The primary purpose of the study is to evaluate the safety and tolerability of multiple intravenous (IV) doses of DYNE-101 administered to participants with Myotonic Dystrophy Type 1 (DM1).
The study consists of 4 periods: A Screening Period (up to 8 weeks), a Placebo-Controlled Period (24 weeks), a Treatment Period (24 weeks) and a Long-Term Extension (LTE) Period (168 weeks) in both multiple-ascending dose (MAD) and dose expansion cohorts.
Diagnosis of DM1 with trinucleotide repeat size >100.
Age of onset of DM1 muscle symptoms ≥12 years.
Clinically apparent myotonia equivalent to hand opening time of at least 2 seconds in the opinion of the Investigator.
Hand grip strength and ankle dorsiflexion strength.
History of major surgical procedure within 12 weeks prior to the start of investigative product administration or an expectation of a major surgical procedure (eg, implantation of cardiac defibrillator) during the study.
History of anaphylaxis.
Medical condition other than DM1 that would significantly impact ambulation or participation in functional assessments.
Treatment with medications that can improve myotonia within a period of 5 half-lives of the medication prior to performing screening assessments.
8
Treatment groupsSee each treatment group below.