SEATTLE — When Paige Ellens was diagnosed with cystic fibrosis as a newborn in 1998, Seattle doctors were quick to reassure her parents that there was hope for patients with the life-threatening genetic disorder.

Even then, 17 years ago, there were inklings that research might one day produce a treatment that could target the underlying cause, not just the symptoms of the disease that causes thick, sticky mucus to build up in the lungs, making it hard to breathe.

“It was devastating, but I just remember that I was going to get to watch her grow up to be big,” recalled Paige’s mom, Sharla Ellens, 47, of Lynden. “Our surgeon assured us that we would find a cure in her lifetime.”

No one’s calling it a cure, but results of two large clinical trials co-led by a Seattle researcher find that a new drug may successfully treat the problem protein in nearly half of people with cystic fibrosis – and reduce the leading cause of death from the disease by 40 percent.

“It is a breakthrough,” said Dr. Bonnie Ramsey, a professor of pediatrics at the University of Washington School of Medicine and the Center for Clinical and Translational Research at Seattle Children’s.

“This is the beginning of effective therapy for cystic fibrosis associated with the most common mutant form of CFTR,” wrote Dr. Pamela Davis, dean of the school of medicine at Case Western University, in an editorial that accompanies the study published Sunday in the New England Journal of Medicine. The disease is caused by mutations in the gene that encodes the problem protein – the cystic fibrosis transmembrane conductance regulator, or CFTR.

Ramsey is one of four lead authors of two Phase 3 clinical trials that confirmed that Orkambi, a new drug from Vertex Pharmaceuticals, can help people age 12 and older with two copies of the most common mutation, known as F508del. Vertex helped fund the trials.

The trial results were part of the evidence that led a federal advisory committee last week to recommend approval of Orkambi by the Food and Drug Administration. In a 12-1 vote, the panel agreed that the drug was safe and effective enough to use. The FDA’s decision is expected July 5.

The trials – which studied more than 1,100 cystic fibrosis patients from six countries between April 2013 and April 2014 – showed that Orkambi helped achieve a 3 percent improvement in lung function over placebo.

“Even though it was only a 3 percent change, once that change happened, there wasn’t a dramatic bump-up, but it was absolutely rock solid for 48 weeks,” Ramsey said.

In addition, the drug reduced pulmonary exacerbations by 40 percent, dramatically cutting those sudden and life-threatening declines in lung function. Paige was hospitalized four or five times in the past three years with these debilitating episodes. But with the drug, that’s gotten much better.

“This is the healthiest I’ve ever been in my life,” said Paige.

Orkambi is intended for the 14,000 cystic fibrosis patients in the U.S. with two copies of the defective gene.