Auspex shares rocket up after Huntington's drug hits the mark in Phase III

Auspex Pharmaceuticals' ($ASPX) treatment for a movement disorder tied to Huntington's disease met its main goal in a late-stage study, the company said, clearing the way for a 2015 FDA filing. And the news ignited an 81% spike in its stock price.

The drug, SD-809, is designed to stop the abnormal involuntary movements spurred by chorea, a condition that afflicts about 90% of Huntington's sufferers, according to Auspex. In a placebo-controlled trial on 90 patients, treatment with SD-809 led to a statistically significant improvement in patients' Total Maximal Chorea (TMC) scores, a measure of the disorder's effect. The drug reduced TMC values by 2.5 points more than placebo, a statistically significant result that met the primary endpoint of the study, dubbed First-HD.

SD-809 also met three of its four secondary goals, charting significant improvements in patient and clinical impressions of change and quality of life. The drug improved patients' performance on the Berg balance test but failed to hit statistical significance on that measurement, Auspex said.

On the safety side, SD-809 was well tolerated across the board, according to the company, with one dropout in the treatment arm compared with two in the placebo group. Adverse event rates were similar across both arms of the study, and one patient in each group experienced a severe reaction, Auspex said. The also drug put up similar results in four-week data from an ongoing study called ARC-HD Switch, which is designed to determine its long-term safety, the biotech said.

Now Auspex says it's on track to submit an application for Huntington's-associated chorea by the middle of next year, the first of many planned indications for the drug.

Auspex CEO Pratik Shah

"The strong efficacy and safety results seen in both the First-HD and ARC-HD Switch studies confirm our belief in SD-809 as a highly promising new medicine for the treatment of chorea associated with Huntington's disease," CEO Pratik Shah said in a statement. "Patients with chorea associated with Huntington's disease have been waiting for too long for a new therapeutic option.... In addition, we remain fully committed to exploring the therapeutic promise of SD-809 in other movement disorders, including tardive dyskinesia and Tourette syndrome."

As it stands, the only FDA-approved treatment for chorea associated with Huntington's is Lundbeck's Xenaxine (tetrabenazine), which brought in about $240 million last year. Auspex believes SD-809 can expand the existing market because it requires less frequent and lower doses than its competitor. With that in mind, ARC-HD Switch, the ongoing safety study, is also designed to provide guidance to physicians on how to transition patients from Xenaxine to SD-809, though it is not powered to compare the treatments' relative efficacy.

The promise of SD-809 helped Auspex raise $84 million in an upsized IPO earlier this year. The biotech is now trading at nearly four times its debut price.

- read the results

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