The study is testing a drug called **pridopidine** for adults with amyotrophic lateral sclerosis (ALS), a disease that affects nerve cells in the brain and spinal cord. Researchers want to find out if pridopidine can slow down the disease and if it's safe. In this study, participants will take either pridopidine or a placebo (a pill that looks like pridopidine but has no medicine) for 48 weeks. After that, everyone will take pridopidine for another 48 weeks. Participants visit the clinic every 1-3 months for checkups and tests. The entire study lasts about 102 weeks, which includes screening and follow-up. Participants must have definite or probable ALS, and be able to swallow capsules. They should not have certain medical conditions or previous treatments that may interfere with the study.

• The study lasts for about 102 weeks.
• Participants take medication daily and visit clinics every 1-3 months.
• Participants will receive a placebo first, then the actual drug.