Chai Discovery, a San Francisco-based start-up applying generative artificial intelligence to drug development, has raised $70 million in Series A financing led by Menlo Ventures through its Anthology Fund, a co-investment vehicle with Anthropic. Existing supporter OpenAI joined the round alongside Thrive Capital, Yuri Milner’s DST Global Partners and several other investors, giving the company an estimated post-money valuation of roughly $550 million, according to the Financial Times. Founded by chief executive Shyamal Joshi, Chai Discovery builds large-scale models that predict and design molecular structures for therapeutics. Its latest system, dubbed Chai-2, reportedly achieves a 100-fold improvement in antibody design compared with previous approaches, cutting laboratory iteration times and costs. The capital will be used to hire researchers, expand computing infrastructure and commercialise the platform with pharmaceutical partners. The fundraising underscores intensifying investor interest in AI-enabled drug discovery, a sector that has attracted several hundred million dollars in fresh capital this year.