A phase I study of oral vitamin D3 in boys with X-linked adrenoleukodystrophy

ObjectiveVitamin D status has been linked to risk of inflammatory brain lesions. We sought to assess the safety and pharmacokinetics of oral vitamin D dosing regimens in boys with X-linked adrenoleukodystrophy (ALD).MethodsIn this open-label, multi-center, phase I study, we enrolled 21 ALD males without brain lesions, aged 1.5 to 25 years to oral vitamin D supplementation for 12 months. Our primary outcome was attainment of plasma 25-hydroxyvitamin D levels in target range (40-80ng/ml) at 6 and 12 months. Secondary outcomes included safety and glutathione levels in brain and blood. Participants were initially assigned to a fixed dosing regimen starting at 2,000 IU daily, regardless of weight. Following a mid-study safety assessment, we modified the dosing regimen so all subsequent participants were assigned to a weight-stratified dosing regimen starting as low as 1,000 IU daily.ResultsBetween October 2016 and June 2019, we recruited 21 participants (n=12 fixed dose; n=9 weight-stratified) with a median age and weight of 6.7 years and 20 kilograms. Most participants achieved target plasma vitamin D levels at 6 and 12 months regardless of dosing regimen. In the fixed dose regimen, 6 of 12 participants had asymptomatic elevation in urine calcium:creatinine or plasma 25-hydroxyvitamin D; no laboratory deviations occurred with the weight-stratified regimen. Glutathione levels increased between baseline and 12 months in the brain but not in the blood.ConclusionsOur weight-stratified vitamin D dosing regimen was well-tolerated and achieved target 25-hydroxyvitamin D levels in most participants. Brain glutathione levels increased over the 12-month trial period.Clinicaltrials.gov identifierNCT02595489Classification of EvidenceThis study provides Class II evidence that a weight-stratified dosing regimen of vitamin D supplementation is safe, well-tolerated, and effective at achieving moderately high vitamin D levels in boys with ALD.Sources of fundingNIH/NINDS K23NS087151