Emily Pearson grew up fearing the sun. A rare skin disorder left her hands, feet and face in “insufferable pain” whenever she stepped outdoors. Now, after a clinical trial, she can run marathons in daylight instead of darkness.
It was at the Mayo Clinic in Rochester, Minnesota, that a doctor made the diagnosis while Pearson was 17, identifying erythropoietic protoporphyria, or EPP — a condition that makes people allergic to light. The prescribed course of action involved avoiding exposure: sunblock, protective clothing, staying indoors.
Pearson, who now lives in Minneapolis, described the agony in stark terms. “It was just insufferable pain. I would never wish that pain upon anyone, because it’s so horrible.”
Running Through the Dark
Pearson found a way out through running. She had spent 12 years competing as a swimmer before trading her stroke for half-marathons after graduating from high school. To keep her symptoms at bay, she either dressed warmly or took off early, running at sunrise or sunset.
Trips to her family’s cabin in Minnesota turned into tests of how long she could hold up. A single mistake set off a chain reaction that left her suffering for days afterward.
Going outside for simple tasks carried a constant mental weight. “Going to the grocery store, going to get gas, going for any kind of car ride or working outside, you constantly have to think about what you’re doing and how it’s going to affect your health, and dealing with those consequences after,” Pearson, now 25, said. “It was really hard, and it was really, really stressful. It was a big mental load, and it was never-ending.”
The Trial That Changed Everything
In 2025, Pearson volunteered at Sun Escape, a weekend camp for kids with EPP and similar conditions. There she learned about a clinical trial for a drug called bitopertin. She was intrigued but cautious.
“I was very wary of it, like, ‘Does it really work? I know it works for other people, but will it work for me?'” Pearson remembered. “There was that anxiety of the unknown.”
Bitopertin is designed to target protoporphyrin IX, a substance found naturally in the skin that becomes active after exposure to sunlight. People with EPP carry mutations that cause their bodies to produce excessive amounts of it, which leads to painful reactions. The medicine works by reducing those levels, and it is taken as a single daily tablet.
Pearson took part in the trial’s second phase. In the United States, clinical testing runs through four stages. The opening stage checks safety and settles on dosage in a small group. The second stage follows up to several hundred people over months or years, tracking how well the treatment works and any side effects. The third and fourth stages broaden to larger groups for longer periods. Only after that does the FDA look at the data and decide if the medication gets approval.
She began taking bitopertin regularly in July 2025, and kept regular checkups with doctors in Boston to watch how she was doing. Her body changed fast: within weeks, she started doing “really, really well,” and her skin grew more tolerant of sunlight.
A porphyria specialist at the University of Washington named Dr. Sioban Keel has reported hearing similar accounts from other patients. She noted that her experience echoes what she has heard from others taking part in the trial. “The impact I’ve seen it have on my patients has been a game changer. Patients that previously could never go out in the sun are able to go out in the sun … You’re like, ‘I can’t believe I’m hearing this.'”
From Marathon to Cabin
Data from a clinical trial published by Disc Medicine in April showed that the drug “significantly reduced protoporphyrin-IX levels” produced “improved measures of sunlight tolerance” for people with EPP, with “no notable safety concerns.”.
Disc Medicine’s Phase 3 trial for bitopertin has enrolled 183 patients, and results are expected in the last quarter of 2026. A written statement from the company says the FDA has chosen not to move forward with an accelerated review of bitopertin, saying it wants additional evidence of how the drug affects patients. Disc Medicine says it expects the Phase 3 data to deliver what the FDA has asked for.
The drug remains part of Pearson’s regimen through an open-label extension, a stage where those enrolled can elect to continue taking it. During that time, her sun tolerance kept rising.
In October 2025, she ran her first marathon. “I was outside the whole day, running and having fun,” Pearson said. “I just got to wear shorts and a T-shirt. And everyone running around you doesn’t know what you’re going through, but I was really proud of myself.”
The race encouraged her to push further. She trained for another marathon this spring and ran it in June. In July, she spent a week at her family’s cabin. Unlike past years, she spent the whole trip “outside every day, sunup to sundown, no reactions.”
She said that though she still gets minor reactions after spending lots of time outside, the pain has grown far less.
What the Story Shows
Pearson’s experience is a reminder that rare conditions often lack obvious answers. For years, her parents tried to find the cause of her reactions. Sunblock didn’t help. The mystery hung over her childhood.
The order was clear: first the diagnosis, then the trial. Pearson had an answer before she found a solution.
Keel’s reaction captures the shift: “I can’t believe I’m hearing this.” The fact that the statement registers disbelief at all shows just how far removed from normal these outcomes have been.
Daylight no longer bothers Pearson as it once did. She has completed two marathons under the sun and has spent a whole week at her cabin without any reaction.
Her life has literally changed so much.
Key Facts
- EPP diagnosis at age 17
- First marathon run in October 2025
- Bitopertin in Phase 3 with 183 patients
- Data expected Q4 2026
- FDA declined expedited review
Comparison Table
| Stage | Participants | Duration |
|---|---|---|
| Phase 1 | Small group | Tests safety, sets dosage |
| Phase 2 | Up to several hundred | Months or years |
| Phase 3 | 183 patients | Larger population, longer |
| Phase 4 | Larger population | Longer |
The sun no longer troubles Pearson the way it once did. She has completed two marathons in daylight and spent a week at her cabin without reactions. What was once a constant companion, the pain that marked her childhood, has faded into memory rather than a daily weight she carries.
Her life has literally changed so much.
See the video the story is built around at CBS News.
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