Study of Ataluren (PTC124) in Nonambulatory Participants With Nonsense-Mutation-Mediated Duchenne/Becker Muscular Dystrophy (nmDMD/BMD)

Duchenne/Becker muscular dystrophy (DMD/BMD) is a genetic disorder that develops in boys. It is caused by a mutation in the gene for dystrophin, a protein that is important for maintaining normal muscle structure and function. Loss of dystrophin causes muscle fragility that leads to weakness and loss of walking ability during childhood and teenage years. A specific type of mutation, called a nonsense (premature stop codon) mutation is the cause of DMD/BMD in approximately 10-15% of boys with the disease. Ataluren (PTC124) is an orally delivered, investigational drug that has the potential to overcome the effects of the nonsense mutation. This study is a Phase 2a trial that enrolled boys with nonsense mutation DMD/BMD who have lost independent mobility due to the disease. This study evaluated the safety and tolerability of ataluren (PTC124) and also evaluated efficacy outcomes in this participant population.

It was planned that this Phase 2a, open-label, safety and efficacy study to be performed at 5 sites in the US and 1 site in the United Kingdom. The study was to enroll \~30 boys with nonsense mutation DMD/BMD (nmDBMD) who have been nonambulatory for at least 1 year. Enrollment was to be stratified to ensure evaluation of \~15 participants who were receiving chronic corticosteroid therapy and of \~15 participants who were not receiving chronic corticosteroid therapy. Participants were to take ataluren 3 times per day (at breakfast, lunch, and dinner) for 48 weeks (\~1 year). Study assessments were to be performed at clinic visits during screening, every 6 weeks for 2 visits and then every 12 weeks until the end of the study. Additional safety laboratory testing was to be required 4 times during the course of the study; this could have been performed at the investigational site, at an accredited local laboratory or clinic, or in the participant's home using a nursing service. When the blind for a similar study (PTC124-GD-007-DMD; NCT00592553) was revealed, the results indicated lack of efficacy for the high dose. Therefore, even though an independent data monitoring committee (DMC) agreed that both ataluren dose levels were well tolerated by the participants, the DMC recommended discontinuing ongoing studies with participants with nmDBMD receiving high-dose ataluren.