The archive · Bio & Materials · Product decision · 2024–2026
Chai Discovery's open-model bet: $30M seed to a $1.3B AI drug designer
London biotech founded 2024: open AI models that design drug molecules from scratch; $30M seed, then $70M A and $130M B at $1.3B.
Chai Discovery
What the business is
AI biotech building open foundation models (Chai-1, Chai-2) that predict molecular structures and design antibodies from scratch for drug-discovery partners.
Starting capital：$30M seed led by Thrive Capital with OpenAI and Dimension (Sept 2024); then $70M Series A (Aug 2025) and $130M Series B (Dec 2025)
How it started
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.
What happened
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.
How it ended up
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.
Background
Chai Discovery is a London AI-biotech startup, founded in 2024, betting that a single open foundation model can predict and reprogram interactions between biochemical molecules — turning drug discovery from screening millions of candidates into designing them. Its founders, led by Joshua Meier, came from OpenAI, Facebook AI, Absci and Stripe, and its seed round was led by Thrive Capital with OpenAI itself and Dimension, at a $150M valuation.
The startup's first move was Chai-1, released free under Apache 2.0 in Sept 2024: a multimodal structure-prediction model that matched AlphaFold3 on the PoseBusters benchmark (77% vs 76%) and folded protein multimers from single sequences without MSA search. Giving the model away built immediate industry credibility. In Aug 2025 Menlo Ventures led a $70M Series A, and Chai-2 followed with a claimed ~20% hit rate for designing antibodies from scratch, versus ~0.1% for computational baselines.
In Dec 2025 Chai raised a $130M Series B at a $1.3B valuation led by General Catalyst and Oak HC/FT, bringing total funding past $225M. The company is still private and scaling, with Chai-1 open source, Chai-2 in partner use, and former Pfizer CSO Mikael Dolsten on the board. The bet has so far held: buyers in drug discovery face years and millions in screening costs, which is exactly what a design engine is priced against.
What has to be true
- 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.
What can be applied
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.
Aftermath
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.
Sources
- OpenAI-backed biotech firm Chai Discovery raises $130M Series B at $1.3B valuation
- Introducing Chai-1: Decoding the molecular interactions of life
- Menlo Ventures Led $70 Million Series A Fundraiser for Chai Discovery to Transform Molecular Design
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