Key Inclusion Criteria:  Medically able to undergo the program procedures, as determined by the treating healthcare professional (HCP). Weakness attributable to ALS and associated with a mutation in the SOD1 gene (SOD1-ALS).  Key Exclusion Criteria:  Previous or current participation in a clinical trial of tofersen. Use of an investigational medicinal product (IMP) for amyotrophic lateral sclerosis (ALS) within 5 half-lives of the IMP before the first dose of tofersen. Participant's primary place of residence is outside of the country of treatment.  NOTE: Other protocol defined Inclusion/Exclusion criteria may apply