Biogen, Stoke Boost Epilepsy Drug’s Blockbuster Potential With Early Seizure Reduction Data
Biogen and Stoke Therapeutics reported new long‑term data for zorevunersen, an investigational antisense oligonucleotide for Dravet syndrome, showing durable reductions in seizure burden.1
A propensity score‑weighted analysis comparing zorevunersen‑treated patients with natural history controls showed a statistically significant reduction in major motor seizures at six months, although specific figures were not disclosed in the company release.1
Jefferies analysts, citing detailed data, reported an 82% drop in major motor seizures among five patients who received two 70‑mg loading doses of zorevunersen, versus a 20% reduction in external natural history comparators over the same period.1
The treatment effect appeared durable:
over 24 months, zorevunersen‑treated patients showed a 76% reduction in seizures compared with 25% among external comparators.1
Stoke and Biogen also observed improvements in five key cognitive and behavioral measures, with several reaching statistical significance, supporting the idea that zorevunersen may have disease‑modifying potential beyond seizure control.1
Analysts at Jefferies wrote that zorevunersen “could be a $1–4B+ blockbuster in Dravet”, attributing the commercial potential largely to its disease‑modifying profile and the new efficacy data.1
The new analysis used propensity score weighting to adjust for baseline differences between treated patients and natural history controls, aiming to “mimic randomization” and better approximate potential Phase III outcomes.1
These data are seen as partially de‑risking for the ongoing Phase III EMPEROR trial, which is evaluating zorevunersen versus placebo in Dravet syndrome.1
Zorevunersen targets the SCN1A mRNA, intended to prevent certain mutations from producing dysfunctional sodium channel protein, thereby addressing an underlying genetic cause of Dravet syndrome.1
Dravet syndrome is a rare, medication‑resistant epilepsy (about 1 in 15,700 people) characterized by frequent, prolonged seizures and developmental, behavioral, movement, and speech problems, highlighting the high unmet need for effective disease‑modifying treatments.1
Biogen and Stoke have been presenting expanding zorevunersen datasets at major epilepsy meetings, including the American Epilepsy Society (AES) 2025 Annual Meeting and the International Epilepsy Congress (IEC) 2025, where they emphasize durable seizure reductions and cognitive/behavioral benefits with up to 36 months of dosing.123
Stoke indicated in its recent quarterly update that it plans to meet with the FDA to discuss potential expedited regulatory pathways for zorevunersen, reflecting growing confidence in the program.1
Sources:
1. https://www.biospace.com/drug-development/biogen-stoke-boost-epilepsy-drugs-blockbuster-potential-with-early-seizure-reduction-data
2. https://medicalupdateonline.com/2025/08/biogen-and-stoke-therapeutics-to-share-latest-results-from-zorevunersen-studies-in-dravet-syndrome-at-iec-2025/
3. https://www.nasdaq.com/press-release/biogen-and-stoke-therapeutics-present-data-further-support-disease-modifying-0