• Safety measures (complete blood count, chemistry profile, electrocardiogram, urinalysis) [ Time Frame: 35 days ] [ Designated as safety issue: Yes ]
  
• Tolerability measures (adverse event severity) [ Time Frame: 35 days ] [ Designated as safety issue: Yes ]
  
• Pharmacokinetic measures (Serum and CSF levels of bile acids) [ Time Frame: 28 days ] [ Designated as safety issue: No ]
  

Huntington's disease is an inherited neurodegenerative disease that causes a movement disorder, dementia, and psychiatric and behavioral disturbance in affected individuals.

Tauroursodeoxycholic acid (TUDCA) is a bile acid synthesized in the liver by the conjugation of taurine to ursodeoxycholic acid (UDCA). It is thought to function as an anti-apoptotic agent in HD, evidenced by studies in toxic cell models and both toxic and transgenic rodent models of the disease.

Ursodiol is a commercially-available exogenous form of UDCA, the precursor of TUDCA. Although the compound has an established dosing, safety, tolerability and efficacy profile in patients with hepatobiliary disorders, gaps exist in the understanding of the pharmacokinetics / pharmacodynamics of the compound, particularly in patients with normal gastrointestinal function, and no human data exist for its therapeutic use in neurodegenerative disorders. The specific aims of this study are:

1. To establish whether treatment with the drug ursodiol will result in measurable levels of its bile acid metabolites in serum and CSF at standard oral doses; and whether a dose-response can be detected using these measures.
2. To establish a preliminary safety and tolerability profile of the drug in subjects with HD.