Ivacaftor (trade names KALYDECO® (ivacaftor) and ORKAMBI® (lumacaftor/ivacaftor)) is a cystic fibrosis transmembrane conductance regulator potentiator indicated for the treatment of cystic fibrosis in patients age 6 years and older who have one of the following mutations in the CFTR gene: G551D, G1244E, G1349D, G178R, G551S, S1251N, S1255P, S549N, or S549R. One such defect G551D is characterized by a dysfunctional CFTR protein on the cell surface. Although the defective protein is trafficked to the correct area, the epithelial cell surface, while there it cannot transport chloride through the channel. Ivacaftor, a CFTR potentiator, improves the transport of chloride through the ion channel by binding to the channels directly to induce a non-conventional mode of gating which in turn increases the probability that the channel is open. Ivacaftor regulates fluid flow within cells and affects the components of sweat, digestive fluids, and mucus.

CTP-656 is a deuterium-modified form of ivacaftor, an FDA-approved drug for the treatment of cystic fibrosis. CTP-656 is jointly developed by Concert Pharmaceuticals and Vertex Pharmaceuticals, and is believed to have higher metabolic stability, lower toxic byproducts and increased half-life compared to the original. CTP-656 acts as a potentiator of is a cystic fibrosis transmembrane conductance regulator (CFTR) protein. CTP-656 is investigated in phase 2 clinical trials for the treatment of cystic fibrosis.