Salanersen granted FDA breakthrough therapy designation for spinal muscular atrophy

Biogen has recently announced that the U.S. FDA has granted salanersen Breakthrough Therapy Designation for the treatment of spinal muscular atrophy. This designation is a formal process intended to accelerate the development and regulatory review of therapies targeting serious conditions, where early clinical evidence suggests the treatment may offer substantial improvement over existing options on clinically significant endpoints. Salanersen is an investigational novel antisense oligonucleotide with the potential to deliver high efficacy in SMA through a once-yearly dosing regimen.

“The FDA’s designation of salanersen as a breakthrough therapy recognizes that there is continued unmet need in spinal muscular atrophy, and there is more that can be done for people impacted by the disease,” said Diana Castro, M.D., of the Neurology Rare Disease Center in Flower Mound, Texas. “In the Phase 1b study of salanersen, we saw unexpected improvements on exploratory endpoints in children previously dosed with gene therapy who gained critical functions, such as sitting and walking, after receiving salanersen. We are excited about the potential of salanersen and eager to help advance the Phase 3 program.”

The FDA’s decision draws on data from the Phase 1b study of salanersen, findings from which were recently presented at both the 2026 Muscular Dystrophy Association (MDA) Clinical & Scientific Conference and the 5th International Scientific Congress on SMA (SMA Europe 2026). Following initiation of once-yearly salanersen in children with SMA who had experienced a suboptimal response to prior gene therapy, clinically meaningful improvements in motor function were observed, alongside a slowing of neurodegeneration as indicated by reduced neurofilament levels. Salanersen was generally well-tolerated throughout the study.

“This designation reflects the FDA’s continued commitment to SMA and its recognition of the potential meaningful impact salanersen may offer,” said Kenneth Hobby, President of Cure SMA. “It affirms what our SMA community has recently communicated to the agency: urgent, unmet needs remain, and promising therapies deserve a rapid path forward.”

“This designation reflects the FDA’s determination that salanersen has the potential to demonstrate substantial improvement over available therapies,” said Stephanie Fradette, Pharm.D., Head of the Rare Neurology Development Unit at Biogen. “This is a significant milestone for our SMA portfolio as we advance the Phase 3 studies designed to establish the role of salanersen in the future SMA treatment landscape.”

The salanersen Phase 3 program comprises three global studies:

• STELLAR-1 (currently recruiting) — an open-label study evaluating the effects of salanersen in young, treatment-naïve, and clinically presymptomatic infants under six weeks of age with a genetic diagnosis of SMA
• SOLAR (currently recruiting) — an open-label study evaluating the effects of salanersen in adolescents and adults aged 15–60 years with SMA who are either treatment-naïve or have previously received risdiplam
• STELLAR-2 (recruitment anticipated to begin June 2026) — a randomized, double-blind, sham-controlled study evaluating the effects of salanersen when initiated approximately six months after onasemnogene abeparvovec-xioi in infants with SMA who received presymptomatic gene therapy at six weeks of age or younger

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Related Topics and Keywords

biogen, FDA Approval, Salanersen, spinal muscular atrophy