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

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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. 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. 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. 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.