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Study on Mepolizumab for Children and Teens with Hypereosinophilic Syndrome

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What is this trial about?

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

This clinical trial is focused on studying a condition known as Hypereosinophilic Syndrome (HES), which is a rare disorder where the body produces too many eosinophils, a type of white blood cell. The study is testing a treatment called mepolizumab, which is given as a solution for injection under the skin. Mepolizumab is designed to help reduce the number of eosinophils in the blood, potentially improving symptoms for those with HES.

The purpose of the study is to evaluate how effective and safe mepolizumab is for children and teenagers aged 6 to 17 years who have HES. Participants in the study will receive mepolizumab injections every four weeks over a period of 52 weeks. The study will monitor the frequency of HES flare-ups, which are episodes when symptoms worsen, and will also look at changes in the use of other medications that participants might be taking for HES.

Throughout the study, researchers will collect information on how participants are feeling, including their levels of fatigue, which is a common symptom of HES. The study will also measure the concentration of mepolizumab in the blood at different times to understand how the body processes the medication. This information will help determine the overall effectiveness and safety of mepolizumab for treating HES in young patients.

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

    Initial Visit and Screening

    The participant, aged 6 to 17 years, attends the initial visit for screening. This visit is referred to as Visit 1.

    During this visit, the participant's medical history is reviewed to confirm a diagnosis of hypereosinophilic syndrome (HES) for at least 6 months.

    A blood test is conducted to ensure the eosinophil count is 1000 cells/μL or higher.

    The participant must have experienced at least two HES flares in the past 12 months.

    The participant must be on a stable dose of HES therapy for the 4 weeks prior to the first dose of mepolizumab.

  2. Step 2

    Consent and Assent

    The participant's legal guardian provides written informed consent, and the participant provides assent if applicable.

    The participant and guardian are informed about the study in understandable terms.

  3. Step 3

    First Dose Administration

    The participant receives the first dose of mepolizumab via subcutaneous injection. This occurs at Visit 2.

    The medication is administered every 4 weeks throughout the study.

  4. Step 4

    Regular Follow-up Visits

    The participant attends regular follow-up visits every 4 weeks for a total of 52 weeks.

    During these visits, the participant's health is monitored, and additional doses of mepolizumab are administered.

    Blood tests are conducted to monitor eosinophil levels and other health indicators.

  5. Step 5

    Monitoring and Assessment

    Throughout the study, the frequency of HES flares is recorded.

    The participant's use of oral corticosteroids (OCS) such as prednisone or prednisolone is monitored, with a focus on reducing the dosage over time.

    Fatigue levels are assessed using a specific questionnaire.

  6. Step 6

    End of Study

    The study concludes after 52 weeks of treatment.

    Final assessments are conducted to evaluate the participant's response to mepolizumab and overall health.

Who can join the trial?

8 criteria

  • The participant must be between 6 and 17 years old at the start of the study.
  • The participant must have been diagnosed with **Hypereosinophilic Syndrome (HES)** for at least 6 months before joining the study. HES is a condition where there are too many eosinophils, a type of white blood cell, in the blood.
  • The participant must have had 2 or more **HES flares** in the past 12 months. A flare is a sudden worsening of symptoms.
  • The participant must have a blood **eosinophil count** of 1000 cells per microliter or more at the start of the study. Eosinophils are a type of white blood cell.
  • The participant must be on a stable dose of HES treatment for 4 weeks before the first dose of the study medication.
  • Both male and female participants can join. Female participants who can have children must use an acceptable method of **contraception** during the study and for 16 weeks after the last dose of the study medication. A pregnancy test is required for females who can have children.
  • Written consent must be obtained from the participant's legal guardian, and the participant must give their agreement to join the study if they are able to understand and sign a form.
  • A legal guardian or primary caregiver must be available to help with study visits, follow-up, and to provide information about the participant during the study.

Who cannot join the trial?

5 criteria

  • Participants who are not between the ages of 6 to 17 years.
  • Participants who do not have a condition called Hypereosinophilic syndrome (HES), which is a disorder where there are too many white blood cells called eosinophils in the blood.
  • Participants who are unable to receive the study medication, which is given as an injection under the skin every 4 weeks.
  • Participants who are not able to follow the study procedures or attend the required visits.
  • Participants who have any other medical condition that might interfere with the study or pose a risk to their health.
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Investigated drugs

Mepolizumab is a medication used in this clinical trial to treat children and teenagers aged 6 to 17 years who have hypereosinophilic syndrome (HES). It is given as an injection under the skin every four weeks. The purpose of using mepolizumab in this study is to see how well it works in reducing the symptoms of HES and to check its safety for young patients.

What is already known about the treatment

Mepolizumab – Mepolizumab is administered as a subcutaneous injection, typically given every four weeks. It is currently being studied in clinical trials for its effectiveness and safety in treating hypereosinophilic syndrome (HES) in children and adolescents aged 6 to 17 years. The medication works by targeting and inhibiting interleukin-5 (IL-5), a protein that plays a key role in the growth and activation of eosinophils, which are a type of white blood cell involved in allergic reactions and inflammation. Mepolizumab is classified as a monoclonal antibody and is used to reduce the number of eosinophils in the blood, thereby alleviating symptoms associated with HES.

Investigated diseases

Hypereosinophilic Syndrome (HES) – Hypereosinophilic syndrome is a rare condition characterized by an abnormally high number of eosinophils, a type of white blood cell, in the blood. This increase in eosinophils can lead to inflammation and damage in various organs and tissues throughout the body. The disease often progresses with episodes of flare-ups, where symptoms may worsen, followed by periods of remission. Common symptoms include fatigue, skin rashes, and respiratory issues, although the specific symptoms can vary depending on which organs are affected. Over time, the persistent high levels of eosinophils can cause significant complications if not managed properly. The condition requires careful monitoring to prevent organ damage and manage symptoms effectively.
Trial detailsLast updated 2 Oct 2026
Age0-17PhasePhase IIITrial ID2023-510110-36-00Protocol code215360Estimated enrolment21 patientsSponsorGlaxosmithkline Research & Development Limited

sourced from the EU Clinical Trials Register and site verification

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On this site, “treatment” means an investigational medicine being studied in a clinical trial. Its safety and efficacy for the use being studied have not yet been confirmed, some participants may receive a placebo or a comparator medicine, and taking part does not guarantee any health benefit. The decision to take part is made by the doctor at the research site. This site is for information only and does not replace medical advice.

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