Fidji Simo, one of OpenAI's top executives, is stepping down.
Simo, the company's CEO of applications, wrote on X on Thursday that she has decided to leave her full-time role and become a part-time advisor.
Simo went on medical leave three months ago. She said on Thursday that she would focus on recovery amid her long-running chronic illness, which does not have a cure.
"During that time, it became clear that the road to recovery would be much longer and more complex than I had anticipated—and that I needed to focus on it fully," she added.
Simo was diagnosed with postural tachycardia syndrome, or POTS, in 2019. The disorder can cause fainting, intense bouts of dizziness, and an elevated heart rate.
She joined OpenAI in 2025, decamping from her CEO job at Instacart, which she'd steered through an initial public offering. She'd previously worked at Meta, formerly Facebook, for more than a decade.
Former colleagues of Simo told Business Insider earlier this year that they'd seen her as a laser-focused, empathetic, relentless leader skilled in long-term strategy. Simo said she did a "listening tour" to better understand the company and aimed to keep OpenAI's culture feeling like a research lab rather than a nascent tech giant.
As CEO Sam Altman focused on research and computing, Simo said she would drive work on the company's products and commercialization.
In her post, Simo thanked OpenAI's board, Altman, and company president Greg Brockman for their support, and wrote that her journey with her illness had reinforced her belief in the importance of technology.
Altman wrote on X, "i am really sad about this and very grateful for all fidji has done for openai, and even grateful for her friendship and who she is as a person. we all wish her the best for a speedy recovery. this sucks."
Simo was plain in her own post about the toll the illness has taken.
"It has been a jarring experience to spend my days helping build the future while simultaneously navigating a disabling disease that still has no cure," she wrote.
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