THE first new asthma treatment in decades could be on the horizon after the discovery of a protein that prevents the condition, according to experts.

The key chemical, a muscle relaxant, is missing from sufferers – triggering airway constriction, mucus, chest tightness and breathing problems.

Now scientists believe they could develop a pill or inhaler that would restore the protein, relieving symptoms for five million asthmatics in the UK and 334 million worldwide.

The SPLUNC1 protein was originally identified for its role in cystic fibrosis by Professor Robert Tarran, whose colleague Professor Steve Tilley wondered if it was involved in asthma.

They measured levels in samples from patients and healthy volunteers at an asthma centre at the University of North Carolina.

Mr Tilley said: “We were astonished to find SPLUNC1 levels were markedly reduced in people who have asthma.”

His laboratory found the protein was also depleted in asthmatic mice. Restoring it reversed airway hyper responsiveness, a cardinal feature of asthma making it difficult to breath.

Mr Tarran found SPLUNC1 could regulate contraction of the airway smooth muscle by blocking calcium, providing an explanation of how a deficiency may lead to the symptom.