PTC Therapeutics, Inc. (PTC) initiated a Phase III trial of ataluren, an investigational protein restoration therapy for patients with nonsense mutation cystic fibrosis (nmCF). Ataluren is the first investigational drug designed to address the underlying cause of nonsense mutation cystic fibrosis. The primary objective of the registration-directed double-blind, placebo-controlled study is to evaluate whether ataluren can improve lung function, as measured by forced expiratory volume in one second (FEV1), in patients with nmCF. An orally administered therapy, ataluren is the first investigational new drug designed to enable the formation of a functioning protein in patients with genetic disorders due to a nonsense mutation. Restoring functional CFTR protein may enable ataluren to address the underlying cause of nmCF and change the course of the disease. Currently available therapies for CF focus on the alleviation of symptoms.