Skip to content
Clinical Trials – home

Rare diseases

Investigational molecules

Locations

Our offerNewsroom

RecruitingRare disease

Long-term study of bitopertin safety and effectiveness in patients with erythropoietic protoporphyria or X-linked protoporphyria

Verified siteInvestigationalNo placebo
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

What is this trial about?

A plain-language summary of the goals, design and what participants do

This study involves two rare blood conditions called Erythropoietic Protoporphyria and X-Linked Protoporphyria. These conditions cause a buildup of a substance in the blood that makes the skin extremely sensitive to sunlight, leading to pain and discomfort when exposed to light. People with these conditions often experience burning pain within minutes of sun exposure, which can severely limit their daily activities and quality of life. The treatment being tested in this study is called Bitopertin, which is also known by its code name DISC-1459. This medication comes as a film-coated tablet that is taken by mouth.

The purpose of this study is to examine the long-term safety and tolerability of bitopertin in people with these light-sensitive conditions. The study will look at how well the medication is tolerated over an extended period and whether it causes any unwanted effects. Additionally, the study will measure how the treatment affects the ability to spend time in daylight without experiencing pain and will track changes in the levels of the substance in the blood that causes the light sensitivity.

This is a long-term study that will follow participants who have already taken part in a previous study of bitopertin. Participants will continue taking the medication for up to 52 weeks, with the maximum daily dose being 60 milligrams. During the study, regular check-ups will be conducted to monitor overall health, including physical examinations and blood tests. The study will also track how much time participants can spend in sunlight without pain and how quickly symptoms appear after sun exposure, as well as measure the concentration of the medication in the blood to understand how the body processes it.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Entry into the long-term study

    This study is designed for individuals who have already participated in a previous bitopertin study and have completed the treatment phase and final visit of that earlier study.

    Upon entering this long-term study, your participation will continue to evaluate the safety and effects of bitopertin over an extended period.

    The study is expected to run until December 2028.

  2. Step 2

    Treatment with bitopertin

    You will receive bitopertin, which is provided as a film-coated tablet that is taken by mouth.

    The specific dosage, frequency, and duration of treatment will be determined based on the study protocol and your individual response to the medication.

    This is an open-label study, meaning both you and your doctor will know that you are receiving bitopertin.

  3. Step 3

    Regular monitoring visits

    Throughout the study, you will attend scheduled visits where your health will be monitored.

    During these visits, your vital signs (such as blood pressure, heart rate, and temperature) will be measured.

    You will undergo physical examinations to assess your overall health.

    Blood samples will be collected to measure laboratory parameters and to check the levels of bitopertin in your blood.

    Your blood will also be tested for metal-free PPIX concentrations, which is a substance that builds up in the blood of individuals with erythropoietic protoporphyria or x-linked protoporphyria.

  4. Step 4

    Recording of time spent in sunlight

    You will be asked to keep track of the total hours you spend in sunlight without experiencing pain.

    You will also record the average time until you first notice early warning signs (called prodromal symptoms) when exposed to sunlight.

    This information helps to assess whether your tolerance to daylight improves during the study.

  5. Step 5

    Reporting of side effects

    Any new symptoms or health changes that occur during the study should be reported to the study staff.

    These are referred to as treatment-emergent adverse events, which are any unwanted medical occurrences that happen after starting the study medication.

    Reporting these events is an important part of evaluating the safety and tolerability of bitopertin.

  6. Step 6

    Continuation of treatment and follow-up

    You will continue taking bitopertin and attending regular monitoring visits throughout the duration of the study.

    The study aims to gather long-term information on the safety, tolerability, and effectiveness of bitopertin in managing erythropoietic protoporphyria or x-linked protoporphyria.

    The study procedures will continue as scheduled until the estimated end date or until your participation is completed.

Who can join the trial?

