HP THERAPEUTICS FOUNDATION, INC.

The purpose of this study is to collect prospective data from individuals who are part of a Huntington Disease (HD) family, in order to relate phenotypes between individuals and families with each other and genetic factors in order to learn more about HD, develop potential treatments for HD, and to plan for future research studies of experimental drugs aimed at slowing or postponing the onset and progression of HD.

The purpose of this study is to evaluate the safety, tolerability and clinical impact of 15-grams daily of sodium phenylbutyrate (phenylbutyrate) in Huntington's disease and to lay the groundwork for possible subsequent trials designed to specifically address its ability to slow or halt the progression of the disease.