Studies look to sea for cystic fibrosis treatment
Inhaled saline solution works where drugs failed, doctors say
By Peggy Peck
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(MedPageToday) -- Surfers chasing waves off the coast of Australia gave researchers a clue to a cheap, effective treatment for cystic fibrosis.
Two studies published Wednesday in the New England Journal of Medicine report that cystic fibrosis patients who inhaled a specially mixed saltwater solution at least twice a day had half as many hospitalizations for lung problems and significantly improved their ability to clear mucus from the lungs.
The patients in the studies also had marked improvement in lung function, said Dr. Scott Donaldson of the University of North Carolina at Chapel Hill.
Cystic fibrosis affects about 30,000 children and young adults in the United States and is the leading fatal genetic disease in whites worldwide -- it affects other races much more rarely. The disorder causes thick, sticky mucus to build up in the lungs. Lung airway surfaces in CF patients are dry, which makes the mucus both harder and stickier, Donaldson said.
Healthy people cough to clear their lungs, but for people with cystic fibrosis, coughing is not enough.
An effective treatment has long been elusive, and now it seems that one was hiding in plain sight: in the world's oceans.
"Surfers with cystic fibrosis had fewer lung exacerbations," Donaldson said.
That led him and other scientists working in North Carolina and at the Royal Prince Alfred Hospital in Sydney, Australia, to theorize that there might be something about saltwater that could explain improved lung function in the surfers.
When the patients inhaled the saltwater, it caused their lungs to "re-hydrate by adding a layer of water to the airway surface," Donaldson said. "That acts as a lubricant, which makes it easier to clear the mucus."
Donaldson and colleagues conducted a pilot study on 24 patients, and those results were shared with the Australian doctors, who tested the treatment in 164 patients for 48 weeks.
Donaldson said he was surprised by the results because he doubted that saltwater -- or more precisely a 7 percent sodium chloride solution called "hypertonic saline" -- could work by itself. So he thought another drug would be needed.
"We found exactly the opposite," Donaldson said. "The patients who received just the hypertonic saline got all the benefit, while the patients who underwent pre-treatment with amiloride (a diuretic drug used to boost the hydration effect of the saltwater) had no improvement.
"We were blown away by this finding, and it sent us scurrying back to the lab where we discovered a novel property of amiloride: It blocked water transport from the blood."
In the Australian study, patients getting the saltwater through a nebulizer had significant improvement in lung function and -- perhaps most significantly --they had 56 percent fewer lung exacerbations.
Dr. Gail Weinmann, director of the Airway Biology and Disease Program at the National Heart, Lung and Blood Institute, said the enthusiasm for the finding needs to be tempered because "more clinical trials are needed to determine how well this treatment is tolerated."
Dr. David Taylor, a professor of medicine at Louisiana State University and a pulmonologist at the Ochsner Clinic, said it might be difficult to dampen the enthusiasm once these results are widely circulated.
"It is not very often that you can find a cheap substance that offers the potential to make a difference in the outcome of a disease that begins early in life and carries a very high morbidity and mortality," said Taylor, who was not involved in the research.
He estimated that cystic fibrosis patients are hospitalized for exacerbations about once a year, "so cutting that rate in half is very, very significant."
But he predicted that translating the finding into practice might be difficult.
"Just because it is so cheap -- I can't imagine any drug company is going to get enthusiastic about producing hypertonic saline," he said.
Donaldson agreed, but said 3 percent saline and 10 percent saline solutions are already being manufactured, "and it is relatively straightforward to mix these in a 50-50 mixture to achieve very close to 7 percent."
Meanwhile, the Cystic Fibrosis Foundation is working to get a 7 percent solution made.
Another problem, Taylor said, is getting patients to inhale the way they should. He noted that in the Australian study, the rate of compliance with the treatment was 63 percent.
Donaldson said another possible barrier to compliance was that the treatment requires the saltwater be inhaled for 15 minutes at a time.
"We are working to improve delivery to perhaps three or four minutes, and ultimately less than one minute," he said.
If the saline cannot be adapted for a more patient-friendly delivery method, "we may be able to use something other than salt to achieve the same effect. For example there is now a pilot study with mannitol, which is a dry powder that has the potential for quick delivery," Donaldson said.
Both studies received funding from the Cystic Fibrosis Foundation, and the North Carolina study received additional support from the National Institutes of Health, while the study in Sydney was also funded by the Australian Cystic Fibrosis Research Trust and the National Health & Medical Research Council of Australia.
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