A decision by regulators in the USA to give the green light to Prestwick Pharmaceuticals’ Xenazine, the first therapy to be approved in the country for the most common symptom of Huntington's Disease, has been warmly welcomed.

Privately-owned Prestwick has announced that the US Food and Drug Administration has approved Xenazine (tetrabenazine) for the treatment of chorea associated with HD. The approval is based on a Phase III study found that the drug, a selective and reversible centrally-acting dopamine depleting treatment, significantly reduced patients' chorea burden (excessive, involuntary and repetitive movements) and was generally safe and well tolerated.

The company noted that the drug will be marketed under an FDA-approved risk evaluation plan to decrease the risk of depression and suicidal ideation that may be associated with Xenazine. The therapy has orphan drug status, giving Prestwick seven years’ market exclusivity in the USA, where around 30,000 people are affected by HD>

The response to the approval from charities dealing with the disease has been very positive. The Hereditary Disease Foundation noted that chorea “is not just a mere inconvenience; it can prevent HD patients from walking, talking, working [and] watching television”. Nancy Wexler, president of the HDF, said that “while we are still hopeful we can some day find a cure, the approval of Xenazine is a breakthrough” and the organisation is “ecstatic”.

Barbara Boyle, chief executive of the Huntington's Disease Society of America said that the approval is “a great moment for our families, who have been waiting for answers to HD for a long time". Those people “should be proud that their advocacy efforts helped make a difference” in persuading the FDA to back the drug, she added.

The UK’s Cambridge Laboratories licensed the US and Canadian rights to Prestwick in 2002 and 2004 respectively and it is also approved in 14 other countries, most recently in the Netherlands, Sweden and Switzerland.