A Study to Assess the Safety, Tolerability, and Pharmacokinetics of BIIB078 in Adults With C9ORF72-Associated Amyotrophic Lateral Sclerosis

The primary objective of this study is to evaluate the safety and tolerability of BIIB078 in adults with C9ORF72-Amyotrophic Lateral Sclerosis (ALS). The secondary objectives of this study are to evaluate the pharmacokinetic profile of BIIB078 and to evaluate the effects of BIIB078 on clinical function. As the first-in-human study, the study enrolls a small number of participants in each cohort. Every participant in a cohort is treated with the same dose or placebo. The study is designed to evaluate and confirm the safety of each dose before enrolling and exposing new participants to a higher dose in the next cohort.