The mFARS is a validated and sensitive rating scale that was developed to quantitatively assess the severity of the neurologic features of FA in adults and adolescents. Scores on the mFARS range from 0 to 93, with lower scores indicating better neurological function. The subscales of the mFARS assessment and maximum score for each subscale are: bulbar function (Subscale A; 2 assessments of speech and cough; maximum score = 5), upper limb coordination (Subscale B; 5 assessments of coordination of movement and function in arms and hands with each limb scored individually; maximum score = 36), lower limb coordination (Subscale C; 2 assessments of coordination of movement and function of lower limbs with each limb scored individually; maximum score = 16), and upright stability (USS, Subscale E; 9 assessments of sitting posture, stance, tandem walk, and gait assessments; maximum score = 36).

The mFARS is a validated and sensitive rating scale that was developed to quantitatively assess the severity of the neurologic features of FA in adults and adolescents. Scores on the mFARS range from 0 to 93, with lower scores indicating better neurological function. The subscales of the mFARS assessment and maximum score for each subscale are: bulbar function (Subscale A; 2 assessments of speech and cough; maximum score = 5), upper limb coordination (Subscale B; 5 assessments of coordination of movement and function in arms and hands with each limb scored individually; maximum score = 36), lower limb coordination (Subscale C; 2 assessments of coordination of movement and function of lower limbs with each limb scored individually; maximum score = 16), and upright stability (USS, Subscale E; 9 assessments of sitting posture, stance, tandem walk, and gait assessments; maximum score = 36).

The C-SSRS is a low-burden measure of the spectrum of suicidal ideation and behavior that was developed to assess severity and track suicidal events through any treatment of individuals ≥ 6 years of age. The C-SSRS is a clinical interview providing a summary of both ideation and behavior that can be administered by the clinician during any evaluation or risk assessment to identify the level and type of suicidality present. The assessment includes "yes" or "no" responses for 5 questions each, related to suicidal ideation (wish to be dead, non-specific active suicidal thoughts, active suicidal ideation with any methods, active suicidal ideation with some intent, active suicidal ideation with specific plan) and suicidal behavior (preparatory acts or behavior, aborted attempt, interrupted attempt, actual attempt, suicide). Numeric ratings are provided for severity of ideation, from 1 to 5, with 5 being the most severe.

Assessment of Tanner stages (a scale of physical development) will be performed by a medical doctor experienced with this assessment. Tanner score ranges from Stage 1 (childhood) to Stage 5 (full physical maturity). Information regarding Tanner staging will be collected at baseline for all participants and will be stopped once the participant reaches Tanner Stage 5 in all gender-appropriate scales.

Assessment of Tanner stages (a scale of physical development) will be performed by a medical doctor experienced with this assessment. Tanner score ranges from Stage 1 (childhood) to Stage 5 (full physical maturity). Information regarding Tanner staging will be collected at baseline for all participants and will be stopped once the participant reaches Tanner Stage 5 in all gender-appropriate scales.

Peak work attained during maximal exercise testing. Cycle ergometry using a recumbent stationary bicycle was used, and workload was increased incrementally. Peak work is defined as the workload at which patients reach maximal volition (defined as an inability to continue to exercise due to exhaustion).

The mFARS includes 4 of the 5 sections of the Friedreich's Ataxia Rating Scale (FARS): bulbar (score 0 to 11), upper limb coordination (score 0 to 36), lower limb coordination (score 0 to 16), and upright stability (score 0 to 36). The minimum score is 0 and the maximum score is 99. A lower score indicates better neurological function.

An AE is any untoward medical occurrence in a patient or clinical investigation participant administered a pharmaceutical product and that does not necessarily have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (including abnormal laboratory finding), symptom, or disease temporally associated with use of a medicinal (investigational) product, whether or not related to medicinal (investigational) product. SAE is any untoward medical occurrence that at any dose results in death, in the view of investigator, places the participant at immediate risk of death (life-threatening event), requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, results in congenital anomaly/birth defect or is medically important event.

Vital signs, including blood pressure (BP), heart rate (HR), and oral body temperature, will be assessed.