Safety, Tolerability, Pharmacodynamic, Efficacy, and Pharmacokinetic Study of DYNE-101 in Participants With Myotonic Dystrophy Type 1

To join this study, you must have a confirmed diagnosis of Myotonic Dystrophy Type 1 (DM1) with a specific genetic marker. Your DM1 muscle symptoms must have started when you were 12 years old or older. You also need to be between 18 and 65 years old. The doctors will check your muscle strength, especially in your hands and ankles, and make sure you have noticeable myotonia (muscles finding it hard to relax).

There are also some requirements about your physical abilities. For example, you should be able to walk a certain distance in 10 minutes, climb stairs, and stand up from a chair five times in a row without needing walking aids like canes or walkers. This helps ensure you can safely complete the study assessments.

However, you won't be able to join if you've had major surgery recently or expect to have one during the study, or if you've had a severe allergic reaction in the past. Other reasons you might not be eligible include certain heart conditions, breathing problems, recent history of suicidal thoughts, or if you're taking certain medications that could interfere with the study. The study team will review all your health information carefully to determine if this study is suitable and safe for you.

If you join this study, it will involve several stages over a long period. First, there's a screening period stretching up to 8 weeks to check if you're suitable. After that, some participants will receive a placebo (dummy medicine) for 24 weeks, while others will eventually receive DYNE-101. This is followed by a main treatment period of 24 weeks where you'll receive the study medicine, and then a long-term follow-up that could last up to 168 weeks (about 3 years and 3 months).

The study medicine, DYNE-101, will be given through an intravenous (IV) drip, meaning it's put directly into a vein. You'll have regular visits to the clinic for these infusions, as well as for various assessments. These assessments will include physical exams, checking your muscle strength and movement, possibly blood tests, heart checks like ECGs, and answering questions about your symptoms and how you're feeling. The exact number of visits will depend on which stage of the study you are in, but generally, expect frequent visits, especially at the beginning.