Valbenazine for tardive dyskinesia: A systematic review of the efficacy and safety profile for this newly approved novel medication-What is the number needed to treat, number needed to harm and likelihood to be helped or harmed?

OBJECTIVE

The objective of this systematic review was to describe the efficacy, tolerability, and safety of valbenazine for the treatment of tardive dyskinesia (TD).

DATA SOURCES

The pivotal registration trials were accessed by querying http://www.ncbi.nlm.nih.gov/pubmed/ and http://www.clinicaltrials.gov, for the search terms 'valbenazine' OR 'NBI-98854', and by also querying the EMBASE (Elsevier) commercial database for clinical poster abstracts, and by asking the manufacturer for copies of posters presented at congresses. Product labeling provided additional information.

STUDY SELECTION

All available clinical reports of studies were identified.

DATA EXTRACTION

Descriptions of the principal results and calculation of number needed to treat (NNT) and number needed to harm (NNH) for relevant dichotomous outcomes were extracted from the available study reports and other sources of information.

DATA SYNTHESIS

Valbenazine, a reversible inhibitor of Vesicular Monoamine Transporter Type 2 (VMAT2), received approval for the treatment of TD in adults based on a clinical trial development programme that included three 6-week parallel group, randomised, placebo-controlled studies, including one Phase III trial described in product labeling. The recommended dose for valbenazine is 80 mg/d. The percentage of responders in the Phase III acute study, as defined by ≥50% reduction from baseline in the Abnormal Involuntary Movement Scale dyskinesia score was 40.0% for valbenazine 80 mg/d vs 8.7% for placebo, yielding a NNT of 4 (95% CI 3-6). As pooled from available data, discontinuation rates because of an adverse event were 2.9% for valbenazine-treated patients vs 1.6% for placebo-treated patients, resulting in a NNH of 76 (ns). The only adverse event that met the threshold of incidence ≥5% for valbenazine and a rate of ≥2 times than that observed with placebo was somnolence (somnolence, fatigue, sedation), with rates of 10.9% for valbenazine (all doses) vs 4.2% for placebo, resulting in a NNH of 15 (95% CI 9-52). An additional warning and precaution is that valbenazine can prolong the ECG QT interval, however, the valbenazine product label does not contain any bolded boxed warnings or contraindications.

CONCLUSIONS

Valbenazine is presently the only US Food and Drug Administration-approved agent specifically indicated for the treatment of TD. Valbenazine is about 15 times more likely to result in a response than in a discontinuation because of an adverse event. Head-to-head comparisons with other VMAT2 inhibitors among patients with TD in the 'real world' are needed.