– Global, pivotal Phase 3 study will evaluate efficacy and safety of zorevunersen compared to sham over a 52-week treatment period –
– Dravet syndrome is a rare genetic disease characterized by refractory seizures and neurodevelopmental impairments, with no currently approved medicines that address the underlying cause of the disease –
CAMBRIDGE, Mass. and BEDFORD, Mass., Aug. 11, 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 that the first patient has been dosed in the global Phase 3 EMPEROR study of zorevunersen for the treatment of Dravet syndrome. Zorevunersen, an investigational antisense oligonucleotide, has the potential to be the first disease-modifying treatment for Dravet syndrome.
“Our Phase 1/2 and open-label extension studies have provided a large dataset to support our understanding of zorevunersen and guide the EMPEROR study design, including dosing, duration and selection and powering of the endpoints,” said Barry Ticho, M.D., Ph.D., Chief Medical Officer of Stoke Therapeutics. “Given the severity of this disease and the limitations of current treatments, the substantial and durable reductions in seizures and continuing improvements in cognition and behavior support our belief that zorevunersen may improve outcomes for patients with Dravet syndrome.”
“The initiation of the EMPEROR study is a critical milestone in zorevunersen's development,” said Katherine Dawson, M.D., Head of the Therapeutics Development Unit at Biogen. “Despite treatment with available anti-seizure medicines, no approved medications currently address the underlying cognitive and behavioral aspects of this rare, genetic disease. Together with Stoke, we look forward to working in collaboration with the hope of bringing forward zorevunersen as the first disease-modifying treatment option, if approved, for Dravet syndrome.”
EMPEROR Pivotal Phase 3 Design Summary
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Anticipated Enrollment: Patients with Dravet syndrome between the ages of 2 and up to 18 years of age with a confirmed variant in the SCN1A gene not associated with gain of function.
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Duration: Following an 8-week baseline period, participants will be randomized 1:1 to receive either zorevunersen or sham for a 52-week treatment period.
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Treatment Arms: Patients in the active treatment arm will receive two 70mg loading doses (Day 1 and Week 8) followed by two 45mg maintenance doses (Week 24 and Week 40). All patients will continue to receive standard of care medicines throughout the study.
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Primary Endpoint: Change in major motor seizure frequency measured at Week 28.
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Key Secondary Endpoints: Change in major motor seizure frequency measured at Week 52. Change in behavior and cognition as measured by the Vineland-3 subdomains, including expressive communication, receptive communication, interpersonal relationships, coping skills and personal skills measured at Week 52.
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Eligible participants will be offered ongoing treatment with zorevunersen as part of an open-label extension (OLE) study.
“Dravet syndrome is one of the most well studied genetic epilepsies so we know the significant and life-altering effects it can have on patients and their caregivers,” said Joseph Sullivan, M.D., FAES, principal investigator of the study and Professor of Neurology and Pediatrics and Director of the Pediatric Epilepsy Center of Excellence at the University of California San Francisco. “Providing additional relief from seizures remains an important clinical outcome, but the potential to address the underlying genetic cause to also address neurodevelopmental symptoms signals a fundamentally new way of treating the disease. The urgent need for treatments is evident in the high degree of interest in the EMPEROR study.”
The EMPEROR clinical trial has initiated in the United States, United Kingdom, Japan and is planned for Europe. For more information on the EMPEROR study, please visit https://www.emperorstudy.com/ and https://clinicaltrials.gov/study/NCT06872125.
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.
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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 ~50% of normal protein levels (haploinsufficiency). Proof of concept has been demonstrated in other organs, tissues, and systems, supporting broad potential for the Company’s proprietary approach. Stoke is headquartered in Bedford, Massachusetts.
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
About Zorevunersen
Zorevunersen is an investigational antisense oligonucleotide that is designed to treat the underlying cause of Dravet syndrome by increasing 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 the EMPEROR Study
The EMPEROR Phase 3 Study (NCT06872125) is a global, double-blind, sham-controlled study evaluating the efficacy, safety and tolerability of zorevunersen in children ages 2 to <18 with Dravet syndrome with a confirmed variant in the SCN1A gene not associated with gain of function. The trial is expected to enroll participants across the United States, Japan, United Kingdom and European Union, with participants being randomized 1:1 to receive either zorevunersen via intrathecal administration or a sham comparator for a 52-week treatment period following an 8-week baseline period. Following the completion of the study, eligible participants will be offered ongoing treatment with zorevunersen as part of an OLE study. The primary endpoint of the study is percent change from baseline in major motor seizure frequency at week 28 in patients receiving zorevunersen as compared to sham. The key secondary endpoints are the durability of effect on major motor seizure frequency and improvements in behavior and cognition as measured by Vineland-3 subdomains, including expressive communication, receptive communication, interpersonal relationships, coping skills and personal skills. Additional endpoints include safety, Clinician Global Impression of Change (CGI-C), Caregiver Global Impression of Change (CaGI-C), and the Bayley Scales of Infant Development (BSID-IV). For more information, visit https://www.emperorstudy.com/.
Reference:
1.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.