UK and Canadian scientists have found that an injection of mepolizumab helped patients whose asthma is made worse by eosinophilia. This is a condition - marked by a particular type of white blood cell - that is linked to severe allergies.
The drug not only reduced the frequency of severe attacks, but enabled patients to cut back on the use of steroids, which are associated with side effects.
The study was published in the New England Journal of Medicine.
The Canadian study focused on 20 patients who had been taking the steroid prednisone - which is linked to side effects such as weight gain and bone loss - for an average of nine years to control their condition.
Those who were given mepolizumab were able to reduce their use of prednisone significantly without their asthma getting any worse.
In contrast, symptoms deteriorated in patients who were given a dummy drug instead of mepolizumab as they cut back on prednisone.
Analysis showed that mepolizumab reduced the number of eosinophils to the normal range - and kept them there.
The UK study of 61 patients, led by Professor Ian Pavord at the Institute for Lung Health, produced similar results. In this case patients continued to take steroids alongside mepolizumab.
Authors stress that this type of therapy would not benefit all asthma patients.
