Biogen to Advance Investigational Spinal Muscular Atrophy Asset to Registrational Studies Based on Positive Interim Phase 1 Results

• Salanersen (BIIB115/ION306) is a novel antisense oligonucleotide (ASO) with the potential to achieve high efficacy and once yearly dosing in spinal muscular atrophy (SMA)
• Interim Phase 1 data show children with SMA previously treated with gene therapy experienced a substantial slowing of neurodegeneration and clinically meaningful improvements in motor function following initiation of salanersen
• Based on these encouraging Phase 1 data, Biogen is engaging with regulators to advance salanersen to registrational stage studies, building on extensive experience in SMA
  

CAMBRIDGE, Mass., June 25, 2025 (GLOBE NEWSWIRE) -- Biogen Inc. (Nasdaq: BIIB) announced topline results from the Phase 1 study of salanersen (BIIB115/ION306), an antisense oligonucleotide (ASO) being developed for the treatment of spinal muscular atrophy (SMA). Leveraging the same mechanism of action as SPINRAZA (nusinersen) but designed to achieve greater potency, salanersen has the potential to achieve high efficacy and enable once yearly dosing. An interim analysis of the Phase 1 study in participants with SMA who were previously treated with gene therapy was conducted to inform the decision on whether to move salanersen forward into registrational studies. Both dose levels tested, 40 mg and 80 mg, given once a year, were generally well-tolerated and led to substantial slowing of neurodegeneration, as shown by reductions in neurofilament. Exploratory clinical outcome data shows clinically meaningful improvements in function and attainment of new World Health Organization (WHO) milestones over 1 year. These data will be presented today at the SMA Research & Clinical Care Meeting hosted by Cure SMA in Anaheim, Calif.

“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 3 months after initiating salanersen, that is unexpected,” said Valeria A. Sansone, M.D., Ph.D., Clinical and Scientific Director at the Clinical Center NeMO in Milan, Professor of Neurology, University of Milan, and a principal investigator for the salanersen Phase 1 trial. “Given these are early data from a relatively small cohort, I am looking forward to further understanding the effects that salanersen can have in both previously treated and treatment-naïve individuals in the upcoming Phase 3 studies.”  

The Phase 1 single ascending dose study was designed to evaluate the safety, tolerability and pharmacokinetics of salanersen. The trial consisted of two parts: Part A, a randomized and placebo-controlled segment in healthy adult male volunteers and Part B, an open-label segment in pediatric participants with SMA who previously received ZOLGENSMA^® (onasemnogene abeparvovec) and had investigator-reported suboptimal clinical status. Interim results are from Part B (n=24) in individuals that received either 40 mg or 80 mg salanersen once a year. In participants with elevated baseline concentrations of neurofilament light chain (NfL), indicating ongoing neurodegeneration, initiation of salanersen led to mean reductions in NfL of 70% at 6-months which were sustained through the 1-year dosing interval.

“Despite the remarkable therapeutic advancements in the field of SMA over the past decade, there remains critical unmet needs. Salanersen represents the next phase of Biogen's ongoing pursuit to address these needs,” said Stephanie Fradette, Pharm.D., Head of the Neuromuscular Development Unit at Biogen. “We are encouraged by the available data and eager to move salanersen into the next stage of development as quickly as possible. We are deeply grateful for the trial participants and their families, investigators, and site staff.”

In addition to safety and NfL, exploratory clinical outcome data were evaluated for the subgroup of participants with at least one year of follow-up at the time of the interim analysis (n=8 participants aged 2-12 who received 40 mg of salanersen). Half (4/8) of these participants 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. Furthermore, these participants experienced clinically meaningful improvements in motor function from baseline to 1-year, including a 3.3-point (SD 4.46) mean improvement from baseline on the Hammersmith Functional Motor Scale – Expanded (HFMSE) and a 5.3 point (SD 4.75) improvement on the Revised Upper Limb Module (RULM).

The cumulative data from the Phase 1 study indicate that salanersen has a generally well tolerated safety profile at both the 40 mg and 80 mg doses, with most adverse events (AEs) mild to moderate in severity. The most common AEs were pyrexia and upper respiratory tract infection.

Biogen is currently engaging with global health authorities regarding the design of the Phase 3 studies. Biogen licensed the global development, manufacturing and commercialization rights for salanersen from Ionis Pharmaceuticals, Inc. Salanersen was discovered by Ionis.

