The first effective treatment for the symptoms of Huntington's disease has now been approved by the U.S. Food and Drug Administration after study results by the Huntington Study Group and Baylor College of Medicine in Houston showed the drug's effectiveness.
Tetrabenazine, to be marketed as Xenazine, eases the abnormal involuntary movement, known as chorea, associated with Huntington's disease. Chorea is thought to be caused by overactivity of the neurotransmitter dopamine.
"Tetrabenazine works by depleting dopamine levels in the brain," said Dr. Joseph Jankovic, professor of neurology and director of the Parkinson Disease Center and Movement Disorder Clinic at BCM.
Huntington's disease is a rare, inherited neurological disorder affecting about 1 in 10,000 people in the United States. About 30,000 people in the United States have Huntington's disease and another 200,000 are at risk of developing the condition.
"In 1979 I was granted special permission from the FDA to treat patients with the drug," said Jankovic, also distinguished chair in movement disorders at BCM. "Since that time I've treated thousands of people with tetrabenazine and have seen amazing results that translated into marked improvement in the quality of life".
When the FDA began the approval process for tetrabenazine, Jankovic and his colleagues presented experience with the drug accumulated over more than a quarter of century. In addition Jankovic and his colleagues at BCM participated in a double-blind, placebo controlled multi-center clinical trial conducted by the Huntington Study Group involving more than 80 participants to establish effectiveness and safety. Those who were treated with tetrabenazine had a significant improvement in chorea compared to patients treated with placebo. Despite some side effects, such as mood changes, slowness of movement, insomnia, restlessness and nausea, the FDA panel unanimously recommended approval of the drug.
"Other drugs used in the past to treat Huntington's disease resulted in permanent side effects, including tardive dyskinesia which is a drug induced movement disorder," Jankovic said. "This side effect has not occurred with tetrabenazine and most other side effects can be lessened with smaller dosages without lasting effect."
Xenazine, developed in the United States by Prestwick Pharmaceuticals, Inc, has been approved with a required Risk Evaluation and Mitigation Strategy to ensure the benefits of the drug outweigh its risks.