Dyne Therapeutics Reports 1-Year ACHIEVE Trial Data for z‑basivarsen

What Happened
On September 29, 2026, Dyne Therapeutics announced additional one‑year clinical data from the multiple ascending dose (MAD) portion of its Phase 1/2 ACHIEVE trial evaluating z‑basivarsen (DYNE‑101) in myotonic dystrophy type 1 (DM1). The announcement reports results from a pooled dose group (N = 25–26) that combined participants from the 3.4 mg/kg Q4W, 5.4 mg/kg Q8W and 6.8 mg/kg Q8W cohorts (including participants originally on placebo who were re‑baselined). Key efficacy signals vs baseline include a mean baseline video hand‑opening time (vHOT) of 8.2 seconds that decreased by 3.2 seconds at 6 months (SD of change 3.5 s); placebo increased by 0.4 s at 6 months (placebo N=14), a 3.6 s relative improvement. The company also provided a blinded mean baseline vHOT of 8.3 s (SD 6.0) for the 71 participants enrolled in the ACHIEVE registrational expansion cohort (REC). Topline REC data are expected in Q1 2027 and could support a potential BLA submission for U.S. Accelerated Approval in Q3 2027. Updated safety data (through April 20, 2026) showed a favorable profile with no related serious treatment‑emergent adverse events identified.

Key Details

• Pooled dose group: N = 25–26 from MAD cohorts (3.4 mg/kg Q4W, 5.4 mg/kg Q8W, 6.8 mg/kg Q8W); only 8 of 26 received the 6.8 mg/kg registrational dose for the full 12 months analyzed.
• Myotonia (vHOT): mean baseline 8.2 s → decrease of 3.2 s at 6 months (SD change 3.5 s); placebo increased 0.4 s at 6 months (placebo N=14); change from baseline in vHOT at 6 months is the REC primary endpoint.
• Function & strength at 12 months: 5xSTS improved by 1.2 s and 10MWR improved by 0.3 s vs baseline (divergence vs matched natural history on 10MWR); QMT total and hand‑grip each improved by 4.8% predicted vs baseline.
• Patient‑reported outcomes: MDHI total score improved 25.2% at 12 months vs baseline (compared to an unmatched END‑DM1 natural history cohort, N=410).
• Safety: Updated through April 20, 2026 — z‑basivarsen continued to show a favorable safety profile with no related serious TEAEs identified.

Why It Matters
These data show sustained improvements from baseline in myotonia (vHOT), function (5xSTS, 10MWR), muscle strength (QMT) and patient‑reported symptoms (MDHI) in the pooled MAD group and signal divergence versus natural history cohorts on several measures. For investors, the timing and content matter because topline REC results (vHOT primary endpoint) expected in Q1 2027 could enable a potential BLA submission for U.S. Accelerated Approval in Q3 2027; the ongoing HARMONIA Phase 3 trial uses 5xSTS as its confirmatory endpoint for traditional approval. Note the pooled group includes mixed dose exposures and most participants did not maintain the registrational dose for the full 12 months, which the company states can limit interpretation of the results.