Once-daily USL255 as adjunctive treatment of partial-onset seizures: randomized phase III study.

Objective: To evaluate the efficacy and safety of USL255, Qudexy(™) XR (topiramate) extended-release capsules, as an adjunctive treatment for refractory partial-onset seizures (POS) in adults taking one to three concomitant antiepileptic drugs.

Methods: In this global phase III study (PREVAIL; NCT01142193), 249 adults with POS were randomized 1:1 to once-daily USL255 (200 mg/day) or placebo. The primary and key secondary efficacy endpoints were median percent reduction in weekly POS frequency and responder rate (proportion of patients with ≥ 50% reduction in seizure frequency).