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Safety and Efficacy of Extended‑Release Tacrolimus (VI‑0106) in Adults with Pulmonary Arterial Hypertension and Functional Limitations

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What is this trial about?

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

Pulmonary Arterial Hypertension is a rare condition where the blood vessels that carry blood from the heart to the lungs become narrowed, leading to high pressure in the lungs, shortness of breath, fatigue, and limited ability to exercise. The study evaluates an oral, extended‑release capsule containing VI-0106, a form of the medication tacrolimus, taken at a dose of 2.5 mg each day, compared with a matching placebo. All participants will continue any other medicines they are already using for this condition.

The main goal is to determine whether the study drug can improve how far a person can walk in six minutes (6MWD), reduce the pressure in the lung vessels, and favorably change laboratory indicators of disease risk. Participants will be randomly assigned to receive either the active capsule or the placebo, and neither the participants nor the study staff will know which is given. Over about six months, participants will attend regular visits where simple walking tests, symptom questionnaires, and routine blood checks are performed. After the 24‑week treatment period, the medication may be stopped for a short time to see if any benefits remain, and safety checks will continue for a few additional weeks.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Randomization and baseline assessment

    After joining the study, you are assigned by a computer to receive either the active drug or a matching placebo. the assignment is unknown to you and the study staff.

    Baseline measurements are taken, including a six‑minute walk test, evaluation of who functional class, and routine blood tests to record your health status before starting the study medication.

  2. Step 2

    Start taking study medication

    You begin taking one oral prolonged‑release capsule each day. the capsule contains 2.5 mg of tacrolimus if you are in the active group, or no active ingredient if you are in the placebo group.

    The medication is taken at the same time each day, with or without food, as instructed by the study team.

  3. Step 3

    Regular clinic visits and safety monitoring

    You attend scheduled clinic visits approximately every four weeks. at each visit, blood samples are collected to check for any safety concerns, and the six‑minute walk test is repeated to track changes in exercise capacity.

    The who functional class is reassessed at selected visits to evaluate any improvement in symptoms.

    Any signs of clinical worsening, such as hospitalization for pulmonary arterial hypertension or a significant drop in six‑minute walk distance, are recorded.

  4. Step 4

    Continue daily medication through week 24

    You keep taking the assigned capsule every day for a total of 24 weeks. the study medication is not stopped unless a safety issue arises.

  5. Step 5

    Temporary withdrawal of study medication

    At the end of week 24, you stop taking the study medication for four weeks. during this period you continue to attend clinic visits for safety checks and the six‑minute walk test at week 28.

  6. Step 6

    Final assessment at week 28

    After the four‑week withdrawal, you undergo the final six‑minute walk test, who functional class evaluation, and blood tests. these results are used to determine whether the medication had a lasting effect after it was stopped.

  7. Step 7

    Study completion

    Once the week‑28 assessments are finished, your participation in the trial ends. you may discuss any further care with your regular physician.

Who can join the trial?

8 criteria

  • Be an adult aged between 18 and 75 years.
  • Have a confirmed diagnosis of WHO Group 1 Pulmonary Hypertension (Pulmonary Arterial Hypertension, PAH).
  • Experience symptoms that place you in functional class II, III, or IV (meaning you have mild to severe limitation in daily activities) even though you are taking approved PAH medicines such as PDE5 inhibitors, guanylate cyclase stimulators, endothelin receptor antagonists, prostanoids, or activin signaling inhibitors, and those medicines have been stable for at least 3 months (or 6 months if you are using an activin signaling inhibitor).
  • Have had a recent right heart catheterization (RHC) (a test that measures pressures inside the heart and lungs) that shows:
    • Mean pulmonary arterial pressure ≥ 25 mmHg (the average pressure in the lung artery is high),
    • Pulmonary artery wedge pressure ≤ 15 mmHg or left ventricular end‑diastolic pressure ≤ 15 mmHg (these values help rule out left‑heart problems), and
    • Pulmonary vascular resistance ≥ 480 dynes·sec·cm⁻⁵ (about 6 Wood units, indicating the blood vessels in the lungs are stiff).
    • Be able to walk between more than 75 meters and up to 450 meters during a six‑minute walk test (6MWD). This test must be done twice, at least 4 hours apart but within one week, and the two distances must be within 15 % of each other, using the higher distance as the result.
    • If you are a female who could become pregnant, you must agree to use highly effective birth control methods during the study.

