Treatment-resistant epilepsy affects thousands of adolescents and adults with devastating developmental disorders, leaving families with few therapeutic options beyond multiple daily medications that often fail to control seizures. This reality may be shifting with early evidence that targeting serotonin pathways could offer meaningful seizure reduction where conventional approaches fall short.
A phase 1b/2a trial tested bexicaserin, a selective 5-HT2C receptor agonist, in 52 participants with severe epileptic encephalopathies including Dravet syndrome and Lennox-Gastaut syndrome. Participants received either bexicaserin (up to 12mg three times daily) or placebo for 75 days while continuing their existing antiseizure regimens. The drug demonstrated measurable reductions in countable motor seizures during the 60-day maintenance phase, with 65% of bexicaserin recipients experiencing treatment-related side effects compared to 33% on placebo.
The serotonin connection to seizure control represents a relatively unexplored therapeutic avenue. While GABA and sodium channel modulators dominate current epilepsy treatment, serotonergic signaling influences neuronal excitability through different mechanisms that could complement existing therapies. This approach is particularly intriguing for developmental epileptic encephalopathies, where seizures often resist multiple conventional medications and contribute to progressive cognitive decline.
However, the 16% discontinuation rate during dose escalation signals tolerability challenges that could limit clinical utility. The small placebo group (nine participants) also constrains statistical power for definitive efficacy conclusions. Still, for conditions where seizure freedom remains elusive despite polytherapy, even modest improvements could meaningfully impact quality of life and developmental trajectories.