A Phase III clinical trial at The Neuro (Montreal Neurological Institute-Hospital) is evaluating a drug with the potential to alter the course of myotonic dystrophy type 1 (DM1) by targeting its genetic underpinnings, rather than merely alleviating symptoms. This is particularly significant for the Saguenay–Lac-Saint-Jean region of Quebec, which has the world's highest concentration of DM1, affecting one in 500 people.
Dr. Erin O’Ferrall, a neurologist and principal investigator for neuromuscular trials at The Neuro, emphasized the importance of this research, stating, “This is the first time we could have a treatment that specifically targets the genetic problem at the heart of myotonic dystrophy type 1.”
Understanding Myotonic Dystrophy Type 1
Myotonic dystrophy is an inherited, multi-system disease characterized by progressive muscle atrophy and weakness, as well as myotonia (difficulty relaxing muscles). It can affect various systems, leading to thyroid issues, insulin resistance or diabetes, cardiac arrhythmias, cataracts, fertility problems, and intellectual disabilities. The condition is dominant, meaning a single copy of the mutated gene is sufficient to cause the disorder, with symptoms often worsening across generations. Globally, it affects approximately one in 8,000 individuals.
"It varies greatly from person to person, but can be seriously disabling," said O’Ferrall. "Patients may have difficulty walking and eventually feeding or bathing themselves. They may have speech impediments, which makes communication difficult. They can have difficulty swallowing, which can lead to choking, lung infections or weight loss."
Targeting the Root Cause
In DM1, an accumulation of excessively large messenger RNA (mRNA) occurs within cells, which cannot be effectively eliminated. This accumulation contributes to the progressive worsening of symptoms. The investigational drug uses small-interfering RNA, combined with an antibody to facilitate cell penetration, to interrupt the detrimental effects of the faulty mRNA and remove existing accumulations of defective RNA.
"Until recently, we had nothing that could improve your swallowing or relieve your breathing difficulties or cardiac arrhythmias – we couldn’t fix these things," said O’Ferrall.
Trial Design and Next Steps
The Phase III trial is a randomized, placebo-controlled study across 40 international sites, with The Neuro’s CRU being one of three participating centers in Canada. Participants are assigned to receive either a placebo or the investigational treatment. Following the study, all participants will have the option for early access to the investigational treatment. Additional trials are planned to open in 2025.
O’Ferrall encourages patients who may have lost contact with their specialists to reconnect, stating, “Many patients have disconnected from their specialist because for years we had nothing to offer them. I encourage them to get back in touch with their neurologist because several potential treatments are on the horizon.”
