Blocking a powerful immune system chemical could provide a new treatment for patients suffering from severe Asthma, scientists said on Thursday.

Asthma affects about 150 million people worldwide. About 10 percent of sufferers have a severe form of the illness.

Professor Stephen Holgate, of Southampton General Hospital in southern England, and his team said patients with severe asthma had higher levels of a chemical called tumour necrosis factor alpha (TNF-alpha) than other sufferers.

In a study of about 150 people, the researchers found that blocking the production of TNF-alpha with a drug produced a significant improvement in symptoms and lung function.

“Our study provides further evidence for a role for TNF-alpha in severe Asthma and is the first study to evaluate the effects of TNF blockade in patients with severe asthma,” Holgate wrote in a study reported in the journal Thorax.

The researchers injected the drug etanercept, which is made by Amgen under the brand name Enbrel, under the patients’ skin twice a week for 12 weeks. Amgen markets Enbrel, which works in a range of autoimmune diseases, along with Wyeth.

The treatment curbed the inflammatory reaction in the lungs and patients reported few side effects, according to the researchers.

TFN alpha promotes inflammation. It is found in several inflammatory disorders such as rheumatoid arthritis, Crohn’s disease and psoriasis.

Asthma affects the airways - small tubes that carry air in and out of the lungs. It occurs when the tubes swell up and spasm, blocking the free passage of air in and out of the lungs.

People with the illness suffer from coughs, wheezing and shortness of breath. A very severe attack may kill.

Colds, the flu, cigarette smoke, pollen, stress and pollution can trigger an Asthma attack. There is no cure for asthma but it can be controlled with drugs.

Although more research and larger studies are needed, the scientists said the drug could offer a potential new avenue of treatment for patients with severe asthma.