A Study to Evaluate the Efficacy, Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of BIIB067 Administered to Adult Subjects With Amyotrophic Lateral Sclerosis and Confirmed Superoxide Dismutase 1 Mutation

The primary objectives of Parts A and B of this study are to evaluate the safety, tolerability, and pharmacokinetics (PK) of ascending doses of tofersen in adults with ALS and a documented superoxide dismutase 1 (SOD1) mutation. The primary objective of Part C of this study is to evaluate the clinical efficacy of tofersen administered to adults with ALS and a confirmed SOD1 mutation.The secondary objective of Parts A and B of this study is to evaluate the effects of tofersen on levels of total SOD1 protein in the cerebrospinal fluid (CSF). The secondary objectives of Part C are to evaluate the safety, tolerability, pharmacodynamic (PD), and biomarker effects of tofersen.