Seizure Outcomes and Durability of Response

For clinicians who have managed Dravet syndrome, the pattern of treating patients who improve temporarily and then experience seizure creep is familiar and frustrating. A medication works well for a period, seizures begin to return, doses are adjusted, and the original level of control is never quite recaptured. The zorevunersen efficacy data tells a different story.

Dr. Wheless reflects on what investigators observed as patients moved through the trial. These were patients they had treated for years, whose seizure burdens they knew well, and who had failed or only partially responded to the best available therapies. The shift in seizure frequency that families began reporting -- dramatic reductions, events becoming rare -- was striking precisely because medications were being held constant. The data confirmed what clinicians were observing: for patients who received the 70 mg dose and then transitioned to 45 mg maintenance dosing, median seizure reductions ranged from approximately 60% on the low end to more than 80 to 90%, sustained across the observation period.

Dr. Schreiber notes that the response appears quickly relative to what one might expect from an intrathecal ASO, particularly at higher doses where loading doses accelerate protein restoration. Critically, that response is maintained. He reports that patients he continues to dose years after their initial enrollment remain seizure-responsive, and the low dropout rate from the open-label extension studies further supports that the efficacy is durable and the treatment is well enough tolerated that patients and families choose to continue.

Dr. Wirrell brings the honeymoon comparison into focus directly. In difficult-to-treat epilepsies, including Dravet, antiseizure medications frequently demonstrate early efficacy that erodes over months as the disease reasserts itself. With zorevunersen, that pattern was not observed. The seizure reductions documented at earlier time points held through three years of study follow-up -- and panelists with patients who have been on treatment for five to six years report that the response continues. She emphasizes that this sustained benefit, in a population that had failed multiple standard therapies, represents a qualitatively different kind of outcome.

In the next episode, the panelists turn to the neurodevelopmental and functional outcomes from the zorevunersen studies, examining what the Vineland data showed, what families identified as meaningful improvement, and what disease modification in the real world looks like for children with Dravet syndrome.