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A Phase 3 Study of Once‑Daily Treprostinil Palmitil Inhalation Powder for Adults with Pulmonary Arterial Hypertension

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What is this trial about?

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

The trial investigates a rare lung blood‑vessel disease called Pulmonary Arterial Hypertension. This condition causes high pressure in the arteries that supply the lungs, leading to shortness of breath and reduced ability to exercise. The study evaluates the safety and effectiveness of a once‑daily inhaled medication, Treprostinil Palmitil Inhalation Powder, compared with a matching placebo. The main purpose is to determine whether the medication improves participants’ ability to exercise.

Participants who meet the disease criteria will be randomly assigned to receive either the active powder or the placebo for about six months. The medication is taken by inhalation once each day. Throughout the study, participants will attend regular clinic visits where simple tests are performed, such as a walking test that measures how far a person can walk in six minutes (six‑minute walk distance), a blood test that checks a heart‑stress marker (NT-proBNP), and a questionnaire that rates symptoms and daily activities. Their overall health status will also be recorded using a standard classification system for breathlessness (WHO functional class). The study design ensures that neither the participants nor the investigators know which treatment is being given, and the data are collected to assess both benefits and any side effects.

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

    Enrollment and randomization

    After you agree to join the study, you are assigned by a computer to receive either treprostinil palmitil inhalation powder or a matching placebo inhalation capsule.

    The assignment is double‑blind, meaning neither you nor the study staff know which product you receive.

  2. Step 2

    Baseline assessments

    Before the first dose, you complete a 6 minute walk test, which measures how far you can walk in six minutes.

    A blood sample is taken to measure nt-probnp, a marker that reflects heart strain.

    You answer questionnaires that evaluate the physical impact and cardiopulmonary symptoms of pulmonary arterial hypertension.

  3. Step 3

    Start of daily inhalation

    You inhale one capsule each morning, which contains 1280 µg of treprostinil palmitil if you are in the active group, or an identical‑appearing capsule without active drug if you are in the placebo group.

    The inhalation is performed once daily and continues for the duration of the study, which is up to 24 weeks.

    The inhaled powder is taken using a device provided by the study and does not require any additional medication.

  4. Step 4

    Regular clinic visits

    You attend scheduled visits at approximately weeks 2, 4, 12, and 24.

    At each visit, safety checks are performed, which may include blood pressure measurement, review of any side effects, and a repeat 6 minute walk test at some visits.

    The study staff may also collect additional blood samples and questionnaire responses.

  5. Step 5

    Week 22 assessment

    Around week 22, you perform a 6 minute walk test about 24 hours after your last dose to evaluate longer‑term exercise capacity.

    The result is compared with your baseline measurement.

  6. Step 6

    Week 24 final assessment

    At week 24, you complete a 6 minute walk test 1 to 3 hours after taking your morning dose; this is the primary measurement of the study.

    Blood is drawn again to measure nt-probnp levels.

    You answer the final questionnaires that assess changes in who functional class, physical impacts, and cardiopulmonary symptoms using the pa h-sympact instrument.

    The study team reviews any clinical worsening events, such as hospitalization, need for additional therapy, or significant decline in walking distance.

  7. Step 7

    Study completion

    After the final visit, you stop taking the study medication.

    A final safety evaluation is performed, and you receive information about the overall study results.

Who can join the trial?

