13 December 2016 - In September 2016, the US FDA approved eteplirsen (Exondys 51), a new drug for Duchenne muscular dystrophy, overruling the recommendations of both its scientific staff and its external advisory committee. 

The development of eteplirsen was controversial, starting with its manufacturer-supported pivotal double-blind study, which involved only 12 patients: 8 were randomised to 2 different eteplirsen doses and 4 were randomised to placebo for 24 weeks. The latter were then switched to eteplirsen and all were to be followed for an additional 24 weeks. 

The sample size was substantially smaller than the study sample size in which a similar drug, drisapersen, had been tested in 3 randomised trials that together enrolled 290 patients. The FDA declined to approve drisapersen in 2015 after these studies showed no clear benefit after 24 weeks in pre-specified clinical end points, such as changes in a 6-minute walk test. Those trials also suggested the possibility of safety problems, including renal toxic effects and thrombocytopenia.

Read JAMA Viewpoint article