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Study of emactuzumab compared to placebo in patients with tenosynovial giant cell tumor

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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 Tenosynovial Giant Cell Tumour (TGCT), which is a rare type of growth that affects the tissue lining around joints and tendons. The study will test a medication called emactuzumab, which will be given through intravenous infusion, comparing it with placebo to determine if it can effectively treat this condition.

The purpose of this research is to evaluate how well emactuzumab works in treating TGCT by measuring the rate at which tumors respond to treatment within 6 months of starting therapy. The medication will be given as a solution that is administered directly into a vein. Some participants will receive emactuzumab, while others will receive placebo.

During the study, participants will first take part in a 6-month phase where they will receive either emactuzumab or placebo without knowing which treatment they are getting. The study will track various aspects of participants' health, including their pain levels, joint stiffness, and physical function. Doctors will use magnetic resonance imaging (MRI) to monitor changes in the tumors. The total treatment period may last up to 10 months, and participants will be monitored for any effects of the treatment.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial evaluation and randomization

    You will be randomly assigned to receive either emactuzumab or placebo through intravenous infusion

    Your tumor must be measurable with a longest diameter of at least 20 mm

    Initial assessments will include blood tests to confirm adequate organ and bone marrow function

  2. Step 2

    Treatment phase - first 6 months

    You will receive either emactuzumab or placebo through IV infusion

    Regular assessments will track changes in pain and stiffness using a numerical rating scale

    Your joint mobility will be measured regularly

    Imaging scans will be performed to measure tumor response

    You will complete quality of life questionnaires during visits

  3. Step 3

    6-month evaluation

    Your tumor response will be evaluated using imaging scans

    Your physical function and symptoms will be assessed

    The effectiveness of the treatment will be measured

  4. Step 4

    Open-label phase option

    If your disease progresses after the 6-month period, you may be eligible to receive emactuzumab

    At least 3 months must pass between completing the initial treatment and starting open-label treatment

    Any side effects from the previous treatment must have improved to mild level or less

    This phase is only available for adult patients who completed the initial 6-month phase

  5. Step 5

    Safety monitoring

    Regular monitoring of side effects throughout the study

    Blood tests will be performed to check organ function

    Your ability to work and general health status will be tracked

Who can join the trial?

9 criteria

  • Must provide written informed consent to participate in the study
  • Must have confirmed TGCT (Tenosynovial Giant Cell Tumour) through biopsy, where surgery is not recommended due to: - Risk of joint function limitations - High chance of tumor returning after surgery - Surgery unlikely to improve patient's condition - Other health issues making surgery risky
  • Must have a measurable tumor of at least 20 millimeters in size
  • Must be at least 12 years old and weigh at least 30 kilograms
  • Must have adequate blood test results showing: - Hemoglobin above 10.0 g/dL - Neutrophils (white blood cells) above 1.5 × 109/L - Platelets above 100 × 109/L
  • Must have an average pain score of at least 4 on a pain scale during the week before starting the study
  • Must have an average stiffness score of at least 4 on a stiffness scale during the week before starting the study
  • Women who can become pregnant must: - Have negative pregnancy tests - Use effective birth control during treatment and for 7 months after - Acceptable birth control methods include hormonal contraception, IUD, tubal ligation, or partner's vasectomy
  • Men with partners who can become pregnant must use barrier contraception during treatment and for 5 months after, unless surgically sterile

Who cannot join the trial?

17 criteria

  • Age below 18 years or above 75 years
  • Pregnant or breastfeeding women
  • History of other cancers within the past 5 years (except successfully treated non-melanoma skin cancer or cervical cancer in situ)
  • Presence of active infections requiring systemic treatment
  • Serious heart conditions, including:
    • Uncontrolled high blood pressure
    • Heart attack within the past 6 months
    • Unstable heart rhythm problems
    • Severe liver disease
    • Severe kidney disease requiring dialysis
    • Known allergies to study medication or its components
    • Participation in other clinical trials within the past 30 days
    • Mental conditions that could interfere with following study procedures
    • Use of medications that could interact with the study drug
    • History of organ transplantation
    • Active autoimmune diseases requiring immunosuppression
    • Inability to swallow oral medications
    • Any condition that, in the opinion of the study doctor, would make participation unsafe
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Investigated drugs

  • Emactuzumab

    is a medication being studied for the treatment of Tenosynovial Giant Cell Tumor. It is a targeted therapy that works by blocking specific proteins that contribute to tumor growth. This medication is being tested to see if it can help reduce tumor size and improve symptoms in patients with this rare joint condition.

  • Placebo

    is an inactive substance that contains no medication. It is used as a comparison to determine if emactuzumab is effective in treating the condition. Some patients in the study will receive the placebo instead of the active medication to help researchers understand how well emactuzumab works.

What is already known about the treatment

Emactuzumab - A monoclonal antibody medication administered through intravenous infusion, currently being investigated in Phase III clinical trials for the treatment of Tenosynovial Giant Cell Tumour. This targeted therapy works by blocking a specific protein called CSF1R (Colony Stimulating Factor 1 Receptor) on the surface of tumor cells, which helps to reduce tumor growth and associated symptoms. As an experimental immunotherapy agent, emactuzumab represents a promising treatment option for patients with this rare joint tumor condition, with ongoing research evaluating its safety and effectiveness compared to placebo in clinical settings.

Investigated diseases

Tenosynovial Giant Cell Tumour - A rare, non-cancerous growth that affects the joints, particularly in the knees, hips, ankles, or other large joints. The condition develops in the synovial membrane, which is the protective lining of joints and tendons. The tumor causes the synovial tissue to thicken and overgrow, leading to swelling, stiffness, reduced movement, and pain in the affected joint. This condition can occur in two forms: a localized form that affects a specific area of a joint, and a diffuse form that impacts larger areas of the joint lining. The tumor can gradually limit joint function and mobility over time.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2023-510422-32-00Protocol codeSNX-301-020Estimated enrolment145 patientsSponsorSynox Therapeutics Limited

sourced from the EU Clinical Trials Register and site verification

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