In December 2013, Deerfield invested in Auspex Pharmaceuticals as the lead investor in a $20 million Series E private financing. Auspex is a biopharmaceutical company focused on the development and commercialization of novel medicines for the treatment of orphan diseases, based on the company’s expertise in deuterium chemistry. At the time of the financing, the company’s lead product candidate, SD-809, was in a Phase 3 registration clinical trial for the treatment of chorea (abnormal involuntary movements) associated with Huntington’s disease. Tetrabenazine (marketed as Xenazine(r) in the United States) has been the only therapy approved by the U.S. Food and Drug Administration, or FDA, for this indication.