Nagy B, et al. - Given recent findings indicating the potential correlation of human epididymis protein 4 (HE4) levels to severity of cystic fibrosis (CF) lung disease, researchers investigated how HE4 levels alter in patients receiving CFTR modulating therapy. They performed a retrospective clinical study enrolling three independent CF patient cohorts (US-American: 29, Australian: 12, and Irish: 19 cases) carrying at least one Class III CFTR CF-causing mutation (p.Gly551Asp) and being treated with CFTR potentiator ivacaftor. Findings revealed an inverse correlation of plasma HE4 levels with lung function improvement in CF patients receiving ivacaftor. Overall, for routine clinical and laboratory follow-up of CFTR modulating therapy, this potential biomarker could be valuable.