How do biologicals and other novel therapies effect clinically used biomarkers in severe asthma?

While there has been much interest in using biomarkers to select patients for particular targeted therapies, there has been much less attention paid to how these biomarkers change in patients once treatment begins. This is an area of great interest to practising clinicians, especially respiratory physicians and allergists who manage severe asthma. In this article, we review monoclonal antibodies and related targeted therapies, especially those that are currently available or in late stage clinical trials, focussing on the differential effects such agents have on biomarkers in widespread clinical practice such as eosinophils, FeNO and total IgE. Serial measurements of biomarkers can be useful in determining whether a particular targeted therapy is having its expected biological effect and invaluable in assessing the reasons for treatment failure should that occur.