A phase II, open-label, non-comparative study of Botulinum toxin in Restless Legs Syndrome

To assess the efficacy of intradermally injected botulinum neurotoxin type A (BoNT/A) in patients with Restless Legs Syndrome (RLS).

We conducted an optimal two-stage, phase II exploratory, open label, non-comparative clinical trial. The primary outcome measure was the efficacy of BoNT/A defined by the proportion of patients (responders) with ⩾50% improvement of their RLS severity score at week 2 following injections compared to baseline score at inclusion. Twenty-seven patients were to be included in the first stage of the trial, which was to be stopped if less than nine responders were documented. Selected patients had a minimum score of 21 on the International RLS Rating Scale. They all received a series of 20 intradermal injections of 0.05 ml of BoNT/A in symptomatic areas in their lower limbs. Change of RLS severity was evaluated over a 6 months period.

Of the 27 selected patients, only six achieved the primary endpoint at week 2. In these six patients, the median duration (Inter-Quartile Range) of the IRLSRS score improvement of at least 50% was 46 days (42-126).

Considering the proportion of responders as the primary endpoint of this trial, BoNT/A showed no efficacy in alleviating RLS sensory symptoms.