Minimal clinically important change in Abnormal Involuntary Movement Scale score in tardive dyskinesia as assessed in pivotal trials of deutetrabenazine

Abstract

IntroductionDeutetrabenazine is approved by the US Food and Drug Administration to treat tardive dyskinesia (TD) based on 2 pivotal, 12-week, placebo-controlled studies (ARM-TD and AIM-TD) evaluating safety and efficacy in patients with baseline total motor Abnormal Involuntary Movement Scale (AIMS) score ≥6. This analysis estimated the minimal clinically important change (MCIC) in total motor AIMS score in TD patients treated with deutetrabenazine. MethodsThe pooled analysis population included all patients in ARM-TD and AIM-TD who received study drug and had ≥1 postbaseline AIMS assessment. MCIC analyses were performed using Patient Global Impression of Change (PGIC) and Clinical Global Impression of Change (CGIC) as anchors. MCIC was defined as the mean change from baseline in total motor AIMS score in patients treated with deutetrabenazine who were rated minimally improved on PGIC or CGIC at Week 12. ResultsThis analysis included 295 patients (deutetrabenazine, n = 197; placebo, n = 98). At Week 12, the MCIC in deutetrabenazine-treated patients was −2.4 based on the PGIC and −2.1 based on the CGIC. Mean change from baseline in total motor AIMS score for placebo-treated patients rated minimally improved was −1.4 based on the PGIC and −1.5 based on the CGIC. The proportion of deutetrabenazine-treated patients who achieved improvement in total motor AIMS score by ≥2 and ≥3 points was 66% and 55%, respectively. ConclusionUsing anchor-based methodology, the MCIC on the AIMS for deutetrabenazine in patients with TD was approximately −2, suggesting that a reduction in total motor AIMS score of ∼2 is associated with clinically meaningful improvement in TD symptoms.