Dyne Therapeutics Announces FDA Breakthrough Therapy Designation for DYNE-101 and Updated Plan for Accelerated Approval in DM1 Following Type C Meeting

Core Viewpoint - Dyne Therapeutics has received Breakthrough Therapy Designation from the FDA for DYNE-101, aimed at treating myotonic dystrophy type 1 (DM1), and has outlined a revised plan for U.S. Accelerated Approval based on new long-term functional data [1][2][10]. Group 1: FDA Designations and Approvals - The FDA granted Breakthrough Therapy Designation to DYNE-101 for DM1, which expedites development and review for drugs showing substantial improvement over existing therapies [10]. - Dyne is pursuing U.S. Accelerated Approval for DYNE-101, with a revised protocol submitted to the FDA following a Type C meeting [6][5]. Group 2: Clinical Trial Updates - The ongoing Registrational Expansion Cohort of the ACHIEVE trial will enroll 60 participants, with video hand opening time (vHOT) as the primary endpoint for potential Accelerated Approval [6][5]. - New long-term data from the ACHIEVE trial indicate that DYNE-101 led to a 3.3 seconds improvement in vHOT at 6 months compared to placebo, with sustained improvements observed at 12 months [12]. - The trial's secondary endpoints include various measures of muscle strength and performance, with a reported 20% improvement in strength at 12 months relative to baseline [12]. Group 3: Financial Guidance - As of March 31, 2025, Dyne reported cash, cash equivalents, and marketable securities totaling $677.5 million, expected to fund operations into Q4 2026 [7]. Group 4: Future Plans - Dyne plans to complete enrollment in the Registrational Expansion Cohort by Q4 2025, with data expected in mid-2026 to support a potential U.S. Accelerated Approval submission in late 2026 [6]. - A confirmatory Phase 3 clinical trial is anticipated to begin in Q1 2026 [6].