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A Study of Depemokimab and Prednisolone in Adults with Hypereosinophilic Syndrome (HES)

Verified siteRegistered drugNo placebo
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What is this trial about?

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

This study focuses on people with Hypereosinophilic Syndrome (HES), a rare blood condition where there are too many white blood cells called eosinophils in the blood and tissues. These elevated levels can cause damage to various organs in the body. The study will test a new medication called depemokimab, which is given as an injection under the skin, along with standard treatments that may include prednisolone tablets.

The purpose of this research is to determine if depemokimab is effective in controlling HES when compared to placebo in people who are already receiving standard care. The study will last for 52 weeks, during which participants will receive either depemokimab injections or placebo injections. Some participants will also receive prednisolone tablets or matching placebo tablets as part of their treatment.

Throughout the study, doctors will monitor how often participants experience HES flares, which are periods when symptoms get worse or blood eosinophil counts increase. The medication will be provided in a pre-filled syringe for injection under the skin. Participants will be regularly checked for any changes in their condition and any effects of the treatment.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial treatment phase

    You will receive either depemokimab (study medication) or a placebo (substance with no active medication) through subcutaneous injection (under the skin).

    You will continue your standard care medications during the study.

    The treatment phase lasts for 52 weeks (one year).

  2. Step 2

    Monitoring period

    Your health condition will be monitored throughout the 52-week period.

    The medical team will track any episodes of HES flares (worsening of your condition).

    You will complete the Brief Fatigue Inventory questionnaire to assess your fatigue levels.

  3. Step 3

    Regular assessments

    Your blood will be tested to measure eosinophil levels (type of white blood cells).

    The medical team will evaluate any symptoms or changes in your condition.

    Your fatigue levels will be measured regularly using a specific questionnaire.

  4. Step 4

    Study completion

    The study ends after 52 weeks of treatment.

    Final assessments will be conducted to evaluate your response to the treatment.

    Your eosinophil levels and overall health condition will be evaluated one last time.

Who can join the trial?

10 criteria

  • Must be at least 18 years old when signing the consent form
  • Must weigh at least 40 kilograms (88 pounds) at screening
  • Must have a confirmed diagnosis of Hypereosinophilic Syndrome (HES) with:
    • Blood tests showing more than 1,500 eosinophils (a type of white blood cell) per microliter at least twice, with tests done at least 1 month apart
    • Signs of organ problems related to high eosinophil levels
    • Must have experienced at least 2 HES flares in the past 12 months, where:
      • A flare means worsening of symptoms or increased eosinophil counts requiring stronger treatment
      • At least one flare must not be related to reducing medication in the previous 4 weeks
      • Can be male or female, but females must either be:
        • Unable to bear children, or
        • Using highly effective birth control (99% or better) from 14 days before starting the study until 30 weeks after the last dose
        • Must not be pregnant or breastfeeding
        • Must be able to understand and sign the informed consent form

Who cannot join the trial?

14 criteria

  • Current diagnosis of parasitic infection (an infection caused by parasites)
  • History of cancer within the past 5 years (except for successfully treated non-melanoma skin cancer or cervical cancer in situ)
  • Current active infection requiring treatment with antibiotics, antivirals, or antifungals
  • History of severe allergic reactions to biological medications
  • Pregnant women or women planning to become pregnant during the study period
  • Breastfeeding women
  • Participation in another clinical trial within the past 30 days
  • Significant heart conditions including heart failure or recent heart attack
  • Severe liver disease or abnormal liver function tests
  • Severe kidney disease or significantly reduced kidney function
  • History of substance abuse within the past year
  • Mental health conditions that could interfere with study participation
  • Unable to follow study procedures or attend scheduled visits
  • Use of prohibited medications that might interfere with the study drug
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Investigated drugs

Depemokimab is an investigational medication given by injection under the skin (subcutaneous injection). It is being studied for treating people with Hypereosinophilic Syndrome (HES), a rare blood disorder where the body produces too many eosinophils (a type of white blood cell). This medication aims to help control the condition in patients who are not responding well enough to standard treatments. Standard of Care (SoC) refers to the current best available treatments that patients typically receive for managing their Hypereosinophilic Syndrome. These treatments will continue to be used alongside the study medication.

What is already known about the treatment

Depemokimab - A novel injectable medication administered through subcutaneous (under the skin) injections that is currently being investigated in clinical trials for the treatment of Hypereosinophilic Syndrome (HES). This biological agent belongs to the class of targeted immunotherapy medications and works by modulating specific components of the immune system to reduce elevated levels of eosinophils, a type of white blood cell that causes inflammation in HES. The medication is being studied as an add-on therapy to standard of care treatment for patients whose HES symptoms are not adequately controlled with conventional treatments.

Investigated diseases

Hypereosinophilic Syndrome (HES) - A rare blood disorder characterized by a persistent increase in eosinophils (a type of white blood cell) in the blood and tissues. The elevated levels of eosinophils can cause inflammation and damage to multiple organs, including the heart, skin, lungs, and nervous system. The condition typically develops gradually and can affect people of any age. Symptoms may include fatigue, fever, cough, muscle pain, rashes, and breathing difficulties. The severity and progression of symptoms can vary significantly among individuals.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2023-510346-25-00Protocol code217013Estimated enrolment120 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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