When Fidji Simo announced that she was leaving her role as one of the most senior members of OpenAI's leadership team after a seven-year battle with her chronic illness, Postural Orthostatic Tachycardia Syndrome, or POTS, the news felt unexpectedly personal. My little cousin has POTS, and it's been devastating to witness. Simo's post said she would be focusing on how to use AI to cure these types of diseases, but I wondered if it was just another tech executive making lofty promises about AI that may never materialize.

POTS is estimated to affect between 1 and 3 million Americans, the majority of them women, yet it remains poorly understood and notoriously difficult to diagnose.

"Do people like my cousin have any reason to have hope that AI can actually make a difference for their health?" I asked Simo when I reached out to her after the announcement. I also told her how much I admired her courage to be so open about her condition. That is not easy for a highly scrutinized public figure. Simo was previously at Meta for a decade, where she oversaw the Facebook app, and then served as CEO of Instacart, which she took public in 2023, before joining OpenAI in 2025.

"Yes," she answered. "I created a company, ChronicleBio, to tackle just that."

We spoke by phone in Simo's first interview since leaving her position as OpenAI's CEO of AGI deployment, where she reported directly to CEO Sam Altman. While her main focus now is recovery and a never-ending schedule of medical appointments, she is also working to grow ChronicleBio and continuing to advise OpenAI. She remains in a Slack channel with the company's leadership team, where she regularly speaks with Altman and Greg Brockman, the OpenAI cofounder and president who took over most of Simo's responsibilities after she left.

Brockman's wife, Anna, has POTS in addition to two other chronic diseases. ChronicleBio's three cofounders — Simo, Rohit Gupta and Rishi Reddy — also either have chronic diseases themselves or have a family member with one. These days, Simo says she is "physically the worst I've ever been." There is no cure for POTS. It can cause dizziness upon standing, fatigue, brain fog, headaches and other symptoms because of an imbalance in the body's autonomic nervous system.

Chronic conditions are "becoming a real epidemic," Simo told me. "We're talking about hundreds of billions in lost productivity, and so there's very big potential in finding drugs for these conditions."

In its first year as a company, ChronicleBio has performed 890 blood draws from 709 patients in Utah, Arizona, Texas and India. It has more than 3,500 tubes of blood in its biobank, the company told me. It has extracted 153 terabytes of data from the blood — three times the 45 terabytes GPT-3.5, a 2022 OpenAI model, was trained on. The company has raised $15 million to date.

The next big thing: home blood draws. On Aug. 11, ChronicleBio will launch a sign-up link for mobile phlebotomy trucks to visit the homes of people with certain chronic diseases. Participants will receive an in-depth report on their condition, free for the first 250 people. In exchange, they will provide their biological data to ChronicleBio.

The goal is to learn more about diseases and improve the success rate of clinical drug trials, something Simo says would be nearly impossible without AI. This matters because roughly 90% of drugs that enter clinical trials never reach the market, and the inability to identify which patient subsets respond to a treatment is a major reason trials fail. AI-driven patient stratification has shown promise in oncology, where genomic profiling of tumors is already used to match patients to targeted therapies, but the approach has been slow to reach multisystem chronic conditions like POTS.

The transcript below has been edited for length and clarity.

In preparation for this interview, you sent me an article that you said captures ChronicleBio's approach. It describes how some patients with long COVID were participating in a clinical trial. The drug was working well for them, but then the trial was canceled for supposedly being ineffective for the group as a whole.

Fidji Simo: Yes, that is really what ChronicleBio is meant to solve. We have seen a lot of clinical trials fail because pharmaceutical companies are not able to identify which subset of patients a drug could work for. So they end up giving the drug to everyone with the same diagnosis. Let's say it's POTS. But there could actually be five sub-diseases within POTS, and the drug would work for one of them, but not the other four. So the clinical trial fails when it could have succeeded if we could have identified these people upfront. It seems really simple, but it has not been done for these conditions.

So what your company is doing is finding patients with similar symptoms, grouping them together, and then testing drugs on those subgroups so the trial is more likely to be successful?

That's exactly right. We have already found five sub-diseases where the biology is really different, despite the symptoms being the same. And now that we understand the biology, we can map that to existing drugs that would solve the problem, and so we're going to start testing these existing drugs on our patient population before the end of the year. Then we would partner with biotech and pharma to develop new drugs, with the goal of having suitable therapeutics for every part of this patient population.

What exactly do you mean by a sub-disease?

The sub-diseases do not even have names right now. That is the problem. The way the medical system names these syndromes is by their symptoms. In the case of POTS, it is called Postural Orthostatic Tachycardia Syndrome. It is basically named after the symptom: tachycardia means your heart rate goes up when you stand. But for one group of patients the disease might be driven by the immune system. For another, it is driven by the mitochondria. The underlying biology is very different, and that is why one drug is not going to work across everyone even if the symptoms are the same.