About Spinal Muscular Atrophy (SMA)
SMA is a rare, genetic, neuromuscular disease that affects individuals of all ages. It is characterized by a loss of motor neurons in the spinal cord and lower brain stem, resulting in progressive muscle atrophy and weakness.¹ SMA is caused by a deficiency in the production of survival motor neuron (SMN) protein due to a damaged or missing SMN1 gene, with a spectrum of disease severity.¹ Some individuals with SMA may never sit; some sit but never walk; and some walk but may lose that ability over time.² In the absence of treatment, children with the most severe form of SMA would usually not be expected to reach their second birthday.¹

SMA impacts approximately 1 in 10,000 live births,^3-6 is a leading cause of genetic death among infants⁷ and causes a range of disability in teenagers and adults.²

About SPINRAZA
SPINRAZA (nusinersen) 12mg/5 mL injection is approved in more than 71 countries to treat infants, children and adults with spinal muscular atrophy (SMA). As a foundation of care in SMA, more than 14,000 individuals have been treated with SPINRAZA worldwide.⁸

SPINRAZA is an antisense oligonucleotide (ASO) that targets the underlying cause of motor neuron loss by continuously increasing the amount of full-length survival motor neuron (SMN) protein produced in the body.⁹ It is administered directly into the central nervous system, where motor neurons reside, to deliver treatment where the disease starts.⁹ 

SPINRAZA has shown efficacy across ages and SMA types with a well-established safety profile based on data in patients treated up to 10 years,^10,11 combined with unsurpassed real-world experience. The most common adverse events observed in clinical studies were respiratory infection, fever, constipation, headache, vomiting and back pain. Laboratory tests can monitor for renal toxicity and coagulation abnormalities, including acute severe low platelet counts, which have been observed after administration of some ASOs. 

Biogen licensed the global rights to develop, manufacture and commercialize SPINRAZA from Ionis Pharmaceuticals, Inc. (Nasdaq: IONS). Please click here for Important Safety Information and full Prescribing Information for SPINRAZA in the U.S., or visit your respective country’s product website. 

About Biogen
Founded in 1978, Biogen is a leading biotechnology company that pioneers innovative science to deliver new medicines to transform patients’ lives and to create value for shareholders and our communities. We apply deep understanding of human biology and leverage different modalities to advance first-in-class treatments or therapies that deliver superior outcomes. Our approach is to take bold risks, balanced with return on investment to deliver long-term growth.

We routinely post information that may be important to investors on our website at www.biogen.com. Follow us on social media - Facebook, LinkedIn, X, YouTube.

Biogen Safe Harbor 
This news release contains forward-looking statements, including statements made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995, including statements about potential clinical effects of BIIB115; the potential benefits, safety and efficacy of BIIB115; the clinical development program for BIIB115; the identification and treatment of SMA; our research and development program for the treatment of SMA; the potential of our commercial business and pipeline programs, including BIIB115; and risks and uncertainties associated with drug development and commercialization. These forward-looking statements may be accompanied by words such as “aim,” “anticipate,” “believe,” “could,” “estimate,” “expect,” “forecast,” “intend,” “may,” “plan,” “potential,” “possible,” “will,” “would” and other words and terms of similar meaning. Drug development and commercialization involve a high degree of risk and only a small number of research and development programs result in commercialization of a product. Results in early stage clinical trials may not be indicative of full results or results from later stage or larger scale clinical trials and do not ensure regulatory approval. You should not place undue reliance on these statements or the scientific data presented.

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References:

1. National Institute of Neurological Disorders and Stroke, NIH. Spinal Muscular Atrophy Fact Sheet. Available at https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Spinal-Muscular-Atrophy-Fact-Sheet. Accessed: December 2021.
2. Wadman RI, Wijngaarde CA, Stam M, et al. Muscle strength and motor function throughout life in a cross-sectional cohort of 180 patients with spinal muscular atrophy types 1c–4. Eur J Neurol. 2018;25(3):512-518.
3. Arkblad E, Tulinius M, Kroksmark AK, Henricsson M, Darin N. A population-based study of genotypic and phenotypic variability in children with spinal muscular atrophy. Acta Paediatr. 2009 May;98(5):865-72. doi: 10.1111/j.1651-2227.2008.01201.x. Epub 2009 Jan 20. 
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6. Sugarman EA, Nagan N, Zhu H, Akmaev VR, Zhou Z, Rohlfs EM, Flynn K, Hendrickson BC, Scholl T, Sirko-Osadsa DA, Allitto BA. Pan-ethnic carrier screening and prenatal diagnosis for spinal muscular atrophy: clinical laboratory analysis of >72,400 specimens. Eur J Hum Genet. 2012 Jan;20(1):27-32. doi: 10.1038/ejhg.2011.134. Epub 2011 Aug 3.
7. Cure SMA. About SMA. Available at https://www.curesma.org/about-sma/. Accessed: June 2022.
8. Based on commercial patients, early access patients, and clinical trial participants through December 31, 2022. 
9. SPINRAZA U.S. Prescribing Information. Available at: https://www.spinraza.com/content/dam/commercial/specialty/spinraza/caregiver/en_us/pdf/spinraza-prescribing-information.pdf. Accessed: July 2024.
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11. Finkle et al. Cure SMA 2024. “Final Safety and Efficacy Data From the SHINE Study in Participants With Infantile-Onset and Later-Onset SMA “

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