PTC Therapeutics' hopes for entering the US market for treating Duchenne muscular dystrophy (DMD) were dashed—at least in the near term—when a Food and Drug Administration Advisory Committee overwhelmingly recommended against approval of its drug candidate ataluren on September 28. Ataluren targets nonsense codons (the triplet nucleotide sequences UAA, UAG or UGA) that create premature stop signals in mRNA translation, resulting in truncated proteins. These nonsense mutations can cause a variety of genetic diseases, including DMD, beta-thalassemia and cystic fibrosis. In February 2016, the FDA refused to review PTC's application for marketing approval of ataluren; the drug had failed to meet its primary endpoint in a phase 3 trial. A subsequent meta-analysis of phase 2b and phase 3 data across several endpoints, however, did show promise and gained the South Plainfield, New Jersey, biotech a conditional approval in Europe for the drug in 2016. The European regulator proposed a new three-year phase 3 study to develop further evidence regarding the drug's effectiveness. PTC also continued to petition the US regulator on the basis of the new review of its data and the promise of a new trial. Although the FDA advisors agreed that the clinical data suggested ataluren would be an effective treatment, all but one said that the post hoc nature of the evidence failed to constitute a definitive proof of efficacy. Still, patient advocates and investors in PTC are hoping that FDA will ignore the Advisory Committee's recommendation. That rarely occurs, but was the case with its review of Cambridge, Massachusetts–based Sarepta Therapeutics' DMD drug Exondys 51 (eteplirsen). After months of lobbying efforts by patients, in September 2016 Exondys gained accelerated approval in the US, against the scientific advice of FDA scientists and staff (Nat. Biotechnol. 34, 1078, 2016).