On Mar. 30, 2026, Biogen announced that the High Dose Regimen of SPINRAZA^® (nusinersen), which is comprised of 50 mg/5 mL and 28 mg/5 mL doses, was approved by the U.S. Food and Drug Administration (FDA) for the treatment of spinal muscular atrophy (SMA).

Backed by more than 10 years of clinical data supporting the Low Dose Regimen of SPINRAZA (12 mg), High Dose SPINRAZA was designed to deliver a higher concentration of drug through both the loading and maintenance dosing phases, to provide a new option in response to the ongoing needs of the community.

The High Dose Regimen of SPINRAZA, which will be available in the coming weeks, enables an accelerated loading phase for those new to SPINRAZA treatment – with two 50 mg doses administered 14 days apart – followed by 28 mg maintenance dose injections every four months thereafter. Patients transitioning from the Low Dose Regimen would follow their existing dosing schedule at four-month intervals after a single High Dose loading phase.

The FDA approval is based on data from the three-part, Phase 2/3 DEVOTE study. Results from the pivotal cohort of the study showed treatment-naïve, symptomatic infants who received High Dose SPINRAZA experienced statistically significant improvements in motor function as measured by the Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND), when compared to a prespecified matched sham (untreated) group from the ENDEAR study* (mean difference: 26.19 points; +15.1 vs. -11.1, p<0.0001).

In the DEVOTE study, the safety profile of the High Dose Regimen of SPINRAZA was generally consistent with the known safety of the Low Dose Regimen. The most common adverse reactions occurring in at least 10% of SPINRAZA-treated patients who received the High Dose Regimen and occurred at least 5% more frequently than in historic matched sham-control were: pneumonia, COVID-19, pneumonia aspiration, and malnutrition in patients with infantile-onset SMA. COVID-19 was not discovered at the time of ENDEAR, the study from which the matched sham-control was taken.