Furthermore, in response to in vitro rescue of CFTR function by LUM/IVA, HE4 expression was lowered in cystic fibrosis bronchial epithelial cell (CFBE) 41o- cells expressing p.Phe508del-CFTR [18], while delta HE4 independently indicated the likelihood of being a responder with ≥5% delta ppFEV1 at 6 months in pwCF undergoing LUM/IVA treatment [17]. This evidence concerns the gene WFDC2 and cystic fibrosis.