The findings stem from the realisation that not all asthma or COPD attacks are the same. Instead, different parts of the immune system are over-reacting in different patients.

“Now we can see there are different patterns of inflammation, we can be smarter and get the right treatment, to the right patient, at the right time,” said Prof Mona Bafadhel, from King’s.

Benralizumab targets a type of white blood cell – called an eosinophil – that can cause inflammation and damage in the lungs.

Eosinophils are implicated in about half of asthma attacks and a third of COPD flare-ups.

If such an attack – involving difficulty breathing, wheezing, coughing and chest tightness – cannot be controlled with regular inhalers then doctors currently prescribe a course of steroids.

The study, on 158 people, monitored patients for three months after treatment for a flare-up.

The results in The Lancet Respiratory Medicine found a treatment failure rate of:

People treated with the new therapy were less likely to be admitted to hospital, need another round of treatment or die.

Prof Bafadhel said this could benefit a huge number of people as two million attacks a year “is not a small number”.

“This is a game-changer, we’ve not had a change in treatment for 50 years – it will revolutionise how we treat people when they’re really unwell,” Prof Bafadhel said.

Volunteers also reported improved symptoms and a better quality of life on the new drug.