Could a heart pill help fontan teens breathe easier during exercise?

NCT ID NCT05918211

Disease control Sponsor: Mezzion Pharma Co. Ltd Source: ClinicalTrials.gov ↗

First seen Jun 27, 2026 · Last updated Jun 27, 2026

Summary

This study tests whether the drug udenafil can improve exercise ability in adolescents aged 12-18 who have had the Fontan procedure for single ventricle heart disease. Participants will take udenafil or a placebo daily for 26 weeks, and their exercise capacity will be measured. The trial aims to enroll 436 people across multiple sites.

What this could mean

Our plain-language read of the trial. This is informational only, not medical advice or a prediction.

Active substance: Udenafil
What this could lead to: If it works, this could lead to a new treatment to help teens with Fontan circulation exercise more easily and have better heart function.
What could go wrong: This is a Phase 3 trial, but udenafil may not improve exercise capacity more than placebo. Side effects from the drug are possible.

This is an AI summary of the original study and may miss details. Read our disclaimer.

Study facts

What this study's own registry entry says, in plain language.

Phase

Phase 3

Large-scale testing in a bigger group. Usually the last step before a treatment can be approved.

Participants

About 436 people

The number the study aims to enrol. It can still change while the study runs.

Started

Oct 2023

Expected to finish

Oct 2025

An estimate. End dates often move.

Lead sponsor

A company

The lead sponsor is a pharmaceutical, biotech, or medical-device company.

Who can take part

This study's own entry requirements. Only the study team can say for certain whether you qualify.

Ages

12 to 18 years

Sex

Anyone

Healthy volunteers

Not accepted

This study is not open to healthy volunteers. The entry requirements below say who it is open to.

Show the full entry requirements

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: 1. Males and females with Fontan physiology who are 12 to less than 19 years of age at enrollment. 2. Participant consent or parental/guardian consent and participant assent. 3. Participant fluency in primary language of country in which study is being conducted. 4. Current antiplatelet or anticoagulant therapy. Exclusion Criteria: 1. Height \< 132 cm. 2. Weight \< 40 kg. 3. Hospitalization for acute decompensated heart failure within the last 12 months. 4. Current intravenous inotropic drugs. 5. Undergoing evaluation for heart transplantation or listed for transplantation. 6. Diagnosis of active protein losing enteropathy or plastic bronchitis within the last 3 years, or a history of liver cirrhosis. 7. Known Fontan baffle obstruction, branch pulmonary artery stenosis, or pulmonary vein stenosis resulting in a mean gradient of \> 4 mmHg between the regions proximal and distal to the obstruction as measured by either catheterization or echocardiography, obtained prior to screening for the trial. 8. Single lung physiology with greater than 80% flow to one lung. 9. Failure to achieve maximal exertion (defined as RER \< 1.10) on screening/baseline exercise test. 10. Peak minute oxygen consumption (VO2) less than 45% or ≥ 80% of predicated for age and gender at enrollment. 11. Severe ventricular dysfunction assessed qualitatively by clinical echocardiography within 6 months prior to enrollment. 12. Severe valvar regurgitation, ventricular outflow obstruction, or severe aortic arch obstruction assessed by clinical echocardiography within six months prior to enrollment. 13. History of significant renal (serum creatinine \> 2.0), hepatic (serum AST and/or ALT \> 3 times upper limit of normal), gastrointestinal or biliary disorders that could impair absorption, metabolism or excretion of orally administered medications. 14. Inability to complete exercise testing at baseline screening. 15. Subjects with a pacemaker whose heart rate at peak exercise is controlled by the extrinsic pacemaker as opposed to a native atrial rhythm. 16. History of PDE-5 inhibitor use within 12 months prior to enrollment. (Treatment is defined as chronic therapy as opposed to a single dose.) 17. History of any other medication for treatment of pulmonary hypertension within 3 months before study onset. 18. Known intolerance to oral udenafil. 19. Frequent use of medications or other substances that inhibit or induce CYP3A4. 20. Current use of alpha-blockers or nitrates. 21. Ongoing or planned participation in another research protocol that would either prevent successful completion of planned study testing or invalidate its results. 22. Noncardiac medical, psychiatric, and/or social disorder that would prevent successful completion of planned study testing or would invalidate its results. 23. Cardiac care, ongoing or planned, at a non-study center that would impede study completion. 24. For females: Pregnancy at the time of screening, pregnancy planned before study completion, or refusal to use an acceptable method of contraception for study duration if sexually active. 25. Unable to abstain or limit intake of grapefruit juice and grapefruit containing drinks during the duration of the trial. 26. Refusal to provide written informed consent/assent. 27. In the opinion of the investigator, the subject is likely to be non-compliant with the study protocol. 28. History of clinically significant thromboembolic event, in the option of the site Principal Investigator, that may put the subject at increased risk of a subsequent event while participating in the study. 29. Coronavirus disease 2019 (COVID-19) vaccination or symptoms of COVID-19 infection within 7 days of Visit 1. 30. Not taking antiplatelet or anticoagulant therapy.

