The headline

At the 2026 SMA Congress (Budapest, O38), Thomas Crawford (Johns Hopkins) presented Phase 1 interim data and the Phase 3 design for salanersen (BIIB115) — Biogen's next-generation antisense oligonucleotide successor to nusinersen (Spinraza).

Why it matters

Nusinersen's limitations are well known: intrathecal dosing every 4 months, fixed CSF exposure, plateauing gains in treatment-experienced patients. Salanersen is engineered for longer dosing intervals and higher CSF exposure, with the potential to serve both nusinersen-experienced and nusinersen-naive patients.

Positioning

• Drug type: 2'-MOE antisense oligonucleotide (same chemistry class as nusinersen)
• Target: SMN2 pre-mRNA ISS-N1 region (exon 7 inclusion)
• Phase: 3 trial design presented
• Manufacturer: Biogen

In-platform

Added to /drugs as salanersen (phase3, Biogen). Linked to SMN2 target.

Context

Salanersen is the third major pipeline pivot the SMA field has seen in 2026 alongside the argenx NMJ axis (ARGX-119) and the redox axis (omaveloxolone in Friedreich, now proposed for SMA). Together these suggest the field is moving past a pure "first-gen fix everything" era into rational combinations.

See our 3-mechanism combo memo for how we think about stacking these.