The FDA rejected the high-dose regimen of Spinraza in September last year due to manufacturing concerns.
After a surprise rejection in September last year, the FDA has signed off on a high-dose formulation of Biogen’s spinal muscular atrophy drug Spinraza.
The approval, announced Monday, will allow a quicker loading phase for patients new to Spinraza treatment. Instead of four induction doses with the original 12-mg formulation, the newly approved version will only require patients to receive two 50-mg loading doses 14 days apart, followed by 28-mg maintenance injections every four months.
Biogen will make high-dose Spinraza available “in the coming weeks,” according to the company’s news release.
High-dose Spinraza “could help sustain sales, effectively bridging [Biogen’s] $1.5B+ SMA franchise toward next-gen salanersen,” analysts at Jefferies wrote in a Monday note, referring to Biogen’s investigational antisense oligonucleotide, which is currently in Phase 1b development. Late-stage data for salanersen could come as early as 2028, Jefferies estimated.
BMO Capital Markets expressed a similar sentiment in its own note to investors Monday morning. “While we are more interested in future updates from the company’s next-generation salanersen agent, approval of high-dose Spinraza is a meaningful first step in continuing to stabilize and grow the company’s SMA products.”
Spinraza was approved in December 2016 and quickly became a top-selling product for Biogen, reaching its peak in 2019 when it earned $2.097 billion. Sales have since slowed down, slumping to below $1.55 billion in 2025, the year that Roche received FDA approval for an oral formulation of its SMA drug Evrysdi. The high-dose approval of Spinraza could help bolster those numbers, CEO Chris Viehbacher said during the company’s fourth quarter earnings call in February, according to reporting from Fierce Pharma.
“Following increasing competition, a high-dose Spinraza approval could reinvigorate Biogen’s SMA franchise,” BMO wrote.
If that pans out, Spinraza could also help Biogen build what Viehbacher called the company’s “bridge to growth.” Positive late-stage readouts and successful product launches form the foundation of this bridge, as do carefully constructed acquisition deals.
Monday’s approval was backed by data from the Phase 2/3 DEVOTE study, which found that the higher-dose drug led to significantly better motor skill outcomes than a sham control, according to a September 2024 readout. The high dose regiment also led to motor improvements over standard-dose Spinraza, though the difference did not reach statistical significance.
Biogen presented updated data from DEVOTE earlier this month at the 2026 congress of the Muscular Dystrophy Association, not only confirming the high-dose regimen’s significant motor benefits over sham, but also touting improvements in terms of event-free survival and neurofilament light chain levels.
The approval of high-dose Spinraza “builds on a therapy that we already know can change lives,” Richard Finkel, director of the Center for Experimental Neurotherapeutics (CENT) at St. Jude Children’s Research Hospital, said in a statement on Monday, adding that the high dose regiment demonstrated “meaningful clinical benefit” while maintaining a well characterized safety profile. Finkel has previously received research funding from Biogen and has been compensated by the company in the past for serving as a scientific advisor.
Spinal muscular atrophy is a genetic disorder characterized by progressive muscle weakness. The condition is caused by mutations to the SMN1 gene, resulting in faulty or deficient levels of the SMN protein. Spinraza, an antisense oligonucleotide therapeutic, works by targeting a similar gene present in these patients, called SMN2, in turn promoting the production of functional SMN.
