Biogen Presents Additional Salanersen Data Showing New Motor Milestones Achieved in Children with SMA Previously Treated with Gene Therapy

Rhea-AI Summary

Biogen (Nasdaq: BIIB) presented Phase 1b data showing salanersen, an investigational once-yearly antisense oligonucleotide for spinal muscular atrophy (SMA), was generally well tolerated and associated with functional improvement in 24 children previously treated with gene therapy.

Key findings: sustained 75% reductions in neurofilament light chain at six months for participants with elevated baseline NfL, 12 of 24 achieved new WHO motor milestones, and all maintained or improved baseline milestones. Biogen also launched a global Phase 3 program (STELLAR-1, STELLAR-2, SOLAR) with planned initiations in Q2–Q3 2026.

Positive

• NfL biomarker concentrations reduced by 75% at six months in participants with elevated baseline NfL
• 12 of 24 participants achieved at least one new WHO motor milestone
• All 24 participants showed improvement from baseline on one or more endpoints
• Phase 3 program initiated with three global studies (STELLAR-1, STELLAR-2, SOLAR) planned in Q2–Q3 2026
• Salanersen administered once-yearly with 80 mg dose selected for Phase 3 evaluation

Negative

• Small Phase 1b sample size of 24 participants limits generalizability
• Two of three Phase 3 studies (STELLAR-1 and SOLAR) are open-label, which may reduce control versus blinded designs
• Common adverse events included pyrexia, upper respiratory tract infection, and vomiting, reported across dose groups

News Market Reaction – BIIB

+1.10%

1 alert

+1.10% News Effect

On the day this news was published, BIIB gained 1.10%, reflecting a mild positive market reaction.

Data tracked by StockTitan Argus on the day of publication.

Key Figures

Phase 1b sample size: 24 participants Dose levels: 40 mg and 80 mg NfL reduction: 75% +5 more

8 metrics

Phase 1b sample size 24 participants Children with SMA aged 0.5–12 years previously treated with gene therapy

Dose levels 40 mg and 80 mg Once‑yearly salanersen dosing evaluated; 80 mg advancing to Phase 3

NfL reduction 75% Reduction in neurofilament light chain at six months in elevated‑baseline patients

New motor milestones 12 of 24 patients Achieved at least one new WHO motor milestone after salanersen initiation

Follow-up duration Minimum 1 year All Phase 1b participants had at least one year of follow-up

STELLAR-1 age Under 6 weeks Treatment‑naïve, clinically presymptomatic infants with genetic SMA diagnosis

SOLAR age range 15–60 years Teens and adults with SMA, treatment‑naïve or previously on risdiplam

Phase 3 program size 3 global studies STELLAR-1, STELLAR-2, and SOLAR evaluating once‑yearly 80 mg salanersen

Market Reality Check

Price: $181.55 Vol: Volume 666,126 is below t...

low vol

$181.55 Last Close

Volume Volume 666,126 is below the 20-day average of 1,014,973 (relative volume 0.66) ahead of this SMA update. low

Technical Price at 188.41 is trading above the 200-day MA of 154.67, sitting 6.92% below the 52-week high of 202.41 and 71.23% above the 52-week low of 110.035.

Peers on Argus

BIIB was up 0.09% pre-news while large-cap peers showed mixed moves: PFE up 1.27...

BIIB was up 0.09% pre-news while large-cap peers showed mixed moves: PFE up 1.27%, but GSK, BMY, AMGN, and SNY down between 0.14% and 1.43%, suggesting stock-specific rather than broad sector momentum.

Historical Context

5 past events · Latest: 2026-03-05 (Positive)

Pattern 5 events

Date	Event	Sentiment	Move	Catalyst
2026-03-05	SMA data preview	Positive	-1.0%	Planned presentation of new SMA data for nusinersen and salanersen at MDA/SMA Europe.
2026-03-04	Dravet trial data	Positive	-1.0%	NEJM publication of zorevunersen data suggesting disease modification in Dravet syndrome.
2026-02-24	Conference appearance	Neutral	-2.3%	Announcement of a TD Cowen health care conference presentation.
2026-02-11	Governance update	Positive	+2.3%	Board chair transition with emphasis on upcoming lupus and nephrology catalysts.
2026-02-04	Investor conference	Neutral	-0.1%	Notice of a Guggenheim biotech summit presentation and webcast availability.

