The finding offers hope to hundreds of thousands of patients who suffer from the most severe form of the debilitating lung disease.
Trials on nearly 1,000 people with uncontrolled asthma showed the drug 'tiotropium' taken through a mist inhaler opened constricted airways and appeared to improve lung function, the 'Daily Mail' reported.
Even those with severe asthma saw the number of attacks cut by 21 per cent and the time between attacks extended by a third.
The drug, already licensed for chronic obstructive pulmonary disease, which usually affects smokers, could be available on the National Health Service (NHS) in UK in few years.
Five million Britons suffer from asthma, with 250,000 diagnosed with a severe form. On average, three patients die each day during an attack.
The disease is usually treated with a steroid inhaler or tablets, which can have serious side effects including skin thinning, weight gain and osteoporosis.
"People with asthma are anxious about what steroids are doing to them, particularly if they have to take them long term. Having another tool will be useful," Neil Churchill, of charity Asthma UK, said.
Researcher Richard Russell, lung specialist at Wexham Park Hospital in Berkshire, said the drug could be a "new weapon in our armoury".
