Phase 1/2 Study of AOC 1020 in Participants With Facioscapulohumeral Muscular Dystrophy (FSHD)

Inclusion Criteria: * FSHD1 or FSHD2 diagnosis confirmed by documented genetic testing (testing provided by Sponsor) * Ambulatory and able to walk 10 meters (with or without assistive devices such as one cane, walking stick or braces) * At least 1 muscle region suitable for biopsy (testing provided by Sponsor) * Muscle weakness in both upper and lower body, as determined by Investigator Exclusion Criteria: * Pregnant or intends to become pregnant while on study, or active breastfeeding * Unwilling or unable to continue to comply with contraceptive requirements * Body mass index (BMI) \>35.0 kg/m2 at Screening * History of muscle biopsy within 30 days of the screening biopsy or planning to undergo any nonstudy muscle biopsies over the duration of the study * History of bleeding disorders, significant keloid, or other skin or muscle conditions (e.g., severe muscle wasting) that, in the opinion of the Investigator, makes the participant unsuitable for serial muscle biopsy * Anticipated survival less than 2 years * Blood or plasma donation within 16 weeks of Study Day 1 * Any contraindication to MRI * Any abnormal lab values, conditions or diseases 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 * Treatment with any investigative medication within 1 month (or 5 half-lives of the drug, whichever is longer) of Screening