J011 Pridopidine demonstrates consistent improvements in Q-Motor measures and early benefits (26 weeks) in Q-Motor predict long-term changes in function and cUHDRS in PROOF-HD

<h3>Background</h3> Q-Motor is an objective measure of motor function that is centrally read, lacks inter- and intra-rater variability, shows high reliability, and has minimal or no placebo response. Q-Motor shows consistent baseline correlations with core, independent clinical endpoints including, cUHDRS, TFC, TMS, SWR, SDMT, CAP-scores and brain-volume across numerous observational and clinical studies. <h3>Aims</h3> To assess the efficacy of pridopidine in Q-Motor measures in participants from the PROOF-HD study. <h3>Methods</h3> Q-Motor tests ‘finger tapping’ (FT, digitomotography) and ‘pronate/supinate hand tapping’ (PS, dysdiadochomotography) were collected and analyzed centrally. <h3>Results</h3> In all subjects, irrespective of antidopaminergic medication (ADM [neuroleptics and VMAT2 inhibitors]) use, Q-Motor measures favored pridopidine at all timepoints through 78 weeks. In subjects off ADMs, pridopidine’s benefit is greater in all Q-Motor measures assessed, including FT IOI mean at all visits (26-weeks, p&lt;0.0001; 52-weeks, p=0.017; 65-weeks, p=0.013; and 78-weeks, p=0.003). Similar improvements are observed in PS Inter-Tap-Interval (ITI) mean. The robust benefits of pridopidine are maintained in subjects on lower doses of ADMs, as per the regulatory label for ADMs in the presence of a CYP2D6 inhibitor such as pridopidine. Early changes in Q-Motor (26 weeks) are highly predictive of long-term changes in numerous clinical measures, including TFC and cUHDRS (≥52 weeks). The predictability of Q-Motor measures are irrespective of ADM use. <h3>Conclusion</h3> Pridopidine demonstrated improvements in Q-Motor assessments at all timepoints irrespective of ADM use, with strongest and most significant effects in subjects off ADMs. Early benefits in Q-Motor were predictive of long-term benefits on key clinical outcome measures of disease progression.