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Study of Elritercept (TAK‑226) with Ruxolitinib vs Placebo in Patients with Myelofibrosis and Anemia on Ruxolitinib Therapy

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What is this trial about?

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

Myelofibrosis is a rare blood disorder in which scar tissue forms in the bone marrow, making it hard for the body to produce healthy blood cells. Many people with this condition also develop anemia, a shortage of red blood cells that can cause tiredness and shortness of breath. In this study participants continue taking the oral medicine ruxolitinib, which is already approved to help control the disease, while receiving either a subcutaneous (under‑the‑skin) injection of the experimental drug elritercept or a matching placebo that looks the same but contains no active medicine.

The purpose of the study is to determine whether adding elritercept improves anemia in people with Myelofibrosis who are already on ruxolitinib. The trial is double‑blind, meaning neither the participants nor the doctors know which injection is being given, and it lasts about 36 weeks. Participants receive regular clinic visits where blood is drawn to check red blood cell counts, hemoglobin (the protein that carries oxygen), and the need for blood transfusions, and they answer simple questionnaires about fatigue and other symptoms.

Throughout the study, safety checks such as routine blood work and occasional imaging scans (like MRI or CT) are performed to monitor how well the bone marrow is working and to look for any side effects. All information is collected in a confidential manner, and the overall goal is to see if the new injection can reduce the need for transfusions and improve energy levels for people living with this condition.

The research process

The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Enrollment and Randomization

    You have been enrolled in the study and assigned at random to receive either the active drug or a matching placebo. The assignment is kept secret to you and the study staff (double‑blind).

  2. Step 2

    Baseline Assessments

    Before any medication is given, you will undergo blood tests, a review of your transfusion history, and questionnaires that measure fatigue and overall quality of life. These results provide a reference point for later comparisons.

  3. Step 3

    Continuation of Background Therapy

    You will keep taking **ruxolitinib** tablets by mouth at a dose of 50 mg each day. This medication is part of your standard treatment for myelofibrosis and will be continued throughout the 36‑week study period.

  4. Step 4

    Study Drug Administration

    You will receive an injection under the skin (**subcutaneous injection**) of either **elritercept** or a **placebo** that looks identical. The injection dose is 5 mg per kilogram of your body weight and will be given according to the study schedule (for example, once each week) for a total of 36 weeks.

  5. Step 5

    Regular Monitoring Visits

    At scheduled clinic visits—typically every four weeks—you will have blood drawn to check your **hemoglobin** level and other safety labs. The study staff will also record any red blood cell (**RBC**) transfusions you receive and ask you to complete the same fatigue and quality‑of‑life questionnaires used at baseline.

  6. Step 6

    Evaluation of Anemia Response

    During the 36‑week double‑blind period, your need for **RBC** transfusions and changes in **hemoglobin** will be evaluated. Success is defined as periods of transfusion independence lasting at least 12, 16, or 24 weeks, and/or increases in hemoglobin of 1.0 g/dL, 1.5 g/dL, or 2.0 g/dL from baseline.

  7. Step 7

    End of Double‑Blind Treatment

    After 36 weeks you will stop receiving the study injections. A final set of blood tests, symptom questionnaires, and any required imaging will be performed to assess the overall effect of the treatment.

  8. Step 8

    Post‑Treatment Follow‑Up

    Optional follow‑up visits may be arranged to monitor long‑term safety, overall survival, and any late effects of the study medication.

Who can join the trial?

6 criteria

  • You must be at least 18 years old when you sign the consent form for the study.
  • You need to be able to understand why the study is being done, the possible risks, and you must sign the consent form voluntarily.
  • You must have a diagnosis of primary myelofibrosis, post‑essential thrombocythemia myelofibrosis or post‑polycythemia vera myelofibrosis that meets the 2022 WHO criteria and is confirmed by a local pathology report (a lab test that looks at your tissue under a microscope).
  • In the 12 weeks before joining the study you must have needed between 3 and 8 units of red blood cell (RBC) transfusions, meaning you are considered transfusion dependent (you rely on blood transfusions to treat anemia).
  • You must have been taking the medication ruxolitinib (a drug approved for treating myelofibrosis) for at least 12 straight weeks, and your daily dose must have been stable (unchanged) for at least the last 8 weeks before the study starts.
  • Your health status must have an Eastern Cooperative Oncology Group (ECOG) score of 2 or lower, which means you are fully active or able to carry out light work and are not bedridden.

Who cannot join the trial?

