Open Access

Adam Strzelczyk, Milka Pringsheim, Thomas Mayer, Tilman Polster, Kerstin Alexandra Klotz, Hiltrud Muhle, Michael Alber, Regina Trollmann, Hartwig Spors, Gerhard Kluger, Gerhard Kurlemann, Susanne Schubert-Bast

• Objective: Dravet syndrome (DS) is a rare but severe drug-resistant epilepsy. Before the approval of fenfluramine (FFA) for the treatment of seizures in DS, patients in Germany could receive treatment under a compassionate use program (CUP). Methods: We conducted a multicenter, retrospective, observational study to describe the efficacy, tolerability, and retention of FFA within the CUP. Patients received add-on therapy with oral FFA gradually titrated to a target dose between .13 and .7 mg/kg/day. Results: Overall, 78 patients with DS (median age = 8.0 years, range = 2.1–46.0; 53% female, median concomitant antiseizure medications [ASMs] = 3) were treated with FFA for a median duration of 255.5 days (range = 31–572). Responder rates (a ≥50% reduction; n = 78) and seizure-freedom rates at 3 months were 68% and 14% for total seizures, respectively, and 67% and 23% for generalized tonic–clonic seizures. Responder rates were consistent at 6 and 12 months (n = 66 and n = 43, respectively). Median seizure days per month significantly decreased from 10.0 (range = .5–30) to 3.0 (range = 0–30) in the 3-month period before and after FFA treatment (p < .001). Significantly fewer patients reported at least one episode of status epilepticus (28% vs. 14% patients before and after FFA initiation, p = .005). During FFA treatment, 35 (45%) patients were able to discontinue a concomitant ASM. At the last follow-up date, 66 (85%) patients remained on treatment with FFA. The most common adverse events were somnolence (36%), decreased appetite (22%), and ataxia (8%). Forty-eight (62%) patients were reported as having a meaningful global clinical improvement. Significance: In a large cohort of patients, FFA demonstrated efficacy across a range of outcomes including clinically significant reductions in convulsive seizures, and was well tolerated, providing valuable information for real-world practice. Key Points: Seventy-eight patients with Dravet syndrome were treated with FFA at multiple centers within the CUP in Germany; FFA had a good retention rate over a sustained period; 85% of patients remained on treatment with FFA for a median duration of 255.5 days; FFA was associated with clinically meaningful reductions in total and convulsive seizures, seizure days per month, and episodes of status epilepticus; FFA was associated with reductions in the number or dose of concomitant antiseizure medications in 68% of patients; FFA was well tolerated, with the main adverse events being somnolence (36%), decreased appetite (22%), and ataxia (8%).