Heartburn drug could ease painful sun sensitivity
NCT ID NCT05020184
First seen Jun 27, 2026 · Last updated Sep 04, 2026 · Updated 3 times
Summary
This Phase 2 trial tested whether oral cimetidine (Tagamet), a common heartburn drug, can reduce light sensitivity in people with erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP). These genetic conditions cause severe pain from sunlight exposure. The study enrolled 26 participants who took cimetidine or a placebo twice daily for several weeks. Researchers measured changes in protoporphyrin levels, time to pain symptoms in sunlight, and quality of life.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- cimetidine (Tagamet)
- What this could lead to
- If it works, this could point toward a treatment to reduce painful light sensitivity in people with protoporphyria.
- What could go wrong
- This is a small Phase 2 trial with only 26 participants, so results may not apply to everyone. The drug may not lower protoporphyrin levels enough to improve symptoms.
This is an AI summary of the original study and may miss details. Read our disclaimer.
Study facts
What this study's own registry entry says, in plain language.
- Phase
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Phase 2
Tests whether the treatment actually works, and watches for side effects, in a larger group.
- Participants
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26 people
The number who actually took part.
- Started
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Jun 2022
- Finished
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Apr 2025
- Lead sponsor
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Other sponsor
The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
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15 years and older
- Sex
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Anyone
- Healthy volunteers
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Not accepted
This study is not open to healthy volunteers. The entry requirements below say who it is open to.
Show the full entry requirements Hide the full entry requirements
Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
Inclusion Criteria: * Prior enrollment or co-enrollment in the Longitudinal Study of the Porphyrias (PC Study 7201) with a confirmed diagnosis of EPP or XLP * Male or female age ≥15 years at screening * Characteristic history of non-blistering cutaneous photosensitivity * Willing and capable of giving informed consent and following procedures described in the protocol Exclusion Criteria: * Participants not willing to expose themselves to light to the point of prodromal symptoms at least weekly * History of liver or bone marrow transplant or clinically significant liver dysfunction as determined by the Investigator * Known or suspected allergy or intolerance to cimetidine * Use of any other experimental therapy in the past 3 months at screening * Use of cimetidine within the past 3 months at screening * Individuals with elevations of porphyrins in plasma or erythrocytes due to other diseases (i.e., secondary porphyrinemia) such as liver and bone marrow diseases * Patients with any clinically significant comorbid conditions, which in the opinion of the Investigator, precludes participation * Treatment with any drugs or supplements (Appendix 1) that in the opinion of the Investigator can interfere with subject safety or the objectives of the study * The participant either does not have a smartphone or is not willing to use his/her smartphone for the study * Women who are pregnant, breastfeeding, or actively planning to become pregnant * Individuals with moderate to severe renal insufficiency
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
Locations
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Atrium Health Wake Forest Baptist Medical Center
Winston-Salem, North Carolina, 27157, United States
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Massachusetts General Hospital
Boston, Massachusetts, 02114, United States
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University of Texas Medical Branch
Galveston, Texas, 77555, United States
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