In this study, researchers will learn more about the use of nusinersen (BIIB058) in participants with spinal muscular atrophy (SMA). This study is an extension study and will enroll only those participants who have completed treatment in the parent study, 232SM203. The main goal of the study is to learn about the long-term safety of nusinersen. The main questions researchers want to answer are: * How many participants have adverse events and serious adverse events during the study? * How do the results of electrocardiograms (ECGs), vital signs, and laboratory tests including blood and urine tests change after treatment? * How many participants have a low platelet count after treatment? * How many participants had a change in the time it took for their heart to recharge between beats after treatment? * How does each participant's height and other measures of growth change after treatment? * How much do the results of neurological exams that check movement, reflexes, and brain function change after treatment? Researchers will also learn about the effect of nusinersen on mobility using various tests. They will study body movements, reflexes, balance, and coordination. They will also record if participants need help with breathing. The 232SM302 study will be done as follows: * Participants will be screened to check if they can join the study. * Participants will receive their 1st dose of nusinersen in this study about 4 months after their final dose in the parent study. * Each participant will receive nusinersen once every 4 months during the treatment period. * Nusinersen will be given through a lumbar puncture, which involves injecting the drug into the fluid around the spinal cord in the lower back. * The treatment period will last for up to 64 months (1921 days). * There will be a follow-up safety period that lasts from 4 to 8 weeks. * In total, participants will have up to 19 study visits. Participants will stay in the study for close to 6 years.
Age range
2 Years
Sex
ALL
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A starting point for the conversation — always confirm anything about your own eligibility, costs, and care with the study team and your doctor.
Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)
Timeframe: Up to Day 1921
Change from Baseline in Growth Parameters
Timeframe: Up to Day 1921
Number of Participants With Shifts from Baseline in Clinical Laboratory Parameters
Timeframe: Up to Day 1921
Number of Participants With Shifts from Baseline in Electrocardiogram (ECG)
Timeframe: Up to Day 1921
Number of Participants With Shifts from Baseline in Vital Signs
Timeframe: Up to Day 1921
Change from Baseline in Activated Partial Thromboplastin Time (aPTT)
Timeframe: Up to Day 1921
Change from Baseline in Prothrombin Time (PT)
Timeframe: Up to Day 1921
Change from Baseline in International Normalized Ratio (INR)
Timeframe: Up to Day 1921
Change from Baseline in Urine Total Protein
Timeframe: Up to Day 1921
Change from Baseline in Neurological Examination Outcomes for Participants ≤2 Years of Age
Timeframe: Up to Day 1921
Number of Participants with Change from Baseline in Neurological Examination Outcomes for Participants >2 Years of Age
Timeframe: Up to Day 1921
Percentage of Participants With a Postbaseline Platelet Count Below the Lower Limit of Normal on at least 2 Consecutive Measurements
Timeframe: Up to Day 1921
Percentage of Participants With a Postbaseline Corrected QT Interval Using Fridericia's Formula (QTcF) of >500 millisecond (msec) and an Increase from Baseline to Any Postbaseline Timepoint in QTcF of >60 msec
Timeframe: Up toDay 1921