Dyne Therapeutics, Inc. announced that the U.S. Food and Drug Administration (FDA) has placed on clinical hold its Investigational New Drug (IND) application to initiate a clinical trial of DYNE-251 in patients with Duchenne muscular dystrophy (DMD) amenable to skipping exon 51. Dyne received a clinical hold letter from the FDA on January 14, 2022 requesting additional clinical and non-clinical information for DYNE-251. The Company expects to submit to the FDA its response with data from existing and ongoing studies in the second quarter of 2022, and if satisfactory to the FDA, to be dosing patients in a Phase 1/2 multiple ascending dose (MAD) clinical trial of DYNE-251 by mid-2022 in accordance with its current guidance.

Dyne will work closely with the FDA to resolve the clinical hold as promptly as possible. As previously announced, the Company expects to submit an IND for DYNE-101 in myotonic dystrophy type 1 (DM1) during the first quarter of 2022 and to be dosing patients in a planned MAD clinical trial by mid-2022.