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Conditions

The condition(s) this trial relates to.

univentricular cardiopathy

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

Single ventricle heart disease

How to take part

Only the study team decides who joins. These are the ways to reach them.

The places running it

40 sites in 2 countries. The list below names each one and where it is.
The official record

ClinicalTrials.gov lists the study team's own contact details, including names and phone numbers. We don't republish those.

Open the record ↗
A doctor treating you

A doctor who knows your case can contact a study site on your behalf, and can tell you whether this study is worth pursuing at all.

Contacts and locations

Locations

Arkansas Children's
RECRUITING

Little Rock, Arkansas, 72202, United States
Boston Children's Hospital
RECRUITING

Boston, Massachusetts, 02115, United States
Children's Healthcare of Atlanta
RECRUITING

Atlanta, Georgia, 30329, United States
Children's Hospital of Colorado
RECRUITING

Denver, Colorado, 80045, United States
Children's Hospital of Georgia
RECRUITING

Augusta, Georgia, 30912, United States
Children's Hospital of Los Angeles
RECRUITING

Los Angeles, California, 90027, United States
Children's Hospital of Philadelphia
RECRUITING

Philadelphia, Pennsylvania, 19104, United States
Children's Hospital of Pittsburgh
RECRUITING

Pittsburgh, Pennsylvania, 15224, United States
Children's Hospital of Wisconsin
RECRUITING

Milwaukee, Wisconsin, 53226, United States
Children's Mercy Hospital Kansas City
RECRUITING

Kansas City, Missouri, 64108, United States
Childrens National Medical Center
RECRUITING

Washington D.C., District of Columbia, 20010, United States
Cincinnati Childrens Hospital Medical Center
RECRUITING

Cincinnati, Ohio, 45206, United States
Cleveland Clinic
RECRUITING

Cleveland, Ohio, 44195, United States
[email protected]
NOT_YET_RECRUITING

Charlotte, North Carolina, 28204, United States
Duke University Medical Center
RECRUITING

Durham, North Carolina, 27710, United States
Joe DiMaggio Children's Hospital
RECRUITING

Hollywood, Florida, 33021, United States
Johns Hopkins All Children's Hospital
RECRUITING

St. Petersburg, Florida, 33701, United States
Lurie Children's Hospital
RECRUITING

Chicago, Illinois, 60611, United States
MUSC Pediatric Research Group
RECRUITING

Charleston, South Carolina, 29425, United States
Mt. Sinai Children's Hospital
NOT_YET_RECRUITING

New York, New York, 10029, United States
Nationwide Children's Hospital
RECRUITING

Columbus, Ohio, 43215, United States
Nemours Children's Hospital
RECRUITING

Wilmington, Delaware, 19803, United States
New York-Presbyterian Children's Hospital
RECRUITING

New York, New York, 10032, United States
Phoenix Children's Hospital
RECRUITING

Phoenix, Arizona, 85016, United States
Primary Children's Medical Center
RECRUITING

Salt Lake City, Utah, 84113, United States
Rady Children's Hospital
RECRUITING

San Diego, California, 92123, United States
Seattle Children's Hospital
RECRUITING

Seattle, Washington, 98105, United States
Sejong General Hospital
RECRUITING

Bucheon-si, Gyeonggi-do, 14754, South Korea
Seoul National University Children's Hospital
RECRUITING

Seoul, 03080, South Korea
Texas Children's Hospital
RECRUITING

Houston, Texas, 77030, United States
UCSF Benioff Children's Hospital
RECRUITING

San Francisco, California, 94158, United States
UF Health Shands Hospital
RECRUITING

Gainesville, Florida, 32608, United States
UT Southwestern Medical Center
RECRUITING

Dallas, Texas, 75235, United States
University of Chicago
RECRUITING

Chicago, Illinois, 60637, United States
University of Michigan
RECRUITING

Ann Arbor, Michigan, 48109, United States
University of Nebraska Children's Hospital and Medical Center
RECRUITING

Omaha, Nebraska, 68114, United States
Vanderbilt University Medical Center
RECRUITING

Nashville, Tennessee, 37232, United States
Washington University
RECRUITING

St Louis, Missouri, 63130, United States
Yale School of Medicine
RECRUITING

New Haven, Connecticut, 06510, United States
Yonsei Severance Hospital
RECRUITING

Seoul, 03722, South Korea

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