Biogen and Stoke Therapeutics Present New Data at the 54th Child Neurology Society (CNS) Annual Meeting that Support the Potential of Zorevunersen as a Disease-Modifying Medicine for Dravet Syndrome
Biogen (Nasdaq: BIIB) and Stoke Therapeutics presented longer-term open-label extension data for zorevunersen at the 54th Child Neurology Society Annual Meeting on Oct 9, 2025. Two‑year analyses showed continuing improvements in cognition and behavior versus minimal change in a two‑year natural history cohort. Clinician and caregiver Global Impression scales reported similar overall clinical improvements in 95% of patients (n=19) at three years. Substantial and durable reductions in major motor seizure frequency were observed through 36 months. Safety data (n=81) showed TEAEs in 30%–53%, CSF protein elevations in 14%–44% (any >50 mg/dL: 42%–86%), one discontinuation, and one SUSAR.
Biogen (Nasdaq: BIIB) e Stoke Therapeutics hanno presentato dati di estensione aperta a lungo termine per zorevunersen al 54° Meeting Annuale della Child Neurology Society il 9 ottobre 2025. Le analisi biennali hanno mostrato miglioramenti continui della cognizione e del comportamento rispetto a un cambiamento minimo in una coorte di storia naturale di due anni. Le scale di Global Impression dei medici e dei caregiver hanno riportato simili miglioramenti clinici complessivi nel 95% dei pazienti (n=19) a tre anni. Rilevamenti sostanziali e duraturi nella frequenza delle crisi motorie principali sono stati osservati fino a 36 mesi. I dati sulla sicurezza (n=81) hanno mostrato TEAEs in 30%–53%, elevazioni delle proteine CSF in 14%–44% (tutti >50 mg/dL: 42%–86%), una interruzione dello studio e un SUSAR.
Biogen (Nasdaq: BIIB) y Stoke Therapeutics presentaron datos de extensión abierta a largo plazo para zorevunersen en la 54ª Reunión Anual de la Sociedad de Neurología Infantil el 9 de octubre de 2025. Los análisis de dos años mostraron mejoras continuas en la cognición y el comportamiento frente a un cambio mínimo en una cohorte de historia natural de dos años. Las escalas Global Impression de clínicos y cuidadores informaron mejoras clínicas globales similares en el 95% de los pacientes (n=19) a tres años. Se observaron reducciones sustanciales y duraderas en la frecuencia de crisis motoras principales hasta 36 meses. Los datos de seguridad (n=81) mostraron TEAEs en 30%–53%, elevaciones de proteínas CSF en 14%–44% (todas >50 mg/dL: 42%–86%), una descontinuación y un SUSAR.
Biogen (나스닥: BIIB)와 Stoke Therapeutics는 zorevunersen에 대한 장기 오픈 라벨 연장 데이터를 54차 연례 소아 신경학회에서 발표했습니다. 2025년 10월 9일에 발표된 내용입니다. 2년 분석에서 인지 및 행동의 지속적인 개선이 나타났으며, 2년간의 자연사 코호트에서의 변화는 최소였습니다. 임상의 및 보호자 Global Impression 척도는 3년째에 전체 임상 개선이 유사하게 보고되었으며 (n=19, 95%) 3년 차에 해당합니다. 주요 운동 발작 빈도에서 상당하고 지속적인 감소가 36개월까지 관찰되었습니다. 안전성 데이터(n=81)에서는 TEAEs가 30%–53%, CSF 단백질 상승이 14%–44% (모두 >50 mg/dL: 42%–86%), 중단 1건 및 SUSAR 1건이 보고되었습니다.
Biogen (NYSE: BIIB) et Stoke Therapeutics ont présenté des données d’extension ouverte à long terme pour zorevunersen lors de la 54e réunion annuelle de la Child Neurology Society le 9 octobre 2025. Les analyses sur deux ans ont montré des améliorations continues de la cognition et du comportement par rapport à un changement minimal dans une cohorte d’histoire naturelle sur deux ans. Les échelles Global Impression chez les cliniciens et les aidants ont rapporté des améliorations cliniques globales similaires chez 95% des patients (n=19) à trois ans. Des réductions substantielles et durables de la fréquence des crises épileptiques majeures ont été observées jusqu’à 36 mois. Les données de sécurité (n=81) ont montré des TEAE dans 30%–53%, des élévations des protéines CSF dans 14%–44% (tous >50 mg/dL : 42%–86%), une interruption et un SUSAR.
