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

TEAEs were defined as adverse events (AEs) with an onset following administration of the first dose of study drug. AEs were defined as any untoward medical occurrence in a participant administered study drug and that does not necessarily have a causal relationship with the study drug. Worsening of a pre-existing medical condition should have been considered an AE if there was either an increase in severity, frequency, or duration of the condition or an association with significantly worse outcomes. SAEs were defined as any AE that, in the view of either the Investigator or Sponsor, resulted in any of the following outcomes as fatal, life-threatening, required in-participant hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, a congenital anomaly/birth defect, an important medical event. A summary of all SAEs and Other AEs (nonserious) regardless of causality is located in 'Reported Adverse Events' Section.

Laboratory parameters included hematology (hematocrit, hemoglobin, red blood cell count, white blood cell count with differential [neutrophils, lymphocytes, monocytes, eosinophils, basophils], and platelet count); serum chemistries (blood urea nitrogen, creatinine, total bilirubin, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, alkaline phosphatase, total protein, sodium, potassium, bicarbonate, calcium, chloride, magnesium, inorganic phosphate, creatine kinase, lactate dehydrogenase, erythrocyte sedimentation rate, C-reactive protein, troponin, myoglobin, insulin-like growth factor 1, and cholesterol [nonfasting]); and urinalysis (color, pH, specific gravity, protein, glucose, ketones, and blood). Clinically significant laboratory abnormalities were based upon Investigator's discretion. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

Ocular parameters included vitreous, retina, macula, choroid, optic nerve, and optic nerve pallor. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

Pulmonary evaluations included pulmonary function tests and pulse oximetry. Clinically significant changes were to be reported as adverse events. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

Titers through Week 12 are summarized.

Participants with Jo-1 Ab levels ≥1.5 units/milliliter (U/mL) were to be discontinued from dosing of the study drug.

Infusion-related reactions included fever, chills, rigors, myalgia, facial erythema, systemic erythema, pallor, facial swelling, chest tightness, difficulty breathing, wheezing, stridor, tachypnea, bronchospasm, cough, tachycardia, significant pulse rate increase from baseline without obvious cause, bradycardia, significant pulse rate decrease from baseline, pre-syncope or syncope, hypotension, orthostatic hypotension, blood pressure swings (including hypertension), skin rash, urticaria, angioedema, pruritus, difficulty speaking, hoarse voice, raspy voice, excessive salivation, difficulty swallowing, nausea, vomiting, cramps, diarrhea; swelling of the throat, tongue, mouth, or lip, and development of a headache especially moderate or greater after start of infusion. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

MMT was graded on a scale from 0 (no movement) to 10 (normal movement). Each side of the body and the position in which each muscle was tested were recorded for each participant. The total MMT score were calculated by averaging a converted-MMT scores across all tested muscle groups. Decreased motor function was indicated by decreased individual muscle or composite MMT score.