News Feature | December 23, 2014

Auspex Pharma's Drug For Huntington's Disease Chorea Succeeds In Late-Stage Trials

By C. Rajan, contributing writer

California-based biopharmaceutical company, Auspex Pharmaceuticals, has announced positive topline efficacy and safety results from two phase 3 trials evaluating its investigational drug, SD-809, for the treatment of chorea associated with Huntington's disease (HD)

The two Phase 3 trials, First-HD and Arc-HD, were designed to evaluate SD-809 (deuterated Tetrabenazine) for the treatment of chorea in HD patients as well as the drug’s effect in patients switching from the standard-of-care drug Tetrabenazine to SD-809, respectively. The drug met all the primary and secondary goals for efficacy and safety in both trials.

Based on the positive data from the trials, Auspex plans to file a New Drug Application (NDA) for SD-809 for the treatment of chorea in HD patients by mid-2015.

"For many individuals with Huntington's disease, chorea is a key symptom impacting safety, function, and quality of life. New, safe, and tolerable therapies for chorea treatment are clearly needed to make this disease an increasingly treatable condition," said Samuel A. Frank, M.D., associate professor of neurology, Boston University School of Medicine, and principal investigator for First-HD.

The pivotal First-HD trial is a placebo-controlled study evaluating SD-809 in 90 HD patients with chorea. The goals of the study were to assess the safety, tolerability, and efficacy of SD-809 in the management of Huntington's-associated chorea. The trial met the primary efficacy endpoint and also demonstrated significant improvements in quality of life, rates of depression, somnolence, restlessness, and other associated symptoms.

The second clinical trial, ARC-HD Switch, enrolled 37 HD patients with chorea and assessed their transition from stable doses of tetrabenazine to SD-809. The results showed successful maintenance of chorea in patients after switching to SD-809 at 1 week and 4 week time points.

SD-809 is a deuterium substituted version of the neurological drug Tetrabenazine, which is the current standard of care. Tetrabenazine works by inhibiting the VMAT2 transporter that packages dopamine and other neurotransmitters for release into the synapse.

Tetrabenazine has been reported to have several problems and side effects, however. The excellent safety profile and tolerability, as well as success in secondary end-points shown by SD-809, will give it an edge over Tetrabenazine.

Tetrabenazine is marketed as Xenazine (Lundbeck) in the U.S. and is expected to lose its market exclusivity in August 2015, reports Reuters.

Huntington's disease, a genetic disorder, causes progressive neurodegeneration that impacts movements, behavior, and cognition. Over 30,000 people in the U.S. and Canada have Huntington's disease, and many others have the genetic predisposition to develop HD.

Approximately 90 percent of people with Huntington's disease develop its most debilitating symptom called chorea, which is characterized by involuntary, excessive movements in all parts of the body. There is no available cure for Huntington's disease, and current treatments only focus on managing the symptoms of the disease.

Auspex is also evaluating SD-809’s potential for treating other related neurodegenerative movement disorders, including tardive dyskinesia (ARM-TD pivotal study) and Tourette syndrome (Phase 1b study). The company says that it anticipates reporting the results from these studies by mid-2015.