Biogen (Nasdaq: BIIB) und Stoke Therapeutics präsentierten längere offene Verlängerungsdaten zu zorevunersen auf der 54. Jahrestagung der Child Neurology Society am 9. Oktober 2025. Zwei Jahre Analysen zeigten fortlaufende Verbesserungen in der Kognition und im Verhalten gegenüber einer zwei Jahre dauernden natürlichen Verlaufskohorte mit minimaler Veränderung. Globale Eindruck-Skalen von Klinikern und Betreuern berichteten ähnliche allgemeine klinische Verbesserungen bei 95% der Patienten (n=19) nach drei Jahren. Es wurden signifikante und dauerhafte Reduktionen der Frequenz schwerer motorischer Anfälle bis zu 36 Monaten beobachtet. Sicherheitsdaten (n=81) zeigten TEAEs in 30%–53%, CSF-Proteine Erhöhungen in 14%–44% (alle >50 mg/dL: 42%–86%), eine Abbruchstelle und einen SUSAR.
Biogen (ناسداك: BIIB) وStoke Therapeutics قدما بيانات تمديد مفتوحة طويلة الأجل لـ zorevunersen في الاجتماع السنوي الـ54 لجمعية علم الأعصاب الأطفال في 9 أكتوبر 2025. أظهرت التحليلات على مدى عامين تحسنات مستمرة في الإدراك والسلوك مقارنة بتغير ضئيل في مجموعة التاريخ الطبيعي لمدة عامين. أبلغت مقاييس الانطباع العالمي من الأطباء ومقدمي الرعاية عن تحسينات سريرية عامة مماثلة في 95% من المرضى (العدد = 19) عند ثلاث سنوات. لوحظت تخفيضات كبيرة ودائمة في تكرار حدوث النوبات الحركية الكبرى حتى 36 شهراً. تظهر بيانات السلامة (العدد = 81) وجود TEAEs بنسبة 30%–53%، وارتفاع بروتين CSF بنسبة 14%–44% (جميعها >50 mg/dL: 42%–86%)، ووقف واحد، وSUSAR واحد.
Biogen（纳斯达克代码：BIIB）与 Stoke Therapeutics 在第54届儿童神经学会年会上于 2025年10月9日 公布了 zorevunersen 的长期开放标签延伸数据。两年分析显示认知与行为方面持续改善，而两年自然史队列的变化很小。临床医生和照护者的全球印象量表在三年时报告了相似的总体临床改善，覆盖 95% 的患者（n=19）。在 36 个月内观察到主要运动性癫痫发作频率的显著且持久下降。安全性数据（n=81）显示 TEAE 为 30%–53%，CSF 蛋白升高为 14%–44%（均>50 mg/dL：42%–86%），有1例停药，1例 SUSAR。
- Clinician and caregiver improvement in 95% of patients at 3 years (n=19)
- Durable reductions in major motor seizure frequency through 36 months
- Two-year cognition and behavior gains versus minimal natural history change
- Phase 3 EMPEROR evaluating 70mg loading/45mg maintenance dosing regimen
- Study drug related TEAEs observed in 30% (Phase 1/2a) and 53% (OLE)
- CSF protein elevations reported in 14% (Phase 1/2a) and 44% (OLE)
- CSF >50 mg/dL occurred in 42% (Phase 1/2a) and 86% (OLE)
- Treatment‑emergent serious adverse events in 22% and 29%; one SUSAR reported
– An analysis designed to evaluate the potential effects of the Phase 3 zorevunersen dosing regimen showed continuing improvements in cognition and behavior at 2 years; results contrast with minimal change in natural history –
– Improvements in overall clinical status at 3 years in the open-label extension studies reported by clinicians and caregivers in
CAMBRIDGE, Mass. and BEDFORD, Mass., Oct. 09, 2025 (GLOBE NEWSWIRE) -- Biogen Inc. (Nasdaq: BIIB) and Stoke Therapeutics, Inc. (Nasdaq: STOK), a biotechnology company dedicated to restoring protein expression by harnessing the body’s potential with RNA medicine, today announced the presentation of longer-term follow-up analyses from the ongoing open-label extension (OLE) studies of zorevunersen that support the potential of zorevunersen as a disease-modifying medicine for Dravet syndrome. These new results were presented at the 54th Child Neurology Society (CNS) Annual Meeting.
