Chai-2

Chai-2 is Chai Discovery's generative AI system for designing new antibodies, nanobodies, and small protein binders against a chosen protein target. Introduced June 30, 2025, it combines molecular structure prediction with sequence and structure generation, and the launch study reported binders for roughly half of 52 tested targets after assaying at most 20 designs per target, a double-digit hit rate the company describes as a hundred-fold improvement over prior computational approaches.

Chai-2 is a closed platform accessed through partnerships rather than public weights, and it has signed collaborations with Eli Lilly, Pfizer, Novartis, argenx, and GSK, with a Chai-3 successor announced for pharma partners. The honest picture: the hit-rate figures come from company preprints rather than peer-reviewed independent replication, and a binding hit is still far from a medicine, but the wet-lab validation bar it cleared is what separates it from pure benchmark claims.