Asthma, what is it and how do we treat it?
Today, 2nd May 2017, is World Asthma Day, a day dedicated to asthma prevention, diagnosis and treatment.
What is asthma?
Asthma is a heterogeneous disease characterised by chronic airway inflammation and variable airway obstruction that is reversible, either spontaneously or after treatment. It affects people of all ages and often starts in childhood, although it can also appear for the first time in adults. The disease is long-term or chronic and the prevalence in different countries varies widely, but the disparity is narrowing due to rising prevalence in low and middle income countries and plateauing in high- income countries.
An estimated 300 million people worldwide suffer from asthma, with 250,000 annual deaths attributed to the disease. It is estimated that the number of people with asthma will grow by more than 100 million by 2025. Approximately 250,000 people die prematurely each year from asthma. Almost all of these deaths are avoidable.
There’s currently no cure for asthma, but there are simple treatments that can help keep the symptoms under control so it doesn’t have a significant impact on the patient´s life. Some people, particularly children, may eventually grow out of asthma, but for many it is a lifelong condition.
Treatment with inhaled corticosteroids is the dominating anti-inflammatory treatment during asthma and is recommended at all stages of the disease, except for the mildest. The inhaled corticosteroids can be combined with long-acting beta-2 agonists, these are symptom-controllers that are helpful in opening the airways. (Reference: http://www.aaaai.org/conditions-and-treatments/asthma)
In addition, leukotriene modifiers can further relieve symptoms for some patients, as leukotrienes are important mediators in asthma. Produced by eosinophils, mast cells and macrophages they contribute to chronic inflammation during asthma.
New drug treatments
In addition to traditional treatments, new drugs are being developed to relieve the different symptoms of asthma. One of them, anti-IL-5 (Mepolizumab) has recently been approved both in Sweden and the UK.
This drug is used to help patients with severe, difficult to treat asthma. Approximately five per cent of asthma patients fall within this category, but since asthma is such a prevalent disease, this proportion adds up to quite a few people.
Mepolizumab targets severe eosinophilic asthma – where the inflammation of the airways is linked to a particular type of white blood cell (eosinophils). It is a humanised monoclonal antibody that binds to interleukin-5 (IL-5) and hinders IL-5 from binding to its receptor on eosinophils, leading to a decrease of eosinophils in blood, tissue and sputum. It is believed that around 40% of people with severe asthma will have an eosinophilic phenotype – meaning that they may be able to benefit from the new treatment.
Mepolizumab is administered through sub-cutaneous injection every two to four weeks. Despite the high cost of the drug doctors are positive.
“A very badly affected group of patients can get help and if a few of these individuals can get a better control over their asthma, their need for healthcare would decrease and their ability to work would increase. This could mean economic benefits for both healthcare and the society,” says Christer Jansson, professor and consultant at the lung and allergy clinic at Akademiska sjukhuset, Uppsala, Sweden.
Benralizumab is another drug targeting eosinophilic asthma, that is undergoing testing right now. Unlike mepolizumab it uses a different pathway; targeting the IL-5 receptor, causing eosinophil apoptosis (cell death). One potential advantage of benralizumab is that it can be given less often, every two months instead of every two weeks, which may lower the cost of the treatment.
Into the future
Hopefully these drugs are just the first of a new line of treatments available targeted at severe asthma. Research is needed to help patients with other types of severe asthma and better diagnostic tests are needed to help ensure that people can have a confirmed diagnosis quickly. This will mean appropriate treatments can be offered, freeing people to go to work, school, raise families and live unrestricted lives that are not overshadowed by asthma.
What are your thoughts on future treatments and diagnostics for asthma? Let me know @fraidifrida