Asthma and allergic conditions like rhinitis affect more than 100 million people around the world. In the UK alone, 5.2 million adults and 1.1 million children are receiving allergy treatment, creating a significant burden on the NHS, to say nothing of the personal suffering involved. Yet there have been no new allergy drugs for 20 years.
But there is hope on the horizon. Researchers at The University of Manchester and St George's, University of London, are developing novel allergy drugs called Allergen Delivery Inhibitors (ADIs). They block the action of allergens before they can cause any damage to the respiratory system. In 2009, the team was awarded a £4.3 million award for their work on ADIs by The Wellcome Trust, the world's largest medical research charity and they have now received a further £390,000 from Wellcome to progress the work.
Professor David Garrod, of the faculty of Life Sciences at The University of Manchester, explains that they found that disease-causing compounds (allergens) from house dust mites cause damage to the lining of the respiratory tract, allowing them to enter the body and trigger the allergy symptoms. This is because allergens are actually so-called proteolytic enzymes that can degrade the seals between the cells lining the nose and lungs. "It was a logical step to realise that if drugs that inhibit these enzymes could be developed, they would have the potential to both alleviate and prevent the disease."
At present, the researchers are studying the properties of compounds that have high potency in blocking HDM enzymes. The work is a successful collaboration between an industrial chemistry company called Domainex, based in London, who produce the compounds and Professor Clive Robertson's team at St George's, and the Manchester-based team, who are testing them. It is too soon to say whether there is an ADI for each different allergen but Prof. Garrod says, "There are reasons to believe that ADIs for house dust mite may be more widely beneficial. On the other hand, we have preliminary evidence that allergens such as pollen and Aspergillus may operate through their own proteolytic enzymes. In the long term, it may be beneficial to develop ADIs specific for these." He adds that they have sought funding to characterise pollen enzymes, but so far without success, which is a pity as millions worldwide suffer from hay fever or pollen allergy.
I asked Prof. Garrod how widely applicable ADIs will be and when they'll be available. "We think ADIs will be applicable to all patients suffering from house dust mite allergy, the main one of the allergic asthma causes," he said. "We hope that simple puffs from an inhaler will alleviate symptoms for all and prevent the mild disease from developing into severe disease." But there is a long road ahead. It is hoped that the ADIs currently being investigated will prove suitable for human clinical trials and if these prove successful the new allergy drugs will reach the market, although that will be several years from now.
It also occurred to me that we don't hear many hopeful stories of this kind of new allergy drugs, but we do hear a great deal about cancer research. Prof. Garrod commented, "There is never enough money for research in any area. If you wish to make a comparison between cancer and asthma and allergy, it is estimated that there are 7.9 million deaths worldwide per year from cancer and 250,000 from asthma. Nevertheless, asthma is a serious disease, which affects over 300 million people globally, including many children. In its moderate and severe forms, it has a serious effect on lifestyle with patients suffering from coughing, wheezing, shortness of breath and tightness in the chest - and it can be fatal. It places an enormous burden on health services. Current treatments alleviate symptoms but do not prevent or cure the disease. There is thus a major unmet clinical need in the area of asthma and allergy and, in my view, there is unquestionably a need for new drugs."