Overview
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 multiple-ascending dose (MAD) Placebo-Controlled Period (24 weeks), a Treatment Period (24 weeks) and a Long-Term Extension (LTE) Period (96 weeks).
Eligibility
Inclusion Criteria:
- 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.
- Able to complete 10-MWRT, stair ascend/descend, and 5×STS at screening without the use of assistive devices such as canes, walkers, or orthoses.
Exclusion Criteria:
- 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.
- Electrocardiogram (ECG) with the corrected QT interval by Fridericia's Formula (QTcF) ≥450 milliseconds (ms) in men and QTcF ≥460 ms in women, PR ≥240 ms, left bundle-branch block, or a conduction defect, which is clinically significant in the opinion of the Investigator.
- Percent predicted forced vital capacity (FVC) <50%.
- History of tibialis anterior biopsy within 3 months of Day 1 or planning to undergo tibialis anterior biopsies during study period for reasons unrelated to the study.
Note: Other inclusion and exclusion criteria may apply.