OBJECTIVES: Huntington disease is a hereditary neurodegenerative disorder 
resulting in loss of motor, cognitive, and behavioral functions and is 
characterized by a distinctive pattern of cerebral metabolic abnormalities. 
Pridopidine (ACR16) belongs to a novel class of central nervous system compounds 
in development for the treatment of Huntington disease. The objective of the 
study was to investigate the metabolic changes in patients with Huntington 
disease before and after pridopidine treatment.
METHODS: [(18)F]Fluorodeoxyglucose positron emission tomographic imaging was 
used to measure the regional cerebral metabolic rate of glucose at baseline and 
after 14 days of open-label pridopidine treatment in 8 patients with Huntington 
disease. Clinical assessments were performed using the Unified Huntington's 
Disease Rating Scale.
RESULTS: Statistical parametric mapping analysis showed increased metabolic 
activity in several brain regions such as the precuneus and the mediodorsal 
thalamic nucleus after treatment. In addition, after pridopidine treatment, the 
correlation between the clinical status and the cerebral metabolic activity was 
strengthened.
CONCLUSIONS: Our findings suggest that pridopidine induces metabolic changes in 
brain regions implicated as important for mediating compensatory mechanisms in 
Huntington disease. In addition, the finding of a strong relationship between 
clinical severity and metabolic activity after treatment also suggests that 
pridopidine treatment targets a Huntington disease-related metabolic activity 
pattern.