Evaluate Safety and Biological Activity of ATYR1940 in Participants With Early Onset Facioscapulohumeral Muscular Dystrophy

Inclusion Criteria:

   - Established, genetically confirmed diagnosis of FSHD.

   - Onset of FSHD signs or symptoms prior to 10 years of age, as documented in the
   participant's medical record or based on participant or family report.

   - Provide written informed consent or assent

   - In the Investigator's opinion, participant is willing and able to complete all study
   procedures and comply with the weekly study visit schedule.

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 or activity on a chronic basis within 4 weeks 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 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.