New two-year data from an analysis that was initially performed to understand the potential effects of the Phase 3 dosing regimen on cognition and behavior showed continuing improvements at two years. These results contrast with findings from a two-year natural history study in which patients with Dravet syndrome who were treated with standard of care showed minimal changes in cognition and behavior. In addition, the companies presented three-year results from analyses of Clinical and Caregiver Global Impression of Change (CGI-C and CaGI-C) scales measuring overall clinical status, which complement previously presented EQ-VAS caregiver-reported quality of life improvements. Caregivers and clinicians separately reported similar improvements in overall clinical status in
“Data from the ongoing open-label extension studies are helping to shape our understanding of the long-term effects of zorevunersen on seizures, cognition, behavior and overall functioning, which together support the potential for disease modification,” said Kelly Knupp, MD, MSCS, Professor of Pediatrics and Neurology at the University of Colorado Anschutz and the Dravet Program Director and Epilepsy Program Lead at Children's Hospital Colorado. “The natural history data continue to provide important context for the effects we are seeing in patients treated with zorevunersen. Improvements in cognition and behavior are not something we see in patients with Dravet syndrome, and rarely do we see such strong correlation between caregiver and clinician-reported outcomes. Together, these data are starting to paint a fuller picture of the potential impact disease modification could have on a patient’s overall health and daily living.”
These data were among several analyses included in a poster presentation of data from the Phase 1/2a and ongoing OLE studies of zorevunersen. Safety and tolerability were the primary endpoints of these studies. In addition, effects on major motor seizure frequency, cognition and behavior were assessed as secondary endpoints. As previously reported, results showed substantial and durable reductions in major motor seizure frequency and improvements in multiple measures of cognition and behavior on top of a background of standard anti-seizure medicines through three years. The most substantial reductions were observed among patients who were treated with loading doses of 70mg in the Phase 1/2a study followed by maintenance doses of 45mg. This regimen is now being evaluated in the Phase 3 EMPEROR study.
Summary of Safety Data
Eighty-one patients received at least one dose of zorevunersen and have been evaluated for safety. Zorevunersen has been generally well tolerated across the Phase 1/2a and OLE studies. Study drug related treatment emergent adverse events (TEAEs) were observed in
Details of the Presentation
Title: Zorevunersen demonstrates disease-modifying potential in patients with Dravet syndrome through durable seizure reduction and continuing improvements in cognition, behavior, and functioning through 36 months of treatment in open-label extension studies
Presenter: Joseph Sullivan, M.D., FAES, Professor of Neurology and Pediatrics and Director of the Pediatric Epilepsy Center of Excellence at the University of California San Francisco
Session: Poster Review & Guided Abstract Tours
Date and Time: Thursday, October 9, 12:30-1:45 PM and 5:30-7:00 PM ET
Poster Number and Location: Poster #92, Hall C, Charlotte Convention Center, Charlotte, NC
The presentation will be available for download on the Stoke Therapeutics website under the Investors & News tab.
About Dravet Syndrome
Dravet syndrome is a severe developmental and epileptic encephalopathy (DEE) characterized by severe, recurrent seizures as well as significant cognitive and behavioral impairments. Most cases of Dravet are caused by mutations in one copy of the SCN1A gene, leading to insufficient levels of NaV1.1 protein in neuronal cells in the brain. More than 90 percent of patients continue to experience seizures despite treatment with the best available anti-seizure medicines. Complications of the disease often contribute to a poor quality of life for patients and their caregivers. Developmental and cognitive impairments often include intellectual disability, developmental delays, movement and balance issues, language and speech disturbances, growth defects, sleep abnormalities, disruptions of the autonomic nervous system and mood disorders. Compared with the general epilepsy population, people living with Dravet syndrome have a higher risk of sudden unexpected death in epilepsy, or SUDEP. Dravet syndrome occurs globally and is not concentrated in a particular geographic area or ethnic group. Currently, it is estimated that up to 38,000 people are living with Dravet syndrome in the U.S. (~16,000), UK, EU-4 and Japan.1 There are no approved disease-modifying therapies for people living with Dravet syndrome.
