This study compares efficacy and side effects of the three most commonly prescribed corticosteroid regimens in young boys with Duchenne muscular dystrophy (DMD). 

Corticosteroids improve muscle function in boys with DMD and should be considered for all newly diagnosed patients, according to care recommendations. However, uncertainty regarding regimen and side effects has led to great variability in corticosteroid use. Corticosteroids are likely to be used in DMD for the foreseeable future.

In a randomized, double-blind, parallel-group clinical trial involving 32 sites in 5 countries, 196 corticosteroid-naïve boys age 4-7 years were randomized 1:1:1 to receive daily prednisone (0.75 mg/kg/day), daily deflazacort (0.9 mg/kg/day), or intermittent prednisone (0.75 mg/kg 10-days on/10-days off). Boys were assessed for three years. The three-dimensional primary outcome comprised rise from the floor velocity, forced vital capacity, and participant/parent global satisfaction with treatment. Secondary efficacy outcomes included 10-meter walk/run velocity, 6-minute walking distance and North Star Ambulatory Assessment total score. Safety outcomes included height and weight, behavioral measures, and frequency and severity of adverse events.

Daily prednisone and deflazacort were superior to intermittent, 10-days on/10- days off, prednisone for the primary outcome and all secondary motor function outcomes.  There were no significant differences in efficacy between daily prednisone and deflazacort.  There was greater weight gain with both daily and intermittent prednisone regimens than with deflazacort. Slowing of growth was less severe with the intermittent regimen than with the daily regimens, with daily deflazacort associated with the greatest slowing of growth.

Daily steroid regimens demonstrated significantly greater efficacy in motor function than the intermittent, 10 days on 10 days off, prednisone regimen. The data support the standardization of corticosteroid prescription at the time of treatment initiation and could facilitate the interpretation of efficacy outcomes of clinical trials targeting young boys with DMD.