A Study of Sotatercept for Patients With Eisenmenger Syndrome or Unrepaired Shunt-Associated Pulmonary Arterial Hypertension Resistant to Vasodilator Therapy

Summary

What is this study about? This study will test whether adding sotatercept to usual medicines for pulmonary arterial hypertension (PAH) can help adults who have PAH due to unrepaired congenital heart defects (atrial or ventricular septal defect, or patent ductus arteriosus), including Eisenmenger syndrome. These conditions often cause long-standing changes in the lung blood vessels and low oxygen levels.

Who can join? About 36 adults (age ≥18 years) in Japan whose PAH has not improved enough with pulmonary vasodilators may join. People with very severe symptoms (WHO class IV) or other serious illnesses will not be enrolled.

What will happen if I join?

Participants will be randomly assigned (like a coin flip, in a 2:1 ratio) to:

Sotatercept + vasodilator-based PAH care, or

vasodilator-based PAH care alone. The study lasts 24 weeks. Those who receive sotatercept will have injections every 3 weeks. All participants will have clinic visits and tests at the start, week 12, and week 24, including a 6-minute walk test (how far you can walk in 6 minutes), blood tests, questionnaires, and other heart-lung assessments used in routine PAH care.

What are the possible benefits? Sotatercept improved exercise capacity and heart-lung measures in other PAH studies, but people with unrepaired heart defects were not included. This study may or may not help you directly, but it may help doctors learn how to use sotatercept safely in this group.

What are the possible risks? Side effects seen with sotatercept include increase in haemoglobin, low platelets, nosebleeds, telangiectasia (small dilated blood vessels), bleeding, and blood clots. People with Eisenmenger syndrome can have both bleeding (for example, haemoptysis) and clotting risks. The study will check complete blood counts (CBC) regularly and adjust or pause dosing using label-based rules. Other risks are those of standard PAH care and blood tests.

Time and location The study is conducted at multiple hospitals in Japan. Study participation lasts about 6 months.

Costs and payments The study drug and study-specific tests will be provided at no cost. Usual medical care not required by the study will follow each hospital's standard billing. There is no required payment to join. Any travel reimbursement or stipends will follow site policy.

Privacy Your information will be kept confidential. Results will be shared in journals and at meetings without using your name.

Who to contact If you are interested or have questions, please contact the study team at the participating hospital.

Conditions

• Eisenmenger Syndrome
• Pulmonary Arterial Hypertension of Congenital Heart Disease

Interventions

DRUG

Sotatercept

Sotatercept will be administered subcutaneously every 3 weeks for 24 weeks (total 8 injections): 0.3 mg/kg lead-in at Visit 1, then 0.7 mg/kg from Visit 2 if safety criteria are met. Dose holds/reductions follow label-concordant rules based on complete blood count (CBC) prior to each dose (e.g., hemoglobin rise \>4.0 g/dL from baseline; or \>2.0 g/dL from the previous dose and above ULN; or \>2.0 g/dL above ULN; and platelet count \<50,000/µL). Participants continue stable background PAH therapy (endothelin, nitric-oxide, prostacyclin pathways) per protocol; initiation or up-titration of PAH drugs during the 24-week treatment period is generally not permitted unless clinically mandated for safety and recorded as a protocol deviation.

DRUG

vasodilator-based PAH therapy

Participants receive no sotatercept. They continue site-standard, stable PAH therapy for 24 weeks (endothelin receptor antagonist, PDE5 inhibitor/riociguat, and/or prostacyclin class as clinically indicated). Changes to background therapy are discouraged during the 24-week period unless required for safety; any changes are captured for analysis. The same visit schedule and assessments (e.g., 6-minute walk test, biomarkers, clinical events) apply as in the sotatercept arm.

Sponsors & Collaborators

• Kazuya Hosokawa

  lead OTHER

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

NONE

Model

PARALLEL

Eligibility

Min Age

18 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2025-10-07

Primary Completion

2027-08-31

Completion

2028-04-30

Countries

• Japan

Study Locations