Eosinophils – a type of white blood cell – are a biomarker for asthma: too many of them in the lungs can cause inflammation
Over 300 million people around the world live with asthma, each affected by their disease in a different way, but often taking a very similar treatment. But could ‘treatable traits’ help scientists uncover a more personalised approach to patient care?
As one of the world’s most common chronic diseases, chances are that most of us will know someone who lives with asthma.
Thanks to advances in treatments and care over the years, many are now able to live near-normal lives, but for some the ability to breathe normally remains a daily struggle.
In the words of one patient: “I have to schedule everything around my lungs.”
Of the 358 million people who live with asthma worldwide, it is estimated that around 30% have asthma that is uncontrolled despite taking their treatment. A further 10% have severe asthma, a different form of the disease in which people struggle to control their symptoms and continue to have asthma attacks, even when they take high doses of medicine.
For many patients with uncontrolled or severe asthma, even simple tasks can become difficult. Many live in fear of their next attack, of not being able to breathe.
Asthma is a chronic lung disease in which inflammation in the lungs makes the airways narrow. This can lead to symptoms such as coughing, wheezing, breathlessness and a tight chest. When these symptoms become worse, it can lead to an asthma attack.
Developments in therapy mean that many patients are able to manage their disease with daily treatment. But for some this isn’t enough.
Research has shown that not all asthma is the same. Asthma can have a number of underlying causes and different types of inflammation. For some people, their inflammation may be triggered by environmental allergens, such as dust mites, pollen and moulds.
For others, their own body may be turning against them.
All of us have eosinophils in our body. They are a type of white blood cell, produced in our bone marrow, and are an important part of our immune system. Found primarily in the gut, they fight parasites and, together with other cells, they form a complex network that helps protect us and keep us healthy.
But in some people, eosinophils can cause trouble. In around half of people with severe asthma, a raised level of eosinophils in their bloodstream causes inflammation and swelling in the airways that deliver vital oxygen to the lungs, making it difficult to breathe and increasing the risk of an asthma attack.
Eosinophils are a biomarker – this is a molecule, gene or characteristic by which a particular disease can be recognised. By understanding how biomarkers work – and the part they play in the body – scientists can identify ways of developing treatment approaches that are tailored to the specific needs of individual patients.
“Understanding the way that biology works differently in different people is at the heart of personalised treatment: it means that treatment can be targeted very specifically – helping us get the right treatment to the right patient,” Steve Yancey, Respiratory Medicines Development Leader, GSK
This recognition has led scientists to develop biologic medicines – produced by living cells, rather than a chemical process – which are thought to treat severe asthma by normalising levels of these white blood cells through targeting a particular protein. A simple blood test can help to identify patients who may be most likely to benefit from this precise approach.
As the understanding of asthma increases, scientists are looking at whether eosinophils can be used as a biomarker more broadly in asthma. They are also exploring if there are further biomarkers or identifiable characteristics known as ‘treatable traits’ that can help doctors adopt a more personalised approach to determining how best to help their patients.
Alongside eosinophil levels, there are many other features of asthma which seem to have an impact on how well a patient responds to different treatment approaches.
By looking at specific groups of asthma patients included in clinical trials, scientists are able to classify these ‘treatable traits’ giving them a better understanding of the disease features which may need to be addressed to improve outcomes for patients.
For example, some patients have limited airflow in their lungs meaning they may require medicines designed to open their airways, others have bacteria present and others cough. A patient’s weight may be a factor, as could be the level of resistance in their lungs.
All of these traits may be options for doctors to address to help minimise the impact of asthma on each individual patient. Instead of a ‘one-size fits all’ approach, it’s becoming more and more clear that different strategies are needed to establish good asthma control for as many patients as possible. And treatable traits may help doctors establish the most appropriate medicine for their patients, reducing the burden of their disease.
For as long as patients are struggling with asthma, there is more for us to do.
Our understanding of this common but complex disease is evolving all the time. As we get better at unlocking its secrets, our hope is that treatable traits will help drive our medicines development, enabling a more personal approach and representing a big step forward for patients.
