Vasodilator and Exercise Study for DMD (VASO-REx)

May 12, 2026 updated by: University of Florida

Vasodilators and Exercise as Adjuvant Therapy for Duchenne Muscular Dystrophy (VASO-REx Study)

Examining two strategies as potential adjuvant therapies for Duchenne muscular dystrophy (DMD); aerobic exercise training (to induce adaptations in skeletal muscle and improve cardiovascular health) and tadalafil, an FDA-approved vasodilator (to optimize blood flow and muscle perfusion which is impaired and often overlooked in DMD). Target: improved muscle function, vascular health, and DMD treatment.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

Duchenne muscular dystrophy (DMD) is characterized by rapid muscle deterioration, mitochondrial and vascular impairments, resulting in premature loss of ambulation and mortality. Disease-modifying therapeutics are emerging and although they are expected to improve muscle function and daily activity in boys with DMD, most are not designed to correct the vascular impairment. This impairment is due to the lack of restoration of neuronal nitric oxide synthase signaling, which is crucial for vasodilation during and after exercise. The investigators believe limitations in study design were responsible for the lack of efficacy. Therefore, this study combines tadalafil with aerobic exercise to necessitate increased blood flow and activate the drug.

This Exploratory Clinical Trial will assess two potential adjuvant therapies for ambulatory boys with DMD (6 years and older): 1) aerobic exercise training and 2) tadalafil, an FDA-approved vasodilator drug. Preclinical and clinical data, including recent findings from the principal investigator's lab, support the use of these strategies and their potential to benefit muscle perfusion, fatigue, and quality of life.

The study will first test for drug responsiveness (increase in muscle oxygenation) after a single dose. Drug-responsive boys with DMD will be randomized to a 6-month intervention of daily tadalafil or placebo, combined with structured cycle exercise training. Participants will receive exercise-related equipment for use at home and be monitored by the research team via video. The study will quantify the intervention's impact on vascular impairment, muscle pathophysiology (inflammation, fat accumulation, mitochondrial dysfunction), exertional fatigue, and cycling performance.

Our findings are expected to yield:

  1. Criteria to identify DMD patients most likely to benefit from tadalafil as adjuvant therapy.
  2. Evidence of a powerful synergy between drug impact and exercise training in DMD.

Study Type

Interventional

Enrollment (Estimated)

50

Phase

  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

  • United States
    • Florida
      • Gainesville, Florida, United States, 32603
        • Recruiting
        • University of Florida Clinical and Translational Research Building

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Child
  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Diagnosis of DMD confirmed by genetic report
  • Minimum entry age of 6.0 years old
  • Ambulatory
  • On stable glucocorticoid regimen (for > 3 months)

Exclusion Criteria:

  • Contraindication to a Magnetic resonance Imaging examination (e.g. severe claustrophobia, magnetic implants, unable/unwilling to perform test)
  • Presence of unstable medical problems, including severe cardiomyopathy, left ventricular ejection fraction <45%, cardiac conduction abnormalities as evidenced on ECG, uncontrolled seizure disorder, uncontrolled hypo or hypertension
  • Presence of a secondary condition that impacts muscle function or muscle metabolism (e.g., myasthenia gravis, endocrine disorder, mitochondrial disease)
  • Presence of a secondary condition leading to developmental delay or impaired motor control (e.g., cerebral palsy) or previous history of unprovoked rhabdomyolysis
  • Contraindications to phosphodiesterase 5 inhibitors (use of nitrates, alpha-adrenergic blockers, other phosphodiesterase 5 inhibitors) or other medications known to modulate blood flow or muscle metabolism
  • Participation in currently approved FDA trials or other investigational clinical trials during the period of the study

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Tadalafil and Exercise Arm
Participants receive tadalafil weight-dependent dosage to take daily for 6 months (26 weeks).
Drug: Tadalafil
Patients will be given either the intervention medication or a placebo (double-blinded, randomized trial) and will be asked to take the medication every day for 6 months in conjunction with weekly exercise sessions.
Other: Exercise Training
The home-based cycling exercise training program is designed to improve muscle strength and endurance. Participants will engage in individualized exercise sessions up to four times per week, lasting up to 40 minutes each. Live video and heart rate monitoring will ensure proper exercise performance and allow for adjustments to the program throughout the study. The participants will receive the exercise equipment for use at home.
Placebo Comparator: Placebo and Exercise Arm
Participants receive a tadalafil placebo tablet matching the tadalafil weight-dependent dosage to take daily for 6 months (26 weeks).
Other: Exercise Training
The home-based cycling exercise training program is designed to improve muscle strength and endurance. Participants will engage in individualized exercise sessions up to four times per week, lasting up to 40 minutes each. Live video and heart rate monitoring will ensure proper exercise performance and allow for adjustments to the program throughout the study. The participants will receive the exercise equipment for use at home.
Drug: Placebo
Patients will be given either the intervention medication or a placebo (double-blinded, randomized trial) and will be asked to take the medication every day for 6 months in conjunction with weekly exercise sessions.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Vascular responsiveness after muscle contraction to a single dose of tadalafil.
Time Frame: up to 4 weeks after the completion of Visits 1 and 2 of Aim 1.
Responsiveness will be determined by an increase in post-contractile muscle oxygenation using MRI-Blood Oxygen Level Dependent (BOLD) responses after dosing compared to before. Study participants demonstrating an increase (>50%) in post-contractile BOLD after tadalafil will be enrolled into Aim 2 of this study.
up to 4 weeks after the completion of Visits 1 and 2 of Aim 1.
Cycling time to fatigue
Time Frame: Baseline and 6 month follow-up visits of Aim 2.

