Genetic testing could lead to tailored asthma treatment

Scientists from Dundee University claim that a relatively simple and inexpensive ‘spit test’ could pave the way for creating bespoke asthma treatment for children suffering with the lung condition if a specific genetic mutation is detected and thus practically rendering their current treatment almost useless.

The Dundee University scientists collaborated with colleagues at Brighton University to analyse a total of 62 children who all had poorly controlled asthma and in many cases it was determined that their prescribed medication could be the source of the problem.

In particularly, a common culprit could be the inhaled ‘salmeterol’, found in both seretide and servent inhalers. Salmeterol is used by children with severe asthma that cannot be controlled with just their inhaled steroid medication such as the blue inhaler Ventolin – a popular inhaler prescribed to all children after they are formally diagnosed as having asthma.

The scientists believe that genetic code is the reason why some children fail to respond to the salmeterol. The drug is known as a ‘bronchodilator’ beta-2 agonist meaning it acts at stimulating beta-2 receptors on the muscle cells that line the airways. This results in these muscle cells being able to relax and open the airways.

Unfortunately however, an estimated one in seven people have a genetic mutation – the arginine-16 genotype of the beta-2 receptor- that causes their receptors to have a slightly altered shape than normal and the salmeterol does not acknowledge this difference.

All 62 children involved in the study had this genetic mutation and all had required periods of time off school, had hospital treatment or had visited a GP out of hours due to their asthma flaring up. During the study, the authors allowed the children to use their basic inhaler to control symptoms. In addition though, half were chosen at random to receive salmeterol and the other half were administered the anti-inflammatory medicine montelukast, used to prevent children from experiencing an asthma attack.

Within just three months it was discovered that those taking montelukast had significantly less coughing and wheezing, less likely to experience any deterioration of their asthma symptoms, as well as more likely to use their reliever inhaler less frequently than before.

At the beginning of the study, researchers calculated that 36% of the children had to use their reliever inhaler on a daily basis. After the year-long study had come to a conclusion, the total number of children using this inhaler every day had been slashed by half in the montelukast group. Interestingly, this trend was not seen within the salmeterol group.

Professor Somnath Mukhopadhyay said: “For almost every clinical outcome we were looking at we found that salmeterol either wasn’t working or was working very poorly. Montelukast was very much better. We’ve shown for the first time that personalised medicine can work in the field of childhood asthma.”

Prof Mukhopadhyay says the simple test would cost around £15 if it were to ever be introduced into GP surgeries, adding that it is unacceptable to prescribe drugs to children that are ineffective. He continued: “It’s a common disease affecting a million children in this country.  A common medicine is probably not working in a significant proportion of the population. I think we need to get some guidance from lead charities and from the Department of Health.”

Professor Stephen Holgate, MRC clinical professor of immunopharmacology at Southampton University, commented on the results of the study and said: “While genetic changes that determine bronchodilator responses in asthma have been known for some time, this is a wonderful example of stratified or personalised medicine working its way into practice. While still a small trial, the results in the asthmatic children’s response to the two treatments across a number of asthma outcomes are impressive.”