Safety Study of Idebenone to Treat Friedreich's Ataxia

This study will determine the highest dose of idebonone that can safely be given to patients with Friedrich's ataxia, an inherited degenerative disease that causes loss of muscle coordination, speech problems, weakness and sensory loss. Enlargement of the left ventricle (the large pumping chamber of the heart) is also common in this disease. In studies in France and Canada, patients with Friedrich's ataxia who were given idebonone, an antioxidant similar to the dietary supplement coenzyme Q, had a decrease in the size of their left ventricle. Patients 5 years and older with Friedrich's ataxia may be eligible for this study. Pregnant and lactating women may not participate. Candidates will be screened with a medical history and physical examination and a review of genetic studies. Patients who have not had genetic studies will be offered genetic counseling and testing to confirm or rule out Friedrich's ataxia. Participants will be admitted to the NIH Clinical Center for 3 days. They will have blood and urine tests and a heart evaluation, including an echocardiogram-a procedure that uses sound waves to produce images of the heart, and an electrocardiogram-a study of the electrical activity of the heart. When these tests have been completed, patients will take an idebonone capsule. They will be monitored for side effects for 72 hours. Blood samples will be collected through an intravenous catheter (flexible plastic tube placed in a vein) 0.5, 1, 2, 3, 4, 6, 12, 24, 48 and 72 hours after the drug is taken to determine how long it takes for the drug to be eliminated from the body. Patients will return for a follow-up visit within 1 to 8 weeks. Those who experienced no serious side effects may receive another, higher dose of the drug, with at least 6 days between doses.

Friedreich's ataxia (FRDA) is a progressive, autosomal recessive, multisystem degenerative disease for which there is currently no effective treatment. Recent studies suggest that lipid-soluble antioxidants may prevent the progression of neurodegeneration and lead to some reversal of cardiomyopathy. This will be a phase Ia, unblinded, dose-escalation trial examining the toxicity and tolerability of the antioxidant idebenone in patients with FRDA. Our primary objective is to determine the maximum tolerated single dose of idebenone in patients with FRDA. Our secondary objective is to document the pharmacokinetics of single-dose idebenone in this population. We aim to enroll 48 patients divided evenly among three age cohorts: children (ages 5-11), adolescents (ages 12-17), and adults (age greater than or equal to 18). Each age cohort will be studied independently. Three patients from each cohort will receive one day of oral idebenone followed by inpatient monitoring for 72 hours. If dose-limiting toxicity (DLT) is not observed during the 72-hour study period, three new patients will receive the next highest dose. If one of three patients experiences DLT, three new patients will receive the same dose. Within each cohort, the dose will be escalated until the maximum tolerated dose (MTD) is established. The MTD will be defined as one dose below that which resulted in DLT in any two patients within a cohort. Subsequent to the completion of this phase Ia trial, we plan to further refine the MTD for each age group in a phase Ib trial in which we will examine multiple-dose regimens over a longer study period. We hope to follow these phase I studies with a double-blinded, placebo-controlled phase II trial to further evaluate safety and to estimate the efficacy of idebenone using cardiac parameters as our primary endpoints. In addition, we are currently in the process of validating a clinical evaluation scale for FRDA that we hope to employ in measuring neurological parameters as a secondary endpoint in the phase II trial.