Tadalafil and Sildenafil for Duchenne Muscular Dystrophy

Study Overview
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Brief Summary
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This study, supported by Parent Project Muscular Dystrophy, will determine if tadalafil or sildenafil can improve muscle blood flow during exercise in boys with Duchenne muscular dystrophy.

Detailed Description
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Duchenne muscular dystrophy (DMD) is a rare, progressive and fatal muscle disease affecting boys and accounts for 80% of muscular dystrophy cases. Tadalafil and sildenafil are medications approved by the FDA for the treatment of erectile dysfunction and pulmonary hypertension. This class of medication improves muscle blood flow in a mouse model of muscular dystrophy, but their benefit to boys with DMD is unknown. The purpose of this study is to 1) determine if tadalafil or sildenafil can improve muscle blood flow during exercise in boys with DMD; and 2) to inform the design of a subsequent, randomized, multi-center trial with clinical endpoints. The investigators will enroll boys with DMD between the ages of 7 and 15 years who are ambulatory and without clinical heart failure. Participants will undergo 6 visits over the course of 5 weeks. The initial visit will include a medical history, physical exam, echocardiogram, and blood draw to determine eligibility for the study. Boys will be given a Holter monitor (a heart monitor) to wear for 48 hours to observe any irregular heartbeats or abnormalities. Eligible boys will be randomized to one of the two study drugs: tadalafil or sildenafil. The boys will take a low dose (0.25mg/kg) of the study drug for the first 2 days and an intermediate dose (0.5mg/kg) for the subsequent 5 days. Then, boys will take a higher dose (1.0mg/kg) of the study drug for 1 week. Tadalafil will be taken once daily and sildenafil will be taken four times daily. Study visits will occur 2 times at baseline, 2 times during the medication, and 1 time after washout of the medication. For these visits, boys will undergo an arm blood flow and hand grip exercise protocol. In this procedure, blood flow and oxygen delivery to the forearm muscles will be measured (noninvasively) before and during application of lower body negative pressure at rest and during handgrip exercise. Lower body negative pressure stimulates the blood flow changes that normally occur when a person sits up after lying down. During these visits, boys will complete a quality of life questionnaire, echocardiogram, and 6-minute walk tests. At home, boys will wear an accelerometer to measure physical activity and a Holter monitor to check for irregular heartbeats. For boys who wish to continue with the study, there will be an option to cross-over and complete study visits with the drug they did not originally receive.

Official Title
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Functional Muscle Ischemia and PDE5A Inhibition in Duchenne Muscular Dystrophy

Conditions
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Duchenne Muscular Dystrophy

Intervention / Treatment
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* Drug: Tadalafil
* Drug: Sildenafil


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Diagnosis of DMD confirmed by muscle biopsy or DNA analysis Age 7-15y Ambulatory No clinical evidence of heart failure Exclusion Criteria: Hypertension, diabetes, or heart failure by standard clinical criteria Elevated BNP level (>100 pg/ml) LVEF < 50% Wheelchair bound Cardiac rhythm disorder, specifically: rhythm other than sinus, SVT, atrial fibrillation, ventricular tachycardia Continuous ventilatory support Liver disease Renal impairment Contraindications to tadalafil or sildenafil (use of nitrates, alpha-blockers, CYP3A inhibitors, amlodipine, or other PDE5A inhibitors)

Ages Eligible for Study
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Minimum Age: 7 Years
Maximum Age: 15 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Tadalafil<br> | Drug: Tadalafil<br>* Escalating dose (0.25 mg/kg, 0.5 mg/kg, 1.0 mg/kg; once daily) over 2 weeks<br>* Other names: Adcirca;|
| Experimental: Sildenafil<br> | Drug: Sildenafil<br>* Escalating dose (0.25 mg/kg, 0.5 mg/kg, 1.0 mg/kg; four times daily) over 2 weeks<br>* Other names: Revatio;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Functional muscle ischemia | Measured by the decrease in muscle tissue oxygenation (near infrared spectroscopy) and blood flow (Doppler ultrasound) evoked by reflex sympathetic activation in exercising forearm muscle. | For 5 study visits | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cardiac Function | Echocardiogram | For 5 study visits | 
| EKG Monitoring | 48 hour Holter monitoring | 5 times over about 6 weeks | 
| 6 Minute Walk Test |  | For 5 study visits | 
| Physical Activity | Assessed by accelerometers | 5 times over about 6-weeks | 
| Quality of Life | PedsQL inventory | For 5 study visits | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Duchenne, muscular dystrophy, tadalafil, sildenafil, muscle ischemia, exercise