Chai Discovery's open-model bet: $30M seed to a $1.3B AI drug designer

AI biotech building open foundation models (Chai-1, Chai-2) that predict molecular structures and design antibodies from scratch for drug-discovery partners.

That one open, multimodal foundation model can predict and reprogram interactions between any biochemical molecules — turning drug discovery from screening into design.

$30M seed led by Thrive Capital with OpenAI and Dimension (Sept 2024); then $70M Series A (Aug 2025) and $130M Series B (Dec 2025)

Founded in London in 2024 by Joshua Meier (ex-OpenAI, Facebook AI and Absci), Jack Dent (ex-Stripe) and AI researchers Mathew McPartlon and Jacques Boitreaud. Meier had led AI at drug-discovery companies and believed biology could be engineered rather than screened. The seed, led by Thrive Capital with OpenAI and Dimension, valued the six-month-old company at $150M.

In Sept 2024 Chai released Chai-1, an Apache-2.0 foundation model for molecular structure prediction that matched AlphaFold3 on PoseBusters (77% vs 76%) and folded multimers from single sequences. In Aug 2025 Menlo Ventures led a $70M Series A; Chai-2 followed, claiming a ~20% hit rate for de novo antibody design versus ~0.1% for computational baselines, and a customer's $5M, three-year problem reportedly solved in two weeks. In Dec 2025 General Catalyst and Oak HC/FT led a $130M Series B at a $1.3B valuation, taking total funding past $225M.

Still running and scaling: as of the Dec 2025 Series B, Chai was valued at $1.3B, had ex-Pfizer CSO Mikael Dolsten on its board, and Chai-2 was in use by partner drug-discovery programs.

AlphaFold3 proved general molecular structure prediction was technically possible, so a startup could build on a proven frontier instead of inventing it.

Open weights lowered adoption barriers: labs ran Chai-1 freely, building benchmark credibility and community pull faster than paid sales could.

Drug discovery's screening bottleneck is measured in years and millions of dollars, giving buyers strong willingness to pay for a design tool.

A founding team that had shipped AI for biology at Absci, OpenAI and Facebook AI — plus OpenAI as an investor — gave the seed instant legitimacy.

Open release can be the wedge, not the giveaway: Chai-1 built free benchmark credibility and Chai-2 converted it into a $1.3B round — give away the frontier, charge for the applied.

As of Sept 2026, Chai Discovery is an independent, privately held company; its last public milestone is the Dec 2025 Series B at a $1.3B valuation with over $225M raised. The company continues developing Chai-2-era antibody-design models for partner drug-discovery programs, and Chai-1 remains available under Apache 2.0. No post-Dec-2025 figures (revenue, customer count, next round) have been published, so this entry stops at that milestone.