An adverse event (AE) is any untoward medical occurrence, whether or not the event is considered related to the investigational product. A TEAE is any adverse change from the subject's baseline condition, including any laboratory test value abnormality judged as clinically significant by the investigator, that occurs on or after the date of the first dose of study drug administered at home and throughout the duration of the clinical study, whether the adverse event is considered related to the treatment or not. A serious AE (SAE) is an AE that results in death, is life-threatening, results in persistent or significant disability or incapacity, inpatient hospitalization or prolongation of an existing hospitalization, is a congenital anomaly or birth defect, or other medically important event.

An adverse event (AE) is any untoward medical occurrence, whether or not the event is considered related to the investigational product. A TEAE is any adverse change from the subject's baseline condition, including any laboratory test value abnormality judged as clinically significant by the investigator, that occurs on or after the date of the first dose of study drug administered at home and throughout the duration of the clinical study, whether the adverse event is considered related to the treatment or not. An SAE is an AE that results in death, is life-threatening, results in persistent or significant disability or incapacity, inpatient hospitalization or prolongation of an existing hospitalization, is a congenital anomaly or birth defect, or other medically important event.

NAb testing only for those participants with a positive ADA test. Baseline is defined as the last non-missing measurement/assessment on the date of Week 26 Visit from study HZNP-ACT-301 (NCT02415127). If this measurement was missing or otherwise unavailable, it was the last non-missing measurement/assessment on or prior to first dose in this study. If the participant discontinued the study, then premature withdrawal assessments were mapped to the nearest scheduled visit based on schedule of the assessment and the study day. If the mapped visit was already available then the visit was mapped to the next schedule visit. Last on study assessment is the last non-missing post-baseline assessment for each participant.

The FARS assessment includes neurological signs that specifically reflect neural substrates affected in FA. Based on a neurological examination, bulbar, upper limb, lower limb, peripheral nerve, and upright stability/gait functions were assessed. The FARS-mNeuro score excludes the peripheral nervous system subscale score and the facial and tongue atrophy and fasciculations from the bulbar subscale score. Scores range from 0 (normal) to 93 (most impairment). A negative change from baseline is an improvement.