The study will assess the impact of tadalafil on exercise performance and fatigue resistance compared to placebo. Participants will undergo a maximal effort cycling test before and after the intervention period. The time it takes for participants to reach exhaustion (TTE) will be recorded as the primary outcome measure.

Measurement: Time to exhaustion (TTE) during a maximal effort cycling test on a recumbent, stationary ergometer. This test will quantify fatigue resistance by measuring the duration participants can sustain maximal effort cycling.
Baseline and 6 month follow-up visits of Aim 2.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Quadriceps muscle Fat Fraction
Time Frame: Aim 1 and Aim 2 (baseline and 6 month follow-up)
This outcome serves as a measure of disease severity. This measure is a sensitive and reproducible biomarker of DMD muscle pathology.
Aim 1 and Aim 2 (baseline and 6 month follow-up)
Metabolic recovery
Time Frame: Through study completion, an average of 3 years.
The rate of phosphocreatine resynthesis after leg exercise will be quantified and serves as index of skeletal muscle mitochondrial oxidative capacity. (Part of Aim 2 of the study).
Through study completion, an average of 3 years.
cardiopulmonary exercise testing (CPET) - Peak aerobic capacity (VO2max)
Time Frame: Through study completion, an average of 3 years.

Patients will undergo cycling exercise at submaximal and peak workloads to quantify peak aerobic capacity, ventilation.

Peak Oxygen Uptake (VO2max): This measure quantifies the maximum amount of oxygen the body can utilize during exercise, assessed through maximal cycling effort in a CPET. It serves as a primary indicator of overall cardiovascular and aerobic fitness.

Peak aerobic capacity: VO2max reflects the maximum oxygen utilization capacity, indicating overall cardiovascular fitness.
Through study completion, an average of 3 years.
cardiopulmonary exercise testing (CPET) - Minute Ventilation (VE)
Time Frame: Through study completion, an average of 3 years.

Minute Ventilation (VE): This measure reflects the total volume of air breathed per minute during exercise, assessed throughout the CPET. Evaluating VE at various workloads provides insights into respiratory efficiency and potential limitations during exercise.

Respiratory efficiency: VE and VE/VO2 assess how well the body utilizes oxygen during exercise, revealing potential respiratory limitations.
Through study completion, an average of 3 years.
cardiopulmonary exercise testing (CPET) - Ventilatory Equivalent for Oxygen (VE/VO2)
Time Frame: Through study completion, an average of 3 years.

Ventilatory Equivalent for Oxygen (VE/VO2): This ratio compares ventilation to oxygen uptake, calculated throughout the CPET. It indicates the efficiency of oxygen utilization during exercise and potential respiratory limitations.

Respiratory efficiency: VE and VE/VO2 assess how well the body utilizes oxygen during exercise, revealing potential respiratory limitations.
Through study completion, an average of 3 years.
cardiopulmonary exercise testing (CPET) - Gas Exchange Threshold (GET)
Time Frame: Through study completion, an average of 3 years.

Gas Exchange Threshold (GET): This point during exercise marks the transition from predominantly aerobic to anaerobic metabolism, identified through changes in blood lactate levels and other CPET parameters. Analyzing GET helps assess exercise tolerance and potential for improvement.

Exercise tolerance and fatigue: GET and W at AT pinpoint the intensity at which fatigue and performance decline become significant, offering insights into exercise limitations and potential for improvement.
Through study completion, an average of 3 years.
cardiopulmonary exercise testing (CPET) - Workload at Anaerobic Threshold (W at AT)
Time Frame: Through study completion, an average of 3 years.

Workload at Anaerobic Threshold (W at AT): This measure, derived from the CPET, quantifies the power output at which anaerobic metabolism significantly contributes to energy production. It reflects exercise intensity at which fatigue and performance decline become prominent.

