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Duchenne muscular dystrophy, dystrophin, viltolarsen, exon skipping, clinical efficacy



Duchenne muscular dystrophy (DMD) is caused by DMD gene mutations, resulting in absence of functional dystrophin protein. Viltolarsen, an exon 53 skipping therapy, significantly increased dystrophin levels in patients with DMD. Presented here are completed study results of > 4 years of functional outcomes in viltolarsen-treated patients compared to a historical control group (Cooperative International Neuromuscular Research Group Duchenne Natural History Study [CINRG DNHS]).


To evaluate the efficacy and safety of viltolarsen for an additional 192 weeks in boys with DMD.


This phase 2, open-label, 192-week long-term extension (LTE) study (NCT03167255) evaluated the efficacy and safety of viltolarsen in participants aged 4 to < 10 years at baseline with DMD amenable to exon 53 skipping. All 16 participants from the initial 24-week study enrolled into this LTE. Timed function tests were compared to the CINRG DNHS group. All participants received glucocorticoid treatment. The primary efficacy outcome was time to stand from supine (TTSTAND). Secondary efficacy outcomes included additional timed function tests. Safety was continuously assessed.


For the primary efficacy outcome (TTSTAND), viltolarsen-treated patients showed stabilization of motor function over the first two years and significant slowing of disease progression over the following two years compared with the CINRG DNHS control group which declined. Viltolarsen was well tolerated, with most reported treatment-emergent adverse events being mild or moderate. No participants discontinued drug during the study.


Based on the results of this 4-year LTE, viltolarsen can be an important treatment strategy for DMD patients amenable to exon 53 skipping.


∗Correspondence to: Paula R. Clemens, MD, Department of Neurology, University of Pittsburgh School of Medicine, 3550 Terrace St, Pittsburgh, PA 15261, USA. Tel.: +1 412 648 9762; Fax: +1 412 648 0036; E-mail:

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DOI: 10.3233/JND-221656

This article was published in Journal of Neuromuscular Diseases, vol. 10, no. 3, pp. 439-447, 2023. IOS Press

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Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.