Chai Discovery, an AI-driven biotechnology startup backed by OpenAI, said on Monday it has raised $130 million in a Series B funding round, valuing the company at $1.3 billion.

The round was led by General Catalyst and Oak HC/FT, Chai said in a statement. Existing investors Menlo Ventures, OpenAI, Dimension, Thrive Capital, Neo, Yosemite Venture Fund, Lachy Groom and SV Angel also participated, alongside new investors Glade Brook and Emerson Collective. The latest financing brings the company’s total funding to more than $225 million.

Founded to apply artificial intelligence to drug development, Chai is part of a fast-growing group of startups betting that AI can significantly shorten the time and cost required to discover new medicines. Menlo Ventures led Chai’s $70 million Series A round in August, describing the company as developing foundation models tailored for drug discovery, with a focus on predicting interactions between biochemical molecules to enable new therapeutic designs.

Chai aims to build what it calls a “computer-aided design suite” for molecules. The company launched its first AI model, Chai 1, last year and has since introduced Chai 2, its latest system. Chai said the new model has delivered markedly higher success rates than existing approaches in de novo antibody design, which involves creating custom antibodies from scratch rather than modifying existing ones.