indication

For the treatment of cystic fibrosis (CF) in patients age 6 years and older who have a G551D mutation in the CFTR gene.

pharmacology

Ivacaftor is a cystic fibrosis transmembrane conductance regulator (CFTR). In patients with the G551D mutation, Kalydeco, a pill taken two times a day with fat-containing food, helps the protein made by the CFTR gene function better and as a result, improves lung function and other aspects of CF such as increasing weight gain.

mechanism of action

Cystic fibrosis is caused by any one of several defects in a protein, cystic fibrosis transmembrane conductance regulator, which regulates fluid flow within cells and affects the components of sweat, digestive fluids, and mucus. The defect, which is caused by a mutation in the individual's DNA, can be in any of several locations along the protein, each of which interferes with a different function of the protein. One mutation, G551D, lets the CFTR protein reach the epithelial cell surface, but doesn't let it transport chloride through the ion channel. Ivacaftor is a potentiator of the CFTR protein. The CFTR protein is a chloride channel present at the surface of epithelial cells in multiple organs. Ivacaftor facilitates increased chloride transport by potentiating the channel-open probability (or gating) of the G551D-CFTR protein.

toxicity

There have been no reports of overdose with Ivacaftor. The highest single dose used in a clinical study was 800 mg in a solution formulation without any treatment-related adverse events.

biotransformation

Ivacaftor is extensively metabolized in humans. In vitro and clinical studies indicate that ivacaftor is primarily metabolized by CYP3A. M1 and M6 are the two major metabolites of ivacaftor in humans. M1 has approximately one-sixth the potency of ivacaftor and is considered pharmacologically active. M6 has less than one-fiftieth the potency of ivacaftor and is not considered pharmacologically active.

half life

12 hours following a single dose

route of elimination

Following oral administration, the majority of ivacaftor (87.8%) is eliminated in the feces after metabolic conversion. The major metabolites M1 and M6 accounted for approximately 65% of the total dose eliminated with 22% as M1 and 43% as M6. There was negligible urinary excretion of ivacaftor as unchanged parent.