OpenAI's second-ranking executive, Fidji Simo, is stepping down from her full-time role as CEO of Applications to transition into a part-time advisory position after an extended medical leave for a severe exacerbation of chronic illness. Simo, who was diagnosed with Postural Orthostatic Tachycardia Syndrome (POTS) in 2019, announced that her recovery journey has proven longer and more complex than anticipated, requiring her to focus entirely on her health. This leadership shift leaves a critical gap in the company's product and business operations as OpenAI prepares for its upcoming public offering, with Greg Brockman expected to step up to manage product responsibilities. The move underscores the intense personal challenges faced by top executives in the fast-paced AI industry and marks a significant change in Sam Altman's leadership team.