Lumacaftor (VX-809) is an investigational drug developed by the Massachusetts-based pharmaceutical company Vertex for the treatment of patients who suffer from cystic fibrosis (CF) and have the F508del mutation in the CF transmembrane conductance regulator (CFTR). Currently, lumacaftor is approved by the U.S. FDA as a combined oral treatment for CF in combination with Kalydeco (ivacaftor). Lumacaftor is commercialized by Vertex under the brand name Orkambi, and Kalydeco was approved in the United States in 2012. The lumacaftor/Kalydeco combo was approved by the FDA in July 2015 for patients ages 12 and older, while the use of lumacaftor alone is still being studied by Vertex. The mechanism of action of lumacaftor is based on the interference with the F508 CFTR. The chronic disease is caused by a mutation in the gene that controls the salt transportation in the cells, resulting in thick, sticky mucus in the respiratory, digestive, and reproductive systems. To address that genetic defect, lumacaftor helps correct the mutated genes with a novel therapeutic approach. Both lumicaftor and kalydeco work by correcting the misfolded CFTR protein, the root cause of the F508del mutation, which led to the approval of the combined treatment by the FDA. However, while kalydeco alone is also approved by the FDA, the use of lumacftor alone has not yet been approved.

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.