Confirmatory long-term efficacy and safety results of ataluren in patients with nmDMD from Study 041, an international, randomized, double-blind, placebo-controlled, Phase III trial

<b>Aim:</b> To report the efficacy and safety of ataluren in patients with nonsense mutation Duchenne muscular dystrophy (nmDMD) from the phase III, 72-week, placebo-controlled period of Study 041. <b>Materials & methods:</b> Inclusion criteria: boys with nmDMD aged ≥5 years, on a stable corticosteroid regimen for ≥12 months, and baseline 6-minute walk distance (6MWD) ≥150 m. Randomization: 1:1, ataluren (40 mg/kg/day):placebo. Primary end point: slope of 6MWD change (average rate of change). Secondary end points: changes in 6MWD, time to 10% persistent worsening in 6MWD, North Star Ambulatory Assessment score, timed function tests and safety. Study populations: intention-to-treat; patients aged ≥7 to ≤16 years with baseline 6MWD ≥300 m and stand from supine ≥5 s; patients with baseline 6MWD 300-400 m. <b>Results:</b> In the intention-to-treat population (n = 359), over 72 weeks, ataluren reduced the rate of 6MWD decline by 21% (p = 0.0248), reduced the average 6MWD change (p = 0.0248), delayed time to 10% persistent worsening in 6MWD (p = 0.0078), and reduced North Star Ambulatory Assessment total score decline (p = 0.0235), change in 10 m walk/run time (p = 0.0422) and change in time to climb four stairs (p = 0.0293) versus placebo. In the 6MWD 300-400 m subgroup (n = 169), ataluren reduced the rate of 6MWD decline by 30% (p = 0.0310) versus placebo. Ataluren treatment benefits were seen in secondary end points in this subgroup, except for change in time to descend four stairs. In the 6MWD ≥300 m and time to stand from supine ≥5s subgroup (n = 185), there was a 9% slower rate of 6MWD decline for ataluren versus placebo over 72 weeks (p = 0.3626). Ataluren reduced change in time to climb four stairs (p = 0.0179) versus placebo in this subgroup; no treatment benefits were seen for other secondary end points. Ataluren was well tolerated (serious adverse events: ataluren, 7.1%; placebo, 6.8%); no deaths occurred. <b>Conclusion:</b> Long-term ataluren treatment has a favorable benefit-risk profile, slowing motor function decline in the largest phase III nmDMD study to date.