Huntington's treatment hope after trial success

9 March 2010

A new dopamine-regulating drug improves motor function and may slow disease progression in patients with Huntington's disease, a Phase III trial has shown.

A neurone from the striatum of the brain showing accumulation of huntingtin (fluorescent areas), the mutant protein that is responsible for Huntington's disease.

Pridopidine (Huntexil) belongs to a class of medicines called dopaminergic stabilisers. These agents, typified by the antipsychotic aripiprazole (Abilify), counteract the effects of both excessive and insufficient dopaminergic activity.

Dopaminergic stabilisers have the potential to treat a wider range of Huntingdon's symptoms with a better tolerability profile than the currently licensed treatment, tetrabenazine (Xenazine 25). This drug promotes the degradation of dopamine, primarily relieving the hyperkinetic symptoms of the disease.

In the double-blind MermaiHD trial, investigators randomised a total of 437 patients to receive pridopidine 45mg once or twice daily, or placebo.

After 6 months, patients receiving pridopidine twice daily showed significant improvements in voluntary movements (p<0.02), global motor function (p<0.001) eye movements (p<0.002) and dystonia (p<0.001). They also exhibited a significant improvement in cognitive function (p<0.05).

The findings were comparable in patients taking and not taking antipsychotic medication. Pridopidine had a similar safety profile to that of placebo and did not appear to worsen cognitive or psychiatric symptoms.

Subsequent analysis of the MermaidHD results indicated that pridopidine might also have disease-modifying properties, in addition to its effect on symptoms. The drug was estimated to slow disease progression by up to 6–18 months.

NeuroSearch, the developer of pridopidine, expects to report data from a 12-month open-label extension of the MermaiHD trial in late 2010.