A Study to Learn if Taking BIIB141 (Omaveloxolone) Affects How Omeprazole is Processed in the Body and About BIIB141's Safety in Healthy Adults Aged 18 to 55

The primary objective of this study is to assess the effect of omaveloxolone on the pharmacokinetics (PK) of omeprazole in healthy adult participants.

The secondary objective of this study is to assess the effect of omaveloxolone on the PK of omeprazole and to assess the safety and tolerability of a single dose administered alone and when administered concurrently with omeprazole to healthy adult participants.

Key Inclusion Criteria:

• All female participants of childbearing potential must have negative results for pregnancy tests as follows:

• At screening, based on a serum sample obtained within 28 days prior to initial study drug administration; and
• Prior to dosing, based on a serum sample obtained on Study Day -1.
• Body mass index (BMI) at screening between 18 and 32 kilograms per square meter (kg/m^2), inclusive.

Key Exclusion Criteria:

• History of any clinically significant cardiac, endocrine, gastrointestinal, hematologic, hepatic, immunologic, metabolic, urologic, pulmonary, neurologic, dermatologic, psychiatric, or renal disease, or other major disease, as determined by the Investigator.
• Clinically significant, as determined by the Investigator, 12-lead electrocardiogram (ECG) abnormalities.
• History of, or positive test result at Screening for, human immunodeficiency virus (HIV).
• History of hepatitis C infection or positive test result at Screening for hepatitis C virus antibody (HCV Ab).
• Current hepatitis B infection [defined as positive for hepatitis B surface antigen (HBsAg) and/or total anti-HBc]. Participants with immunity to hepatitis B from previous natural infection (defined as negative HBsAg, positive anti-HBc, and positive anti-HBs) or vaccination (defined as negative HBsAg, negative anti-HBc, and positive anti-HBs) are eligible to participate in the study.
• Chronic, recurrent, or serious infection (e.g., pneumonia, septicemia, and herpes simplex virus), as determined by the Investigator, within 90 days prior to Screening or between Screening and Day -1.
• Symptoms of bacterial, fungal, or viral infection (including upper respiratory tract infection) within 14 days prior to Screening or between Screening and Day -1. Participants with local fungal infection (e.g., candidiasis, tinea) are eligible to be rescreened after successful treatment of the infection.
• Prior exposure to omaveloxolone.

NOTE: Other protocol-defined inclusion/exclusion criteria may apply.