Asthma: much more than one disease
and childhood forms of asthma suggests that pharmaceutical
companies may have to rethink their approach to developing new
drugs for the disease.
The finding ties in with a growing body of research indicating that asthma is a collection of a number of discrete syndromes joined together by their common symptoms of breathing difficulties and inflammation in the lung.
This means that the drug industry's historical approach to asthma - trying to develop drugs for all patients - is flawed. The increased complexities of the disease process means that different targets could emerge that are appropriate for different patient groups.
The study, published in the Journal of Allergy and Clinical Immunology (January 2004 issue) examined the characteristics of asthma depending on the age at which symptoms first developed.
80 patients were separated into two groups, those with severe symptoms who developed the disease before they were 12 years old, and those who developed it after this age, who tended to have milder symptoms.
Compared to the late-stage asthma patients, the younger group tended to be more allergic when tested using a standard skin prick test, and also had more allergy-like symptoms - such as wheezing.
Meanwhile, the older group showed signs of faster lung deterioration and demonstrated higher levels of eosinophils (inflammatory cells) in the lungs. The report suggests that, as well as onset age, the level of eosinophils in the lung distinguishes the type of asthma from which a patient suffers.
It has been estimated that there are 30-50 genes involved in asthma, which is a further indication of the heterogenous nature of the disease.
For pharmaceutical companies, the findings pose something of a problem. Focusing a lot of resources on a specific pathway could lead to a highly-effective treatment with a lower risk of side effects, but which is active only in a small proportion of patients, making it harder to recoup their R&D investment.
This may be easier if a high price could be charged for the medication, but as asthma is controllable in many cases with existing drugs such as bronchodilators or steroids, health care payers may balk at footing the bill.
However, with 150 million patients with the disease worldwide and 40 million in the US, a drug that worked in just a quarter of patients would still be a sizeable product opportunity.
The challenge for pharmaceutical researchers will be to identify areas of crossover between the different disease types that will broaden the patient population.
