CFTR and cystic fibrosis: Mucociliary clearance in bronchial and nasal epithelial cell cultures of CF patients improved even further when the arginase inhibitor CB1158 and Arg were supplemented in addition to treatment with Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) modulators and potentiators (i.e., lumacaftor/ivacaftor).