Thanks to Charlotte Lin
A little over a year after starting her dream job at OpenAI as Sam Altman’s second-in-command, Fidji Simo stepped down as her health condition worsened.
She’d been diagnosed six years earlier with postural orthostatic tachycardia syndrome, or POTS, a frustrating chronic condition in which moving from lying down to standing, or even to sitting up, can cause a racing heart and dizziness.
Now, Simo is working on ways to use AI and lots of biological data to attack chronic health conditions like her own. In March 2025, while still at OpenAI, she launched a startup called ChronicleBio with Rohit Gupta, who had previously overseen biobanks at Stanford and UCSF, and Rishi Reddy, a managing director at Tarsadia Investments.
Their goal: To sort through the thicket of symptoms underlying chronic immune-related diseases like POTS, long COVID and myalgic encephalomyelitis/chronic fatigue syndrome, known as ME/CFS. Taken together, perhaps 250 million people worldwide suffer from this set of chronic conditions, Gupta estimates.
To date, ChronicleBio has collected nearly 200 terabytes of data—roughly four times the amount in OpenAI’s early GPT-3 model—from more than 1,000 patients, with nearly 9,800 tubes of blood that have yielded 40,000 vials of specimens stored in its biobank. From those samples, ChronicleBio measures more than 1 billion data points.
ChronicleBio is one of a flood of companies that are looking to use AI and data to develop new therapies more quickly, including for diseases previously considered “undruggable.” ChronicleBio’s difference is that it is focused squarely on chronic diseases that have long stymied scientific researchers. These conditions receive far less attention and funding than, say, cancer.
Why It Matters
“People with complex, chronic diseases like POTS and ME/CFS often spend years banging their heads against the wall of the existing medical system that doesn’t know what to do about their amorphous, yet debilitating, symptoms,” says Forbes senior editor Amy Feldman. “ChronicleBio hopes that by subtyping patients based on their biology rather than their symptoms, it will allow them to develop therapies that have previously failed or stalled out in clinical trials.”