Soticlestat as an adjunctive therapy in children and young adults with Dravet syndrome

OBJECTIVE: This study evaluated the efficacy, safety, and tolerability of soticlestat as adjunctive therapy in children and young adults with Dravet syndrome (DS). METHODS: SKYLINE (NCT04940624) was a multicenter, randomized, double-blind, placebo-controlled, phase 3 trial that enrolled patients with DS aged 2-21 years with uncontrolled convulsive seizures (≥4/month despite adequate treatment). Participants received oral soticlestat 300 mg (weight adjusted) or matching placebo twice daily. The total study duration was 16 weeks, comprising 4-week dose titration and 12-week maintenance treatment periods. The primary endpoint was a comparison of monthly convulsive seizure frequency between baseline and the titration/maintenance periods. Key secondary endpoints included several modified Caregiver and Clinical Global Impression of Improvement (GI-I) scales for DS. RESULTS: One hundred forty-four participants were randomized (71 placebo, 73 soticlestat) with a mean (SD) age of 10.3 (5.0) years; 72 (50%) were male, and 117 (81.3%) were receiving ≥3 antiseizure medications. Median change from baseline in convulsive seizure frequency over the full treatment period was -8.64% with placebo (n = 71) and -22.16% with soticlestat (n = 73), a difference of -15.64% (p = .061); in the maintenance treatment period, these changes were -11.99% with placebo and -23.29% with soticlestat, a difference of -14.29% (p = .089). The proportion of participants with ≥50% reduction in convulsive seizures was 9.9% with placebo and 27.4% with soticlestat (nominal p = .008). Soticlestat showed clinically meaningful results in the Caregiver and Clinical GI-I, and Clinical GI-I Seizure Intensity and Duration scales over the 16-week treatment period (all nominal p-values ≤ .004). The most commonly reported treatment-emergent adverse events related to study drug were somnolence, change in seizure presentation, decreased appetite, and insomnia. SIGNIFICANCE: Although statistical significance was narrowly missed, soticlestat showed a numerical benefit over placebo for convulsive seizure decrease. Clinically meaningful benefits across multiple secondary endpoints were observed. No new safety concerns emerged.