Study to Assess the Efficacy and Safety of Viltolarsen in Ambulant Boys With DMD (RACER53)

Phase 3

Completed

Brief Summary: The main objective of this study is to evaluate the efficacy of Viltolarsen compared to placebo in Duchenne muscular dystrophy (DMD) patients amenable to exon 53 skipping.

Detailed Description: This is a Phase 3 randomized, double-blind, placebo-controlled, multi-center study to assess the efficacy and safety of Viltolarsen in ambulant boys with Duchenne muscular dystrophy. Eligible patients with out-of-frame deletion mutations amenable to exon 53 skipping will be randomized to receive once weekly intravenous (IV) infusions of 80 mg/kg Viltolarsen or placebo for up to 48 weeks.

The study will enroll approximately 74 patients amenable to exon 53 skipping. Clinical efficacy will be assessed at regularly scheduled study visits, including functional tests such as Time to Stand Test (TTSTAND), Time to Run/Walk 10 Meters Test (TTRW), Six-minute Walk Test (6MWT), North Star Ambulatory Assessment (NSAA), Time to Climb 4 Steps Test (TTCLIMB) and Hand-held dynamometer (elbow extension, elbow flexion, knee extension and knee flexion on the dominant side only).

Safety will be assessed through the collection of adverse events (AEs), laboratory tests, electrocardiograms (ECGs), vital signs, and physical examinations throughout the study.

Blood samples will be taken periodically throughout the study to assess the pharmacokinetics of study drug.

Recruitment & Eligibility

Inclusion Criteria

Male ≥ 4 years and < 8 years of age
Confirmed DMD mutation(s) in the dystrophin gene that is amenable to skipping of exon 53 to restore the dystrophin mRNA reading frame
Able to walk independently without assistive devices
TTSTAND < 10 seconds
Stable dose of glucocorticoid (GC) for at least 3 months prior to study entry and is expected to remain on stable dose of GC treatment for the duration of the study
Other inclusion criteria may apply

Exclusion Criteria

Current or history of chronic systemic fungal or viral infections
Acute illness within 4 weeks prior to the first dose of study drug
Evidence of symptomatic cardiomyopathy (Note: Asymptomatic cardiac abnormality on investigation would not be exclusionary)
Allergy or hypersensitivity to the study drug or to any of its constituents
Severe behavioral or cognitive problems that preclude participation in the study, in the opinion of the investigator
Previous or ongoing medical condition, medical history, physical findings or laboratory abnormalities that could affect safety, make it unlikely that treatment and follow-up will be correctly completed or impair the assessment of study results, in the opinion of the investigator;
Surgery within the 3 months prior to the first dose of study drug or surgery is planned for anytime during the duration of the study
Participant has positive test results for hepatitis B antigen, hepatitis C antibody or human immunodeficiency virus (HIV)
Currently taking any other investigational drug or has taken any other investigational drug within 3 months prior to the first dose of study drug or within 5 times the half-life of a medication, whichever is longer
Previously enrolled in an interventional study of viltolarsen
Currently taking any other exon skipping agent or has taken any other exon skipping agent within 3 months prior to the first dose of study drug
Having taken any gene therapy
Other exclusion criteria may apply

Arm && Interventions

Group	Intervention	Description
Placebo	Placebo	Patients amenable to exon 53 skipping will receive placebo intravenous (IV) infusions, weekly, for up to 48 weeks.
Viltolarsen	Viltolarsen	Patients amenable to exon 53 skipping will receive viltolarsen intravenous (IV) infusions, weekly, at 80 mg/kg for up to 48 weeks.

Primary Outcome Measures

Name	Time	Method
Change From Baseline in Time to Stand (TTSTAND) Velocity	baseline, Week 13, 25, 37, 49	The change from baseline for velocity converted from TTSTAND was compared between the viltolarsen-treated patients and the placebo-treated patients. TTSTAND was assessed as the time it takes the participant to go from lying flat on the floor to standing. The time measured for TTSTAND was converted to a velocity expressed as rise per second.

Secondary Outcome Measures

Name	Time	Method

Locations (40): University of California Davis Medical Center
🇺🇸
Sacramento, California, United States
Ann and Robert H. Lurie Children's Hospital of Chicago
🇺🇸
Chicago, Illinois, United States
Queensland Children's Hospital
🇦🇺
Brisbane, Australia
Perth Children's Hospital
🇦🇺
Nedlands, Australia
The Childrens Hospital at Westmead
🇦🇺
Westmead, Australia
The Hospital for Sick Children (SickKids)
🇨🇦
Toronto, Ontario, Canada
Alberta Children's Hospital
🇨🇦
Calgary, Canada
CHU de Quebec Research Centre
🇨🇦
Quebec City, Canada
Hospital de Niños Roberto del Rio
🇨🇱
Santiago, Chile
Pontificia Universidad Católica de Chile
🇨🇱
Santiago, Chile
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University of California Davis Medical Center
🇺🇸Sacramento, California, United States