New symptomatic therapies for Huntington disease.

Huntington disease (HD), an inherited neurodegenerative disease, results from a CAG repeat expansion creating mutant huntingtin protein and widespread neuronal damage. Motor symptoms such as chorea are often preceded by cognitive and behavioral changes. Tetrabenazine and deutetrabebenazine are the two drugs approved by the Federal Food and Drug Administrationfor HD symptoms, is an effective therapy for chorea. However, there is still a large need for other symptomatic therapies impacting functional issues, including impaired gait, behavioral, and cognitive symptoms. A number of pharmacologic agents are under investigation. Additionally, other mechanisms are being targeted in motor symptom drug development, including phosphodiesterase 10 enzyme inhibition, dopamine modulation, and inhibition of deacetylation. There is perhaps the greatest unmet need in treating nonmotor effects, such as cognition and change in disease course. PBT2, a metal chaperone, and latrepirdine, a mitochondrial stabilizer, are under investigation specifically for the possibility of cognitive benefit. Unfortunately, there is a lack of HD-specific evidence on effective treatments for behavioral and psychiatric symptoms. Further investigation of nonmedication interventions such as physical therapy is necessary. As our understanding of molecular and cellular mechanisms underlying HD broadens, a new set of mechanistic targets will become the focus of HD symptomatic therapies.