Ataluren is conditionally approved by the European Medicines Agency to treat nonsense mutation Duchenne muscular dystrophy (nmDMD).

The design of a phase 3 randomized, double-blind, placebo-controlled trial with an open-label extension period evaluating long-term efficacy and safety of ataluren in nmDMD (Study 041) will be presented.

Inclusion critera are evidence of nmDMD, age ≥ 5 y, corticosteroid use ≥12 months, 6-minute walk distance (6MWD) ≥ 150 m, and performance of timed function tests (TFTs) within 30 s.

Patients will receive ataluren 40 mg/kg/day in three doses: 10, 10 and 20 mg/kg, or placebo for 72 weeks. All patients will receive open-label ataluren in the 72 week extension to  compare outcomes in patients who received ataluren from baseline to week 144 (early-start ataluren) vs. those receiving ataluren from week 72 to 144 (delayed-start ataluren). Primary endpoint is slope of change from baseline to week 72 in 6MWD in patients aged ≥ 7 to ≤ 16 years with baseline 6MWD ≥ 300 m and time to stand from supine ≥ 5 s. Secondary and exploratory outcome measures include TFTs, North Star Ambulatory Assessment, muscle strength (in patients <7 years old), upper limb function (in patients ≥7 years old), health-related quality of life, as well as magnetic resonance imaging at a subset of sites. Safety parameters will be assessed throughout the study.

This study incorporates learnings from previous studies (007 and 020) as well as current EMA and FDA guidance on the use of longer trials in DMD drug development.