Exercise tolerance and fatigue: GET and W at AT pinpoint the intensity at which fatigue and performance decline become significant, offering insights into exercise limitations and potential for improvement.
Through study completion, an average of 3 years.
The 100-meter timed test (100m)
Time Frame: Through study completion, an average of 3 years.
The 100m is a fixed distance test of maximal performance and will be completed according to published guidelines.
Through study completion, an average of 3 years.
the North Star Ambulatory Assessment (NSAA)
Time Frame: Through study completion, an average of 3 years.
The North Star Ambulatory Assessment (NSAA) is a 17-item rating scale that is used to measure physical function and motor abilities in ambulatory boys with DMD and is increasingly being used in clinical trials as an overall measure of physical function.
Through study completion, an average of 3 years.
The 4-stair climb
Time Frame: Through study completion, an average of 3 years.
The time to ascend 4-stairs is a strength-measure. The patient is instructed to climb four standard steps (six inches in height each) with two handrails as fast as safely possible, using the rails if needed.
Through study completion, an average of 3 years.
The Physical activity questionnaire (PAQ-C)
Time Frame: Through study completion, an average of 3 years.
The PAQ-C is a self-administered, 7-day recall instrument developed to assess general levels of physical activity throughout the elementary school year for students in grades 4 to 8 and approximately 8 to 14 years, with high validity. Although reliability is considered to be moderate, other physical activity questionnaires are less reliable. Results will be correlated with indices of disease severity and tadalafil responsiveness.
Through study completion, an average of 3 years.
Pulmonary function testing - vital capacity (FVC)
Time Frame: Through study completion, an average of 3 years.

Measurement: FVC, measured using a standard spirometer according to American Thoracic Society guidelines. This is the maximum amount of air an individual can forcefully exhale after a full inhalation.

Significance: FVC reflects the total lung capacity and is a key indicator of overall lung volume and function. It can help identify restrictive lung diseases, where lung volume is limited, and track respiratory health changes over time.
Through study completion, an average of 3 years.
Pulmonary function testing - forced expiratory volume in 1 second (FEV1)
Time Frame: Through study completion, an average of 3 years.

Measurement: FEV1, measured using a standard spirometer according to American Thoracic Society guidelines. This is the amount of air forcefully exhaled in the first second of a maximal exhalation after a full inhalation.

Significance: FEV1 reflects the efficiency of airflow from the lungs and is sensitive to obstructive lung diseases, like asthma and Chronic Obstructive Pulmonary Disease (COPD), where airflow is impaired.
Through study completion, an average of 3 years.
Neurology Quality of Life (NeuroQoL) pediatric lower extremity function
Time Frame: Through study completion, an average of 3 years.
Questionnaire used to measure patient-reported outcomes of intervention impact.
Through study completion, an average of 3 years.
Patient Reported Outcomes Measurement Information System (PROMIS) pediatric fatigue
Time Frame: Through study completion, an average of 3 years.
Questionnaire used to measure patient-reported outcomes of intervention impact.
Through study completion, an average of 3 years.
PROMIS parent proxy for physical activity
Time Frame: Through study completion, an average of 3 years.
Questionnaire used to measure patient's parent-reported outcomes of intervention impact.
Through study completion, an average of 3 years.
PROMIS pediatric physical activity
Time Frame: Through study completion, an average of 3 years.
Questionnaire used to measure patient's parent-reported outcomes of intervention impact.
Through study completion, an average of 3 years.
Physical Activity Monitoring - Daily Step Rate
Time Frame: Through study completion, an average of 3 years.
Measurement: Total number of steps taken per day, assessed using the Actigraph activity monitor.
Through study completion, an average of 3 years.
Physical Activity Monitoring - Time in Low-Level Activity
Time Frame: Through study completion, an average of 3 years.
Measurement: Total time spent in low-intensity physical activity per day, as defined by Actigraph criteria.
Through study completion, an average of 3 years.
Physical Activity Monitoring - Time in Moderate-Level Activity
Time Frame: Through study completion, an average of 3 years.
Measurement: Total time spent in moderate-intensity physical activity per day, as defined by Actigraph criteria.
Through study completion, an average of 3 years.
Physical Activity Monitoring - Time in High-Level Activity
Time Frame: Through study completion, an average of 3 years.
Measurement: Total time spent in high-intensity physical activity per day, as defined by Actigraph criteria.
Through study completion, an average of 3 years.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Florida

Collaborators

National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)

Investigators

  • Principal Investigator: Tanja Taivassalo, Ph.D., University of Florida, College of Medicine, Department of Physiology and Aging

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

June 5, 2024

Primary Completion (Estimated)

November 1, 2026

Study Completion (Estimated)

November 1, 2026

Study Registration Dates

First Submitted

February 9, 2024

First Submitted That Met QC Criteria

March 1, 2024

First Posted (Actual)

March 4, 2024

Study Record Updates

Last Update Posted (Actual)

May 15, 2026

Last Update Submitted That Met QC Criteria

May 12, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • IRB202301491
  • 1R21AR079755-01 (U.S. NIH Grant/Contract)
  • PRO00050023 (Other Identifier: UFIRST)

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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