The US FDA has approved the orphan drug ivacaftor (Kalydeco®) for the treatment of cystic fibrosis (CF) in patients aged ≥6 years who have at least one copy of the G551D mutation in the Cystic Fibrosis Transmembrane Regulator (CFTR) gene.

CF is caused by mutations in the CFTR gene and it is estimated that around 4% of patients with CF have the G551D mutation.  Ivacaftor is an oral medicine known as a CFTR potentiator, which helps the CFTR protein function more normally once it reaches the cell surface.  It targets the abnormal CFTR protein channels and opens them to allow chloride ions to move into and out of the cell. 

The approval was based on the results of two Phase III studies (total n=213) which found that treatment with ivacaftor resulted in significant and sustained improvement in lung function as well as other disease measures, including weight gain and certain quality of life measurements, compared to those who received placebo.  The FDA report notes that this treatment is the first to tackle the underlying cause of CF, and is a breakthrough treatment for the CF community.

Because ivacaftor targets a specific genetic mutation, a person’s genotype should be known before it is prescribed (FDA-cleared tests are available for people with CF whose genotype is unknown).