Indeed, the early trials of anti-IL-5 treatment did not select for patients with raised eosinophils, the cell type regulated by IL-5, and therefore yielded negative results.57 However, this study’s cohort resembled a subgroup with the greatest lung function response to timapiprant in an earlier trial: atopic with positive skin prick tests, partially uncontrolled asthma as defined by ACQ-6 score, raised blood eosinophil counts, and relatively young.29 No alternative biomarker or clinical parameter for identifying treatment response has been suggested in the literature. Here, IL5 is linked to asthma.