Spinraza (nusinersen)

Reviewed by: HU Medical Review Board | Last reviewed: April 2023

In 2016, Spinraza® (nusinersen) became the first drug approved by the U.S. Food and Drug Administration (FDA) to treat children and adults with spinal muscular atrophy (SMA). It works by increasing the ability of motor neurons to produce the “survival of motor neuron” (SMN) protein.1

In clinical trials, infants and children treated with Spinraza show improvements in motor function and survival rate. Health outcomes are even better when treatment is started earlier.2-5

What are the ingredients in Spinraza?

The active ingredient in Spinraza is nusinersen.6

How does it work?

Nusinersen, the active ingredient of Spinraza, is an “antisense oligonucleotide” (ASO). ASOs are drugs that have a similar chemical structure to our DNA. They change how our cells use genetic material to make a certain protein.1

Spinraza improves the ability of motor neurons to produce the “survival of motor neuron” (SMN) protein from the back-up SMN2 gene. It does this by changing how the SMN2 gene is processed. This helps keep motor neurons alive and prevent muscle wasting.6,7

One way to imagine this is that the SMN2 gene is a recipe for your cells to make the SMN protein. But it has important instructions missing, which makes the recipe unreadable. Spinraza makes the recipe readable by fixing how motor neurons process the SMN2 gene.

Spinraza and other ASOs cannot reach the motor neurons in the spine from the bloodstream. This is why Spinraza must be injected directly into the spine. This may cause problems for people who have had spinal fusion surgery.1

What are possible side effects of this treatment?

The most common side effects of Spinraza in infants include:6

  • Lower respiratory infection
  • Constipation
  • Teething
  • Urinary tract infection
  • Ear infection

The most common side effects of Spinraza in older children include:6

  • Fever
  • Headache
  • Vomiting
  • Back pain

Spinraza may cause bleeding disorders in some people. This can happen because of a low number of platelets. Platelets are blood cells that are needed for blood to clot in response to bleeding. Doctors may perform blood tests to monitor your platelet count while taking Spinraza.6,7

Spinraza may also cause kidney problems in some people. One sign of kidney problems is high amounts of protein in urine (proteinuria). Doctors may perform urine tests to monitor urine protein levels in people taking Spinraza.6,7

These are not all the possible side effects of Spinraza. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with Spinraza.

Things to know about Spinraza

Spinraza is given by an injection into the spine. Treatment usually starts with 4 doses within 2 months. After that, 1 dose is given every 4 months. Delayed or missed doses should usually be given as soon as possible.6

The cost of each dose is about $125,000. This makes the yearly cost around $750,000 for the first year and around $375,000 every year afterward. Most families must rely on insurance coverage or payment assistance programs to afford Spinraza.8

The high price limits the cost-effectiveness for many people with SMA. This is especially true for older children and adults with SMA who may not benefit as much from Spinraza. For example, some adults with SMA would prefer to receive a similar amount of money for wheelchairs, transportation, and other resources.8

Before beginning treatment for SMA, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

For more information, read the full prescribing information of Spinraza.


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