There are 2 parts in this study. During Part 1, participants will take either BIIB141 or a placebo once a day for 52 weeks. After completion of Part 1, participants will be invited to participate in Part 2 during which all participants will take BIIB141 for up to 104 weeks.
Participants will be screened to check to see if they are eligible to join the study. Participants who meet all the eligibility criteria will be invited to begin the study at a designated study research center.
In Part 1, participants will take BIIB141 or the placebo in a study research center on Day 1, and then at in-person visits at Week 4, Week 12, Week 26, and Week 52. On all other days, they will take BIIB141 or the placebo at home. Part 1 lasts up to 52 weeks. Participants will have up to 10 visits to their study research center and a phone call at Week 2.
During Part 2, participants from Part 1 will either continue taking BIIB141 or start it if they were taking the placebo. In Part 2, participants will have visits at Weeks 4, 8,12, 26, and every 26 weeks after that until they leave the study, and a phone call at Week 2. There will be a final phone call to check on the participants’ health 31 days after their last dose. Part 2 will last up to 104 weeks.
Each participant will be in the study up to approximately 3 years.
Key Inclusion Criteria for Part 1:
- Diagnosed with genetically confirmed Friedreich’s ataxia (FA). This includes being homozygous for GAA repeat expansions, or having a GAA repeat expansion on one allele and a point mutation, deletion, or other non GAA repeat expansion mutation on the other allele.
- Symptomatic for FA as reported by the participant and/or their parent or caregiver.
- Children 7 to 15 must have an upright stability score on the modified Friedreich’s Ataxia Rating Scale (mFARS) between 10 and 34 at baseline.
Key Exclusion Criteria for Part 1:
- Glycosylated hemoglobin A1C (HbA1c) > 11% (indicator of poorly controlled diabetes)
- B-type natriuretic peptide (BNP) > 200 pg/mL at screening (measure of heart health)
- Ejection fraction <40% as measured by echocardiogram at screening visit (measure of heart health)
- Clinically significant cardiac disease except mild to moderate cardiomyopathy
Open Label Extension (Part 2) Eligibility:
- Participants have completed Part 1 and no discontinuation criteria have been met.
- Safety and tolerability data from Part 1 are supportive of continuation in the judgement of the investigator.
Other inclusion/exclusion criteria may apply.