PTC shares slide on paper questioning ataluren's mechanism

Shares of PTC Therapeutics Inc. (NASDAQ:PTCT) slid $1.50 to $16.04 on Wednesday after researchers at the University of Dundee published preclinical data in PLoS Biology questioning the mechanism of action of PTC's ataluren, which is in Phase III testing to treat nonsense mutation genetic disorders. PTC has described ataluren as a "read-through" agent, or a small molecule that facilitates complete translation of proteins containing nonsense mutations. In several in vitro read-through assays, the researchers compared the efficacy of ataluren with geneticin, an aminoglycoside antibiotic previously shown to have read-through activity, in cells transfected with a reporter gene containing a nonsense mutation. The data showed geneticin had varying activity in every assay, while ataluren had no evidence of activity.

PTC said results of preclinical proof-of-concept (POC) and larger clinical trials are consistent with ataluren-mediated read-through having clinical activity, and that numerous independent laboratories have provided confirmation of the results. ...