Early Reduction of FeNO on Anti‐IL5 Biologics Is Associated With Clinical Remission of Severe Asthma

ABSTRACT Background In patients with severe asthma, treatment with anti‐interleukin‐5 (IL‐5) biologics can lead to a reduction in fractional exhaled nitric oxide (FeNO) in some patients. The clinical implications of varying FeNO responses to anti‐IL‐5 biologics remain unclear. This study aims to categorise patients based on their FeNO response to anti‐IL‐5 biologics and evaluate the association of these categories with clinical outcomes. Methods We used the Danish Severe Asthma Register (DSAR) to identify the early FeNO response profiles in patients receiving anti‐IL5 biologics. We defined FeNO responders as patients with elevated FeNO levels at baseline and a decrease corresponding to the minimal clinically important difference (MCID) at 4 months of follow‐up and FeNO non‐responders as those who did not experience a decrease. Results We identified 403 patients on anti‐IL5 treatment in DSAR, and 265 (66%) had elevated FeNO levels at baseline. After 4 months of treatment, 151 (57%) patients showed a significant decrease in FeNO levels, and 114 (43%) did not. FeNO responders were more likely to achieve clinical remission of asthma (34% vs. 19%, p = 0.01, OR 2.11, CI 1.04, 5.18, p = 0.03) than FeNO non‐responders after 12 months of treatment. The higher remission rates in FeNO responders mainly reflected a higher rate of normalisation of lung function. Conclusions FeNO levels were reduced after anti‐IL5 treatment in a significant proportion of patients treated with anti‐IL5, and this was associated with clinical remission. Early FeNO response to anti‐IL5 could potentially be used as a biomarker to guide management decisions with biologics towards remission of disease in severe asthma.