OpenAI announced in a blog post on Tuesday that it agreed to acquire the product testing startup Statsig, and bring on its founder and CEO, Vijaye Raji, as the company’s CTO of Applications.

OpenAI is paying $1.1 billion for Statsig in an all-stock deal — one of the largest acquisitions ever for the ChatGPT maker — under the company’s current $300 billion valuation, OpenAI spokesperson Kayla Wood told TechCrunch.

The acquisition marks OpenAI’s latest effort to build out its Applications business, helmed by the former CEO of Instacart, Fidji Simo, who started work at the company a few weeks ago. Raji will report to Simo and will head product engineering for ChatGPT, the company’s AI coding tool Codex, and future applications that OpenAI plans to build. The company says that bringing Statsig’s experimentation platform in-house will accelerate product development across the Applications organization.

As Raji comes on board, OpenAI is making changes to its leadership team.

The company’s chief product officer, Kevin Weil, will become VP of a new group called OpenAI for Science, he announced in a post on LinkedIn. Weil says the goal of his new organization “is to build the next great scientific instrument: an AI-powered platform that accelerates scientific discovery.” Weil says he will work closely with Sebastien Bubeck, an OpenAI researcher and the former VP of AI and Distinguished Scientist at Microsoft.

“I’m able to do this because the product and design leaders at OpenAI are amazing, and now are complemented by Fidji Simo beginning her role as CEO of Applications,” said Weil. “OpenAI’s products have been my life since I joined, and they’re in great hands.”

Meanwhile, OpenAI’s current head of engineering, Srinivas Narayanan, announced in a post on LinkedIn that he would transition to a new role as the company’s CTO of B2B applications. In the role, Narayanan says he will collaborate directly with OpenAI’s COO, Brad Lightcap, who oversees many of the company’s relationships with enterprise customers.

OpenAI says the Statsig acquisition is pending regulatory review. Once completed, the company says that all Statsig employees will become OpenAI employees. However, the product testing startup will “continue operating independently and serving its customer base out of its Seattle office,” the company said in their blog post.