To evaluate the safety (primary objective) and efficacy (secondary objective) of (−)-OSU6162 in Huntington’s disease (HD).

In a double-blind, cross-over trial, patients with HD were randomly assigned to start treatment on either (−)-OSU6162 or placebo. After 4 weeks, those patients who initially received active drug were switched to placebo for another 4 weeks, and vice versa. During the first week the (−)-OSU6162 dose was 15 mg twice daily, during the second week 30 mg twice daily, and during the last 2 weeks 45 mg twice daily. Motor, cognitive, mental and social functions were rated by the clinical investigator or by self-assessment, using established rating scales.

Fifteen patients fulfilling inclusion and exclusion criteria completed the study. (−)-OSU6162 was well tolerated by all patients and no adverse effects were observed. (−)-OSU6162 treatment significantly improved the Short Form 36 Vitality score, mainly due to an improvement of the individual item ‘worn-out’ (VT3). In addition, an improvement of depressive symptoms was found using Beck Depression Inventory. In contrast to a general trend of improvement in several non-motor variables only small and non-significant differences between (−)-OSU6162 and placebo were found regarding motor functions.

(−)-OSU6162 offers promise for the treatment of HD, as a drug with good tolerability, capable of improving the patients’ experienced non-motor functions such as energy and mood and thus alleviating symptoms of great importance for their quality of life.