Avidity’s Breakthrough in Myotonic Dystrophy Type 1: A New Era of RNA Therapeutics?
San Diego, CA – February 18, 2026 – Avidity Biosciences announced today that final results from the Phase 1/2 MARINA® trial of del-desiran, an investigational treatment for myotonic dystrophy type 1 (DM1), will be published in the February 19 issue of The New England Journal of Medicine. This milestone signals a potential turning point in the treatment of this progressive and often fatal neuromuscular disease, for which there are currently no disease-modifying therapies.
Understanding the Science: Targeting the Root Cause of DM1
DM1 is caused by a genetic defect – a triplet-repeat in the DMPK gene – leading to the production of toxic mRNA. This toxic mRNA sequesters key RNA-regulatory proteins, disrupting gene splicing and causing a wide range of symptoms. Del-desiran is designed to address this underlying genetic cause by reducing levels of the harmful DMPK mRNA.
Promising Results from the MARINA Trial
The Phase 1/2 MARINA trial, a randomized, double-blind, placebo-controlled study, demonstrated several key findings. Del-desiran effectively delivered siRNA to muscle tissue, resulting in approximately a 40% mean reduction in DMPK mRNA across all treated participants. Improvements were observed in multiple measures, including myotonia (muscle stiffness), muscle function and strength, mobility and patient-reported outcomes. The treatment also showed acceptable safety and tolerability, with most adverse events being mild or moderate.
“These final results from the MARINA study further reinforce data reported thus far showing acceptable safety profile and improvements across a range of key functional assessments including myotonia, a hallmark symptom of DM1,” said Nicholas E. Johnson, M.D., M.Sci., FAAN, professor and vice chair of research in the Department of Neurology at Virginia Commonwealth University, and lead investigator of the trial.
Antibody Oligonucleotide Conjugates (AOCs™): A Novel Approach
Avidity Biosciences’ success with del-desiran hinges on its proprietary AOC platform. AOCs combine the specificity of monoclonal antibodies with the precision of oligonucleotide therapies. This allows for targeted delivery of RNA therapeutics to specific tissues, overcoming a major hurdle in the field of RNA-based drug development. This targeted approach is a significant advancement over traditional RNA therapies.
Novartis’ $12 Billion Bet on Neuroscience and Dystrophy
The potential of AOC technology and del-desiran specifically has not gone unnoticed by major pharmaceutical players. In a recent move, Novartis acquired Avidity for $12 billion, bolstering its neuroscience pipeline. Novartis CEO Vasant Narasimhan even suggested the deal could have been “twice as big,” underscoring the perceived value of Avidity’s platform and DM1 program.
Looking Ahead: Phase 3 Trials and Beyond
Del-desiran (4 mg/kg) is currently being assessed in the global Phase 3 HARBOR™ study, which completed enrollment in July 2025. Topline data from this pivotal trial are expected in the second half of 2026. The HARBOR study is designed to evaluate del-desiran in a larger patient population and confirm the findings from the Phase 1/2 trial. All participants from the MARINA trial have the option to enroll in the ongoing HARBOR open-label extension (HARBOR-OLE™) trial.
The Broader Implications for RNA Therapeutics
Avidity’s progress with del-desiran and the AOC platform has broader implications for the field of RNA therapeutics. The success of targeted RNA delivery could unlock new treatment options for a wide range of genetic diseases. Other companies are also pursuing innovative approaches to RNA delivery, but Avidity’s AOC technology appears to be a frontrunner.
Frequently Asked Questions (FAQ)
What is Myotonic Dystrophy Type 1 (DM1)? DM1 is a rare, hereditary neuromuscular disease that causes muscle stiffness, weakness, and a variety of other symptoms.
What are Antibody Oligonucleotide Conjugates (AOCs™)? AOCs are a novel class of RNA therapeutics that combine the specificity of antibodies with the precision of oligonucleotides for targeted drug delivery.
What is the status of the HARBOR™ trial? The Phase 3 HARBOR™ trial is currently underway and expected to deliver topline data in the second half of 2026.
Is del-desiran safe? The Phase 1/2 MARINA trial showed that del-desiran was generally well-tolerated, with most adverse events being mild or moderate.
Pro Tip
Stay informed about clinical trial results and new drug approvals by regularly checking the websites of the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA).
Investor Contact: Kat Lange, (619) 837-5014, [email protected]
Media Contact: Kristina Coppola, (619) 837-5016, [email protected]
Learn more about DM1 and ongoing research at http://www.clinicaltrials.gov.
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