- Round led by Index Ventures, alongside Kleiner Perkins, Sequoia Capital, Dimension and existing investors, values company at $3.8B
- Chai’s AI models generate new molecular designs from scratch, helping partners including Eli Lilly and Pfizer pursue targets that traditional discovery methods struggle to reach
SAN FRANCISCO--(BUSINESS WIRE)--Chai Discovery, the company engineering AI models to discover new molecules, today announced a $400M Series C fundraise to further accelerate progress.
The round, which values the company at $3.8B, was led by Index Ventures alongside Kleiner Perkins, Sequoia Capital and Dimension.
These firms were joined by new investors Bain Capital Ventures, Battery Ventures, Baillie Gifford, BDT & MSD, Sapphire Ventures, Avra Capital, and other notable investors. Existing investors Thrive Capital, OpenAI, Oak HC/FT, Menlo Ventures, General Catalyst, Glade Brook, Avenir, Lachy Groom, and Yosemite also joined the round.
Chai Discovery builds AI models to accelerate pre-clinical drug discovery, predicting and reprogramming the interactions between molecules. Its software platform puts those models into the hands of scientists at leading pharmaceutical and life sciences companies, including Eli Lilly and Pfizer, to bring the precision and predictability of engineering to one of the hardest problems in science - better, faster therapeutics, for even the toughest "hard to drug” and “undruggable” problems.
“Tomorrow’s medicines should be designed with the precision, speed and scale of modern engineering, and this support helps us move faster towards that future,” said Joshua Meier, co-founder and CEO of Chai Discovery. “AI drug discovery has moved from promise to deployment, and Chai’s models are already unlocking progress for our partners—enabling them to design better molecules, move faster against difficult targets, and take on challenges that traditional discovery methods have struggled to solve.”
Its latest model, Chai-3, materially improves target success rates and binding affinity compared to its predecessor, producing antibodies that bind substantially more tightly to intended targets. Chai-2, released in 2025, was the first zero-shot generative platform for fully de novo antibody design to achieve double-digit experimental success rates, representing a step-change over prior computational methods.
"It's rare to find founders who have the technical brilliance to push the frontier and the clarity to turn that into real commercial traction," said Nina Achadjian, partner at Index Ventures. "From the moment I met this team, I knew they were the ones to tackle one of medicine's hardest problems. Josh, Jack, Matt, Jacques and the team aren't building toward real-world deployment — they're already there, with deployments already at the world's largest pharma companies. We're excited to partner with the Chai team as they build the platform for a new era of drug discovery."
“At Kleiner Perkins, we’ve always believed the most important companies begin with a fundamental truth and a team with the ambition, clarity, and velocity to build something enduring,” said Ilya Fushman, partner at Kleiner Perkins. “Chai has both. Their models are already being used by some of the world’s largest pharma companies, and the speed at which this team is advancing the frontier, technically and commercially, is remarkable. Drug discovery is being transformed by AI, and Chai is building the platform that can help define what comes next.”
"Drug discovery is one of the hardest problems in science. For a long time, there's been a dream that AI will solve it," said Pat Grady, partner at Sequoia Capital. "Chai's product velocity and real-world partnerships with Eli Lilly, Pfizer, and more of the biggest names in pharma are starting to turn this dream into a reality. Josh and Jack move with a focus and precision that are rare in this space."
“This is the largest check we’ve ever written at Dimension, and we are beyond thrilled for this next phase of growth and continued acceleration of R&D for the Chai team,” said Zavain Dar, founder at Dimension. “As the pre-eminent firm at the intersection of science and compute, we bring a discerning approach to evaluating the companies in our portfolio. As early investors in Chai, our strong conviction in the team and their lightning speed innovation has only grown over time. We are excited to be on this journey with them.”
About Chai Discovery
Chai Discovery is building a world where new medicines are not found through trial and error, but designed with the precision, speed and scale of modern engineering. Chai’s models are designed to reason about biological structure and function, generate new molecular designs from scratch, and help pharma teams pursue targets that traditional discovery methods have struggled to reach.
Founded in 2024 by Joshua Meier, Jack Dent, Matthew McPartlon and Jacques Boitreaud, Chai Discovery is based in San Francisco, California. With backgrounds spanning OpenAI, Meta FAIR, Stripe, molecular design and academic research, the team shares a singular vision: to bring the precision and predictability of engineering to one of the hardest problems in science - better, faster therapeutics, for even the toughest 'undruggable' targets.
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