Genetics

08 July 2016

New drug eases Huntington's disease symptoms

If approved by the FDA, deutetrabenazine may provide another treatment option, making Huntington's disease an increasingly treatable condition.

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An experimental drug may help control the involuntary, sudden muscle movements associated with Huntington's disease, with fewer side effects, according to the results of a small trial.

Fatal genetic disorder

"Deutetrabenazine is not yet FDA-approved, but assuming it becomes available, practicing clinicians may have another choice for their individual patients," said lead researcher Dr Samuel Frank. He is a neurologist and instructor at Harvard Medical School in Boston.

The involuntary movements associated with Huntington's disease are called chorea.

Huntington's disease is a fatal genetic disorder. It causes the progressive destruction of nerve cells in the brain. Symptoms vary from person to person. People who have Huntington's lose their physical and mental abilities over 10 to 25 years. The disease has no cure, according to the Huntington's Disease Society of America (HDSA).

Read: Predictive testing for Huntington's: ethical and social questions

Every child with a parent with Huntington's disease has a 50 percent chance of carrying the faulty gene. Approximately 30,000 Americans have symptomatic Huntington's disease. More than 200,000 are at risk of inheriting the disease, the HDSA says.

The choice of drugs to treat chorea should be based on safety, effectiveness, cost to patients and the best chance of compliance, Frank said.

"The opportunity to possibly improve quality of life should be part of the decision-making process as well," he said. "If approved by the FDA, deutetrabenazine may provide another treatment option, making Huntington's disease an increasingly treatable condition."

A number of side effects

Funding for the trial was provided by the maker of the drug, Auspex Pharmaceuticals, a subsidiary of Teva Pharmaceutical Industries, Ltd.

Currently, tetrabenazine (Xenazine) is the only drug approved by the US Food and Drug Administration for treating chorea in Huntington's disease, the study authors said.

Read: Prenatal testing for Huntington's disease

Although the drug is effective, tetrabenazine often has to be taken three times a day and can cause side effects, such as sedation, fatigue, anxiety or nausea, the researchers said.

For the new study, Frank and his colleagues randomly assigned 90 patients with Huntington's disease and chorea to receive either deutetrabenazine or a placebo.

Over eight weeks, the dose of deutetrabenazine was increased to a level at which it was most effective. That dose was maintained over four weeks, the study authors said.

Larger trials underway

"We found that deutetrabenazine reduces chorea, the hallmark movement disorder in Huntington disease," Frank said. "There was also an overall improvement in participants' condition and improvement in a quality-of-life measure. There was, however, no improvement in balance."

The rate of side effects was similar for the drug and a placebo, which included depression, anxiety and akathisia (a movement disorder), the researchers found.

Read: Huntington's disease

Frank said larger trials are underway to assess the long-term safety and effectiveness of deutetrabenazine.

The study findings were published in the Journal of the American Medical Association.

One neurologist said he would like to have seen a head-to-head comparison between deutetrabenazine and tetrabenazine.

Both equally effective

"I wish they had included a tetrabenazine arm and a placebo arm," said Dr Michael Geschwind. A professor of neurology at the University of California, San Francisco, he co-wrote an editorial accompanying the study results.

Such a trial is needed to see which drug is superior, Geschwind said. "But for FDA approval, they only have to show it's better than placebo," he said.

Looking at this trial and another that compared tetrabenazine with a placebo, Geschwind found that both drugs appeared to be equally effective. However, deutetrabenazine had fewer side effects, he said.

"If a patient is doing well on tetrabenazine and tolerating it well, I wouldn't consider changing it," Geschwind said. "But if I were starting a new patient and the drugs were similar in cost, I'm probably going to go to the new drug because out of the starting gate I'm probably going to have fewer side effects."

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