Huntington's disease (HD) is an inherited autosomal dominant, progressive neurodegenerative disease. Clinically, HD is characterized by a triad of movement disorders, cognitive impairments and psychiatric disturbances. These symptoms represent a tremendous burden for patients and caregivers. HD is a fatal disorder with neither cure, nor evidence-based standard therapy available.

The green tea polyphenon (2)-epigallocatechin-3-gallate (EGCG) was shown to have beneficial effects in cell and animal models of HD. The aim of this study is to evaluate the efficacy and tolerability of EGCG in HD.

The investigators hypothesize that Sunphenon EGCG administered at a maximal daily dose of 1200 mg compared to placebo during a period of 12 months improves cognition in patients with HD. As primary outcome measure, the change of cognitive functions (as measured by the Unified Huntington's Disease Rating Scale (UHDRS)-Cognition composite score of Stroop test, Verbal fluency & Symbol Digit Modalities Test) after 12 months in comparison to Baseline was defined.

The investigators further expect a positive influence of EGCG on other clinical manifestations of HD, measurable effects of EGCG on HD biomarkers and good safety and tolerability of EGCG in HD patients.

Inclusion Criteria:

• Chorea Huntington (CAG repeats >39)
• UHDRS TFC >5
• ≥18 years of age
• Readiness and ability to take oral medication
• Normal liver function laboratory test
• Stable concomitant medication regimen > 4 weeks prior to Baseline
• Motivation for women with childbearing potential to use highly efficient contraception

Exclusion Criteria:

• Clinically relevant abnormal findings in the ECG, vital signs, physical examination or laboratory values at Screening,
• Long-term treatment with potentially hepatoxic medication
• Any unstable medical condition
• BDI Depression score > 9 AND clinical diagnosis of depression
• Suicidal tendencies
• Cognitive dysfunction defined as a score < 23 in the Mini-Mental State Examination (MMSE) at Screening
• Liver or renal disease
• Schizophreniform psychosis within the last 6 months before baseline
• Consumption of more than two cups of black tea per day, consumption of green tea, consumption of > 500 ml /day of grapefruit juice
• Participation in other Arzneimittelgesetz (AMG) or Medizinproduktegesetz (MPG) studies (three months before and during participation)
• Pregnancy/ lactation