Randomized, phase III study results of clobazam in Lennox-Gastaut syndrome.

OBJECTIVE: To evaluate efficacy and safety of clobazam, a 1,5-benzodiazepine, as adjunctive therapy for Lennox-Gastaut syndrome (LGS).

METHODS: Patients aged 2-60 years were randomized to placebo or clobazam 0.25, 0.5, or 1.0 mg/kg/day. Study consisted of 4-week baseline, 3-week titration, and 12-week maintenance phases, followed by a 2- or 3-week taper or continuation in an open-label extension. Primary endpoint was percentage decrease in mean weekly drop seizure rates during maintenance vs baseline phases for modified intention-to-treat (mITT) population. Secondary outcomes included other seizure types, responder rates, and physicians' and caregivers' global assessments.

RESULTS: A total of 305 patients were screened, 238 were randomized, and 217 composed the mITT population. Of patients enrolled after a protocol amendment, 125/157 (79.6%) completed. Average weekly drop seizure rates decreased 12.1% for placebo vs 41.2% (p = 0.0120), 49.4% (p = 0.0015), and 68.3% (p < 0.0001) for the clobazam 0.25-, 0.5-, and 1.0-mg/kg/day groups. Responder rates (≥50%) were 31.6% (placebo) vs 43.4% (p = 0.3383), 58.6% (p = 0.0159), and 77.6% (p < 0.0001) for clobazam 0.25-, 0.5-, and 1.0-mg/kg/day groups. Physicians' and caregivers' assessments indicated clobazam significantly improved symptoms. Somnolence, pyrexia, upper respiratory infections, and lethargy were the most frequent adverse events reported for clobazam.

CONCLUSIONS: Clobazam significantly decreased weekly drop seizure rates in LGS. No new safety signals were identified.

CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that clobazam as adjunctive therapy is efficacious, in a dosage-dependent manner, in reducing mean weekly drop seizure rates of patients with LGS over 12 weeks.