A "breakthrough" treatment for cystic fibrosis will not be available on the NHS after the the health watchdog rules that it is too expensive.
The drug Orkambi has been shown in clinical trials to improve lung function and respiratory symptoms in people with the genetic condition.
But the National Institute for Health and Care Excellence (Nice) said the cost is too high "for the benefits it offers".
Almost 3,000 people in the UK suffer with the condition.
What is cystic fibrosis?
Cystic fibrosis is an inherited condition in which the lungs and digestive system can become clogged with thick, sticky mucus
It can cause breathing and digestion problems from a young age
Over many years, the lungs become increasingly damaged and may eventually stop working
One in every 2,500 babies born in the UK has cystic fibrosis
Symptoms can include: recurring chest infections; difficulty putting on weight; frequent, wet-sounding coughs; diarrhoea; occasional wheezing and shortness of breath
Only around half of people with cystic fibrosis live to celebrate their 40th birthday
The charity the Cystic Fibrosis Trust said that since Nice undertook its appraisal, new data had been published that suggested Orkambi almost halved the rate of decline in lung function in people with the disease over a two-year period, potentially adding years to life.
The drug, which is approved in the US, Germany and France, is for people with the F508del mutation, which causes the production of an abnormal protein that disrupts how water and chloride are transported in the body.
Having two copies of this mutation (one inherited from each parent) is the leading cause of cystic fibrosis.
Ed Owen, chief executive of the Cystic Fibrosis Trust, said:
We are very disappointed by this decision. It demonstrates the weakness of the current system, and Nice has been unable to confidently predict the long-term benefits of the drug.
Simon Bedson, senior vice president at Vertex, which makes the drug, said it was now in talks with the Department of Health to agree a price that might make the drug accessible.
Orkambi costs £104,000 per patient for every year of treatment.
As we've said for many months, the single technology appraisal process (used by Nice) is not appropriate for assessing medicines, such as Orkambi, for rare diseases like cystic fibrosis.
Professor Carole Longson, Director of the Nice Centre for Health Technology Evaluation, said:
We know how important a new treatment option would be for people with cystic fibrosis; but for the benefits it offers, the cost of Orkambi is too high.