7 criteria

  • You must have a diagnosis of EPP (a rare condition that makes your skin very sensitive to sunlight) or XLP (a similar condition linked to the X chromosome), and you must be currently participating or have previously participated in an earlier bitopertin study, and you must have completed the treatment phase and final visit of that earlier study.
  • You must be at least 12 years old or older when you agree to join this study.
  • If you are younger than 18 years old, you must weigh at least 32 kilograms. If you are 18 years old or older, your BMI (a measurement that compares your weight to your height) must be at least 18.5.
  • You must be willing to use highly effective birth control methods during the study, while taking the study medicine, and for at least 30 days after your last dose. This applies to males who have female partners who can become pregnant and to females who can become pregnant.
  • If you are a female who can become pregnant, you must have a negative pregnancy test (either urine or blood test) before starting the study.
  • You must be able to understand the goals, procedures, and requirements of the study, and you must be able to provide written informed consent (your agreement to participate). If you are under 18, you may also need to provide assent (your agreement in addition to your parent or guardian's permission).
  • You must be able to follow all the procedures required by the study.

Who cannot join the trial?

3 criteria

  • The study data does not list specific reasons why patients cannot participate in this clinical trial
  • If you are interested in participating, the research team will need to review your individual medical situation to determine if you are eligible
  • General safety considerations will be evaluated by the medical team conducting the study
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.

We usually reply within a few days

Verified sites

All sites with verified contact details – recruitment status may not be available; ask directly

Trial locations

Where you can join this trial

Countries are shaded by recruitment status. Click a recruiting country to ask about joining there.

RecruitingNot recruiting
Not finding your country?

Not sure what to do next?

Joining a clinical trial can seem overwhelming. We guide you step by step, so you know exactly what to expect and how we support you through the process.

See the full process and FAQ

Investigated drugs

Bitopertin (also known as DISC-1459) is an investigational medication being studied for the long-term treatment of erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP). These are rare genetic conditions that cause the skin to become extremely sensitive to sunlight. This medication is being tested to see if it is safe and well-tolerated when taken over an extended period of time, and whether it can help improve the symptoms of these conditions.

What is already known about the treatment

Bitopertin – Bitopertin is an experimental medication being studied in tablet or capsule form taken by mouth for the treatment of Erythropoietic Protoporphyria (EPP) and X-Linked Protoporphyria (XLP), which are rare genetic disorders that cause severe skin sensitivity to sunlight. The drug works by blocking a specific protein called GlyT1, which helps reduce the production of protoporphyrin, the substance that builds up in the blood and causes painful skin reactions when exposed to light. Bitopertin is currently under investigation in clinical trials and is not yet approved for regular medical use, but early studies are evaluating whether it can safely help patients tolerate more sun exposure and improve their quality of life.

Investigated diseases

  • Erythropoietic Protoporphyria

    Erythropoietic Protoporphyria is a rare inherited disorder that affects the production of heme, an essential component of hemoglobin in red blood cells. The condition results from a deficiency of an enzyme called ferrochelatase, which leads to the buildup of a substance called protoporphyrin in the blood, skin, and other tissues. When exposed to sunlight, people with this disease experience painful burning sensations in their skin, often within minutes of sun exposure. The skin may become red, swollen, and develop a waxy appearance after repeated sun exposure. The accumulation of protoporphyrin can also affect the liver over time. This condition typically begins in childhood and continues throughout life.

  • X-Linked Protoporphyria

    X-Linked Protoporphyria is a rare inherited metabolic disorder similar to Erythropoietic Protoporphyria but caused by a different genetic mutation. The condition results from increased activity of an enzyme called ALAS2, which leads to excessive production and accumulation of protoporphyrin in red blood cells and tissues. Like Erythropoietic Protoporphyria, affected individuals experience painful skin reactions when exposed to sunlight, including burning, itching, and swelling. The symptoms typically appear in early childhood and persist throughout life. The excess protoporphyrin in the body can also accumulate in the liver. Because the genetic mutation is located on the X chromosome, the inheritance pattern differs from Erythropoietic Protoporphyria.

Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-523275-27-00Protocol codeDISC-1459-501Estimated enrolment265 patientsSponsorDisc Medicine Inc.

sourced from the EU Clinical Trials Register and site verification

Want to learn more about this trial or check if you can participate?

Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.