In the 12-week ARM-TD and AIM-TD studies evaluating deutetrabenazine for the treatment of tardive dyskinesia (TD), the percentage of patients achieving ≥50% response was higher in the deutetrabenazine-treated group than in the placebo group. These studies also showed low rates of overall adverse events (AEs) and discontinuations associated with deutetrabenazine. The current open-label study evaluated the long-term efficacy and safety of deutetrabenazine in patients with TD.

Patients with TD who completed ARM-TD or AIM-TD could enroll in this open-label, single-arm extension study, titrating up over 6 weeks to a maximum total daily dose of deutetrabenazine 48 mg/day on the basis of dyskinesia control and tolerability. The proportion of Abnormal Involuntary Movement Scale (AIMS; items 1-7) responders was assessed based on response rates for achieving ≥50% improvement from baseline in the open-label extension study. AlMS score was assessed by local site raters for this analysis.

343 patients enrolled in the extension study. At Week 54 (n=249; total daily dose [mean ± standard error]: 38.6±0.66 mg), the mean percentage change from baseline in AIMS score was –40%; 48% of patients achieved a ≥50% response and 59% of those had already achieved a ≥50% response at Week 15. Further, 34% of those who had not achieved a ≥50% response at Week 15 achieved a ≥50% response at Week 54. At Week 106 (n=169; total daily dose: 39.6±0.77 mg), the mean percentage change from baseline in AIMS score was –45%; 55% of patients achieved a ≥50% response, 59% of those patients had already achieved a ≥50% response at Week 15, and 41% of those who had not achieved a ≥50% response at Week 15 but who reached Week 106 achieved a ≥50% response. At Week 132 (n=109; total daily dose: 39.7±0.97 mg), the mean percentage change from baseline in AIMS score was –61%; 55% of patients achieved a ≥50% response, 61% of those patients had already achieved a ≥50% response at Week 15, and 43% of those who had not achieved a ≥50% response at Week 15 but who reached Week 132 achieved a ≥50% response. Completer analysis suggests that long-term efficacy was not due to dose increases over time. Treatment with deutetrabenazine was generally well tolerated. There were 623 patient-years of exposure through Week 158, and exposure-adjusted incidence rates (incidence/patient-years) of adverse events of special interest were 0.01 for akathisia and restlessness, 0.07 for somnolence and sedation, 0.04 for parkinsonism, and 0.05 for depression.

Patients who received long-term treatment with deutetrabenazine achieved response rates that were indicative of clinically meaningful long-term benefit. Results from this open-label trial suggest the possibility of increasing benefit over time with individual dose titration of deutetrabenazine.

This study was funded by Teva Pharmaceuticals, Petach Tikva, Israel.