18 criteria

  • You have previously received luspatercept, sotatercept, or other drugs that block transforming growth factor‑beta (a type of protein that can affect blood cell production).
  • You are currently taking part in another interventional clinical trial (a study testing a new treatment).
  • You have had a solid organ transplant (such as a kidney or liver) or a bone‑marrow transplant.
  • You are of childbearing potential (able to become pregnant) and do not agree to use at least one highly effective birth‑control method from signing the consent until at least 60 days after the last dose.
  • You are a male who can father children and have a partner who could become pregnant, and you do not agree to use a reliable barrier method (such as a male condom) throughout the treatment and for 60 days after the last dose.
  • You have an active infection that needs intravenous antibiotics within the past 28 days or oral antibiotics within the past 7 days (unless they are preventive medicines for low white‑blood‑cell counts).
  • You are known to be positive for HIV, active hepatitis B (HBV) or active hepatitis C (HCV) infections.
  • Your body mass index (BMI) is 40 kg/m² or higher (a measure of body weight relative to height).
  • You have had another type of cancer (other than myelofibrosis) within the past 2 years, unless it is a very early skin cancer, cervical or breast carcinoma in situ, early prostate cancer (stage T1a/b), or early papillary thyroid cancer (stage I).
  • You received any of the following systemic (body‑wide) treatments within 28 days before randomization: androgens (e.g., danazol), drugs that stimulate red‑blood‑cell production, growth‑factor medicines for white blood cells, high‑dose steroids, hydroxyurea, immunomodulatory drugs (e.g., thalidomide, lenalidomide), interferon, thrombopoietin‑receptor agonists, or any investigational drug (a drug still being studied).
  • You have anemia caused by reasons other than myelofibrosis or the JAK inhibitor medication (examples include iron deficiency, vitamin B12 or folate deficiency, thalassemia, autoimmune hemolytic anemia, infections, or significant bleeding).
  • 1,000,000/µL), blood “blasts” (immature cells) >5% in a blood test or ≥10% in any past bone‑marrow test, liver enzymes (AST or ALT) ≥3 times the normal limit, bilirubin ≥2 times normal (unless you have Gilbert syndrome with mild elevation), kidney function (eGFR) <30 mL/min/1.73 m², ferritin ≤50 µg/L, folate ≤2.0 ng/mL, or vitamin B12 ≤200 pg/mL.
  • You have a positive pregnancy test, are known to be pregnant, or are breastfeeding and do not agree to stop breastfeeding for the treatment period and 60 days after the last dose.
  • If you live in France, you are under court protection, not covered by social security, or otherwise legally protected as an adult under French law.
  • You received a red‑blood‑cell transfusion for any reason other than myelofibrosis within the past 12 weeks.
  • You have serious heart disease, such as New York Heart Association Class III or IV (moderate to severe symptoms), a corrected QT interval >500 ms (a heart‑electrical test), uncontrolled arrhythmia, a heart attack, or unstable chest pain within the past 6 months.
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Investigated drugs

  • Elritercept

    is an experimental medicine being tested in this study. It is given as a liquid injection under the skin. The purpose of giving elritercept is to see if it can improve the low blood‑cell counts (anemia) that many people with myelofibrosis experience, even when they are already taking their regular treatment.

  • Ruxolitinib

    is an approved oral medication that blocks certain signals (JAK pathways) that help control the growth of abnormal bone‑marrow cells in myelofibrosis. In this trial, all participants continue to take ruxolitinib as their standard background therapy while the effect of elritercept is evaluated.

What is already known about the treatment

  • Elritercept

    Elritercept is given as a subcutaneous injection in a liquid solution, meaning it is placed under the skin using a small needle. It is still an experimental drug and is being studied in clinical trials, so it is not yet approved for general medical use. The medicine is being tested to help improve anemia in people with myelofibrosis, a rare blood‑bone marrow disease. It works by blocking a protein called activin‑type IIA receptor, which helps the body make more red blood cells, and it belongs to the class of selective activin receptor antagonists (investigational biologics).

  • Ruxolitinib

    Ruxolitinib is taken by mouth as tablets that come in strengths from 5 mg up to 20 mg. It is an approved, orphan‑designated drug used to treat myelofibrosis and related blood disorders. The drug blocks Janus kinase 1 and 2 (JAK1/2), enzymes that send growth signals to abnormal blood cells, thereby reducing disease activity. It is classified as a JAK inhibitor, a type of targeted oral therapy.

Investigated diseases

Myelofibrosis - Myelofibrosis is a bone‑marrow disorder in which scar tissue gradually replaces normal marrow, reducing the production of blood cells. It often starts with symptoms such as fatigue, weakness, and an enlarged spleen, and the scar tissue can increase over time, leading to worsening anemia and further spleen enlargement. The condition may develop from other blood disorders and can progress to a more severe form with greater marrow failure.
Trial detailsLast updated 11 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2026-525660-17-00Protocol codeTAK-226-3002Estimated enrolment241 patientsSponsorTakeda Development Center Americas Inc.

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