Biogen, Stoke Release Final BUTTERFLY Study Data

November 17, 2025 — 09:49 am EST

Written by RTTNews.com for RTTNews

(RTTNews) - Biogen Inc. (BIIB) and Stoke Therapeutic (STOK), Monday announced the final results of the two-year BUTTERFLY natural history study in Neurology.

This provides one of the most thorough assessments of the effects of Dravet syndrome on cognitive, behavioral, and motor development to date. Children and adolescents between the ages of 2 and 18 who received standard-of-care treatments, such as anti-seizure medications, were the subjects of the study.

Regardless of the age at study entry, researchers discovered that neurodevelopment in Dravet syndrome plateaued at about two years of age, leading to a growing gap in comparison to typical development.

Participants' behavior, motor skills, communication, and cognitive abilities barely changed over the course of two years. The frequency of major motor seizures also rose by 10.6 percent.

STOK is currently trading at $26.05, down $0.46 or 1.74 percent on the Nasdaq.

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Biogen, Stoke Release Final BUTTERFLY Study Data

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