CARE‐HD.

Methods	120‐week double‐blind, four‐arm parallel study. Method of randomisation: computer generated stratification by investigator. Results presented for each arm of the trial. Intention‐to‐treat data analysis. Location: 25 centres (USA).
Participants	347 patients, 37 drop‐outs. 176 male and 171 female patients completed the trial. Mean age of participants: 47.9±10,5 years. Mean duration of disease: 4,9±3,1 years. Inclusion criteria: HD (genetically established or positive family history) TFC‐UHDRS≥7, disease stage I or II. Exclusion criteria: Coenzyme Q10 use in previous 3 months, unstable medical or psychiatric disease.
Interventions	Coenzyme Q10, 300‐600mg/day (87 patients), remacemide, 400‐600mg/day (86 patients) or Coenzyme Q10+remacemide , 300‐600mg/day+400‐600mg/day (87 patients) and placebo ‐ identical pills (87 patients). No titration.
Outcomes	Primary: deteriorarion in TFC‐UHDRS. Secondary: Change in TMS‐UHDRS. Change in cognitive function (Stroop test, Hopkins Verbal Learning Test, Brief Test Attention, Conditional Associative Learning Test, Trailmaking test, Test for visuomotor speed). Frequency and severity of individual adverse events, abnormal values or changes of laboratory tests and ECG results, changes from baseline to 30 months in laboratory test and vital signs.
Notes	Negative for efficacy measures.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Unclear risk	B ‐ Unclear