Chai Discovery raised $400 million in Series C financing, pushing its valuation to $3.8 billion, the company said. The San Francisco AI platform generates de novo molecular designs and is already being used by large pharma partners including Eli Lilly and Pfizer to pursue targets considered hard to drug. The company highlighted progress from its latest model release, Chai-3, claiming material improvements in antibody binding affinity and target success rates versus prior iterations. It also pointed to earlier results from Chai-2, which it said achieved double-digit experimental success rates as a zero-shot de novo antibody design platform. The funding adds to the scale-up narrative for AI-first discovery tools—moving from experimentation into wider partner deployment as investors bet on faster iteration loops for therapeutics with previously lower hit rates.