A recent press release from Auspex Pharmaceuticals reported on an interim analysis from their ongoing ARC-HD trial that switching from tetrabenazine (Xenazine®) to SD-109, resulted in equal control of chorea in Huntington's disease. SD-109 is a chemically modified form of tetrabenazine that allows for a lower dosing regimen. It is hoped that lower dosing of SD-109 will result in fewer side effects than the present form tetrabenazine.