What Is Spinraza (Nusinersen)? Uses, Dosage, and What You Need to Know in 2026

Spinraza (nusinersen) is a prescription medication used to treat spinal muscular atrophy (SMA) in pediatric and adult patients. It was the first disease-modifying therapy approved for SMA, receiving FDA approval in December 2016, and has since transformed outcomes for patients with this rare and devastating neuromuscular disease. In March 2026, the FDA also approved a new High Dose Regimen, expanding the treatment options available to patients and providers.

This guide provides a comprehensive overview of Spinraza — what it is, how it works, who it's approved for, how it's given, and what you need to know as a patient or caregiver in 2026.

What Is Spinal Muscular Atrophy (SMA)?

Spinal muscular atrophy is a group of inherited neurological disorders caused by mutations in the SMN1 gene on chromosome 5q. This gene produces the survival motor neuron (SMN) protein, which is essential for the health of the motor neurons in the spinal cord that control muscle movement. Without adequate SMN protein, these neurons degenerate, causing progressive muscle weakness and wasting.

SMA affects approximately 1 in 10,000 newborns and is a leading genetic cause of infant death. It is classified into four main types based on age of onset and maximum motor milestones achieved — from the most severe Type 1 (infantile-onset, fatal without treatment before age 2) to the mildest Type 4 (adult onset, generally mild weakness).

What Is Spinraza?

Spinraza is the brand name for nusinersen, an antisense oligonucleotide (ASO) designed to treat SMA caused by mutations in the SMN1 gene. It is manufactured by Biogen and was developed in collaboration with Ionis Pharmaceuticals. Spinraza has orphan drug designation in the United States and the European Union, reflecting the rare nature of the disease it treats.

Rather than replacing the broken SMN1 gene, Spinraza works by modifying how the related but less-efficient SMN2 gene is processed — coaxing it to produce more full-length, functional SMN protein. This approach slows or stops the progression of motor neuron degeneration and can lead to meaningful improvements in motor function in many patients.

Who Is Spinraza Approved For?

Spinraza is FDA-approved for the treatment of SMA in pediatric and adult patients. It is approved for all types of SMA (Types 1, 2, 3, and 4) and for patients across all ages — from newborns identified through newborn screening before symptoms appear, to adults with later-onset SMA.

Research has consistently shown that the earlier treatment is initiated, the better the outcomes. In the NURTURE trial, infants who received Spinraza before developing symptoms showed the most dramatic improvements — with most achieving motor milestones not typically seen in untreated SMA patients.

How Is Spinraza Given?

Spinraza is administered as an intrathecal injection — directly into the cerebrospinal fluid (CSF) surrounding the spinal cord — via lumbar puncture. This allows the drug to reach the motor neurons in the spinal cord with maximum concentration. The injection is performed by a trained healthcare professional at a hospital or outpatient neurology clinic and typically takes 1 to 3 minutes.

Before the injection, 5 mL of CSF is removed from the patient. Ultrasound or fluoroscopic imaging guidance may be used, particularly for young infants or patients with spinal abnormalities. Sedation may be required for young infants.

Dosage and Dosing Schedule

There are now two approved dosing regimens for Spinraza as of 2026:

Low Dose Regimen (approved 2016):

Four 12 mg (5 mL) loading doses: doses 1, 2, and 3 given every 14 days; dose 4 given 30 days after dose 3

Maintenance: 12 mg (5 mL) once every 4 months (3 times per year) indefinitely

High Dose Regimen (FDA-approved March 30, 2026):

Two 50 mg (5 mL) loading doses given 14 days apart (accelerated loading phase)

Maintenance: 28 mg (5 mL) once every 4 months indefinitely

What Do the Clinical Trials Show?

Four major clinical trials supported the U.S. approval and ongoing use of Spinraza:

ENDEAR (Phase 3, Type 1 SMA): 51% of Spinraza-treated infants showed improved motor function vs. 0% in the sham group; 47% lower risk of death or permanent ventilation

CHERISH (Phase 3, later-onset SMA): 57% of treated children showed clinically meaningful motor improvements vs. 26% in the sham group

NURTURE (Phase 2, presymptomatic infants): Most presymptomatic infants treated early achieved motor milestones typical of typically developing children

DEVOTE (Phase 2/3, high-dose regimen): Treatment-naive infants showed 26.19-point mean CHOP-INTEND improvement at 6 months vs. sham control; supported 2026 high-dose approval

Important Monitoring Requirements

Before every Spinraza dose, your doctor must check platelet count and coagulation studies and urine protein levels. This monitoring is required because Spinraza carries risks of thrombocytopenia (low platelets) and kidney toxicity. Never skip pre-dose lab work.

Where to Access Spinraza

Spinraza is only available at certified treatment centers — it cannot be picked up at a retail pharmacy. medfinder is a paid service that helps patients find the right treatment centers and navigate the access process for specialty medications like Spinraza.

Want to understand the science behind how Spinraza works? See: How Does Spinraza Work? Mechanism of Action Explained.