Fidji Simo, OpenAI’s No. 2 executive, is leaving her full-time position, the Wall Street Journal reports.

In a note to staff Thursday, Simo said his current medical leave has proven longer and more difficult than expected, and he will instead transition to a part-time advisory role. Simo joined OpenAI’s board of directors in 2024 and joined OpenAI in May 2025 as CEO of Applications, then a newly created role reporting directly to Sam Altman and which consolidated the company’s business and product operations.

That move was embedded in a broader reporting shift: Chief Operating Officer Brad Lightcap, Chief Financial Officer Sarah Friar and CEO Kevin Weil began reporting to him, while Altman stepped back to focus on research, IT and security.

Simo first revealed his health issues in April, when he announced he would be taking medical leave due to a relapse of a neuroimmune condition; It was in that same memo that it was shared publicly that Lightcap took on a new “special projects” role and that CMO Kate Rouch was leaving the company to focus on cancer recovery. Weil has since also left the company.

Simo came to OpenAI from Instacart, where she had been CEO since 2021 and led the company through its 2023 IPO, and before that spent more than a decade at Meta, including running the Facebook app.

Simo’s decision to permanently step back leaves Altman looking for a successor just as OpenAI eyes a potential initial public offering and races to close the business gap with Anthropic. She had been widely seen as a likely candidate to take on even more responsibilities once OpenAI went public, making this a real void for CEO Sam Altman to fill.

Simo primarily focused on growing OpenAI’s consumer business. But ChatGPT’s growth cooled late last year as it missed internal revenue targets, forcing the company to lean more into coding tools, an area it has been and continues to, for now, lag behind Anthropic.