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Phase 2 Randomized Trial of Oral NS-863 in Patients 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 study focuses on Pulmonary Arterial Hypertension (PAH), a condition in which the arteries that carry blood from the heart to the lungs become narrowed, making it harder for the heart to pump blood through the lungs. The investigational medicine being tested is an oral tablet called NS-863, which is taken by mouth.

The purpose of the trial is to find out whether NS-863 can safely improve how the blood vessels in the lungs work and reduce side effects compared with a placebo. Researchers will look at changes in pulmonary vascular resistance, which is a measure of how much pressure the heart must generate to push blood through the lungs, and will count the number of participants who experience an adverse event, meaning any unwanted medical problem. Additional assessments include how far a person can walk in six minutes (6-minute walk distance), a rating of breathlessness using the Borg dyspnea scale, and classification of symptoms using the World Health Organization Functional Classification. Heart function will be checked with an echocardiogram, electrical activity of the heart will be recorded with electrocardiograms, and blood and urine will be examined through clinical laboratory tests to monitor safety.

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 (double‑blind). The medication is taken once daily for about 24 weeks, with regular visits to the clinic for safety checks and basic health evaluations. Throughout the study, participants continue their usual care while the investigators collect the information needed to assess the drug’s effects.

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

    Randomization and Baseline Assessments

    After joining the study, you will be randomly assigned to receive either NS-863 or a matching placebo. The study is double‑blind, so you will not know which one you receive.

    Baseline measurements will be taken, including blood pressure, heart rate, a 12‑lead electrocardiogram (ECG), laboratory tests, and an assessment of your breathing difficulty caused by pulmonary arterial hypertension (PAH).

  2. Step 2

    Start of Study Medication

    You will begin taking one film‑coated tablet each day. Each tablet contains 232 mg of NS-863 (or an identical tablet without active drug if you are in the placebo group).

    The tablet is taken orally with water, preferably at the same time each day.

  3. Step 3

    Daily Dosing

    You will continue the daily dose for approximately 24 weeks, which is the intended treatment period for the study.

  4. Step 4

    Regular Clinic Visits

    You will attend scheduled visits at the study site, typically every four weeks, to allow study staff to check your health and collect data.

    During each visit, vital signs such as blood pressure and heart rate will be recorded, and you will be asked about any new symptoms or side effects.

  5. Step 5

    Efficacy Assessments

    At selected visits, the following tests will be performed to evaluate the effect of the medication:

    Pulmonary vascular resistance (PVR) will be measured to assess the pressure in the blood vessels of the lungs.

    6‑minute walk distance (6MWD) will be recorded to see how far you can walk in six minutes.

    The Borg dyspnea scale will be used to rate how short of breath you feel during activity.

    Your functional status will be classified using the World Health Organization Functional Classification (WHO FC).

    An echocardiogram will be performed to image the heart and its function.

    You will complete the PAH‑Symptoms and Impact (SYMPACT®) questionnaire to report how PAH affects your daily life.

  6. Step 6

    Safety Monitoring

    In addition to efficacy tests, safety will be monitored through:

    Regular measurement of vital signs.

    Physical examinations by a health professional.

    Repeated 12‑lead ECG recordings.

    Laboratory tests that include blood counts, chemistry panels, urine analysis, and clotting studies.

  7. Step 7

    End of Treatment

    After approximately 24 weeks of daily dosing, you will stop taking the study medication.

    A final set of assessments will be performed to capture the last measurements of efficacy and safety.

  8. Step 8

    Study Completion

    All collected data will be reviewed to determine the overall effect of NS-863 compared with the placebo.

    You will be thanked for your participation, and any remaining questions about the study results will be answered by the study team.

Who can join the trial?

9 criteria

  • Be able to read, understand, and sign a written permission form called informed consent before joining the study.
  • Be an adult (male or female) aged 18 to 75 years (19 to 75 years in South Korea) when the consent form is signed.
  • Have a diagnosis of Group 1 pulmonary arterial hypertension (PAH) confirmed by a test called right‑heart catheterization (RHC), and belong to one of these sub‑types: idiopathic (no known cause), heritable (passed down in families), caused by drugs or toxins, linked to connective‑tissue disease, or linked to a simple congenital heart defect that was repaired at least 6 months ago.
  • Be classified as World Health Organization functional class II, III, or IV, meaning you have mild to severe symptoms while on stable background medication.
  • Have recent RHC results (within the last 35 days) that show:
    • Pulmonary vascular resistance (PVR) greater than 5 Wood units (a measure of how hard the heart has to pump through the lungs).
    • Pulmonary artery wedge pressure (PAWP) or left‑ventricle end‑diastolic pressure (LVEDP) of 15 mm Hg or less (indicates normal pressure on the left side of the heart).
    • Mean pulmonary artery pressure (mPAP) greater than 20 mm Hg (shows elevated pressure in the lungs).
    • Complete a six‑minute walk test with a distance of at least 100 meters but no more than 500 meters, performed twice at least 4 hours apart, and the two results must be within 15 % of each other.
    • Be able to attend all scheduled study visits and follow the instructions given by the study doctor.

