Phase 3 data comparing deflazacort and prednisone indicate that deflazacort improves muscle strength and causes less weight gain than prednisone compared with placebo. The data, published in Neurology,1 have been submitted as support for Marathon Pharmaceutical’s New Drug Application (NDA) for deflazacort, which was granted Priority Review by the US Food and Drug Administration (FDA) for the treatment of Duchenne muscular dystrophy.
The complete data support the daily use of deflazacort to help preserve muscle strength in patients with Duchenne muscular dystrophy.
“Corticosteroids are the only treatment that increases muscle strength in boys with Duchenne muscular dystrophy. Importantly, this study showed that both deflazacort and prednisone increase strength over placebo, and deflazacort is associated with less weight gain than prednisone,” study investigator and lead author Robert C. Griggs, MD, of the University of Rochester in New York, said in a statement.2 “With currently no FDA-approved treatment for Duchenne and no cure, deflazacort may provide an important treatment option for delaying the progression of Duchenne.”
The double-blind, randomized, placebo-controlled, multicenter study evaluated muscle strength over a 52-week period in 196 boys aged 5 to 15 years with Duchenne muscular dystrophy. The study included a 12-week phase 1 period in which participants were randomly assigned to receive deflazacort 0.9 mg/kg/d, 1.2 mg/kg/d, prednisone 0.75 mg/kg/d, or placebo. In phase 2, which ran for an additional 40 weeks, participants in the treatment groups continued treatment and those assigned to placebo in phase 1 were randomly assigned to 1 of the 3 treatment groups.
In phase 1, a statistically significant improvement in muscle strength was observed at 12 weeks for deflazacort 0.9 mg/kg/d (0.25 vs 20.1, P = .017, 95% CI 0.04-0.46), deflazacort 1.2 mg/kg/d (0.36 vs 20.1, P = .0003, 95% CI 0.14-0.57), and prednisone 0.75 mg/kg/d (0.37 vs 20.1, P = .0002, 95% CI 0.15-0.59) compared with placebo. Additionally, statistically significant improvements in motor function in time from supine to standing (deflazacort 0.9 mg/kg/d [P = .0018], deflazacort 1.2 mg/kg/d [P = .0002], prednisone [P = .0016]); time to climb 4 stairs (P < .0001 for all treatment groups); and time to run or walk 30 feet (P < .0001 for all treatment groups) were observed in all 3 treatment groups compared to placebo.
In phase 2, participants randomly assigned to receive either dose of deflazacort continued to see improved muscle strength through weeks 12 to 52 while worsening strength was observed in participants taking prednisone. Notably, a significant improvement in average muscle strength from week 12 to 52 was observed in the deflazacort 0.9 mg/kg/d group compared with the prednisone group (least squares [LS] mean 0.29, P = .044, 95% CI 0.08-0.49). Those receiving deflazacort 1.2 mg/kg/d saw improvement, but it was not statistically significant (LS mean 0.16, P = .18, 95% CI 20.06-0.37).