Salanersen Receives FDA Breakthrough Therapy Designation for Spinal Muscular Atrophy

The Food and Drug Administration (FDA) has granted Breakthrough Therapy designation to salanersen (BIIB115; Biogen, Cambridge, MA), an agent under investigation for the treatment of spinal muscular atrophy (SMA). The designation is intended to expedite development and review of therapies for serious conditions when preliminary clinical evidence suggests potential substantial improvement over available treatment on clinically significant end points.

Salanersen is an intrathecally administered antisense oligonucleotide (ASO) designed to correct splicing of SMN2 pre-mRNA and increase production of survival motor neuron (SMN) protein. Biogen stated that the company is developing the therapy with once-yearly dosing, and phase 3 studies will evaluate an 80-mg annual dose across a broad SMA population.

Data Supporting the Designation

The FDA decision was based on findings from a phase 1b study of salanersen in children with SMA, including participants previously treated with gene therapy who had suboptimal clinical status. The data were presented at the 2026 Muscular Dystrophy Association Clinical & Scientific Conference and the 5th International Scientific Congress on SMA.

• The phase 1b study included 24 participants aged 0.5 to 12 years who received at least 2 doses of salanersen at 40 mg or 80 mg.
• Among participants with elevated baseline neurofilament light chain (NfL), reductions of 75% in NfL levels were observed at 6 months and were sustained during follow-up.
• All 24 participants had increases from baseline on at least 1 study end point.
• Twelve participants achieved at least 1 new World Health Organization motor milestone.
• All participants maintained the motor milestones documented at baseline.

Salanersen was generally well tolerated at both evaluated dose levels. Most adverse events were mild to moderate. The most common adverse events were upper respiratory tract infection and vomiting in the 40-mg group and pyrexia and upper respiratory tract infection in the 80-mg group.

Phase 3 Program

Biogen’s salanersen phase 3 program includes 3 global studies:

• STELLAR-1 (NCT07221669) is an open-label study evaluating salanersen in treatment-naïve, clinically presymptomatic infants younger than 6 weeks with a genetic diagnosis of SMA, with recruiting underway.
• SOLAR (NCT07444476) is an open-label study evaluating salanersen in teens and adults aged 15 to 60 years who are treatment-naïve or previously treated with risdiplam, which is currently recruiting.
• STELLAR-2 (NCT07444450), expected to begin recruitment in June 2026, is a randomized, double-blind, sham-controlled study evaluating salanersen initiated approximately 6 months after onasemnogene abeparvovec-xioi in infants treated presymptomatically with gene therapy at 6 weeks of age or younger.

Salanersen remains investigational and has not been approved by the FDA. Biogen licensed global development, manufacturing, and commercialization rights for salanersen from Ionis Pharmaceuticals, which discovered the therapy.

Source

Biogen. Biogen’s salanersen receives FDA Breakthrough Therapy designation for spinal muscular atrophy. Published June 4, 2026. Accessed June 8, 2026. https://investors.biogen.com/news-releases/news-release-details/biogens-salanersen-receives-fda-breakthrough-therapy-designation