This study is researching an experimental drug called ALN-SOD (called "study drug"). This study is focused on people with Amyotrophic Lateral Sclerosis (ALS) caused by a change in a gene called the Superoxide Dismutase-1 (SOD1) gene. This type of ALS is known as "SOD1-ALS". This is the first time that ALN-SOD will be given to people.
The aim of the study is to see how safe and tolerable the study drug is.
The study is looking at several other research questions, including:
* The effect the study drug has on specific biomarkers, which are substances in the blood or in the fluid that surrounds the brain and spinal cord, known as Cerebrospinal Fluid (CSF) * How much study drug is in the blood and in the CSF, at different times * Whether the body makes antibodies against the study drug (which could make the drug less effective or could lead to side effects) * What effects the study drug has on ALS symptoms
Weakness attributable to ALS and a SOD1 variant that has been previously described as associated with ALS or is considered likely to cause ALS, as defined in the protocol
Slow Vital Capacity (SVC) ≥50% predicted value based on age, gender and height, measured in upright position
Body Mass Index (BMI) ≤35 kg/m2 at time of screening
If participants are taking riluzole or edaravone, they must be on a stable dose for at least 4 weeks prior to initial dosing visit and are expected to remain at that dose until the end of the study
Concurrent participation in another interventional clinical trial
Has had a tracheostomy
Has dementia, as assessed by the investigator
Has uncontrolled psychiatric disease, including psychosis, active or recent suicidal ideation, untreated major depression, in the past 30 days
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Treatment groupsSee each treatment group below.