Chai Discovery, the San Francisco startup engineering AI models for drug discovery, has raised a $400 million Series C at a $3.8 billion valuation to accelerate development of its generative molecular-design platform. Announced on July 14, 2026, the round is led by Index Ventures alongside Kleiner Perkins, Sequoia Capital, and Dimension.
An investor roster that dwarfs most biotech rounds
New investors in the round include Bain Capital Ventures, Battery Ventures, Baillie Gifford, BDT & MSD, Sapphire Ventures, and Avra Capital. They join existing backers Thrive Capital, OpenAI, Oak HC/FT, Menlo Ventures, General Catalyst, Glade Brook, Avenir, Lachy Groom, and Yosemite. The mix — Silicon Valley venture capital, pharma-savvy growth investors, and a strategic tie to OpenAI — mirrors the hybrid infrastructure Chai's founders came from.
Chai-3 pushes zero-shot antibody design forward
The startup's software puts its generative models into the hands of scientists at Eli Lilly, Pfizer, and other leading pharmaceutical companies. Its latest model, Chai-3, materially improves binding affinity over its predecessor. Chai-2, released in 2025, was the first zero-shot generative platform for fully de novo antibody design to hit double-digit experimental success rates — a step change over prior computational methods.
Founders from OpenAI, Meta FAIR and Stripe
Chai Discovery was founded in 2024 by Joshua Meier (co-founder and CEO), Jack Dent, Matthew McPartlon, and Jacques Boitreaud, with backgrounds spanning OpenAI, Meta FAIR, Stripe, and academic molecular design research. "AI drug discovery has moved from promise to deployment," Meier said in a statement, "and Chai's models are already unlocking progress for our partners." Index Ventures partner Nina Achadjian said the team is "already there, with deployments at the world's largest pharma companies."
Where the round fits in a hot AI-biotech cycle
The Chai raise lands in a market where AI drug-discovery funding has topped $2 billion in recent months. It follows other high-profile 2026 rounds — including CuspAI's $450M Series B — as investors bet that generative models can compress drug discovery timelines from years to months. Chai has said the fresh capital will go toward scaling infrastructure and expanding partnerships across "undruggable" target classes.
Reporting based on coverage from BioSpace, BusinessWire, and Chai Discovery.