Spinraza (nusinersen) is an injectable drug used to treat a rare and often fatal hereditary disorder known as spinal muscular atrophy (SMA). Spinraza is able to slow the progressive loss of muscle control, increases survival times, and improve motor function by as much as 51% in people affected by the disease.1
Spinraza is delivered by routine injections into the fluid surrounding the spinal cord. Common side effects include upper and lower respiratory infections.
Spinraza is the first drug approved by the U.S. Food and Drug Administration (FDA) to treat SMA. It is costly—with an estimated price tag of $750,000 for the first year and $375,000 for every year thereafter.2 However, Spinraza may be available free of charge for those who qualify for financial assistance. Spinal muscular atrophy (SMA) is a rare disorder, affecting roughly one of every 11,000 births.
Spinraza is a form of gene therapy that treats all types of SMA in children and adults. SMA is caused by genetic mutations that impair the production of a protein called survival motor neuron (SMN). Without enough SMN to keep spinal neurons alive and functioning, individuals with SMA can experience a loss of muscle control, muscle wasting, and impaired respiratory function.4
Spinraza works by stimulating a closely related gene not affected by SMA. Without Spinraza, this related gene cannot produce enough SMN to supply the body; with Spinraza, beneficial levels can be achieved.
Spinraza is approved for the treatment of the four classifications of SMA:5
Type 1 SMA, also called Werdnig-Hoffmann disease, is the most severe form of SMA, and it is usually evident at or soon after birth. Children with this type usually have a limited ability to move or sit and difficulty breathing and swallowing. Death usually occurs before the age of 2 years.
Type 2 SMA is the intermediate form of SMA. The legs tend to be affected more than the arms. Life expectancy can range from early childhood to adulthood, depending on the severity of symptoms.
Type 3 SMA, also called Kugelberg-Welander syndrome or juvenile spinal muscular atrophy, is a mild form of SMA that can strike anytime from childhood to adulthood. People with this type have a hard time rising from a seated position, although life expectancy is usually not affected.
Type 4 SMA does not manifest until the second or third decade of life, during which time muscle weakness may slowly progress along with other SMA symptoms.
Current evidence suggests that the response to treatment is greater when Spinraza is started soon after diagnosis rather than later. This especially true with type 1 SMA.
Spinraza is used in the first-line treatment of SMA. There are currently no contraindications for the use of the drug.
However, the FDA recommends that baseline tests be taken before treatment to evaluate kidney enzymes, platelet counts, and blood clotting times. This allows doctors to monitor for kidney toxicity or impaired clotting that can affect some users.
Spinraza is the first, but not only, gene therapy used to treat SMA. Another, called Zolgensma (onasemnogene abeparvovec), may be used in children under age 2 years, although its price tag—roughly $2 million for a once-off infusion—may limit its approval by health insurers.
Spinraza is available in 5-milliliter (mL), single-dose vials for intrathecal injection (injection into the cerebrospinal fluid that surrounds the spinal cord). Each 5-mL vial contains 12 milligrams (mg) of nusinersen.
The recommended dosage of Spinraza for children and adults is 12 mg per injection.5
Spinraza requires an induction (loading) dose involving four separate injections. The first three are delivered in 14-day intervals. The fourth is given no less than 30 days after the third injection. Thereafter, a maintenance dose is delivered every four months.
How to Take and Store
Spinraza is administered in a hospital, surgery center, or doctor's office by a healthcare professional experienced in lumbar punctures (spinal taps).
A local anesthetic is used to numb the injection site. An ultrasound may be needed to correctly place the needle in infants, smaller children, or people with spinal deformity.
If a Spinraza dose is missed, it needs to given as soon as possible. Every effort should be made to keep to the prescribed schedule to ensure optimal results.
Spinraza is stored in a refrigerator (2C to 8C / 36F to 46F) and allowed to return to room temperature (77 F / 25 C) before the shot is given. The responsible health provider is tasked with storing and administering the drug. Spinraza should be stored in the original carton. If it is removed from the original carton, time out of refrigeration should not exceed 30 hours at room temperature.
Spinraza may cause side effects, most notably respiratory infections. Some of the side effects are manageable, while others may require the termination of treatment.
Common side effects of Spinraza (affecting no less than 5% of users) include:5
Lower respiratory infections (including pneumonia, bronchitis, and bronchiolitis)
Upper respiratory infections (including the common cold, non-allergic rhinitis, pharyngitis, and tracheitis)
Injection site pain
Drug rashes have also been known to occur, although they tend to be low-grade and resolve on their own without treatment.
Less commonly, Spinraza can impair blood clotting and lead to a condition known as thrombocytopenia (low platelets). Most cases are relatively mild with platelet counts rarely falling below 50,000 even with ongoing use.5 Even so, treatment will need to be stopped if the symptoms and/or decline in platelet numbers are severe.
Observational studies have suggested that Spinraza may impede the height of growing infants. It is unclear, however, if stopping the drug will remedy the impairment.8
More concerning, Spinraza may interfere with spinal formation in some children. One such manifestation is scoliosis, an abnormal curvature of the spine, which affects up to 5% of Spinraza users.5
Although severe scoliosis is rare with Spinraza use, any abnormality in the spine can complicate the intrathecal administration of the drug.
Kidney toxicity is another concern. Because Spinraza is excreted from the body in urine, it can sometimes damage the delicate filters of the kidneys called the glomeruli. In some cases, this can lead to a potentially fatal condition known as glomerulonephritis.5
To avoid drug toxicity, your doctor will monitor your renal function, most especially elevations in the amount of protein in your urine (a key indicator of glomerular impairment).
Warnings and Interactions
Although there are no adequate human studies investigating the use of Spinraza during pregnancy, there were no signs of fetal harm in pregnant mice or rabbits given Spinraza injections.5
Because it is unknown if nusinersen can be passed to babies in breast milk, speak with your doctor to weigh the benefits and risks of breastfeeding before starting Spinraza therapy.
Spinraza is not believed to have any significant drug-drug interactions due to its minimal effect on cytochrome P450 (an enzyme involved in drug metabolization).9
How to Access Manufacturer Drug Assistance
Generally, anyone with non-government insurance is eligible for $0 copay assistance, regardless of income. Spinraza may be offered free of charge to eligible individuals without insurance.