A Study to Learn More About the Effects and Long-Term Safety of Omaveloxolone (BIIB141) in Children and Teens With Friedreich's Ataxia

A Phase 3 Study to Evaluate the Efficacy, Safety, Pharmacokinetics, and Pharmacodynamics of Omaveloxolone (BIIB141) in Participants With Friedreich's Ataxia Aged 2 to < 16 Years

In this study, researchers will learn more about omaveloxolone, also known as BIIB141 or SKYCLARYS®. Omaveloxolone is already approved for people with Friedreich's Ataxia (FA) who are 16 years of age or older. However, it is not yet available for younger teens and children. The main goal of this study is to learn how omaveloxolone affects symptoms of FA and its safety in younger participants between the ages of 2 and 15 years old.

The main questions researchers want to answer in this study are:

• How does omaveloxolone affect the participants' FA symptoms?
• How many participants have adverse events during the study?
• Are there any changes in the participants' overall health or heart health? Adverse events are health problems that may or may not be caused by the study drug.

Researchers will use the modified Friedreich's Ataxia Rating Scale (mFARS) to test nerve function. The mFARS tests movement ability, balance, coordination, speech, and arm and leg functions.

They will also use a number of questionnaires to learn more about participants' quality of life, muscle strength, and ability to perform daily tasks. Researchers will also note any changes as participants go through puberty.

Finally, researchers will learn more about how the body processes omaveloxolone in children and teenagers.

This study will be done in 2 parts as follows:

• Participants will be screened for up to 4 weeks to check if they can join the study.
• In Part 1, participants will be randomly assigned to take either omaveloxolone or a placebo by mouth once a day for about 1 year. A placebo looks like the study drug but contains no real medicine.
• Part 1 will be double blind. This means that the participants, study doctor, and site staff will not know if the participants are receiving omaveloxolone or a placebo.
• Including screening, participants will have up to 9 clinic visits and 1 phone call during Part 1. If a participant does not join Part 2, they will have another safety follow-up phone call a month after their last dose of omaveloxolone.
• Participants who complete Part 1 will move onto Part 2 where everyone will receive omaveloxolone for about 2 years.
• During Part 2, participants will have up to 8 clinic visits and 1 phone call. Participants will also have a follow-up phone call about a month after they stop taking omaveloxolone.
• In total, participants will have up to 17 clinic visits and 3 phone calls. Each participant will be in the study for up to 3 years.

The primary objective of Part 1 is to evaluate the efficacy of omaveloxolone as measured by upright stability score (USS) and the secondary objectives are to evaluate the efficacy of omaveloxolone as measured by additional secondary efficacy outcomes, safety of omaveloxolone and the plasma concentration of omaveloxolone after single and multiple dose administration.

The primary objective of Part 2A is to evaluate the efficacy of omaveloxolone and the secondary objectives are to characterize the efficacy of omaveloxolone as measured by additional secondary outcomes, evaluate the safety and tolerability of omaveloxolone and plasma concentration of omaveloxolone after single and multiple dose administration.

The primary objective for Part 2B is to evaluate the safety and tolerability of long-term omaveloxolone use and the secondary objective is to evaluate the efficacy of omaveloxolone following long-term use.

Part 1: Key inclusion criteria:

• Diagnosed with genetically confirmed Friedreich's Ataxia (FA), i.e., homozygous for guanine-adenine-adenine (GAA) repeat expansion in intron-1 of the frataxin gene, or GAA repeat expansion in 1 allele and with point mutations or deletions, or other non-GAA expansion mutations in the other allele.
• Symptomatic for FA as confirmed by clinician assessment. a. Children 7 to < 16 years must also have an upright stability score (USS) score of 10 to ≤ 34 at baseline

Part 1: Key exclusion criteria:

• Glycosylated hemoglobin A1C (HbA1c) > 11%
• B-type natriuretic peptide (BNP) > 200 picograms per milliliter (pg/mL) at screening
• Ejection fraction (EF) < 40% [based on echocardiogram (ECHO) performed at screening visit]
• Clinically significant cardiac disease except mild to moderate cardiomyopathy

Part 2A: Eligibility criteria:

• They have completed Part 1 of the study and no discontinuation criteria have been met.
• Safety and tolerability data from Part 1 are supportive of continuation in the judgement of the investigator.

Part 2B: Eligibility criteria:

• Participants have completed Part 1 of the study and no discontinuation criteria have been met.
• Safety and tolerability data from Part 1 are supportive of continuation in the judgement of the Investigator.

Note: Other protocol-defined Inclusion/Exclusion criteria may apply.