The authors investigated the biomarker profile and PK/pharmacodynamics (PD) on ivacaftor-lumacaftor in 41 French patients utilizing potential screening tools for predicting PK/PD and patient outcomes utilizing CF biomarkers such as sweat chloride, β-adrenergic peak sweat, lung function (percentage predicted FEV1 [ppFEV1] and residual volume) and CFTR activity. Here, CFTR is linked to cystic fibrosis.