Fresh Treatment Shows Promise for Myotonic Dystrophy Type 1

A novel antibody oligonucleotide conjugate, delpacibart etedesiran (del-desiran), has demonstrated significant improvements in individuals with myotonic dystrophy type 1 (DM1), according to final results from the Phase 1/2 MARINA® trial published in The New England Journal of Medicine on February 19, 2026. This marks a potential turning point in the treatment of DM1, a progressive and often fatal neuromuscular disease with limited therapeutic options.

Understanding Myotonic Dystrophy Type 1

DM1 is a genetic disorder caused by an expansion of a CTG repeat in the DMPK gene. This leads to the production of toxic RNA that accumulates in muscle cells, disrupting normal gene expression and causing a range of symptoms, including myotonia (muscle stiffness), muscle weakness, and various systemic complications.

How Del-Desiran Works

Del-desiran is designed to address the root cause of DM1 by reducing the levels of toxic DMPK mRNA. It utilizes Antibody Oligonucleotide Conjugate (AOC) technology to deliver small interfering RNA (siRNA) directly to muscle cells, where it degrades the harmful mRNA. This reduction in toxic mRNA aims to restore normal RNA processing and alleviate disease symptoms.

Key Findings from the MARINA® Trial

The Phase 1/2 MARINA trial involved 38 participants with DM1 who were randomized to receive either del-desiran or a placebo. Key results include:

• mRNA Reduction: Del-desiran effectively reduced DMPK mRNA levels by approximately 40% on average.
• Improved Symptoms: Participants receiving del-desiran showed improvements in myotonia, muscle function, strength, mobility, and patient-reported outcomes.
• Safety and Tolerability: The treatment demonstrated acceptable safety and tolerability, with most adverse events being mild or moderate.

What’s Next?

The publication of these results in The New England Journal of Medicine represents a significant step forward in the development of therapies for DM1. Further research and clinical trials will be necessary to confirm these findings and evaluate the long-term efficacy and safety of del-desiran. Avidity Biosciences, Inc. (Nasdaq: RNA) continues to advance the development of this promising treatment.