Clinical Data
An unusually high placebo effect, extending beyond that expected from previous studies, limited the ability to determine treatment effects on assessments of HD motor scores. Evidence of symptomatic impact, however, was seen in the early stage HD patient sub-population, with improvement in Total Motor Score (TMS) and dystonia observed at 26 and 52 weeks in this patient sub-set (stage 1 HD) at specific doses.The discovery of pridopidine's previously unknown mode of action as a potent agonist of the Sigma 1 Receptor (S1R) resulted in a change in PRIDE-HD study design, from a 26-week study focused on symptoms, to a 52-week study focused on exploring pridopidine’s potential impact on disease progression, as measured by Total Functional Capacity (TFC). TFC is the most widely accepted and validated tool for assessing disease stage in HD. It has been used as the endpoint in more than 10 previous clinical trials of drugs seeking to demonstrate an impact on HD progression, none of which were successful.This study showed a statistically significant impact on the endpoint of disease progression at 52 weeks following treatment with pridopidine at certain doses versus placebo, as measured by TFC. The effect of pridopidine was further evident in a sub-population of patients with early stage HD, an effect first observed at 26 weeks.