Chai Discovery Raises $400M Series C at $3.8B Valuation for AI Drug Discovery

What happened

Chai Discovery, a San Francisco AI drug discovery startup founded in 2024, closed a $400M Series C on July 14, 2026 led by Index Ventures, with participation from Kleiner Perkins, Sequoia Capital, Dimension, Bain Capital Ventures, Battery Ventures, Baillie Gifford, and others. The valuation reached $3.8 billion — triple the previous round from seven months prior.

Context and impact

AI drug discovery is one of the most promising biotech segments. Chai-3, the company's latest model, improves antibody binding affinity and target identification success rates. The fact that OpenAI is among investors indicates the company sees biological AI as a key strategic market. The customer base includes two of the ten largest pharmaceutical companies in the world.

Details

• Round: $400M (Series C)
• Valuation: $3.8B (3× growth in 7 months)
• Lead investor: Index Ventures
• Also: Kleiner Perkins, Sequoia, Bain Capital Ventures, Baillie Gifford
• Customers: Eli Lilly, Pfizer
• Existing investor: OpenAI
• Product: Chai-3 — model for antibody design and molecular engineering