BIIB091

A Safety, Tolerability, Pharmacokinetic, and Pharmacodynamic Study of BIIB091, a Bruton's Tyrosine Kinase (BTK) Inhibitor, in Healthy Adult Participants

Study of BIIB091 Formulations in Healthy Participants

A Study to Find Out How Multiple Doses of BIIB091 Affect the Electrical Activity of the Heart in Healthy Participants

A Study to Find Out How Different Forms of BIIB091 is Processed in The Body With and Without Food in Healthy Participants

A Study to Learn About the Safety of BIIB091 and Its Effect on Brain Inflammation When Taken Alone or With Diroximel Fumarate (DRF) in Adults With Relapsing Forms of Multiple Sclerosis (MS)

A 2-Part, Multicenter, Randomized, Blinded, Active-Controlled Phase 2 Study to Sequentially Evaluate the Safety and Efficacy of BIIB091 Monotherapy and BIIB091 Combination Therapy With Diroximel Fumarate in Participants With Relapsing Forms of Multiple Sclerosis