MONDAY AUG. 18, 2008 (FDA) -- The U.S. Food and Drug Administration has approved Xenazine (tetrabenazine) for the treatment of chorea in people with Huntington’s disease. Chorea is the jerky, involuntary movement that occurs in people with this disease.

Xenazine is a new drug and is the first treatment of any kind approved in the United States for any symptom of Huntington’s disease. Currently there are no other drugs that are FDA-approved to treat chorea.

Serious side effects reported with use of Xenazine include depression and suicidal thoughts and actions. Xenazine should not be used in patients who are actively suicidal or in patients with untreated depression. Concerns about the risk of suicide are heightened in all patients with Huntington’s disease.

“Xenazine represents hope for patients and families dealing with this difficult disease,” said Timothy Coté, M.D., M.P.H., director of FDA’s Office of Orphan Products Development. “For the first time, there is a treatment that can help patients with this disease gain some quality of life.”

Huntington's disease is a rare, inherited neurological disorder affecting about 1 in 10,000 people in the United States. The disease results from genetically programmed degeneration of brain cells. The deterioration causes uncontrolled movements, loss of intellectual faculties, and emotional disturbance. Huntington’s disease is passed from parent to child through a gene mutation. Each child of a parent with the disease has a 50 percent chance of inheriting the mutation.

About 30,000 people in the United States have Huntington’s disease and another 200,000 are at risk of developing the condition. Symptoms commonly develop between ages 30 and 50. The disease progresses slowly and a person may live for another 15-20 years after the onset of symptoms.

Xenazine decreases the amount of dopamine available to work at relevant synapses in the brain. Dopamine is a chemical that communicates between certain nerve cells in the brain. In patients with Huntington’s disease, this system is overactive and results in the abnormal movements called chorea. Xenazine decreases the amount of dopamine available to interact with certain nerve cells, thereby decreasing the involuntary movements.

The effectiveness and safety of Xenazine was established primarily in a randomized, double-blind, placebo-controlled multi-center clinical trial. Patients treated with Xenazine had a significant improvement in chorea compared to patients treated with placebo. Other studies provided additional support for this effect.

The most common side effects reported by patients using Xenazine in clinical trials include insomnia, depression, drowsiness, restlessness and nausea.

While the drug has been shown to decrease chorea in the short-term, it also showed slight worsening in mood, cognition, rigidity, and functional capacity in clinical trials. Health care professionals and family members of patients taking the drug should pay attention to all of the facets of the disease.

Xenazine has been approved with a required Risk Evaluation and Mitigation Strategy (REMS) to ensure that the benefits of the drug outweigh its risks, particularly the risks of depression and suicidal thoughts and actions. REMS is a strategy to manage a known or potential serious risk associated with a drug or biological product.

The REMS includes educational materials for prescribers, pharmacists and patients (and their caregivers) to help minimize adverse effects associated with Xenazine. It also includes a Medication Guide, which informs patients and their caregivers about the risks of depression, suicidal thoughts and actions, and other side effects. The FDA requires that the Medication Guide be handed out with every prescription for the drug dispensed.

Xenazine was granted orphan drug designation by the FDA. A drug is eligible for orphan drug designation if it is intended to treat a disease or condition that affects less than 200,000 people in the United States. A drug is also eligible for orphan drug designation if it is intended to treat a disease or condition that affects more than 200,000 people in the United States, but there is no reasonable expectation that the cost of developing and making available a drug for the disease or condition will be recovered from sales of the drug.

Xenazine is manufactured by Prestwick Pharmaceuticals, Inc., Washington, D.C.

For more information

FDA: Questions and Answers on Risk Evaluation and Mitigation Strategies
http://www.fda.gov/cder/regulatory/FDAAA/FR_QA.htm

FDA: Office of Orphan Products Development
www.fda.gov/orphan

National Institute of Neurological Disorders and Stroke: Huntington's Disease Information Page
www.ninds.nih.gov/disorders/huntington/huntington.htm