Backing up for a second, is it an amazing feeling to have gone through such a long medical journey yourself, and now you are in a position of power to actually improve the system?

Yeah, you know, it is obviously a horrible disease, and I certainly wish I could have dodged it. But at the same time, I think it has given me enormous meaning. The gap between the disability from these diseases and the amount of funding and research being done on them is terrible. If you look at a condition like chronic fatigue syndrome, it is considered the most disabling disease of all diseases. Like, when you look at the disease chart, it is completely at the bottom, worse than cancer.

And yet, if you look at the amount of funding for this condition, it is absolutely pathetic for two reasons: One, it primarily affects women, so of course you get less funding. Second, while it completely disables you, it usually does not kill you. And so the combination of these two things has made it so these diseases are really ignored, even though they affect people at the prime of their lives. You usually get affected between 20 and 40 years old, and you are completely disabled. You are taken out of your life entirely, and so it is a crazy amount of suffering.

I have a lot of empathy for people with chronic fatigue and chronic conditions after being pregnant. It kind of feels like that. [Earlier in our conversation, Simo mentioned she was bedridden for five months of her pregnancy, and she developed POTS a few years later.]

Yeah, imagine that 24/7, impossible to move. Some patients are fully bedridden in the dark, sensitive to light, sensitive to sound. It is a really terrible quality of life, and to me, it seems impossible that with the tools we have today, we would continue to conclude that diseases are incurable and that patients should be in a dark room for years. We owe them something better, given the progress that we are seeing in a lot of disciplines.

So what is different now with AI? What does it unlock that would not have been possible before?

The complexity of these diseases made it so that without AI they were incredibly difficult to solve. Like I said, they are multisystem, so you need to be looking at the state of the nervous system, the state of the immune system, and how it correlates with your genetics. All of that is a massive data problem that was very hard to get your hands around without AI. And so finally we have AI, and then on top of that, you have the cost of these analyses going down. Doing a genetic analysis years ago was way more costly than it is now. Analyzing 150 terabytes of data would have been either impossible or would have taken years, and now it takes us minutes.

So that is what gives me a lot of hope. I am physically the worst I've ever been, but at the same time, we are at a moment in time where we have the best tools we have ever had to solve diseases that are considered incurable.

What AI models are you using?

We are using a combo of OpenAI and Anthropic models. We are using anything that is available that can help.

Why do you need to collect blood to get the right data?

The reason I did ChronicleBio is because I really think that we are missing true biological data to make progress toward discovering drugs. Right now, a lot of the models use a lot of EHR data — medical records. But medical records do not tell you enough about biology. They are incredibly noisy. They do not tell you how the human body works. If you look at LLMs, they work so well because the internet existed, right? You already had all of this language. We are missing the internet of biology.

What is the latest initiative you are working on?

Right now we have acquired all of this data from blood by partnering with clinics, but we think it is really important to get that data from anyone who wants to participate. We are now in the process of opening up our tests to anyone in the U.S., with mobile phlebotomy coming to their house. That is going to allow us to have a much larger dataset, but also reach patients that are bedridden, that are in the sickest stages of the disease. And we actually return the data to patients, so that gives them more information about that condition in case that can help direct them toward a particular therapy. So that is basically what we are up to.

That is amazing. When does it start?

It is next week, on Aug. 11. We partnered with mobile phlebotomy companies that collect the blood in a kit. They send that to us. We get it analyzed. It takes a couple weeks because these analyses are very robust. And then we send back a report to the patient about everything we learned, and that data goes into our database. And then over time, if we have more findings about which sub-disease the patient might have or things like that, we continue keeping them posted, and then they can take the test over time, so at multiple points in time, so that we can also see how they evolve. So if they went on a particular drug, did their immune system change? That gives us longitudinal data about the evolution and progression of these diseases.

There are already a variety of mail-in blood tests out there. How is what you are doing different?

That is right. The test we do is very focused on these particular complex chronic conditions. So it is not just the standard blood tests that are common. It is a really advanced research-grade blood test.

How much will it cost?

We are making it free for the first 250 patients because we really want to make sure they are getting value out of the report. After that, it is going to cost $400. We are doing it at cost, meaning that is what it costs us, and we are charging the same for patients. The whole point for us is not to make money. It is to collect data so we can find cures.

This is all so fascinating. I am glad we did this.

Thank you for your interest! We are excited. You know, when I was at OpenAI, I said, "I think if AI accomplishes everything but does not cure disease, that would be a very sad state of affairs." The real promise of AI has always been to cure disease. I think it would be a tragedy if we had all of these amazing tools in our hands, but were not able to turn them into drugs that can save patients' lives on a time frame that matters.

This story was originally featured on Fortune.com