An Open‐Label Pilot Study to Examine the Safety, Tolerability and Efficacy of Deutetrabenazine in Isolated Dystonia

ABSTRACT Background Dystonia may respond to VMAT2 inhibition. Objectives Providing pilot data on the safety, tolerability, and efficacy of deutetrabenazine in non dopa‐responsive dystonia. Methods Deutetrabenazine was titrated by adults with isolated dystonia. Primary study endpoints included the proportion who maintained the individual, maximum tolerated dose for 6 weeks, and how many titrated to 48 mg/day. Secondary endpoints included rates of QTc prolongation/arrhythmias, suicidality, excessive daytime sleepiness, cognitive decline, and drug‐induced parkinsonism. Exploratory endpoints for clinical efficacy were assessed. Results Among 15 participants, four (26.7%) withdrew early and six (40%) titrated to 48 mg/day. Common adverse events included fatigue and diarrhea. Secondary safety endpoints did not change significantly, but MDS‐UPDRS III scores worsened by ≥3 points in seven participants (46.7%). PGI‐C and the blinded CGI‐C and GDS improved in three women with blepharospasm. Conclusions Most participants tolerated deutetrabenazine for 6 weeks, and those with blepharospasm may have benefitted from its use.