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

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.