Teva's Huntington's disease therapy starts US review

Teva's treatment for symptoms associated with Huntington's disease could be on the market next year in the US, as the FDA has now started to review the drug.

SD-809 (deutetrabenazine) is an improved version of an existing drug called tetrabenazine that is already sold by Lundbeck as Xenazine to treat chorea (involuntary muscle movements) in Huntington's, a serious neurodegenerative disorder that affects about five to seven people per 100,000 in western countries.

The deuterated form of the molecule seems to be less likely to cause side effects than Xanazine, including depression and anxiety, and also appears to be more effective in controlling chorea.

Teva has estimated that only 5 percent of Huntington's patients actually receive treatment with the drug due to side effects, although Lundbeck was still able to achieve revenues of $245 million from the brand last year thanks to a price of $60,000 to $70,000 a year.

The Israeli drugmaker acquired rights to SD-809 when it bought Auspex in a $3.5bn deal agreed in March.

The company has been trying to boost its pipeline and reduce its reliance on multiple sclerosis therapy Copaxone (glatiramer acetate), which has started to lose patent protection and is now subject to generic competition in a number of markets including the US.

The US filing is based on the results of two Phase 3 trials - FIRST-HD and ARC-HD - which looked at the drug in comparison to placebo and tetrabenazine, respectively.

The FIRST-HD study showed SD-809 was more effective than placebo in reducing chorea in patients with Huntington's, while ARC-HD study demonstrated that patients were able to safely convert from tetrabenazine to SD-809 overnight with continued control of symptoms.

Teva is also developing SD-809 for the movement disorder tardive dyskinesia (TD), which often develops as a complication of treatment with psychoactive drugs and would be a much larger market than Huntington's, as well as Tourette's syndrome. Xenazine is reported to be used off-label in TD.