A phase 3, randomized clinical trial of soticlestat as adjunctive therapy for Lennox-Gastaut syndrome

There remains a need for new treatments for Lennox-Gastaut syndrome (LGS), a developmental and epileptic encephalopathy with a heterogenous patient population that often requires polytherapy. The phase 3, randomized SKYWAY study (NCT04938427) investigated the efficacy and safety of the cholesterol 24-hydroxylase inhibitor soticlestat (TAK-935) in participants with LGS.

This global, double-blind, placebo-controlled trial enrolled participants aged 2-55 years with LGS (adjudicated by the Epilepsy Study Consortium). Participants were randomized 1:1 to stable background medication plus either soticlestat (≤300 mg twice daily, weight-adjusted) or placebo over 16 weeks (4-week titration plus 12-week maintenance). The primary endpoint was percentage change from baseline in major motor drop (MMD) seizure frequency per 28 days.

SKYWAY enrolled 270 participants (placebo, n = 136; soticlestat, n = 134); mean age was 12.9 years; 95% were receiving ≥2 antiseizure medications. The difference in median change from baseline in MMD seizure frequency for soticlestat versus placebo was -1.17% (p = .785) during the full treatment period and 2.43% (p = .778) during maintenance. No meaningful difference was observed between soticlestat and placebo for most key secondary endpoints; numerical trends for small effects favoring soticlestat were seen in the proportions of participants showing improvement in the Clinical Global Impression of Improvement (CGI-I) Non-seizure Symptoms Disruptive Behaviors domain (odds ratio = 1.91, nominal p = .032) and CGI-I Seizure Intensity and Duration (odds ratio = 1.67, nominal p = .029). Treatment-related adverse events (TEAEs; mostly mild or moderate) were reported in 68.4% of placebo-treated and 74.6% of soticlestat-treated participants; the most frequent treatment-related TEAE with soticlestat was somnolence. Serious treatment-related TEAEs occurred in one placebo-treated and three soticlestat-treated participants.

Soticlestat did not demonstrate efficacy versus placebo in reducing MMD seizure frequency; the safety findings were consistent with those of previous studies. These data suggest that targeting cholesterol 24-hydroxylase is not a suitable pharmacotherapeutic strategy for LGS.