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Phase 2 Study of RADAMTS13 in Adults with Acute Ischemic Stroke

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What is this trial about?

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

The study focuses on people who have suffered an Acute Ischemic Stroke, a condition where blood flow to part of the brain is suddenly blocked, causing brain cells to be damaged. The investigational medication being tested is identified by the code name TAK-755, which is given by an intravenous infusion, meaning it is delivered directly into a vein. Participants are randomly assigned to receive either the study drug or a placebo, and neither the participants nor the study staff know which treatment is given, a design described as double‑blind and randomized. The main goal of the trial is to evaluate the safety and tolerability of the medication while also assessing its potential benefit in improving recovery after stroke.

After a stroke is diagnosed, eligible individuals receive a single infusion of the assigned treatment shortly after the event. They remain in the hospital for a few days for close monitoring of any side effects and for basic health checks. Follow‑up visits are scheduled over the next three months to track recovery, including assessments of neurological function and overall health. The study collects information on any serious bleeding events, other adverse reactions, and measures of disability and functional outcome during this period.

The research process

The trial runs in 9 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Randomization and blinding

    After you join the study, you are randomly assigned to receive either the test medication or a placebo. the study is double‑blind, which means you and the study staff will not know which product you receive.

  2. Step 2

    Baseline assessments

    Before any medication is given, you will undergo a series of baseline checks. these include a physical exam, vital‑sign measurements, blood tests, the national institutes of health stroke scale (nihss) assessment, and brain imaging to document the stroke.

  3. Step 3

    Administration of study medication

    You will receive a single intravenous infusion. if you are assigned to the test group, the infusion contains 500 international units of recombinant adamts13 (the active substance). if you are assigned to the placebo group, the infusion contains a lyophilized product with no active ingredient. the infusion is given once and does not require repeated dosing.

  4. Step 4

    Immediate safety monitoring

    Following the infusion, you will be observed closely for at least 120 hours (5 days). during this period, vital signs, neurological status, and any signs of bleeding, especially symptomatic intracranial hemorrhage, will be checked regularly.

  5. Step 5

    24‑hour follow‑up assessments

    At 24 hours after the infusion, you will have a repeat nihss assessment to measure any change in stroke severity. brain imaging will also be performed to determine whether the blocked artery has reopened (recanalization) and whether the damaged brain tissue has improved (reperfusion).

  6. Step 6

    72‑hour or discharge assessment

    If you remain in the hospital, a final brain‑injury measurement (infarct volume) will be taken at 72 hours or at the time of discharge, whichever occurs first.

  7. Step 7

    Intermediate safety visits (day 30 and day 60)

    You will return for clinic visits around day 30 and day 60. during these visits, blood tests will be repeated, and the presence of antibodies against the study drug will be checked. additional safety information, such as any serious adverse events, will be recorded.

  8. Step 8

    Day‑90 final evaluation

    At day 90, a comprehensive final assessment is performed. this includes the modified rankin scale (mrs) score to evaluate overall disability, a final review of any adverse events, and confirmation of survival status. the study also records whether the mrs score is 0‑1 or 0‑2, indicating good functional outcome.

  9. Step 9

    Study completion

    After the day‑90 visit, your participation in the trial is concluded. all data collected throughout the study will be used to assess the safety and effectiveness of the test medication.

Who can join the trial?

13 criteria

  • You (or your legal representative) must sign a written Informed Consent before any study procedures begin.
  • You must be between 18 and 80 years old at the time you sign the consent form.
  • You must have a doctor’s diagnosis of Acute Ischemic Stroke (a stroke caused by a blocked blood vessel in the brain).
  • Your stroke symptoms must have started within the last 24 hours before enrollment. If you woke up with symptoms, the time you were last known to be well counts as the start time.
  • If you can receive the study drug within 0 to 4.5 hours after your stroke began, you must meet one of these imaging requirements:
    • If the hospital uses perfusion imaging (CT perfusion or MR perfusion), the scan must show a small core of dead tissue (less than 70 cc) and a larger area of still‑alive but at‑risk tissue (at least 10 cc), and an ASPECTS score greater than 6.
    • If the hospital does not use perfusion imaging, the scan must still show an ASPECTS score greater than 6.
    • If you are being considered more than 4.5 hours but less than 24 hours after stroke onset, you must meet imaging criteria that show there is still salvageable brain tissue, such as:
      • A core of dead tissue less than 70 cc and a penumbra of at least 10 cc on perfusion imaging, with an ASPECTS score > 6.
      • Or, if only MRI is used, a visible acute lesion on DWI (diffusion‑weighted imaging) without a bright signal on FLAIR (called a DWI/FLAIR mismatch), plus an ASPECTS score > 6 for large‑vessel blockages or > 7 for medium‑vessel blockages.
      • Your National Institutes of Health Stroke Scale (NIHSS) score must be between 6 and 25, indicating a moderate to severe stroke. (The NIHSS is a test that measures stroke severity.)
      • Before your stroke, you must have had a Modified Rankin Scale score of less than 2, meaning you had no significant disability before the stroke. (The Modified Rankin Scale rates how much a person’s daily activities are limited.)
      • Your signs and symptoms must be consistent with an anterior circulation stroke, which affects the front part of the brain’s blood supply.
      • Brain imaging (CT or MRI) must show a blockage in one of the following arteries: internal carotid artery, M1‑M4 segments, or A1‑A3 segments (these are major brain arteries).
      • If the hospital does not have advanced imaging, they must still be able to see an ASPECTS score > 6 (or > 7 for some smaller vessels) on a regular CT scan, and may need to see good collateral blood flow on a CT angiography scan.

