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Zolgensma vs Spinraza: What are the key differences?

Medically reviewed by Philip Thornton, DipPharm. Last updated on Dec 12, 2022.

Official answer


Zolgensma (onasemnogene abeparvovec-xioi) and Spinraza (nusinersen sodium) are both treatments for people with spinal muscular atrophy (SMA).

SMA is a type of motor neuron disease. It is caused by a mutation in the SMN1 (survival motor neuron 1) gene, which is responsible for producing the SMN protein that keeps motor neurons healthy and functioning. If enough SMN protein is not produced then the spinal cord ceases to be able to transmit signals from the brain to the muscles.

Functional SMN protein is also produced in small amounts by the SMN2 gene, a back up gene. However, production of SMN protein by the SMN2 gene can’t fully compensate for a faulty SMN1 gene.

5 key differences between Zolgensma and Spinraza

  1. Uses / indication. Zolgensma and Spinraza are both used to treat SMA, but Zolgensma is only approved for use in patients less than two years of age, whereas Spinraza is approved for use in pediatric and adult patients.
  2. Frequency of treatment. Zolgensma is a one-off treatment, whereas Spinraza requires four loading doses and then a maintenance dose needs to be given once every four months. The first three loading doses are given at 14 day intervals and the fourth dose is given 30 days after the third.
  3. Type of drug. Zolgensma is an adeno-associated virus vector-based gene therapy and Spinraza is a survival motor neuron-2 (SMN2)-directed antisense oligonucleotide.
  4. How the treatment works - mechanism of action. Zolgensma delivers a copy of the gene encoding the human SMN protein, which enables the patient to make the SMN protein they are lacking.

    Spinraza, on the other hand, makes the SMN protein produced by the SMN2 gene functional. Spinraza works by fixing a mistake - RNA splicing error - that leads to exon 7 being skipped and a faulty protein being produced by SMN2. By rebinding at exon 7 - enhancing the inclusion of exon 7 into the SMN protein - the protein produced by SMN2 functions like that produced by SMN1.
  5. How well it works - efficacy. An indirect comparison of the two treatments indicates that Zolgensma may be more effective than Spinraza among infants with symptomatic SMA type 1 in terms of overall survival, independence from permanent assisted ventilation, motor function and motor milestones. Both treatments offer significant benefits over having no treatment at all, which typically meant that patients would not survive beyond two years of age.

The table below also provides details of other important aspects for both treatments.

Zolgensma vs Spinraza - other factors

(onasemnogene abeparvovec-xioi)


(nusinersen sodium)

Company Novartis Gene Therapies (formerly AveXis) Biogen
Approval year - US Food and Drug Administration (FDA) 2019 2016
Dosage form A suspension for infusion that comes as single-use vials. A kit is supplied containing two to nine vials A solution for injection that comes in a single-dose vial
Administration Intravenous (IV) infusion over 60 minutes Intrathecal injection (injection into the subarachnoid space of the spinal cord/the cerebrospinal fluid)
Side effects / adverse effects The most common adverse events occurring in ≥ 5% of patients include:
  • Elevated aminotransferases
  • Vomiting
The most common adverse reactions occurring in at least 20% of patients and at a frequency of at least 5% more than controls who didn’t receive Spinraza include:
  • Lower respiratory infection and constipation in patients with infantile-onset SMA
  • Pyrexia, headache, vomiting and back pain in patients with later-onset SMA
Warnings and precautions
  • Thrombocytopenia - platelet counts need monitoring before treatment and for three months after
  • Elevated troponin-I - monitor levels before and for three months after
Requires baseline tests before each administration because of thrombocytopenia and coagulation abnormalities and renal toxicity
Special patient populations Not recommended for preterm infants May cause fetal harm


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