When Gunnar Esiason’s health rapidly deteriorated in 2013, he was in and out of the hospital for two years.

Infections associated with cystic fibrosis started to “take over” his lungs.

“I underwent close to two dozen medical procedures just to keep my head above the water,” said the 28-year-old, who was diagnosed with the genetic disorder at the age of two.

But last year, when he enrolled in a clinical trial for a new drug developed by Vertex Pharmaceuticals called Trikafta, his condition improved more rapidly than it had deteriorated.

“It felt like my future was unlocked,” he told CTV’s Your Morning on Tuesday from Hanover, New Hampshire. He started to gain weight. The mucus buildup in his lungs began to feel different and he stopped coughing.

“Which is quite an amazing thing when you’re dealing with a respiratory illness,” he said. “Everything changed almost overnight.”

The new drug was approved last week by the U.S. Food and Drug Administration for patients, 12 and up, with specific gene mutations. That accounts for roughly 90 per cent of the CF population, the agency said. The list price for Americans is more than US$311,000 annually. Though it’s not yet available in Canada, there’s a “palpable” excitement among more than 4,000 Canadians living with the disorder, said John Wallenburg, chief scientific officer with Cystic Fibrosis Canada.

Esiason himself has dubbed the drug a “miracle.”

“It’s huge. It’s absolutely huge for this community,” said Wallenburg Tuesday on CTV’s Your Morning. “In terms of progress, scientifically and medically, this is fantastic.”

In the clinical trials, which performed short-term tests on people with lung capacity between 40 and 90 per cent, the average improvement in lung function was 14 per cent. CF patients typically lose lung function at a rate of 2 per cent a year.

“That’s a massive difference,” he said. “It’s a drug that affects different people differently. There are some people who had much greater improvements as well.”

CF results from a defect of a protein called the cystic fibrosis transmembrane conductance regulator, or simply CFTR, that causes a buildup of mucus affecting organs, including the digestive and respiratory systems. The new development is the third generation of a class of drugs known as “CFTR modulators,” which take aim at the protein flaw.

“It goes in and it fixes that defective protein rather than just treating the symptoms, which is what we’ve done largely so far,” said Wallenburg.

But for many Canadian scientists, the new drug is being met with mixed feelings. “We’ve seen this day coming for a long time,” said Wallenburg. “It’s a challenge in Canada. This is the third generation of this type of drug. We’ve skipped right over -- we haven’t even gotten the second generation.”

When and where a drug is submitted for approval is at the developer’s discretion. The decision can be informed by a variety of factors. The U.S. is the biggest market for the drug, and also the market that pays the most, said Wallenburg. Canada is traditionally considered “top tier,” which should help propel the drug’s approval.

“We’ve usually been pretty rapid in terms of at least seeing a company submit something for regulatory approval,” he said, though it’s uncertain when this could happen in Canada.

For CF patients like 28-year-old Esiason, the new drug means thinking about life long-term. The median age of survival for a Canadian born with CF is just 52, according to Cystic Fibrosis Canada.

When you’re living with a terminal illness, you kind of live day to day,” said Esiason. “As soon as my health turned around, it was like, ‘OK, what am I going to do next? I’m really looking forward to the rest of my life because of this amazing breakthrough.”