AOC 1001-CS2 (MARINA-OLE) is a Phase 2 extension of the AOC 1001-CS1 (MARINA) study to evaluate the safety, tolerability, efficacy, pharmacokinetics and pharmacodynamics of multiple-doses of AOC 1001 Administered Intravenously to Adult Myotonic Dystrophy Type 1 (DM1) patients

This study will continue to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, and efficacy of AOC 1001 in participants that enrolled in the randomized, placebo-controlled, First-In-Human Phase 1/2 AOC 1001-CS1 (MARINA) clinical study.

Participants from AOC 1001-CS1 are eligible to enroll in AOC 1001-CS2 if they have satisfactorily completed AOC 1001-CS1.

After completion of Q8W Visit 6 assessments, participants will have the option to enroll in another AOC 1001 open-label extension (OLE) study. Participants who do not enroll in an AOC 1001 OLE study will be monitored for safety for a total of 8 weeks from the last dose of study drug. Total duration on study is up to 37 months (3 years 1 month).

As of September 2024, the dosing regimen was updated to every 8 weeks.

Key Inclusion Criteria:

• Completion of AOC 1001-CS1 (MARINA) study with satisfactory compliance and no significant tolerability issues

Key Exclusion Criteria:

• Pregnancy, intent to become pregnant, or active breastfeeding
• Unwilling or unable to continue to comply with contraceptive requirements
• Any new conditions or worsening of existing conditions that in the opinion of the investigator or sponsor would make the participant unsuitable for the study or could interfere with participation or completion of the study

Participants will receive one blinded treatment at Day 43. Treatment assignment on this day will be based on treatment received in AOC 1001-CS1 so that participants who did not receive active drug on Day 43 in AOC 1001-CS1 will received active drug on Day 43 in AOC 1001-CS2.