Muscle MRI in Duchenne muscular dystrophy patients after fordadistrogene movaparvovec

MRI is an important noninvasive tool that can be used for monitoring progression of Duchenne muscular dystrophy (DMD). We present muscle volume (MV) and fat fraction (FF) measures from MRI examinations of ambulatory participants with DMD during 2 years of follow-up with fordadistrogene movaparvovec, a recombinant adeno-associated virus serotype-9–based gene therapy in development for DMD. In this ongoing, phase 1b, open-label, nonrandomized study (NCT03362502), MRI assessments and functional data were evaluated following treatment with fordadistrogene movaparvovec. Eligible participants (N = 19; male, aged 4–12 years at enrollment), received a single intravenous infusion of low-dose (1E14 vg/kg) or high-dose (3E14 vg/kg) fordadistrogene movaparvovec. An external reference (ER) cohort from another interventional trial was derived from participants who met eligibility criteria for this trial. Fordadistrogene movaparvovec–treated participants had a mean percent change from baseline (�B) in MV of 9.0 ± 13.5% (1 year) and 7.4 ± 16.1% (2 years). ER cohort had a respective mean �B in MV of 2.7 ± 8.3% and 2.4 ± 12.1%. MV increases were most pronounced in younger participants. MRI of thigh muscle and upper limb of participants treated with fordadistrogene movaparvovec showed increases in MV over 2 years. No clear difference in FF was seen in comparison to ER over 2 years. MRI is an important tool for monitoring Duchenne muscular dystrophy.Two-year MRI of thigh muscle and upper limb showed increases in muscle volume.No clear difference in fat fraction vs external reference was reported over 2 years. MRI is an important tool for monitoring Duchenne muscular dystrophy. Two-year MRI of thigh muscle and upper limb showed increases in muscle volume. No clear difference in fat fraction vs external reference was reported over 2 years. Clinical trial registration: ClinicalTrials.gov: NCT03362502 (https://clinicaltrials.gov/study/NCT03362502); NCT02310763 (https://clinicaltrials.gov/study/NCT02310763).