Novartis Myotonic Dystrophy Trial Flop Sends Dyne Therapeutics Shares Tumbling

Dyne Therapeutics Inc. (NASDAQ:DYN) stock is trading lower on Tuesday in reaction to Novartis AG’s (NYSE:NVS) data from the global Phase 3 HARBOR study of del-desiran for myotonic dystrophy type 1 (DM1).

• Dyne Therapeutics stock is feeling bearish pressure. What’s behind DYN decline?

Competitor Phase 3 Failure Impacts Dyne Therapeutics

The study did not demonstrate statistically significant improvement versus placebo on the primary endpoint of video hand opening time (vHOT), a novel measure of hand myotonia.

Dyne is developing zeleciment basivarsen (z-basivarsen, also known as DYNE-101), an antisense oligonucleotide (ASO) conjugated to an antigen-binding fragment (Fab) that binds to the transferrin receptor 1 (TfR1) to enable delivery to muscle and the central nervous system.

It is designed to deliver functional improvement in DM1 patients.

Upcoming Clinical Data Presentations

On Tuesday, Dyne Therapeutics announced it will present additional one-year clinical data from the Phase 1/2 ACHIEVE trial of z-basivarsen for DM1 at the Annual International Congress of the World Muscle Society, as well as the 2026 Annual Meeting of the American Association of Neuromuscular & Electrodiagnostic Medicine.

These presentations will both include:

• Data at six and 12 months from a pooled dose group (N=25-26), comprised of participants initially enrolled in the 3.4 mg/kg Q4W, 5.4 mg/kg Q8W, and 6.8 mg/kg Q8W cohorts of the multiple ascending dose (MAD) portion of the ACHIEVE trial, including participants originally assigned to placebo in these cohorts.
• Data at 12 months from a cohort of participants (N=41-46) from the ongoing END-DM1 natural history study who were propensity-matched to the ACHIEVE pooled dose group.
• Updated safety data from ACHIEVE MAD participants.

In June, the company completed enrollment in the registrational expansion cohort (REC) of the Phase 1/2 ACHIEVE trial of zeleciment basivarsen for DM1.

Dyne will also provide the average baseline value for vHOT in the REC of the ACHIEVE trial (n=71), which remains blinded to treatment assignment. Topline data from the ACHIEVE REC are planned for the first quarter of 2027.

Phase 3 HARMONIA Trial Progress and Regulatory Alignment

In March, Dyne Therapeutics initiated the Phase 3 HARMONIA trial of z-basivarsen for DM1. The trial will enroll approximately 150 participants age 16 and older.

Dyne has aligned with the U.S. Food and Drug Administration (FDA) on the HARMONIA Phase 3 trial design and protocol.

HARMONIA is intended to serve as a confirmatory trial to support conversion of Accelerated Approval to traditional approval in the U.S. and to support ex-U.S. marketing applications.

DYN Stock Price Activity: Dyne Therapeutics shares were down 14.66% to $20.72 at the time of publication on Tuesday, according to Benzinga Pro data.

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