Neurological effects of high-dose idebenone in patients with Friedreich's ataxia: a randomised, placebo-controlled trial.
BACKGROUND
Friedreich's ataxia (FA) is a progressive, multisystem, degenerative disorder caused by a reduction in frataxin. Loss of frataxin results in mitochondrial dysfunction and oxidative damage in patients and model systems. Previous studies have indicated that the antioxidant idebenone (5 mg/kg daily) reduces cardiac hypertrophy, but definite improvement in neurological function has not been shown.


METHODS
48 genetically confirmed FA patients, aged 9-17 years, were enrolled in a 6-month, randomised, double-blind, placebo-controlled study. The patients received placebo or one of three doses of idebenone (approximately 5 mg/kg, 15 mg/kg, and 45 mg/kg), stratified by body weight. The primary endpoint was change from baseline in urinary 8-hydroxy-2'-deoxyguanosine (8OH2'dG), a marker of oxidative DNA damage. Secondary endpoints included changes in the international cooperative ataxia rating scale (ICARS), the FA rating scale (FARS), and a survey of activities of daily living (ADL). This study is registered with ClinicalTrials.gov, number NCT00229632.


RESULTS
Idebenone was generally well tolerated with similar numbers of adverse events in each group. One child receiving high-dose idebenone developed neutropenia after 6 months, which resolved after discontinuation of treatment. 8OH2'dG concentrations were not increased, and did not significantly change with idebenone treatment. Whereas an overall analysis did not show a significant difference in ICARS, FARS, or ADL total scores, there were indications of a dose-dependent response in the ICARS score. A second, pre-specified analysis, excluding patients who required wheelchair assistance, showed a significant improvement in ICARS (Bonferroni p=0.03) and suggested a dose-related response in ICARS, FARS, and ADL scores.


CONCLUSIONS
Treatment with higher doses of idebenone was generally well tolerated and associated with improvement in neurological function and ADL in patients with FA. The degree of improvement correlated with the dose of idebenone, suggesting that higher doses may be necessary to have a beneficial effect on neurological function.
Di Prospero
Nicholas A
NA
Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-3705, USA. diprospern@ninds.nih.gov
Baker
Angela
A
Jeffries
Neal
N
Fischbeck
Kenneth H
KH
D000080242:8-Hydroxy-2'-Deoxyguanosine; D000203:Activities of Daily Living; D000293:Adolescent; D000975:Antioxidants / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D016227:Benzoquinones / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D002648:Child; D004249:DNA Damage; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000652:urine; D004305:Dose-Response Relationship, Drug; D005260:Female; D005621:Friedreich Ataxia / Q000188:drug therapy* / Q000235:genetics / Q000503:physiopathology* / Q000652:urine; D006801:Humans; D008297:Male; D009420:Nervous System / Q000187:drug effects* / Q000503:physiopathology*; D009503:Neutropenia / Q000139:chemically induced; D012720:Severity of Illness Index; D014451:Ubiquinone / Q000031:analogs & derivatives