FDA Grants Breakthrough Therapy Designation to Delpacibart Etedesiran for Myotonic Dystrophy Type 1

Delpacibart etedesiran (del-desiran/AOC 1001; Avidity Biosciences, San Diego, CA) has been granted Breakthrough Therapy designation by the Food and Drug Administration (FDA) as an investigational treatment for myotonic dystrophy type 1 (DM1). Delpacibart etedesiran was previously granted Orphan Drug Designation and Fast Track designation by the FDA, and it was shown to reverse disease progression in results of the MARINA-OLE clinical trial (NCT05479981) presented at the 2024 Muscular Dystrophy Association (MDA) Clinical and Scientific Conference.

Delpacibart etedesiran is the lead clinical development program of Avidity Biosciences, a monoclonal antibody (mAb) agent designed to reduce levels of DMPK, a disease-related mRNA. According to a statement from Avidity Biosciences, the company plans to initiate the HARBOR clinical trial (NCT06411288) in 2024. HARBOR is a phase 3 that will assess video hand opening time (vHOT) as a primary endpoint in individuals who have a clinical or genetic diagnosis of DM1, with secondary endpoints assessing quantitative muscle testing (QMT) total score, hand grip strength, and activities of daily living as measured according to the myotonic dystrophy type 1 activity and participation scale (DM1-Activ).

“We are pleased that the FDA has granted Breakthrough Therapy designation to del-desiran for myotonic dystrophy type 1, underscoring the potential of del-desiran to be an effective treatment and the urgency of bringing this treatment to people living with DM1," said Sarah Boyce, President and CEO of Avidity Biosciences. “Initiation is underway for our global Phase 3 HARBOR study as we focus on rapidly advancing del-desiran for people living with DM1, who currently have no treatment options to address the underlying cause of this devastating rare muscle disease.”