nusinersen
Spinraza (nusinersen) is an antisense oligonucleotide from Biogen for spinal muscular atrophy in children and adults. Given into the spinal fluid, it helps the backup SMN2 gene produce more of the survival motor neuron protein that motor neurons need to survive.
This page is based on FDA prescribing information and the EMA medicine record for nusinersen, cross-checked with DailyMed; the mechanism is explained in plain language, and analogies are used only where they stay accurate.
How it works
Explains what the medicine does in the body, not dosing, side effects, or safety.
An analogy
Motor neurons need a protein called SMN to survive. In spinal muscular atrophy the main gene that makes it, SMN1, is broken, and a backup gene, SMN2, sends out messages that are mostly edited wrong and fall apart. Nusinersen is a small patch of synthetic genetic code that sticks to those backup messages and fixes the editing error, so more complete instructions get through and the cell makes more working SMN protein.
In simple terms
Spinal muscular atrophy is caused by a defect in the SMN1 gene, so motor neurons lack survival motor neuron (SMN) protein and gradually stop working, leading to progressive muscle weakness. People also carry a backup gene, SMN2, but most of its messages are edited incorrectly and make little usable protein. Nusinersen is a short strand of synthetic genetic code, an antisense oligonucleotide, that binds SMN2's messages and corrects the editing, raising the amount of full-length SMN protein. It is given into the fluid surrounding the spinal cord, where motor neurons need the protein most.
In depth
Nusinersen is a survival motor neuron-2 (SMN2)-directed antisense oligonucleotide administered intrathecally. It binds a regulatory sequence in SMN2 pre-mRNA and modulates splicing so that exon 7 is included, increasing the proportion of full-length, stable SMN protein produced from the SMN2 gene. In spinal muscular atrophy, where SMN1 is deleted or mutated, this restored SMN protein supports motor neuron survival and function. It is approved for the treatment of SMA in pediatric and adult patients.
See it in motion
A schematic animation of the mechanism — simplified for clarity, not drawn to scale.
How nusinersen fixes the editing error
- In spinal muscular atrophy the main gene that makes it, SMN1, is broken, and a backup gene, SMN2, sends out messages that are mostly edited wrong and fall apart.
- Nusinersen is a short strand of synthetic genetic code, an antisense oligonucleotide, that binds SMN2's messages and corrects the editing, raising the amount of full-length SMN protein.
- It binds a regulatory sequence in SMN2 pre-mRNA and modulates splicing so that exon 7 is included, increasing the proportion of full-length, stable SMN protein produced from the SMN2 gene.
- It is given into the fluid surrounding the spinal cord, where motor neurons need the protein most.
Target: Survival motor neuron-2 (SMN2) pre-mRNA
The RNA message produced by the SMN2 backup gene; in spinal muscular atrophy the main SMN1 gene is defective, so motor neurons depend on how much usable protein this message yields.
Approved uses
Approved uses differ by country and change over time. Always follow your local prescribing information.
Approved uses in United States
FDA- For the treatment of spinal muscular atrophy (SMA) in pediatric and adult patients
Approved uses in European Union
EMA- For the treatment of 5q spinal muscular atrophy
Official sources
The statements on this page trace back to these records.
- Spinraza (nusinersen) — Summary of product characteristics and package leaflet, English version
European Medicines Agency
- DailyMed: SPINRAZA (nusinersen) official US label
U.S. National Library of Medicine, DailyMed
- U.S. Food and Drug Administration: nusinersen prescribing information
U.S. Food and Drug Administration
This page explains how the medicine works — it isn’t the patient leaflet. For anything that applies to you, read the leaflet that came with your medicine or ask your pharmacist.
MedUnfold provides educational content and is not medical advice. Always follow your local prescribing information and healthcare professional.