SAN DIEGO, Calif. — Avidity Biosciences, Inc. (Nasdaq: RNA), a biopharmaceutical company committed to delivering a new class of RNA therapeutics called Antibody Oligonucleotide Conjugates (AOCs™), today announced the completion of enrollment in the ongoing global Phase 3 HARBOR™ clinical trial of delpacibart etedesiran (del-desiran) for people living with myotonic dystrophy type 1 (DM1). Topline data from HARBOR, the first global Phase 3 clinical trial in DM1, are anticipated in the second quarter of 2026.
Prior to initiation of the HARBOR trial, Avidity aligned with global regulators, including FDA, on the registrational path for del-desiran. The Company plans to submit marketing applications beginning in the second half of 2026 including in the United States, European Union and Japan.
“Completing enrollment in our Phase 3 HARBOR study for del-desiran marks a significant step toward bringing the first potentially approved drug for DM1 to people around the world who are living with this devastating rare neuromuscular disease,” said Steve Hughes, M.D., chief medical officer at Avidity. “The growing body of data from clinical studies to date support the promise of del-desiran, including durable improvements in multiple clinical endpoints compared to natural history data and evidence that del-desiran is addressing the underlying genetic cause of disease progression. These encouraging results suggest that this potential therapy may be transformational for patients who urgently need treatment options. We extend our deepest appreciation to the DM1 community for their ongoing support of our research and development program, especially the patients, families, global advocacy groups, healthcare providers and staff who are part of the HARBOR and MARINA-OLE™ studies.”
Del-desiran is an investigational treatment designed to address the underlying genetic cause of DM1, a rare, hereditary, progressive neuromuscular disease that shortens life expectancy and requires life-long care. DM1 is characterized by multisystemic manifestations including myotonia and progressive muscle weakening and may be underrecognized because it presents heterogeneously across skeletal, cardiac, and smooth muscles, leading to impairment of the cardiovascular, gastrointestinal, respiratory, ocular, and/or endocrine systems. Currently, there are no approved drugs for people living with DM1.
Del-desiran has received Breakthrough Therapy, Orphan Drug and Fast Track designations by the U.S. Food and Drug Administration (FDA) and Orphan designation by the European Medicines Agency (EMA). Del-desiran was also the first investigational treatment for DM1 to receive Orphan Drug designation in Japan.
About the Phase 3 HARBOR™ Trial
The global Phase 3 HARBOR™ trial is a randomized, placebo-controlled, double blind pivotal study designed to evaluate del-desiran in approximately 150 people (age 16 and older) living with DM1. The trial is being conducted at approximately 40 sites globally. Patients are administered either del-desiran or placebo (1:1) every eight weeks. HARBOR is designed to assess multiple key functional aspects of DM1. The primary endpoint is video hand opening time (vHOT), a measurement of myotonia, which is a hallmark symptom of DM1. Key secondary endpoints include muscle strength as measured by hand grip strength and quantitative muscle testing (QMT) total score, and activities of daily living as measured by DM1-Activ. All study participants, regardless of whether they receive active treatment or placebo, have the option to enroll into an open-label extension trial that is expected to begin in Q3 2025. For more information about the HARBOR trial, visit the HARBOR study website or visit http://www.
About Myotonic Dystrophy Type 1
Myotonic dystrophy type 1 (DM1) is a rare, hereditary (autosomal dominant), progressive neuromuscular disease that shortens life expectancy and requires life-long care caused by a triplet-repeat in the DMPK gene, resulting in a toxic gain of function mRNA. The disease is highly variable with respect to severity, presentation and age of onset, however, all forms of DM1 are associated with high levels of disease burden. DM1 is characterized by multisystemic manifestations including myotonia and progressive muscle weakening and may be underrecognized because it presents heterogeneously across skeletal, cardiac, and smooth muscles, leading to impairment of the cardiovascular, gastrointestinal, respiratory, ocular, and/or endocrine systems. Currently, there are no approved drugs for people living with DM1.
About del-desiran
Del-desiran, utilizing Avidity’s AOC platform technology, is designed to address the genetic cause of DM1 by reducing levels of toxic DMPK mRNA. Del-desiran consists of a proprietary monoclonal antibody that binds to transferrin receptor 1 (TfR1) and is conjugated to a siRNA that targets DMPK mRNA. Del-desiran is currently being assessed in the global Phase 3 HARBOR™ trial and in the ongoing MARINA-OLE™ trial in people with DM1. Long-term data from the MARINA-OLE trial showed reversal of disease progression in people living with DM1 across multiple endpoints including video hand opening time (vHOT) as a measure of hand function and myotonia, muscle strength and activities of daily living when compared to END-DM1 natural history data. Del-desiran has received Breakthrough Therapy, Orphan Drug and Fast Track designations by the U.S. Food and Drug Administration (FDA) and Orphan designation by the European Medicines Agency (EMA). Del-desiran was also the first investigational treatment for DM1 to receive Orphan Drug designation in Japan.
About Avidity
Avidity Biosciences, Inc.’s mission is to profoundly improve people’s lives by delivering a new class of RNA therapeutics – Antibody Oligonucleotide Conjugates (AOCs™). Avidity is revolutionizing the field of RNA with its proprietary AOCs, which are designed to combine the specificity of monoclonal antibodies with the precision of oligonucleotide therapies to address targets and diseases previously unreachable with existing RNA therapies. Utilizing its proprietary AOC platform, Avidity demonstrated the first-ever successful targeted delivery of RNA into muscle and is leading the field with clinical development programs for three rare muscle diseases: myotonic dystrophy type 1 (DM1), Duchenne muscular dystrophy (DMD) and facioscapulohumeral muscular dystrophy (FSHD). Avidity is also advancing two wholly-owned precision cardiology development candidates addressing rare genetic cardiomyopathies. In addition, Avidity is broadening the reach of AOCs with its advancing and expanding pipeline including programs in cardiology and immunology through key partnerships. Avidity is headquartered in San Diego, CA. For more information about our AOC platform, clinical development pipeline and people, please visit www.aviditybiosciences.
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