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Published online by Cambridge University Press: 24 April 2020
Tardive dyskinesia (TD) is a persistent and potentially disabling movement disorder associated with prolonged exposure to antipsychotics and other dopamine receptor blocking agents. Valbenazine is a highly selective vesicular monoamine transporter 2 (VMAT2) inhibitor approved for the treatment of TD in adults. Using data from a long-term study (KINECT 3; NCT02274558), the effects of once-daily valbenazine (40 mg, 80 mg) on TD were assessed using the Abnormal Involuntary Movement Scale (AIMS) in participants who were early responders based on subjective measures, including patient self-report (Patient Global Impression of Change [PGIC]) or clinician judgment (Clinical Impression of Change-Tardive Dyskinesia [CGI-TD]).
Data from KINECT 3 (6-week double-blind, placebo-controlled [DBPC] period; 42-week double-blind extension) were analyzed post hoc. Long-term outcomes included mean change from baseline to Week 48 in AIMS total score (sum of items 1-7) and AIMS response (≥50% total score improvement from baseline) at Week 48. These AIMS outcomes were assessed in participants who achieved early improvement, defined as a PGIC or CGI-TD score of ≤3 (“minimally improved” or better) at Week 2 (first post-baseline visit of the DBPC period). Participants who initially received placebo were not included in the analyses.
In participants who received only valbenazine (40 or 80 mg) during KINECT 3 and had available Week 2 assessment, 50% (72/143) had early PGIC improvement (score ≤3) and 43% (61/142) had early CGI-TD improvement (score ≤3). Baseline characteristics were generally similar between participants who achieved early PGIC or CGI-TD improvement and those who did not. Based on available assessments at Week 48, mean AIMS total score change from baseline in participants with early PGIC improvement was similar to those who did not reach the early PGIC improvement threshold (-4.1 [n=35] vs -3.5 [n=41]). Mean AIMS total score change from baseline in participants with early CGI-TD improvement was similar to those who did not achieve early CGI-TD improvement (-4.2 [n=31] vs -3.5 [n=45]). AIMS response at Week 48 was also similar in those who achieved early PGIC and CGI-TD improvement (40% and 42%, respectively) compared to those who did not achieve early PGIC and CGI-TD improvement (39% and 38%, respectively).
Results from this long-term valbenazine trial indicate that many participants achieved at least minimal patient- and clinician-reported improvement at Week 2. AIMS outcomes at Week 48 demonstrated long-term reductions in TD severity regardless of early response. More research is needed to understand the association between early improvement and long-term treatment effects, but early non-improvement based on subjective measures may not be predictive of long-term treatment failure.
International Congress of Parkinson’s Disease and Movement Disorders; September 22-26, 2019; Nice, France.
This study was sponsored by Neurocrine Biosciences, Inc.
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