11 criteria

  • Be between 18 and 75 years old at the time you sign the consent form.
  • Be able to give a signed informed consent and agree to follow the study rules.
  • Be able to understand the study instructions and, in the doctor’s opinion, likely to finish the study as planned.
  • Have a diagnosis of pulmonary arterial hypertension (PAH) that fits the WHO Group 1 categories (such as idiopathic, heritable, drug‑induced, related to connective‑tissue disease, or after repair of a simple heart defect) according to accepted guidelines.
  • Have had the PAH diagnosis for at least 3 months before screening.
  • Have a functional status of class II‑IV on the NYHA/WHO scale (meaning symptoms range from mild with ordinary activity to severe even at rest).
  • Be taking stable PAH medication (1 to 3 drugs) for at least 90 days (or 6 months for sotatercept) with no dose changes in the last 30 days (or 3 months for sotatercept). These medicines may include endothelin receptor antagonists, phosphodiesterase‑5 inhibitors, guanylate cyclase stimulators, or activin signaling inhibitors.
  • Have not changed the dose of long‑term diuretic medicines for at least 30 days before screening (single or rescue doses are allowed).
  • Be able to walk between 150 and 450 meters on a six‑minute walk test (done twice, at least 4 hours apart, with results within 15 % of each other).
  • Have a recent right‑heart catheterization (or one done within the past 6 months) that shows the required pressure measurements: mean pulmonary artery pressure > 20 mmHg, pulmonary capillary wedge pressure or left‑ventricular end‑diastolic pressure ≤ 15 mmHg, and pulmonary vascular resistance ≥ 5 Wood units.
  • If you are a man or a woman who could become pregnant, you must use an approved method of birth control (contraceptives) according to local regulations.

Who cannot join the trial?

7 criteria

  • If you have pulmonary hypertension that belongs to WHO Groups 2, 3, 4, or 5, or a type of Group 1 that is linked to HIV, complex congenital heart disease, portal hypertension, pulmonary veno‑occlusive disease, or schistosomiasis, you cannot take part.
  • If you have serious problems with the left side of your heart—such as significant valve disease, weak left‑ventricular pumping with a left ventricular ejection fraction (LVEF) below 45%, abnormal echo findings suggesting post‑capillary pulmonary hypertension, a large left atrium (LAVI > 34 mL/m²), types of heart failure called HFpEF or HFmrEF, recent unstable heart‑attack‑related disease, or uncontrolled irregular heartbeat (uncontrolled atrial fibrillation)—you are excluded.
  • If lung function tests show airway blockage, meaning the ratio of forced expiratory volume in 1 second (FEV1) to forced vital capacity (FVC) is less than 0.7, you cannot join.
  • If lung function tests show a restrictive pattern, meaning your forced vital capacity (FVC) is less than 70 % of the value predicted for your age and size, you are not eligible.
  • If you have had a sudden worsening of right‑side heart failure (acute decompensated right heart failure) within the 30 days before screening or during the screening visit, you cannot participate.
  • If an electrocardiogram (ECG) shows a QTc interval longer than 500 milliseconds or you have a known history of long QT syndrome, you are excluded.
  • If you have chronic blood‑clot disease in the lungs (chronic thromboembolic disease) or a recent (within the past 6 months) acute pulmonary embolism, you cannot be enrolled.
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Investigated drugs

Treprostinil Palmitil Inhalation Powder is a medication that patients inhale as a powder once each day. It contains a form of treprostinil that is designed to be released slowly in the lungs. The drug works by relaxing and widening the small blood vessels in the lungs, which helps lower the high pressure that can build up in these vessels in pulmonary arterial hypertension. By improving blood flow in the lungs, the medication aims to make it easier for patients to exercise and carry out daily activities. This inhaled therapy is being tested in the study to see how well it improves exercise capacity and how safe it is for people with this condition.

What is already known about the treatment

Treprostinil Palmitil - It is taken as a dry‑powder inhalation that patients use once a day with a special inhaler, allowing the medication to reach the lungs directly; the powder contains a prodrug that is changed in the lungs to the active drug treprostinil. The product is still investigational and has not yet received full market approval, but it is being studied in several clinical trials for pulmonary arterial hypertension. Its main use is to treat pulmonary arterial hypertension, a rare disease that causes high blood pressure in the arteries of the lungs. Treprostinil Palmitil is classified as a prostacyclin analog and works by activating receptors that relax blood‑vessel muscles, helping to lower pressure and improve blood flow.

Investigated diseases

Pulmonary Arterial Hypertension - A chronic condition where the small arteries that carry blood from the heart to the lungs become narrowed, thickened, or stiff. This increases pressure in these vessels and makes it harder for blood to flow through the lungs. Over time the right side of the heart works harder to pump blood against the higher pressure, which can cause the heart muscle to enlarge. Symptoms such as shortness of breath, fatigue, and reduced exercise capacity may gradually worsen as the disease progresses.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2026-525265-48-00Protocol codeINS1009-301Estimated enrolment190 patientsSponsorInsmed Inc.

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