Background: Tardive dyskinesia results from exposure to dopamine receptor antagonists, such as typical and atypical antipsychotics. If clinically appropriate, clinicians often manage this disorder by lowering the dose of, or discontinuing, the causative drug. There is a significant unmet need for a treatment option that does not disrupt treatment regimens for underlying psychiatric illnesses. We aimed to assess the efficacy, safety, and tolerability of fixed doses of deutetrabenazine-a novel vesicular monoamine transporter-2 inhibitor-in patients with tardive dyskinesia.

Methods: We did this double-blind, randomised, placebo-controlled, phase 3 trial at 75 centres in the USA and Europe. Patients aged 18-80 years with tardive dyskinesia (≥3 months before screening) were randomly assigned centrally (1:1:1:1), via interactive response technology, to receive one of three fixed doses of deutetrabenazine (12 mg/day, 24 mg/day, or 36 mg/day) or matching placebo. Randomisation was stratified by baseline use of dopamine receptor antagonists. Patients were started on oral deutetrabenazine 12 mg/day, and this dose was increased through week 4 until the randomised dose was achieved, then maintained over 8 weeks. During the treatment period, patients, investigators, their site personnel, and sponsor were masked to group assignment. The primary efficacy endpoint was change in Abnormal Involuntary Movement Scale (AIMS) score from baseline to week 12 in patients with at least one post-baseline rating. The primary efficacy analysis was done in the modified intention-to-treat population (baseline AIMS score ≥6 and at least one post-baseline rating). The safety analysis was done in patients who received any study drug. This trial is registered with ClinicalTrials.gov, numberNCT02291861.

Findings: Between Oct 29, 2014, and Aug 19, 2016, we randomly assigned 298 patients to receive at least one dose of placebo (n=74), deutetrabenazine 12 mg/day (n=75), 24 mg/day (n=74), or 36 mg/day (n=75); 222 patients comprised the modified intention-to-treat population and 293 patients comprised the safety population. From baseline to week 12, the least-squares mean AIMS score improved by -3·3 points (SE 0·42) in the deutetrabenazine 36 mg/day group, -3·2 points (0·45) in the 24 mg/day group, and -2·1 points (0·42) in the 12 mg/day group, with a treatment difference of -1·9 points (SE 0·58, 95% CI -3·09 to -0·79; p=0·001), -1·8 points (0·60, -3·00 to -0·63; p=0·003), and -0·7 points (0·57, -1·84 to 0·42; p=0·217), respectively, versus -1·4 points (0·41) in the placebo group. The rate of adverse events was similar between patients in the deutetrabenazine 36 mg/day group (n=38/74 [51%]), 24 mg/day group (n=32/73 [44%]), and 12 mg/day group (n=36/74 [49%]), and those in the placebo group (n=34/72 [47%]). Serious adverse events were reported in four (5%) patients given deutetrabenazine 36 mg/day, six (8%) patients given 24 mg/day, and two (3%) patients given 12 mg/day, compared with four (6%) patients given placebo. Two (1%) patients in the safety population died, one each in the deutetrabenazine 24 mg/day and 36 mg/day groups; neither death was deemed related to study drug by the investigator or sponsor.

Interpretation: Deutetrabenazine 24 mg/day and 36 mg/day provided a significant reduction in tardive dyskinesia, with favourable safety and tolerability. These findings suggest that dosing regimens could be individualised and tailored for patients on the basis of dyskinesia control and tolerability.

Funding: Teva Pharmaceutical Industries.