Fidji Simo is stepping down after taking medical leave because of a worsening chronic illness. Driving the news: Simo said Thursday she is stepping down as OpenAI's head of product and business after a "severe exacerbation" of Postural Orthostatic Tachycardia Syndrome (POTS), a chronic condition she was diagnosed with in 2019. * She went on medical leave in April, and OpenAI President Greg Brockman assumed responsibility for product during her absence. What they're saying: "I am only making this decision now because I failed to make it many times before," Simo wrote on X, adding that she's seeing the opportunity for AI applications in health now more than ever. * CEO Sam Altman posted on X saying that he is "really sad about this and very grateful...we all wish her the best for a speedy recovery. * CEO Sam Altman hired her to scale OpenAI's applications business as the company expanded beyond frontier AI models into consumer and enterprise products.