In this study, researchers will learn more about BIIB141, also known as omaveloxolone or SKYCLARYS®. This drug has been approved, or made available for doctors to prescribe, for people with Friedrich's Ataxia (FA) who are at least 16 years old. But, it is not yet available for children and teens with FA who are younger than 16 years old. The main goal of this study is to learn how BIIB141 is processed in the body of children and teens who are 2 to 15 years old.
The main question researchers want to answer in this study is:
* How does the body process BIIB141 in children and teens?
* How many participants have medical problems during the study?
* Are there any changes in the participants' overall health during the study?
* Are there any changes in the participants' heart health?
* Are there any changes in how the participants move through puberty? Puberty is the time in someone's life when their body changes from a child to an adult.
This study will be done as follows:
* Participants will be screened to see if they can join the study. The screening period will be up to 14 days, after which participants will check into their study research center.
* There are 2 parts to this study. During Part 1, participants will take a single dose of BIIB141. Participants will be in 1 of 7 different groups based on their age:
* Group A1: 12 to 15 years old, taking 150 milligrams (mg) of BIIB141
* Group A2: 12 to 15 years old, taking a dose of BIIB141 based on the data from Group A1
* Group B1: 7 to 11 years old, taking a dose of BIIB141 based on Group A1 data
* Group C1: 2 to 6 years old, taking a dose of BIIB141 based on Groups A1, A2, and B1 data
* Group A3: 12 to 15 years old, taking a dose of BIIB141 based on Groups A1, A2, and B1 data
* Group B2: 7 to 11 years old, taking a dose of BIIB141 based on Groups A1, A2, and B1 data
* Group C2: 2 to 6 years old, taking a dose of BIIB141 based on Group A1, A2, A3, B1, B2, and C1 data.
* During Part 2, participants from Part 1 will take BIIB141 once in the study research center. Cohort A1 will take 150 mg of BIIB141. Dose of Cohorts A2 and B1 will be based on data from Cohort A1, dose of Cohorts C1, A3 and B2 will be based on data from Cohorts A1, A2 and B1, while Cohort C2's dose will be based on all the other groups. Participants will then take it once a day at home.
* After leaving the study research center in Part 2, participants will return for tests at Week 4, Week 12, Week 24, and then every 24 weeks. Participants will also be contacted by telephone at Week 2, Week 8, and Week 18, and about 30 days after their last dose of the study drug.
* Participants will be in this study for up to 302 weeks.