Pattern Detected

Recent BIIB news has often produced modest moves, with mixed alignment between positive R&D headlines and short-term price reactions.

Recent Company History

Over the last months, Biogen has highlighted multiple neurology and rare-disease programs. On Feb 11, a board chair transition accompanied commentary on an 18‑month catalyst window, and shares rose 2.25%. Earlier in March, positive SMA and Dravet syndrome clinical updates on Mar 4 and Mar 5 each saw BIIB decline 0.98%. Conference-related items in February had small to moderate negative moves. Against this backdrop, today’s new salanersen Phase 1b data and Phase 3 designs extend the SMA narrative already introduced on Mar 5.

Market Pulse Summary

This announcement adds substantive detail to Biogen’s SMA strategy, highlighting Phase 1b salanersen...

Analysis

This announcement adds substantive detail to Biogen’s SMA strategy, highlighting Phase 1b salanersen data with a 75% reduction in neurofilament light chain and new WHO motor milestones in 12 of 24 children previously treated with gene therapy. The three‑study Phase 3 program (STELLAR‑1, STELLAR‑2, SOLAR) expands across infants to adults, following earlier SMA conference previews on Mar 5. Investors may track enrollment progress, safety signals, and functional outcomes as key validation points for this once‑yearly ASO approach.

Key Terms

antisense oligonucleotide, spinal muscular atrophy, neurofilament light chain, world health organization (who) motor milestones, +4 more

8 terms

antisense oligonucleotide medical

"Salanersen is a novel antisense oligonucleotide and has the potential..."

An antisense oligonucleotide is a small piece of synthetic genetic material designed to attach to specific molecules in the body’s cells, effectively blocking or modifying how genes are expressed. This technology is important because it can be used to develop targeted treatments for certain diseases, which may influence the value of biotech companies and the broader healthcare sector. Its development reflects advances in personalized medicine and gene-based therapies.

spinal muscular atrophy medical

"salanersen ... given once a year for spinal muscular atrophy (SMA)"

A genetic condition in which the “wiring” between the spinal cord and muscles fails, causing progressive loss of muscle strength and motor skills from infancy through adulthood as the nerve cells that move muscles deteriorate. Investors pay attention because the condition creates a clear, long-term need for specialized therapies, diagnostics and ongoing care — meaning successful drugs or tests can attract premium pricing, sustained demand and significant regulatory and reimbursement scrutiny that materially affect biotech and healthcare valuations.

neurofilament light chain medical

"had elevated baseline concentrations of neurofilament light chain (NfL)..."

Neurofilament light chain is a protein released into cerebrospinal fluid and blood when nerve cells are damaged, acting like a measurable “leak” that signals injury to the brain or spinal cord. For investors, it matters because rising or falling levels can serve as an objective readout in clinical trials and disease monitoring, helping assess whether a drug or therapy is slowing nerve damage and reducing development or commercial risk.

world health organization (who) motor milestones medical

"including achievement of new World Health Organization (WHO) motor milestones"

World Health Organization (WHO) motor milestones are a set of age-based benchmarks describing when most infants and young children typically achieve key physical skills (for example rolling, sitting, crawling, standing and walking). Investors watch these milestones because they serve as simple, widely accepted measures in pediatric clinical trials, public-health assessments and product-market evaluations — like a checklist that shows whether a therapy, device or program helps children reach normal development on time.

open-label medical

"STELLAR-1, an open-label study, will evaluate the effects of salanersen..."

Open-label describes a situation where everyone involved in a study or process knows the full details, such as who is receiving a treatment or intervention. For investors, understanding whether a project or product is open-label helps gauge the level of transparency and potential biases, influencing trust and decision-making. It’s like knowing whether a test or experiment is conducted openly or behind closed doors.

double-blind medical

"STELLAR-2, a randomized, double-blind, sham-controlled study, will evaluate..."

