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 patients with Friedreich's ataxia. Patients enrolled in Part 2 will be randomized 1:1 to receive omaveloxolone (RTA 408) 150 mg or placebo.