Why Is Neuromuscular-Focused Dyne Therapeutics Stock Trading Lower On Friday?

On Friday, Dyne Therapeutics, Inc. DYN revealed new data from its ongoing Phase 1/2 ACHIEVE trial of DYNE-101 in patients with myotonic dystrophy type 1 (DM1).

Dyne plans to begin a global Registrational Expansion Cohort with the potential to support a submission for U.S. Accelerated Approval based on biomarker and functional data in H1 2026.

Also Read: Muscle Disease Drug Developer Dyne Therapeutics Stock Plunges After Updated Data From Duchenne Muscular Dystrophy

Dyne reported efficacy data from adult DM1 patients enrolled in the randomized, placebo-controlled MAD portion of the DYNE-101 ACHIEVE trial, including data from the 6.8 mg/kg Q8W cohort (n=8) at up to 6 months.

At the 6.8 mg/kg Q8W dose, DYNE-101 resulted in significant splicing correction at 3 months compared to baseline, which was associated with progress in multiple functional endpoints, beginning at 3 months and continuing at 6 months.

• Analysis of muscle biopsy data for the 6.8 mg/kg Q8W cohort showed a substantial knockdown of Drug Metabolism and Pharmacokinetics (DMPK) (DYNE-101 molecular target) RNA levels. Splicing correction at 3 months for the 6.8 mg/kg Q8W cohort was robust. It was associated with improvement in multiple functional endpoints, supporting CASI-22 at 3 months as a surrogate endpoint for potential U.S. Accelerated Approval.
• Early and sustained improvement in myotonia as measured by video hand opening time (vHOT) was seen in the 6.8 mg/kg Q8W cohort and at low doses with modest splicing correction, deepening with more time on the drug.
• Functional measures showed early and sustained clinical benefit at the 6.8 mg/kg Q8W dose.

Dyne also reported safety and tolerability data from 56 patients. Most of the treatment-emergent adverse events were mild or moderate, and no related serious treatment-emergent adverse events have been identified.

Based on previous dialogue with the FDA’s Center for Drug Evaluation and Research division, Dyne continues to pursue accelerated approval in the U.S. based on splicing as a surrogate endpoint.

Dyne anticipates completing enrollment in the Registrational Expansion Cohort in mid-2025 and submitting for U.S. Accelerated Approval in H1 2026.

Price Action: DYN stock is down 35.3% at $14.91 at last check Friday.

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