Who cannot join the trial?

38 criteria

  • Weight greater than 130 kg or less than 40 kg.
  • If you need intravenous clot‑busting medicine (such as alteplase, tenecteplase, prourokinase, or reteplase) for this stroke, you cannot join the study.
  • Having a seizure at the time the stroke started.
  • Severe head injury that occurred in the past 90 days.
  • Blood pressure that stays very high (systolic ≥ 185 mm Hg or diastolic ≥ 110 mm Hg) before randomisation.
  • Blood sugar (glucose) lower than 50 mg/dL or higher than 400 mg/dL.
  • Previous brain bleeding (intracranial hemorrhage).
  • History of a brain tumor, except a small, harmless meningioma.
  • Another stroke that happened in the past 90 days.
  • Brain or spinal surgery performed within the past 90 days.
  • Major surgery or serious injury in the past 14 days.
  • Having a serious, advanced, or terminal illness expected to shorten life to less than one year.
  • History of cerebral amyloid angiopathy (a condition that makes brain blood vessels fragile).
  • History of any cancer throughout the body, except for fully removed basal cell or squamous cell skin cancers.
  • Active, uncontrolled bleeding at the time of enrolment.
  • A tendency to bleed easily (bleeding diathesis) or any other condition that raises bleeding risk.
  • Inability to have an MRI (magnetic resonance imaging) or CT (computed tomography) scan.
  • Stroke symptoms that are improving very quickly.
  • Chronic blockage of a brain artery that caused the stroke.
  • Complete blockage of the neck portion of the internal carotid artery (extracranial ICA).
  • Signs of infection that has sent clots to the brain (septic emboli) or evidence of bacterial heart infection (endocarditis).
  • Any other significant health problem that the doctor thinks adds extra risk.
  • Participation in another interventional clinical trial within the previous 90 days.
  • Being pregnant, breastfeeding, or unable to follow required birth‑control or abstinence rules.
  • Imaging (MRI or CT) that is too poor in quality to be read according to the study rules.
  • Evidence of a large brain swelling effect (mass effect) or shift of the brain’s midline structures.
  • Blockage in more than one brain blood‑vessel territory.
  • Evidence of recent or old brain bleeding (intracranial hemorrhage).
  • Extensive early brain injury covering more than one‑third of the area supplied by the middle cerebral artery.
  • Presence of a brain tumor (other than a small meningioma), a brain‑wall bulge (cerebral aneurysm), or an abnormal tangle of vessels (arteriovenous malformation).
  • Platelet count lower than 50,000 per cubic millimetre (very low platelets).
  • Being judged by the investigator as potentially unable or unwilling to follow study procedures.
  • Known life‑threatening allergic reaction to TAK‑755 or any of its ingredients.
  • Having received TAK‑755 before.
  • Use of the medication caplacizumab within the past 30 days.
  • Use of products containing von Willebrand factor within the past 14 days.
  • Baseline conditions that prevent understanding the nature, purpose, and possible effects of the trial, as judged by the investigator.
  • Prior use of clot‑busting drugs (alteplase, tenecteplase, prourokinase, or reteplase) for this stroke event.
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Investigated drugs

ADZYNMA is a medicine that contains a protein called radamts13. It is prepared as a powder that is mixed with a liquid and given by injection into a vein. The protein helps the body break down blood clots, which can improve blood flow in the brain after an acute ischemic stroke. In this trial, ADZYNMA is being tested to see if it is safe, if patients can tolerate it well, and whether it may help patients recover better after a stroke. It is classified as an orphan drug, meaning it is intended for a rare medical condition.

What is already known about the treatment

ADZYNMA - ADZYNMA is given as a powder that is mixed with a solvent to create a solution for intravenous injection. It is an orphan drug that has been approved in several countries for the treatment of congenital thrombotic thrombocytopenic purpura and is being studied for use in acute ischemic stroke. The drug works by replacing the missing ADAMTS13 enzyme, which breaks down large von Willebrand factor strings and helps prevent abnormal blood clots. It is classified as a recombinant enzyme replacement therapy and an antithrombotic agent.

Investigated diseases

Acute Ischemic Stroke - Acute ischemic stroke is a sudden loss of blood flow to a part of the brain caused by a blocked blood vessel. The blockage deprives brain cells of oxygen and nutrients, leading to rapid loss of function in the affected area. Symptoms appear quickly, often within minutes, and may include weakness, difficulty speaking, or loss of vision. As the blockage persists, the area of damaged brain tissue can enlarge, worsening neurological deficits. Early changes may be reversible if blood flow is restored, but ongoing blockage can lead to permanent loss of function in that region.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-522734-31-00Protocol codeTAK-755-2002Estimated enrolment222 patientsSponsorTakeda Development Center Americas Inc.

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