Efficacy of gabapentin enacarbil in adult patients with severe primary restless legs syndrome

Aim: Assess efficacy and tolerability of gabapentin enacarbil (GEn) in adults with severe primary restless legs syndrome (RLS). Methods: We pooled data from three 12-week, double-blind, placebo-controlled, randomized trials (NCT00298623, NCT00365352, NCT01332305) across GEn 600-mg, GEn 1200-mg, and placebo treatment groups for severe primary RLS (baseline International Restless Legs Scale (IRLS) total score ≥24). Co-primary end points at week 12 were mean change from baseline in IRLS total score and proportion of responders ("much"/very much" improved) on the investigator-rated Clinical Global Impression - Improvement (CGI-I) Scale. Outcomes for individual IRLS items (eg, sleep, mood, quality of life, pain, safety) were assessed. Results: A total of 309 patients had severe primary RLS (placebo, n = 110; GEn 600 mg, n = 80; GEn 1200 mg, n = 119). GEn 600 mg and 1200 mg significantly improved least-squares mean IRLS total scores versus placebo at week 12 (placebo, -12.3; GEn 600 mg, -16.3; GEn 1200 mg, -18.0; treatment difference vs. placebo, both p < 0.01). Significantly more patients with severe primary RLS treated with GEn 600 mg (64%) and 1200 mg (74%) were CGI-I responders at week 12 versus placebo (42%; p < 0.01 for both GEn doses). Both GEn doses led to significant improvements in the other outcomes explored versus placebo at week 12. The most frequent treatment-emergent adverse events (TEAEs) were somnolence (GEn, 21-24%; placebo, 3%) and dizziness (GEn, 14-19%; placebo, 3%). Conclusions: GEn (600 mg or 1200 mg) once daily significantly improved RLS symptoms and consequences of these symptoms in severe primary RLS. The most frequent TEAEs were somnolence and dizziness.