A Phase 2 interventional study of Tadalafil and Placebo in Duchenne Muscular Dystrophy, Duchenne Disease and Muscular Dystrophy, sponsored by University of Florida. Recruiting at 1 site in United States. Open to male participants aged 6 Years and older. Per ClinicalTrials.gov, last updated 2026-05-15.
Sponsored by University of Florida · Phase 2, Interventional, and Treatment
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.
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:
481 studies on the registry are indexed under Muscular Dystrophy, Duchenne; 108 are open to participants now.
This study's planned enrollment of 50 is above the median of 26 across 332 interventional studies indexed under Muscular Dystrophy, Duchenne.
Browse Muscular Dystrophy, Duchenne studies →University of Florida is the lead sponsor of 1,287 studies on the registry; 199 are open to participants now.
Of its 180 completed or terminated interventional studies of FDA-regulated products, 143 (79%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
A recording of the heart’s electrical activity, taken with stickers on the chest, arms and legs. It takes a few minutes and does not hurt.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
LVEF (left ventricular ejection fraction)
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECG (electrocardiogram)
A recording of the heart’s electrical activity, taken with stickers on the chest, arms and legs. It takes a few minutes and does not hurt.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants receive tadalafil weight-dependent dosage to take daily for 6 months (26 weeks).
Drug: Tadalafil · Other: Exercise Training
Participants receive a tadalafil placebo tablet matching the tadalafil weight-dependent dosage to take daily for 6 months (26 weeks).
Drug: Placebo · Other: Exercise Training
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.
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.
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.
Vascular responsiveness after muscle contraction to a single dose of tadalafil.
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.
Time frame: up to 4 weeks after the completion of Visits 1 and 2 of Aim 1.
Cycling time to fatigue
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.
Time frame: Baseline and 6 month follow-up visits of Aim 2.
Quadriceps muscle Fat Fraction
This outcome serves as a measure of disease severity. This measure is a sensitive and reproducible biomarker of DMD muscle pathology.
Time frame: Aim 1 and Aim 2 (baseline and 6 month follow-up)
Metabolic recovery
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).
Time frame: Through study completion, an average of 3 years.
cardiopulmonary exercise testing (CPET) - Peak aerobic capacity (VO2max)
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.
Time frame: Through study completion, an average of 3 years.
cardiopulmonary exercise testing (CPET) - Minute Ventilation (VE)
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.
Time frame: Through study completion, an average of 3 years.
cardiopulmonary exercise testing (CPET) - Ventilatory Equivalent for Oxygen (VE/VO2)
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.
Time frame: Through study completion, an average of 3 years.
cardiopulmonary exercise testing (CPET) - Gas Exchange Threshold (GET)
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.
Time frame: Through study completion, an average of 3 years.
cardiopulmonary exercise testing (CPET) - Workload at Anaerobic Threshold (W at AT)
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.
Time frame: Through study completion, an average of 3 years.
The 100-meter timed test (100m)
The 100m is a fixed distance test of maximal performance and will be completed according to published guidelines.
Time frame: Through study completion, an average of 3 years.
the North Star Ambulatory Assessment (NSAA)
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.
Time frame: Through study completion, an average of 3 years.
The 4-stair climb
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.
Time frame: Through study completion, an average of 3 years.
The Physical activity questionnaire (PAQ-C)
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.
Time frame: Through study completion, an average of 3 years.
Pulmonary function testing - vital capacity (FVC)
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.
Time frame: Through study completion, an average of 3 years.
Pulmonary function testing - forced expiratory volume in 1 second (FEV1)
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.
Time frame: Through study completion, an average of 3 years.
Neurology Quality of Life (NeuroQoL) pediatric lower extremity function
Questionnaire used to measure patient-reported outcomes of intervention impact.
Time frame: Through study completion, an average of 3 years.
Patient Reported Outcomes Measurement Information System (PROMIS) pediatric fatigue
Questionnaire used to measure patient-reported outcomes of intervention impact.
Time frame: Through study completion, an average of 3 years.
PROMIS parent proxy for physical activity
Questionnaire used to measure patient's parent-reported outcomes of intervention impact.
Time frame: Through study completion, an average of 3 years.
PROMIS pediatric physical activity
Questionnaire used to measure patient's parent-reported outcomes of intervention impact.
Time frame: Through study completion, an average of 3 years.
Physical Activity Monitoring - Daily Step Rate
Measurement: Total number of steps taken per day, assessed using the Actigraph activity monitor.
Time frame: Through study completion, an average of 3 years.
Physical Activity Monitoring - Time in Low-Level Activity
Measurement: Total time spent in low-intensity physical activity per day, as defined by Actigraph criteria.
Time frame: Through study completion, an average of 3 years.
Physical Activity Monitoring - Time in Moderate-Level Activity
Measurement: Total time spent in moderate-intensity physical activity per day, as defined by Actigraph criteria.
Time frame: Through study completion, an average of 3 years.
Physical Activity Monitoring - Time in High-Level Activity
Measurement: Total time spent in high-intensity physical activity per day, as defined by Actigraph criteria.
Time frame: Through study completion, an average of 3 years.
Started Jun 2024 (actual). Primary completion is estimated for Nov 2026, 29 months after the start.
Of 47 phase 2 interventional studies under Muscular Dystrophy, Duchenne, half reached primary completion within 31 months of starting (the median), counting those still running; a quarter within 20 and three quarters within 42. This study's planned 29 months is close to that.
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Studies of the drug tested here: Tadalafil
Muscular Dystrophy, Duchenne →