Thick mucus blocks the lungs
An experimental drug is proving effective for treating the genetic disease cystic fibrosis (CF).
CF produces thick, sticky mucus that clogs the lungs and the pancreas, leading to life-threatening chest infections and problems with digestion.
Existing treatments only ease symptoms, but the new drug, VX-770 restores function to defective proteins which cause the disease.
The early trial results were presented at the BA Festival of Science.
One in 25 people in the UK is a carrier for a defective CF gene which disables or destroys a protein known as CFTR.
Although carriers do not develop CF, they run the risk of passing the gene on to their children. Around 8,000 people in the UK have CF.
Defects in the CFTR protein affect the transport of chloride and other ions across cells.
VX-770 is designed to increase the probability that the CFTR channel is open, thereby increasing chloride transport across the cell surface.
So far it has been tested in CF patients with a genetic defect known as G551D.
Further clinical trials are necessary to learn more about the total number of patients who might benefit from the drug.
One of the most recognisable symptoms of CF is salty sweat, caused by the failure of the sweat ducts to reabsorb sweat.
Patients who received 150mg twice a day saw the concentration of salt in their sweat decrease by almost 50% and lung function improve by 10%.
Lead researcher Dr David Sheppard from the University of Bristol said: "The early results with VX-770 suggest that drug therapies which target defects at the root of the disease have the potential to improve greatly the quality of life of CF patients."
Researchers are testing other compounds that work in a similar way.
Rosie Barnes, chief executive of the Cystic Fibrosis Trust said: "The development of VX-770 is very encouraging for people with CF with a specific mutation of the CF gene - about 6% of those with CF in the UK.
"The CF Trust warmly welcomes any advances in the understanding and treatment of this terrible disease."