Efficacy and tolerability of sumanirole in restless legs syndrome: a phase II, randomized, double-blind, placebo-controlled, dose-response study.

OBJECTIVE: To compare the efficacy, safety and tolerability of sumanirole with placebo in patients with idiopathic restless legs syndrome (RLS).

METHODS: In this double-blind, placebo-controlled, randomized, parallel-group, dose-response study, 270 patients with idiopathic RLS were enrolled and randomized to receive sumanirole 0.5, 1.0, 2.0, or 4.0mg, or placebo. The primary efficacy endpoint was mean change of the total score of the International Restless Legs Scale (IRLS-10), a 10-item scale, from baseline to end of maintenance. Secondary assessments included polysomnography (PSG) variables.

RESULTS: Treatment with sumanirole was well tolerated. Mean change in IRLS-10 showed no statistically significant change compared with placebo at any dose, although the mean change with the 4.0-mg dose was numerically greater than the other doses and placebo. PSG variables, specifically the periodic leg movements during sleep, showed statistically significant dose-related improvement in favor of sumanirole. Consistent with earlier multinational, multicenter studies in RLS, high placebo response rates were seen with IRLS-10 but not with PSG variables.

CONCLUSIONS: Given data published in Parkinson's disease, the dose range of sumanirole selected here may have been too low. Alternatively, dopamine D(2) selective agents could be intrinsically less effective than agonists with combined D(2)/D(3) activity. Sumanirole demonstrated an excellent safety profile.