Biogen has announced that salanersen has been given the US FDA Breakthrough Therapy Designation to treat spinal muscular atrophy (SMA).Salanersen is an investigational novel antisense oligonucleotide (ASO) and has the potential to offer high efficacy in SMA with once-yearly dosing.
Breakthrough Therapy designation helps to speed up the development and review of drugs intended to treat serious conditions, and where preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over available therapy on a clinically significant endpoint(s).
Diana Castro, from the Neurology Rare Disease Center in Flower Mound, Texas, said: “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.
“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.”
The FDA’s decision is based on data from the phase 1b study of salanersen, which were recently presented at the 2026 Muscular Dystrophy Association (MDA) Clinical & Scientific Conference and the 5th International Scientific Congress on SMA (SMA Europe 2026). After initiation of once-yearly salanersen in children with SMA who had a suboptimal response to prior gene therapy, clinically meaningful improvements in motor function were observed as well as slowing of neurodegeneration, as measured by reduced neurofilament levels. Salanersen was generally well-tolerated in the study.
Stephanie Fradette, Head of the Rare Neurology Development Unit at Biogen, said: ”This designation reflects the FDA’s determination that salanersen has the potential to demonstrate substantial improvement over available therapies. 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.”