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Phase 3 Randomized Placebo‑Controlled Study of Efgartigimod Alfa in Adults with Graves’ Disease Inadequately Controlled by Antithyroid Drugs

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What is this trial about?

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

The study examines adults with Graves' Disease whose thyroid condition remains uncontrolled despite use of antithyroid drugs. The investigational medication, identified as efgartigimod PH20 SC PFS, is given by a subcutaneous injection and is compared with a placebo. The purpose of the study is to evaluate the efficacy and safety of this new treatment in helping patients achieve normal thyroid hormone levels without the need for ongoing antithyroid medication.

Participants are randomly assigned to receive either the study drug or placebo on a regular schedule for several months. Throughout the trial, blood tests are performed to measure thyroid hormones (such as T3, T4, and TSH) and antibodies that affect the thyroid (TRAb). Researchers also monitor overall health, side effects, and quality of life using questionnaires. The study follows participants for up to 24 weeks to see how many can maintain normal thyroid function without antithyroid drugs and to assess any safety concerns associated with the treatment.

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

    Baseline assessment

    After you join the study, a series of initial tests will be performed. these include blood tests to measure thyroid hormones (ft3, ft4, tsh) and antibodies, as well as an electrocardiogram and vital‑sign measurements.

    Information about your current antithyroid drug (atd) dose will be recorded, and you will be asked to complete questionnaires about symptoms and quality of life.

  2. Step 2

    Randomization

    Based on the baseline results, you will be assigned by a computer system to receive either efgartigimod or a matching placebo. the assignment is double‑masked, meaning neither you nor the study staff will know which product you receive.

  3. Step 3

    First injection

    You will receive a single subcutaneous injection (under the skin) of the assigned product. the efgartigimod product is a 1000 mg solution in a pre‑filled syringe; the placebo looks identical but contains no active substance.

    The injection will be administered by a trained study professional in a designated clinic area.

  4. Step 4

    Subsequent injection schedule

    Additional injections will be given at regular intervals as defined by the study protocol. each injection will be subcutaneous and will follow the same procedure as the first dose.

    The exact frequency (for example, weekly or bi‑weekly) and total number of doses will be determined by the study design and communicated to you at the start of this phase.

  5. Step 5

    Routine follow‑up visits

    At each visit you will have blood drawn to check thyroid hormone levels, antibody levels, and overall safety labs such as liver function and blood counts.

    You will also be asked about any side effects, and your antithyroid drug (atd) dose may be adjusted according to the study guidelines.

    Electrocardiogram and vital‑sign checks may be repeated periodically.

  6. Step 6

    Week 24 evaluation

    Around week 24, a comprehensive assessment will be performed to determine if you are euthyroid (thyroid hormones within normal range) while off antithyroid drugs.

    The evaluation will also record whether you are taking a low dose of methimazole (mmi ≤5 mg/day) or carbimazole (cbz ≤7.5 mg/day), and whether thyroid‑stimulating hormone receptor antibodies (trabs) are negative.

  7. Step 7

    Extended safety monitoring

    After the week‑24 visit, you will continue to be monitored for up to 18 months to assess long‑term thyroid status and any delayed side effects.

    Periodic blood tests, questionnaires, and safety checks will be performed according to the study schedule.

  8. Step 8

    Study completion

    At the end of the study period, a final visit will collect all remaining data, including final thyroid hormone levels, antibody status, and a summary of any adverse events.

    The results will be used to evaluate the overall efficacy and safety of efgartigimod compared with placebo in participants with graves’ disease.

Who can join the trial?

4 criteria

  • Be at least 18 years old and legally able to give consent for a clinical study.
  • Have a confirmed diagnosis of Graves' Disease with blood test showing anti‑thyrotropin receptor antibody (TRAb) levels that are at or above the upper limit of normal.
  • Show active hyperthyroidism caused by Graves' Disease, meaning the blood level of thyroid‑stimulating hormone (TSH) is less than 0.1 mIU/L.
  • Have taken the medication methimazole (MMI) or carbimazole (CBZ) for at least three months before the screening visit.

Who cannot join the trial?

5 criteria

  • History of an overactive thyroid (hyperthyroidism) that is not caused by Graves' disease, such as a toxic adenoma or a toxic multinodular goiter.
  • Previously received radioactive iodine therapy or have had a complete removal of the thyroid gland (total thyroidectomy).
  • Taken any medication or supplement containing the thyroid hormones T3 or T4 (for example, levothyroxine, liothyronine, dried thyroid preparations, or thyroid‑support supplements) within 6 weeks before screening.
  • Any complication of overactive thyroid or another medical condition that could place you at high risk, including an irregular heart rhythm (arrhythmia) related to Graves' disease, such as fast heart rhythms like atrial fibrillation or atrial flutter that are not well controlled with medication.
  • Having Graves' Orbitopathy or Thyroid Eye Disease that requires systemic therapy (medicines that affect the whole body, such as corticosteroids), eye injections, eye surgery, radiation to the eye area, or planning any of these treatments during the study.
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Investigated drugs

Vyvgart (efgartigimod alfa) is a medication given as a subcutaneous injection using a pre‑filled syringe. It is designed to target a specific part of the immune system that can worsen Graves’ disease, helping to reduce disease activity when standard antithyroid drugs are not enough. In the study, participants receive this injection and are monitored to see how well it improves their thyroid condition and to check for any side effects.

What is already known about the treatment

Vyvgart - Vyvgart is given as a 1000 mg solution for injection in a pre‑filled syringe that is administered subcutaneously (under the skin). It is an FDA‑approved monoclonal antibody (IgG1) that is currently used for chronic immune thrombocytopenia and is being studied for Graves’ disease, so it is a known drug with published clinical data. The medicine works by binding to the neonatal Fc receptor (FcRn) and preventing it from recycling IgG antibodies, which lowers the level of harmful auto‑antibodies that drive the disease. It belongs to the class of FcRn antagonists, a type of immunomodulatory biologic.

Investigated diseases

Graves' disease - Graves' disease is an autoimmune condition in which the immune system stimulates the thyroid gland to produce excess thyroid hormones. This leads to a faster metabolism that can cause weight loss, rapid heartbeat, heat intolerance, and nervousness. Over time, the overactive thyroid may cause the heart to work harder and can affect sleep and energy levels. Some people develop swelling of the eyes, known as Graves' ophthalmopathy, which can make the eyes appear bulged and feel uncomfortable. The disease can also cause the skin on the shins to thicken. Without treatment, the hormonal imbalance and eye changes may become more pronounced.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-523333-26-00Protocol codeARGX-113-25-GRD-3001Estimated enrolment230 patientsSponsorArgenx

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