Dyne adjusts regulatory timeline for DYNE-101 after FDA feedback

US biotech Dyne Therapeutics (Nasdaq: DYN) has revised its regulatory approach for DYNE-101, a treatment in development for myotonic dystrophy type 1 (DM1), after discussions with the American medicines regulator.

While the shift in clinical strategy has caused a delay in the company’s accelerated approval timeline, it also comes with an upside — DYNE-101 has been granted breakthrough therapy designation.

The decision follows a Type C meeting between Dyne and the Center for Drug Evaluation and Research. As part of the updated plan, the registrational expansion cohort of the ongoing Phase I/II ACHIEVE study will now use a functional measure — video hand opening time (vHOT) — as its main efficacy endpoint at six months. This replaces the previously used biomarker-focused assessment of splicing changes via the composite alternative splicing index (CASI-22).