A double-blind process means that neither the people conducting an activity nor the people involved know certain key details, such as who is receiving a treatment or a placebo. This approach helps prevent bias from influencing the results, making the outcome more trustworthy. For investors, it ensures that decisions or judgments are based on unbiased information rather than preconceived opinions or expectations.

sham-controlled medical

"STELLAR-2, a randomized, double-blind, sham-controlled study, will evaluate..."

A sham-controlled trial compares a real medical procedure or device to a fake version that looks and feels the same but has no therapeutic effect, much like a sugar pill for surgery or implants. For investors, sham control is a sign of rigorous testing because it helps separate true treatment benefits from placebo effects or patient expectations, making clinical results and regulatory prospects more reliable when assessing commercial potential.

adverse events medical

"most adverse events (AEs) have been mild to moderate in severity"

Adverse events are any harmful or unwanted medical occurrences experienced by people using a drug, device, or undergoing a treatment, whether or not the problem is caused by the product. Think of them as complaints or breakdowns noticed during a trial or after a product is on the market; regulators record and investigate them. Investors care because clusters or serious adverse events can delay approvals, trigger costly studies or recalls, change labeling, and quickly alter a company’s revenue and risk profile.

AI-generated analysis. Not financial advice.

• New Phase 1b data support the safety and effectiveness of salanersen over one year in children with SMA who had the potential for improvement due to suboptimal clinical status with prior gene therapy
• Salanersen is a novel antisense oligonucleotide and has the potential to deliver high efficacy in SMA with once-yearly dosing
• Biogen also debuted the design of the Phase 3 salanersen clinical trial program which is being initiated at sites around the world

CAMBRIDGE, Mass., March 11, 2026 (GLOBE NEWSWIRE) -- Biogen Inc. (Nasdaq: BIIB) presented additional results from the Phase 1b study of salanersen, an investigational novel antisense oligonucleotide (ASO) given once a year for spinal muscular atrophy (SMA), at the 2026 Muscular Dystrophy Association (MDA) Clinical & Scientific Conference. The study evaluated salanersen in children who had suboptimal clinical status despite prior administration of gene therapy (onasemnogene abeparvovec-xioi). Salanersen was generally well-tolerated. Participants experienced a slowing of neurodegeneration and functional improvement, including achievement of new World Health Organization (WHO) motor milestones, following initiation of salanersen. These new results include a minimum of one year of follow-up for all participants, building on the interim study data presented at Cure SMA 2025. The company also presented the study designs of the Phase 3 salanersen clinical trials.

“Spinal muscular atrophy has benefitted from extraordinary therapeutic progress, but across the treatment landscape there remains room for improvement. There is growing scientific and clinical enthusiasm about the advances that salanersen offers,” said Thomas Crawford, M.D., co-director, Muscular Dystrophy Association Clinic at Johns Hopkins Medicine. “These additional Phase 1 data add confidence in the emerging salanersen clinical profile. We have more reason to look forward to results of the Phase 3 program."

Salanersen Phase 1b Study Results
In this analysis, new data are available for study participants (n=24, aged 0.5-12 years), all of whom have received at least 2 doses of salanersen (40 mg or 80 mg). The 80 mg dose will be further evaluated in the Phase 3 studies.

In participants who received salanersen 40 mg and 80 mg and had elevated baseline concentrations of neurofilament light chain (NfL), a marker of ongoing neurodegeneration, meaningful reductions (75%) in NfL levels were observed at six months; these reductions were sustained throughout the follow-up period. All 24 participants treated with salanersen experienced improvement from baseline on one or more endpoints. Notably, 12 of the 24 achieved at least one new WHO motor milestone, and all participants maintained the motor milestones documented at their baseline. Salanersen has been generally well-tolerated at both 40 and 80 mg doses in the ongoing Phase 1 study, and most adverse events (AEs) have been mild to moderate in severity. As of the analysis, the most common AEs in the 40 mg group were upper respiratory tract infection and vomiting, and the most common AEs in the 80 mg group were pyrexia and upper respiratory tract infection.

