Modern Hope for Myotonic Dystrophy Type 1: Promising Results Published in NEJM

A new investigational treatment, delpacibart etedesiran (del-desiran), is showing significant promise for individuals living with myotonic dystrophy type 1 (DM1), a progressive and often fatal neuromuscular disease. Final results from the Phase 1/2 MARINA® trial were published in the February 19, 2026, issue of The New England Journal of Medicine [1], offering a potential disease-modifying therapy for a condition with limited treatment options.

Understanding Myotonic Dystrophy Type 1

DM1 is an underrecognized neuromuscular disease characterized by the accumulation of toxic myotonic dystrophy protein kinase (DMPK) mRNA. This buildup disrupts RNA-regulatory proteins, leading to missplicing of genes and a wide range of clinical symptoms. Currently, there are no therapies that address the underlying genetic cause of DM1.

How Del-Desiran Works

Del-desiran is an Antibody Oligonucleotide Conjugate (AOC™) designed to target and reduce levels of the toxic DMPK mRNA. By addressing the root cause of the disease, it aims to alleviate the symptoms and slow the progression of DM1.

Key Findings from the MARINA® Trial

The Phase 1/2 MARINA trial was a randomized, double-blind, placebo-controlled study involving 38 adults with DM1. Participants received either a placebo or varying doses of del-desiran intravenously for six months. The results demonstrated:

• Approximately a 40% mean reduction in DMPK mRNA levels.
• Improvements in several measures, including myotonia (muscle stiffness), muscle function, strength, mobility and patient-reported outcomes.
• Acceptable safety and tolerability, with most adverse events being mild or moderate.

What This Means for Patients

These findings represent a significant step forward in the treatment of DM1. Avidity Biosciences, Inc. (Nasdaq: RNA), the biopharmaceutical company developing del-desiran, believes this treatment could potentially offer a new hope for individuals affected by this debilitating disease. [4]

Looking Ahead

The publication of these results in The New England Journal of Medicine marks a crucial milestone in the development of del-desiran. Further research and potential regulatory approvals will be necessary before this treatment becomes widely available to patients. However, the data from the MARINA® trial provide a strong foundation for optimism in the fight against myotonic dystrophy type 1.