WALTHAM, Mass. — September 29, 2026

Dyne Therapeutics reported additional one-year clinical data from the multiple ascending dose (MAD) portion of its Phase 1/2 ACHIEVE trial evaluating zeleciment basivarsen (z-basivarsen, DYNE-101) in myotonic dystrophy type 1 (DM1). A pooled group of 25–26 participants showed improvements from baseline across multiple functional, strength and patient-reported measures at 12 months, with comparisons also favoring treatment over a matched natural-history cohort on selected measures. The findings are being presented at the 31st Annual International Congress of the World Muscle Society and the 2026 AANEM Annual Meeting. Dyne continues to expect topline data from the ACHIEVE registrational expansion cohort (REC) in Q1 2027, with a potential U.S. Accelerated Approval submission planned for Q3 2027.

ACHIEVE Data Show Improvements Across Measures

The pooled analysis included participants from three dose cohorts in the ACHIEVE MAD study, including 3.4 mg/kg every four weeks, 5.4 mg/kg every eight weeks and 6.8 mg/kg every eight weeks. At 12 months, participants showed improvements from baseline in the five-times sit-to-stand test, 10-meter walk/run test, quantitative muscle testing and the Myotonic Dystrophy Health Index. The group’s mean video hand opening time (vHOT), a measure of myotonia, improved by 3.2 seconds at six months from a baseline of 8.2 seconds, compared with a 0.4-second worsening in the ACHIEVE placebo group. The analysis included mixed dose exposures; only 8 of 26 participants received the registrational dose for the full 12-month period, limiting conclusions about outcomes specifically attributable to continuous treatment at that dose.

Functional and Patient-Reported Outcomes

At 12 months, the pooled group improved by 1.2 seconds on the five-times sit-to-stand test and 0.3 seconds on the 10-meter walk/run test relative to baseline. Quantitative muscle testing total and hand-grip scores each improved by 4.8% predicted, while the Myotonic Dystrophy Health Index total score improved by 25.2%. Dyne reported divergence from a propensity-matched natural-history cohort on 10-meter walk/run and strength measures, and from an unmatched natural-history cohort on the patient-reported outcome measure. These comparisons are supportive but have limitations: the pooled analysis was not a randomized comparison at a single dose, the natural-history groups were not identical across measures, and the five-times sit-to-stand test was not included in the END-DM1 natural-history study.

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Dyne Prepares for Registrational Readouts

Z-basivarsen is an investigational antisense oligonucleotide designed to reduce toxic DMPK RNA and address the underlying RNA-splicing abnormalities associated with DM1. The therapy uses a transferrin receptor 1-binding Fab to support delivery to muscle and the central nervous system. The ACHIEVE REC is fully enrolled, with 71 participants and a mean baseline vHOT of 8.3 seconds; its primary endpoint is change in vHOT at six months versus placebo. Dyne is also recruiting participants at more than 35 global sites in the Phase 3 HARMONIA trial, which uses change in the five-times sit-to-stand test at 12 months as its primary endpoint. Z-basivarsen has received FDA Breakthrough Therapy, Fast Track and Orphan Drug designations, but remains investigational, and its efficacy and safety will require confirmation in the registrational studies.

Source :Dyne Therapeutics press release