Avidity Biosciences Gets FDA Breakthrough Status for Delpacibart Etedesiran in Myotonic Dystrophy Type 1

Avidity Biosciences, Inc., a biopharmaceutical company renowned for its innovative RNA therapeutics called Antibody Oligonucleotide Conjugates (AOCs™), has announced significant developments in the treatment of myotonic dystrophy type 1 (DM1). The U.S. Food and Drug Administration (FDA) has granted Breakthrough Therapy designation to the company’s lead clinical candidate, delpacibart etedesiran (AOC 1001), also known as del-desiran. This investigational treatment aims to address the underlying cause of DM1, a severe neuromuscular disorder for which no approved therapies currently exist.

Sarah Boyce, the president and CEO of Avidity, expressed the company’s enthusiasm about the FDA’s decision. She emphasized the importance of del-desiran as a potential effective treatment for DM1 and the urgency of making this option available to patients afflicted by this debilitating condition.

Avidity is launching its global Phase 3 HARBOR™ study of del-desiran within this quarter. The primary goal of this pivotal trial is to measure video hand opening time (vHOT), with secondary objectives focusing on muscle strength, as assessed by hand grip strength and quantitative muscle testing (QMT) total score, alongside daily living activities measured by DM1-Activ. This follows the positive outcomes reported from the MARINA-OLE™ study, which indicated a reversal of disease progression in DM1 patients across various functional measures, including vHOT, muscle strength, and DM1-Activ, compared to natural disease progression data.

Del-desiran has also received Orphan Drug and Fast Track designations from the FDA and Orphan designation from the European Medicines Agency (EMA), highlighting its potential as a groundbreaking treatment for DM1.

The ongoing MARINA-OLE™ study is an open-label, multi-center trial designed to assess the long-term safety and tolerability of del-desiran in DM1 patients who participated in the MARINA® Phase 1/2 trial. This study continues to evaluate various aspects such as safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and efficacy in participants who receive quarterly doses of del-desiran. The active treatment phase in this trial spans approximately 24 months, followed by a nine-month safety follow-up period, with the possibility of extending the treatment duration.

Del-desiran operates by reducing levels of a disease-related mRNA known as DMPK. It consists of a proprietary monoclonal antibody that binds to the transferrin receptor 1 (TfR1), conjugated with a small interfering RNA (siRNA) targeting DMPK mRNA. Preclinical studies have shown that del-desiran effectively delivers siRNAs to muscle cells, leading to significant, dose-dependent reductions in DMPK RNA across various muscle types.

Myotonic dystrophy type 1 is a progressive, often fatal disorder caused by a genetic mutation in the DMPK gene, resulting in toxic mRNA accumulation. This condition exhibits a wide range of severity and can lead to numerous complications including muscle weakness, respiratory issues, cardiac abnormalities, and cognitive impairments. Currently, no approved treatments exist for DM1.

Avidity Biosciences is dedicated to revolutionizing RNA therapeutics through its proprietary AOCs, combining the specificity of monoclonal antibodies with the precision of oligonucleotide therapies. The company’s pipeline includes treatments for several rare muscle diseases like myotonic dystrophy type 1, Duchenne muscular dystrophy, and facioscapulohumeral muscular dystrophy. Avidity is extending the reach of its AOCs to address conditions in cardiology and immunology through ongoing research and strategic partnerships.

The future of del-desiran and Avidity’s broader AOC platform looks promising, with ongoing efforts to bring these innovative treatments to patients suffering from rare and severe diseases.

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