Characterising individual response to mepolizumab treatment

Background: Patients with severe eosinophilic asthma (SEA) often have heterogenous phenotypes with periods of asthma worsening, making it difficult to assess mepolizumab treatment response. Aims: To define patient level variables for mepolizumab treatment response. Methods: In this post-hoc analysis we examined mepolizumab response in patients with SEA (≥2 exacerbations in prior year) in the 32-week, randomised, placebo-controlled MENSA study and the following 52-week, open-label COSMOS study. Patients who completed both studies and received mepolizumab throughout were included (n=311). Results: In MENSA, 67% and 21% of patients had 0 or 1 exacerbations, respectively, and were considered responders; 12% (n=37) with ≥2 exacerbations were considered non-responders and assessed against four variables of clinical benefit. Of these non-responders, 89% (n=33) had evidence of response when other variables were assessed (Table). Of the 37 non-responders in MENSA, 38% (n=14) responded in COSMOS, having either 0 (n=3) or 1 (n=11) exacerbations. Conclusions: These data highlight the difficulty in defining individual response to mepolizumab treatment. Responder classification should ideally take into account several clinical measures of improvement beyond exacerbation reduction. The relative importance of each of these measures may differ between patients, therefore doctors should set realistic treatment goals with each patient. Funding: GSK[NCT01691521/NCT01842607]