Evaluate Safety and Biological Activity of ATYR1940 in Patients With Early Onset Facioscapulohumeral Muscular Dystrophy (FSHD)

• Incidences of Treatment-Emergent adverse events and serious adverse events [ Time Frame: 12 weeks ]
  Incidences of adverse events including serious and severe adverse events overall and by intensity
• Changes from Baseline in safety laboratory test results [ Time Frame: Changes from Baseline after 12 weeks ]
  Changes from Baseline in safety laboratory test results
• Changes from Baseline in pulmonary evaluation [ Time Frame: Changes from Baseline after 12 week ]
  Change from Baseline in pulmonary evaluation
• Changes from Baseline in visual assessment [ Time Frame: Changes from Baseline after 12 weeks ]
  Changes in Baseline in visual acuity
• Changes from Baseline in hearing [ Time Frame: Changes from Baseline after 12 weeks ]
  Safety Primary Outcome Measure - Changes from Baseline in hearing based on audiometry

• Immunogenicity Outcome Measure - Incidence and level of ADA [ Time Frame: 12 weeks ]
  Incidence and level of ADA titers
• Immunogenicity Outcome Measure - Incidence and level of Jo-1 Ab [ Time Frame: 12 weeks ]
  Incidence and level of Jo-1 Ab titers
• Immunogenicity Outcome Measure - Incidence of infusion reactions [ Time Frame: 12 weeks ]
  Incidence of infusion reactions

• Pharmacodynamic Additional Outcome Measure - Changes in FSHD-related inflammatory immune state [ Time Frame: 12 weeks ]
  Effects assessed by changes in muscular dystrophy-related inflammatory immune state in peripheral blood
• Pharmacodynamic Additional Outcome Measure - Changes from baseline clinical parameters [ Time Frame: 12 weeks ]
  Changes from baseline in muscle strength based on manual muscle strength

• Biological: ATYR1940
  ATYR1940 will be administered as an IV infusion at doses of 0.3, 1.0, and 3.0 mg/kg using intrapatient dose escalation. The dose level in this study will not exceed 3.0 mg/kg
• Biological: Placebo
  An initial IV infusion of placebo will be supplied as normal saline, and administered over a 30-minute period at Week 1.

• Experimental: ATYR1940
  Intrapatient dose escalation ATYR1940: ATYR1940 will be administered as an IV infusion at doses of 0.3, 1.0, and 3.0 mg/kg for up to 12 Weeks. The dose level in this study will not exceed 3.0 mg/kg.
  Intervention: Biological: ATYR1940
• Placebo Comparator: Placebo
  An initial IV infusion of placebo will be supplied as normal saline, and administered over a 30-minute period at Week 1.
  Intervention: Biological: Placebo

Inclusion Criteria:

• Established, genetically confirmed diagnosis of FSHD.
• Onset of FSHD signs or symptoms prior to 10 years of age, as documented in the patient's medical record or based on patient or family report.
• Provide written informed consent or assent
• In the Investigator's opinion, patient 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 patient's ability to complete the study protocol.
• Muscle biopsy within 30 days before baseline.