Evaluate Safety and Biological Activity of ATYR1940 in Participants With Limb Girdle Muscular Dystrophy 2B (LGMD2B) and Facioscapulohumeral Muscular Dystrophy (FSHD)

An Open-Label, Intrapatient Dose Escalation Study to Evaluate the Safety, Tolerability, Immunogenicity, and Biological Activity of ATYR1940 in Patients With Limb Girdle and Facioscapulohumeral Muscular Dystrophies

The purpose of this study is to assess the safety and biological activity of ATYR1940 in participants with LGMD2B and FSHD.

Inclusion Criteria:

• Provided informed consent.
• Investigator's opinion, participant is willing and able to complete all study procedures and comply with the study visit schedule.

Participant with LGMD2B:

• Established, genetically confirmed diagnosis of LGMD2B.
• Either the presence of a short tau inversion recovery (STIR) positive muscle on lower extremity skeletal muscle magnetic resonance imaging (MRI), or, if no STIR positive muscles, meets muscle biomarker criteria.

Participant with FSHD:

• Established, genetically confirmed diagnosis of FSHD.
• The presence of a STIR positive muscle on lower extremity skeletal muscle MRI.

Exclusion Criteria:

• Currently receiving treatment with an immunomodulatory agent, including targeted biological therapies within the 3 months before baseline; corticosteroids within 3 months before baseline; or high-dose non-steroidal anti-inflammatory agents within 2 weeks before baseline.
• Currently receiving curcumin or albuterol; use of a product that putatively enhances muscle growth on a chronic basis within 30 days before baseline; statin treatment initiation or significant adjustment to statin regimen within 3 months before baseline (stable, chronic statin use is permissible).
• Use of an investigational product or device within 30 days before baseline.
• Evidence of an alternative diagnosis other than LGMD2B or FSHD or a coexisting myopathy or dystrophy, based on prior muscle biopsy or other available investigations.
• History of severe restrictive or obstructive lung disease or evidence for interstitial lung disease on screening chest radiograph.
• History of anti-synthetase syndrome, prior Jo-1 Ab-positivity, or a positive or equivocally positive Jo-1 Ab test result during screening.
• Chronic infection, such as hepatitis B, hepatitis C, or human immunodeficiency virus or a history of tuberculosis.
• Vaccination within 8 weeks before baseline or vaccination is planned during study participation.
• Symptomatic cardiomyopathy or severe cardiac arrhythmia that may in the Investigator's opinion, limit the participant's ability to complete the study protocol.
• Muscle biopsy within 30 days before baseline.