INTRODUCTION
DMD, muscle dystrophin, recessive, neuromuscular disorder
DUCHENNE MUSCULAR DYSTROPHY (DMD), NONSENSE MUTATION
Duchenne muscular dystrophy (DMD) is an X-linked, recessive, neuromuscular disorder resulting from DMD gene mutations (deletions, duplications, nonsense mutations) causing a loss of dystrophin protein and function in striated muscle [Exon skipping therapies use antisense oligonucleotides to restore the open reading frame of the pre-messenger RNA by changing DMD out-of-frame deletions to in-frame deletions [An initial phase 2, randomized, 24-week clinical trial that evaluated the efficacy, safety, and tolerability of viltolarsen in boys 4 to < 10 years of age with DMD demonstrated muscle dystrophin production [The primary objective of the LTE study was to evaluate the effects on mobility and safety of 40- or 80-mg/kg/week intravenous doses of viltolarsen for an additional 192-week treatment period for a total of 216 weeks of treatment from the start of the initial phase 2 study to the completion of the open-label extension study. An interim analysis at 2 years was published, and the data presented here are the final results following 4 years of treatment [