Salanersen Phase 3 Clinical Development Program
Biogen also presented the design of the Phase 3 clinical program that will evaluate once-yearly salanersen 80 mg across the broad SMA population. The program is comprised of three global studies:

• STELLAR-1, an open-label study, will evaluate the effects of salanersen in young (under 6 weeks old), treatment-naïve and clinically presymptomatic infants with a genetic diagnosis of SMA.
• STELLAR-2, a randomized, double-blind, sham-controlled study, will evaluate the effects of salanersen when initiated ~6 months after onasemnogene abeparvovec-xioi in infants with SMA who received presymptomatic treatment with the gene therapy at 6 weeks of age or younger.
• SOLAR, an open-label study, will evaluate the effects of salanersen in teens and older adults (aged 15–60 years) with SMA who are either treatment-naïve or previously treated with risdiplam.
  

The STELLAR trials are complementary and designed to compare multiple early treatment strategies in presymptomatic newborns – salanersen alone, gene therapy alone, and salanersen as an add-on to gene therapy – to inform future treatment approaches in SMA. The clinical development program has already commenced with STELLAR-1 initiated screening, and the other studies planned to initiate in Q2 2026 (SOLAR) and Q3 2026 (STELLAR-2).

“With the encouraging Phase 1b results in hand, we are initiating the Phase 3 STELLAR-1, STELLAR-2, and SOLAR salanersen studies as quickly as possible,” said Stephanie Fradette, Pharm.D., Head of the Neuromuscular Development Unit at Biogen. “Together with the SMA community, we have designed these studies to confidently answer the most relevant questions for the field and establish salanersen’s role in the future treatment landscape.”

In addition to being presented at MDA, these data will also be shared at the 5th International Scientific Congress on SMA (SMA Europe 2026).

About Salanersen
Salanersen (BIIB115) is a novel, intrathecally administered antisense oligonucleotide (ASO) in development for SMA. Salanersen is designed to correct splicing of SMN2 pre-mRNA to increase production of SMN protein. It has a new backbone chemistry that leads to high potency, enabling the potential for high efficacy with once-yearly dosing.

Salanersen is being evaluated in three global Phase 3 studies designed to evaluate safety and efficacy of 80 mg administered once-yearly in a broad spectrum of individuals living with SMA. 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 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, Instagram, 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 the potential clinical effects of salanersen; the potential benefits, safety and efficacy of salanersen, including the potential to slow neurodegeneration and improve motor function; the clinical development program for salanersen; 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 salanersen; 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,” “assume,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “forecast,” “goal,” “guidance,” “hope,” “intend,” “may,” “objective,” “outlook,” “plan,” “possible,” “potential,” “predict,” “project,” “prospect,” “should,” “target,” “will,” “would” or the negative of these words or 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. Given their forward-looking nature, these statements involve substantial risks and uncertainties that may be based on inaccurate assumptions and could cause actual results to differ materially from those reflected in such statements.

These forward-looking statements are based on management’s current beliefs and assumptions and on information currently available to management. Given their nature, we cannot assure that any outcome expressed in these forward-looking statements will be realized in whole or in part. We caution that these statements are subject to risks and uncertainties, many of which are outside of our control and could cause future events or results to differ materially from those stated or implied in this document, including, among others, uncertainty of our long-term success in developing, licensing, or acquiring other product candidates or additional indications for existing products; expectations, plans, prospects and timing of actions relating to product approvals, approvals of additional indications for our existing products, sales, pricing, growth, reimbursement and launch of our marketed and pipeline products; the potential impact of increased product competition in the biopharmaceutical and healthcare industry, as well as any other markets in which we compete, including increased competition from new originator therapies, generics, prodrugs and biosimilars of existing products and products approved under abbreviated regulatory pathways; our ability to effectively implement our corporate strategy; difficulties in obtaining and maintaining adequate coverage, pricing, and reimbursement for our products; the drivers for growing our business, including our dependence on collaborators and other third parties for the development, regulatory approval, and commercialization of products and other aspects of our business, which are outside of our full control; risks related to commercialization of biosimilars, which is subject to such risks related to our reliance on third-parties, intellectual property, competitive and market challenges and regulatory compliance; the risk that positive results in a clinical trial may not be replicated in subsequent or confirmatory trials or success in early stage clinical trials may not be predictive of results in later stage or large scale clinical trials or trials in other potential indications; risks associated with clinical trials, including our ability to adequately manage clinical activities, unexpected concerns that may arise from additional data or analysis obtained during clinical trials, regulatory authorities may require additional information or further studies, or may fail to approve or may delay approval of our drug candidates; and the occurrence of adverse safety events, restrictions on use with our products, or product liability claims; and any other risks and uncertainties that are described in other reports we have filed with the U.S. Securities and Exchange Commission, which are available on the SEC’s website at www.sec.gov.

