Biogen’s antisense oligonucleotide (ASO), salanersen, is advancing to Phase III trials after it showed benefit with a lower dosing schedule than Spinraza (nusinersen) in patients with spinal muscular atrophy (SMA).
Leveraging the same mechanism of action as Spinraza but designed to achieve greater potency, Biogen believes that salanersen has the potential to achieve high efficacy while enabling once yearly dosing. Meanwhile, Spinraza is dosed once every four months.
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Interim analysis of the Phase I study (NCT05575011) found that both dose levels tested, 40mg and 80mg, given once a year, were generally well-tolerated and led to substantial slowing of neurodegeneration. This was shown by a 70% mean reduction in neurofilament light chain (NfL) at six months.
Half of the patients dosed with salanersen achieved new WHO motor milestones that they previously could not achieve on their own or required assistance to do, such as walking, crawling, standing, or sitting. These patients also experienced clinically meaningful improvements in motor function from baseline to one year, including a 3.3-point mean improvement from baseline on the Hammersmith Functional Motor Scale – Expanded (HFMSE) and a 5.3-point improvement on the Revised Upper Limb Module (RULM).
Salanersen was generally well tolerated in both doses, with most adverse events (AEs) mild to moderate in severity. The most common AEs were pyrexia and upper respiratory tract infection.
The interim analysis comes from Part B of the study, an open-label segment that enrolled paediatric SMA patients who previously received Novartis’ Zolgensma (onasemnogene abeparvovec) and had investigator-reported suboptimal clinical status.
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By GlobalDataThe data is set to be presented at the SMA Research & Clinical Care Meeting hosted by Cure SMA in Anaheim, California, on 25 June.
Biogen preps salanersen for Phase III in SMA
Biogen is now engaging with global health authorities to initiate Phase III studies. Biogen licensed the global development, manufacturing and commercialisation rights for salanersen from Ionis Pharmaceuticals. This is the second SMA collaboration between the pair, with Spinraza also originally coming from Ionis.
GlobalData analysis shows that Spinraza made $1.57bn in sales in 2024, with 2030 sales projected to reach $1.19bn. This drop in sales is due in part to the therapy losing its US exclusivity in December 2023.
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Principal investigator for the salanersen Phase I trial and Clinical Center NeMO’s clinical and scientific director Dr Valeria A Sansone said: “Of the data generated, to me, it is neurofilament and the WHO milestones that are most easily interpretable, given these children had previously received gene therapy. To see a child dosed with gene therapy at one year of age and still unable to sit without support at age five, then gain the ability to sit independently just three months after initiating salanersen, that is unexpected.”
SMA is a rare, genetic and neuromuscular disease that affects patients of all ages. It is characterised by a loss of motor neurons in the spinal cord and lower brain stem, resulting in progressive muscle atrophy and weakness.
Roche’s Evrysdi (risdiplam) is also approved for use in SMA, having gained US Food and Drug Administration (FDA) approval in August 2020. Scholar Rock’s apetigromab has received priority review from the FDA with a Prescription Drug User Fee Act (PDUFA) target action date of 22 September 2025.
According to GlobalData analysis, the SMA market across the seven major markets (7MM: France, Germany, Italy, Japan, Spain, the UK and the US) is set to grow from $2.7bn in 2023 to $3bn in 2033.
