Post-transcriptional control mechanisms are all the regulatory events that take place after a messenger RNA (mRNA) molecule is copied from DNA (i.e., after the transcription process). These mechanisms include the decoding of the mRNA molecule so that a protein is synthesized, the determination of how efficiently an mRNA is utilized to make protein, and how long an mRNA lasts in a cell. All of these regulatory effects have a direct impact on how much protein is produced from each mRNA. Precise control of mRNA utilization is critical for many important functions, including the cell division cycle, the immune response, and the growth and repair of tissues.

Small molecules that target post-transcriptional control to either up- or down-regulate protein production may have the potential to treat a wide variety of diseases, including muscular dystrophy, that result from the body's production of too much or too little of a particular protein. Such compounds can effectively regulate protein levels, either by inducing or enhancing the production of a needed protein or by blocking the production of an undesirable protein.

PTC Therapeutics’ lead compound, ataluren (PTC-124), is an orally available drug for the treatment of genetic defects resulting from nonsense mutations. Ataluren allows the cellular machinery to bypass the nonsense mutation and continue the translation process, restoring the production of full-length, functional protein.

The investigational new drug is in phase III for the treatment of cystic fibrosis (CF); it is also undergoing phase II/III clinical evaluation for the treatment of Becker's muscular dystrophy and for the treatment of Duchenne's muscular dystrophy in patients with nonsense-mutation-mediated disease. Additional phase II clinical trials are evaluating ataluren for the treatment of nonsense-mutation-mediated hemophilia A and B. In 2005 and 2006, ataluren was granted fast-track designation from the FDA for the treatment of CF and Duchenne's muscular dystrophy in patients with nonsense-mutation-mediated disease, respectively. The drug holds orphan drug designation in the U.S. and E.U. for the treatment of CF due to a nonsense mutation in the cystic fibrosis transmembrane regulator (CFTR) gene and for the treatment of Duchenne's muscular dystrophy.