Biogen's salanersen earns FDA Breakthrough Therapy Designation for SMA

The U.S. Food and Drug Administration (FDA) has granted Breakthrough Therapy Designation to salanersen (BIIB115), an investigational therapy from Biogen, the company announced on June 4, 2026.

Salanersen is an antisense oligonucleotide (ASO) that boosts production of the SMN protein by correcting SMN2 pre-mRNA splicing. The designation is supported by exploratory Phase 1b findings: some children with SMA who had previously received gene therapy but remained clinically suboptimal showed improved motor function and signs of slowed neurodegeneration after treatment with salanersen.

The Phase 3 program includes three global studies — STELLAR-1, SOLAR and STELLAR-2. Enrollment in STELLAR-2 is expected to begin in June 2026, evaluating salanersen in infants roughly six months after onasemnogene abeparvovec gene therapy. Source: Biogen, SMA News Today.