Novel Hope for Myotonic Dystrophy Type 1: Antibody-Oligonucleotide Conjugate Shows Promise

A groundbreaking new treatment for myotonic dystrophy type 1 (DM1), an often fatal neuromuscular disease, is on the horizon. Final results from the Phase 1/2 MARINA® trial of delpacibart etedesiran (del-desiran) have been published in the February 19, 2026, issue of The New England Journal of Medicine.

Understanding Myotonic Dystrophy Type 1

DM1 is a progressive and underrecognized neuromuscular disease with limited treatment options. The disease is caused by the accumulation of toxic myotonic dystrophy protein kinase (DMPK) mRNA. This buildup sequesters RNA-regulatory proteins, leading to missplicing of genes and a wide range of clinical symptoms.

How Del-Desiran Works

Del-desiran is an investigational Antibody Oligonucleotide Conjugate (AOC™) designed to address the root cause of DM1 by reducing levels of the toxic DMPK mRNA. AOCs represent a new class of RNA therapeutics developed by Avidity Biosciences, Inc. (Nasdaq: RNA).

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 demonstrate:

• Approximately a 40% indicate reduction in DMPK mRNA levels.
• Amelioration of missplicing.
• Improvements in myotonia (muscle stiffness), muscle function, and strength.
• Enhanced mobility.
• Positive changes in patient-reported outcomes.
• Del-desiran demonstrated acceptable safety and tolerability, with most adverse events being mild or moderate.

What This Means for Patients

These findings offer a significant step forward for individuals living with DM1, a disease with no currently approved disease-modifying therapies. By targeting the underlying genetic cause, del-desiran has the potential to slow disease progression and improve the quality of life for patients.

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 clinical trials will be necessary to confirm these findings and determine the long-term efficacy and safety of this promising new treatment.