Phase 2 Open-label Extension Study of AOC 1020 in Participants With Facioscapulohumeral Muscular Dystrophy (FSHD)

Inclusion Criteria: 1. Ability to provide written informed consent (signed and dated) and any authorizations required by local law and be willing and able to comply with all study requirements. When enrolling participants who are minors, it is necessary to also obtain consent from a legally designated representative and the participant will receive information in a way adapted to their age and mental maturity. 2. Completion of AOC 1020-CS1 with the following as judged by the Investigator and Sponsor: 1. No significant tolerability issues 2. Satisfactory compliance with the AOC 1020-CS1 protocol requirements Exclusion Criteria: 1. Pregnancy, intent to become pregnant during the clinical study, or active breastfeeding. 2. Unwilling or unable to continue to comply with contraceptive requirements for the length of AOC 1020-CS2. 3. Any new conditions or worsening of existing condition(s) 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. (Note: FSHD progression is not exclusionary, even if the participant no longer has the ability to walk 10 meters without a walker or two canes.)