These statements speak only as of the date of this press release and are based on information and estimates available to us at this time. Should known or unknown risks or uncertainties materialize or should underlying assumptions prove inaccurate, actual results could vary materially from past results and those anticipated, estimated or projected. Investors are cautioned not to put undue reliance on forward-looking statements. A further list and description of risks, uncertainties and other matters can be found in our Annual Report on Form 10-K for the fiscal year ended December 31, 2025 and in our subsequent reports on Form 10-Q. Except as required by law, we do not undertake any obligation to publicly update any forward-looking statements whether as a result of any new information, future events, changed circumstances or otherwise.

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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: March 2026.
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. 
4. Jedrzejowska M, Milewski M, Zimowski J, Zagozdzon P, Kostera-Pruszczyk A, Borkowska J, Sielska D, Jurek M, Hausmanowa-Petrusewicz I. Incidence of spinal muscular atrophy in Poland--more frequent than predicted? Neuroepidemiology. 2010;34(3):152-7. doi: 10.1159/000275492. Epub 2010 Jan 15.
5. Prior TW, Snyder PJ, Rink BD, Pearl DK, Pyatt RE, Mihal DC, Conlan T, Schmalz B, Montgomery L, Ziegler K, Noonan C, Hashimoto S, Garner S. Newborn and carrier screening for spinal muscular atrophy. Am J Med Genet A. 2010 Jul;152A(7):1608-16. doi: 10.1002/ajmg.a.33474.
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. Kolb SJ, Coffey CS, Yankey JW, et al. Natural history of infantile-onset spinal muscular atrophy. Ann Neurol. 2017;82(6):883-891. doi:10.1002/ana.25101.
   

MEDIA CONTACT: Biogen Madeleine Shin +1-781-464-3260 public.affairs@biogen.com

INVESTOR CONTACT: Biogen Tim Power +1 781 464 2442 IR@biogen.com

FAQ

What were the Phase 1b salanersen results announced by Biogen (BIIB) on March 11, 2026?

The Phase 1b results showed tolerability and functional gains in 24 children previously treated with gene therapy. According to the company, participants had sustained 75% NfL reductions at six months and 12 of 24 achieved new WHO motor milestones, with all maintaining baseline milestones.

How did salanersen affect the neurodegeneration biomarker in the BIIB Phase 1b study?

Salanersen produced a meaningful reduction in neurodegeneration biomarker levels at six months. According to the company, participants with elevated baseline neurofilament light chain saw ~75% reductions that were sustained through the follow-up period.

What safety profile did Biogen report for salanersen (BIIB) in the Phase 1b cohort?

Salanersen was generally well tolerated with mostly mild-to-moderate adverse events. According to the company, most common events were upper respiratory tract infection, pyrexia, and vomiting across the 40 mg and 80 mg dose groups.

Which Phase 3 trials for salanersen did Biogen (BIIB) initiate and when will they start?

Biogen launched a three-study Phase 3 program: STELLAR-1, STELLAR-2 and SOLAR. According to the company, STELLAR-1 began screening and SOLAR and STELLAR-2 are planned to initiate in Q2 2026 and Q3 2026, respectively.

Who is eligible for the STELLAR-1 and STELLAR-2 salanersen studies from Biogen (BIIB)?

STELLAR-1 targets treatment-naïve, presymptomatic infants under six weeks with genetic SMA. According to the company, STELLAR-2 will evaluate infants treated presymptomatically with onasemnogene abeparvovec-xioi when salanersen is initiated about six months after gene therapy.

What does Biogen (BIIB) plan to study in the SOLAR salanersen trial?

SOLAR will evaluate salanersen in teens and adults aged 15–60, including treatment-naïve and risdiplam-treated individuals. According to the company, SOLAR is an open-label study designed to assess safety and functional effects in older patients with SMA.