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AI drug designer Chai Discovery triples valuation to USD 3.8b after USD 400m Series C

Edited by Robert McTiernan··3 min read
AI drug designer Chai Discovery triples valuation to USD 3.8b after USD 400m Series C

San Francisco-based Chai Discovery has closed a USD 400 million Series C financing round for a USD 3.8 billion valuation, meaning a near-tripling of its valuation in under eight months after the AI-driven molecular design specialist signed its first commercial contracts. The round was led by Index Ventures, with participation from Kleiner Perkins, Sequoia Capital, and Dimension, alongside new investors including Bain Capital Ventures, Battery Ventures, Baillie Gifford, BDT & MSD, Sapphire Ventures, and Avra Capital. Existing backers Thrive Capital, OpenAI, Oak HC/FT, Menlo Ventures, General Catalyst, Glade Brook, Avenir, Lachy Groom, and Yosemite also participated.

The company said proceeds will be used to further accelerate its AI model development and expand its platform capabilities, though specific allocation details were not disclosed.

Chai Discovery has raised approximately USD 630 million across four rounds since its founding in 2024. A seed round of approximately USD 30 million, backed by Thrive Capital, OpenAI, and Dimension, was followed by a USD 70 million Series A in August 2025 led by Menlo Ventures. A USD 130 million Series B co-led by Oak HC/FT and General Catalyst followed in December 2025, bringing the company to unicorn status at a USD 1.3 billion valuation. The Series C nearly triples that figure.

The pace of commercial deal-making has tracked the fundraising trajectory. In January 2026, the company announced a research collaboration with Eli Lilly and Co. that included development of a bespoke AI model trained on Lilly's proprietary data. A license agreement with Pfizer, announced in June 2026, granted Pfizer early access to Chai-3, the company's most advanced model, alongside a custom model tailored to Pfizer's workflows. The day before the Series C was announced, Chai disclosed a collaboration with Novartis to advance AI-driven antibody discovery, extending its roster of major pharma partners to three of the industry's largest companies.

Chai's platform is built on the premise that if an AI model can learn the physical and chemical rules governing how molecules interact at atomic resolution, it can generate entirely new drug candidates computationally — without the experimental library screening that has historically defined early-stage drug discovery.

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The platform's foundation model, Chai-1, performs multimodal biomolecular structure prediction across proteins, small molecules, DNA, and RNA simultaneously, including their interactions. Chai-2, released in 2025, added a generative layer: a full-atom diffusion architecture capable of designing complete antibody sequences and structures from scratch, conditioned only on a target protein and a specified binding epitope. The company reported that Chai-2 achieved experimental hit rates of approximately 16–20% in fully de novo antibody design — compared to rates below 1% for prior computational methods — a threshold that makes small-panel experimental validation practical and commercially viable.

Chai-3, the current generation, is reported to reduce the antibody design failure rate by approximately 50% relative to Chai-2 and to improve binding affinity and multi-specific molecule engineering. It is the model now licensed to Pfizer.

The founding team draws its technical lineage from industry rather than academic spinout. CEO Joshua Meier previously led protein language model research at Meta AI Research (FAIR), where he co-developed the ESM model family, and served as Chief AI Officer at Absci, where he co-authored early work on generative antibody design. Co-founder Matthew McPartlon holds a PhD in computer science from the University of Chicago focused on deep learning for protein design, and also worked at Absci as technical lead for de novo antibody design modelling. Co-founder Jacques Boitreaud conducted graduate research in generative molecular modelling at McGill University before working at French AI drug discovery company Aqemia.

This article was generated with AI assistance and reviewed and edited by the AllSci editorial team Explore more at AllSci News: https://allsci.com/news/

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