OpenAI-Backed Chai Discovery Raises $130M at $1.3B Valuation to Scale AI-Driven Antibody Design
OpenAI-backed Chai Discovery, founded in 2024, has raised $130M in a Series B round, valuing the company at $1.3B and bringing total funding to $225M just four months after its $70M raise.
The financing follows the release of Chai-2, the company’s latest antibody design model. Unlike earlier methods limited to antibody fragments (single domains, scFvs) or binding predictions, Chai-2 designs full-length monoclonal antibodies. In internal studies, 86% of designed antibodies demonstrated zero or one flagged problem, meeting common preclinical selection standards. Furthermore, 24 of 28 target antigens yielded at least one clean, drug-like candidate.
Credit: Chai Discovery
Chai-2’s capabilities are supported by atomic-level structural accuracy. Cryo-EM validation of five antibody–antigen complexes showed binding exactly at the intended epitopes, with sub-angstrom agreement between predicted and experimental structures, including in challenging CDR loops.
The model has also delivered results on traditionally hard-to-drug targets. Chai-2 generated antibodies against six GPCRs, producing at least one binder per target while testing as few as 10 to 73 designs, and directly generated agonistic antibodies, including in full mAb format. In peptide–MHC studies, testing 27 to 50 designs yielded highly specific binders to KRAS G12V, with no binding to closely related variants.
Chai frames its long-term objective as producing IND-ready biologics in a single in silico pass, which it characterizes as a shift from stochastic screening toward programmable discovery workflows. That ambition now sits alongside a stated Responsible Deployment policy, under which access to the platform is granted selectively to academic and industry users, with explicit constraints around dual-use and unsafe design applications.
The round was co-led by Oak HC/FT and General Catalyst, with participation from Thrive Capital, OpenAI, Dimension, Menlo Ventures, Lachy Groom, Yosemite, Neo, and SV Angel, with Emerson Collective and Glade Brook as newcomers. The capital will be used to build a computer-aided molecular design suite.
Topic: Biotech Ventures
