Progress Toward the Synthesis of Labeled Derivatives of the Cystic Fibrosis Drug Ivacaftor

Cystic fibrosis (CF) is one of the most common genetic diseases, affecting approximately 70,000 people worldwide causing severe complications and often leading to early death. CF is caused by a mutation in the gene encoding for the cystic fibrosis transmembrane conductance regulator (CFTR) protein which is responsible for fluid and ion transport through epithelial membranes maintaining the formation of a thin slippery mucous layer. CFTR mutations either lead to a trafficking defect where the CFTR protein does not reach the plasma membrane or a gating defect where CFTR protein at the plasma membrane does not function properly. Treatment of cystic fibrosis usually addresses the symptoms to overcome the complications of the disease such as pneumonia, lung infections, pancreatitis, maldigestion and infertility. Vertex pharmaceuticals has been interested in developing small molecules that have the ability to interact with mutated CFTR proteins, aiding in their delivery to the cell membrane and/or restoring their channel function. VX-770 is an orally bioavailable potentiator that has the ability to improve the gating activity and increasing the open probability of CFTR protein in patients carrying the G551D mutation. VX770, Ivacaftor, was recently approved by the US FDA after showing very good improvements in the lung function in CF patients with good safety profile. Our research is focusing on the synthesis of VX770 under mild conditions and formation of labeled derivatives to help in the understanding of its exact mode of action. Different methods were developed toward the synthesis of the two main components, LHS and RHS, of VX770 by using less harsh conditions for a short period of time. We were successfully able to make two photoaffinity labeled derivatives, aryl azide and benzophenone derivatives, which will be beneficial in tracking the drug molecule and revealing the exact site of interaction between the drug and the protein. Synthesis of VX770 fragments was is another focus of interest in our research as they will provide us with information about the best positions for further derivatization.