Spinal Muscular Atrophy is a rare genetic condition that makes the muscles very weak, often starting in infancy. Some babies receive an early gene‑therapy called Onasemnogene Abeparvovec that can improve outcomes. This study looks at adding another medicine, Salanersen (code name BIIB115), which is given as a small injection into the fluid that surrounds the spinal cord.
The purpose of the study is to find out whether giving Salanersen about six months after the gene‑therapy is safe and can be tolerated well. Children who take part will receive the injection and then be seen regularly for several years. At each visit they will have simple blood draws and brief examinations to check how they are doing.
During the study doctors will watch for any side effects and will also look at a protein called neurofilament light chain that can show nerve damage, and they will perform a test called compound muscle action potential that measures how nerves and muscles work together. The children’s ability to reach basic movement goals such as sitting, standing and walking will be recorded using the World Health Organization motor milestones and other easy‑to‑understand scales like the Hammersmith Infant Neurological Examination, CHOP INTEND, Hammersmith Functional Motor Scale Expanded and Revised Upper Limb Module. The follow‑up continues until the children are several years old, allowing researchers to see long‑term safety and any signs of benefit.
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