VMAT2 inhibitors for the treatment of tardive dyskinesia

Tardive dyskinesia (TD) is an often disabling hyperkinetic movement disorder caused by exposure to dopamine receptor blocking agents. Although initially thought to most commonly occur with typical antipsychotics, the incidence is likely similar with atypical antipsychotics and antiemetics such as metoclopramide. Increased prescribing of these agents as well as low rates of remission have contributed to a rising prevalence of TD. Although this condition was described nearly 60 years ago, it is only within the past year that two novel therapeutic agents were FDA approved. Characterization of the VMAT2 inhibitor tetrabenazine, which was identified as a therapeutic agent for TD in older clinical trials, has yielded two distinct pharmacologic strategies to optimize response. The first strategy, used to create deutetrabenazine, employed deuterization of tetrabenazine to stabilize the pharmacokinetics and eliminate high peak plasma levels. The second strategy was the creation of a prodrug, valbenazine, for the two most active isoforms of tetrabenazine that also resulted in more stable pharmacokinetics and eliminated peak plasma levels. Both agents have been demonstrated to be effective and safe for the treatment of TD in multicenter, controlled trials and their development has led to a resurgence of interest in the characterization and treatment of this movement disorder.