The Food and Drug Administration on Jan. 31 approved the drug ivacaftor (Kalydeco) for cystic fibrosis patients aged 6 years and older who have the G551D mutation.

According to ivacaftor maker Vertex Pharmaceuticals, the approval is one of the fastest ever at the FDA. It took only 3 months from submission of data to approval.

Ivacaftor targets the G551D mutation in the cystic fibrosis transmembrane regulator (CFTR) gene. CFTR proteins regulate the flow of salt and water across the cells. A defective CFTR protein causes thick, sticky mucus to build up in the lungs, digestive tract, and other parts of the body, which can lead to respiratory and digestive problems and other complications.

The Vertex drug, taken orally twice a day, is a CFTR potentiator. It targets abnormal CFTR protein channels and opens them to allow chloride ions to move into and out of the cell; that, in turn, thins the mucus and the airways become less clogged, according to Vertex.

The FDA said that about 1,200 people – 4% of the 30,000 with cystic fibrosis in the United States – have the G551D mutation. Ivacaftor can help only those with the mutation. The agency and Vertex recommend FDA-approved molecular diagnostic testing before starting the therapy.

"Kalydeco is an excellent example of the promise of personalized medicine – targeted drugs that treat patients with a specific genetic makeup," said Dr. Margaret A. Hamburg, FDA commissioner, in a statement.

Added Dr. Janet Woodcock, director of the FDA’s Center for Drug Evaluation and Research, "Kalydeco is the first available treatment that targets the defective CFTR protein, which is the underlying cause of cystic fibrosis. This is a breakthrough therapy for the cystic fibrosis community because current therapies only treat the symptoms of this genetic disease."

The FDA’s approval was based on two 48-week, placebo-controlled clinical studies that enrolled 213 patients. One study was in patients aged 12 years and older, and the other was in patients aged 6-11 years.

They all had at least one copy of the G551D mutation. The ivacaftor-treated groups had significant and sustained improvements in lung function, as well as in weight gain and some quality of life measurements, compared with those who received placebo, according to Vertex. They also had fewer pulmonary exacerbations.

The most common side effects were upper respiratory tract infection, headache, stomach ache, rash, diarrhea, and dizziness.

Vertex said it would begin shipping ivacaftor to U.S. pharmacies this week.