A Study to Learn About the Effects and Safety of RTA 408 (Omaveloxolone) in People Aged 16 to 40 With Friedreich's Ataxia

Friedreich's ataxia is an autosomal recessive cerebellar ataxia caused by triplet-repeat expansions. The causative mutation is a trinucleotide (GAA) repeat expansion in the first intron of the frataxin gene, leading to impaired transcription of frataxin. The pathological consequences of frataxin deficiency include a severe disruption of iron-sulfur cluster biosynthesis, mitochondrial iron overload coupled to cellular iron dysregulation, and an increased sensitivity to oxidative stress. A hallmark of Friedreich's ataxia is impairment of antioxidative defense mechanisms, which play a major role in disease progression. Studies have demonstrated that nuclear factor erythroid-derived 2-related factor 2 (Nrf2) signaling is grossly impaired in participants with Friedreich's ataxia. Therefore, the ability of omaveloxolone (RTA 408) to activate Nrf2 and induce antioxidant target genes is hypothesized to be therapeutic in participants with Friedreich's ataxia. This 2-part study will evaluate the efficacy, safety, and pharmacodynamics of omaveloxolone (RTA 408) in the treatment of participants with Friedreich's ataxia. Part 1: The first part of this study will be a randomized, placebo-controlled, double-blind, dose-escalation study to evaluate the safety of omaveloxolone (RTA 408) at various doses in participants with Friedreich's ataxia. Part 2: The second part of this study is a randomized, placebo-controlled, double-blind, parallel-group study to evaluate the safety and efficacy of omaveloxolone (RTA 408) 150 mg in participants with Friedreich's ataxia. Participants enrolled in Part 2 will be randomized 1:1 to receive omaveloxolone (RTA 408) 150 mg or placebo. Extension: The extension will assess long-term safety and tolerability of omaveloxolone (RTA 408) in qualified participants with Friedreich's ataxia following completion of Part 1 or Part 2. Participants will not be unblinded to study treatment in Part 1 or Part 2 upon entering the extension study. Participants will receive open-label omaveloxolone (RTA 408) at 150 mg once daily.