SOUTH PLAINFIELD, N.J., Sept. 10 /PRNewswire/ -- PTC Therapeutics, Inc. (PTC) today announced the initiation of a Phase 3 trial of ataluren (formerly PTC124(R)), an investigational protein restoration therapy in patients with nonsense mutation cystic fibrosis (nmCF). Patients with CF lack adequate levels of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, a chloride channel necessary for normal function of the lung, pancreas, liver, and other organs. In nmCF, an interruption in the genetic code -- known as a nonsense mutation -- prematurely halts the synthesis of CFTR, causing the protein to be short and non-functioning. Nonsense mutations are categorized as Class I mutations that result in little or no production of the CFTR protein. CF patients with Class I mutations typically experience more severe disease symptoms than those with low-risk genotypes, including a greater than twofold increased risk of death,(1) a higher probability of end-stage lung disease,(2) and a higher prevalence of pancreatic insufficiency.(2) Ataluren is designed to promote restoration of the missing CFTR. Through advances in genetic analysis, a simple test can now determine if a patient’s disease is caused by a nonsense mutation.