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# Dyne Therapeutics' Mid-Stage DM1 Trial Shows Broad One-Year Gains Across Strength, Function, And Patient-Reported Outcomes
- URL: https://www.bullished.co/dyne-therapeutics-mid-stage-dm1-trial-shows-broad-one-year-gains-across-strength-function-07ee160f/
- Published: 2026-10-02T16:31:32.000Z
- Updated: 2026-10-03T20:38:54.000Z
- Description: Z-basivarsen cut hand-opening time by 3.2 seconds at six months and diverged from a natural history control group at 12 months across four measures.
- Author: Matteo Parrino
- Tags: SEC Filings, DYN, Industry: Healthcare

Dyne Therapeutics released one-year data Tuesday from its mid-stage ACHIEVE trial of z-basivarsen for myotonic dystrophy type 1 — a rare progressive neuromuscular disease with no approved disease-modifying treatment — showing improvements in myotonia, muscle strength, motor function, and patient-reported disease burden versus both placebo and a matched natural history control group, according to an [8-K filed](https://www.sec.gov/Archives/edgar/data/0001818794/000181879426000009/dyn-20260929.htm?ref=bullished.co) with the SEC. The data were presented at two medical conferences on the same day the filing was made.

## What The Trial Data Show

The results come from a pooled group of 25 to 26 participants drawn from three dosing cohorts in the multiple ascending dose portion of ACHIEVE. At six months, that group showed a mean 3.2-second decrease in hand-opening time — measured by a video test the company calls vHOT — from a baseline of 8.2 seconds. The placebo group, by contrast, saw hand-opening time increase by 0.4 seconds over the same period, putting the relative difference between the two groups at 3.6 seconds, according to the [press release](https://www.sec.gov/Archives/edgar/data/0001818794/000181879426000009/dyn-ex99%5F1.htm?ref=bullished.co).

The six-month vHOT change is also the primary endpoint for the separate registrational expansion cohort — the 71-participant group whose topline data will determine whether Dyne can file for U.S. Accelerated Approval.

At 12 months, the pooled group improved on muscle strength by 4.8% on both the quantitative muscle testing total score and the hand grip score, and improved on the Myotonic Dystrophy Health Index — a patient-reported measure — by 25.2% relative to baseline. Both measures diverged from a matched natural history cohort drawn from the ongoing END-DM1 study, the [filing states](https://www.sec.gov/Archives/edgar/data/0001818794/000181879426000009/dyn-ex99%5F1.htm?ref=bullished.co).

On motor function, the pooled group improved by [1.2 seconds](https://sg.finance.yahoo.com/news/dyne-therapeutics-stock-rises-positive-212300568.html?ref=bullished.co) on the five-times sit-to-stand test and by 0.3 seconds on the 10-meter walk/run test at 12 months versus baseline. The 10-meter walk/run result diverged from the matched natural history cohort; the five-times sit-to-stand test could not be compared because it was not included in the END-DM1 natural history study.

The patient-reported outcome improvement covered six subscales measuring central nervous system disease manifestations: cognitive impairment, sleep disturbances, fatigue, communication, emotional issues, and pain. That comparison was made against an unmatched END-DM1 cohort of 410 participants.

Dyne also disclosed that z-basivarsen continued to show a favorable safety profile through an April 20, 2026 data cutoff, with no related serious treatment-emergent adverse events identified.

## The Natural History Comparison — And Its Limits

Tuesday's release marked the first time Dyne compared its trial results against a propensity-matched cohort from the END-DM1 natural history study. Doug Kerr, M.D., Ph.D., chief medical officer of Dyne, said the new data "further support our confidence in the results we have previously presented from smaller individual dose cohorts" and that the company was, "for the first time," showing functional improvement "compared to a matched natural history cohort."

