The proposed research is for the second competitive renewal of a long-term project to develop imaging biomarkers for Duchenne muscular dystrophy (DMD). Noninvasive outcome measures that provide unbiased patient assessments and reliably evaluate drug responses in clinical trials are essential to develop curative therapies for muscular dystrophies. In the previous funding cycles, we developed and validated lower extremity quantitative magnetic resonance imaging (qMR) biomarkers for ambulatory patients with DMD and modeled the disease trajectory in upper and lower extremity muscles. These qMR biomarkers are now used as primary and secondary endpoints in a number of international clinical trials. In this application one major objective is to extend our DMD work by focusing on older DMD patients with advanced disease progression. More than 50% of the DMD population is nonambulant, yet there are few outcome measures that permit their inclusion in clinical trials. We propose to 1) develop composite qMR biomarkers using quantitative whole-body imaging and 2) validate novel qMR biomarkers that assess respiratory muscle quality and can predict a decline in respiratory function, a major cause of death in muscular dystrophies. We hypothesize that composite qMR biomarkers?statistical constructs that optimally combine fat fraction measures in multiple muscles?are responsive across a wide range of motor abilities in DMD. We will leverage the large (older) DMD cohort currently enrolled in the ImagingDMD natural history study to test these two new qMR biomarkers for advanced disease stages. We also propose to extend our biomarker development work to patients with Becker muscular dystrophy (BMD), the milder allelic form of the disease. Breakthroughs in gene delivery and exon skipping technology have resulted in production of truncated dystrophin in variable amounts, effectively converting the DMD phenotype into BMD. These therapeutic developments are expected to change the landscape for the next generation of DMD patients. Thus, to assist future trials targeting dystrophin restoration, we will examine the critical relationship between dystrophin expression, mutation site and qMR biomarkers of muscle quality in BMD patients, setting the stage for informed in vivo monitoring of dystrophin rescue across muscles. This project addresses critical barriers in therapeutic development and provides the potential for a paradigm shift in clinical trial design in DBMD. In addition, this project will help inform future molecular based therapies and will address a missing piece in translational gene restoration in DMD. All natural history data are shared with the community.
This study addresses critical barriers in therapeutic development for muscular dystrophy, a genetic muscle wasting disease. We will develop and test new outcome measures that provide an unbiased assessments of muscle quality, without the need for muscle biopsies. We will also collect much needed natural history data.
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