In the presence of substantially improving lung function (17.5 [14.5–20.5]% of ppFEV1) in CF adults of cohort 1, there were significantly (p < 0.0001) reduced HE4 serum concentrations—regardless of its baseline value—at 3 months of treatment, this being the only follow-up time point of these patients (Figure 1A). Here, WFDC2 is linked to cystic fibrosis.