Objective: This double-blind, randomized, placebo-controlled Phase 2 study (NCT01462292) assessed the 24-week efficacy, safety, tolerability, and pharmacokinetics of two different subcutaneous drisapersen doses, and the 24-week off-dose persistent effect, in ambulant Duchenne muscular dystrophy (DMD) patients.
Methods: Male DMD patients (≥5 years; time to rise from floor ≤15 s) were randomized to drisapersen 3 mg/kg/week, 6 mg/kg/week or placebo. The primary efficacy endpoint was change from baseline in 6-minute walking distance (6MWD) at week 24. Secondary endpoints included changes in timed function tests, muscle strength, and pulmonary function tests.
Results: Fifty-one patients were randomized to placebo (N = 16), drisapersen 3 mg/kg/week (N = 17) or 6 mg/kg/week (N = 18). All but 2 patients had baseline rise from floor time <7 s. This study was exploratory and not prospectively powered; however, a difference in mean 6MWD versus placebo in favor of drisapersen 6 mg/kg/week was observed at week 24 (27.1 m; P = 0.069) and maintained 24 weeks off-treatment (27.9 m; P = 0.177). The 3 mg/kg/week group showed no statistically significant difference in mean 6MWD versus placebo. For some secondary endpoints, a more positive response in favor of drisapersen 6 mg/kg/week compared to placebo was shown. Drisapersen had a long half-life with steady state reached after approximately 36 weeks. Most common adverse events in both drisapersen groups were related to injection site reactions and subclinical proteinuria.
Interpretation: Drisapersen 6 mg/kg/week for 24 weeks resulted in a treatment benefit in 6MWD, largely maintained 24 weeks off-treatment. This study provided insights for further studies to optimize dosage regimen.