Cystic fibrosis drug gets FDA approval

By Dr. Ananya Mandal, MDFeb 1 2012

A drug – the first of its kind - that treats the root cause of cystic fibrosis won approval Tuesday. This could be a ray of hope for patients with the deadly illness and broader hope for thousands more patients with the inherited disease.

About 30,000 Americans live with cystic fibrosis, a disease that causes sticky mucus buildup in the lungs and other organs, leading to infections, digestive problems and death in young adulthood. The typical life expectancy is about 37 years, according to the Cystic Fibrosis Foundation.

Now the Food and Drug Administration has approved Vertex Pharmaceuticals Inc.'s Kalydeco for patients with a rare form of the disease that affects just 1,200 people in the U.S., about 4 percent of affected population nationwide. These patients have a protein defect that prevents their cells from properly absorbing and excreting salt and water. Studies of the drug showed it significantly improved lung function and reduced other symptoms of cystic fibrosis. The FDA approved the drug in approximately three months, half the time usually needed for high-priority drugs.

The mutation, called G551D, is in a gene called the cystic fibrosis transmembrane conductance regulator. The CFTR gene regulates the transport of chloride and water in the body. Kalydeco helps the protein made by the CFTR gene function better, which improves lung function and improves other side effects of cystic fibrosis.

“Even though this drug isn't for the majority of people, it proves that you can look at the mistake in the genes and design a drug in a rational way that will fix the problem,” said Dr. Drucy Borowitz of the State University of New York at Buffalo, where she directs the cystic fibrosis program.

The pill is to be taken twice a day. It is one of the first drugs designed to a correct a specific genetic defect. Its development characterizes both the promise and challenges of that approach. Scientists first identified the gene that causes cystic fibrosis in 1989, but it took more than two decades and more than $75 million in outside funding to develop a drug to treat the disease.

Borowitz enrolled several of her patients in the key study for Kalydeco, which showed that patients taking the drug increased their lung strength more than 10 percent when compared with patients taking a placebo. Patients also had fewer infections and gained nearly seven pounds on average, a significant amount for patients who typically have trouble retaining weight. All patients in the study continued taking older medications that help loosen mucus.

Only a few decades ago, children with cystic fibrosis seldom survived elementary school. Today, thanks to earlier diagnosis and new focus on diet and physical therapy, 47 percent live to be 18 or older.

The FDA approved the drug for patients 6 years old and up, though Vertex is also planning to study the drug in patients as young as 2 years old. Researchers hope that by using the drug earlier they will be able to prevent permanent lung damage, which is the primary cause of death for cystic fibrosis patients.

Vertex executives said Kalydeco would cost $294,000 for a year's supply, placing it among the most expensive prescription drugs sold in the U.S. Specialty drug makers are known to charge $300,000 or more for drugs that treat very small groups of patients. “The drug is priced for the value it will deliver to this very small group of patients,” Vertex Executive Vice President Nancy Wysenski told analysts. Wysenski said Vertex would provide the medicine for free to people with no insurance and household income of $150,000 or less. The company will also cover 30 percent of co pay costs for select patients who have insurance.

The most common side effects with Kalydeco include headache, stomach ache, rash diarrhea and dizziness.