ABOUT SMA / HOW SMA AFFECTS MUSCLES

Motor neuron loss leads to muscle weakness in SMA

SMN protein is essential for motor neuron survival1

Muscles are controlled by motor neurons that transmit signals from the CNS.2 SMN protein plays an important role in the health and function of these motor neurons.1

Motor neuron degeneration

Patients with SMA are born with a homozygous deletion or heterozygous mutation of their SMN1 gene, resulting in insufficient production of functional SMA protein.3 This leads to motor neuron degeneration, muscle weakness, and muscle atrophy.1 Muscle weakness progresses over time, with a wide range of severity, from mild proximal limb weakness to severe generalized weakness and respiratory failure.4

Adapted from Hensel, et al. Front Neurol. 2020.

CNS, central nervous system; SMA, spinal muscular atrophy; SMN, survival motor neuron; SMN1, survival motor neuron 1.

Treatment of SMA involves many different types of healthcare specialists

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INDICATION

SPINRAZA® (nusinersen) is indicated for the treatment of spinal muscular atrophy (SMA) in pediatric and adult patients.

IMPORTANT SAFETY INFORMATION

Coagulation abnormalities and thrombocytopenia, including acute severe thrombocytopenia, have been observed after administration of some antisense oligonucleotides. Patients may be at increased risk of bleeding complications.

In the sham-controlled studies for patients with infantile-onset (Study 1) and later-onset (Study 2) SMA who received Low Dose Regimen (12 mg loading doses/12 mg maintenance doses), 24 of 146 SPINRAZA-treated patients (16%) with high, normal, or unknown platelet count at baseline developed a platelet level below the lower limit of normal, compared to 10 of 72 sham-controlled patients (14%). Two SPINRAZA-treated patients developed platelet counts <50,000 cells per microliter, with the lowest level of 10,000 cells per microliter recorded on study day 28. In patients who received High Dose Regimen (50 mg loading doses/28 mg maintenance doses), decreases in platelet counts were also observed.

Renal toxicity, including potentially fatal glomerulonephritis, has been observed after administration of some antisense oligonucleotides. SPINRAZA is present in and excreted by the kidney. In Study 1 and Study 2, 71 of 123 SPINRAZA-treated patients (58%) had elevated urine protein, compared to 22 of 65 sham-controlled patients (34%).

Laboratory testing and monitoring to assess safety should be conducted. Perform a platelet count, coagulation laboratory testing, and quantitative spot urine protein testing at baseline and prior to each dose of SPINRAZA and as clinically needed.

Severe hyponatremia was reported in an infant treated with SPINRAZA requiring salt supplementation for 14 months.

Cases of rash were reported in patients treated with SPINRAZA.

SPINRAZA may cause a reduction in growth as measured by height when administered to infants, as suggested by observations from the controlled study. It is unknown whether any effect of SPINRAZA on growth would be reversible with cessation of treatment.

The most common adverse reactions in the Low Dose Regimen (≥20% of SPINRAZA-treated patients and ≥5% more frequently than in control patients) that occurred in the infantile-onset controlled study were lower respiratory infection and constipation. Serious adverse reactions of atelectasis were more frequent in SPINRAZA-treated patients (18%) than in control patients (10%). Because patients in this controlled study were infants, adverse reactions that are verbally reported could not be assessed. The most common adverse reactions that occurred in the later-onset controlled study were pyrexia, headache, vomiting, and back pain. Post-lumbar puncture syndrome has also been observed after the administration of SPINRAZA.

The most common adverse reactions in the High Dose Regimen (≥10% of SPINRAZA-treated patients and ≥5% more frequently than control patients from Study 1) that occurred in patients with infantile-onset SMA were pneumonia, COVID-19, pneumonia aspiration, and malnutrition. COVID-19 was not discovered at the time of Study 1.

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As a courtesy, our full Prescribing Information is also available en Español. For prescribing decisions, please refer to official approved labeling.

References

1. National Institute of Neurological Disorders and Stroke. Spinal muscular atrophy fact sheet. https://www.ninds.nih.gov/health-information/disorders/spinal-muscular-atrophy. Reviewed March 13, 2026. Accessed March 19, 2026. 2. Stifani N. Motor neurons and the generation of spinal motor neuron diversity. Front Cell Neurosci. 2014;8:293. doi:10.3389/fncel.2014.00293 3. National Library of Medicine. MedlinePlus: SMN1 gene. Updated October 1, 2018. Accessed March 19, 2026. https://ghr.nlm.nih.gov/gene/SMN1 4. Arnold WD, Kassar D, Kissel JT. Spinal muscular atrophy: diagnosis and management in a new therapeutic era. Muscle Nerve. 2015;51(2):157-167. doi:10.1002/mus.24497 5. Hensel N, Kubinski S, Claus P. The need for SMN-independent treatments of spinal muscular atrophy (SMA) to complement SMN-enhancing drugs. Front Neurol. 2020;11:45. doi:10.3389/fneur.2020.00045

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