BOSTON — The approval of Vertex Pharmaceuticals Inc.’s Orkambi (lumacaftor/ivacaftor) is being hailed as a big stride forward in the treatment of cystic fibrosis.

Orkambi is the first medication to treat the underlying cause of cystic fibrosis in people ages 12 and older with two copies of the F508del mutation, the largest group of people with the disease.

The Food and Drug Administration announced its approval of the drug just before the holiday weekend. Vertex noted that the medication is the first to treat the underlying cause of cystic fibrosis in people ages 12 and older with two copies of the F508del mutation. It is only indicated for these patients, who can be identified with a genetic test.

People with two copies of the F508del mutation represent the largest group of people with cystic fibrosis (CF). Of the 30,000 people in the United States with CF, about 8,500 ages 12 and older have two copies of the F508del mutation.

Vertex said Orkambi will be available for shipment to U.S. specialty pharmacies within days.

“Today is a remarkable day for science, medicine and the CF community,” Vertex chairman, president and chief executive officer Jeffrey Leiden said in a statement. “More than 15 years ago, our scientists set out to discover and develop medicines to treat the underlying cause of cystic fibrosis. Today, the approval of Orkambi represents a fundamental change in the treatment of the most common form of CF, marking significant progress for us and for the entire CF community. While we celebrate this important step forward, we also recognize that two out of three patients in the U.S. still do not have a medicine to treat the underlying cause of their disease. We share their urgency and are committed to continuing our significant investment in research and development to discover new medicines for them and to improve upon what we offer patients today.”

A life-threatening genetic disease, CF causes serious lung infections and premature death. It affects 70,000 people worldwide. People with the disease inherit a defective gene that causes a buildup of thick mucus in the lungs, pancreas and other organs.

The Cystic Fibrosis Foundation noted that Orkambi improves lung function and significantly reduces the rate of pulmonary exacerbations, which can lead to frequent hospitalizations and accelerated lung disease. The foundation said Orkambi is the second drug approved by the FDA that targets the underlying cause of CF, with ivacaftor — as a single therapy — being the first.

Orkambi was developed by Vertex with significant clinical, scientific and funding support from the CF Foundation.

“We applaud the FDA for its swift approval of Orkambi. It is our hope that everyone who is prescribed this drug will have immediate access to it so they can begin to live longer, healthier lives,” stated Robert Beall, president and CEO of the CF Foundation. “We are proud of the important role that the foundation played in the research and development of both ivacaftor and lumacaftor, including initiating the first efforts that led to the discovery and development of these small molecules.”

The FDA said Orkambi received the agency’s breakthrough therapy designation because preliminary clinical evidence demonstrated that the drug may offer a substantial improvement over available therapies. The FDA also reviewed Orkambi under the priority review program — employed for drugs that may offer significant improvement in safety or effectiveness in treatment over available therapy in a serious disease or condition — and granted Orkambi orphan drug designation because it treats a rare disease.

“The FDA encourages manufacturers to develop new and innovative treatments for serious rare diseases like cystic fibrosis,” commented John Jenkins, director of the Office of New Drugs for the FDA’s Center for Drug Evaluation and Research. “Today’s approval significantly broadens the availability of targeted treatments for the specific defects that cause cystic fibrosis.”