Biogen Inc. and Stoke Therapeutics have announced the publication of final data from the two-year BUTTERFLY natural history study in people with Dravet syndrome. The study results, which have been published, indicate that children with Dravet syndrome continue to experience frequent seizures and significant cognitive and behavioral impairments despite treatment with standard-of-care anti-seizure medicines. The data show minimal changes in cognition and behavior over two years, with affected children developing a widening gap in neurodevelopment compared to their neurotypical peers. The findings highlight the need for new medicines that target the underlying genetic cause of Dravet syndrome to improve long-term outcomes. There are currently no approved disease-modifying treatments for Dravet syndrome.