Tadalafil as Adjuvant Therapy for DMD

Study Overview
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Brief Summary
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This project will assess the vascular responsiveness in leg muscles of boys with Duchenne muscular dystrophy (DMD) to one single dose of tadalafil, a common vasodilator drug, using non-invasive techniques (MRI or Doppler ultrasound) and exercise testing. These findings will provide proof of concept for a subsequent intervention study to demonstrate efficacy of longer-term tadalafil to counter sympathetic vasoconstriction and slow disease progression in DMD. It will also inform whether a group of patients do not respond to the drug.

Detailed Description
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This project will target up to 25 ambulatory boys with DMD aged 7-13 years. Because the vascular impact of tadalafil is immediate, we will confirm that the drug target is valid target in lower extremities by assessing the change in post-exercise microvascular perfusion using Blood Oxygen Level-Dependent (BOLD) MRI or change in post-exercise hyperemia using Doppler ultrasonography. We will also assess the functional impact of the drug through exercise testing. Patients will be randomized to undergo the above-mentioned assessments with or without the study drug on two separate visits. Time function tests, MRI-based fat fraction and inflammation measurements will also be obtained in all patients, thus characterizing disease severity and provide a sampling of information on whether a subset of patients do not respond to the drug. This information may be used to inform future trials as to the appropriate target population for PDE5i as well as account for potential failures in a previously published phase 3 clinical trial.

Official Title
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Tadalafil as an Adjuvant to Therapy for Duchenne Muscular Dystrophy

Conditions
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Duchenne Muscular Dystrophy

Intervention / Treatment
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* Drug: Tadalafil
* Drug: Tadalafil


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Diagnosis of DMD confirmed by 1) clinical history with features before the age of five, 2) physical examination, 3) elevated serum creatine kinase level and 4) absence of dystrophin expression, as determined by immunostaining or Western blot (<2%) and/or DNA confirmation of dystrophin mutation. Minimum entry age of 7.0 years Ambulatory Exclusion Criteria: Older than 13.0 years of age Contraindication to an MR examination (e.g. aneurysm clip, severe claustrophobia, magnetic implants) Presence of unstable medical problems Presence of a secondary condition that impacts muscle function or muscle metabolism (e.g. myasthenia gravis, endocrine disorder, mitochondrial disease) Contraindications to Tadalafil (use of nitrates, alpha-adrenergic blockers, other PDE5A inhibitors)

Ages Eligible for Study
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Minimum Age: 7 Years
Maximum Age: 13 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: Parallel Assignment
Interventional Model Description: Pre/post single dose tadalafil
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Tadalafil plus BOLD-MRI (Schedule A)<br>The intervention is the same as in Schedule B; this arm will use BOLD-MRI as the technique to monitor drug impact on skeletal muscle. | Drug: Tadalafil<br>* Patient will be randomized to one dose of 0.6 mg/kg tadalafill on one of two study visits. On both visits, assessments (MRI, exercise testing, clinical function) will be performed 3 hours after time of dosing.<br>* Other names: Cialis;|
| Experimental: Tadalafil plus Doppler ultrasound (Schedule B)<br>The intervention is the same as in Schedule A; this arm will use Doppler ultrasound as the technique to monitor drug impact on skeletal muscle. | Drug: Tadalafil<br>* Patient will be randomized to one dose of 0.6 mg/kg tadalafill on one of two study visits. On both visits, assessments (Doppler US, exercise testing, clinical function) will be performed 3 hours after time of dosing.<br>* Other names: Cialis;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in post-contractile BOLD response after tadalafil dosing | MRI technique to measure microvascular function in skeletal muscle | MRI will be done 3 hours after dosing/no-dosing on two separate study visits | 
| Change in post-exercise hyperemia after tadalafil dosing | Doppler ultrasound will be used to measure blood flow | Doppler ultrasound will be done 3 hours after dosing/no-dosing on two separate study visits | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in submaximal exercise capacity after tadalafil dosing | incremental cardiopulmonary exercise testing on cycle ergometer will be performed to measure heart rate and parameters of exercise performance. | Cycle testing will be done 4 hours after dosing/no-dosing on two separate study visits | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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therapy, treatment strategy, vasodilator, exercise