About Zorevunersen
Zorevunersen is an investigational antisense oligonucleotide that is designed to treat the underlying cause of Dravet syndrome by increasing functional NaV1.1 protein production in brain cells from the non-mutated (wild-type) copy of the SCN1A gene. This highly differentiated mechanism of action aims to reduce seizure frequency beyond what has been achieved with anti-seizure medicines and to improve neurodevelopment, cognition, and behavior. Zorevunersen has demonstrated the potential for disease modification and has been granted orphan drug designation by the FDA and the EMA. The FDA has also granted zorevunersen rare pediatric disease designation and Breakthrough Therapy Designation for the treatment of Dravet syndrome with a confirmed mutation not associated with gain-of-function, in the SCN1A gene. Stoke has a strategic collaboration with Biogen to develop and commercialize zorevunersen for Dravet syndrome. Under the collaboration, Stoke retains exclusive rights for zorevunersen in the United States, Canada, and Mexico; Biogen receives exclusive rest of world commercialization rights.
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.
About Stoke Therapeutics
Stoke Therapeutics (Nasdaq: STOK), is a biotechnology company dedicated to restoring protein expression by harnessing the body’s potential with RNA medicine. Using Stoke’s proprietary TANGO (Targeted Augmentation of Nuclear Gene Output) approach, Stoke is developing antisense oligonucleotides (ASOs) to selectively restore naturally-occurring protein levels. Stoke’s first medicine in development, zorevunersen, has demonstrated the potential for disease modification in patients with Dravet syndrome and is currently being evaluated in a Phase 3 study. Stoke’s initial focus are diseases of the central nervous system and the eye that are caused by a loss of ~
Biogen Safe Harbor
This news release contains forward-looking statements, including, among others, relating to: the potential clinical effects of zorevunersen; the potential for zorevunersen to improve outcomes for patients with Dravet syndrome; the potential benefits, safety and efficacy of zorevunersen; potential regulatory discussions, submissions and approvals and the timing thereof; the treatment of Dravet syndrome; the anticipated benefits, risks and potential of Biogen's collaboration arrangements with Stoke; the potential of Biogen's commercial business and pipeline programs, including zorevunersen; and risks and uncertainties associated with drug development and commercialization. These forward-looking statements may be accompanied by such words as “aim,” “anticipate,” “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. 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.
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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, 2024 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.
Stoke Therapeutics Cautionary Note Regarding Forward-Looking Statements
This press release contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to: the ability of zorevunersen to treat the underlying causes of Dravet syndrome and reduce seizures or show improvements in behavior and cognition at the indicated dosing levels or at all; and the design, timing and results of the Phase 3 EMPEROR study. Statements including words such as “anticipate,” “could,” “expect,” “plan,” “will,” or “may” and statements in the future tense are forward-looking statements. These forward-looking statements involve risks and uncertainties, as well as assumptions, which, if they prove incorrect or do not fully materialize, could cause Stoke’s results to differ materially from those expressed or implied by such forward-looking statements, including, but not limited to, risks and uncertainties related to: Stoke’s ability to advance, obtain regulatory approval and ultimately commercialize its product candidates; that if Stoke’s collaborators were to breach or terminate their agreements, it would not obtain the anticipated financial or other benefits; the possibility that Stoke and Biogen may not be successful in their development of zorevunersen and that, even if successful, they may be unable to successfully commercialize zorevunersen; positive results in a clinical trial may not be replicated in subsequent trials or successes in early stage clinical trials may not be predictive of results in later stage trials; Stoke’s ability to protect its intellectual property; Stoke’s ability to fund development activities and achieve development goals through mid-2028; and the other risks and uncertainties described under the heading “Risk Factors” in Stoke’s Annual Report on Form 10-K for the year ended December 31, 2024, its quarterly reports on Form 10-Q, and the other documents it files with the Securities and Exchange Commission. These forward-looking statements speak only as of the date of this press release, and Stoke undertakes no obligation to revise or update any forward-looking statements to reflect events or circumstances after the date hereof.
Reference:
- Based on Stoke Therapeutics’ preliminary estimates, which scaled annual incidence to prevalence using country-specific live birth rates over the past 85 years and adjusted for Dravet-specific mortality. The estimate is based on incidence rates published by Wu et al., Pediatrics, 2015.
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FAQ
What did Biogen announce about zorevunersen for Dravet syndrome on Oct 9, 2025 (BIIB)?
How durable were seizure reductions with zorevunersen through 36 months in the BIIB presentation?
What safety signals did Biogen report for zorevunersen (BIIB) in the OLE studies?
What dosing regimen is being evaluated in the Phase 3 EMPEROR study for zorevunersen (BIIB)?
Where and when were the zorevunersen data presented on Oct 9, 2025?
Will investors be able to access the zorevunersen presentation for BIIB?
