On June 25, 2025, Ionis Pharmaceuticals, Inc. announced that its partner, Biogen Inc., will advance salanersen (ION306/BIIB115) into registrational studies for the potential treatment of spinal muscular atrophy (SMA). This decision is based on positive topline interim results from the Phase 1 study of salanersen, an investigational antisense oligonucleotide (ASO).
Salanersen, which leverages the same mechanism of action as SPINRAZA® (nusinersen) but is designed for greater potency, demonstrated the potential for high efficacy and once-yearly dosing. Interim data from Part B of the Phase 1 study (n=24) in pediatric participants with SMA, who had previously received ZOLGENSMA® (onasemnogene abeparvovec) and had suboptimal clinical status, showed substantial slowing of neurodegeneration.
Specifically, participants with elevated baseline neurofilament light chain (NfL) experienced a mean reduction of 70% in NfL at six months, sustained through the one-year dosing interval. Exploratory clinical outcome data also showed clinically meaningful improvements in motor function, including a 3.3-point mean improvement on the Hammersmith Functional Motor Scale – Expanded (HFMSE) and a 5.3-point improvement on the Revised Upper Limb Module (RULM). Biogen is now engaging with global health authorities to design the Phase 3 studies, aiming to address critical unmet needs in the SMA community.
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