have long resisted traditional computational and laboratory methods.
Chai was founded in 2024 by Joshua Meier, Jack Dent, Matthew McPartlon and Jacques Boitreaud, who previously worked at OpenAI, Meta's FAIR lab and Stripe. Headcount and revenue were not disclosed.
Customers and partners
Chai said Eli Lilly, Pfizer and Novartis have started adopting its models across their organisations. The Next Web, citing the company, also reported a collaboration with the immunology company argenx, announced the same week as the funding.
These customer claims come from the company and were not independently verified.
The funding so far
Chai raised a $70m Series A in mid-2025 and a $130m round in December 2025 at the $1.3bn valuation, The Next Web reported. The Series C brings the total above $600m.
The company said the new money will expand the compute, data and research behind its models, speed up product development and bring the technology to more scientists.
A crowded field
AI drug discovery has drawn large rounds as investors back companies that claim to design medicines rather than search for them. The Next Web used the phrase "designed, not discovered" for that goal. Chai's valuation jump in seven months shows how quickly the leading startups in the field are being repriced.
How the valuation moved
The Series C values Chai at $3.8bn, about 2.9 times the $1.3bn set in the December 2025 round. The Next Web said that step-up came in roughly seven months.
The three rounds reported so far, $70m, $130m and $400m, add up to $600m, which matches the figure of more than $600m raised in about eleven months. The company did not disclose revenue, so the valuation cannot be compared with sales.
Company website: chaidiscovery.com