Biogen has revealed compelling new results from its Phase 1b study of salanersen, an investigational once-yearly antisense oligonucleotide (ASO) for spinal muscular atrophy (SMA), at the 2026 Muscular Dystrophy Association Clinical & Scientific Conference. 

 

The study focused on children whose clinical status remained suboptimal despite prior gene therapy with onasemnogene abeparvovec-xioi.

 

Salanersen was generally well-tolerated, slowed neurodegeneration, and enabled functional gains—including new World Health Organization (WHO) motor milestones. The results reflect at least one year of follow-up for all participants and expand upon earlier interim findings presented at Cure SMA 2025. Biogen also introduced the design of its global Phase 3 clinical trial program for salanersen.

 

“Spinal muscular atrophy has benefitted from extraordinary therapeutic progress, but across the treatment landscape there remains room for improvement. There is growing scientific and clinical enthusiasm about the advances that salanersen offers,” said Thomas Crawford, co-director, Muscular Dystrophy Association Clinic at Johns Hopkins Medicine. 

 

“These additional Phase 1 data add confidence in the emerging salanersen clinical profile. We have more reason to look forward to results of the Phase 3 program."

 

The analysis included 24 children, ages 6 months to 12 years, who had received at least two doses of salanersen (40 mg or 80 mg). Participants with elevated baseline neurofilament light chain (NfL) levels—a marker of ongoing neurodegeneration—showed a 75% reduction at six months, sustained throughout follow-up.

 

“With the encouraging Phase 1b results in hand, we are initiating the Phase 3 STELLAR-1, STELLAR-2, and SOLAR salanersen studies as quickly as possible,” said Stephanie Fradette, Head of the Neuromuscular Development Unit at Biogen. “Together with the SMA community, we have designed these studies to confidently answer the most relevant questions for the field and establish salanersen’s role in the future treatment landscape.”