Who cannot join the trial?

18 criteria

  • Having a current diagnosis of any special type of pulmonary arterial hypertension that is linked to HIV infection, portal hypertension (high blood pressure in the liver’s veins), schistosomiasis (a parasitic infection), involvement of small veins or capillaries, or Eisenmenger syndrome (a heart condition where blood flows the wrong way) or other large heart‑lung connections.
  • Showing blood in the urine (hematuria) with more than 5 red blood cells per high‑power microscope view, or having protein in the urine (proteinuria) measured as a urine albumin‑creatinine ratio above 150 mg/g or a urine protein‑creatinine ratio above 400 mg/g at the screening visit.
  • Having other health problems that make it hard to do the 6‑minute walk test (a simple test where you walk for six minutes to see how far you can go), such as poor circulation in the limbs, joint or muscle disorders, or severe obesity.
  • Having a life expectancy of less than one year.
  • Being pregnant, breastfeeding, or planning to become pregnant while taking part in the study.
  • Using two medicines that stop platelets from clumping together (dual platelet inhibitor therapy), which can increase bleeding risk.
  • Having a serious medical problem or lab result that could raise the risk of the study, such as a previous brain bleed (intracranial hemorrhage), any bleeding event in the past six months, a very low white‑blood‑cell count (absolute neutrophil count under 1 × 10⁹/L), or a very low platelet count (under 50 × 10⁹/L).
  • Testing positive for HIV infection.
  • Having an active liver infection caused by hepatitis B or hepatitis C viruses.
  • Being judged by the study doctor as unwilling or unable to follow the study rules.
  • Having any other ongoing illness or condition that the doctor believes could put you at risk or affect the study results.
  • Starting a program of lung or heart exercise training (pulmonary or cardiac rehabilitation) within the 12 weeks before the first study visit.
  • Having three or more risk factors for left‑heart problems, such as a body‑mass‑index (BMI) of 30 kg/m² or higher, a history of high blood pressure (essential hypertension), any type of diabetes (diabetes mellitus), or evidence of significant coronary artery disease (heart‑blood‑vessel disease) like a past heart attack, heart procedures, a narrowing of a coronary artery by more than 50 %, a positive stress test, previous heart‑bypass surgery, or ongoing chest pain from the heart.
  • Being diagnosed with pulmonary hypertension that belongs to groups 2, 3, 4, or 5 (different types of high blood pressure in the lungs that are not the main condition being studied).
  • Having moderate or severe obstructive lung disease (where the ratio of two breathing measurements, FEV1/FVC, is less than 0.6) or restrictive lung disease (where total lung capacity is less than 70 % of what is expected or the lung’s ability to transfer gas (DLCO) is under 45 %), unless the doctor thinks this is due to a testing error that can be repeated.
  • Having a significant problem with drug or alcohol misuse within the past six months, as judged by the study doctor.
  • Having a history of urinary stones (urinary calculus).
  • Having had an episode of sudden kidney damage (acute kidney injury) within the 12 weeks before the screening visit.
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Investigated drugs

NS-863 is an experimental oral medication being tested as a film‑coated tablet. In this study, participants with pulmonary arterial hypertension (PAH) take the tablet to see if it can lower the pressure in the lungs’ blood vessels and improve how well the heart works. Researchers are looking at how well the drug works compared with a placebo and also checking for any side effects that may occur.

What is already known about the treatment

NS-863 - NS-863 is taken by mouth as a film‑coated tablet, each dose containing 232 mg of the drug. It is still an experimental medicine being studied in Phase 2 trials and has not yet received regulatory approval. The drug is being tested to treat pulmonary arterial hypertension, a condition where the blood vessels in the lungs become too tight. It works by blocking signals that cause the lung arteries to constrict, helping them relax and lower pressure in the pulmonary circulation, and is classified as an investigational oral vasodilator.

Investigated diseases

Pulmonary arterial hypertension (PAH) - Pulmonary arterial hypertension is a condition where the blood pressure in the arteries that carry blood from the heart to the lungs becomes abnormally high. This pressure increase is caused by narrowing or stiffening of these arteries, which makes it harder for blood to flow through the lungs. Over time, the heart must work harder to pump blood through the high‑pressure vessels, leading to gradual enlargement of the right side of the heart. The disease typically worsens slowly, with symptoms such as shortness of breath and reduced exercise capacity becoming more noticeable as the arterial changes progress.
Trial detailsLast updated 11 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-525114-38-00Protocol codeNS863A-P2-01Estimated enrolment114 patientsSponsorNs Pharma Inc.

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