A Study to Investigate the Safety and Pharmacodynamics of a Single Intrathecal Injection (IT) of INS1202 in Participants With Amyotrophic Lateral Sclerosis (ALS)

Key Inclusion Criteria: - * Participant with body mass index (BMI) ≥18 kilograms per square meter (kg/m\^2). * Participant with symptomatic ALS as diagnosed by Gold Coast diagnostic criteria. * Sporadic ALS cohorts: Negative testing for known monogenic mutations associated with familial ALS. * SOD1-ALS (Cohorts 2 and 3 only): Confirmed pathogenic SOD1 mutation, with negative testing for other genetic mutations associated with familial ALS. * Any polymorphism or mutation in the coding region will require additional review by the Sponsor to determine compatibility with the study intervention. * Baseline ALSFRS-R ≥ 24. * ALS disease duration ≤ 42 months. Key Exclusion Criteria: - * Previous treatment for ALS with cellular or gene therapies. * Any investigational medication or treatment (for ALS or other condition). Note: Other protocol-defined inclusion/exclusion criteria may apply.