The company flagged a key caveat in the 8-K: the pooled dose group mixes different dose levels and does not reflect the effect of staying on the registrational dose — [6.8 mg/kg](https://www.globenewswire.com/news-release/2026/09/29/3371326/0/en/dyne-therapeutics-announces-additional-one-year-clinical-data-from-phase-1-2-achieve-trial-of-z-basivarsen-dyne-101-for-myotonic-dystrophy-type-1-dm1.html?ref=bullished.co) every eight weeks — for the full treatment period. Only 8 of the 26 participants in the pooled group received that dose for the entire 12 months analyzed, and most did not receive it at all during the period.

## The Registrational Cohort And What Comes Next

The 71-participant registrational expansion cohort is now fully enrolled. Its mean baseline hand-opening time is [8.3 seconds](https://sg.finance.yahoo.com/news/dyne-therapeutics-stock-rises-positive-212300568.html?ref=bullished.co) — nearly identical to the 8.2-second baseline in the pooled group that generated Tuesday's results. Those baseline data remain blinded to treatment assignment.

Dyne expects topline data from the registrational cohort in the first quarter of 2027, which it plans to use to support a potential Biologics License Application for U.S. Accelerated Approval in the third quarter of 2027\. A separate late-stage confirmatory trial, called HARMONIA, is currently enrolling at [more than 35](https://www.globenewswire.com/news-release/2026/09/29/3371326/0/en/dyne-therapeutics-announces-additional-one-year-clinical-data-from-phase-1-2-achieve-trial-of-z-basivarsen-dyne-101-for-myotonic-dystrophy-type-1-dm1.html?ref=bullished.co) sites globally; its primary endpoint is the five-times sit-to-stand test at 12 months.

Myotonic dystrophy type 1 affects roughly 40,000 people in the U.S. and about 55,000 in the EU. The disease causes progressive muscle weakness, difficulty relaxing muscles, fatigue, cognitive impairment, and cardiac complications. Z-basivarsen is designed to correct the underlying RNA splicing defect that drives the disease by delivering a targeted payload to both muscle and the central nervous system. The drug holds Breakthrough Therapy, Orphan Drug, and Fast Track designations from the FDA, as well as Orphan Drug designation from the European Medicines Agency and Japan's health ministry.

DYN shares fell about 2% to $15.45 in Friday trading, after the stock had gained about 2% in after-hours trading on Tuesday when the data were released, according to market data.

The next major readout for Dyne is topline data from the 71-participant registrational expansion cohort, expected in the first quarter of 2027 — the result that will determine whether the company files for U.S. Accelerated Approval by the third quarter of that year.

### Sources

- [8-K Filing — Dyne Therapeutics, Inc. (DYN)](https://www.sec.gov/Archives/edgar/data/0001818794/000181879426000009/dyn-20260929.htm?ref=bullished.co) — SEC EDGAR
- [Exhibit dyn-ex99\_1.htm — Dyne Therapeutics, Inc. 8-K exhibit](https://www.sec.gov/Archives/edgar/data/0001818794/000181879426000009/dyn-ex99%5F1.htm?ref=bullished.co) — SEC EDGAR
- [Exhibit dyn-ex99\_2.htm — Dyne Therapeutics, Inc. 8-K exhibit](https://www.sec.gov/Archives/edgar/data/0001818794/000181879426000009/dyn-ex99%5F2.htm?ref=bullished.co) — SEC EDGAR
- [Dyne Therapeutics stock rises on positive DM1 trial results](https://sg.finance.yahoo.com/news/dyne-therapeutics-stock-rises-positive-212300568.html?ref=bullished.co) — sg.finance.yahoo.com
- [Dyne Therapeutics Announces Additional One-Year Clinical](https://www.globenewswire.com/news-release/2026/09/29/3371326/0/en/dyne-therapeutics-announces-additional-one-year-clinical-data-from-phase-1-2-achieve-trial-of-z-basivarsen-dyne-101-for-myotonic-dystrophy-type-1-dm1.html?ref=bullished.co) — globenewswire.com