Who cannot join the trial?

17 criteria

  • Total Lung Capacity (the amount of air your lungs can hold) is less than 60% of what is expected for your age and size; even if it is between 60%‑70%, you must not have moderate or severe interstitial lung disease (a type of lung scarring) shown on a CT scan (detailed X‑ray).
  • You have an active infection that needs treatment with antibiotics, antifungal, or antiviral medicines.
  • You are currently taking cyclosporine, a drug that suppresses the immune system.
  • You are known to be allergic or overly sensitive to tacrolimus, another immune‑suppressing medication.
  • You are not up to date with recommended vaccinations, or you have a serious mental‑health, addiction, or other condition that makes it difficult to understand the study, follow its rules, or take the medication as directed.
  • Your lung function test shows FEV1/FVC (the ratio of air you can force out in one second to the total air you can exhale) is less than 70% of normal, or your FEV1 (the amount of air you can force out in one second) is less than 60% of normal.
  • You have evidence of left‑sided heart disease, such as:
    • Significant problems with the aortic or mitral heart valves.
    • A heart‑pumping ability (ejection fraction) below 45%.
    • Pericardial constriction (thickening of the heart’s outer covering).
    • Restrictive cardiomyopathy (a stiff heart muscle).
    • Significant coronary artery disease with reduced blood flow (ischemia).
    • You are unable to safely complete the 6‑minute walk test (a test that measures how far you can walk in six minutes).
    • Your expected remaining lifespan is less than six months.
    • Your kidney function measured by eGFR (estimated glomerular filtration rate) is below 30 mL/min/1.73 m², indicating severe kidney impairment.
    • You have moderate to severe liver problems, shown by a Child‑Pugh score higher than 10.
    • Your blood potassium level is higher than 5.1 mEq/L, which can affect heart rhythm.
    • You have used experimental treatments for pulmonary arterial hypertension within the past three months.
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Investigated drugs

Tacrolimus is an oral medication in a prolonged‑release capsule form. In this study it is being tested as an extended‑release version to see if it can improve how well patients with pulmonary arterial hypertension (PAH) can function and to assess its impact on heart and lung measurements. The drug is taken by mouth and is designed to release the medicine slowly over time, which may help maintain steady levels in the body. It is being evaluated for safety and effectiveness in people who are already on standard PAH treatments but still have limitations in their daily activities.

What is already known about the treatment

Tacrolimus - Tacrolimus is taken orally as a prolonged‑release capsule, which means the pill is swallowed and slowly releases the medicine over several hours. It is an approved immunosuppressant used worldwide to prevent organ rejection and is now being studied for pulmonary arterial hypertension, a rare lung disease. The drug works by binding to a protein called FKBP12, which blocks an enzyme named calcineurin; this stops certain immune cells from becoming active and reduces inflammation that can narrow lung blood vessels. Pharmacologically, it is classified as a calcineurin inhibitor and an immunosuppressive agent.

Investigated diseases

Pulmonary arterial hypertension (PAH) - Pulmonary arterial hypertension is a disorder in which the blood vessels that carry blood from the heart to the lungs become narrowed or blocked, raising pressure in these arteries. The increased pressure forces the right side of the heart to work harder to pump blood through the lungs. Over time this extra workload can cause the right heart muscle to thicken and eventually become less efficient. Patients typically notice growing shortness of breath, especially during activity, and may feel fatigue or light‑headedness. The condition often progresses slowly, with symptoms worsening as the arterial narrowing advances.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-524596-24-00Protocol codePH-201 (TRANSCEND)Estimated enrolment218 patients

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