Chai Discovery Secures $400M Series C to Propel AI-Driven Molecular Innovation

Chai Discovery, a company focused on engineering AI models for the discovery of new molecules, has announced a $400M Series C funding round aimed at accelerating its advancements in the field. This funding round, which values the company at $3.8 billion, was led by Index Ventures, with participation from Kleiner Perkins, Sequoia Capital, Dimension, and several existing investors.

"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," commented Nina Achadjian, partner at Index Ventures. New investors such as Bain Capital Ventures, Battery Ventures, and Baillie Gifford joined existing backers like Thrive Capital and OpenAI in this substantial investment.

Chai Discovery specializes in building AI models that enhance the pre-clinical drug discovery process by predicting and reprogramming molecular interactions. Their software platform empowers scientists at prominent pharmaceutical companies, including Eli Lilly and Pfizer, to tackle some of the most challenging issues in drug development, such as designing therapeutics for "hard to drug" and "undruggable" targets.

“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. He added, “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.”

The latest model from Chai, known as Chai-3, significantly enhances target success rates and binding affinity compared to earlier versions, producing antibodies that bind more tightly to their intended targets. Chai-2, which was released in 2025, was notable for being the first zero-shot generative platform for de novo antibody design, achieving double-digit experimental success rates.

"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," reiterated Nina Achadjian from 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," stated 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,” expressed 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 envisions a future where new medicines are crafted with the precision, speed, and scale of modern engineering, rather than through traditional trial and error. The company's models are designed to reason about biological structure and function, generate new molecular designs from scratch, and assist pharmaceutical teams in pursuing challenging targets.

Founded in 2024 by Joshua Meier, Jack Dent, Matthew McPartlon, and Jacques Boitreaud, Chai Discovery is headquartered in San Francisco, California. The founding team, with backgrounds from OpenAI, Meta FAIR, Stripe, and academic research, is united by a vision to apply engineering principles to one of science's toughest challenges: creating better and faster therapeutics for the most challenging "undruggable" targets.